Multidrug resistance remains a major challenge in the
chemotherapy of
breast cancer.
Guajadial, a natural meroterpenoid, has been found to possess anti-
tumor activity. However, the role of
guajadial in drug resistance has not been investigated. The aim of this study was to evaluate the effect of
guajadial on drug resistance in
drug-resistant
breast cancer cells. Cell viability was measured by MTT assay, and the IC50 values were calculated. The expression of
ATP-binding cassette (
ABC) transporters including
P-glycoprotein (P-gp) and the
breast cancer resistance
protein (BCRP) was detected by qRT-PCR and western blot. The expression of Akt, p-Akt,
p70S6K, and p-p70S6K was determined by western blot. We found that
guajadial significantly inhibited cell viability of parental non-resistant cell line MCF-7,
adriamycin (ADR)-resistant cell line MCF-7/ADR, and
paclitaxel (PTX)-resistant cell line MCF-7/PTX in a dose-dependent manner.
Guajadial enhanced ADR and PTX sensitivity of MCF-7/ADR and MCF-7/PTX cells, and inhibited the expression of P-gp and BCRP.
Guajadial treatment resulted in an inactivation of PI3K/Akt pathway in
drug-resistant MCF-7 cells. In conclusion,
guajadial acted as an inhibitor of drug resistance, which might be mediated by the inhibition of
ABC transporter expression and PI3K/Akt pathway in
drug-resistant
breast cancer cells. These findings suggested that
guajadial treatment might be a new approach to overcome the drug resistance in the
chemotherapy of
breast cancer.