Targeting LRG1 boosts immunotherapy

Vascular normalization therapy has the potential to facilitate drug delivery and lymphocyte infiltration in tumors. Yet, optimal targets and dosage regimens remain elusive. In this issue of Med, O’Connor et al. show that inhibition of LRG1 stabilizes the tumor-associated vasculature to enhance tumor response to both cytotoxic and immune therapies. Vascular normalization therapy has the potential to facilitate drug delivery and lymphocyte infiltration in tumors. Yet, optimal targets and dosage regimens remain elusive. In this issue of Med, O’Connor et al. show that inhibition of LRG1 stabilizes the tumor-associated vasculature to enhance tumor response to both cytotoxic and immune therapies. Main textAntiangiogenic therapy, which is aimed to disrupt tumor-associated blood vessels, has largely failed to improve overall survival of cancer patients owing to tumor adaptations that may fuel aggressive regrowth. Lessons learned from preclinical models and clinical experience have put forward an alternative approach, where the treatment is aimed to normalize the unstable and dysfunctional tumor-associated vasculature and improve—rather than impair—vascular functionality, so as to enhance drug delivery to the tumor.1Jain R.K. Normalization of tumor vasculature: an emerging concept in antiangiogenic therapy.Science. 2005; 307: 58-62Crossref PubMed Scopus (4275) Google Scholar This strategy may also facilitate T cell trafficking and increase tumor response to immunotherapy, including immune checkpoint blockade (ICB), as shown in both preclinical models2Allen E. Jabouille A. Rivera L.B. Lodewijckx I. Missiaen R. Steri V. Feyen K. Tawney J. Hanahan D. Michael I.P. et al.Combined antiangiogenic and anti–PD-L1 therapy stimulates tumor immunity through HEV formation.Science Translational Medicine. 2017; 9: eaak9679Crossref PubMed Scopus (400) Google Scholar, 3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 4Schmittnaegel M. Rigamonti N. Kadioglu E. Cassará A. Wyser Rmili C. Kiialainen A. Kienast Y. Mueller H.-J. Ooi C.-H. Laoui D. et al.Dual angiopoietin-2 and VEGFA inhibition elicits antitumor immunity that is enhanced by PD-1 checkpoint blockade.Science Translational Medicine. 2017; 9: eaak9670Crossref PubMed Scopus (326) Google Scholar and clinical trials.5Finn R.S. Qin S. Ikeda M. Galle P.R. Ducreux M. Kim T.-Y. Kudo M. Breder V. Merle P. Kaseb A.O. et al.IMbrave150 InvestigatorsAtezolizumab plus Bevacizumab in Unresectable Hepatocellular Carcinoma.N. Engl. J. Med. 2020; 382: 1894-1905Crossref PubMed Scopus (1909) Google Scholar Challenges to broad clinical implementation, however, are the incomplete understanding of the cellular and molecular mechanisms that govern tumor-associated vessel dysfunction and the identification of optimal drug regimens that may initiate and maintain vascular normalization across diverse tissue sites. Writing in this issue of Med, O’Connor et al. describe a new promising target, leucine rich alpha-2-glycoprotein-1 (LRG1), which is induced in human tumors and whose inhibition promotes vascular stability, drug delivery, and immunotherapeutic efficacy.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google ScholarLRG1 is a secreted glycoprotein that binds endoglin—a critical component of the transforming growth factor-β (TGFβ) receptor complex—to switch downstream signaling pathways from angiostatic to angiogenic.7Wang X. Abraham S. McKenzie J.A.G. Jeffs N. Swire M. Tripathi V.B. Luhmann U.F.O. Lange C.A.K. Zhai Z. Arthur H.M. et al.LRG1 promotes angiogenesis by modulating endothelial TGF-β signalling.Nature. 2013; 499: 306-311Crossref PubMed Scopus (288) Google Scholar While LRG1 is dispensable for vascular development, its expression induces disorganized and dysfunctional blood vessel growth, which contributes to vascular pathology in mouse models of macular degeneration and ocular hypoxia.7Wang X. Abraham S. McKenzie J.A.G. Jeffs N. Swire M. Tripathi V.B. Luhmann U.F.O. Lange C.A.K. Zhai Z. Arthur H.M. et al.LRG1 promotes angiogenesis by modulating endothelial TGF-β signalling.Nature. 