Abstract
Abstract Purpose: Organic cation transporters (OCTs) have been recently implicated in the uptake and toxicity of oxaliplatin. Peripheral neuropathy is the dose-limiting toxicity of oxaliplatin due to accumulation of platinum in the dorsal root ganglia (DRG) and damage to sensory neurons. This study sought to determine the role of OCTs in the DRG neuronal uptake of oxaliplatin. Experimental Design: [14C] Oxaliplatin uptake and cytotoxicity in HEK/rOctn1, HEK/rOctn2, HEK/hOCTN1, HEK/hOCTN2, and primary culture of DRG neurons was determined to evaluate the role of Octn1 and Octn2 in oxaliplatin transport and neurotoxicity. mRNA, protein and functional expression of organic cation transporters in rat lumbar DRG were characterised using RT-PCR, Western blotting and uptake of model OCT substrates [3H] MPP, [14C] TEA, [3H] ergothioneine and [3H] L-carnitine. Results: HEK293 cells over-expressing rOctn1, rOctn2, hOCTN1 and hOCTN2 showed increased uptake and cytotoxicity of oxaliplatin compared to Mock-transfected HEK293 controls, and Octn2-mediated uptake of oxaliplatin was significantly higher than Octn1 in both human and rat. Uptake of ergothioneine mediated by Octn1, and L-carnitine mediated by Octn2, was decreased during oxaliplatin exposure. Rat DRG showed high Octn1 and Octn2 mRNA levels, and uptake of ergothioneine and L-carnitine that was temperature- and sodium-dependent and significantly inhibited by model substrates of Octn1 and Octn2. In contrast, DRG had negligible functional activity and low or undetectable mRNA levels of Oct1, Oct2, and Oct3. [14C] Oxaliplatin uptake by DRG neurons was temperature- and sodium-dependent and inhibited by ergothioneine and L-carnitine. Ergothioneine and L-carnitine uptake by DRG neurons was inhibited in the presence of oxaliplatin. Conclusions: In conclusion, Octn1 and Octn2, but not Oct1, Oct2 or Oct3, are functionally expressed in rat DRG neurons. Oxaliplatin uptake by rat DRG neurons and HEK293 cells was mediated by Octn2 and to lesser extent by Octn1. Supported by Grant-in-Aid for Scientific Research (B) (I. T.), Research Activity Start-up (T. N.), Auckland Medical Research Foundation (Doctoral Scholarship) and Cancer Society of New Zealand (Research Grant). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4391. doi:10.1158/1538-7445.AM2011-4391
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