Multiple abnormalities in the ultraviolet light response of cultured fibroblasts derived from patients with the basal cell nevus syndrome

Deficient expression of aldehyde dehydrogenase 1A1 is consistent with increased sensitivity of Gorlin syndrome patients to radiation carcinogenesis

Human phenotypes that are highly susceptible to radiation carcinogenesis have been identified. Sensitive phenotypes often display robust regulation of molecular features that modify biological response, which can facilitate identification of the pathways/networks that contribute to pathophysiological outcomes. Here we interrogate primary dermal fibroblasts isolated from Gorlin syndrome patients (GDFs), who display a pronounced inducible tumorigenic response to radiation, in comparison to normal human dermal fibroblasts (NHDFs). Our approach exploits newly developed thiol reactive probes to define changes in protein thiol profiles in live cell studies, which minimizes artifacts associated with cell lysis. Redox probes revealed deficient expression of an apparent 55 kDa protein thiol in GDFs from independent Gorlin syndrome patients, compared with NHDFs. Proteomics tentatively identified this protein as aldehyde dehydrogenase 1A1 (ALDH1A1), a key enzyme regulating retinoic acid synthesis, and ALDH1A1 protein deficiency in GDFs was confirmed by Western blot. A number of additional protein thiol differences in GDFs were identified, including radiation responsive annexin family members and lamin A/C. Collectively, candidates identified in our study have plausible implications for radiation health effects and cancer susceptibility.

Impaired removal of 8-hydroxydeoxyguanosine induced by UVB radiation in naevoid basal cell carcinoma syndrome cells

BACKGROUND

The naevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by tumorigenesis such as multiple basal cell carcinomas, odontogenic keratocysts and developmental abnormalities such as calcified dural folds and rib-anomalies. Recently, it has been shown that ultraviolet (UV) B exposure produced more BCCs in ptch knockout mice than wild mice.

OBJECTIVES

To Investigate the role of UV in development of BCCs in NBCCS, cellular sensitivity to killing by UVB and removal of UVB-induced oxidative DNA damage were examined using fibroblasts derived from patients with NBCCS under physiologically relevant doses of UVB exposure.

PATIENTS AND METHODS

Three patients with NBCCS, a 59-year-old male patient, an 18-year-old boy and a 13-year-old boy were examined by photobiological analysis. Cellular sensitivity to killing by UVB and UVC and removal of oxidative DNA damage caused by UVB were tested using fibroblasts derived from these patients. We measured cellular 8-hydroxydeoxyguanosine (8-OHdG) after UVB exposure up to 24 h after UVB exposure using high-performance liquid chromatography.

RESULTS

All three cell strains derived from the patients with NBCCS were hypersensitive to killing by UVB (D10: 50-70% of normal) but not by UVC. After UVB exposure, the production of 8-OHdG increased dose dependently up to 3200 J m-2 in both NBCCS cells and normal cells. In normal cells, 8-OHdG after UVB exposure returned to its basal level during 24 h, whereas in NBCCS cells the amount of 8-OHdG after 800 J m-2 of UVB exposure did not return to its basal level even after 24 h. The result indicates the removal of 8-OHdG could be impaired in NBCCS cells. Ability in removal of thymine dimers of NBCCS cells was similar to that of normal cells.

CONCLUSIONS

Hypersensitivity to UVB can be one of the diagnostic tools of NBCCS for those whose clinical features have not yet completed. Hypersensitivity to cell killing and the impairment of removal of 8-OHdG after UVB exposure may play some role in developing BCCs and other tumours in NBCCS.