2013; 499: 306-311Crossref PubMed Scopus (288) Google Scholar Recently, LRG1 was also identified as an inflammatory feature of the premetastatic lung microvasculature, whose expression is induced in lung endothelial cells during primary tumor development. High expression of LRG1 by either endothelial or cancer cells heightened serum levels of LRG1, destabilized blood vessels systemically, and created a permissive niche for cancer cell seeding and outgrowth.8Singhal M. Gengenbacher N. Abdul Pari A.A. Kamiyama M. Hai L. Kuhn B.J. Kallenberg D.M. Kulkarni S.R. Camilli C. Preuß S.F. et al.Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis.Sci. Transl. Med. 2021; 13: eabe6805Crossref PubMed Scopus (12) Google ScholarIn a new study, O’Connor et al. tested the hypothesis that therapeutic inhibition of LRG1 is a vascular-normalizing strategy that synergizes with both cytotoxic and immune treatments.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar They found that LRG1 is induced in human carcinomas of the lung, prostate, and breast, relative to normal tissue, and is elevated in the serum of patients with pancreas and squamous cell lung carcinoma compared to healthy subjects. In preclinical mouse models, both genetic and antibody-based inhibition of LRG1 increased vascular patency, mural cell coverage, and blood vessel perfusion and reduced intratumoral hypoxia, all suggesting a more functional tumor-associated vasculature (Figure 1). Interestingly, LRG1 inhibition alone was sufficient to inhibit the incidence and growth of tumors and to extend mouse survival in various preclinical tumor models, raising the question of whether normalizing the tumor-associated vasculature through LRG1 inhibition could also synergize with anticancer therapies.To explore the therapeutic potential of combination therapy, O’Connor et al. combined the LRG1-targeting antibody with cisplatin, adoptive T cell therapy, or ICB in a mouse melanoma model. In all cases, combination therapy improved tumor control and was associated with more efficient therapy delivery to the tumor parenchyma. Co-delivery of cisplatin with LRG1 antibodies increased the prevalence of DNA double-strand breaks in the cancer cells, while combination with adoptive T cell therapy or ICB improved T cell infiltration, together supporting the hypothesis that improved vascular function was a key mechanism of action and determinant for the efficacy of the combined treatments.These results are consistent with earlier studies that reported therapeutic synergy when combining vascular-targeting agents with ICB.2Allen E. Jabouille A. Rivera L.B. Lodewijckx I. Missiaen R. Steri V. Feyen K. Tawney J. Hanahan D. Michael I.P. et al.Combined antiangiogenic and anti–PD-L1 therapy stimulates tumor immunity through HEV formation.Science Translational Medicine. 2017; 9: eaak9679Crossref PubMed Scopus (400) Google Scholar, 3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 4Schmittnaegel M. Rigamonti N. Kadioglu E. Cassará A. Wyser Rmili C. Kiialainen A. Kienast Y. Mueller H.-J. Ooi C.-H. Laoui D. et al.Dual angiopoietin-2 and VEGFA inhibition elicits antitumor immunity that is enhanced by PD-1 checkpoint blockade.Science Translational Medicine. 2017; 9: eaak9670Crossref PubMed Scopus (326) Google Scholar However, the mechanisms of vascular normalization vary with the molecular target or therapeutic agent, illustrating multiple pathways for vascular remodeling that may improve immune surveillance of cancer. For example, antiangiogenic treatment with VEGFA pathway inhibitors and ICB may induce intratumoral blood vessels to acquire a high endothelial venule (HEV)-like phenotype that increases T cell infiltration and ICB efficacy.2Allen E. Jabouille A. Rivera L.B. Lodewijckx I. Missiaen R. Steri V. Feyen K. Tawney J. Hanahan D. Michael I.P. et al.Combined antiangiogenic and anti–PD-L1 therapy stimulates tumor immunity through HEV formation.Science Translational Medicine. 2017; 9: eaak9679Crossref PubMed Scopus (400) Google Scholar,3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar However, there was no evidence for HEV-like vessels in tumors treated with LRG1 and PD-1 antibodies.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar Instead, transcriptional analyses indicated increased expression of adhesion molecules that might provide a more permissive scaffold for the trans-endothelial migration of effector T cells. These studies raise the possibility that targeting either specific angiocrine signals or immune checkpoints (e.g., PD-L1 versus PD-1) may drive distinct, endothelial-dependent therapeutic responses, perhaps impacted by underlying organ-specific endothelial heterogeneity.9Nolan D.J. Ginsberg M. Israely E. Palikuqi B. Poulos M.G. James D. Ding B.