Tumor-Associated Fibroblasts Promote HER2-Targeted Therapy Resistance through FGFR2 Activation

Abstract

Purpose: Despite the therapeutic success of existing HER2-targeted therapies, tumors invariably relapse. This study aimed at identifying new mechanisms responsible for HER2-targeted therapy resistance. Experimental Design: We have used a platform of HER2-targeted therapy–resistant cell lines and primary cultures of healthy and tumor-associated fibroblasts (TAF) to identify new potential targets related to tumor escape from anti-HER2 therapies. Results: We have shown that TAFs promote resistance to HER2-targeted therapies. TAFs produce and secrete high levels of FGF5, which induces FGFR2 activation in the surrounding breast cancer cells. FGFR2 transactivates HER2 via c-Src, leading to resistance to HER2-targeted therapies. In vivo, coinoculating nonresistant cell lines with TAFs results in more aggressive and resistant tumors. Resistant cells activate fibroblasts and secrete FGFR ligands, creating a positive feedback loop that fuels resistance. FGFR2 inhibition not only inhibits HER2 activation, but also induces apoptosis in cells resistant to HER2-targeted therapies. In vivo, inhibitors of FGFR2 reverse resistance and resensitize resistant cells to HER2-targeted therapies. In HER2 patients' samples, α-SMA, FGF5, and FGFR2 contribute to poor outcome and correlate with c-Src activation. Importantly, expression of FGF5 and phospho-HER2 correlated with a reduced pathologic complete response rate in patients with HER2-positive breast cancer treated with neoadjuvant trastuzumab, which highlights the significant role of TAFs/FGF5 in HER2 breast cancer progression and resistance. Conclusions: We have identified the TAF/FGF5/FGFR2/c-Src/HER2 axis as an escape pathway responsible for HER2-targeted therapy resistance in breast cancer, which can be reversed by FGFR inhibitors.

Metformin suppresses HIF‐1α expression in cancer‐associated fibroblasts to prevent tumor‐stromal cross talk in breast cancer

“…Tissue from all specimens was minced into small pieces and digested to further isolate the fibroblast population. 9 The obtained fibroblasts were seeded in 10% of FBS-DMEM medium and cultured under standard conditions (37°C under a humidified atmosphere with 5% CO 2 ). The purity of the CAFs was evaluated by morphological assessments and immunofluorescence analyses of α-smooth muscle actin (Supplementary Figure S1A).…”

Mesenchymal stem cells induce PD‐L1 expression through the secretion of CCL5 in breast cancer cells

“…(2019) (Truong et al, 2019). A large number of studies documented the effects of CAF cells on morphology changes of various types of cancer cells (Fernandez-Nogueira et al, 2019;Miyazaki et al, 2019;Yu et al, 2014;Zhuang et al, 2015).…”

Stromal Oncostatin M axis promotes breast cancer progression

“…Human breast cancer-associated (CAF-173, CAF-200, CAF-220 and CAF-318) and normal fibroblasts (RMF-31 and RMF-39) were derived from human breast tumours and reduction mammoplasty surgeries respectively, immortalized, tagged with GFP and cultured in collagen pre-coated flasks 34 . The aforementioned human mammary fibroblasts, TS1 cells derived from primary tumours of the MMTV-PyMT mice model 27,75 , LM2 breast cancer cells (kindly donated by Dr. Roger Gomis) and HS27 skin fibroblasts (kindly donated by Dr. Ander Izeta) were cultured in DMEM medium supplemented with 10% fetal bovine serum (FBS), 1% glutamine, and 1% penicillin and streptomycin.…”

“…Depletion of OSMR in the tumour microenvironment resulted in delayed tumour onset and tumour growth ( As we previously observed that fibroblasts were the cell population with higher levels of OSMR within the stroma (Fig. 3), we performed complementary in vitro and in vivo experiments to assess the effect of OSMR activation in mammary cancer-associated and normal fibroblasts derived from human breast tumours and reduction mammoplasty surgeries 34 , respectively. The ability to remodel the extracellular matrix is a hallmark of CAFs 25 .…”