Recent Advances in Clinical Research for Skin Cancer Chemoprevention.

Neoplasm arising from the keratinocytes or melanocytes in the skin is the most prevalent type of cancer in the United States and worldwide. Since ultraviolet (UV) radiation may be a causing factor for several types of skin cancer, effective strategies to manage skin cancer include preventive measures such as minimizing exposure to UV and applying sunscreens. However, the effect of sunscreen in reducing skin cancer incidence remains uncertain. An alternative approach to prevent skin cancer is chemoprevention, which is defined as using either natural products or synthetic compounds to inhibit, delay, or reverse the development of cancer. Preclinical studies have demonstrated the effectiveness of multiple pharmacological agents and dietary supplements. However, whether preclinical findings can be translated into clinical application is unknown. This review evaluates the state of recent clinical trials investigating chemopreventive agents focusing on skin cancer to compare the target populations, interventions, endpoints, and outcomes of these trials. The ClinicalTrials and PubMed databases were searched for their available literature using the key words "skin cancer" and "chemoprevention". The objective of this review is to provide updated information on the effectiveness and side effects of promising chemopreventive agents in human subjects and to identify research gaps.

Transfersome Encapsulated with the R-carvedilol Enantiomer for Skin Cancer Chemoprevention.

The R-carvedilol enantiomer, present in the racemic mixture of the chiral drug carvedilol, does not bind to the ß-adrenergic receptors, but exhibits skin cancer preventive activity. For skin delivery, R-carvedilol-loaded transfersomes were prepared using various ratios of drug, lipids, and surfactants, and characterized for particle size, zeta potential, encapsulation efficiency, stability, and morphology. Transfersomes were compared for in vitro drug release and ex vivo skin penetration and retention. Skin irritation was evaluated by viability assay on murine epidermal cells and reconstructed human skin culture. Single-dose and repeated-dose dermal toxicity was determined in SKH-1 hairless mice. Efficacy was evaluated in SKH-1 mice exposed to single or multiple ultraviolet (UV) radiations. Transfersomes released the drug at a slower rate, but significantly increased skin drug permeation and retention compared with the free drug. The transfersome with a drug-lipid-surfactant ratio of 1:3:0.5 (T-RCAR-3) demonstrated the highest skin drug retention and was selected for further studies. T-RCAR-3 at 100 µM did not induce skin irritation in vitro and in vivo. Topical treatment with T-RCAR-3 at 10 µM effectively attenuated acute UV-induced skin inflammation and chronic UV-induced skin carcinogenesis. This study demonstrates feasibility of using R-carvedilol transfersome for preventing UV-induced skin inflammation and cancer.

The ionophore thiomaltol induces rapid lysosomal accumulation of copper and apoptosis in melanoma.

In this report, we investigate the toxicity of the ionophore thiomaltol (Htma) and Cu salts to melanoma. Divalent metal complexes of thiomaltol display toxicity against A375 melanoma cell culture resulting in a distinct apoptotic response at submicromolar concentrations, with toxicity of Cu(tma)2 > Zn(tma)2 >> Ni(tma)2. In metal-chelated media, Htma treatment shows little toxicity, but the combination with supplemental CuCl2, termed Cu/Htma treatment, results in toxicity that increases with suprastoichiometric concentrations of CuCl2 and correlates with the accumulation of intracellular copper. Electron microscopy and confocal laser scanning microscopy of Cu/Htma treated cells shows a rapid accumulation of copper within lysosomes over the course of hours, concurrent with the onset of apoptosis. A buildup of ubiquitinated proteins due to proteasome inhibition is seen on the same timescale and correlates with increases of copper without additional Htma.

Topical carvedilol delivery prevents UV-induced skin cancer with negligible systemic absorption.

The ß-blocker carvedilol prevents ultraviolet (UV)-induced skin cancer, but systemic drug administration may cause unwanted cadiovascular effects. To overcome this limitation, a topical delivery system based on transfersome (T-CAR) was characterized ex vivo and in vivo. T-CAR was visualized by Transmission Electron Microscopy as nanoparticles of spherical and unilamellar structure. T-CAR incorporated into carbopol gel and in suspension showed similar drug permeation and deposition profiles in Franz diffusion cells loaded with porcine ear skin. In mice exposed to a single dose UV, topical T-CAR gel (10 µM) significantly reduced UV-induced skin edema and cyclobutane pyrimidine dimer formation. In mice exposed to chronic UV radiation for 25 weeks, topical T-CAR gel (10 µM) significantly delayed the incidence of tumors, reduced tumor number and burden, and attenuated Ki-67 and COX-2 expression. The T-CAR gel was subsequently examined for skin deposition, systemic absorption and cardiovascular effects in mice. In mice treated with repeated doses of T-CAR gel (100 µM), the drug was undetectable in plasma, the heart rate was unaffected, but skin deposition was significantly higher than mice treated with oral carvedilol (32 mg/kg/day). These data indicate that the carbopol-based T-CAR gel holds great promise for skin cancer prevention with negligible systemic effects.

