STK4 and breast cancer: It is in part in line with the findings that HIFs may upregulate the expression of tumor suppressor lncRNA mitochondrial oxygen-responsive transcript 1 (MTORT1), which sponges off miR-26a-5p from its targets CREB1 and serine/threonine kinase 4 (STK4), and inhibits cell growth and proliferation in breast cancer cells (158), in contrast to the well-established tumor promoting functions of HIFs under hypoxic conditions.