PGP and malignant colon neoplasm: In this paper, we have examined chemopreventive effect of celastrol on drug resistant colon cancer cells, including its impact on functional/transporter activity of the P-gp, on frequency of apoptosis and necrosis in colon cancer cell cultures, as well as on size of the SP cells subpopulation (subpopulation of cancer cells assumed to be enriched with cancer stem cells; CSCs).