Uncoupling CD4+ TIL-Mediated Tumor Killing from JAK-Signaling in Melanoma

Purpose: Impaired MHCI-presentation and insensitivity to interaction. Around 40% of melanomas constitutively express immune effector molecules are common features of immune MHC Class II molecules; hence, melanomas with or without checkpoint blockade (ICB)-resistant tumors and can be, respecnatural constitutive MHC Class II expression (MHCIIconstþ or tively, associated with loss of b2 microglobulin (B2M) or impaired MHCIIconst-) were used. IFNg signaling. Patients with ICB-resistant tumors can respond to Results: CD4þ TIL-mediated cytotoxicity was not affected by alternative immunotherapies, such as infusion of autologous B2M loss but was dependent on the expression of CIITA. tumor-infiltrating lymphocytes (TIL). CD4þ T cells can exert MHCIIconstþ melanomas were killed by tumor-specific CD4þ TILs cytotoxic functions against tumor cells; however, it is unclear even in the absence of IFNg-mediated MHCII upregulation, where-whether CD4þ T-cell responses can be exploited to improve the as IFNg was necessary for CD4þ TIL-mediated cytotoxicity against clinical outcomes of patients affected by ICB-resistant tumors. MHCIIconst- melanomas. Notably, although tumor-specific CD4þ Experimental Design: Here, we exploited CRISPR (clustered TILs did not kill JAK1KO MHCIIconst- melanomas even after IFNg regularly interspaced short palindromic repeats)/Cas9 gene edit-stimulation, sensitivity to CD4þ TIL-mediated cytotoxicity was ing to reproduce immune-resistant tumor phenotypes via gene maintained by JAK1KO MHCIIconstþ melanomas. knockout (KO). To determine the role of cytotoxic CD4þ TILs Conclusions: In conclusion, our data indicate that exploiting in ICB-resistant tumors, we investigated CD4þ TIL-mediated tumor-specific cytotoxic CD4þ TILs could help overcome resistance cytotoxicity in matched pairs of TILs and autologous melanoma to ICB mediated by IFNg-signaling loss in MHCIIconstþ melanomas. cell lines, used as a model of patient-specific immune-tumor See related commentary by Betof Warner and Luke, p. 3829