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

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• Human concentrative nucleoside transporters (hCNTs) mediate nucleoside uptake, including anticancer drugs.
• hCNT1, a specific pyrimidine transporter, is implicated in tumor progression and its downregulation is observed in some cancers.
• Mechanisms underlying hCNT1 downregulation in digestive cancers like colorectal and pancreatic adenocarcinoma remain largely unknown.

Purpose of the Study:

• To investigate changes in hCNT1 expression in colorectal and pancreatic ductal adenocarcinoma.
• To explore the role of microRNAs (miRNAs) in regulating hCNT1 in these cancers.
• To determine if hCNT1 downregulation by miRNAs contributes to chemoresistance.

Main Methods:

• Analysis of hCNT1 protein levels in tumor and adjacent non-tumoral tissues from colorectal and pancreatic cancer patients.
• Investigation of potential miRNA regulation of hCNT1, focusing on oncomiRs miR-106a and miR-17.
• Correlation of hCNT1 expression with response to fluoropyrimidine-based treatments.

Main Results:

• hCNT1 protein was significantly downregulated in both colorectal and pancreatic ductal adenocarcinoma tissues compared to adjacent non-tumoral tissues.
• A direct regulatory relationship was identified between oncomiRs miR-106a and miR-17 and the loss of hCNT1 expression.
• These findings suggest hCNT1 inhibition by specific oncomiRs contributes to chemoresistance.

Conclusions:

• hCNT1 downregulation is a feature of colorectal and pancreatic ductal adenocarcinoma.
• OncomiRs miR-106a and miR-17 directly inhibit hCNT1 expression in these cancers.
• Inhibition of hCNT1 by these oncomiRs represents a novel mechanism contributing to fluoropyrimidine chemoresistance in digestive cancers.