Detection of genotoxic and non-genotoxic renal carcinogens in vitro in NRK-52E cells using a transcriptomics approach

Abstract

There is a need to develop quick, cheap, sensitive and specific methods to detect the carcinogenic potential of chemicals. Currently there 10 is no in vitro model system for reliable detection of non-genotoxic carcinogens (NGTX) and current tests for detection of genotoxic carcinogens (GTX) can have low specificity. A transcriptomics approach holds promise and a few studies have utilised this technique. However, the majority of these studies have examined liver carcinogens with little work on renal carcinogens which may act via renalspecific NGTX mechanisms. In this study the normal rat renal cell line (NRK-52E) was exposed to sub-toxic concentrations of selected rat renal carcinogens and non-carcinogens (NC) for 6h, 24h and 72h. Renal carcinogens were classified based on their presumed mode of 15 action into GTX and NGTX classes. A whole-genome transcriptomics approach was used to determined genes and pathways as potential signatures for GTX, NGTX and those common to both carcinogenic events in vitro. For some of the GTX compounds an S9 drug metabolising system was included to aid pro-carcinogen activation. Only three genes were deregulated after carcinogen (GTX + NGTX) exposure, one Mdm2 with a detection rate of 67%, and p21 and Cd55 with a detection rate of 56%. However, examination of enriched pathways showed that 3 out of 4 NGTX carcinogens and 4 out of 5 GTX carcinogens were related to known pathways involved in 20 carcinogenesis giving a detection rate of 78%. In contrast, none of the NC chemicals induced any of the above genes or well-established carcinogenic pathways. Additionally, five genes (Lingo1, Hmox1, Ssu72, Lyrm and Usp9x) were commonly altered with 3 out of 4 NGTX carcinogens but not with NC or GTX carcinogens. However, there was no clear separation of GTX and NGTX carcinogens using pathway analysis with several pathways being common to both classes. The findings presented here indicate that the NRK-52E cell line has the potential to detect carcinogenic chemicals, although a much larger number of chemicals need to be used to confirm these 25 findings.

Risk assessment of ochratoxin A in food

“…The authors considered this as evidence of a non-genotoxic MoA. Bloch et al (2012) attempted to distinguish between genotoxic and non-genotoxic renal carcinogens based on their profile of alteration of gene expression in NRK-52E cells, using OTA to represent the non-genotoxic class of carcinogen. However, several pathways were common to both genotoxic and non-genotoxic categories making distinction not possible.…”

Transcriptomic alterations induced by Monuron in rat and human renal proximal tubule cells in vitro and comparison to rat renal-cortex in vivo

“…5 We found that MON at 250 μM (IC 10 at 72 h in rat renal cells) did not induce micronucleus formation. 11 However, studies in Chinese hamster ovary (CHO) cells noted a small increase in chromosome aberrations, which were markedly increased in the presence of Aroclorinduced rat liver S9, indicating MON-induced chromosome aberrations, albeit at a concentration of 1.3 mg ml −1 (6.55 mM). 5 MON also caused transformation in Syrian hamster embryo cells in the absence of metabolic acti-vation.…”