-S. Schachterle W. Liu Y. Rosenwaks Z. et al.Molecular signatures of tissue-specific microvascular endothelial cell heterogeneity in organ maintenance and regeneration.Dev. Cell. 2013; 26: 204-219Abstract Full Text Full Text PDF PubMed Scopus (413) Google Scholar While LRG1 appears to be upregulated across visceral organ sites in tumor-bearing mice,8Singhal M. Gengenbacher N. Abdul Pari A.A. Kamiyama M. Hai L. Kuhn B.J. Kallenberg D.M. Kulkarni S.R. Camilli C. Preuß S.F. et al.Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis.Sci. Transl. Med. 2021; 13: eabe6805Crossref PubMed Scopus (12) Google Scholar its impact on vascular function in distinct organ niches remains to be determined. Importantly, recent evidence indicates that an ICB and antiangiogenic combination regimen, efficacious in multiple solid tumor models, exacerbated disease progression when applied to mouse models of non-small cell lung cancer,10Martinez-Usatorre A. Kadioglu E. Boivin G. Cianciaruso C. Guichard A. Torchia B. Zangger N. Nassiri S. Keklikoglou I. Schmittnaegel M. et al.Overcoming microenvironmental resistance to PD-1 blockade in genetically engineered lung cancer models.Sci. Transl. Med. 2021; 13: eabd1616Crossref PubMed Scopus (16) Google Scholar further highlighting the need to consider tissue-specific endothelial and immune biology.Importantly, O’Connor et al.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar provide proof of principle, across multiple preclinical tumor models, that LRG1 inhibition improves both cytotoxic and immune therapies, which may ultimately guide clinical care. The interesting observation that LRG1 inhibition also prevents metastasis in the perioperative and postsurgical setting6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar,8Singhal M. Gengenbacher N. Abdul Pari A.A. Kamiyama M. Hai L. Kuhn B.J. Kallenberg D.M. Kulkarni S.R. Camilli C. Preuß S.F. et al.Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis.Sci. Transl. Med. 2021; 13: eabe6805Crossref PubMed Scopus (12) Google Scholar suggests improved control of occult metastases; the efficacy of these combinations in the setting of spontaneously disseminated disease thus deserves further investigation. Together, these preclinical studies support the concept that vascular-targeting agents may both stabilize the vasculature to prevent cancer-cell extravasation and simultaneously sensitize metastatic lesions for T cell infiltration and response to ICB.3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar The intertwined regulation of both metastatic dissemination and immune cell trafficking in various tumor beds and premetastatic niches may provide future strategies for therapeutic intervention. Main textAntiangiogenic therapy, which is aimed to disrupt tumor-associated blood vessels, has largely failed to improve overall survival of cancer patients owing to tumor adaptations that may fuel aggressive regrowth. Lessons learned from preclinical models and clinical experience have put forward an alternative approach, where the treatment is aimed to normalize the unstable and dysfunctional tumor-associated vasculature and improve—rather than impair—vascular functionality, so as to enhance drug delivery to the tumor.1Jain R.K. Normalization of tumor vasculature: an emerging concept in antiangiogenic therapy.Science. 2005; 307: 58-62Crossref PubMed Scopus (4275) Google Scholar This strategy may also facilitate T cell trafficking and increase tumor response to immunotherapy, including immune checkpoint blockade (ICB), as shown in both preclinical models2Allen E. Jabouille A. Rivera L.B. Lodewijckx I. Missiaen R. Steri V. Feyen K. Tawney J. Hanahan D. Michael I.P. et al.Combined antiangiogenic and anti–PD-L1 therapy stimulates tumor immunity through HEV formation.Science Translational Medicine. 2017; 9: eaak9679Crossref PubMed Scopus (400) Google Scholar, 3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 4Schmittnaegel M. Rigamonti N. Kadioglu E. Cassará A. Wyser Rmili C. Kiialainen A. Kienast Y. Mueller H.-J. Ooi C.