Upregulation of NOX-2 and Nrf-2 Promotes 5-Fluorouracil Resistance of Human Colon Carcinoma (HCT-116) Cells

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Bhargav N. Waghela¹, Foram U. Vaidya¹, and Chandramani Pathak^1,2,a*

¹School of Biological Sciences & Biotechnology, Indian Institute of Advanced Research, Koba Institutional Area, 382426 Gujarat, Gandhinagar, India

²Amity Institute of Biotechnology, Amity University Haryana, 122413 Gurgaon, India

^* To whom correspondence should be addressed.

Received July 14, 2020; Revised September 21, 2020; Accepted September 21, 2020

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Altered expression of cellular redox genes and proteins contributes to invasion, metastasis, and drug resistance in cancer. NADPH oxidase (NOX) isoforms are the pro-oxidant enzymes that generate ROS as a primary product. Dysregulation of NOX activity and expression alters ROS generation, which either directly or indirectly modulates cell death and survival signaling during the progression of cancer. Nuclear factor erythroid 2-related factor 2 (Nrf-2) is an inducible transcription factor, which transcribes an array of antioxidant genes and protects cancer cells from the oxidative stress. Both NOXs and Nrf-2 participate in the regulation of cellular redox homeostasis; but their dysregulation promotes oxidative stress, which contributes to the progression of different types of cancer. Indeed, the role of NOX isoforms and Nrf-2 in developing the drug resistance in cancer is largely unknown. In the present study, we have explored the association of NOX isoforms and Nrf-2 signaling with the MDR1 gene expression in colon carcinoma cells (HCT-116/R). The MDR1 gene was overexpressed to develop resistant HCT-116/R cells and the NOX activation and ROS generation were monitored. We also assessed the role of NOX isoforms and Nrf-2 in the 5-fluorouracil (5-FU) mediated apoptotic cell death of HCT-116/R cells. The HCT-116/R cells demonstrated higher expression of HIF-1α, Nrf-2, and HO-1 and were highly resistant to 5-FU; they also displayed upregulated expression and activity of NOX-2, as well as elevated ROS levels. Interestingly, the treatment with HDC, a specific NOX-2 inhibitor, reduced the ROS levels in HCT-116/R cells. The treatment with HDC and ML-385 (specific inhibitor of Nrf-2) augmented the 5-FU-mediated apoptotic cell death of HCT-116/R cells, which suggests that NOX-2 and Nrf-2 are involved in the development of the chemoresistant phenotype of these cells. Taken together, NOX-2 and Nrf-2 are associated with developing drug resistance of colorectal cancer cells and might be potential targets to overcome drug resistance during cancer therapy.

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KEY WORDS: 5-fluorouracil, drug resistance, HO-1, MDR1, NOX-2, Nrf-2, ROS

DOI: 10.1134/S0006297921030044

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