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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We analyze published data on cancer incidence as a function of age for (i) cutaneous melanoma for cohorts of males in Connecticut and (ii) hepatocellular cancer in Mozambique, China and Romania, on the basis of multi-hit models for carcinogenesis. The simple multi-hit model suggests an unlikely scenario in which, as the cohorts advance or the intensity of mutagenesis increases, fewer mutations are required to bring about the appearance of cancer. We present a new version of the multi-hit model in which two sets of mutatable loci are present, of differing sensitivities to mutagens. This provides a more acceptable description in which the number of rate-limiting steps for the appearance of cancer drops as the frequency of mutation rises, so that some of these steps are no longer rate-limiting.
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PMID:Rate-limiting steps in carcinogenesis and their bearing on the incidence/age data for cutaneous melanoma and hepatocellular carcinoma. 166 4

Incidence registration and survival data for non-melanocytic skin neoplasms and cutaneous melanoma have been abstracted from the population-based system of the Cancer Registry of the Swiss Canton of Vaud, which has been operating in a particularly favourable environment, since the large majority of cutaneous lesions resected in the area are examined by a pathologist. Among the 5,712 cases registered, 66.7% were basal-cell carcinomas, 20.6% squamous-cell cancers, 9.3% cutaneous melanomas and 3.4% other miscellaneous histological types. The distribution by histological type did not differ appreciably in the 2 sexes, but there were marked inter-sex differences as regards anatomical site. In both sexes, head and neck was by far the commonest localization for non-melanomatous neoplasms (69 to 81% of all incident cases), followed by trunk for basal-cell cancers (18% in males, 15% in females) and upper limb for squamous-cell (10% in males, 17% in females). The distribution of skin melanomas differed considerably between the 2 sexes, by far the commonest site being the trunk for males (45% of cases) and lower limbs for females (40%), followed by head and neck (22% in both sexes). Incidence rates for both basal- and squamous-cell cancers increased with age, and rates were higher in males for each localization except the lower limb. In contrast, incidence for melanoma was higher in females, and incidence rates did not increase with age above 55 years for all sites except head and neck. This can be interpreted in terms of cohort effect, since mortality from melanoma has substantially increased in Switzerland across subsequent birth cohorts. Although this study is essentially descriptive, accurate inspection of these data provides some support for the major aetiological hypotheses of skin carcinogenesis, i.e., the observation that the large majority of basal- and squamous-cell cancers arise on the head and neck confirms the importance of long-term ultraviolet exposure; the relative excess of squamous-cell as compared to basal-cell neoplasms on the upper limb may suggest the role of exposure to other (chemical) carcinogens; and the proportional excess of melanomas on the trunk in males and lower limb in females further indicates that intermittent exposure to sunlight is probably the relevant aetiologic factor for melanocytic skin neoplasms.
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PMID:Descriptive epidemiology of skin cancer in the Swiss Canton of Vaud. 319 22

The putative ultraviolet (u.v.) carcinogenesis of cutaneous melanoma bears sufficient inconsistencies as to seriously challenge this theory. A more attractive hypothesis is the incrimination of a hitherto unknown chemical xenobiotic. This hypothesis explains the dramatic increase in incidence rates in most affluent countries during the last two or three decades. It also explains the particular risk of populations of high socio-economic status and the increased risk of indoor workers. It finally explains the urban-rural and coastal-inland trends observed in many countries with high incidence rates.
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PMID:Melanoma of the skin is not caused by ultraviolet radiation but by a chemical xenobiotic. 364 22