-H. Laoui D. et al.Dual angiopoietin-2 and VEGFA inhibition elicits antitumor immunity that is enhanced by PD-1 checkpoint blockade.Science Translational Medicine. 2017; 9: eaak9670Crossref PubMed Scopus (326) Google Scholar and clinical trials.5Finn R.S. Qin S. Ikeda M. Galle P.R. Ducreux M. Kim T.-Y. Kudo M. Breder V. Merle P. Kaseb A.O. et al.IMbrave150 InvestigatorsAtezolizumab plus Bevacizumab in Unresectable Hepatocellular Carcinoma.N. Engl. J. Med. 2020; 382: 1894-1905Crossref PubMed Scopus (1909) Google Scholar Challenges to broad clinical implementation, however, are the incomplete understanding of the cellular and molecular mechanisms that govern tumor-associated vessel dysfunction and the identification of optimal drug regimens that may initiate and maintain vascular normalization across diverse tissue sites. Writing in this issue of Med, O’Connor et al. describe a new promising target, leucine rich alpha-2-glycoprotein-1 (LRG1), which is induced in human tumors and whose inhibition promotes vascular stability, drug delivery, and immunotherapeutic efficacy.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google ScholarLRG1 is a secreted glycoprotein that binds endoglin—a critical component of the transforming growth factor-β (TGFβ) receptor complex—to switch downstream signaling pathways from angiostatic to angiogenic.7Wang X. Abraham S. McKenzie J.A.G. Jeffs N. Swire M. Tripathi V.B. Luhmann U.F.O. Lange C.A.K. Zhai Z. Arthur H.M. et al.LRG1 promotes angiogenesis by modulating endothelial TGF-β signalling.Nature. 2013; 499: 306-311Crossref PubMed Scopus (288) Google Scholar While LRG1 is dispensable for vascular development, its expression induces disorganized and dysfunctional blood vessel growth, which contributes to vascular pathology in mouse models of macular degeneration and ocular hypoxia.7Wang X. Abraham S. McKenzie J.A.G. Jeffs N. Swire M. Tripathi V.B. Luhmann U.F.O. Lange C.A.K. Zhai Z. Arthur H.M. et al.LRG1 promotes angiogenesis by modulating endothelial TGF-β signalling.Nature. 2013; 499: 306-311Crossref PubMed Scopus (288) Google Scholar Recently, LRG1 was also identified as an inflammatory feature of the premetastatic lung microvasculature, whose expression is induced in lung endothelial cells during primary tumor development. High expression of LRG1 by either endothelial or cancer cells heightened serum levels of LRG1, destabilized blood vessels systemically, and created a permissive niche for cancer cell seeding and outgrowth.8Singhal M. Gengenbacher N. Abdul Pari A.A. Kamiyama M. Hai L. Kuhn B.J. Kallenberg D.M. Kulkarni S.R. Camilli C. Preuß S.F. et al.Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis.Sci. Transl. Med. 2021; 13: eabe6805Crossref PubMed Scopus (12) Google ScholarIn a new study, O’Connor et al. tested the hypothesis that therapeutic inhibition of LRG1 is a vascular-normalizing strategy that synergizes with both cytotoxic and immune treatments.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar They found that LRG1 is induced in human carcinomas of the lung, prostate, and breast, relative to normal tissue, and is elevated in the serum of patients with pancreas and squamous cell lung carcinoma compared to healthy subjects. In preclinical mouse models, both genetic and antibody-based inhibition of LRG1 increased vascular patency, mural cell coverage, and blood vessel perfusion and reduced intratumoral hypoxia, all suggesting a more functional tumor-associated vasculature (Figure 1). Interestingly, LRG1 inhibition alone was sufficient to inhibit the incidence and growth of tumors and to extend mouse survival in various preclinical tumor models, raising the question of whether normalizing the tumor-associated vasculature through LRG1 inhibition could also synergize with anticancer therapies.To explore the therapeutic potential of combination therapy, O’Connor et al. combined the LRG1-targeting antibody with cisplatin, adoptive T cell therapy, or ICB in a mouse melanoma model. In all cases, combination therapy improved tumor control and was associated with more efficient therapy delivery to the tumor parenchyma. Co-delivery of cisplatin with LRG1 antibodies increased the prevalence of DNA double-strand breaks in the cancer cells, while combination with adoptive T cell therapy or ICB improved T cell infiltration, together supporting the hypothesis that improved vascular function was a key mechanism of action and determinant for the efficacy of the combined treatments.These results are consistent with earlier studies that reported therapeutic synergy when combining vascular-targeting agents with ICB.2Allen E. Jabouille A. Rivera L.B. Lodewijckx I. Missiaen R. Steri V. Feyen K. Tawney J. Hanahan D. Michael I.P. et al.Combined antiangiogenic and anti–PD-L1 therapy stimulates tumor immunity through HEV formation.Science Translational Medicine. 