Enhancement of PD-L1-attenuated CAR-T cell function through breast cancer-associated fibroblasts-derived IL-6 signaling via STAT3/AKT pathways

Abstract

Background Carcinoma-associated fibroblasts (CAFs) play a critical role in cancer progression and immune cell modulation. In this study, it was aimed to evaluate the roles of CAFs-derived IL-6 in doxorubicin (Dox) resistance and PD-L1-mediated chimeric antigenic receptor (CAR)-T cell resistance in breast cancer (BCA). Methods CAF conditioned-media (CM) were collected, and the IL-6 level was measured by ELISA. CAF-CM were treated in MDA-MB-231 and HCC70 TNBC cell lines and siIL-6 receptor (IL-6R) knocked down (KD) cells to determine the effect of CAF-derived IL-6 on Dox resistance by flow cytometry and on increased PD-L1 through STAT3, AKT and ERK1/2 pathways by Western blot analysis. After pre-treating with CM, the folate receptor alpha (FRα)-CAR T cell cytotoxicity was evaluated in 2D and 3D spheroid culture assays. Results The results showed a significant level of IL-6 in CAF-CM compared to that of normal fibroblasts (NFs). The CM with high IL-6 level significantly induced Dox resistance; and PD-L1 expression through STAT3 and AKT pathways in MDA-MB-231 and HCC70 cells. These induction effects were attenuated in siIL-6R KD cells. Moreover, the TNBC cell lines that were CM-treated with STAT3 and an AKT inhibitor had a reduced effect of IL-6 on PD-L1 expression. BCA cells with high IL-6 containing-CM treatment had resistance to cancer cell killing by FRα CAR-T cells compared to untreated cells. Conclusion These results highlight CAF-derived IL-6 in the resistance of chemotherapy and T cell therapy. Using inhibitors of IL6-STAT3/AKT-PD-L1 axis may provide a potential benefit of Dox and CAR-T cell therapies in BCA patients.

Chemerin promotes invasion of oral squamous cell carcinoma cancer by stimulating IL-6/TNF-α production via STAT3 signaling pathway

“…The STAT3 pathway has been reported to be involved in the regulation of IL-6 production [11]. We therefore investigated the possible mechanism that chemerin mediates IL-6/TNF-a secretion via activation of STAT3 in OSCC cells.…”

Small molecule agents for triple negative breast cancer: Current status and future prospects

“…Interleukin-6 (IL-6) is a crucial inflammatory cytokine that plays a significant role in tumor development. Overexpression of IL-6 in tumor tissues can stimulate the overactivation of JAK/STAT3 signaling pathway, leading to tumor angiogenesis, chemotherapy resistance, and tumor immunosuppression [268] , [269] , [270] , ultimately resulting in a poor prognosis for patients [271] . Regulation of the IL-6/JAK/STAT3 pathway can inhibit tumor proliferation and metastasis, and activate tumor immunity to control the malignant progression of tumors [ 272 , 273 ].…”

Modulation of the tumor microenvironment and mechanism of immunotherapy-based drug resistance in breast cancer

“…TAM depletion by sequential administration of TAM targeting T cells followed by cancer targeting T cells, resulting in reduction in tumor size and longer survival in mouse ovarian cancer model [ 336 ]. CAF-derived IL-6 contributes to immune therapy resistance and inhibition of the IL-6-STAT3/Akt-PD-L1 axis resensitizes to immune therapy in breast cancer patients [ 337 ]. In addition, MDSC is an essential component of the TME to be considered in immunotherapy outcomes.…”