Xeroderma pigmentosum (XP), is a rare, autosomal recessive disease with sun sensitivity and multiple neoplasms in association with reduced DNA repair. As a reflection of the clinical consequences of deficient DNA repair, XP serves as a model for determining the effects of proficient DNA repair. To estimate the risk of developing neoplasms in XP, we abstracted reports of 726 XP patients (from 41 countries) published from 1874 to 1982. Despite limitations of a literature survey, the XP patients under age 20 years had an estimated 2000-fold increase in frequency of basal cell and squamous cell carcinoma of the skin, of cutaneous melanoma, of cancer of the anterior eye, and of cancer of the anterior tongue, in comparison to the general population. These sites are all potentially exposed to u.v. radiation, a strong carcinogen which produces DNA damage that is poorly repaired by XP cells. XP patients under age 20 years also had an estimated 12-fold increase in occurrence of neoplasms in sites not exposed to u.v. radiation. Among the XP patients under age 40 years with internal cancer, there was a disproportionate representation of malignant neoplasms of the brain (especially sarcomas), and oral cavity (excluding tongue) compared to US whites under age 40 years. These internal neoplasms may be related to exposure to chemical environmental carcinogens that cause DNA damage which, like u.v.-induced damage, is poorly repaired by XP cells. These reports provide no evidence of an increase in XP of common lethal neoplasms such as lymphomas, or female genital tract or endocrine system cancers. These findings suggest that DNA repair plays a role in protection against u.v.-induced neoplasia and in protection against some internal neoplasms in the general population.
Carcinogenesis 1984 Apr
PMID:DNA repair protects against cutaneous and internal neoplasia: evidence from xeroderma pigmentosum. 670 49

Xeroderma pigmentosum, Cockayne syndrome, the xeroderma pigmentosum-Cockayne syndrome complex, and trichothiodystrophy cells have defects in DNA repair and are associated with clinical and cellular hypersensitivity to ultraviolet radiation (UV). Familial dysplastic nevus syndrome cells have UV hypermutability. Although xeroderma pigmentosum and dysplastic nevus syndrome have markedly increased cancer risk. Cockayne syndrome and trichothiodystrophy do not. At the molecular level, these disorders are associated with several different genetic defects as evidenced by the existence of multiple overlapping complementation groups. Recent progress has been made in identifying the chromosomal location and cloning the defective genes in these disorders. Using plasmid shuttle vectors we have shown abnormal repair and mutagenesis of DNA damaged by 254-nm (UVC) or 295-nm (UVB) radiation or the chemical carcinogen aflatoxin in cells from patients with xeroderma pigmentosum. Although xeroderma pigmentosum cells are defective in repair of all photoproducts, Cockayne syndrome cells appear to be defective in repair of cyclobutane dimers and have normal repair of nondimer photoproducts. DNS cells have post UV plasmid hypermutability. These diseases may serve as models for examining molecular mechanisms of carcinogenesis in humans.
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PMID:Xeroderma pigmentosum and related disorders: examining the linkage between defective DNA repair and cancer. 796 92

Human cutaneous melanoma is heterogeneous with respect to the genetic aberrations involved and the genes altered are potential targets for the immune system. The incidence of cutaneous melanoma is known to be linked to UV peak exposure, and the N-ras oncogene is clearly one of the genes involved in the UV carcinogenesis in melanoma. It is mutated in a significant proportion of melanomas and therefore may serve as a target for T cells. Here, we report that an human leukocyte antigen-A2 binding peptide CLLDILDTAGL, encompassing the frequently found 61-Leu mutation in N-ras, induces cytotoxic T lymphocytes from healthy donor blood that lyse 61-Leu N-ras transfected melanoma cells. Furthermore, we have found an association between the presence of N-ras mutations and clinical response to immunotherapy with interleukin-2 plus interferon in a group of stage IV melanoma patients. Although the overall survival of these patients was not affected by the N-ras status of their melanomas, these studies suggest that mutated N-ras may provide a target for cytotoxic T lymphocytes in melanoma patients.
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PMID:UV-induced N-ras mutations are T-cell targets in human melanoma. 957 25