2017; 9: eaak9679Crossref PubMed Scopus (400) Google Scholar, 3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 4Schmittnaegel M. Rigamonti N. Kadioglu E. Cassará A. Wyser Rmili C. Kiialainen A. Kienast Y. Mueller H.-J. Ooi C.-H. Laoui D. et al.Dual angiopoietin-2 and VEGFA inhibition elicits antitumor immunity that is enhanced by PD-1 checkpoint blockade.Science Translational Medicine. 2017; 9: eaak9670Crossref PubMed Scopus (326) Google Scholar However, the mechanisms of vascular normalization vary with the molecular target or therapeutic agent, illustrating multiple pathways for vascular remodeling that may improve immune surveillance of cancer. For example, antiangiogenic treatment with VEGFA pathway inhibitors and ICB may induce intratumoral blood vessels to acquire a high endothelial venule (HEV)-like phenotype that increases T cell infiltration and ICB efficacy.2Allen E. Jabouille A. Rivera L.B. Lodewijckx I. Missiaen R. Steri V. Feyen K. Tawney J. Hanahan D. Michael I.P. et al.Combined antiangiogenic and anti–PD-L1 therapy stimulates tumor immunity through HEV formation.Science Translational Medicine. 2017; 9: eaak9679Crossref PubMed Scopus (400) Google Scholar,3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar However, there was no evidence for HEV-like vessels in tumors treated with LRG1 and PD-1 antibodies.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar Instead, transcriptional analyses indicated increased expression of adhesion molecules that might provide a more permissive scaffold for the trans-endothelial migration of effector T cells. These studies raise the possibility that targeting either specific angiocrine signals or immune checkpoints (e.g., PD-L1 versus PD-1) may drive distinct, endothelial-dependent therapeutic responses, perhaps impacted by underlying organ-specific endothelial heterogeneity.9Nolan D.J. Ginsberg M. Israely E. Palikuqi B. Poulos M.G. James D. Ding B.-S. Schachterle W. Liu Y. Rosenwaks Z. et al.Molecular signatures of tissue-specific microvascular endothelial cell heterogeneity in organ maintenance and regeneration.Dev. Cell. 2013; 26: 204-219Abstract Full Text Full Text PDF PubMed Scopus (413) Google Scholar While LRG1 appears to be upregulated across visceral organ sites in tumor-bearing mice,8Singhal M. Gengenbacher N. Abdul Pari A.A. Kamiyama M. Hai L. Kuhn B.J. Kallenberg D.M. Kulkarni S.R. Camilli C. Preuß S.F. et al.Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis.Sci. Transl. Med. 2021; 13: eabe6805Crossref PubMed Scopus (12) Google Scholar its impact on vascular function in distinct organ niches remains to be determined. Importantly, recent evidence indicates that an ICB and antiangiogenic combination regimen, efficacious in multiple solid tumor models, exacerbated disease progression when applied to mouse models of non-small cell lung cancer,10Martinez-Usatorre A. Kadioglu E. Boivin G. Cianciaruso C. Guichard A. Torchia B. Zangger N. Nassiri S. Keklikoglou I. Schmittnaegel M. et al.Overcoming microenvironmental resistance to PD-1 blockade in genetically engineered lung cancer models.Sci. Transl. Med. 2021; 13: eabd1616Crossref PubMed Scopus (16) Google Scholar further highlighting the need to consider tissue-specific endothelial and immune biology.Importantly, O’Connor et al.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar provide proof of principle, across multiple preclinical tumor models, that LRG1 inhibition improves both cytotoxic and immune therapies, which may ultimately guide clinical care. The interesting observation that LRG1 inhibition also prevents metastasis in the perioperative and postsurgical setting6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar,8Singhal M. Gengenbacher N. Abdul Pari A.A. Kamiyama M. Hai L. Kuhn B.J. Kallenberg D.M. Kulkarni S.R. Camilli C. Preuß S.F. et al.Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis.Sci. Transl. Med. 2021; 13: eabe6805Crossref PubMed Scopus (12) Google Scholar suggests improved control of occult metastases; the efficacy of these combinations in the setting of spontaneously disseminated disease thus deserves further investigation. Together, these preclinical studies support the concept that vascular-targeting agents may both stabilize the vasculature to prevent cancer-cell extravasation and simultaneously sensitize metastatic lesions for T cell infiltration and response to ICB.3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar The intertwined regulation of both metastatic dissemination and immune cell trafficking in various tumor beds and premetastatic niches may provide future strategies for therapeutic intervention. Antiangiogenic therapy, which is aimed to disrupt tumor-associated blood vessels, has largely failed to improve overall survival of cancer patients owing to tumor adaptations that may fuel aggressive regrowth. Lessons learned from preclinical models and clinical experience have put forward an alternative approach, where the treatment is aimed to normalize the unstable and dysfunctional tumor-associated vasculature and improve—rather than impair—vascular functionality, so as to enhance drug delivery to the tumor.1Jain R.K. Normalization of tumor vasculature: an emerging concept in antiangiogenic therapy.Science. 2005; 307: 58-62Crossref PubMed Scopus (4275) Google Scholar This strategy may also facilitate T cell trafficking and increase tumor response to immunotherapy, including immune checkpoint blockade (ICB), as shown in both preclinical models2Allen E. Jabouille A. Rivera L.B. Lodewijckx I. Missiaen R. Steri V. Feyen K. Tawney J. Hanahan D. Michael I.P. et al.Combined antiangiogenic and anti–PD-L1 therapy stimulates tumor immunity through HEV formation.Science Translational Medicine. 2017; 9: eaak9679Crossref PubMed Scopus (400) Google Scholar, 3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 4Schmittnaegel M. Rigamonti N. Kadioglu E. Cassará A. Wyser Rmili C. Kiialainen A. Kienast Y. Mueller H.-J. Ooi C.-H. Laoui D. et al.Dual angiopoietin-2 and VEGFA inhibition elicits antitumor immunity that is enhanced by PD-1 checkpoint blockade.Science Translational Medicine. 2017; 9: eaak9670Crossref PubMed Scopus (326) Google Scholar and clinical trials.5Finn R.S. Qin S. Ikeda M. Galle P.R. Ducreux M. Kim T.-Y. Kudo M. Breder V. Merle P. Kaseb A.O. et al.IMbrave150 InvestigatorsAtezolizumab plus Bevacizumab in Unresectable Hepatocellular Carcinoma.N. Engl. J. Med. 2020; 382: 1894-1905Crossref PubMed Scopus (1909) Google Scholar Challenges to broad clinical implementation, however, are the incomplete understanding of the cellular and molecular mechanisms that govern tumor-associated vessel dysfunction and the identification of optimal drug regimens that may initiate and maintain vascular normalization across diverse tissue sites. Writing in this issue of Med, O’Connor et al. describe a new promising target, leucine rich alpha-2-glycoprotein-1 (LRG1), which is induced in human tumors and whose inhibition promotes vascular stability, drug delivery, and immunotherapeutic efficacy.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar LRG1 is a secreted glycoprotein that binds endoglin—a critical component of the transforming growth factor-β (TGFβ) receptor complex—to switch downstream signaling pathways from angiostatic to angiogenic.7Wang X. Abraham S. McKenzie J.A.G. Jeffs N. Swire M. Tripathi V.B. Luhmann U.F.O. Lange C.A.K. Zhai Z. Arthur H.M. et al.LRG1 promotes angiogenesis by modulating endothelial TGF-β signalling.Nature. 2013; 499: 306-311Crossref PubMed Scopus (288) Google Scholar While LRG1 is dispensable for vascular development, its expression induces disorganized and dysfunctional blood vessel growth, which contributes to vascular pathology in mouse models of macular degeneration and ocular hypoxia.7Wang X. Abraham S. McKenzie J.A.G. Jeffs N. Swire M. Tripathi V.B. Luhmann U.F.O. Lange C.A.K. Zhai Z. Arthur H.M. et al.LRG1 promotes angiogenesis by modulating endothelial TGF-β signalling.Nature. 