Intravenous lidocaine for refractory pain in patients with pancreatic ductal adenocarcinoma and chronic pancreatitis (LIDOPAN): a multicenter prospective non-randomized pilot study.

INTRODUCTION: Refractory pain is a major clinical problem in patients with pancreatic ductal adenocarcinoma (PDAC) and chronic pancreatitis (CP). New, effective therapies to reduce pain are urgently needed. Intravenous lidocaine is used in clinical practice in patients with PDAC and CP, but its efficacy has not been studied prospectively. METHODS: Multicentre prospective non-randomized pilot study including patients with moderate or severe pain (NRS ≥ 4) associated with PDAC or CP in 5 Dutch centers. An intravenous lidocaine bolus of 1.5mg/kg, was followed by continuous infusion at 1.5 mg/kg/hour. The dose was raised every 15 minutes until treatment response (up to a maximum 2mg/kg/hour) and consecutively administered for two hours. Primary outcome was the mean difference in pain severity, pre-infusion and the first day after (Brief Pain Inventory [BPI] scale 1-10). A BPI decrease ≥ 1.3 points was considered clinically relevant. RESULTS: Overall, 30 patients were included, 19 with PDAC (63%) and 11 with CP (37%). The mean difference in BPI at day one was 1.1 (SD±1.3) points for patients with PDAC and 0.5 (SD±1.7) for CP patients. A clinically relevant decrease in BPI on day one was reported in 9/29 patients (31%), this response lasted up to one month. No serious complications were reported, and only three minor complications (vertigo, nausea, tingling of mouth). Treatment with lidocaine did not impact quality of life. CONCLUSION: Intravenous lidocaine in patients with painful PDAC and CP did not show an overall clinically relevant reduction of pain. However, this pilot study shows that the treatment is feasible in this patient group, and had a positive effect in a third of patients which lasted up to a month with only minor side effects. To prove or exclude the efficacy of intravenous lidocaine, the study should be performed in a study with a greater sample size and less heterogeneous patient group.

Optimising SME Potential in Modern Healthcare Systems: Challenges, Opportunities and Policy Recommendations.

The expansion of European small and medium-sized enterprises (SMEs) into the healthcare innovation arena suggests that this should be an important EU policy priority that can significantly benefit the economy, society and citizens, including patients. Deepening and widening of Europe's SMEs' growth and activities is part of the EU objectives as set out by the European Commission in its Communications "Small Business Act" for Europe [1] and "Small Business, Big World" [2]. However, innovative healthcare SMEs have struggled to get traction despite the sector being worth more than EUR 250 billion. The 1991 Maastricht Treaty gave the Union new competences in public health and more scope for cross-border cooperation in this area [3]. Nevertheless, health initiatives here have tripped over each other, due to the fact that the delivery of healthcare is a national competence [4]. As such, EU healthcare-driven policy has never truly found its footing as a singular policy area despite the fact that a tenth of the EU's GDP is spent on healthcare and more than 17 million people are employed in Europe in this sector [5]. Taking into account the necessity of bringing innovation into healthcare, and the willingness of SMEs to undertake the risk to be at the forefront of it, there is a need for a renewed effort to support SMEs so as to provide solutions for citizens and patients throughout the bloc in different healthcare settings [6]. This policy paper brings together two separate strands of analysis: firstly, a policy review of the main challenges and opportunities; secondly, a proposal for policy recommendations.

MECP2 variation in Rett syndrome-An overview of current coverage of genetic and phenotype data within existing databases.

