HIF Inactivation of p53 in Ovarian Cancer Can Be Reversed by Topotecan, Restoring Cisplatin and Paclitaxel Sensitivity

Abstract

Ovarian cancer growth under hypoxic conditions results in hypoxia-inducible factor-1a (HIF1a) stabilization. HIF1a is an adverse prognostic factor that may contribute to worse outcomes via its capacity to bind to p53, potentially blocking p53-mediated apoptosis. We determined whether HIF1a-p53 binding occurred in hypoxic ovarian cancer cell lines, and if this blocked p53 transcriptional activity. Topotecan (TPT), used in the treatment of ovarian cancer, inhibits HIF1a translation via a topoisomerase-1 (TOPO1)-dependent mechanism. We examined if TPT knockdown of HIF1a restored p53 transcriptional function. TPT effects on HIF1a and p53related transcriptional targets were assessed by PCR. Associations between TPT effects and TOPO1 expression levels were examined by Western blots and knockdown by siRNA. RNAbinding protein immunoprecipitation was used to assess if TOPO1 was resident on HIF1a mRNA. We determined if sublethal doses of TPT, used to knockdown HIF1a, reversed hypoxia-related cisplatin and paclitaxel resistance (XTT assay). Flow cytometry was used to assess HIF1a-mediated upregulation of ABCB1 and ABCB5 efflux pump expression. We found that HIF1a binding to, and inhibition of, p53 transcriptional activity in hypoxic ovarian cancer cells was associated with drug resistance. TPT-mediated downregulation of HIF1a in hypoxic cells required TOPO1 resident on HIF1a mRNA, restored p53 transcriptional activity, downregulated ABCB1/ ABCB5 cell surface expression, and reversed hypoxia-related cisplatin and paclitaxel resistance.Implications: TPT-mediated reduction of HIF1a accumulation in hypoxic ovarian cancer cell lines restores p53 tumorsuppressor function, offering a novel approach to reverse chemoresistance. Further clinical investigation is warranted.

Mechanisms of Taxane Resistance

“…Moreover, siRNA inhibition of HIF1-α also decreased MDR1 and restored PTX sensitivity [291]. MDR1 expression was increased in hypoxic conditions but was reduced following treatment with the clinical topoisomerase 1 inhibitor topotecan (TPT) [292], further supporting the interaction between HIF1-α levels and drug efflux pumps in taxane resistance. TPT indirectly inhibits HIF1-α by preventing its translation [292,293].…”

“…MDR1 expression was increased in hypoxic conditions but was reduced following treatment with the clinical topoisomerase 1 inhibitor topotecan (TPT) [292], further supporting the interaction between HIF1-α levels and drug efflux pumps in taxane resistance. TPT indirectly inhibits HIF1-α by preventing its translation [292,293]. Though successful at inhibiting HIF1-α, TPT is not effective enough as a monotherapy and may only benefit patients with increased hypoxia signal and the presence of topoisomerase 1.…”

“…In fact, it was found that TPT should be used as a second-line therapy due to the efficacy not being markedly better than PTX [294]. HIF1-α was also found to interact with p53 in hypoxic conditions using co-IP, possibly due to inhibition by HIF1-α on p53's pro-apoptotic function [292]. It is clear that HIF1-α coordinates with multiple resistance proteins in ovarian cancer, but more research should be done on the prevalence of hypoxia in ovarian solid tumors before assigning HIF1-α to biomarker status.…”

Cabozantinib Reverses Topotecan Resistance in Human Non-Small Cell Lung Cancer NCI-H460/TPT10 Cell Line and Tumor Xenograft Model

“…Reduction of topoisomerase I protein expression was observed in NCI-H460 cells treated with 30 nM TPT and the combination of TPT and 5 µM CBZ, as well as in NCI-H460/TPT10 cells treated with the drug combination. It has been reported that TPT could decrease the protein expression of topoisomerase I in ovarian cancer cells and breast cancer cells (D'Onofrio et al, 2011;Parmakhtiar et al, 2019). The downregulation of topoisomerase I expression in NCI-H460 cells upon TPT or combination treatment and in NCI-H460/TPT10 cells upon combination treatment may be explained by the accumulated TPT in NCI-H460 cells and the restored TPT level by CBZ in NCI-H460/TPT10 cells.…”

<p>UBE2N Regulates Paclitaxel Sensitivity of Ovarian Cancer via Fos/P53 Axis</p>

“…It has been reported that inhibition of P53 transcriptional activity is associated with paclitaxel resistance in ovarian cancer cells, and restore P53 transcriptional activity can reverse paclitaxel sensitivity. 47 Hailing Yang et al reported that P53 expression was upregulated in ovarian cancer cells after paclitaxel stimulation, and the overexpression of TAP63, a P53 family member, led to apoptosis in paclitaxel-resistant ovarian cancer cells after treatment with paclitaxel. 48 According to these studies, we speculate that Fos is a potential target for the regulation of paclitaxel sensitivity, and maybe participates in the regulation via suppressing P53's apoptotic contribution to drug response in ovarian cancer cells.…”