Targeting <i>p21</i> ‐High Senescent Kupffer Cells Nanotherapeutically Potentiates Antitumor Immunity in Advanced Hepatocellular Carcinoma with Portal Vein Tumor Thrombus

ABSTRACT Hepatocellular carcinoma (HCC) patients with portal vein tumor thrombus (PVTT) are associated with a significantly poor prognosis and limited treatment options. Single‐cell RNA sequencing (scRNA‐seq) has revealed senescent Kupffer cells (sKCs), which are characterized by high levels of p21 expression and enriched in the tumor microenvironment (TME) of HCC‐PVTT. These sKCs exhibit a pronounced senescence‐associated secretory phenotype (SASP), promoting the proliferation and invasion of tumors and crosstalk with cancer‐associated fibroblasts. To target sKCs, a biomimetic nanodelivery system termed SKEV@AAV has been developed. This system comprises adeno‐associated virus (AAV) vectors carrying p21 ‐specific shRNA, encapsulated within sKCs‐derived exosomes (SKEV). SKEV@AAV effectively downregulated p21 , suppressed SASP signaling, and disrupted pro‐tumor interactions between sKCs and cancer‐associated fibroblasts. In an orthotopic PVTT model, SKEV@AAV showed single‐agent antitumor activity and attenuated SASP‐associated inflammatory remodeling. Furthermore, the combination efficacy with anti‐PD‐1 was evaluated in a murine splenic liver‐metastasis model, where SKEV@AAV reduced tumor burden, enhanced CD8 + T‐cell infiltration, decreased regulatory T cells, and promoted memory T‐cell differentiation. Our findings reveal a pivotal role of sKCs in mediating immune suppression in HCC‐PVTT and provide a nanotherapeutic strategy that reverses sKCs' senescence, reprograms the TME, and ultimately enhances antitumor immune activation.