ABCG2 and cancer: This includes (a) modulation of growth factors and their receptors linked with the specific signaling pathways, (b) modification of transcription factors, (c) alterations in the tumor environment, (d) epithelial-mesenchymal transition, (e) cancer stem cells’ development, (f) ABC transporters, (g) modulation of apoptosis/autophagy and cancer cell proliferation, and (h) activation of gene repair processes.