Microsatellite instability at tetranucleotide repeats in skin and bladder cancer

Recently, a novel form of MSI has been described that occurs only at tetranucleotide repeat markers. This has been termed elevated microsatellite instability at selected tetranucleotide repeats (EMAST). EMAST has been related to alterations of the p53 gene, and to the nature of the repeat sequence. We initially tested whether loss of heterozygosity (LOH) at the p53 and the patched (ptch) genes was related to EMAST in a series of 61 non-melanoma skin cancer (NMSC) tumors. We then analysed a series of 57 primary bladder cancers for the presence of EMAST, testing whether this was related to mutation or expression of the p53 gene. In both NMSC and bladder tumors we found a high prevalence of EMAST (75.4 and 43.9%). In NMSC the prevalence of EMAST was higher in tumors that had either p53 or ptch LOH, although the difference was not statistically significant. There was a significant association of extensive EMAST (three or more loci) with mutations in p53 among the bladder cancer tumors, but no indication of elevated EMAST in tumors with abnormal p53 staining without mutation. The association of EMAST with p53 mutation was confined to non-invasive disease. Hence, EMAST likely reflects a particular pattern of somatic events that are interactive with p53 mutation, particularly common in skin cancer and limited to non-invasive disease in bladder cancer.

p53 immunohistochemistry of odontogenic keratocysts in relation to recurrence, basal-cell budding and basal-cell naevus syndrome

Mutation of the p53 tumour suppressor gene can produce a more stable protein that does not inhibit mitosis, accumulates in the nucleus and can then be detected immunohistochemically in many human tumours using antibody CM-1. The protein has also been detected in odontogenic keratocysts. Routinely processed material from 30 odontogenic keratocysts was immunostained with antibody CM-1. Ten were recurrences and five were associated with the basal-cell naevus syndrome (Gorlin-Goltz syndrome). p53 protein was found in 50% (15/30) of the odontogenic keratocysts, in 53.3% (8/15) of non-recurrent cysts, in 40% (4/10) of recurrent cysts and in 60% (3/5) of those associated with the basal-cell naevus syndrome. Staining was weak and speckled and limited to occasional basal and suprabasal cells. There was no statistically significant difference in staining between these groups and no correlation between expression and the presence of satellite cysts, basal-cell budding or islands of odontogenic epithelium. The low levels of expression may represent physiological expression of wild-type p53 protein rather than mutant or complexed p53 protein.

Cyclobutane pyrimidine dimers in UV-DNA induce release of soluble mediators that activate the human immunodeficiency virus promoter

Ultraviolet (UV) irradiation of human cells induced expression of a stably maintained fusion gene consisting of the human immunodeficiency virus long terminal repeat promoter controlling the bacterial chloramphenicol acetyltransferase gene. Two experiments demonstrated that DNA damage can initiate induction: UV induction was greater in DNA repair-deficient cells from a xeroderma pigmentosum patient than in repair-proficient cells, and transfection of UV-irradiated DNA into unirradiated cells activated gene expression. Increased repair of cyclobutane pyrimidine dimers by T4 endonuclease V abrogated viral gene activation, suggesting that dimers in DNA are one signal leading to increased gene expression. This signal was spread from UV-irradiated cells to unirradiated cells by co-cultivation, implicating the release of soluble factors. Irradiation of cells from DNA repair-deficiency diseases resulted in greater release of soluble factors than irradiation of cells from unaffected individuals. These results suggest that UV-induced cyclobutane pyrimidine dimers can activate the human immunodeficiency virus promoter at least in part by a signal-transduction pathway that includes secretion of soluble mediators.