Rett syndrome (RTT) is a monogenic rare disorder that causes severe neurological problems. In most cases, it results from a loss-of-function mutation in the gene encoding methyl-CPG-binding protein 2 (MECP2). Currently, about 900 unique MECP2 variations (benign and pathogenic) have been identified and it is suspected that the different mutations contribute to different levels of disease severity. For researchers and clinicians, it is important that genotype-phenotype information is available to identify disease-causing mutations for diagnosis, to aid in clinical management of the disorder, and to provide counseling for parents. In this study, 13 genotype-phenotype databases were surveyed for their general functionality and availability of RTT-specific MECP2 variation data. For each database, we investigated findability and interoperability alongside practical user functionality, and type and amount of genetic and phenotype data. The main conclusions are that, as well as being challenging to find these databases and specific MECP2 variants held within, interoperability is as yet poorly developed and requires effort to search across databases. Nevertheless, we found several thousand online database entries for MECP2 variations and their associated phenotypes, diagnosis, or predicted variant effects, which is a good starting point for researchers and clinicians who want to provide, annotate, and use the data.

Circulating concentrations of vitamin D in relation to pancreatic cancer risk in European populations.

Evidence from in vivo, in vitro and ecological studies are suggestive of a protective effect of vitamin D against pancreatic cancer (PC). However, this has not been confirmed by analytical epidemiological studies. We aimed to examine the association between pre-diagnostic circulating vitamin D concentrations and PC incidence in European populations. We conducted a pooled nested case-control study within the European Prospective Investigation into Cancer and Nutrition (EPIC) and the Nord-Trøndelag Health Study's second survey (HUNT2) cohorts. In total, 738 primary incident PC cases (EPIC n = 626; HUNT2 n = 112; median follow-up = 6.9 years) were matched to 738 controls. Vitamin D [25(OH)D2 and 25(OH)D3 combined] concentrations were determined using isotope-dilution liquid chromatography-tandem mass spectrometry. Conditional logistic regression models with adjustments for body mass index and smoking habits were used to estimate incidence rate ratios (IRRs) and 95% confidence intervals (95%CI). Compared with a reference category of >50 to 75 nmol/L vitamin D, the IRRs (95% CIs) were 0.71 (0.42-1.20); 0.94 (0.72-1.22); 1.12 (0.82-1.53) and 1.26 (0.79-2.01) for clinically pre-defined categories of ≤25; >25 to 50; >75 to 100; and >100 nmol/L vitamin D, respectively (p for trend = 0.09). Corresponding analyses by quintiles of season-standardized vitamin D concentrations also did not reveal associations with PC risk (p for trend = 0.23). Although these findings among participants from the largest combination of European cohort studies to date show increasing effect estimates of PC risk with increasing pre-diagnostic concentrations of vitamin D, they are not statistically significant.

Policy Making in Newborn Screening Needs a Structured and Transparent Approach.

PURPOSE: Newborn bloodspot screening (NBS) programs have expanded significantly in the past years and are expected to expand further with the emergence of genetic technologies. Historically, NBS expansion has often occurred following ad hoc consideration of conditions, instead of a structured and transparent approach. In this review, we explore issues pertinent to NBS policy making, through the lens of the policy cycle: (a) agenda setting, (b) policy advice, (c) policy decision, (d) implementation, and (e) evaluation. METHODS: A literature search was conducted to gather information on the elements specific to NBS and its policy making process. RESULTS: The review highlighted two approaches to nominate a condition: a structured approach through horizon scanning; and an ad hoc process. For assessment of a condition, there was unanimous support for a robust process based on criteria. While the need to assess harms and benefits was a repeated theme in the articles, there is no agreed-upon threshold for benefit in decision-making. Furthermore, the literature was consistent in its recommendation for an overarching, independent, multidisciplinary group providing recommendations to government. An implementation plan focusing on the different levels on which NBS operates and the information needed on each level is essential for successful implementation. Continuously monitoring, and improving a program is vital, particularly following the implementation of screening for a new condition. An advisory committee could advise on implementation, development, review, modification, and cessation of (parts of) NBS. CONCLUSION: The results highlight that there are a wave of issues facing NBS programs that policy makers must take into account when developing policy processes. What conditions to screen, and the technologies used in NBS, are both up for debate.

Specific polymorphisms in the vitamin D metabolism pathway are not associated with susceptibility to Chlamydia trachomatis infection in humans.

