Immunovascular classification of HCC reflects reciprocal interaction between immune and angiogenic tumor microenvironments

Background and Aims: Immune cells and tumor vessels constitute important elements in tumor tissue; however, their detailed relationship in human tumors, including HCC, is still largely unknown. Consequently, we expanded our previous study on the immune microenvironment of HCC and analyzed the relationship among the immune microenvironment, inflammatory/angiostatic factor expression, angiogenic factor expression, and tumor vessel findings, including vessels encapsulating tumor clusters (VETC) and macrotrabecular-massive (MTM) patterns. Approach and Results: We classified HCC into four distinct immunovascular subtypes (immune-high/angiostatic [IH/AS], immune-mid/angio-mid [IM/AM], immune-low/angiogenic [IL/AG], and immune-low/angio-low [IL/AL]). IH/AS, IM/AM, and IL/AG subtypes were associated with decreasing lymphocytic infiltration and increasing angiogenic factor expression and VETC/MTM positivity, reflecting their reciprocal interaction in the tumor microenvironment of HCC. IL/AG subtype was further characterized by CTNNB1 mutation and activation of Wnt/β-catenin pathway. IL/AL subtype was not associated with increased lymphocyte infiltration or angiogenic factor expression. Prognostically, IH/AS subtype and VETC/MTM positivity were independently significant in two independent cohorts. Increased angiogenic factor expression was not necessarily associated with VETC/MTM positivity and poor prognosis, especially when inflammatory/angiostatic milieu coexisted around tumor vessels. These results may provide insights on the therapeutic effects of immunotherapy, antiangiogenic therapies, and their combinations. The potential of evaluating the immunovascular microenvironment in predicting the clinical effect of these therapies in nonresectable HCC needs to be analyzed in the future study. Conclusions: HCC can be classified into four distinct immunovascular subtypes (IH/AS, IM/AM, IL/AG, and IL/AL) that reflect the reciprocal interaction between the antitumor immune microenvironment and tumor angiogenesis. In addition to its clinicopathological significance, immunovascular classification may also provide pathological insights on the therapeutic effect of immunotherapy, antiangiogenic therapy, and their combination.