Cutaneous melanoma primary site is linked to nevus density

There are at least two pathways driving cutaneous melanoma; one is linked to an inherent melanoma susceptibility to nevi development and the second to environmental cumulative ultraviolet light exposure. In this study, we examined the relation between nevus density, accrued sun damage and the site of primary melanoma excision. In a series of 888 consecutive cutaneous melanoma patients, melanomas appearing in skin areas with a high relative nevus density were most prominent in men, with an elevated nevus count, at sites without solar elastosis, but with an epidemiological history of previous sunburn. The present study associates melanoma development to sites with high nevus density. Our study supports more careful surveillance of body areas with increased nevus density in patients with high total body number of nevi, especially when they report a history of sunburns at these sites.

Defective cell cycle checkpoint functions in melanoma are associated with altered patterns of gene expression

Defects in DNA damage responses may underlie genetic instability and malignant progression in melanoma. Cultures of normal human melanocytes (NHMs) and melanoma lines were analyzed to determine whether global patterns of gene expression could predict the efficacy of DNA damage cell cycle checkpoints that arrest growth and suppress genetic instability. NHMs displayed effective G1 and G2 checkpoint responses to ionizing radiation-induced DNA damage. A majority of melanoma cell lines (11/16) displayed significant quantitative defects in one or both checkpoints. Melanomas with B-RAF mutations as a class displayed a significant defect in DNA damage G2 checkpoint function. In contrast the epithelial-like subtype of melanomas with wild-type N-RAS and B-RAF alleles displayed an effective G2 checkpoint but a significant defect in G1 checkpoint function. RNA expression profiling revealed that melanoma lines with defects in the DNA damage G1 checkpoint displayed reduced expression of p53 transcriptional targets, such as CDKN1A and DDB2, and enhanced expression of proliferation-associated genes, such as CDC7 and GEMININ. A Bayesian analysis tool was more accurate than significance analysis of microarrays for predicting checkpoint function using a leave-one-out method. The results suggest that defects in DNA damage checkpoints may be recognized in melanomas through analysis of gene expression.

Melanocortin ligands: 30 years of structure-activity relationship (SAR) studies

The challenge of peptide and peptidomimetic research is the development of methods and techniques to improve the biological properties of native peptides and to convert peptide ligands into non-peptide compounds. Improved biological properties of peptides includes enhancement of stability, potency, and receptor selectivity, for both in vivo and in vitro applications. The design of a ligand with specific activity and desired biological properties is a complex task, and, to accomplish this objective, knowledge about putative interactions between a ligand and the corresponding receptor will be valuable. This includes interactions for both the binding and signal transduction processes. Structure-activity relationship (SAR) studies involve systematic modification of a lead peptide and are designed to provide insight into potential interactions involved in the formation of the ligand-receptor complex. It is desirable to have knowledge about both favorable and unfavorable processes that may occur in putative ligand-receptor interactions that result in either receptor stimulation or inhibition. Herein, we discuss various SAR studies that have involved melanocortin peptides over three decades and the information these studies have provided to the melanocortin field.

Influence of Genes, Nevi, and Sun Sensitivity on Melanoma Risk in a Family Sample Unselected by Family History and in Melanoma-Prone Families

BACKGROUND

Few family studies have investigated the effects of genetic, environmental, and host factors on melanoma risk, and most have been restricted to high-risk families. We assessed the role of these factors on melanoma risk in two types of families: families ascertained through melanoma probands but unselected by family history and melanoma-prone families.

METHODS

Data on pigmentary traits, nevus phenotypes, exposure to sun, and reactions to sunlight were collected from 295 families unselected by family history and 53 melanoma-prone families. We modeled melanoma risk using a logistic regressive model incorporating the effect of a melanoma-predisposing gene, familial dependence, and potential risk factors (e.g., pigmentary traits, nevus phenotypes, history of sun exposure, skin reactions to sunlight). Maximum-likelihood estimates of the parameters of the regressive model were used to compute odds ratios associated with each risk factor and age-specific melanoma risk depending on the genotype at the melanoma-predisposing gene and the effects of risk factors. All statistical tests were two-sided.

RESULTS

In the families unselected by family history, there was statistically significant evidence (P<.001) for a dominant gene, with melanoma risk reaching 0.49 and 0.67 by age 80 years in male and female gene carriers, respectively. Melanoma risk was statistically significantly influenced by total nevi (odds ratio of hazard function [OR] = 5.81, 95% confidence interval [CI] = 3.47 to 8.99), sun exposure (OR = 5.37, 95% CI = 4.44 to 6.36), and sunburn interacting with the gene (OR = 26.31, 95% CI = 7.56 to 99.22 in gene carriers and OR = 1.67, 95% CI = 1.36 to 2.03 in noncarriers). Twenty of the 53 melanoma-prone families had cosegregating mutations in CDKN2A, a gene known to be associated with melanoma. In these 53 families, three risk factors in addition to CDKN2A mutations increased melanoma risk: dysplastic nevi (OR = 2.32, 95% CI = 2.08 to 2.58), total nevi (OR = 1.99, 95% CI = 1.61 to 2.20) and sunburn (OR = 5.16, 95% CI = 4.82 to 5.52).

CONCLUSIONS

Together, a melanoma-predisposing gene (identified as being CDKN2A in melanoma-prone families), number of nevi and/or dysplastic nevi, and sun-related covariates influence melanoma risk in both families unselected by family history and melanoma-prone families.

Gene expression profile of tissue engineered skin subjected to acute barrier disruption

The main function of the skin is to protect the body from infection, dehydration, and other environmental insults by creating an impermeable barrier of cornified cell layers, the stratum corneum. In contrast to cells in culture, tissue-engineered skin equivalents contain well-developed basal, spinous, granular, and cornified cell layers providing an excellent model to study the tissue response to barrier disruption. After 7 d of culture at the air-liquid interface the barrier of the tissues was disrupted by short exposure to acetone and the global gene expression profile of the tissues was evaluated using DNA microarrays. We found that tissue-engineered skin responds to barrier disruption by a two-wave dynamic response. Early on, the cells upregulate signal transducing, stress, proliferation, and inflammation genes to protect the tissue and possibly to communicate the damage to the immune system and neighboring tissues. At later times, pro-inflammatory cytokines and some growth-related genes are significantly reduced but enzymes that participate in lipid synthesis increase, suggesting that the epidermal cells attempt to restore the lost barrier. Quantitative immunostaining for the proliferation antigen Ki67 revealed that barrier disruption by acetone increased proliferation by 4-fold in agreement with the microarray data and previous in vivo studies. Our work suggests that functional genomics may be used in tissue engineering to understand tissue development, wound regeneration, and response to environmental stimuli. A better understanding of engineered tissues at the molecular level may facilitate their application in the clinic and as biosensors for toxicologic testing.