Chlamydia trachomatis is the most common sexually transmitted bacterium worldwide. Its often asymptomatic course of infection increases chances of transmission, and increases risk of late complications. Genetic variations in the host immune system are known to impact the course of infections. Recent studies have shown a positive impact of vitamin D on the regulation of the immune system. This study assesses the impact of eight polymorphisms in five genes [VDR (rs1544410 G > A, rs2228570 C > T), CYP27B1 (rs10877012 G > T), DHCR7 (rs7944926 G > A, rs3829251 G > A), GC (rs3755967) and CYP2R1 (rs10741657 G > A, rs2060793 G > A)] on susceptibility to Chlamydia infections in humans. These polymorphisms could influence protein expression or function, and thus influence the immune system. Samples of women visiting the STD outpatient clinic in South Limburg were genotyped using the Roche Lightcycler 480. In this study, we did not observe statistically significant differences between the genotype distributions of these polymorphisms in women with or without a Chlamydia infection. This suggests that VDR, CYP27B1, DHCR7, GC and CYP2R1 do not affect the susceptibility to Chlamydia infections. However, due to its pleiotropic nature in the immune system a role for the vitamin D pathway may not be excluded from the whole clinical course of Chlamydia infections (e.g. late complications), and further research is required.

Preferences for genetic testing for colorectal cancer within a population-based screening program: a discrete choice experiment.

This study explored individuals' preferences for genetic testing for colorectal cancer (CRC) in a screening situation and their willingness to participate in genetic testing for Lynch syndrome, familial adenomatous polyposis (FAP), and familial colorectal cancer (FCC). For that purpose, 532 respondents aged 55-65 years completed a Discrete Choice Experiment. Using panel latent class models, the preferences for two screening situation characteristics (the probability of being genetically predisposed and the probability of developing CRC) and screening test characteristics (the frequency of preventive colonoscopies and CRC survival) were estimated. Based on these preferences, respondents' willingness to participate in the three screening initiatives was estimated. Lower-educated respondents and respondents who express serious anxiety and worries found colonoscopy frequency and the probability of developing CRC relatively more important and survival relatively less important compared with higher-educated respondents and respondents who express no anxiety and worries. These differences in preferences resulted in opposite preferences for participation in FCC and FAP screening. In conclusion, the general population is willing to participate in genetic screening for CRC. If individuals are suspected of genetic or familial CRC, they should at least be informed about their increased risk of being genetically predisposed and about the importance of participating in all preventive follow-up colonoscopies in order to maximize survival.

The impact of personalized medicine of Type 2 diabetes mellitus in the global health context.

Advances in the fields of genomic sciences have given rise to personalized medicine. This new paradigm draws upon a patient's genetic and metabolic makeup in order to tailor diagnostics and treatment. Personalized medicine holds remarkable promises to improve prevention and management of chronic diseases of global relevance, such as Type 2 diabetes mellitus (T2DM). This review article aims at summarizing the evidence from genome-based sciences on T2DM risk and management in different populations and in the Global Health context. Opinions from leading experts in the field were also included. Based on these findings, strengths and weaknesses of personalized approach to T2DM in a global context are delineated. Implications for future research and implementation on that subject are discussed.

Dietary fat intake and development of specific breast cancer subtypes.

We prospectively evaluated fat intake as predictor of developing breast cancer (BC) subtypes defined by estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor 2 receptor (HER2), in a large (n = 337327) heterogeneous cohort of women, with 10062 BC case patients after 11.5 years, estimating BC hazard ratios (HRs) by Cox proportional hazard modeling. High total and saturated fat were associated with greater risk of ER(+)PR(+) disease (HR = 1.20, 95% confidence interval [CI] = 1.00 to 1.45; HR = 1.28, 95% CI = 1.09 to 1.52; highest vs lowest quintiles) but not ER(-)PR(-) disease. High saturated fat was statistically significantly associated with greater risk of HER2(-) disease. High saturated fat intake particularly increases risk of receptor-positive disease, suggesting saturated fat involvement in the etiology of this BC subtype.

