Does polygenic risk influence associations between sun exposure and melanoma? A prospective cohort analysis

Does genetic risk modify the effect of skin screening on melanoma detection rates?

BACKGROUND

Skin screening is associated with higher melanoma detection rates, a potential indicator of overdiagnosis, but it remains possible that this effect is due to confounding by genetic risk.

OBJECTIVES

To compare melanoma incidence among screened vs. unscreened participants within tertiles of genetic risk.

METHODS

We investigated melanoma incidence in the QSkin study, a prospective cohort study which for this analysis comprised 15 283 participants aged 40-69 years with genotype data and no prior history of melanoma. We calculated a polygenic score (PGS) for melanoma. We first calculated the age-standardized rate (ASR) of melanoma within PGS tertiles, and then measured the association between skin examination and melanoma detection by calculating the hazard ratio (HR) and 95% confidence interval (95% CI), overall and within PGS tertiles.

RESULTS

Melanoma incidence increased with PGS (ASR per 100 000 per year): tertile 1 = 442; tertile 2 = 519; tertile 3 = 871. We found that the HRs for all melanomas (i.e. in situ and invasive) associated with skin examination differed slightly across PGS tertiles [age- and sex-adjusted tertile 1 HR 1.88 (95% CI 1.26-2.81); tertile 2 HR 1.70 (95% CI 1.20-2.41); tertile 3 HR 1.96 (95% CI 1.43-2.70); fully adjusted tertile 1 HR 1.14 (95% CI 0.74-1.75); tertile 2 HR 1.21 (95% CI 0.82-1.78); tertile 3 HR 1.41 (95% CI 1.00-1.98)], but these differences were not statistically significant. HRs for in situ melanoma associated with skin examination were similar across PGS tertiles. For invasive melanomas, the point estimates appeared to be highest in PGS tertile 3 in both the minimally adjusted (age, sex) and fully adjusted models; however, these apparent differences were also not statistically significant.

CONCLUSIONS

Genetic risk predicts subsequent melanoma incidence, and is weakly associated with screening behaviour, but it does not explain the higher rate of melanoma detection between screened and unscreened people.

Childhood sunburn and risk of melanoma and non-melanoma skin cancer: a Mendelian randomization study

Previous evidence has suggested that childhood sunburn could be a risk factor for cutaneous malignant melanoma (MM) and non-melanoma skin cancer (NMSC). However, existing observational studies could not reveal the causal associations genetically. This study aimed to investigate whether there was a genetic causal relationship between childhood sunburn and skin cancers. Univariable Mendelian randomization (MR) and Causal Analysis Using Summary Effect analysis was carried out for causal estimates and evaluation for the horizontal pleiotropy. Multivariable MR and the mediation effects analysis were used to test whether the causal associations were mediated by potential confounders. A suggestively significant causal association between childhood sunburn and MM was indicated (OR = 4.74; 95% CI: 1.31-17.19; p = 1.79E-02). Genetically predicted childhood sunburn was significantly associated with increased risk of overall melanoma in situ (MIS) (OR = 4.02; 95% CI: 2.00-8.08; p = 9.40E-05), MIS of face (OR = 18.28; 95% CI: 5.28-63.35; p = 4.59E-06), and MIS of trunk (OR = 7.05; 95% CI: 2.06-24.13; p = 1.88E-03). Similar trends were found for childhood sunburn and NMSC (OR = 8.16; 95% CI: 6.07-10.99; p = 1.53E-20), including both basal cell carcinoma (BCC) (OR = 3.76; 95% CI:2.96-4.77; p = 2.19E-08) and squamous cell carcinoma (SCC) (OR = 7.44; 95% CI: 5.09-10.87; p = 2.19E-08). After adjustment for hair and skin color, facial ageing, vitamin D levels, body mass index, alcohol consumption, and smoking status, childhood sunburn showed an independent association with MIS, MIS of face, MIS of trunk, as well as NMSC, including both BCC and SCC. Mediation analysis showed no significant mediation effect. This study demonstrated a causal relationship between childhood sunburn and the risk of both MM and NMSC, which suggested that enhanced screening and prevention for childhood sunburn could contribute to the early detection and decreased risk of MM and NMSC.

