Bryan Oronsky1, Curtis Scribner2, Rahul Aggarwal3, Pedro Cabrales4. 1. EpicentRx Inc, 4445 Eastgate Mall, Suite 200, San Diego, CA, 92121, USA. boronsky@epicentrx.com. 2. EpicentRx Inc, 4445 Eastgate Mall, Suite 200, San Diego, CA, 92121, USA. 3. Helen Diller Comprehensive Cancer Center, University of California San Francisco, UCSF, Box 1711, San Francisco, CA, 94143, USA. 4. Department of Bioengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, San Diego, CA, 92093, USA.
Abstract
BACKGROUND: RRx-001, a minimally toxic next-generation checkpoint inhibitor that targets myeloid suppressor cells in the tumor microenvironment, has also been shown to protect normal tissues from the cytotoxic effects of chemotherapy and radiation. The following experiments were carried out to determine whether the cytoprotective functions of RRx-001 in normal cells were operative in tumor cells. DESIGN: The effects of RRx-001 on normal cells, and ovarian cancer A2780 and UWB1 cells were evaluated with a colony-forming assay. Western blot densitometry was used to measure Nrf2 nuclear translocation in Caco2 cells after exposure to RRx-001. Following incubation with RRx-001, levels of the antioxidant, NQO1, were determined in Caco2 cells by measuring absorbance over 300 min at 440 nm. RRx-001-mediated cytotoxicity in HCT-116 colorectal cancer cells was evaluated with an MTT assay. In addition, the effect of RRx-001 incubation on the protein expression of Nrf2, PARP, cleaved PARP, procaspases 3, 8, and 9, Bcl-2, and Bax in HCT-116 colorectal cells was determined by western blot analysis. RESULTS: RRx-001 is demonstrated to induce Nrf2 in normal tissues, mediating protection, and to downregulate the Nrf2-controlled antiapoptotic target gene, B-cell lymphoma 2 (Bcl-2) in tumors, mediating cytotoxicity. CONCLUSION: Through Nrf2 induction in normal cells and inhibition of Bcl-2 in tumor cells, RRx-001 selectively protects normal cells against lethality in normal cells, but induces apoptosis in tumor cells.
BACKGROUND:RRx-001, a minimally toxic next-generation checkpoint inhibitor that targets myeloid suppressor cells in the tumor microenvironment, has also been shown to protect normal tissues from the cytotoxic effects of chemotherapy and radiation. The following experiments were carried out to determine whether the cytoprotective functions of RRx-001 in normal cells were operative in tumor cells. DESIGN: The effects of RRx-001 on normal cells, and ovarian cancer A2780 and UWB1 cells were evaluated with a colony-forming assay. Western blot densitometry was used to measure Nrf2 nuclear translocation in Caco2 cells after exposure to RRx-001. Following incubation with RRx-001, levels of the antioxidant, NQO1, were determined in Caco2 cells by measuring absorbance over 300 min at 440 nm. RRx-001-mediated cytotoxicity in HCT-116 colorectal cancer cells was evaluated with an MTT assay. In addition, the effect of RRx-001 incubation on the protein expression of Nrf2, PARP, cleaved PARP, procaspases 3, 8, and 9, Bcl-2, and Bax in HCT-116 colorectal cells was determined by western blot analysis. RESULTS:RRx-001 is demonstrated to induce Nrf2 in normal tissues, mediating protection, and to downregulate the Nrf2-controlled antiapoptotic target gene, B-cell lymphoma 2 (Bcl-2) in tumors, mediating cytotoxicity. CONCLUSION: Through Nrf2 induction in normal cells and inhibition of Bcl-2 in tumor cells, RRx-001 selectively protects normal cells against lethality in normal cells, but induces apoptosis in tumor cells.
Authors: Bryan Oronsky; Corey A Carter; Scott Caroen; Curtis Scribner; Arnold Oronsky; Tony R Reid Journal: Oncoimmunology Date: 2020-04-03 Impact factor: 8.110