PGP and melanoma: Carcinoma of colon, kidney, adrenal gland, pancreas, and liver express high P-gp levels while intermediate P-gp levels are expressed in neuroblastomas, soft tissue carcinomas, hematological malignancies including CD34-positive acute myeloid leukemias, etc. with low P-gp levels expressed in malignancies of lung, esophagus, stomach, ovary, breast, melanomas, lymphomas, multiple myelomas, and acute promyelocytic leukemia but may display elevated P-gp levels after chemotherapy due to acquired drug resistance (Velingkar and Dandekar, 2010).