The health risks associated with ozone depletion will principally be those due to increased ultraviolet B (UV-B) radiation in the environment, i.e., increased damage to the eyes, the immune system, and the skin. Some new risks may also be introduced with the increased use of alternatives to the ozone-depleting substances (ODSs). Quantitative risk estimates are available for some of the UV-B-associated effects, e.g., cataract and skin cancer; however, the data are insufficient to develop similar estimates for effects such as immunosuppression and the toxicity of alternatives. Ocular damage from UV exposures includes effects on the cornea, lens, iris, and associated epithelial and conjunctival tissues. The most common acute ocular effect of environmental ultraviolet radiation (UVR) is photokeratitis. Also known as snowblindness in skiers, this condition also occurs in other outdoor recreationists. Chronic eye conditions likely to increase with ozone depletion include cataract, squamous cell carcinoma, ocular melanoma, and a variety of corneal/conjunctival effects, e.g., pterygium and pinguecula. Suppression of local (at the site of UV exposure) and systemic (at a distant, unexposed site) immune responses to a variety of antigens has been demonstrated in both humans and animals exposed to UV-B. In experiments with animals these effects have been shown to worsen the course/outcome of some infectious diseases and cancers. There is reasonably good evidence that such immunosuppression plays a role in human carcinogenesis; however, the implications of such immunosuppression for human infectious diseases are still unknown. In light-skinned populations, exposure to solar UVR appears to be the most important environmental risk factor for basal and squamous cell carcinomas and cutaneous melanoma. Originally it was believed that total accumulated exposure to UVR was the most important environmental factor in determining risk for these tumors. Recent information now suggests that only squamous cell carcinoma risk is related to total exposure. In the cases of both basal cell carcinoma and melanoma, new information suggests that increases in risk are tied to early exposures (before about age 15), particularly those leading to severe sunburns. Testing of a number of the chlorofluorocarbon (CFC) alternatives indicates that most of these chemicals have low acute toxicity, and low to moderate chronic toxicity. Some chemicals that were originally proposed as alternatives have been dropped from consideration because these tests raised concerns about toxicity and/or manufacturing difficulties. In one instance, high accidental occupational exposure was associated with liver damage, underlining the need for care in the use of these substitutes. Recent quantitative risk estimates have been developed for cataract, melanoma, and all skin cancers combined. These estimates indicate that under the Montreal Adjustments, cataract and skin-cancer incidence will peak mid-century at additional incidences of just under 3 per 100,000 and about 7 per 100,000, respectively.
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PMID:Health risks. 989 51

The role of ultraviolet (UV) radiation in the induction of nonmelanoma skin cancer is widely accepted, although its precise contribution to the development of primary cutaneous melanoma skin cancer requires further definition. We found that painting aloe emodin, a trihydroxyanthraquinone from Aloe barbadensis, in ethyl alcohol vehicle on the skin of mice in conjunction with exposure to UVB (280-320 nm) radiation results in the development of melanin-containing skin tumors. C3H/HeN mice were treated thrice weekly with aloe emodin in a 25% ethanol in water vehicle and exposed to 15 kJ/m2 UV radiation. Neither ethanol vehicle nor aloe emodin alone induced skin tumors in the absence of UV radiation. In two separate experiments, 20-30% of the mice treated with a combination of UV radiation and ethanol vehicle and 50-67% of the UV-irradiated animals given aloe emodin in ethanol vehicle developed primary cutaneous melanin-containing tumors. The diagnosis of melanoma was established using Fontana silver stain for melanin; these tumors were negative for vimentin and keratin. Melanin-containing melanosomes were observed by transmission electron microscopy in tumors diagnosed as melanomas. Although the mechanism of carcinogenesis in these mice is currently unknown, our findings have led to the development of the first facile murine model for the induction of primary melanoma. This model has the potential to clarify the role of UV radiation in the etiology of malignant melanoma.
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PMID:Induction of primary cutaneous melanomas in C3H mice by combined treatment with ultraviolet radiation, ethanol and aloe emodin. 1098 13

