PDK4-driven metabolic reprogramming enhances mesothelial cell invasion in colorectal cancer peritoneal metastasis

Abstract

Mesothelial cells play an important role in colorectal cancer peritoneal metastasis (CRC-PM), where they support tumor growth and invasion. In this study, we investigate the molecular mechanisms by which mesothelial cells contribute to CRC metastasis. Using single-cell RNA sequencing (scRNA-seq) on tissue samples from 12 CRC patients with peritoneal metastasis, we identify PDK4 as a key gene in mesothelial cells during metastasis. The expression of PDK4 is significantly greater in mesothelial cells undergoing mesothelial-to-mesenchymal transition (MMT) compared to normal peritoneal cells, suggesting its involvement in mesothelial cell reprogramming during peritoneal metastasis. In vitro experiments show that coculturing mesothelial cells with CRC cells leads to increased PDK4 expression, which in turn enhances mesothelial cell migration and invasion. Knockdown of PDK4 reduces mesothelial cell invasion, while overexpression of PDK4 increases invasive ability, highlighting its critical role in mesothelial cell invasion. Additionally, PDK4 promotes metabolic changes, specifically increasing fatty acid oxidation (FAO), which is necessary for mesothelial cell invasion. Blocking FAO reduces the invasive ability of PDK4-overexpressing mesothelial cells, while restoring FAO in PDK4-knockdown cells rescues their invasion potential. Further analysis shows that PDK4 enhances the acetylation of β-catenin, a protein involved in cell movement, and that this modification is crucial for mesothelial cell invasion. Our results suggest that PDK4 regulates mesothelial cell invasion through β-catenin acetylation following metabolic reprogramming, offering a potential target for therapies aimed at inhibiting CRC-PM.

1. Introduction

Colorectal cancer (CRC) is one of the most common malignancies in China [1]. Among the various metastatic routes, peritoneal metastasis (PM) is particularly prevalent. However, its prognosis is significantly worse than that of patients with lung and liver metastases [2]. To date, the mechanisms underlying peritoneal metastasis are not fully understood, largely because of the heterogeneity of the process [3–5]. Peritoneal metastasis begins with the adhesion of tumor cells to the peritoneum, which is covered by a layer of mesothelial cells. Once metastasis is established, tumor cell invasion is facilitated not only by the tumor cells themselves but also by interactions with the extracellular matrix (ECM) and stromal cells [5–7]. These interactions help create a favorable microenvironment for metastatic growth.

Mesothelial cells, which constitute a signature cell type of the peritoneum, are influenced by various signaling molecules, such as transforming growth factor-beta (TGF-β), platelet-derived growth factor (PDGF), and fibroblast growth factor (FGF). These signals trigger mesothelial-to-mesenchymal transition (MMT), where mesothelial cells lose their epithelial characteristics and acquire mesenchymal traits [8,9]. This transition promotes ECM degradation and enhances the invasive potential of interacting tumor cells. Additionally, MMT contributes to an immunosuppressive tumor microenvironment and provides a source of cancer-associated fibroblasts (CAFs) [10].