Topical Delivery of Carvedilol Loaded Nano-Transfersomes for Skin Cancer Chemoprevention.

The ß-blocker carvedilol has been shown to prevent skin carcinogenesis in vitro and in vivo. Since systemic absorption of the ß-blocker may cause cardiovascular disturbance, we developed a carvedilol loaded transfersome for skin-targeted delivery. Transfersomes were prepared using phospholipids and surfactants at various ratios and characterized. One formulation (F18) selected for further analysis was composed of carvedilol, soy phosphatidylcholine, and Tween-80 at a ratio of 1:3:0.5, which had a particle size of 115.6 ± 8.7 nm, a zeta potential of 11.34 ± 0.67 mV, and an encapsulation efficiency of 93.7 ± 5.1%. F18 inhibited EGF-induced neoplastic transformation of mouse epidermal JB6 P+ cells at non-toxic concentrations, while only high concentrations induced cytotoxicity in JB6 P+ and human keratinocytes HaCaT. Compared to the free drug, F18 released through the dialysis membrane and permeated through the porcine ear skin at a slower rate, but similarly depositing the drug in the epidermis and dermis of the skin. Consistently, surface application of F18 on reconstructed full-thickness human skin showed slower drug permeation, while it suppressed ultraviolet-induced DNA damage, inflammatory gene expression, and apoptosis. These data indicate that transfersome is a promising topical delivery system of carvedilol for preventing ultraviolet-induced skin damage and carcinogenesis.

A Possible Link of Genetic Variations in ER/IGF1R Pathway and Risk of Melanoma.

The mechanism of gender disparity in cutaneous melanoma incidence remains unclear. Steroid hormones including estrogens have long been implicated in the course of melanoma, but the conclusion is controversial. Estrogen receptors (ERs) and insulin-like growth factor 1 receptor (IGF1R) show extensive crosstalk in cancer development, but how the ER/IGF1R network impacts melanoma is currently unclear. Here we studied the melanoma associations of selected SNPs from the ER/IGF1R network. Part of the International Genes, Environment, and Melanoma (GEM) cohort was used as a discovery set, and the Gene Environment Association Studies Initiative (GENEVA) dataset served as a validation set. Based on the associations with other malignant disease conditions, thirteen single nucleotide polymorphism (SNP) variants in ESR1, ESR2, IGF1, and IGF1R were selected for candidate gene association analyses. The rs1520220 in IGF1 and rs2229765 in IGF1R variants were significantly associated with melanoma risk in the GEM dataset after Benjamini-Hochberg multiple comparison correction, although they were not validated in the GENEVA set. The discrepancy may be caused by the multiple melanoma characteristics in the GEM patients. Further analysis of gender disparity was carried out for IGF1 and IGF1R SNPs in the GEM dataset. The GG phenotype in IGF1 rs1520220 (recessive model) presented an increased risk of melanoma (OR = 8.11, 95% CI: 2.20, 52.5, p = 0.006) in men but a significant opposite effect in women (OR = 0.15, 95% CI: 0.018, 0.86, p = 0.045). The AA genotype in IGF1R rs2229765 (recessive model) showed a significant protective effect in men (OR = 0.24, 95% CI: 0.07, 0.64, p = 0.008) and no effect in women. Results from the current study are warranted for further validation.

A Phase IIa Trial of Metformin for Colorectal Cancer Risk Reduction among Individuals with History of Colorectal Adenomas and Elevated Body Mass Index.