Telomerase plays a key role in carcinogenesis. It is activated in most immortal cell lines and human cancers, including cutaneous melanoma (CM). Increased cell proliferation and deregulation of the cell cycle occur in human cancers. Links between telomerase activity (TA), cell proliferation, cell death and expression of cell-cycle regulators have not been extensively elucidated in CM. In this study, we investigated TA, mitotic index (MI), apoptotic index (AI), Ki-67 and nuclear positivity of cyclins D1 and A (Ki-67+ N/1,000, cyclin D1+N/1,000, cyclin A+N/1,000) in 42 primary cutaneous melanomas (PCMs). TA was detected in all cases and directly correlated with MI, Ki-67+N/1,000, cyclin D1+N/1,000 and cyclin A+N/1,000 (p < 0.001); it was not correlated with AI. When subdividing PCMs into radial and vertical growth phase melanomas (RGPMs, VGPMs), a correlation was maintained only with MI (p < 0.005) and cyclin D1 +N/1,000 (p < 0.005). Although MI and Ki-67+N/1,000 were highly correlated with cyclin D1+N/1,000 and cyclin A+N/1,000 (p < 0.001) when considering all cases together, a high correlation was found in the RGPM and VGPM groups between cyclin A+N/1,000 and Ki-67+N/1,000 only (p < 0.001), thus suggesting that cyclin A is more closely correlated with cell proliferation than cyclin D1. Our results further support the association between TA, tumor cell proliferation and cyclin D1 and A expression in PCM, though it is possible that links between TA and proliferation, on the one hand, and TA and cyclin D1 expression, on the other, might occur following various pathways.
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PMID:Detection of telomerase activity and correlation with mitotic and apoptotic indices, Ki-67 and expression of cyclins D1 and A in cutaneous melanoma. 1105 70

Mutations in the ras genes are key events in the process of carcinogenesis; in particular, point mutations in codon 61 of exon 2 of the N-ras gene occur frequently in cutaneous melanoma. To investigate whether these mutations occur in early or late tumor progression phases, we searched for point mutations in the N- and K-ras genes in 69 primary cutaneous melanoma, 35 metastases, and seven nevocellular nevi in association with cutaneous melanoma. Lesions were microdissected in order to procure pure tumor samples from the distinctive growth phases of the cutaneous melanoma; the very sensitive denaturing gradient gel electrophoresis technique was used to visualize the mutations, and was followed by sequencing. Point mutations in the N-ras gene but not in the K-ras gene were detected on denaturing gradient gel electrophoresis. Twenty-three primary (33%) and nine metastatic (26%) melanomas showed bandshifts for N-ras. In the majority of cases, mutations occurring in early growth phases (i.e., the "intraepidermal" radial growth phase), were preserved in later growth phases (i.e., the invasive radial growth phase, vertical growth phase, and metastatic phase), which proves the clonal relationship between the successive growth phases. In three cases, however, the mutations differed between the distinctive growth phases within the same cutaneous melanoma, due to the occurrence of an additional mutation (especially in codon 61) in a later tumor progression phase. Our approach also permitted us to analyze the mutational status of nevi, associated with cutaneous melanoma. Six out of seven associated nevi carried the same sequence (mutated or wild-type) as the primary cutaneous melanoma, whereas in one case the sequence for N-ras differed between the primary melanoma and the associated nevus. In conclusion, this approach allowed us to demonstrate the clonal relationship between subsequent growth phases of melanoma and associated nevi; our results suggest that N-ras exon 1 mutations preferentially occur during early stages of tumor progression and hence may be involved in melanoma initiation, whereas those in N-ras exon 2 are found preferentially during later stages and hence are more probably involved in metastatic spread of cutaneous melanoma.
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PMID:Analysis of N- and K-ras mutations in the distinctive tumor progression phases of melanoma. 1188 12


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