Genetic variants for smoking behaviour and risk of skin cancer

Observational studies have suggested that smoking may increase the risk of cutaneous squamous cell carcinoma (cSCC) while decreasing the risks of basal cell carcinoma (BCC), and melanoma. However, it remains possible that confounding by other factors may explain these associations. The aim of this investigation was to use Mendelian randomization (MR) to test whether smoking is associated with skin cancer, independently of other factors. Two-sample MR analyses were conducted to determine the causal effect of smoking measures on skin cancer risk using genome-wide association study (GWAS) summary statistics. We used the inverse-variance-weighted estimator to derive separate risk estimates across genetic instruments for all smoking measures. A genetic predisposition to smoking initiation was associated with lower risks of all skin cancer types, although none of the effect estimates reached statistical significance (OR 95% CI BCC 0.91, 0.82-1.01; cSCC 0.82, 0.66-1.01; melanoma 0.91, 0.82-1.01). Results for other measures were similar to smoking initiation with the exception of smoking intensity which was associated with a significantly reduced risk of melanoma (OR 0.67, 95% CI 0.51-0.89). Our findings support the findings of observational studies linking smoking to lower risks of melanoma and BCC. However, we found no evidence that smoking is associated with an elevated risk of cSCC; indeed, our results are most consistent with a decreased risk, similar to BCC and melanoma.

Systematic review on gene-sun exposure interactions in skin cancer

BACKGROUND

The risk of skin cancer is determined by environmental factors like ultraviolet radiation (UVR), personal habits like time spent outdoors and genetic factors. This review aimed to survey existing studies in gene-environment (GxE) interaction on skin cancer risk, and report on GxE effect estimates.

METHODS

We searched Embase, Medline (Ovid) and Web of Science (Core Collection) and included only primary research that reported on GxE on the risk of the three most common types of skin cancer: basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma. Quality assessment followed the Newcastle-Ottawa Scale. Meta-analysis was not possible because no two studies examined the same interaction. This review was registered on PROSPERO (CRD42021238064).

RESULTS

In total 260 records were identified after exclusion of duplicates. Fifteen studies were included in the final synthesis-12 used candidate gene approach. We found some evidence of GxE interactions with sun exposure, notably, with MC1R, CAT and NOS1 genes in melanoma, HAL and IL23A in BCC and HAL and XRCC1 in SCC.

CONCLUSION

Sun exposure seems to interact with genes involved in pigmentation, oxidative stress and immunosuppression, indicating that excessive UV exposure might exhaust oxidative defence and repair systems differentially, dependent on genetic make-up. Further research is warranted to better understand skin cancer epidemiology and develop sun exposure recommendations. A genome-wide approach is recommended as it might uncover unknown disease pathways dependent on UV radiation.

