Abstract
BackgroundThe metabolic inhibitor 3-bromopyruvate (3-BrPA) is a promising anti-cancer alkylating agent, shown to inhibit growth of some colorectal carcinoma with KRAS mutation. Recently, we demonstrated increased resistance to 3-BrPA in wt p53 tumor cells compared to those with p53 silencing or mutation. Since hypoxic microenvironments select for tumor cells with diminished therapeutic response, we investigated whether hypoxia unequally increases resistance to 3-BrPA in wt p53 MelJuso melanoma harbouring (Q61L)-mutant NRAS and wt BRAF, C8161 melanoma with (G12D)-mutant KRAS (G464E)-mutant BRAF, and A549 lung carcinoma with a KRAS (G12S)-mutation. Since hypoxia increases the toxicity of the p53 activator, Prima-1 against breast cancer cells irrespective of their p53 status, we also investigated whether Prima-1 reversed hypoxic resistance to 3-BrPA.ResultsIn contrast to the high susceptibility of hypoxic mutant NRAS MelJuso cells to 3-BrPA or Prima-1, KRAS mutant C8161 and A549 cells revealed hypoxic resistance to 3-BrPA counteracted by Prima-1. In A549 cells, Prima-1 increased p21CDKN1mRNA, and reciprocally inhibited mRNA expression of the SLC2A1-GLUT1 glucose transporter-1 and ALDH1A1, gene linked to detoxification and stem cell properties. 3-BrPA lowered CAIX and VEGF mRNA expression. Death from joint Prima-1 and 3-BrPA treatment in KRAS mutant A549 and C8161 cells seemed mediated by potentiating oxidative stress, since it was antagonized by the anti-oxidant and glutathione precursor N-acetylcysteine.ConclusionsThis report is the first to show that Prima-1 kills hypoxic wt p53 KRAS-mutant cells resistant to 3-BrPA, partly by decreasing GLUT-1 expression and exacerbating pro-oxidant stress.
Highlights
The metabolic inhibitor 3-bromopyruvate (3-BrPA) is a promising anti-cancer alkylating agent, shown to inhibit growth of some colorectal carcinoma with KRAS mutation
Oncogenic KRAS mutations increase Reactive oxygen species (ROS) levels [14] and overexpression of GLUT1 in lung carcinomas [15]. This glucose receptor 1 (SLC2A1-GLUT1) transports glucose which has a role in antioxidant defense [16], since it is the first substrate in the pentose phosphate pathway generating NADPH, capable of donating electrons to antioxidant pathways to attenuate excessive oxidative stress [14,15,16]
Since basal oxidative stress is increased by mutant p53 [13] or mutant KRAS [14], and can be further exacerbated by 3-BrPA [25] or Prima-1 [12], we showed for the first time that the latter 2 agents cooperate to hyperinduce ROS under aerobic conditions (Fig. 2) and counteract hypoxic resistance to 3-BrPA using physiological 5 mM glucose levels
Summary
The metabolic inhibitor 3-bromopyruvate (3-BrPA) is a promising anti-cancer alkylating agent, shown to inhibit growth of some colorectal carcinoma with KRAS mutation. Oncogenic KRAS mutations increase ROS levels [14] and overexpression of GLUT1 in lung carcinomas [15] This glucose receptor 1 (SLC2A1-GLUT1) transports glucose which has a role in antioxidant defense [16], since it is the first substrate in the pentose phosphate pathway generating NADPH, capable of donating electrons to antioxidant pathways to attenuate excessive oxidative stress [14,15,16]. MQ can target cells irrespective of p53 by inhibiting thioredoxin reductase I and converting it to a pro-oxidant NADPH oxidase to further increase oxidative stress [6, 12] Another potent prooxidant is 3-bromopyruvate (3-BrPA), a metabolic competitor of pyruvate [17], and an alkylating agent capable of depleting ATP and increasing metabolic stress by generating free radicals [24, 25]. Another potent prooxidant is 3-bromopyruvate (3-BrPA), a metabolic competitor of pyruvate [17], and an alkylating agent capable of depleting ATP and increasing metabolic stress by generating free radicals [24, 25]. 3-BrPA preferentially suppressed the growth of some colorectal carcinoma cells with KRAS or BRAF mutations which survived glucose starvation [26]
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