Sotorasib, a KRAS-G12C Inhibitor, Induces Chemoresistance by Activating Human Pregnane Xenobiotic Receptor

Abstract

<b>Abstract ID 23343</b> <b>Poster Board 33</b> During multidrug combination chemotherapy, activation of the nuclear receptor, human pregnane xenobiotic receptor (hPXR), has been shown to play a role in the development chemoresistance. Mechanistically, this could occur by upregulation of agonists-induced hPXR-regulated expression of drug-metabolizing enzymes and drug-efflux pumps, such as cytochrome P450 3A4 (CYP3A4) and multidrug resistance protein 1 (MDR1). CYP3A4 &amp; MDR1, contribute to the metabolism and disposition of over 50% of clinical drugs. Therefore, during multidrug chemotherapy, drug induction of hPXR-regulated CYP3A4 &amp; MDR1 leads to increased drug metabolism &amp; transport, affecting the therapeutic response of co-administered drugs, leading to chemoresistance. Sotorasib (SOT) is the first FDA approved KRAS-G12C inhibitor for the treatment of advanced non-small cell lung cancer with the KRAS-G12C mutation. It is currently unknown whether SOT can activate hPXR and upregulate hPXR target gene expression, leading to chemoresistance. We therefore sought to determine whether SOT, at its therapeutically relevant concentrations, could act as an hPXR agonist and upregulate hPXR-mediated regulation of CYP3A4 &amp; MDR1 in human hepatocytes, HepG2 liver cancer cells &amp; LS180 colon cancer cells, and induce chemoresistance in LS180 cells. Reporter gene assays were conducted to determine the transactivation of CYP3A4 promoter activity by the nuclear receptors. Cell viability assays were performed to assess cytotoxicity. RT-qPCR assays were conducted to study CYP3A4 &amp; MDR1 gene expression. Rhodamine-123 intracellular accumulation assays were performed to examine MDR1 function. Competitive ligand binding assays were performed to determine the ability of SOT to bind to hPXR. SOT, at its therapeutically relevant concentrations, induced hPXR transactivation of CYP3A4 promoter activity, suggesting that SOT can induce hPXR target gene expression. Indeed, SOT induced endogenous gene expression of hPXR target genes: CYP3A4 &amp; MDR1. SOT decreased intracellular accumulation of MDR1 substrate rhodamine-123, suggesting that SOT induces MDR1 functional expression. SOT was able to bind to the ligand-binding domain of hPXR, suggesting that SOT can directly interact with hPXR to induce hPXR target gene expression. The inductive effect of SOT on CYP3A4 promoter activity as well as endogenous CYP3A4 &amp; MDR1 gene expression was inhibited by a specific hPXR antagonist SPA70. These findings suggest that SOT induces hPXR target genes by directly activating hPXR. Moreover, while SOT activated hPXR, it failed to activate the mouse PXR and another related nuclear receptor human constitutive androstane receptor in the reporter gene assays, indicating that the effects of SOT are both species and nuclear receptor dependent. Notably, SOT decreased the sensitivity of LS180 cells to both irinotecan and its active metabolite SN-38, suggesting that SOT can induce chemoresistance by activating hPXR. Taken together, our results suggest that SOT induces chemoresistance by activating hPXR and inducing CYP3A4 &amp; MDR1. The inductive effects of SOT on CYP3A4 &amp; MDR1 expression caution the use of SOT in conjunction with other medications that are metabolized and transported via CYP3A4 &amp; MDR1, as this can lead to chemoresistance. Acknowledgments: This study was supported by Auburn University Animal Health &amp; Disease Research Program to S.R.P.