Hepatocellular carcinoma risk factors and disease burden in a European cohort: a nested case-control study.

BACKGROUND: To date, no attempt has been made to systematically determine the apportionment of the hepatocellular carcinoma burden in Europe or North America among established risk factors. METHODS: Using data collected from 1992 to 2006, which included 4,409,809 person-years in the European Prospective Investigation into Cancer and nutrition (EPIC), we identified 125 case patients with hepatocellular carcinoma, of whom 115 were matched to 229 control subjects. We calculated odds ratios (ORs) for the association of documented risk factors for hepatocellular carcinoma with incidence of this disease and estimated their importance in this European cohort. RESULTS: Chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) infection (OR = 9.10, 95% confidence interval [CI] = 2.10 to 39.50 and OR = 13.36, 95% CI = 4.11 to 43.45, respectively), obesity (OR = 2.13, 95% CI = 1.06 to 4.29), former or current smoking (OR = 1.98, 95% CI = 0.90 to 4.39 and OR = 4.55, 95% CI = 1.90 to 10.91, respectively), and heavy alcohol intake (OR = 1.77, 95% CI = 0.73 to 4.27) were associated with hepatocellular carcinoma. Smoking contributed to almost half of all hepatocellular carcinomas (47.6%), whereas 13.2% and 20.9% were attributable to chronic HBV and HCV infection, respectively. Obesity and heavy alcohol intake contributed 16.1% and 10.2%, respectively. Almost two-thirds (65.7%, 95% CI = 50.6% to 79.3%) of hepatocellular carcinomas can be accounted for by exposure to at least one of these documented risk factors. CONCLUSIONS: Smoking contributed to more hepatocellular carcinomas in this Europe-wide cohort than chronic HBV and HCV infections. Heavy alcohol consumption and obesity also contributed to sizeable fractions of this disease burden. These contributions may be underestimates because EPIC volunteers are likely to be more health conscious than the general population.

Endogenous sex steroids and risk of cervical carcinoma: results from the EPIC study.

BACKGROUND: Epidemiologic data and animal models suggest that, despite the predominant role of human papillomavirus infection, sex steroid hormones are also involved in the etiology of invasive cervical carcinoma (ICC). METHODS: Ninety-nine ICC cases, 121 cervical intraepithelial neoplasia grade 3 (CIN3) cases and 2 control women matched with each case for center, age, menopausal status and blood collection-related variables, were identified in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Circulating levels of testosterone (T) and estradiol (E(2)); dehydroepiandrosterone sulfate (DHEAS); progesterone (premenopausal women); and sex hormone-binding globulin (SHBG) were measured using immunoassays. Levels of free (f) T and E(2) were calculated from absolute concentrations of T, E(2), and SHBG. Odds ratios (ORs) and 95% confidence intervals (CI) were computed using regularized conditional logistic regression. RESULTS: Among premenopausal women, associations with ICC were observed for fT (OR for highest vs. lowest tertile = 5.16, 95% CI, 1.50-20.1). SHBG level was associated with a significant downward trend in ICC risk. T, E(2), fE(2), and DHEAS showed nonsignificant positive association with ICC. Progesterone was uninfluential. Among postmenopausal women, associations with ICC were found for T (OR = 3.14; 95% CI, 1.21-9.37), whereas E(2) and fT showed nonsignificant positive association. SHBG level was unrelated to ICC risk in postmenopausal women. No associations between any hormone and CIN3 were detected in either pre- or postmenopausal women. CONCLUSIONS: Our findings suggest for the first time that T and possibly E(2) may be involved in the etiology of ICC. IMPACT: The responsiveness of cervical tumors to hormone modulators is worth exploring.

Functional foods and dietary supplements: products at the interface between pharma and nutrition.

