Immunosuppression and phenotypic plasticity in an atlas of human hepatocholangiocarcinoma

Background: Hepatocholangiocarcinoma (H-ChC) has the clinicopathological features of both hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA) and is a more aggressive subtype of primary hepatic carcinoma than HCC or iCCA. Methods: We sequenced 91,112 single-cell transcriptomes from 16 human samples to elucidate the molecular mechanisms underlying the coexistence of HCC and iCCA components in H-ChC.Results: We observed two molecular subtypes of H-ChC at the whole-transcriptome level (CHP and CIP), where a metabolically active tumour cell subpopulation enriched in CHP was characterized by a cellular pre differentiation property. To define the heterogeneity of tumours and their associated microenvironments, we observe greater tumour diversity in H-ChC than HCC and iCCA. H-ChC exhibits weaker immune cell infiltration and greater CD8+ exhausted T cell (Tex) dysfunction than HCC and iCCA. Then we defined two broad cell states of 6,852 CD8+ Tex cells: GZMK+ CD8+ Tex cells and terminal CD8+ Tex cells. GZMK+ CD8+ Tex cells exhibited higher infiltration of after treatment in H-ChC, the effector scores and expression of the immune checkpoints of them greatly increased after immunotherapy, which indicated that H-ChC might be more sensitive than HCC or iCCA to immunotherapy. Conclusions: In this paper, H-ChC was explored, hoping to contribute to the study of mixed tumours in other cancers.