OncomiRs miR-106a and miR-17 negatively regulate the nucleoside-derived drug transporter hCNT1

Abstract

High-afnity uptake of natural nucleosides as well as nucleoside derivatives used in anticancer therapies is mediated by human concentrative nucleoside transporters (hCNTs). hCNT1, the hCNT family member that specifcally transports pyrimidines, is also a transceptor involved in tumor progression. In particular, oncogenesis appears to be associated with hCNT1 downregulation in some cancers, although the underlying mechanisms are largely unknown. Here, we sought to address changes in colorectal and pancreatic ductal adenocarcinoma both of which are important digestive cancers in the context of treatment with fuoropyrimidine derivatives. An analysis of cancer samples and matching non-tumoral adjacent tissues revealed downregulation of hCNT1 protein in both types of tumor. Further exploration of the putative regulation of hCNT1 by microRNAs (miRNAs), which are highly deregulated in these cancers, revealed a direct relationship between the oncomiRs miR-106a and miR-17 and the loss of hCNT1. Collectively, our fndings provide the frst demonstration that hCNT1 inhibition by these oncomiRs could contribute to chemoresistance to fuoropyrimidine-based treatments in colorectal and pancreatic cancer.