Heat-labile glucose-6-phosphate dehydrogenase in cultured fibroblasts from patients with De Sanctis-Cacchione Syndrome.

The normal senescent fibroblasts in culture accumulate a significantly high proportion of altered enzymes, and the alterations are considered to be the manifestation of ageing in molecular terms. To detect the possible molecular alterations in patients with De Sanctis-Cacchione syndrome, the severest form of xeroderma pigmentosum, in which repair processes to UV light-damaged DNA are defective and the neurologic abnormalities are considered to reflect accelerated ageing, we studied the heat stability of glucose-6-phosphate dehydrogenase (G6PD) in crude extracts of cultured skin fibroblasts. Three patients with the syndrome were the center of our investigation. Even at early passage in culture the heat-labile portion of G6PD was increased in the cells from patients in comparison to normal controls. The life span of the cells in culture from patients was not reduced below normal age-matched controls, and no appreciable senescent appearance was observed. The increase in the heat-labile portion of G6PD from cells of DeSanctis-Cacchione syndrome patients to reflect that defective repair of DNA damage occurs, rather than being a direct result of ageing of cultured cells.