Obesity is associated with risk of colorectal adenoma (CRA) and colorectal cancer. The signaling pathway activated by metformin (LKB1/AMPK/mTOR) is implicated in tumor suppression in ApcMin/+ mice via metformin-induced reduction in polyp burden, increased ratio of pAMPK/AMPK, decreased pmTOR/mTOR ratio, and decreased pS6Ser235/S6Ser235 ratio in polyps. We hypothesized that metformin would affect colorectal tissue S6Ser235 among obese patients with recent history of CRA. A phase IIa clinical biomarker trial was conducted via the U.S. National Cancer Institute-Chemoprevention Consortium. Nondiabetic, obese subjects (BMI ≥30) ages 35 to 80 with recent history of CRA were included. Subjects received 12 weeks of oral metformin 1,000 mg twice every day. Rectal mucosa biopsies were obtained at baseline and end-of-treatment (EOT) endoscopy. Tissue S6Ser235 and Ki-67 immunostaining were analyzed in a blinded fashion using Histo score (Hscore) analysis. Among 32 eligible subjects, the mean baseline BMI was 34.9. Comparing EOT to baseline tissue S6Ser235 by IHC, no significant differences were observed. Mean (SD) Hscore at baseline was 1.1 (0.57) and 1.1 (0.51) at EOT; median Hscore change was 0.034 (P = 0.77). Similarly, Ki-67 levels were unaffected by the intervention. The adverse events were consistent with metformin's known side-effect profile. Among obese patients with CRA, 12 weeks of oral metformin does not reduce rectal mucosa pS6 or Ki-67 levels. Further research is needed to determine what effects metformin has on the target tissue of origin as metformin continues to be pursued as a colorectal cancer chemopreventive agent.

Trends in Medical Aid in Dying in Oregon and Washington.

Importance: The combined 28 years of data of medical aid in dying (MAID) between Oregon (OR) and Washington (WA) are the most comprehensive in North America. No reports to date have compared MAID use in different US states. Objective: To evaluate and compare patterns of MAID use between the states with the longest-running US death with dignity programs. Design, Setting, and Participants: A retrospective observational cohort study of OR and WA patients with terminal illness who received prescriptions as part of their states' legislation allowing MAID. All published annual reports, from 1998 to 2017 in OR and from 2009 to 2017 in WA, were reviewed. A total of 3368 prescriptions were included. Main Outcomes and Measures: Number of deaths from self-administration of lethal medication vs number of prescriptions written. Results: A combined 3368 prescriptions were written in OR and WA, with 2558 patient deaths from lethal ingestion (76.0%). Of the 2558 patients, most were male (1311 [51.3%]), older than 65 years (1851 [72.4%]), and non-Hispanic white (2426 [94.8%]). The most common underlying illnesses were cancer (1955 [76.4%]), neurologic illness (261 [10.2%]), lung disease (144 [5.6%]), and heart disease (117 [4.6%]). Loss of autonomy (2235 [87.4%]), impaired quality of life (2203 [86.1%]), and loss of dignity (1755 [68.6%]) were the most common reasons for pursuing MAID. Time between drug intake to coma ranged from 1 to 660 minutes and time from drug intake to death ranged from 1 to 6240 minutes. In the 1557 patients for whom rates of complications were reported, 1494 (96.0%) did not experience a complication (592 of 626 [94.6%] in OR and 902 of 931 [96.8%] in WA). Eight patients (<0.5%) regained consciousness after drug ingestion in OR. Annual rates per year for percentage of patients who received a prescription ingesting the prescribed medication ranged from 48% to 87%, with no significant time trend in OR (adjusted odds ratio per year, 1.01; 95% CI, 0.99-1.02; P = .59) but with an increase over time in WA (adjusted odds ratio per year, 1.13; 95% CI, 1.08-1.19; P < .001). In both OR and WA there were increases in the number of patient deaths due to MAID per 1000 deaths over time. Conclusions and Relevance: In this study, MAID results in Oregon and Washington were similar, although MAID use measured as a percentage of patients prescribed lethal medications and then self-administering them increased only in WA. Most patients who acquired lethal prescriptions had cancer or terminal illnesses that are difficult to palliate and lead to loss of autonomy, dignity, and quality of life.

Race-, Age-, and Anatomic Site-Specific Gender Differences in Cutaneous Melanoma Suggest Differential Mechanisms of Early- and Late-Onset Melanoma.