The effects of exposure to solar radiation on human health

This assessment by the Environmental Effects Assessment Panel (EEAP) of the Montreal Protocol under the United Nations Environment Programme (UNEP) evaluates the effects of ultraviolet (UV) radiation on human health within the context of the Montreal Protocol and its Amendments. We assess work published since our last comprehensive assessment in 2018. Over the last four years gains have been made in knowledge of the links between sun exposure and health outcomes, mechanisms, and estimates of disease burden, including economic impacts. Of particular note, there is new information about the way in which exposure to UV radiation modulates the immune system, causing both harms and benefits for health. The burden of skin cancer remains high, with many lives lost to melanoma and many more people treated for keratinocyte cancer, but it has been estimated that the Montreal Protocol will prevent 11 million cases of melanoma and 432 million cases of keratinocyte cancer that would otherwise have occurred in the United States in people born between 1890 and 2100. While the incidence of skin cancer continues to rise, rates have stabilised in younger populations in some countries. Mortality has also plateaued, partly due to the use of systemic therapies for advanced disease. However, these therapies are very expensive, contributing to the extremely high economic burden of skin cancer, and emphasising the importance and comparative cost-effectiveness of prevention. Photodermatoses, inflammatory skin conditions induced by exposure to UV radiation, can have a marked detrimental impact on the quality of life of sufferers. More information is emerging about their potential link with commonly used drugs, particularly anti-hypertensives. The eyes are also harmed by over-exposure to UV radiation. The incidence of cataract and pterygium is continuing to rise, and there is now evidence of a link between intraocular melanoma and sun exposure. It has been estimated that the Montreal Protocol will prevent 63 million cases of cataract that would otherwise have occurred in the United States in people born between 1890 and 2100. Despite the clearly established harms, exposure to UV radiation also has benefits for human health. While the best recognised benefit is production of vitamin D, beneficial effects mediated by factors other than vitamin D are emerging. For both sun exposure and vitamin D, there is increasingly convincing evidence of a positive role in diseases related to immune function, including both autoimmune diseases and infection. With its influence on the intensity of UV radiation and global warming, the Montreal Protocol has, and will have, both direct and indirect effects on human health, potentially changing the balance of the risks and benefits of spending time outdoors.

From the trajectory of heritability to the heritability of trajectories

Although compelling and insightful, the proposal by Uchiyama et al. largely neglects within-person change over time, arguably the central topic of interest within their framework. Longitudinal behavioural genetics modelling suggests that the heritability of trajectories is low, in contrast to high and increasing cross-sectional heritability across development. Better understanding of the mechanisms of trajectories remains a crucial outstanding challenge.

Genetically determined cutaneous nevi and risk of cancer

Numerous epidemiologic studies have reported positive associations between higher nevus counts and internal cancers. Whether this association represents a true relationship or is due to bias or confounding by factors associated with both nevus counts and cancer remains unclear. We used germline genetic variants for nevus count to test whether this phenotypic trait is a risk-marker for cancer. We calculated polygenic risk scores (PRS) for nevus counts using individual-level data in the UK Biobank (n = 394 306) and QSkin cohort (n = 17 427). The association between the nevus PRS and each cancer site was assessed using logistic regression adjusted for the effects of age, sex and the first five principal components. In both cohorts, those in the highest nevus PRS quartile had higher risks of melanoma than those in the lowest quartile (UK Biobank odds ratio [OR] 1.42, 95% confidence interval [CI]: 1.29-1.55; QSkin OR 1.58, 95% CI: 1.29-1.94). We also observed increases in risk of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) associated with higher nevus PRS quartiles (BCC UK Biobank OR 1.38, 95% CI: 1.33-1.44; QSkin OR 1.20, 95% CI: 1.05-1.38 and SCC UK Biobank OR 1.41, 95% CI: 1.28-1.55; QSkin OR 1.44, 95% CI: 1.19-1.77). We found no consistent evidence that nevus count PRS were associated with risks of developing internal cancers. We infer that associations between nevus counts and internal cancers reported in earlier observational studies arose because of unmeasured confounding or other biases.

Regional variability of melanoma incidence and prevalence in Hungary. Epidemiological impact of ambient UV radiation and socioeconomic factors

BACKGROUND

The incidence of cutaneous melanoma has risen faster than almost any other type of cancer in the last 50 years. Ultraviolet (UV) radiation and genetic susceptibility are the most important risk factors.

OBJECTIVE

We aimed to determine the epidemiologic indicators of melanoma in Hungary, a country with an estimated population of 9.8 million and an area of 93 030 km2.

