Those stem-like prostate cancer cells show high expression of ABCB1, which encodes multidrug resistance-related protein P-glycoprotein, leading to the Doc-resistance in prostate cancer.
Steroid derivatives were studied for their growth-inhibitory effect, cytotoxicity, reversal of multidrug resistance, apoptosis induction, and interaction with doxorubicin on multidrug resistant human ATP-binding cassette, sub-family B, member 1 (ABCB1) gene-transfected mouse T-lymphoma cell line, and human PC-3 and LNCaP prostate cancer cell lines in vitro.
Differential expression of the multidrug resistance 1 (MDR1) protein in prostate cancer cells is independent from anticancer drug treatment and Y box binding protein 1 (YB-1) activity.
Several combination therapies and small P-glycoprotein inhibitors have been proposed to improve the therapeutic potential of docetaxel in prostate cancer.
Taken together, these results provide strong evidence that TPL overcomes MDR in prostate cancer cells by downregulating MDR1 expression, and suggest that TPL is a promising agent for prostate cancer therapy, especially for chemoresistant prostate cancer.
Previously, we described that MDR phenotype in PCa could be related with high basal and drug-induced expression of MDR proteins P-Glycoprotein (P-Gp), MRP1, and LRP.
Hypermethylation was more frequent in PCa than in BPH tissues (EDNRB, 100% versus 88%; TIG1, 96% versus 12%; RARbeta, 95% versus 35%; GSTP1, 93% versus 15%; APC, 80% versus 50%; MDR1, 80% versus 31%; PTGS2, 68% versus 15%; Reprimo, 59% versus 19%; and Annexin2, 4% versus 0%).
To test our hypothesis, prostate cancer samples (170) and benign prostatic hyperplasia samples (69) were examined by methylation-specific PCR for three genes: adenomatous polyposis coli (APC), glutathione S-transferase pi (GSTP1), and multidrug resistance 1 (MDR1).
Receiver operator characteristic curve analyses suggested that CpG island hypermethylation changes at GSTP1, APC, RASSF1a, PTGS2, and MDR1 in various combinations can distinguish primary prostate cancer from benign prostate tissues with sensitivities of 97.3-100% and specificities of 92-100%.
These findings suggest that CpG hypermethylation of MDR1 promoter is a frequent event in prostate cancer and is related to disease progression via increased cell proliferation in prostate cancer cells.
The study was focused on the inhibition of MDR by blocking the ADR1 gene expression and through the inhibition of the pump-function of mdr-p-glycoprotein, in human breast cancer cell lines expressing mrp and prostate cancer cell line (PC-3).
We hypothesize that early in prostate cancer progression, increased expression of YB-1 may increase P-gp activity which may in turn lower androgen levels in the prostate tumor cells.
These data suggest that drug resistance in human prostate cancer may be multifactorial, with MRP and LRP frequently expressed in prostate cancer cells before antineoplastic drug treatment and P-gp expression occasionally acquired after drug exposure.