In order to explore melanoma risk factors through gender-, age-, race-, and site-specific incidence rates, malignant melanoma cases from the Caucasian whites and non-whites were retrieved from the US SEER database. Age-standardized, age-, and site-specific tumor rates were calculated. All races and both genders showed positive annual average percentage changes (AAPCs) over the years, but AAPCs varied at different body sites, with men's trunk exhibiting the fastest increase. Non-whites were diagnosed at a significantly younger age than whites and showed a trend towards fewer gender differences in the age of diagnosis. However, non-whites and whites showed a similar pattern of age-specific gender differences in the incidence rate ratios. A consistent spiked difference (female vs. male, incidence rate ratio (IRR) >2) was observed at or near the age of 20⁻24 in all race groups and at all body sites. The highest female vs. male IRR was found in the hip and lower extremities, and the lowest IRR was found in the head and neck region in all races. These race-, gender-, and site-dependent differences suggest that age-associated cumulative sun exposure weighs significantly more in late-onset melanomas, while genetics and/or pathophysiological factors make important contributions to early-onset melanomas.

Chemoprevention agents for melanoma: A path forward into phase 3 clinical trials.

Recent progress in the treatment of advanced melanoma has led to unprecedented improvements in overall survival and, as these new melanoma treatments have been developed and deployed in the clinic, much has been learned about the natural history of the disease. Now is the time to apply that knowledge toward the design and clinical evaluation of new chemoprevention agents. Melanoma chemoprevention has the potential to reduce dramatically both the morbidity and the high costs associated with treating patients who have metastatic disease. In this work, scientific and clinical melanoma experts from the national Melanoma Prevention Working Group, composed of National Cancer Trials Network investigators, discuss research aimed at discovering and developing (or repurposing) drugs and natural products for the prevention of melanoma and propose an updated pipeline for translating the most promising agents into the clinic. The mechanism of action, preclinical data, epidemiological evidence, and results from available clinical trials are discussed for each class of compounds. Selected keratinocyte carcinoma chemoprevention studies also are considered, and a rationale for their inclusion is presented. These data are summarized in a table that lists the type and level of evidence available for each class of agents. Also included in the discussion is an assessment of additional research necessary and the likelihood that a given compound may be a suitable candidate for a phase 3 clinical trial within the next 5 years.

Oxidative stress and antioxidants in the pathophysiology of malignant melanoma.

The high number of somatic mutations in the melanoma genome associated with cumulative ultra violet (UV) exposure has rendered it one of the most difficult of cancers to treat. With new treatment approaches based on targeted and immune therapies, drug resistance has appeared as a consistent problem. Redox biology, including reactive oxygen and nitrogen species (ROS and RNS), plays a central role in all aspects of melanoma pathophysiology, from initiation to progression and to metastatic cells. The involvement of melanin production and UV radiation in ROS/RNS generation has rendered the melanocytic lineage a unique system for studying redox biology. Overall, an elevated oxidative status has been associated with melanoma, thus much effort has been expended to prevent or treat melanoma using antioxidants which are expected to counteract oxidative stress. The consequence of this redox-rebalance seems to be two-fold: on the one hand, cells may behave less aggressively or even undergo apoptosis; on the other hand, cells may survive better after being disseminated into the circulating system or after drug treatment, thus resulting in metastasis promotion or further drug resistance. In this review we summarize the current understanding of redox signaling in melanoma at cellular and systemic levels and discuss the experimental and potential clinic use of antioxidants and new epigenetic redox modifiers.

Final Analysis of the Prevention of Early Menopause Study (POEMS)/SWOG Intergroup S0230.

Premature menopause is a serious long-term side effect of chemotherapy. We evaluated long-term pregnancy and disease-related outcomes for patients in S0230/POEMS, a study in premenopausal women with stage I-IIIA estrogen receptor-negative, progesterone receptor-negative breast cancer to be treated with cyclophosphamide-containing chemotherapy. Women were randomly assigned to standard chemotherapy with or without goserelin, a gonadotropin-releasing hormone agonist, and were stratified by age and chemotherapy regimen. All statistical tests were two-sided. Of 257 patients, 218 were eligible and evaluable (105 in the chemotherapy + goserelin arm and 113 in the chemotherapy arm). More patients in the chemotherapy + goserelin arm reported at least one pregnancy vs the chemotherapy arm (5-year cumulative incidence = 23.1%, 95% confidence interval [CI] = 15.3% to 31.9%; and 12.2%, 95% CI = 6.8% to 19.2%, respectively; odds ratio = 2.34; 95% CI = 1.07 to 5.11; P = .03). Randomization to goserelin + chemotherapy was associated with a nonstatistically significant improvement in disease-free survival (hazard ratio [HR] = 0.55; 95% CI = 0.27 to 1.10; P = .09) and overall survival (HR = 0.45; 95% CI = 0.19 to 1.04; P = .06). In this long-term analysis of POEMS/S0230, we found continued evidence that patients randomly assigned to receive goserelin + chemotherapy were not only more likely to avoid premature menopause, but were also more likely to become pregnant without adverse effect on disease-related outcomes.