2013; 499: 306-311Crossref PubMed Scopus (288) Google Scholar Recently, LRG1 was also identified as an inflammatory feature of the premetastatic lung microvasculature, whose expression is induced in lung endothelial cells during primary tumor development. High expression of LRG1 by either endothelial or cancer cells heightened serum levels of LRG1, destabilized blood vessels systemically, and created a permissive niche for cancer cell seeding and outgrowth.8Singhal M. Gengenbacher N. Abdul Pari A.A. Kamiyama M. Hai L. Kuhn B.J. Kallenberg D.M. Kulkarni S.R. Camilli C. Preuß S.F. et al.Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis.Sci. Transl. Med. 2021; 13: eabe6805Crossref PubMed Scopus (12) Google Scholar In a new study, O’Connor et al. tested the hypothesis that therapeutic inhibition of LRG1 is a vascular-normalizing strategy that synergizes with both cytotoxic and immune treatments.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar They found that LRG1 is induced in human carcinomas of the lung, prostate, and breast, relative to normal tissue, and is elevated in the serum of patients with pancreas and squamous cell lung carcinoma compared to healthy subjects. In preclinical mouse models, both genetic and antibody-based inhibition of LRG1 increased vascular patency, mural cell coverage, and blood vessel perfusion and reduced intratumoral hypoxia, all suggesting a more functional tumor-associated vasculature (Figure 1). Interestingly, LRG1 inhibition alone was sufficient to inhibit the incidence and growth of tumors and to extend mouse survival in various preclinical tumor models, raising the question of whether normalizing the tumor-associated vasculature through LRG1 inhibition could also synergize with anticancer therapies. To explore the therapeutic potential of combination therapy, O’Connor et al. combined the LRG1-targeting antibody with cisplatin, adoptive T cell therapy, or ICB in a mouse melanoma model. In all cases, combination therapy improved tumor control and was associated with more efficient therapy delivery to the tumor parenchyma. Co-delivery of cisplatin with LRG1 antibodies increased the prevalence of DNA double-strand breaks in the cancer cells, while combination with adoptive T cell therapy or ICB improved T cell infiltration, together supporting the hypothesis that improved vascular function was a key mechanism of action and determinant for the efficacy of the combined treatments. These results are consistent with earlier studies that reported therapeutic synergy when combining vascular-targeting agents with ICB.2Allen E. Jabouille A. Rivera L.B. Lodewijckx I. Missiaen R. Steri V. Feyen K. Tawney J. Hanahan D. Michael I.P. et al.Combined antiangiogenic and anti–PD-L1 therapy stimulates tumor immunity through HEV formation.Science Translational Medicine. 2017; 9: eaak9679Crossref PubMed Scopus (400) Google Scholar, 3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 4Schmittnaegel M. Rigamonti N. Kadioglu E. Cassará A. Wyser Rmili C. Kiialainen A. Kienast Y. Mueller H.-J. Ooi C.-H. Laoui D. et al.Dual angiopoietin-2 and VEGFA inhibition elicits antitumor immunity that is enhanced by PD-1 checkpoint blockade.Science Translational Medicine. 2017; 9: eaak9670Crossref PubMed Scopus (326) Google Scholar However, the mechanisms of vascular normalization vary with the molecular target or therapeutic agent, illustrating multiple pathways for vascular remodeling that may improve immune surveillance of cancer. For example, antiangiogenic treatment with VEGFA pathway inhibitors and ICB may induce intratumoral blood vessels to acquire a high endothelial venule (HEV)-like phenotype that increases T cell infiltration and ICB efficacy.2Allen E. Jabouille A. Rivera L.B. Lodewijckx I. Missiaen R. Steri V. Feyen K. Tawney J. Hanahan D. Michael I.P. et al.Combined antiangiogenic and anti–PD-L1 therapy stimulates tumor immunity through HEV formation.Science Translational Medicine. 2017; 9: eaak9679Crossref PubMed Scopus (400) Google Scholar,3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar However, there was no evidence for HEV-like vessels in tumors treated with LRG1 and PD-1 antibodies.