title: The absence of Brm exacerbates photocarcinogenesis.
abstract: Brm is an ATPase subunit of the SWI/SNF chromatin-remodelling complex. Previously, we identified a novel hotspot mutation in Brm in human skin cancer, which is caused by exposure to ultraviolet radiation (UVR). As SWI/SNF is involved in DNA repair, we investigated whether Brm-/- mice had enhanced photocarcinogenesis. P53+/- and Brm-/-p53+/- mice were also examined as the p53 tumor suppressor gene is mutated early during human skin carcinogenesis. Mice were exposed to a low-dose irradiation protocol that caused few skin tumors in wild-type mice. Brm-/- mice with both p53 alleles intact had an increased incidence of skin and ocular tumors compared to Brm+/+p53+/+ controls. Brm loss in p53+/- mice did not further enhance skin or ocular cancer incidence beyond the increased photocarcinogenesis in p53+/- mice. However, the skin tumors that arose early in Brm-/- p53+/- mice had a higher growth rate. Brm-/- did not prevent UVR-induced apoptotic sunburn cell formation, which is a protective response. Unexpectedly, Brm-/- inhibited UVR-induced immunosuppression, which would be predicted to reduce rather than enhance photocarcinogenesis. In conclusion, the absence of Brm increased skin and ocular photocarcinogenesis. Even when one allele of p53 is lost, Brm has additional tumor suppressing capability.
authors: Discipline of Dermatology, Bosch Institute, Sydney Medical School, University of Sydney, Sydney, NSW, Australia. gary.halliday@sydney.edu.au
authors: Gary M
authors: GM
authors: Halliday
authors: Yue
authors: Y
authors: Zhou
authors: Paul W
authors: PW
authors: Sou
authors: Xiao X J
authors: XX
authors: Huang
authors: Sabita
authors: S
authors: Rana
authors: Matthew J
authors: MJ
authors: Bugeja
authors: Nicole
authors: N
authors: Painter
authors: Richard A
authors: RA
authors: Scolyer
authors: Christian
authors: C
authors: Muchardt
authors: Nick
authors: N
authors: Di Girolamo
authors: J Guy
authors: JG
authors: Lyons
mesh_terms: D000818:Animals; D017209:Apoptosis; D004307:Dose-Response Relationship, Radiation; D005134:Eye Neoplasms / Q000235:genetics / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D015994:Incidence; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009381:Neoplasms, Radiation-Induced / Q000235:genetics / Q000473:pathology / Q000503:physiopathology*; D012878:Skin Neoplasms / Q000235:genetics / Q000473:pathology / Q000503:physiopathology*; D014157:Transcription Factors / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: C499503:Smarca2 protein, mouse; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53