Abstract 2936: Molecular characterization of the immune subclass of hepatocellualr carcinoma

Background: Immune checkpoint inhibitors have emerged as a promising therapeutic approach in different solid tumors, including hepatocellular carcinoma (HCC). Nonetheless, little is known about the immune-component of HCC or potential biomarkers of response to these therapies. Aims: To perform comprehensive characterization of the HCC immunological profile and to identify biomarkers to select immunotherapy candidates. Methods: We performed gene expression array deconvolution through non-negative matrix factorization in 228 resected HCCs. Characterization of the transcriptional landscape was conducted using >1,000 signatures representing distinct immune cells by gene set enrichment and nearest template prediction analyses. Presence of immune infiltration, tertiary lymphoid structure (TLS), PD-1 and PD-L1 immunostainings was investigated using immunohistochemistry. DNA methylation profile of 450K CpG sites was analyzed to identify those with significant differences for each group. Extensive validation of the immune classifier was performed in 728 independent HCC samples. Results: Overall, an immune-related subclass of HCC was identified in ~27% of patients. The immune subclass was characterized by gene signatures identifying immune cells (i.e. T cells, TLS, cytotox, p<0.001), signatures of response to immune checkpoint therapy (p<0.001), presence of high immune infiltration (p=0.01), TLS (≥5 foci, 19/51 vs 33/168, p=0.01) and PD-1 and PD-L1 protein expression (p<0.05). The methylation levels of 363 CpG sites in 192 immune response gene promoters were able to capture the Immune class (ANOVA, p<0.05, Δβ>0.2 Tukey test). Integration with HCC molecular classifications revealed significant enrichment of the Immune subclass with IFN and S1 (p<0.001) and exclusion of the CTNNB1 and S2 (p<0.001) subclasses. The immune class contains two distinct microenvironment-based types: A) Exhausted immune response type (~35%) characterized by stromal activation, T cell exhaustion signatures, and presence of immunosuppressive components such as TGFB, LGALS1, M2 macrophages and pathways able to recruit myeloid-derived-suppressor cells (FDR<0.01); and B) Active immune response type (~65%) characterized by overexpression of adaptive immune response genes and IFN signaling (p<0.001). Tumors within the active immune response type showed a trend towards better survival vs rest (p=0.07). Conclusions: Around 27% of HCC patients belong to the Immune class, characterized by activation of immune cells and signatures of response to immunotherapies. Within this subclass, two distinct types have been characterized by presenting active or exhausted immune responses, a feature that provides the rationale for precision medicine-based therapies. Note: This abstract was not presented at the meeting. Citation Format: Daniela Sia, Yang Jiao, Iris Martinez, Olga Kuchuk, Carlos Villacorta Martin, Manuel Castro de Moura, Juan Putra, Genis Camprecios, Swan Thung, Samuel Waxman, Vincenzo Mazzaferro, Manel Esteller, Augusto Villanueva, Josep Maria Llovet. Molecular characterization of the immune subclass of hepatocellualr carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2936. doi:10.1158/1538-7445.AM2017-2936