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Statistical analysis of rodent gene expression changes were conducted as part of the comprehensive toxicological assessment of HFO-1234yf. This was not a guideline study, was not GLP compliant, and is not accepted as a validated method by the regulatory authorities; however, it was conducted to provide additional information. Potential gene expression changes in liver, kidney and lung tissue were assessed following exposure of female B6C3F1 mice and male F344 rats to levels of 10000 and 50000 ppm HFO-1234yf 6 hrs/day, 5 days/wk for 13 weeks. The assessment was based on the results from a comparison of the responses seen with HFO-1234yf to both positive (tetrafluoroethylene, 1-amino-2,4-dibromoanthraquinone, and Tris(2,3-dibromopropyl)phosphate) and negative (trichlorofluoromethane, iodoform, tetrafluoroethane and N-(1-naphthyl)ethylenediamine dihydrochloride) controls. Vehicle controls were also included. In addition histopathological examination of selected tissues was conducted. 

Statistical classification analysis predicted HFO-1234yf (2,3,3,3-tetrafluoropropene) to be noncarcinogenic in both female mouse liver and male rat kidney, and carcinogenic in the female mouse lung. These findings had a statistical probability of selecting true negatives of 100% for kidney, 99.2% for liver and 83% for lung. The probability for a true positive being identified was 90% for the kidney, 97.2% for the liver and only 71.3% for the lung.

No dose response relationship with respect to changes in gene expression was observed. Furthermore, as only a limited number of genes were altered, it was concluded that for the female mouse lung, the number of genes altered was too small to perform a meaningful gene ontology enrichment analysis. No treatment related histopathological lesions were observed in the liver or kidney and only 1/10 mice in both exposure groups showed mild irritation in the lung. The weight of evidence suggests that HFO-1234yf is not likely to be carcinogenic. This conclusion is supported by the lack of mutagenic activity in all mammalian in vivo genetic toxicity studies, the lack of significant metabolic activity, the lack of systemic toxicity and the lack of significant lesions in the livers, kidneys and lungs in any of the studies.