Abstract 5471: Identification of OAT1/OAT3 as contributors to cisplatin nephrotoxicity

Cisplatin is among the most widely used anticancer drugs and known to cause dose-limiting nephrotoxicity. We previously reported that renal organic cation transporters (OCT2 in humans, Oct1/Oct2 in mice) are involved in the etiology of this side effect (Filipski et al, CPT 2009), but the tubular damage is not completely abolished in mice deficient of Oct1 and Oct2 (Sprowl et al, CCR 2014). Since probenecid and furosemide, inhibitors of organic anion transporters OAT1 and OAT3, are known to provide partial protection against cisplatin nephrotoxicity in mice, we evaluated the comparative excretion and nephrotoxicity of cisplatin in mice with and without the Oat1 [Oat1(-/-) mice] and Oat3 genes [Oat3(-/-) mice]. Following a single cisplatin dose of 30 mg/kg, we found that the rate and extent of the cumulative percentage of the dose recovered in urine was impaired in Oat-deficient mice compared with age-matched wild-type mice. Blood urea nitrogen and creatinine, markers of acute renal tubular necrosis, were significantly increased within 3 days after cisplatin administration in wild-type mice but not in Oat1(-/-) or Oat3(-/-) mice. The lesions were characterized by dilated tubules filled with necrotic tubular epithelial cells, cellular debris and proteinaceous casts, whereas the glomeruli, which do not express Oat1 or Oat3, were histologically normal. Previous studies have indicated that OAT1 and OAT3 can transport mercapturic acids, negatively charged N-acetylcysteine S-conjugates formed from the coupling of cysteine with endogenous or exogenous compounds. The existence of a mercapturic acid metabolite of cisplatin (NAC-1) that acts as a precursor of a nephrotoxic and reactive thiol led to our hypothesis that this conjugate might be a transported substrate of OAT1 and/or OAT3 and is responsible for the OCT2-independent mechanism leading to renal injury. To obtain support for this mechanism, we confirmed that NAC-1 preferentially accumulates in HEK293 cells engineered to overexpress OAT1 or OAT3 compared with control cells and that this process is sensitive to inhibition by probenecid. Based on the ability of several tyrosine kinase inhibitors (TKIs) to potently inhibit several transporters of the SLC22A family, including OCT2 (Sprowl et al, ENA 2012), we next evaluated the possibility that some of these same agents may also affect OAT1 and/or OAT3 function in vitro using the prototypical substrates p-aminohippuric acid and estrone-3-sulfate, respectively. Of 23 TKIs evaluated, we found that only nilotinib was able to potently inhibit OCT2, OAT1, and OAT3, without being itself a transported substrate and without influencing cisplatin plasma levels and cytotoxicity against cancer cell lines with detectable levels of OCT2. Collectively, this study identified OAT1/OAT3 as a modulator of cisplatin toxicity, and we expect that nilotinib could be exploited as a transporter inhibitor to alleviate these side effects. Citation Format: Shuiying Hu, Navjotsingh Pabla, Laura J. Janke, Lie Li, Aksana Vasilyeva, Jason A. Sprowl, Alex Sparreboom. Identification of OAT1/OAT3 as contributors to cisplatin nephrotoxicity. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5471. doi:10.1158/1538-7445.AM2015-5471