Abstract 24P
Background
Pancreatic ductal adenocarcinoma (PDAC) has a dismal long-term patient survival rate. This poor prognosis is in part due to poor patient responses to current standard-of-care chemotherapy regimens. Patients receiving platinum-based chemotherapy often succumb to treatment resistance. MicroRNAs (miRNAs) are small, non-coding RNAs that play an important role in modulating cellular processes involved in chemo-resistance. Here, we identify a molecular mechanism underpinning miR-31-mediated alterations in platinum agent chemosensitivity, supporting miR-31 as an important therapeutic target.
Methods
A pCMV-miR vector containing a miR-31 mimic was stably expressed into a miR-31-deficient PDAC cell line, BxPC-3. Additionally, a pmiRZip lentivector suppressing miR-31 was stably expressed into a miR-31 abundant PDAC cell line, Panc-1. ICP-MS post cisplatin treatment was used to measure levels of Pt195 within the cytoplasmic and nuclear compartments. To assess ATOX1 alterations, a pCMV6-AC-ATOX1 overexpression vector was stably expressed into Panc-1 cells and a pRS ATOX1 shRNA suppression vector was stably expressed into BxPC-3 cells.
Results
MiR-31 overexpression in BxPC-3 cells significantly promoted resistance to cisplatin. Reciprocally, miR-31 suppression in Panc-1 cells significantly enhanced cisplatin sensitivity. Kaplan-Meier survival analysis of PDAC patients showed that low miR-31 expression inversely correlates with high expression of ATOX1, a cytoplasmic copper (Cu) chaperone and transcription factor, and that these patients have significantly improved overall survival. Overexpression of miR-31 significantly reduced ATOX1 expression in PDAC cells. MiR-31 expression inversely correlated with the nuclear accumulation of Pt195 in PDAC cells. Moreover, direct overexpression of ATOX1 in Panc-1 cells resulted in a significant increase in sensitivity to cisplatin. Reciprocally, direct suppression of ATOX1 in BxPC-3 cells resulted in a significant increase in resistance to cisplatin.
Conclusions
Our study demonstrates that miR-31 regulates ATOX1 expression, which modulates platinum chemotherapy shuttling to the nucleus, promoting either a chemo-resistant or chemo-sensitive phenotype in PDAC.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Breakthrough Cancer Research, Ireland.
Disclosure
All authors have declared no conflicts of interest.