The role of sunlight and DNA repair in melanoma and nonmelanoma skin cancer. The xeroderma pigmentosum paradigm.

BACKGROUND AND DESIGN: The frequency of melanoma and nonmelanoma skin cancer is increasing rapidly in the United States. However, the linkage of these cancers to sun exposure has been questioned because of differences in anatomic site distribution. To obtain insights into the development of these skin cancers, we examined reports of 132 patients with xeroderma pigmentosum (XP), an inherited cancer-prone, DNA repair-deficient disorder with marked clinical and laboratory UV hypersensitivity. RESULTS: Malignant skin neoplasms were present in 70% of the patients with XP at a median age of 8 years, which is 50 years earlier than in the US white population. Fifty-seven percent of the patients had basal cell or squamous cell carcinoma, and 22% had melanoma. The frequency of melanomas, like the frequency of nonmelanoma skin cancers (basal cell and squamous cell carcinomas), anterior eye cancers, and tongue cancers, but unlike that of internal neoplasms, was increased 1000-fold or more in patients with XP who were younger than 20 years. As in the general population, the anatomic distribution of melanomas was different from that of nonmelanomas in the patients with XP. CONCLUSIONS: These data suggest that (1) DNA repair plays a major role in the prevention of cutaneous cancers in the general population and (2) sunlight exposure is responsible for the induction of melanoma as well as nonmelanoma skin cancer in patients with XP, although acting by different mechanisms for the two types of skin cancer.

Abnormally low UV-induced unscheduled DNA synthesis in cells from a patient with hydroa vacciniforme.

Skin fibroblasts from a patient with the photosensitive disorder hydroa vacciniforme were tested in vitro for DNA repair capacity. The rate of ultraviolet light (254 nm)-induced unscheduled DNA synthesis (UDS) in these fibroblasts was found to be 51-59% of the rate found in 4 normal fibroblasts strains. The patient had none of the clinical signs of the classic DNA deficient disease, xeroderma pigmentosum.

A correlation between aging and DNA repair in human epidermal cells.

Ultraviolet-induced unscheduled DNA synthesis (i.e. repair synthesis) in human epidermal cells was measured as a function of age. Normal mammary skin specimens were obtained at surgery from 36 female patients, ranging in age from 17 to 77 years. The enzymatically isolated epidermal cells were analyzed for two parameters: (1) the number and percentage of cells carrying out repair synthesis, and (2) the rate of ultraviolet-induced unscheduled thymidine incorporation in individual cells. The results show that the percentage of epidermal cells capable of DNA excision repair synthesis does not decrease significantly with age, but that the rate of unscheduled DNA synthesis in individual cells decreases to a highly significant degree with advancing age.

Protection against pulmonary acid aspiration with ranitidine. A new histamine H2-receptor antagonist.

Ninety patients presenting for elective surgery were randomly divided into three groups A, B and C and studied on a double-blind basis to assess the effects of ranitidine, a new histamine H2 -receptor antagonist and placebo on gastric secretion. Group A received 150 mg ranitidine orally at 2200 hours on the evening before surgery and a further 150 mg 1-2 hours before operation. Group B received 150 mg ranitidine with premedication only, while Group C received a placebo at 2200 hours and again with premedication on the day of surgery. Gastric fluid was aspirated immediately after induction of anaesthesia and the volume and pH of the aspirate measured. Gastric volumes were significantly greater in the placebo group when compared to Group B, but not to Group A. The proportion of patients with pH greater than 2.5 at induction of anaesthesia was 100, 82.3 and 67.9% in Groups A, B and C, respectively. The percentage of patients who had measured gastric volume less than 25 ml or pH greater than 2.5 were Group A--90%, Group B--75.9% and Group C--57%. Thus ranitidine 150 mg orally on the evening before surgery and on the morning prior to anaesthetic induction lowered the mean volume and raised the average pH of gastric content to safe levels in all cases.

A simple and rapid method for evaluating the survival of xeroderma pigmentosum lymphoid lines after irradiation with ultraviolet light.

A simple, rapid, and reproducible test has been developed to measure the viability of cells after irradiation with ultraviolet light (UV). Epstein-Barr virus-transformed lymphoid lines, derived from patients with xeroderma pigmentosum (XP), were irradiated with UV, and the post-UV viability of the lymphoid lines was determined by the trypan blue dye exclusion method. The relative post-UV survival of the patients' lymphoid lines was similar to the relative post-UV survival of the patients' fibroblast strains.

Normal pressure hydrocephalus. Recognition and relationship to neurological abnormalities in Cockayne's syndrome.