Systems biology analysis of mitogen activated protein kinase inhibitor resistance in malignant melanoma.

BACKGROUND: Kinase inhibition in the mitogen activated protein kinase (MAPK) pathway is a standard therapy for cancer patients with activating BRAF mutations. However, the anti-tumorigenic effect and clinical benefit are only transient, and tumors are prone to treatment resistance and relapse. To elucidate mechanistic insights into drug resistance, we have established an in vitro cellular model of MAPK inhibitor resistance in malignant melanoma. METHODS: The cellular model evolved in response to clinical dosage of the BRAF inhibitor, vemurafenib, PLX4032. We conducted transcriptomic expression profiling using RNA-Seq and RT-qPCR arrays. Pathways of melanogenesis, MAPK signaling, cell cycle, and metabolism were significantly enriched among the set of differentially expressed genes of vemurafenib-resistant cells vs control. The underlying mechanism of treatment resistance and pathway rewiring was uncovered to be based on non-genomic adaptation and validated in two distinct melanoma models, SK-MEL-28 and A375. Both cell lines have activating BRAF mutations and display metastatic potential. RESULTS: Downregulation of dual specific phosphatases, tumor suppressors, and negative MAPK regulators reengages mitogenic signaling. Upregulation of growth factors, cytokines, and cognate receptors triggers signaling pathways circumventing BRAF blockage. Further, changes in amino acid and one-carbon metabolism support cellular proliferation despite MAPK inhibitor treatment. In addition, treatment-resistant cells upregulate pigmentation and melanogenesis, pathways which partially overlap with MAPK signaling. Upstream regulator analysis discovered significant perturbation in oncogenic forkhead box and hypoxia inducible factor family transcription factors. CONCLUSIONS: The established cellular models offer mechanistic insight into cellular changes and therapeutic targets under inhibitor resistance in malignant melanoma. At a systems biology level, the MAPK pathway undergoes major rewiring while acquiring inhibitor resistance. The outcome of this transcriptional plasticity is selection for a set of transcriptional master regulators, which circumvent upstream targeted kinases and provide alternative routes of mitogenic activation. A fine-woven network of redundant signals maintains similar effector genes allowing for tumor cell survival and malignant progression in therapy-resistant cancer.

A Case-Control Study of the Genetic Variability in Reactive Oxygen Species-Metabolizing Enzymes in Melanoma Risk.

Recent studies have shown that ultraviolet (UV)-induced chemiexcitation of melanin fragments leads to DNA damage; and chemiexcitation of melanin fragments requires reactive oxygen species (ROS), as ROS excite an electron in the melanin fragments. In addition, ROS also cause DNA damages on their own. We hypothesized that ROS producing and metabolizing enzymes were major contributors in UV-driven melanomas. In this case-control study of 349 participants, we genotyped 23 prioritized single nucleotide polymorphisms (SNPs) in nicotinamide adenine dinucleotide phosphate (NADPH) oxidases 1 and 4 (NOX1 and NOX4, respectively), CYBA, RAC1, superoxide dismutases (SOD1, SOD2, and SOD3) and catalase (CAT), and analyzed their associated melanoma risk. Five SNPs, namely rs1049255 (CYBA), rs4673 (CYBA), rs10951982 (RAC1), rs8031 (SOD2), and rs2536512 (SOD3), exhibited significant genotypic frequency differences between melanoma cases and healthy controls. In simple logistic regression, RAC1 rs10951982 (odds ratio (OR) 8.98, 95% confidence interval (CI): 5.08 to 16.44; p < 0.001) reached universal significance (p = 0.002) and the minor alleles were associated with increased risk of melanoma. In contrast, minor alleles in SOD2 rs8031 (OR 0.16, 95% CI: 0.06 to 0.39; p < 0.001) and SOD3 rs2536512 (OR 0.08, 95% CI: 0.01 to 0.31; p = 0.001) were associated with reduced risk of melanoma. In multivariate logistic regression, RAC1 rs10951982 (OR 6.15, 95% CI: 2.98 to 13.41; p < 0.001) remained significantly associated with increased risk of melanoma. Our results highlighted the importance of RAC1, SOD2, and SOD3 variants in the risk of melanoma.

