CLK1 Promotes MDSC Trafficking and Reprograms the Tumor Microenvironment by activating Hippo/YAP signaling in Colorectal Cancer

Colorectal cancer (CRC) is a highly heterogeneous malignancy, characterized by complex interactions between tumor cells and the immune system. The tumor microenvironment (TME) plays a crucial role in CRC progression and response to therapy. However, its regulatory mechanisms remain poorly understood due to the genetic and phenotypic diversity of tumor cells. In this study, we investigated the tumor-intrinsic factors contributing to TME formation and evaluated genotype-based combination strategies to enhance the efficacy of immunotherapy in CRC. RNA sequencing, single-cell analysis, and immunohistochemistry were conducted to identify pro-oncogenic proteins associated with low immune activation. Functional studies using in vitro co-culture systems, subcutaneous CRC tumor models, flow cytometry, and immunohistochemistry revealed the pivotal role of CLK1 in tumor progression and immunosuppressive TME remodeling. Mechanistically, CLK1 activation led to hyperactivation of the Hippo signaling pathway, promoting nuclear translocation of YAP and subsequent transcriptional upregulation of the chemokine CXCL1. Elevated CLK1 expression correlated with increased infiltration of myeloid-derived suppressor cells (MDSCs) and impaired antitumor immune responses. Knockdown of CLK1 significantly reduced MDSC recruitment and restored CD8+ T cell activity. Moreover, combined CLK1 knockdown and anti-PD1 therapy synergistically enhanced intratumoral CD8⁺ T cell infiltration and elicited robust antitumor responses in murine CRC models. Collectively, our findings identify the CLK1-Hippo/YAP-CXCL1 signaling axis as a key regulator of immune evasion and TME remodeling in CRC, and highlight its potential as a therapeutic target to improve the efficacy of immune checkpoint blockade.