It is increasingly recognized that most chronic diseases of concern today are multifactorial in origin. To combat such diseases and adverse health conditions, a treatment approach where medicines and nutrition complement each other may prove to be the most successful. Within nutrition, apart from (disease-related) dietetic regimes, an increasing number of functional foods and dietary supplements, each with their own health claim, are marketed. These food items are considered to be positioned between traditional foods and medicines at the so-called 'Pharma-Nutrition Interface'. This paper encompasses aspects related to the regulatory framework and health claims of functional foods and dietary supplements. The use of functional foods or dietary supplements may offer opportunities to reduce health risk factors and risk of diseases, both as monotherapy and in combination with prescription drugs. Nevertheless, the potential caveats of these products should not be overlooked. These caveats include the increased risk for food-drug interactions due to the elevated amounts of specific functional ingredients in the diet, and the stimulation of self-medication potentially resulting in lower adherence to drug therapy. Health technology assessments should be used more to compare the cost-effectiveness and benefit-risk ratios of drugs, functional foods and dietary supplements, and to evaluate the added value of functional foods or dietary supplements to drug therapy.

Costs and health effects of adding functional foods containing phytosterols/-stanols to statin therapy in the prevention of cardiovascular disease.

The present modelling study aimed to evaluate if and by how much functional foods containing phytosterols/-stanols add to the benefits of statins in the prevention of cardiovascular disease in terms of cost-effectiveness. Long-term health effects, measured as quality-adjusted life-years gained, and costs for scenarios with additional phytosterol/-stanol use were compared to scenarios without extra use. Phytosterols/-stanols were given only to persons who were eligible for use according to their 10-year absolute risk of fatal cardiovascular disease (SCORE-risk). Intake levels and discontinuation rates as observed in daily practice were included in the model. Two situations were compared: 1) A real-life situation in which persons at high SCORE-risk were identified through clinical case-finding and, 2) A theoretical maximum situation where universal screening was implemented resulting in known SCORE-risks for the whole Dutch population aged 35-75 years (8.4 million people). Sensitivity analyses were performed for variations in the cholesterol-lowering effect and intake level of phytosterols/-stanols, indirect health care costs, time horizon and discount rates. At the model's start year, a total of 1.0 (real-life situation) to 3.3 (maximum situation) million persons qualified for phytosterol/-stanol use based on their SCORE-risk (both statin users and statin non-users). Over the model's time horizon, this resulted in a gain of 2700 to 16,300 quality-adjusted life-years, and yielded cost-effectiveness ratios that ranged between €92,000 and €203,000 per quality-adjusted life-year. This simulation study showed that the cost-effectiveness of phytosterols/-stanols as monotherapy and as add-on to statins is above thresholds for cost-effectiveness, generally ranging between €20,000 and €50,000, and is thus a non-cost-effective strategy to reduce cardiovascular disease.

Influence of the use of functional foods enriched with phytosterols/-stanols on adherence to statin therapy.

PURPOSE: Subjects using functional foods with approved health claims may be more likely to be non-adherent with prescribed drug therapy. This study aimed to assess the influence of the use of phytosterol/-stanol-enriched functional foods on adherence to statin therapy among patients initiating treatment. METHODS: We used data from the statin intervention research project, a randomized controlled trial aimed at improving adherence to statins. In the trial, new statin users were randomized to receive either usual care or extensive pharmaceutical care consisting of five individual counseling sessions. Customary use of phytosterol/-stanol-enriched products was identified by questionnaires filled out by all participants. Automated pharmacy-dispensing records were used to assess adherence in terms of discontinuation of therapy and the medication possession ratio. Analyses were performed for the overall population, as well as stratified for receiving pharmaceutical or usual care. RESULTS: The use of functional foods enriched with phytosterols/-stanols was not related to discontinuation of statin therapy, neither in the overall population (overall population adjusted hazard rate ratio (HR(adj)): 0.80 [95%CI: 0.59-1.08]), nor when stratified by randomization arm (pharmaceutical care HR(adj): 0.77 [95%CI: 0.49-1.23]); usual care HR(adj): 0.81 [95%CI: 0.54-1.21]). The median medication possession ratio was significantly lower in users of phytosterols/-stanols in the usual care group, but the difference was not clinically relevant. CONCLUSIONS: Customary use of phytosterol/-stanol-enriched functional foods did not affect adherence to statins in new users that are well informed on the beneficial effects of statin therapy. In daily medical practice, general practitioners and pharmacists should urge subjects not to take phytosterol/-stanol-enriched functional foods as replacement for their prescribed medication.

