Hepatocellular carcinoma (HCC) is an immunotherapy-resistant malignancy characterized by high cellular heterogeneity. The diversity of cell types and the interplay between tumor and non-tumor cells remain to be clarified. Single cell RNA sequencing of human and mouse HCC tumors revealed heterogeneity of cancer-associated fibroblast (CAF). Cross-species analysis determined the prominent CD36 ⁺ CAFs exhibited high-level lipid metabolism and expression of macrophage migration inhibitory factor (MIF). Lineage-tracing assays showed CD36 ⁺ CAFs were derived from hepatic stellate cells. Furthermore, CD36 mediated oxidized LDL uptake-dependent MIF expression via lipid peroxidation/p38/CEBPs axis in CD36 ⁺ CAFs, which recruited CD33 ⁺ myeloid-derived suppressor cells (MDSCs) in MIF- and CD74-dependent manner. Co-implantation of CD36 ⁺ CAFs with HCC cells promotes HCC progression in vivo. Finally, CD36 inhibitor synergizes with anti-PD-1 immunotherapy by restoring antitumor T-cell responses in HCC. Our work underscores the importance of elucidating the function of specific CAF subset in understanding the interplay between the tumor microenvironment and immune system.

Metastasis is one of the main causes of poor prognosis for hepatocellular carcinoma (HCC), which has been linked to cell-death resistance. Autophagy is an important survival mechanism under conditions of cell stress. We hypothesized that autophagy may play a role in HCC metastasis due to its prosurvival effect. Highly metastatic HCC cell lines with stable autophagy inhibition were established via lentivirus-mediated silencing of BECN1 and ATG5 genes. Mouse models of pulmonary metastasis were then developed using the cells with or without autophagy inhibition. The analysis of lung metastasis by histopathological examination and small animal imaging showed that autophagy inhibition significantly decreased the incidence of pulmonary metastases in vivo. Further invasion, migration, detachment, lung colonization, and epithelial-mesenchymal transition (EMT) assays indicated that autophagy inhibition did not affect cell invasiveness, migration or EMT but attenuated the anoikis-resistance and lung colonization of HCC cells. Investigation of the molecular mechanisms underlying showed that the autophagy-inhibition-mediated anoikis-resistance attenuation was associated with the regulation of apoptotic signaling. As autophagy inhibition was shown to be able to suppress HCC metastasis, an autophagy-based HCC tissue-specific target therapy system (AFP-Cre/LoxP-shRNA) was constructed. In vitro and in vivo analyses showed that the system was able to efficiently inhibit autophagy of HCC cells and tissue in a tissue-specific manner. Further in vivo metastasis assay showed that intratumoral administration of the system could significantly suppress lung metastasis. Together, our findings suggest that autophagy may be involved in HCC metastasis through facilitating anoikis resistance and lung colonization of HCC cells. Autophagy-based HCC tissue-specific target therapy may be a new strategy for the management of HCC metastasis.

Background and Aims: Monocarboxylate transporter (MCT) 4 is a high‐affinity lactate transporter that is primarily involved in the maintenance of intracellular pH homeostasis and highly expressed in different tumors. However, the role of MCT4 in modulating immune responses against HCC remains unknown. Approach and Results: In this study, we demonstrated that MCT4 was overexpressed in HCC, which was associated with poor prognosis in patients. Genetic or pharmacological inhibition of MCT4 using VB124 (a highly potent MCT4 inhibitor) suppressed HCC tumor growth in immunocompetent mice model by enhancing CD8 ⁺ T cell infiltration and cytotoxicity. Such improved immunotherapy response by MCT4 targeting was due to combined consequences characterized by the alleviated acidification of tumor microenvironment and elevated the chemokine (C‐X‐C motif) ligand (CXCL) 9/CXCL10 secretion induced by reactive oxygen species/NF‐κB signaling pathway. Combining MCT4 inhibition improved the therapeutic benefit of anti–programmed cell death 1 immunotherapy in HCC and prolonged mice survival. Moreover, higher MCT4 expression was observed in tumor tissues from nonresponder patients with HCC receiving neoadjuvant therapy with toripalimab. Conclusions: Our results revealed that lactate exportation by MCT4 has a tumor‐intrinsic function in generating an immunosuppressive HCC environment and demonstrated the proof of the concept of targeting MCT4 in tailoring HCC immunotherapeutic approaches.