176 - Interactions Between TPM4-positive Hepatocellular Carcinoma Cells and IL32-positive Monocytes Mediate the Formation and Progression of Portal Vein Tumor Thrombus in Hepatocellular Carcinoma

Purpose: Hepatocellular carcinoma (HCC) with portal vein tumor thrombus (PVTT) progresses rapidly and carries a high mortality. Multiple clinical studies indicate that, compared with patients without PVTT, those with PVTT derive limited benefit from TACE combined with targeted therapy and immunotherapy. This study aimed to characterize the tumor microenvironment (TME) of HCC without PVTT and HCC with PVTT, and to elucidate mechanisms underlying PVTT formation and suboptimal therapeutic efficacy.

Materials and Methods: Primary tumors from 3 patients with BCLC stage A HCC and primary tumors plus PVTT tissues from 3 patients with BCLC stage C HCC were subjected to single-cell RNA sequencing. Findings were validated and prognostic relevance assessed using TCGA-LIHC and the GSE77509 public dataset.

Results: The TME comprised tumor cells, endothelial cells, fibroblasts, T/NK cells, myeloid cells, and B cells. Compared with HCC without PVTT (HCCNP), HCC with PVTT (HCCP) showed marked alterations in tumor cells. TCGA-LIHC patients exhibiting the tumor cells molecular signature of HCCP had significantly reduced overall survival (OS). Pathway enrichment highlighted disruption of cell junctions and polarity, cytoskeletal remodeling, vascular adhesion, and pro-proliferative signaling. Tumor cells in HCCP displayed elevated TPM4 expression.High TPM4 expression in TCGA-LIHC was associated with shorter OS, and TPM4 was further upregulated in PVTT. TPM4-positive tumor cells were enriched for “regulation of actin cytoskeleton” and “focal adhesion" indicating enhanced migration–adhesion–colonization capacity, and engaged inflammatory/immune-evasive programs via “IL-17 pathway” and “NOD-like receptor pathway''. CellChat analysis revealed strengthened interactions between TPM4-positive tumor cells and myeloid cells, with the strongest interaction observed with IL32-positive monocytes. TPM4-positive tumor cells likely secrete SPP1 to engage CD44 on IL32-positive monocytes. The presence of IL32-positive monocytes correlated with reduced OS and was enriched for“cellular senescence” and "leukocyte transendothelial migration", promotes cell migration, vascular infiltration, and an immunosuppressive microenvironment.

Conclusion: TPM4-positive tumor cells drive PVTT formation and, through interactions with IL32-positive monocytes, establish an immunosuppressive microenvironment that fosters HCC progression and contributes to poor first-line therapeutic efficacy.