title: A mechanistic evaluation of the Syrian hamster embryo cell transformation assay (pH 6.7) and molecular events leading to senescence bypass in SHE cells.
abstract: The implementation of the Syrian hamster embryo cell transformation assay (SHE CTA) into test batteries and its relevance in predicting carcinogenicity has been long debated. Despite prevalidation studies to ensure reproducibility and minimise the subjective nature of the assay's endpoint, an underlying mechanistic and molecular basis supporting morphological transformation (MT) as an indicator of carcinogenesis is still missing. We found that only 20% of benzo(a)pyrene-induced MT clones immortalised suggesting that, alone, the MT phenotype is insufficient for senescence bypass. From a total of 12 B(a)P- immortalised MT lines, inactivating p53 mutations were identified in 30% of clones, and the majority of these were consistent with the potent carcinogen's mode of action. Expression of p16 was commonly silenced or markedly reduced with extensive promoter methylation observed in 45% of MT clones, while Bmi1 was strongly upregulated in 25% of clones. In instances where secondary events to MT appeared necessary for senescence bypass, as evidenced by a transient cellular crisis, clonal growth correlated with monoallelic deletion of the CDKN2A/B locus. The findings further implicate the importance of p16 and p53 pathways in regulating senescence while providing a molecular evaluation of SHE CTA -derived variant MT clones induced by benzo(a)pyrene.
authors.affiliation: Institute of Cancer Genetics and Pharmacogenomics, Brunel University London, Kingston Lane, Uxbridge, Middlesex UB8 3PH, United Kingdom. Electronic address: jessica.pickles@ucl.ac.uk.
authors.forename: Jessica C
authors.initials: JC
authors.lastname: Pickles
authors.affiliation: BioReliance Corporation, 14920 Broschart Road, Rockville, MD 20850-3349, USA.
authors.forename: Kamala
authors.initials: K
authors.lastname: Pant
authors.affiliation: Institute of Cancer Genetics and Pharmacogenomics, Brunel University London, Kingston Lane, Uxbridge, Middlesex UB8 3PH, United Kingdom.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Mcginty
authors.affiliation: Institute of Cancer Genetics and Pharmacogenomics, Brunel University London, Kingston Lane, Uxbridge, Middlesex UB8 3PH, United Kingdom.
authors.forename: Hemad
authors.initials: H
authors.lastname: Yasaei
authors.affiliation: Institute of Cancer Genetics and Pharmacogenomics, Brunel University London, Kingston Lane, Uxbridge, Middlesex UB8 3PH, United Kingdom.
authors.forename: Terry
authors.initials: T
authors.lastname: Roberts
authors.affiliation: Unilever, Safety and Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedford MK44 1LQ, United Kingdom.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Scott
authors.affiliation: Institute of Cancer Genetics and Pharmacogenomics, Brunel University London, Kingston Lane, Uxbridge, Middlesex UB8 3PH, United Kingdom. Electronic address: robert.newbold@brunel.ac.uk.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Newbold
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000633:toxicity*; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D006224:Cricetinae; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D019175:DNA Methylation / Q000187:drug effects / Q000235:genetics; D008647:Mesocricetus
chemical_list: D002273:Carcinogens; D019941:Cyclin-Dependent Kinase Inhibitor p16
keywords: Cell transformation assay; Morphological transformation; Senescence bypass; Syrian hamster; p16/CDKN2A