Molecular mechanisms of ultraviolet radiation carcinogenesis

UV radiation is a potent DNA damaging agent and a known inducer of skin cancer in experimental animals. There is excellent scientific evidence to indicate that most non-melanoma human skin cancers are induced by repeated exposure to sunlight. UV radiation is unique in that it induces DNA damage that differs from the lesions induced by any other carcinogen. The prevalence of skin cancer on sun-exposed body sites in individuals with the inherited disorder XP suggests that defective repair of UV-induced DNA damage can lead to cancer induction. Carcinogenesis in the skin, as elsewhere, is a multistep process in which a series of genetic and epigenetic events leads to the emergence of a clone of cells that have escaped normal growth control mechanisms. The principal candidates that are involved in these events are oncogenes and tumor suppressor genes. Oncogenes display a positive effect on transformation, whereas tumor suppressor genes have an essentially negative effect, blocking transformation. Activated ras oncogenes have been identified in human skin cancers. In most cases, the mutations in the ras oncogenes have been localized to pyrimidine-rich sequences, which indicates that these sites are probably the targets for UV-induced DNA damage and subsequent mutation and transformation. The finding that activation of ras oncogenes in benign and self-regressing keratoacanthomas in both humans and in animals indicates that they play a role in the early stages of carcinogenesis (Corominas et al., 1989; Kumar et al., 1990). Since cancers do not arise immediately after exposure to physical or chemical carcinogens, ras oncogenes must remain latent for long periods of time. Tumor growth and progression into the more malignant stages may require additional events involving activation of other oncogenes or deletion of growth suppressor genes. In addition, amplification of proto-oncogenes or other genes may also be involved in tumor induction or progression. In contrast to the few studies that implicate the involvement of oncogenes in UV carcinogenesis, the role of tumor suppressor genes in UV carcinogenesis is unknown. Since cancer-prone individuals, particularly XP patients, lack one or more repair pathways, one can speculate that DNA repair enzymes would confer susceptibility to both spontaneous and environmentally induced cancers. Another potential candidate that can function as a tumor suppressor gene is the normal c-Ha-ras gene. Spandidos and Wilkie (1988) have shown that the normal c-Ha-ras gene can suppress transformation induced by the mutated ras gene.(ABSTRACT TRUNCATED AT 400 WORDS)

Sensitivity of cultured lymphocytes from patients with nevoid basal cell carcinoma syndrome to ultraviolet light and phytohemagglutinin stimulation

DNA repair and replication after in vitro UV irradiation were determined in cultured peripheral blood lymphocytes from 6 patients with nevoid basal cell carcinoma syndrome (NBCCS) and from a group of control donors. DNA repair synthesis (UDS) was measured in unstimulated lymphocytes by incubation with 3H-TdR in the presence of hydroxyurea for 3 and 6 h after UV irradiation (6-48 J/m2). DNA replication was measured in PHA-stimulated lymphocytes, UV-irradiated or mock-irradiated, by incubation with 3H-TdR for 24 h. The effect of the mitogen was followed during 5 days after stimulation by determining the incorporation of 3H-TdR, the increase of cell number, and the mitotic index. NBCCS and control lymphocytes showed equal sensitivity to UV light in terms of UDS and reduced response to PHA. On the contrary, the mitotic index and the number of cells in stimulated cultures were significantly lower in the affected subjects. These data suggest an altered progression along the cell cycle, which could be characteristic of stimulated NBCCS lymphocytes.

Cultured skin keratinocytes from both normal individuals and basal cell naevus syndrome patients are more resistant to gamma-rays and UV light compared with cultured skin fibroblasts

Measurement of colony-forming ability following exposure to gamma-rays was performed on cultured skin keratinocytes and skin fibroblasts obtained from normal individuals, basal cell naevus syndrome patients (BCNS) and ataxia telangiectasia (A-T) patients. The most striking observation was the radiation resistance of 8/8 keratinocyte strains compared with fibroblasts whether from BCNS patients or normals. The single A-T keratinocyte cell strain showed the same radiosensitivity as A-T fibroblast cell strains. The differential survival of keratinocytes and fibroblasts was also observed following exposure to 254 nm UV light. The survival curves of SV40 immortalized keratinocytes and retinoblasts derived from normal individuals or BCNS patients showed large shoulder regions following exposure to gamma-rays or 254 nm UV light. An increased D37 rather than an increased D0 was therefore the feature of such curves. This contrasted with the SV40 immortalized A-T keratinocytes or fibroblasts which showed a minimal shoulder effect and an increased D0. No difference in survival was observed between BCNS and normal cells following exposure to either UV or gamma-rays.