This is the first study exploring miRs associated with resistance to trastuzumab-based chemotherapy in HER2-positive oesophago-gastric cancer cell lines using large-scale screening methods followed by an evaluation of circulating miR-148a-3p in HER2-positive advanced oesophago-gastric cancer patients treated with trastuzumab-based chemotherapy. Here, ERBB2 is linked to gastric cancer.