Obese Adipose Tissue‐Derived Extracellular Vesicles increase Colorectal Cancer Cell proliferation and glycolysis

Abstract

Colorectal cancer (CRC) is the second deadliest cancer worldwide and obesity is an established risk factor for both men and women. However, we still have limited knowledge regarding the molecular mechanisms that support obesity‐induced CRC. Obesity substantially modifies the adipose tissue (AT) and increases secretion of various factors including nanometer‐sized extracellular vesicles (EVs). EVs are lipid bilayer vesicles released from most types of cells and contain lipids, proteins, microRNAs and other cytoplasmic components of the parent cell. Considering their ability to travel to distant sites and deliver cargo to recipient cells, EVs could act as intercellular mediators that alter the tumorigenic potential of recipient cancer cells. Therefore, we hypothesized that obese AT secreted EVs carry cargo that enhances tumorigenicity of CRC cells. Here, we aimed to determine the functional and metabolic changes induced by obese human AT‐secreted EVs on human CRC cell lines. Visceral AT tissue from patients with obesity (BMI>35) undergoing bariatric surgery and non‐obese patients (BMI<30) undergoing anti‐reflux surgery was cultured ex vivo in EV‐free DMEM‐H/Ham’s F12 for 48 hrs. Conditioned media was collected and EVs were isolated by ultracentrifugation. EV size and concentration were measured through Nanoparticle Tracking Analysis (NTA). EV protein cargo was characterized by unbiased proteomics analysis using LC‐MS. Human CRC cell lines HCT‐116 and HT‐29 were treated with 10^7 EV/ml for 24 or 48 hrs and proliferation and mitochondrial/glycolytic ATP production were measured by CCK‐8 assay or Seahorse XF ATP Rate Assay, respectively. NTA reported our EV preps were on average 120 nm in size, suggesting we isolated exosomes and/or small microvesicles. Using KEGG Pathway Database and Panther Protein Classification Software, 25% of EV proteins secreted from human AT were associated with metabolism, with 13% of total metabolic proteins in EVs associating with glycolysis. Obese EVs exhibited increased expression of glycolytic enzymes pyruvate kinase, phosphoglycerate kinase 1, and G3P dehydrogenase. Obese EVs increased proliferation and glycolytic ATP production in CRC cell lines, both serving as indicators of cancer aggressiveness. Taken together, our results suggest that obese adipose EVs mediate the tumorigenic potential of CRC cells. Our study is significant since it aims to identify druggable pathways which support tumorigenesis in obese CRC patients.