Topically Applied Carvedilol Attenuates Solar Ultraviolet Radiation Induced Skin Carcinogenesis.

In previous studies, the ß-blocker carvedilol inhibited EGF-induced epidermal cell transformation and chemical carcinogen-induced mouse skin hyperplasia. As exposure to ultraviolet (UV) radiation leads to skin cancer, the present study examined whether carvedilol can prevent UV-induced carcinogenesis. Carvedilol absorbs UV like a sunscreen; thus, to separate pharmacological from sunscreen effects, 4-hydroxycarbazole (4-OHC), which absorbs UV to the same degree as carvedilol, served as control. JB6 P+ cells, an established epidermal model for studying tumor promotion, were used for evaluating the effect of carvedilol on UV-induced neoplastic transformation. Both carvedilol and 4-OHC (1 µmol/L) blocked transformation induced by chronic UV (15 mJ/cm2) exposure for 8 weeks. However, EGF-mediated transformation was inhibited by only carvedilol but not by 4-OHC. Carvedilol (1 and 5 µmol/L), but not 4-OHC, attenuated UV-induced AP-1 and NF-κB luciferase reporter activity, suggesting a potential anti-inflammatory activity. In a single-dose UV (200 mJ/cm2)-induced skin inflammation mouse model, carvedilol (10 µmol/L), applied topically after UV exposure, reduced skin hyperplasia and the levels of cyclobutane pyrimidine dimers, IL1ß, IL6, and COX-2 in skin. In SKH-1 mice exposed to gradually increasing levels of UV (50-150 mJ/cm2) three times a week for 25 weeks, topical administration of carvedilol (10 µmol/L) after UV exposure increased tumor latency compared with control (week 18 vs. 15), decreased incidence and multiplicity of squamous cell carcinomas, while 4-OHC had no effect. These data suggest that carvedilol has a novel chemopreventive activity and topical carvedilol following UV exposure may be repurposed for preventing skin inflammation and cancer. Cancer Prev Res; 10(10); 598-606. ©2017 AACR.

Redox-Redux and NADPH Oxidase (NOX): Even More Complicated than We Thought it Might Be.

The NOX (nicotinamide adenine dinucleotide phosphate oxidase) family includes seven unique members that are involved in a multitude of physiological functions, including extensive interaction with UVR and the skin. NOX1 is uniquely present and activated by UVB radiation with biphasic expression of the enzyme immediately and then after a several-hour delay. Specific inhibition of both early and late NOX1 activation leads to evidence of decreased photocarcinogenesis in in vitro keratinocytes and in well-characterized mouse models in which antitumor efficacy has been shown; inhibiting only late NOX activation does not exhibit such effects. These results suggest a crucial function of early NOX activation in transducing a signal for cellular protection after UVB carcinogenesis provocation. We term this an intrinsic cellular ROS priming function for quenching DNA damage and promoting survival. Evolutionally, this type of priming function may be essential for addressing various types of stimuli from adverse environments.

Sex differences in the association of cutaneous melanoma incidence rates and geographic ultraviolet light exposure.

BACKGROUND: Cutaneous melanoma (CM) incidence rates continue to increase, and the reasons are unknown. Previously, we reported a unique age-specific sex difference in melanoma that suggested additional causes other than solar ultraviolet (UV) radiation. OBJECTIVE: This study attempted to understand whether and how UV radiation differentially impacts the CM incidence in men and women. METHODS: CM data and daily UV index (UVI) from 31 cancer registries were collected for association analysis. A second dataset from 42 US states was used for validation. RESULTS: There was no association between log-transformed female CM rates and levels of UVI, but there was a significant association between male rates and UVI and a significant association between overall rates and UVI. The 5-year age-specific rate-UVI association levels (represented by Pearson's coefficient ρ) increased with age in men, but age-specific ρ levels remained low and unchanged in women. The significant rate-UVI association in men and nonassociation in women was validated in a population of white residents of the United States. LIMITATIONS: Confounders, including temperature and latitude, are difficult to separate from UVI. CONCLUSIONS: Ambient UVI appears to be associated with melanoma incidence in males but not in females.