Monocarboxylate Transporter-1 Is Dispensable for Hepatocellular Carcinoma Development

Hepatocellular carcinoma (HCC) is the most prevalent type of liver cancer and the deadliest liver disease. It is imperative to understand the underlying molecular mechanisms involved in the development of HCC. Monocarboxylate transporter-1 (MCT1) is a proton-coupled protein that facilitates the bidirectional transport of monocarboxylates, such as lactate and pyruvate, across the plasma membrane to maintain the cellular metabolism and energy supply. MCT1 was found to be upregulated in human HCC specimens, and its inhibition reduced xenograft tumor growth. However, the role of MCT1 in HCC remains to be further investigated using immune-competent in vivo models. To better understand the role of MCT1 in HCC, we established liver-specific MCT1 knockout mice. We found that deletion of MCT1 in liver cells did not affect morphology, proliferation, or apoptosis. DEN/CCl4 model, where a single injection of DEN is followed by repeated injections of CCl4, was used to induce HCC in mice. Intriguingly, we found that liver-specific knockout of MCT1 was not sufficient to reduce the size or count of DEN/CCl4-induced liver tumors. In addition, we used immunohistochemical staining to evaluate the expression of Ki67, collagen A1, and myeloperoxidase, and we found that MCT1 knockout was not able to hinder the proliferation, fibrosis, and inflammation in the DEN/CCl4-induced HCC tumors. In conclusion, MCT1 is dispensable for HCC development, and its deletion was insufficient to alleviate the phenotypic repercussions of HCC tumors in the DEN/CCl4-induced HCC model.