Abstract 1979: JAK2/STAT3 and TrkA pathways are frequently co-activated in triple-negative and HER2-enriched breast cancers and the co-activation correlates with an increased potential of metastasis

Abstract Breast cancer is the leading cause of cancer-related deaths in American women. Despite the current standard-of-care, which implements tumor resection, radiotherapy, and chemotherapy, triple-negative and HER2-positive breast cancer patients often relapse and present with recurrent disease, for which there is no cure. Thus, there is an urgent need to identify new molecular targets to improve patient response to anti-cancer therapies. The JAK2-STAT3 and TrkA receptor tyrosine kinase signaling pathways have been separately implicated in metastatic breast cancers, but information about their crosstalk remains limited. Activated Janus kinase 2 (JAK2) receptor tyrosine kinase phosphorylates signal transducer and activator of transcription 3 (STAT3) transcription factor, inducing STAT3 nuclear translocation and transcriptional activity. Abnormal activation of STAT3-mediated transcription has been identified as a pro-tumorigenic event in breast cancers and promotes progression through induction of breast cancer stem cells, invasion, and angiogenesis. Tropomyosin receptor kinase A (TrkA) frequently forms oncogenic fusion proteins and its overexpression has been shown to drive malignant transformation of breast cancer cells. JAK2 inhibitors, while approved for treatment of myeloproliferative neoplasms, are currently in clinical trials for triple-negative breast cancers. Currently, there are two FDA-approved TrkA inhibitors for treatment of NTRK1 fusion-positive solid tumors, one of which is considered a tumor-agnostic inhibitor. However, whether these two important pathways are co-activated in breast cancers and whether the co-activation is associated with overall progression of breast cancer have not been investigated. Herein, we report that STAT3 and TrkA are more co-activated in triple-negative and HER2-enriched breast cancers, compared to luminal subtypes, as determined by immunohistochemical staining of 33 invasive breast carcinomas and datamining data of over 1,500 breast cancer patients. We also observed that high co-activation of both JAK2-STAT3 and TrkA pathways significantly shortens overall metastasis-free survival of both triple-negative and HER2-enriched breast cancer patients when compared to patients with low co-activation. Similarly, we also find that JAK2-STAT3 and TrkA co-activation also significantly shortens brain, lung, and bone metastasis-free survival in both of these breast cancer subtypes, suggesting a critical role for JAK2-STAT3 and TrkA in distant metastasis of aggressive breast cancers. Taken together, our findings indicate a novel signaling crosstalk between JAK2-STAT3 and TrkA pathways in triple-negative and HER2-enriched breast cancers, and the use of their co-activation as a prognostic indicator for metastatic breast cancers of both subtypes. Citation Format: Angelina T. Regua, Noah R. Aguayo, Sara Abu Jalboush, Daniel L. Doheny, Sara G. Manore, Dongqin Zhu, Grace L. Wong, Austin Arrigo, Calvin J. Wagner, Yang Yu, Karen Baylon, Alexandra Thomas, Michael D. Chan, Jimmy Ruiz, Guangxu Jin, Roy E. Strowd, Peiqing Sun, Linda J. Metheny-Barlow, Jiayuh Lin, Hui-Wen Lo. JAK2/STAT3 and TrkA pathways are frequently co-activated in triple-negative and HER2-enriched breast cancers and the co-activation correlates with an increased potential of metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1979.