The results showed that miR-4521 expression was suppressed under hypoxic conditions in different GC cell lines (the parental GC cell lines SGC7901, BGC823 and MGC803, and the lowly invasive cell lines SGC7901-L and BGC823-L) and breast carcinoma cell line MCF7 as well as lung carcinoma cell line A549, accompanied by HIF-1α induction (Fig. 3a, b). This evidence concerns the gene HIF1A and lung carcinoma.