METHODS

Anonymized patient records from the National Health Insurance Fund Management covering the entire population were used to determine the incidence and prevalence of melanoma in the counties of Hungary from 2013 to 2017. Altogether 20 030 melanoma cases were identified for inclusion in this study.

RESULTS

The prevalence of melanoma increased over the investigated period and was significantly higher among women than men. The incidence of melanoma stagnated during this period and the incidence rate was the highest among the elderly. Interestingly, the incidence was higher in males in the elderly population, while the incidence was higher in females in the younger (<60 years) population. Geographical variations in ambient UV radiation did not show statistically significant correlation with the regional variability of epidemiologic indicators, probably due to small differences in the number of bright sunshine hours per year between regions. Although Hungary is a relatively small country, we observed regional heterogeneity in socioeconomic factors. Notably, a significant and strong negative correlation was found between single-person household rates and melanoma prevalence.

CONCLUSION

In addition to ambient UV radiation, melanoma incidence and prevalence appear to be related to age, gender and socioeconomic factors.

Genetically determined risk of keratinocyte carcinoma and risk of other cancers

BACKGROUND

Epidemiological studies have consistently documented an increased risk of developing primary non-cutaneous malignancies among people with a history of keratinocyte carcinoma (KC). However, the mechanisms underlying this association remain unclear. We conducted two separate analyses to test whether genetically predicted KC is related to the risk of developing cancers at other sites.

METHODS

In the first approach (one-sample), we calculated the polygenic risk scores (PRS) for KC using individual-level data in the UK Biobank (n = 394 306) and QSkin cohort (n = 16 896). The association between the KC PRS and each cancer site was assessed using logistic regression. In the secondary (two-sample) approach, we used genome-wide association study (GWAS) summary statistics identified from the most recent GWAS meta-analysis of KC and obtained GWAS data for each cancer site from the UK-Biobank participants only. We used inverse-variance-weighted methods to estimate risks across all genetic variants.

RESULTS

Using the one-sample approach, we found that the risks of cancer at other sites increased monotonically with KC PRS quartiles, with an odds ratio (OR) of 1.16, 95% confidence interval (CI): 1.13-1.19 for those in KC PRS quartile 4 compared with those in quartile 1. In the two-sample approach, the pooled risk of developing other cancers was statistically significantly elevated, with an OR of 1.05, 95% CI: 1.03-1.07 per doubling in the odds of KC. We observed similar trends of increasing cancer risk with increasing KC PRS in the QSkin cohort.

CONCLUSION

Two different genetic approaches provide compelling evidence that an instrumental variable for KC constructed from genetic variants predicts the risk of cancers at other sites.

Environmental effects of stratospheric ozone depletion, UV radiation and interactions with climate change: UNEP Environmental Effects Assessment Panel, update 2019

This assessment, by the United Nations Environment Programme (UNEP) Environmental Effects Assessment Panel (EEAP), one of three Panels informing the Parties to the Montreal Protocol, provides an update, since our previous extensive assessment (Photochem. Photobiol. Sci., 2019, 18, 595-828), of recent findings of current and projected interactive environmental effects of ultraviolet (UV) radiation, stratospheric ozone, and climate change. These effects include those on human health, air quality, terrestrial and aquatic ecosystems, biogeochemical cycles, and materials used in construction and other services. The present update evaluates further evidence of the consequences of human activity on climate change that are altering the exposure of organisms and ecosystems to UV radiation. This in turn reveals the interactive effects of many climate change factors with UV radiation that have implications for the atmosphere, feedbacks, contaminant fate and transport, organismal responses, and many outdoor materials including plastics, wood, and fabrics. The universal ratification of the Montreal Protocol, signed by 197 countries, has led to the regulation and phase-out of chemicals that deplete the stratospheric ozone layer. Although this treaty has had unprecedented success in protecting the ozone layer, and hence all life on Earth from damaging UV radiation, it is also making a substantial contribution to reducing climate warming because many of the chemicals under this treaty are greenhouse gases.