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar Instead, transcriptional analyses indicated increased expression of adhesion molecules that might provide a more permissive scaffold for the trans-endothelial migration of effector T cells. These studies raise the possibility that targeting either specific angiocrine signals or immune checkpoints (e.g., PD-L1 versus PD-1) may drive distinct, endothelial-dependent therapeutic responses, perhaps impacted by underlying organ-specific endothelial heterogeneity.9Nolan D.J. Ginsberg M. Israely E. Palikuqi B. Poulos M.G. James D. Ding B.-S. Schachterle W. Liu Y. Rosenwaks Z. et al.Molecular signatures of tissue-specific microvascular endothelial cell heterogeneity in organ maintenance and regeneration.Dev. Cell. 2013; 26: 204-219Abstract Full Text Full Text PDF PubMed Scopus (413) Google Scholar While LRG1 appears to be upregulated across visceral organ sites in tumor-bearing mice,8Singhal M. Gengenbacher N. Abdul Pari A.A. Kamiyama M. Hai L. Kuhn B.J. Kallenberg D.M. Kulkarni S.R. Camilli C. Preuß S.F. et al.Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis.Sci. Transl. Med. 2021; 13: eabe6805Crossref PubMed Scopus (12) Google Scholar its impact on vascular function in distinct organ niches remains to be determined. Importantly, recent evidence indicates that an ICB and antiangiogenic combination regimen, efficacious in multiple solid tumor models, exacerbated disease progression when applied to mouse models of non-small cell lung cancer,10Martinez-Usatorre A. Kadioglu E. Boivin G. Cianciaruso C. Guichard A. Torchia B. Zangger N. Nassiri S. Keklikoglou I. Schmittnaegel M. et al.Overcoming microenvironmental resistance to PD-1 blockade in genetically engineered lung cancer models.Sci. Transl. Med. 2021; 13: eabd1616Crossref PubMed Scopus (16) Google Scholar further highlighting the need to consider tissue-specific endothelial and immune biology. Importantly, O’Connor et al.6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar provide proof of principle, across multiple preclinical tumor models, that LRG1 inhibition improves both cytotoxic and immune therapies, which may ultimately guide clinical care. The interesting observation that LRG1 inhibition also prevents metastasis in the perioperative and postsurgical setting6O’Connor M. Kallenberg D.M. Camilli C. Pilotti C. Drtisoula A. Jackstadt R. Bowers C. Watson A. Alatsatianos M. Ohme J. et al.LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency.Med. 2021; 2: 1231-1252Abstract Full Text Full Text PDF Scopus (6) Google Scholar,8Singhal M. Gengenbacher N. Abdul Pari A.A. Kamiyama M. Hai L. Kuhn B.J. Kallenberg D.M. Kulkarni S.R. Camilli C. Preuß S.F. et al.Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis.Sci. Transl. Med. 2021; 13: eabe6805Crossref PubMed Scopus (12) Google Scholar suggests improved control of occult metastases; the efficacy of these combinations in the setting of spontaneously disseminated disease thus deserves further investigation. Together, these preclinical studies support the concept that vascular-targeting agents may both stabilize the vasculature to prevent cancer-cell extravasation and simultaneously sensitize metastatic lesions for T cell infiltration and response to ICB.3He B. Johansson-Percival A. Backhouse J. Li J. Lee G.Y.F. Hamzah J. Ganss R. Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy.Cell Rep. 2020; 30: 714-724.e5Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar The intertwined regulation of both metastatic dissemination and immune cell trafficking in various tumor beds and premetastatic niches may provide future strategies for therapeutic intervention. The authors declare no competing financial interests. M.D.P. received sponsored research grants from EVIR Therapeutics, Hoffman La-Roche, Deciphera Pharmaceuticals, and MedImmune; reports honoraria from Merck and Sanofi/Regeneron Pharmaceuticals; and serves on the Scientific Advisory Boards of EVIR Therapeutics, Deciphera Pharmaceuticals, Montis Biosciences, Light Chain Bioscience/Novimmune, Macomics, and Genenta. LRG1 destabilizes tumor vessels and restricts immunotherapeutic potencyO’Connor et al.MedNovember 3, 2021In BriefAbnormal tumor vessel function is pro-oncogenic and restricts the delivery of therapeutics. O’Connor et al. demonstrate that induced expression of LRG1 in cancer contributes to tumor vascular dysfunction and its inhibition improves cytotoxic and immunotherapeutic efficacy. Full-Text PDF