ABSTRACT
Basal cell carcinoma of the skin is the most common type of cancer in humans. The majority of these tumors displays aberrant activation of the SONIC HEDGEHOG (SHH)/PATCHED pathway, triggered by mutations in the PATCHED tumor suppressor gene, which encodes a transmembrane receptor of SHH. In this study, we took advantage of the natural genotype (PATCHED(+/-)) of healthy keratinocytes expanded from patients with the nevoid basal cell carcinoma or Gorlin syndrome to mimic heterozygous somatic mutations thought to occur in the PATCHED gene early upon basal cell carcinoma development in the general population. PATCHED(+/-) epidermis developed on a dermal equivalent containing wild-type (WT) PATCHED(+/+) fibroblasts exhibited striking invasiveness and hyperproliferation, as well as marked differentiation impairment. Deciphering the phenotype of PATCHED(+/-) keratinocytes revealed slight increases of the transcriptional activators GLI1 and GLI2-the latter known to provoke basal cell carcinoma-like tumors when overexpressed in transgenic mice. PATCHED(+/-) keratinocytes also showed a substantial increase of the cell cycle regulator cyclin D1. These data show for the first time the physiological impact of constitutive heterozygous PATCHED mutations in primary human keratinocytes and strongly argue for a yet elusive mechanism of haploinsufficiency leading to cancer proneness.
Subject(s)
Carcinoma, Basal Cell/genetics , Mutation , Receptors, Cell Surface/genetics , Skin Neoplasms/genetics , Skin/pathology , Base Sequence , Carcinoma, Basal Cell/metabolism , Carcinoma, Basal Cell/pathology , Cell Transformation, Neoplastic/genetics , Cells, Cultured , DNA Mutational Analysis , Female , Gene Expression Regulation, Neoplastic , Genes, Tumor Suppressor/physiology , Genetic Predisposition to Disease , Heterozygote , Humans , Keratinocytes/metabolism , Keratinocytes/pathology , Male , Middle Aged , Models, Biological , Mutation/physiology , Organ Culture Techniques , Patched Receptors , Receptors, Cell Surface/metabolism , Skin/metabolism , Skin Neoplasms/metabolism , Skin Neoplasms/pathologyABSTRACT
Nucleotide excision repair (NER) of DNA-lesions is the most versatile DNA repair mechanism involved in genome maintenance, cell and organismal preservation. Deciphering the stepwise mechanism of NER has mostly relied on cells from rare patients presenting photosensitive, recessively inherited genetic disorders such as xeroderma pigmentosum (XP), trichothiodystrophy (TTD) and Cockayne (CS) syndromes. Cells from these patients share various extents of impaired capacity of repairing UV-induced DNA lesions (cyclobutane pyrimidine dimers, 6-4 pyrimidine-pyrimidone photo products) located either in transcribed DNA strands or in inactive DNA. We review here the essentials of NER actors and how impairment of their activity may lead to distinct and characteristic human disorders whose presentation may be limited to developmental trait (TTD; CS), or cumulate with cancer susceptibility toward genotoxic aggressions, most notably short wavelength ultraviolets.
Subject(s)
DNA Repair , Genetic Diseases, Inborn/genetics , Animals , Cockayne Syndrome/genetics , DNA/genetics , DNA Damage , Dimerization , Genetic Complementation Test , Genome , Humans , Models, Genetic , Trichothiodystrophy Syndromes/genetics , Ultraviolet Rays , Xeroderma Pigmentosum/geneticsABSTRACT
DNA polymerase beta, one of the most inaccurate DNA synthesizing enzymes, has been shown to confer genetic instability when up-regulated in cells, a situation found in several human cancers. Here, we demonstrated that enhanced activity and expression of this enzyme occur in the human ovarian tumor 2008/C13*5.25 cells, which are resistant to the antitumor agent cisplatin and hypersensitive to 6-thioguanine. We found that translesion synthesis across platinated DNA crosslinks as well as increased incorporation into DNA of 6-thioguanine took place in the 2008/C13*5.25 cells compared to the parental 2008 cells. Such features being molecular signatures of DNA polymerase beta, these findings suggest that deregulation of its expression in cancer cells may contribute to the modulation of the response to antitumor treatments and therefore to tumor progression.