Genetic variability of the fatty acid synthase pathway is not associated with prostate cancer risk in the European Prospective Investigation on Cancer (EPIC).

A western lifestyle, characterised by low rates of energy expenditure and a high-energy diet rich in animal protein, saturated fats and refined carbohydrates, is associated with high incidence of prostate cancer in men. A high-energy nutritional status results in insulin/IGF signalling in cells, which in turn stimulates synthesis of fatty acids. We investigated whether the genetic variability of the genes belonging to the fatty acid synthesis pathway is related to prostate cancer risk in 815 prostate cancer cases and 1266 controls from the European Prospective Investigation on Cancer (EPIC). Using a tagging approach and selecting 252 SNPs in 22 genes, we covered all the common genetic variation of this pathway. None of the SNPs reached statistical significance after adjusting for multiple comparisons. Common SNPs in the fatty acid synthase pathway are not major contributors to prostate cancer risk.

Estimated number of new cancer cases attributable to infection in the Netherlands in 2003.

Several infectious diseases are considered to play a causal role in cancer aetiology. It is estimated that in 2003 in the Netherlands at maximum 2553 new cancer cases (3.5% of all new cancer cases) were attributable to infection. This is considerably lower than globally (17.8%) and in developed countries in general (7.7%), as previously estimated by Parkin. Most likely the explanation is that the prevalence of infections in the Netherlands is lower. Infectious agents that cause the highest number of cancer cases in the Netherlands, as well as globally, are Helicobacter pylori (stomach cancer) and the human papilloma virus (mainly cervical cancer).

Opposing associations of serum n-3 and n-6 polyunsaturated fatty acids with colorectal adenoma risk: an endoscopy-based case-control study.

Several human and animal studies have shown that n-3 polyunsaturated fatty acids (PUFA) might be associated with a decreased risk, whereas other studies showed that n-6 PUFA may be associated with an increased risk of colorectal cancer. However, results from these studies are not consistent. We evaluated the associations between serum n-3 and n-6 PUFA levels and colorectal adenoma risk in an endoscopy-based case-control study, conducted in The Netherlands between 1997 and 2002. We included 363 cases of colorectal adenomas and 498 adenoma-free controls. Serum fatty acids were measured in cholesteryl esters. Logistic regression models were used to calculate odds ratios (OR), which were adjusted for age, gender and alcohol intake. Total serum n-3 PUFA levels were inversely associated with colorectal adenoma risk, the OR comparing the third tertile with the first tertile was 0.67 [95% confidence interval (CI) 0.46-0.96, p for trend = 0.03]. Serum eicosapentaenoic acid (EPA; C20:5n-3) and docosahexaenoic acid (DHA; C22:6n-3) and the n-3/n-6 ratio were inversely associated with colorectal adenoma risk, but these were not statistically significant. In contrast, the risk of colorectal adenomas was increased by total n-6 PUFA with an OR of 1.68 (95% CI, 1.17-2.42, p for trend = 0.006) and by linoleic acid (LA; C18:2n-6) with an OR of 1.65 (95% CI, 1.15-2.38, p for trend = 0.007). This is the first observational study that simultaneously finds an inverse association of serum n-3 PUFA and a positive association of n-6 PUFA with colorectal adenoma risk.

