XERODERMA PIGMENTOSUM CELL SUSCEPTIBILITY TO SV40 VIRUS TRANSFORMATION: LACK OF EFFECT OF LOW DOSAGE ULTRAVIOLET RADIATION IN ENHANCING VIRAL-INDUCED TRANSFORMATION.

SV40 is an oncogenic DNA virus capable of both tumorigenesis in vivo and of transformation in vitro. i.e., loss of contact inhibition and subsequent overgrowth of otherwise contact-inhibited cells. Marked increased susceptibility to SV40 transformation of skin fibroblasts is present in Down's syndrome and Fanconi's anemia, both of which are associated with a high incidence of neoplasia. The question arose as to whether skin fibroblasts from patients with xeroderma pigmentosum (XP) which show an otherwise normal incidence of SV40-induced transformation, might, on exposure to UV radiation, show enhanced transformation. Can the biologic defect in relation to carcinogenesis in XP be enhanced susceptibility to the triggering by sun exposure of viral oncogenesis? Both XP and normal skin fibroblasts were exposed to low-dosage UV radiation immediately prior to infection with SV40 and the incidence of T-antigen, an early marker of SV40 infection, and of gross transformation, the morphologic late end point in vitro, were noted. No increase in transformation either absolute or relative to cell survival post irradiation was seen. In no instance was transformation seen in noninfected, but irradiated, control cultures. [ABSTRACT FROM AUTHOR]