MicroRNAs (miRs) may be involved in primary resistance to HER2 inhibitors and represent a clinically useful biomarker for gastro-oesophageal cancer (GOC) patients with HER2 amplified disease. Identification of miRs responsible for resistance to HER2 inhibitors may allow us to develop a novel, reproducible, non-invasive and cost-effective tool for GOC patient stratification. Defining predictive biomarkers of resistance to HER2 inhibitors would enable patient selection, minimise chances of severe toxicity in those less likely to respond, and may define novel strategies to restore drug sensitivity.
A high-throughput large-scale RNA interference screen in the HER2-amplified GOC cell line NCI-N87 and the HER2-non-amplified cell line FLO-1 was performed in order to discover novel miRs involved in sensitivity and resistance to trastuzumab. Cells were transfected using a library of 1015 miR mimics, control miRs and siRNAs, and siPLK1 positive control. They were treated 48 hours later with cisplatin + 5FU + trastuzumab based on IC50 data previously obtained. Cell viability was analysed after 72 hrs of continuous drug treatment by fluorescence-based assay (Cell Titer Blue® and EnVision™). Data from 3 biological replicates was analysed and shortlisting of significant hits was based on the concordance among data from different replicates. miRs were considered significant if they caused >40% decrease in cell viability with a t-test p value of
Thirty-two miRs caused >40% decrease in cell viability and were associated with a p value of 40% decrease in cell viability and were associated with a p value of
We identified a panel of miRs associated with GOC resistance to HER2 inhibitors in combination with chemotherapy. Inhibition of these miRs significantly affects GOC cell viability and and restores sensitivity to HER2 inhibitors plus chemotherapy. These miRs require validation with Exiqon miR inhibitors and Nanostring analysis. Translational studies will be conducted in the ST03 HER2 substudy (EUDRACT 2006-000811-12).
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Cancer Research UK
D. Cunningham: Institution has received research funding from AstraZeneca, Amgen, Celgene, Merck Serono, Sanofi, Merrimack, and Medimmune. All other authors have declared no conflicts of interest.