Multidrug resistance (MDR) presents a serious problem in
cancer chemotherapy. Our previous studies have shown that
guggulsterone could reverse MDR through inhibiting the function and expression of
P-glycoprotein (P-gp). The present study is to further investigate the reversal effects of
guggulsterone on MDR in
drug-resistant
cancer cell lines. The effects of
guggulsterone on MDR1mRNA gene expression, intracellular pH, P-gp
ATPase activity and
glucosylceramide synthase (GCS) expression were assessed by RT-PCR,
Laser Scanning Confocal Microscope using the pH-sensitive
fluorescent probe BCECF-AM, Pgp-Glo assay system, and flow cytometric technology, respectively. The results showed that
guggulsterone ranging from 2.5 to 80 μM significantly promoted the activity of P-gp
ATPase in a dose-dependent manner. The intracellular pH of K562/DOX cells was found to be higher than K562 cells.
After treatment with
guggulsterone (1, 3, 10, 30, 100 μM), intracellular pH of K562/DOX cells decreased in a dose- and time-dependent manner. However, the present study revealed that
guggulsterone ranging from 3 to 100 μM had little influence on MDR1 gene expression in K562/DOX cells. Further, the isogenic
doxorubicin-resistant MCF-7/DOX cells exhibited a 4.9-fold increase in GCS level as compared with parental MCF-7 human
breast cancer cells.
After treatment with
guggulsterone (0.1, 1, 10 μM) for 48 h, MCF-7/DOX cells were found to have no change of GCS
protein expression amount.
Guggulsterone might be a potent MDR reversal agent, and its mechanism on MDR needs more research.