Oxidative Stress Promotes Doxorubicin‐Induced Pgp and BCRP Expression in Colon Cancer Cells Under Hypoxic Conditions

Abstract

P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) are ATP binding cassette (ABC) transporters that are overexpressed in different drug-resistant cancer cell lines. In this study, we investigated whether doxorubicin promotes Pgp and/or BCRP expression to induce drug resistance in colon cancer cells under hypoxic conditions. We analyzed HIF-1α activity via ELISA, Pgp, and BCRP expression by qRT-PCR and the relationship between doxorubicin uptake and ABC transporter expression via confocal microscopy in HT-29WT and HT-29 doxorubicin-resistant colon cancer cells (HT-29DxR). These cells were treated with doxorubicin and/or CoCl (chemical hypoxia), and reactive oxygen species inductors. We found that the combination of chemically induced hypoxia and doxorubicin promoted Pgp mRNA expression within 24 h in HT-29WT and HT-29DxR cells. Both doxorubicin and CoCl alone or in combination induced Pgp and BCRP expression, as demonstrated via confocal microscopy in each of the above two cell lines. Thus, we surmised that Pgp and BCRP expression may result from synergistic effects exerted by the combination of doxorubicin-induced ROS production and HIF-1α activity under hypoxic conditions. However, HIF-1α activity disruption via the administration of E3330, an APE-1 inhibitor, downregulated Pgp expression and increased doxorubicin delivery to HT-29 cells, where it served as a substrate for Pgp, indicating the existence of an indirect relationship between Pgp expression and doxorubicin accumulation. Thus, we concluded that Pgp and BCRP expression can be regulated via cross-talk between doxorubicin and hypoxia, promoting drug resistance in HT-29 WT, and HT-29DxR cells and that this process may be ROS dependent. J. Cell. Biochem. 118: 1868-1878, 2017. © 2017 Wiley Periodicals, Inc.

Inhibition of the Receptor Tyrosine Kinase AXL Restores Paclitaxel Chemosensitivity in Uterine Serous Cancer

“…For example, Lin and colleagues showed that inhibition of AXL reversed EMT in prostate cancer cells, but they did not assess whether chemosensitivity could be restored with AXL knockdown [25]. Similarly, several reports suggest that inhibition or knockdown of AXL reduces the resistance of mesenchymal cells to chemotherapeutic drugs while also reverting them to an epithelial state [18, 33, 38, 50, 51]. Our finding that inactivation of AXL improves chemosensitivity without affecting the mesenchymal phenotype indicates that AXL directly regulates chemoresistance.…”

“…Fold change was calculated using the 2(x0005E)(-ΔΔCT) method. Primer sequences were previously published [9, 38, 39]. …”

Therapeutic Inhibition of the Receptor Tyrosine Kinase AXL Improves Sensitivity to Platinum and Taxane in Ovarian Cancer

“…mRNA expression was normalized with respect to glyceraldehyde-3-phosphate dehydrogenase, and fold change was calculated by the 2 (ÀDDCT) method. Primer sequences were previously published (18,(24)(25)(26).…”

MDR1 in immunity: friend or foe?

“…35 The modulation of glucose levels and the oxidative stress also induces HIF-1α and MDR1 expression. 36,37 MDR1 is also regulated at RNA level by micro RNAs (miR) such as miR-145, miR-27a and miR-331-5p that bind directly the 3ʹUTR of ABCB1 mRNA to decrease MDR1 expression. 38,39 Some other miR (miR-137) indirectly decrease MDR1 expression by targeting the YB-1 transcription factor that upregulates MDR1 expression by fixation on ABCB1 promoter.…”