Functional Retroviral Vector for Gene Therapy of Xeroderma Pigmentosum Group D Patients

Abstract

Xeroderma pigmentosum (XP) is an autosomal recessive genetic disorder characterized by an increased frequency of skin cancer following minimal sunlight exposure. Cells isolated from XP patients are also hypersensitive to UV rays and UV-like chemicals. This sensitivity is directly related to a defect in the early steps of nucleotide excision repair (NER) of damaged DNA. No efficient treatment is available for this disease and skin cancer prevention can only be achieved by strict avoidance of sunlight exposure. Thus, we are developing a model for gene therapy in XP, particularly for patients belonging to group D. We report here the construction of a retroviral vector (LXPDSN) containing the XPD (ERCC2) cDNA, which fully complements the DNA repair deficiency of primary skin fibroblasts. Efficient integration, mRNA synthesis, and protein expression of the XPD gene were obtained in all LXPDSN-transduced XP-D fibroblasts tested. Full correction of the DNA repair defect was observed with all DNA repair assays used, such as an increased survival after UV-radiation of the transduced cells, a normal level of DNA repair synthesis (UDS), and the reactivation of a UV-irradiated reporter vector. This retroviral vector will be used to modify keratinocytes genetically to produce repair proficient reconstituted skin for engraftment to XP patients.

Overview summary

The first step toward gene therapy for the DNA repair disease xeroderma pigmentosum (XP) has been established by Carreau et al. They report the construction of a retroviral vector containing one of the DNA repair genes, the XP complementation group D previously known as ERCC2. Gene transfer was carried out on fibroblasts from two XP complementation group D patients referred to their laboratory. Complete phenotypic correction of the DNA repair defect in cells from both patients was achieved after the introduction of a functional copy of the XPD gene. This vector will then be used to modify keratinocytes to produce repair proficient reconstituted skin for engraftment at the most exposed areas. In this view, this study represents the first step toward long-term skin cancer therapy for XP patients.