Mismatch repair-proficient (pMMR)/microsatellite-stable (MSS) tumors, representing the majority of solid cancers, remain largely unresponsive to immune checkpoint inhibitors, highlighting the urgent need for effective therapeutic strategies. Tumor cell vaccines, serving as delivery platforms for a broad repertoire of tumor antigens, hold potential for eliciting systemic antitumor immunity, yet their clinical efficacy has remained limited. Here, we developed Tβ1KO/PolyIC-Vac, an off-the-shelf therapeutic whole-tumor cell vaccine generated by CRISPR-Cas9-mediated TGF-β1 knockout and formulated with the TLR3 agonist Poly(I:C). In therapeutic vaccination models, subcutaneous vaccination significantly suppressed distal tumor growth, reduced lung metastases, and delayed spontaneous colorectal tumor progression. It also synergized with anti-PD-1 blockade, enhancing complete response rates and establishing baseline antitumor immunity. Mechanistically, knockout of tumor-derived TGF-β1 reprogrammed immunity by reducing MDSC accumulation to relieve local immunosuppression and activate dendritic cells in draining lymph nodes, while intrinsically triggering the tumor STAT1-IL-15 axis to enhance vaccine immunogenicity. Poly(I:C) further enhanced cross-presentation and adaptive immunity, conferring long-term cross-protection against heterologous tumors. Together, these findings establish Tβ1KO/PolyIC-Vac as a universal tumor vaccine platform capable of efficiently delivering a comprehensive repertoire of tumor antigens and eliciting robust, durable, and cross-protective tumor-specific immunity in immunotherapy-resistant pMMR/MSS tumors.

Whole-tumor-cell vaccine  /  TGF-β1 knockout  /  Poly(I:C)  /  pMMR/MSS tumors  /  Immunotherapy  /  Immune checkpoint blockade  /  Adaptive immune priming  /  Antigen presentation