Normal pressure hydrocephalus (NPH) in adults is a well-known cause of dementia. We describe NPH in children having the recessively inherited Cockayne's syndrome (CS). Cockayne's syndrome is characterized by cachectic dwarfism, neurological dysfunction, and cutaneous sunlight sensitivity. We noted that the NPH-associated triad of dementia, gait disturbance, and incontinence developed in CS patients. Computerized tomography of the brain in our four CS patients showed hydrocephalic enlargement of the brain ventricles greatest in the older patients. There was no evidence of cortical atrophy except in the one patient who had CS with xeroderma pigmentosum. Lumbar puncture and radionuclide cisternography in the two patients tested showed normal CSF pressure, with complete blockade to flow of radionuclide above the tentorium cerebelli, ventricular reflux, and delayed absorption. Studies of NPH in CS may elucidate the pathophysiology of NPH and methods to alter its sequelae.

Cockayne's syndrome fibroblasts have increased sensitivity to ultraviolet light but normal rates of unscheduled DNA synthesis.

Cockayne's syndrome is a form of cachectic dwarfism characterized by acute sun sensitivity and numerous other abnormalities of many organ systems. We studied fibroblasts from 9 Cockayne's syndrome patients to determine if their fibroblasts had abnormal post-ultraviolet light colony-forming ability or abnormal ultraviolet light-induced unscheduled DNA synthesis. The fibroblast strains from all the patients had markedly decreased post-ultraviolet light colony-forming ability in comparison with fibroblasts from control donors. Since this increased ultraviolet light sensitivity is propagable in vitro, it may be a manifestation of, or be closely associated with, the inherited genetic defect of this autosomal recessive disease. However, the patients' fibroblasts had normal rates of ultraviolet light-induced unscheduled DNA synthesis. Thus, unlike the UV sensitivity of DNA excision repair-deficient xeroderma pigmentosum strains, the UV sensitivity of Cockayne's syndrome strains is not related to abnormal DNA excision repair, at least to the extent that this repair process is reflected by rates of ultraviolet light-induced unscheduled DNA synthesis.

Xeroderma pigmentosum neurological abnormalities correlate with colony-forming ability after ultraviolet radiation.

Xeroderma pigmentosum is an autosomal recessive disease in which DNA repair processes are defective. All xeroderma pigmentosum patients develop premature aging of sun-exposed skin, and some develop neurological abnormalities due to premature death of nerve cells. Sensitivity to ultraviolet radiation of 24 xeroderma pigmentosum fibroblast strains was studied in vitro by measuring each strain's ability to divide and form colonies after irradiation. The most sensitive strains were derived from patients who had an early onset of neurological abnormalities; less sensitive strains were from patients with a later onset; and the most resistant strains were from patients without neurological abnormalities. The UV sensitivities of strains from each member of a sibling pair with xeroderma pigmentosum were identical, indicating that UV sensitivity of xeroderma pigmentosum strains is determined by the patient's inherited DNA repair defect. The results suggest that effective DNA repair is required to maintain the functional integrity of the human nervous system by preventing premature death of neurons.

Colony-forming ability of ultraviolet-irradiated xeroderma pigmentosum fibroblasts from different DNA repair complementation groups.

Patients with xeroderma pigmentosum develop severe sunlight-induced damage, including malignant neoplasms, on sun-exposed skin. Some patients also have neurological abnormalities. Xeroderma pigmentosum cells are known to have impaired ability to repair ultraviolet light- or chemical mutagen-induced damage to their DNA, and cell-fusion studies have shown five complementation groups among the DNA excision repair-deficient strains. All xeroderma pigmentosum fibroblast strains we tested had lower colony-forming abilities after ultraviolet irradiation than normal strains. Furthermore, we have found that strains from different complementation groups can have different post-ultraviolet colony-forming abilities and that strains from patients with neurological abnormalities are the most sensitive to ultraviolet light. These results suggest that extremely ineffective repair of damaged DNA in central nervous system neurons may be the cause of the neurological abnormalities.

Relation of D.N.A. repair processes to pathological ageing of the nervous system in xeroderma pigmentosum.

The severity of neurological abnormalities in patients with xeroderma pigmentosum has been found to be related to their ability to repair ultraviolet (U.V.)-damaged D.N.A. Patients with the most severe neurological abnormalities have the least effective D.N.A. repair is shown by the decreased colony-forming ability of their U.V.-irradiated fibroblasts. These results suggest that the lack of adequate D.N.A. repair is causally related to the clinical manifestations of a human heredodegenerative nervous system disease.