ABCG2 and cancer: Recent research established that GH regulates multiple key mechanisms of making tumors resistant to anti-cancer drugs (chemotherapy and targeted therapy) including but not limited to increasing tumoral drug efflux via ABC transporters, inducing epithelial-to-mesenchymal transition (EMT), suppressing apoptosis, increasing cancer stem cells (CSCs), and inducing fibrosis and extracellular matrix (ECM) remodeling (31).