Restoring DNA repair capacity of cells from three distinct diseases by XPD gene-recombinant adenovirus

The nucleotide excision repair (NER) is one of the major human DNA repair pathways. Defects in one of the proteins that act in this system result in three distinct autosomal recessive syndromes: xeroderma pigmentosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD). TFIIH is a nine-protein complex essential for NER activity, initiation of RNA polymerase II transcription and with a possible role in cell cycle regulation. XPD is part of the TFIIH complex and has a helicase function, unwinding the DNA in the 5' --> 3' direction. Mutations in the XPD gene are found in XP, TTD and XP/CS patients, the latter exhibiting both XP and CS symptoms. Correction of DNA repair defects of these cells by transducing the complementing wild-type gene is one potential strategy for helping these patients. Over the last years, adenovirus vectors have been largely used in gene delivering because of their efficient transduction, high titer, and stability. In this work, we present the construction of a recombinant adenovirus carrying the XPD gene, which is coexpressed with the EGFP reporter gene by an IRES sequence, making it easier to follow cell infection. Infection by this recombinant adenovirus grants full correction of SV40-transformed and primary skin fibroblasts obtained from XP-D, TTD and XP/CS patients.

Complementation of the DNA repair deficiency in human xeroderma pigmentosum group a and C cells by recombinant adenovirus-mediated gene transfer

Nucleotide excision repair (NER) is one of the most versatile DNA repair mechanisms, ensuring the proper functioning and trustworthy transmission of genetic information in all living cells. The phenotypic consequences caused by NER defects in humans are autosomal recessive diseases such as xeroderma pigmentosum (XP). This syndrome is the most sun-sensitive disorder leading to a high frequency of skin cancer. The majority of patients with XP carry mutations in the XPA or XPC genes that encode proteins involved in recognition of DNA damage induced by UV light at the beginning of the NER process. Cells cultured from XPA and XPC patients are hypersensitive to UV light, as a result of malfunctioning DNA repair. So far there is no effective long-term treatment for these patients. Skin cancer prevention can only be achieved by strict avoidance of sunlight exposure or by the use of sunscreen agents. We have constructed recombinant adenoviruses carrying the XPA and XPC genes that were used to infect XP-A and XP-C immortalized and primary fibroblast cell lines. UV survival curves and unscheduled DNA synthesis confirmed complete phenotypic reversion in XP DNA repair deficient cells with no trace of cytotoxicity. Moreover, transgene expression is stable for at least 60 days after infection. This efficient adenovirus gene delivery approach may be an important tool to better understand XP deficiency and the causes of DNA damage induced skin cancer.

An adenovirus vector containing the suicide gene thymidine kinase for a broad application in cancer gene therapy

Treatment of cancer using gene therapy is based on adding a property to the cell leading to its elimination. One possibility is the use of suicide genes that code for enzymes that transform a pro-drug into a cytotoxic product. The most extensively used is the herpes simplex virus thymidine kinase (TK) gene, followed by administration of the antiviral drug ganciclovir (GCV). The choice of the promoter to drive the transcription of a transgene is one of the determinants of a given transfer vector usefulness, as different promoters show different efficiencies depending on the target cell type. In the experiments presented here, we report the construction of a recombinant adenovirus carrying TK gene (Ad-TK) driven by three strong promoters (P CMV IE, SV40 and EN1) and its effectiveness in two cell types. Human HeLa and mouse CCR2 tumor cells were transduced with Ad-TK and efficiently killed after addition of GCV. We could detect two sizes of transcripts of TK gene, one derived from the close together P CMV IE/SV40 promoters and the other from the 1.5 Kb downstream EN1 promoter. The relative amounts of these transcripts were different in each cell type thus indicating a higher flexibility of this system.