Effect of VAV1 on metastasis and immune evasion in squamous cell carcinoma.

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Background: Cancer progression is shaped by continuous adaptation to environmental constraints. While metastatic dissemination and immune evasion are often studied independently, whether tumors dynamically switch between these programs under therapeutic pressure remains unclear. Methods: Using a genome-wide CRISPR–Cas9 screen in murine squamous cell carcinoma (SCC), combined with in vivo immune checkpoint blockade models, extracellular vesicle profiling, proteomics, and functional immunological assays, we interrogated molecular determinants governing tumor state transitions under immune pressure. Results: We identify VAV1 as a critical molecular switch that bifurcates tumor evolutionary trajectories. Elevated VAV1 expression drives epithelial–mesenchymal transition and metastatic competence, defining an invasive tumor state. However, upon immune checkpoint blockade and CD8⁺ T cell–mediated cytotoxic stress, tumor cells rapidly downregulate VAV1 and transition into an immune-resistant state. Mechanistically, VAV1 constrains extracellular trafficking of GSDMD-N through an HSPB1-dependent complex. Loss of VAV1 unleashes exosomal export of GSDMD-N into the tumor microenvironment, where it induces neutrophil pyroptosis and robust neutrophil extracellular trap (NET) formation. NET accumulation suppresses CD8⁺ T cell effector function and promotes T cell exhaustion, thereby establishing a protective immunosuppressive niche that blunts therapeutic efficacy. These findings reveal that tumor cells do not merely survive immune pressure—they reprogram their microenvironment to neutralize it. Conclusions: Our findings reveal that VAV1 functions as a strategic regulator of tumor evolutionary behavior. During early tumorigenesis, elevated VAV1 expression confers metastatic competence, enabling rapid dissemination in a manner analogous to an aggressive expansion strategy. In contrast, under immune checkpoint blockade, selective pressure imposed by activated CD8⁺ T cells drives VAV1 downregulation, reprogramming tumor cells toward an immune-resistant state characterized by GSDMD-N–mediated NET formation and microenvironmental suppression. Thus, VAV1 operates as a molecular decision node that coordinates a switch between metastatic expansion and immune defense. Rather than being passive targets of therapy, tumor cells dynamically recalibrate their signaling circuitry to optimize survival under changing constraints. This adaptive capacity underscores the evolutionary sophistication of cancer and identifies the GSDMD-N–NETs axis as a tractable vulnerability for disrupting tumor immune resilience.