Utilization of Reactive Oxygen Species Targeted Therapy to Prolong the Efficacy of BRAF Inhibitors in Melanoma

Abstract

BRAF mutations occur in about 50% of melanoma patients. FDA approved BRAF and MEK inhibitors have improved the prognosis of patients with BRAF mutations. However, all responders develop resistance typically within one year of treatment. Recent observations demonstrate that BRAF inhibitors induce reactive oxygen species (ROS) in melanoma cells. A100, identified from a library screen, is a ROS-activated prodrug that self-cyclizes into a stable bicyclic ring and causes DNA double strand breaks. We proposed to examine if ROS activated therapy will inhibit tumor growth and evade resistance to BRAF inhibitors. In this study, the BRAF inhibitor dabrafenib was used to generate resistant cell lines (A375DR, SK-MEL-24DR and WM-115DR). Flow cytometry experiments showed that ROS levels are increased in these dabrafenib-resistant cells as compared to parental cells, assessed by both the H2DCFDA and MitoSOX assays. Furthermore, we observed that resistant cells had increased levels of the mitochondrial enzymes SOD2 and PRDX1, which function to reduce ROS levels in the mitochondria. We found that A100 sensitized the resistant melanoma cells to dabrafenib and induced DNA damage. Co-treatment of both A100 and dabrafenib significantly suppressed in vitro cell proliferation and three- dimensional (3D) matrigel growth. This study suggests that the combination of A100 with a BRAF inhibitor could be a potential strategy to treat melanoma patients with BRAF mutations.

Disruption of Redox Balance Enhances the Effects of BRAF-inhibition in Melanoma Cells

“…This increased dependence could present a therapeutic opportunity in melanomas. Indeed, our own results and recent reports inform that redox modulation could be a viable strategy to improve the treatment outcomes (Bauer et al, 2017;Cesi et al, 2017;Corazao-Rozas et al, 2013;Fruehauf and Trapp, 2008;Gorrini et al, 2013;Yuan et al, 2018) .…”

“…Indeed, we show that the disruption of this redox buffer improves the outcomes of targeted therapies. In summary, our findings suggest that modulation of cancer antioxidant defense could be exploited to augment the benefits of existing therapies in melanoma (Khamari et al, 2018;Yuan et al, 2018) . This strategy may extend beyond melanoma, as antioxidant pathways have been implicated in tumor progression, and drug resistance (Harris et al, 2015;Ji et al, 2018;Sarmiento-Salinas et al, 2019) .…”

Mechanisms of Acquired BRAF Inhibitor Resistance in Melanoma: A Systematic Review

“…A considerable number of preclinical studies are investigating other novel targets for overcoming BRAF inhibitor resistance. These include combining BRAF and/or MEK inhibitors with inhibitors of pre-mRNA splicing (to counteract resistance caused by BRAF splicing) [ 251 ], BH3-mimetics [ 252 , 253 ], BCL2 inhibitors [ 254 ], mitochondrial-targeted agents [ 255 , 256 ], inhibitors of p90 ribosomal S6 kinases [ 257 , 258 ], pro-caspase activating compounds [ 259 ], Rho kinase 1 (ROCK1) inhibitors [ 260 ], protein kinase Cδ inhibitors [ 261 ], tubulin inhibitors [ 262 ], ErbB2 or ErbB3 inhibitors [ 222 , 263 , 264 ], activators of the liver-X nuclear hormone receptor [ 265 ], an antibody conjugate targeting the endothelin B receptor [ 266 ], monoclonal antibodies against chondroitin sulfate proteoglycan 4 [ 267 ], inhibitors of sterol regulator element binding protein I (SREBP-1) [ 268 ], copper chelators [ 269 ], polo-like 3 kinase inhibitors (including in models of BRAF + MEK inhibitor resistance) [ 270 , 271 ], anti-nodal antibodies [ 272 ], PAK1 inhibitors [ 273 ], GLI1/2 inhibitors [ 274 ], inhibitors of IQ motif-containing GTPase activating protein 1 (IQGAP1) [ 275 ], serotonin agonists [ 276 ], CK2 inhibitors [ 277 ], p53 activators [ 278 ], metformin [ 279 ], statins [ 280 ], non-steroidal anti-inflammatory drugs [ 281 ], mibefradil [ 282 ], hydroxychloroquine (an autophagy inhibitor) [ 83 ], and A100 (a reactive oxygen species-activated prodrug) [ 283 ].…”

Current Advances in the Treatment of BRAF-Mutant Melanoma

“…Cell damage and cytotoxicity occurs through the alkylation of DNA or cellular proteins. A100 sensitizes dabrafenib-resistant melanoma cells to BRAF protein kinase inhibitors [233]. A100, in the presence of high ROS levels, can self-cyclize into a bicyclic ring and cause DNA double strand breaks in cancer cells [234].…”