Knockout of Shcbp1 sensitizes immunotherapy by regulating α‐SMA positive cancer‐associated fibroblasts

Abstract The crucial role of cancer‐associated fibroblasts (CAFs) in promoting T‐cell exclusion has a significant impact on tumor immune evasion and resistance to immunotherapy. Therefore, enhancing T‐cell infiltration into solid tumors has emerged as a pivotal area of research. We achieved a conventional knockout of Shcbp1 ( Shcbp1 −/− ) through CRISPR/Cas9 gene editing and crossed these mice with spontaneous breast cancer MMTV‐PyMT mice, resulting in PyMT Shcbp1 −/− mice. The different CAF subtypes were detected by flow cytometry analysis (FCA). We evaluated collagen and CAFs levels using Sirius red staining, immunohistochemistry (IHC), and immunofluorescence (IF). Primary tumor cells and CAFs were isolated from both PyMT Shcbp1 +/+ and PyMT Shcbp1 −/− mice. We analyzed CAFs’ proliferation, invasion, migration, apoptosis, and cell cycle. Transwell coculture experiments were performed with primary tumor cells and CAFs to evaluate the role of CAFs in increasing the sensitivity of tumor cells to Erdafitinib. Tumors from PyMT Shcbp1 +/+ and PyMT Shcbp1 −/− mice were orthotopically transplanted to assess the therapeutic effect of the Erdafitinib and PD‐1 combination. CAFs and T‐cell infiltration in these tumors were assessed using FCA and IF. Knockout of Shcbp1 leads to a significant reduction in tumor burden, promotes longer survival, and decreases CAFs in MMTV‐PyMT. Moreover, knockout of Shcbp1 enhances the sensitivity of Erdafitinib, leading to effective inhibition of CAFs' proliferation and invasion, as well as the induction of apoptosis. Additionally, it results in cell cycle arrest at the G2/M phase in vitro. Meanwhile, Shcbp1 −/− CAFs change the sensitivity of Shcbp1 −/− tumor cells to Erdafitinib compared to Shcbp1 +/+ CAFs. Importantly, knockout of Shcbp1 boosts the effectiveness of Erdafitinib in combination with immune checkpoint blockade therapy by augmenting T‐cell infiltration through CAFs regulation in vivo. Our findings demonstrate that knockout of Shcbp1 holds significant potential in enhancing the therapeutic response of Erdafitinib combined with PD‐1 antibody treatment, offering promising prospects for future breast cancer therapies.