IMP1/IGF2BP1 alters extracellular vesicle cargo in colorectal cancer

Abstract

BackgroundColorectal cancer (CRC) is the third leading cause of cancer‐related death worldwide. There is an urgent need for new therapeutic targets and methods of early detection to improve patient outcomes. Extracellular Vesicles (EVs) and EV cargo are promising new biomarkers and therapeutic targets. EVs are secreted nanoparticles that carry DNA, RNA, and proteins. EVs can target specific cell types and once taken up by a destination cell, EV cargo can shape cell gene expression and physiology. EVs can shape the tumor microenvironment (TME) (i.e., stromal, immune, and endothelial cells), which plays critical roles in patient survival and disease outcomes. Our current understanding of how EV cargo is determined and how it influences the CRC cell TME is limited. One promising but understudied molecular aspect of EVs is RNA binding proteins (RNAbps). RNAbps are post‐transcriptional regulators of gene expression and could provide a link between host cell gene expression and EV cargo. Insulin‐like growth factor 2 RNA binding protein 1 (IMP1, IGF2BP1) is an RNAbp with a critical role in CRC development and progression. IMP1 is expressed highly in CRC tumors, expression correlates with worse prognosis, and IMP1 binds/potently regulates tumor‐associated transcripts. How EV cargo is influenced by IMP1 and effects on EV targeting to destination cells and on target cell gene expression and function is not known. Understanding how IMP1 shapes EV cargo and which TME cells are targeted, will identify new mechanisms of cancer development/progression through IMP1‐EV‐mediated alteration of the TME and novel EV cargo as candidates for early detection biomarkers.HypothesisWe hypothesize that IMP1 facilitates the packaging of tumor‐promoting EV cargo that interact and communicate with the TME to enhance tumor progression.MethodsEVs were isolated from IMP1 null and IMP1‐overexpressing (IMP1OE) CRC cell lines, HT‐29, SW480, as well as wildtype Caco2 cells (express high levels of IMP1) by size‐exclusion chromatography. EVs were assessed by nanoparticle tracking analysis, western blot, electron microscopy, and qPCR.ResultsWe found that IMP1 enters EVs from Caco2 and SW480 IMP1OE cell lines, but not HT‐29 IMP1OE or corresponding null controls. IMP1 did not alter EV secretion in CRC cell lines. We found that IMP1 target mRNAs, such as KRAS, cMYC are present within EVs, but not the IMP1 target PTGS2.ConclusionsOur novel findings suggest that IMP1 enters the EV to directly influence EV cargo in specific CRC cell lines. Our findings have implications for the development of novel early detection biomarkers and therapeutic approaches in CRC.