Comparative gene expression profiling in two congenic mouse strains following Bordetella pertussis infection.

BACKGROUND: Susceptibility to Bordetella pertussis infection varies widely. These differences can partly be explained by genetic host factors. HcB-28 mice are more resistant to B. pertussis infection than C3H mice, which could partially be ascribed to the B. pertussis susceptibility locus-1 (Bps1) on chromosome 12. The presence of C57BL/10 genome on this locus instead of C3H genome resulted in a decreased number of bacteria in the lung. To further elucidate the role of host genetic factors, in particular in the Bps1 locus, in B. pertussis infection, and to identify candidate genes within in this region, we compared expression profiles in the lungs of the C3H and HcB-28 mouse strains following B. pertussis inoculation. Twelve and a half percent of the genomes of these mice are from a different genetic background. RESULTS: Upon B. pertussis inoculation 2,353 genes were differentially expressed in the lungs of both mouse strains. Two hundred and six genes were differentially expressed between the two mouse strains, but, remarkably, none of these were up- or down-regulated upon B. pertussis infection. Of these 206 genes, 17 were located in the Bps1 region. Eight of these genes, which showed a strong difference in gene expression between the two mouse strains, map to the immunoglobulin heavy chain complex (Igh). CONCLUSION: Gene expression changes upon B. pertussis infection are highly identical between the two mouse strains despite the differences in the course of B. pertussis infection. Because the genes that were differentially regulated between the mouse strains only showed differences in expression before infection, it appears likely that such intrinsic differences in gene regulation are involved in determining differences in susceptibility to B. pertussis infection. Alternatively, such genetic differences in susceptibility may be explained by genes that are not differentially regulated between these two mouse strains. Genes in the Igh complex, among which Igh-1a/b, are likely candidates to explain differences in susceptibility to B. pertussis. Thus, by microarray analysis we significantly reduced the number of candidate susceptibility genes within the Bps1 locus. Further work should establish the role of the Igh complex in B. pertussis infection.

Induction of nevi and skin tumors in Ink4a/Arf Xpa knockout mice by neonatal, intermittent, or chronic UVB exposures.

Nevi and melanomas correlate to childhood and intermittent solar UV exposure, xeroderma pigmentosum patients run increased risk, and p16(Ink4a) expression is often lost in malignant progression. To ascertain the effect of these risk factors, pigmented hairless Ink4a/Arf-, Xpa- knockout mice were subjected to various combinations of neonatal [7,12-dimethylbenz(a)anthracene (DMBA) or UVB exposure] and adult treatments (12-O-tetradecanoylphorbol-13-acetate or subacute daily UVB exposure or intermittent overexposure). Nevi occurred earliest, grew largest, and were most numerous in mice exposed to DMBA followed by intermittent UVB overexposure [effect of six minimal edemal doses (MED), 1 x /2 weeks > 4 MED 1 x /wk]. Neonatal UV exposure enhanced nevus induction but lost its effect after 200 days. The Xpa(-/-) mice proved exquisitely sensitive to UV-driven nevus induction, indicating the involvement of pyrimidine dimer DNA lesions, but Xpa(+/+) mice developed many more nevi (>40 per mouse) at high UV dosages not tolerated by Xpa(-/-) mice. Ink4a/Arf(-/-) mice developed most skin tumors faster, but surprisingly developed nevi slower than their heterozygous counterparts especially after neonatal UV exposure. Despite raising >1,600 nevi, only six melanomas arose in our experiments with Ink4a/Arf knockout mice (five of which in Xpa(+/+) mice at high UV dosages). In contrast to human nevi, these nevi lacked hotspot mutations in Braf or Ras genes, possibly explaining the lack of malignant progression in the Ink4a/Arf(-/-) mice. Hence, although our experiments did not effectively emulate human melanoma, they provided clear evidence that intermittent UV overexposure strongly stimulates and the Ink4a/Arf(-/-) genotype may actually impair nevus development.