EPAS1 (HIF2A) and dexamethasone-activated glucocorticoid receptor NR3C1 (GCR or GR), in the presence of the NR3C1 co-factor PELP1, cooperatively bind to adjacent hypoxia response and glucocorticoid response elements in the PTK6 gene promoter. The cooperative binding of EPAS1 and NR3C1 to the PTK6 gene promoter may be facilitated by p38 MAPK-mediated phosphorylation of NR3C1 on serine residue S134. EPAS1 expression can also be stimulated by the activated NR3C1. EPAS1 and NR3C1-mediated activation of PTK6 expression may play an important role in the progression of the triple negative breast cancer (Regan Anderson et al. 2016).