(1) Zheng X (2) Fu J (3) Chen G (4) Huang Y (5) Huang J (6) Li Z (7) Zhong W (8) Wu B (9) Tang R (10) Yue Y (11) Huang T (12) Meng L (13) Mou P (14) Chen P (15) Guo L (16) Dong X (17) Liu X (18) Zeng Y (19) Cai Z

Journal for immunotherapy of cancer | Free PMC Article

Zheng et al. showed that in human HCC, XIAP is markedly upregulated and inversely correlated with CD8+ T cell tumor infiltration and RFS. Treatment of orthotopic HCC mouse models with the SMAC mimetic Birinapant boosted MHC-­I expression, reduced PD-­L1 levels, induced short-term immune cell tumor infiltration and mediated modest antitumor effects. Birinapant combined with personalized NeoVAC therapy expanded less exhausted, cytotoxic, neoantigen-­specific CD8+ Tem cells, promoted DC antigen presentation, and shifted TAMs toward a pro-­inflammatory phenotype to safely stimulate potent tumor control, immune memory, and protection against metastases.

Contributed by Paula Hochman

BACKGROUND: Personalized neoantigen vaccines offer a rational immunotherapeutic strategy for hepatocellular carcinoma (HCC), but their efficacy is limited by insufficient tumor immunogenicity and an immunosuppressive tumor microenvironment. Tumor-intrinsic factors that constrain vaccine-induced immune responses in HCC are not well defined. X-linked inhibitor of apoptosis protein (XIAP) is frequently overexpressed in HCC and has been linked to immune evasion, raising the possibility that targeting XIAP may improve the effectiveness of neoantigen-based vaccination. METHODS: XIAP expression is examined in human HCC specimens using transcriptomic analysis and multiplex immunofluorescence. A personalized neoantigen vaccine (NeoVAC) is generated and evaluated in combination with Birinapant, a clinically investigated second mitochondria-derived activator of caspases (SMAC) mimetic, and IAP antagonist, in orthotopic HCC and KPC-OVA-ICC mouse models. Antitumor efficacy is assessed by bioluminescence imaging and survival analysis. Immune landscapes are characterized by flow cytometry, immunohistochemistry, multiplex immunofluorescence, and single-cell RNA sequencing. Neoantigen-specific immune responses are further assessed using functional assays. RESULTS: XIAP is markedly upregulated in human HCC and inversely associates with intratumoral CD8+T_cell infiltration and recurrence-free survival. Birinapant treatment increases major histocompatibility complex class I (MHC-I) expression, reduces PD-L1 levels, and facilitates immune-cell infiltration, but only has modest antitumor effects as monotherapy. In contrast, combining Birinapant with NeoVAC substantially improves tumor control. A notable proportion of treated mice achieves complete tumor regression, accompanied by durable protection against tumor rechallenge and metastatic dissemination. These effects are associated with the expansion of neoantigen-specific Ly6C(+)CD8(+) T cells exhibiting effector-memory features, strong cytotoxic capacity, and limited exhaustion, together with enhanced dendritic-cell antigen presentation and a shift of tumor-associated macrophages toward a pro-inflammatory M1-like phenotype. CONCLUSIONS: These data identify XIAP expression as a clinical correlate of an immune-refractory HCC phenotype and show that pharmacological IAP antagonism with Birinapant enhances tumor immunogenicity and supports antigen-specific T-cell immunity. The findings provide a preclinical rationale for combining the SMAC mimetic Birinapant with neoantigen vaccine-based immunotherapy in HCC.

Citation: J Immunother Cancer 2026 Oct 9 14: Epub10/09/2026

Link to PUBMED: http://www.ncbi.nlm.nih.gov/pubmed/42855228

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