AUTHOR=Wang Qian , Wei Xin , Hu Lanyan , Zhuang Lingling , Zhang Hong , Chen Qi 

TITLE=Hedgehog−Gli2 Signaling Promotes Chemoresistance in Ovarian Cancer Cells by Regulating MDR1

JOURNAL=Frontiers in Oncology

VOLUME=11

YEAR=2022

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2021.794959

DOI=10.3389/fonc.2021.794959

ISSN=2234-943X

ABSTRACT=<sec><title>Background</title><p>Cisplatin (DDP) resistance remains a key challenge in improving the clinical outcome of patients with ovarian cancer (OC). <italic>Gli2</italic> overexpression can lead to DDP resistance in OC cells, but the specific underlying regulatory mechanism remains unclear. The membrane transporter encoding gene <italic>MDR1</italic> positively regulates chemotherapy resistance in various cancer types. We evaluated <italic>MDR1</italic> as a potential <italic>Gli2</italic> downstream target and the contribution of the <italic>Gli2/MDR1</italic> axis in promoting DDP resistance in OC cells.</p></sec><sec><title>Methods</title><p>To generate drug-resistant SKOV3/DDP cells, SKOV3 cells were grown for six months under continuous induction wherein the DDP concentration was steadily increased. <italic>Gli2</italic> expression in OC cells with varying DDP sensitivities was detected using western blot. Cell counting kit-8 assays were used to assess the DDP sensitivity of SKOV3, SKOV3/DDP, A2780, and A2780/DDP cells and reversal of DDP resistance in SKOV3/DDP and A2780/DDP cells. Cell proliferation was analyzed using 5-ethynyl-2′-deoxyuridine (EdU) incorporation assays. The transcriptional regulation of <italic>MDR1</italic> by <italic>Gli2</italic> was determined using luciferase reporter assays. Finally, xenograft OC tumors were generated in nude mice, which were then treated with intraperitoneal DDP or phosphate-buffered saline (PBS) injections to investigate if <italic>Gli2</italic> affected DDP resistance in OC <italic>in vivo</italic>.</p></sec><sec><title>Results</title><p>DDP-resistant SKOV3/DDP and A2780/DDP cells showed higher expression of <italic>Gli2</italic> and <italic>MDR1</italic> as compared with that in DDP-sensitive OC cells. <italic>Gli2</italic> knockdown in SKOV3/DDP cells significantly reduced <italic>MDR1</italic> expression, whereas it increased DNA damage, thereby sensitizing OC cells to DDP. Similar results were obtained after targeting Gli2 expression with the Gli-antagonist 61 inhibitor (GANT61) in SKOV3/DDP and A2780/DDP cells. In cells stably overexpressing <italic>Gli2</italic>, treatment with gradient concentrations of verapamil, an MDR1 inhibitor, significantly inhibited <italic>MDR1</italic> expression. Our findings indicate that downregulation of <italic>MDR1</italic> expression may reverse OC cell resistance to DDP. Moreover, dual-luciferase reporter gene assays confirmed that <italic>MDR1</italic> is a direct downstream target of <italic>Gli2</italic>, with <italic>Gli2</italic> positively regulating <italic>MDR1</italic> expression. Finally, subcutaneous xenotransplantation in nude mice demonstrated that <italic>Gli2</italic> plays a key role in regulating OC drug resistance.</p></sec><sec><title>Conclusions</title><p>We identified a mechanism by which Hedgehog-<italic>Gli</italic> signaling regulates OC chemoresistance by modulating <italic>MDR1</italic> expression. Hence, <italic>Gli2</italic> and <italic>MDR1</italic> are potential biomarkers and therapeutic targets in patients with chemoresistant OC.</p></sec>