Cilia-Associated Oxysterols Activate Smoothened.

Primary cilia are required for Smoothened to transduce vertebrate Hedgehog signals, but how Smoothened accumulates in cilia and is activated is incompletely understood. Here, we identify cilia-associated oxysterols that promote Smoothened accumulation in cilia and activate the Hedgehog pathway. Our data reveal that cilia-associated oxysterols bind to two distinct Smoothened domains to modulate Smoothened accumulation in cilia and tune the intensity of Hedgehog pathway activation. We find that the oxysterol synthase HSD11ß2 participates in the production of Smoothened-activating oxysterols and promotes Hedgehog pathway activity. Inhibiting oxysterol biosynthesis impedes oncogenic Hedgehog pathway activation and attenuates the growth of Hedgehog pathway-associated medulloblastoma, suggesting that targeted inhibition of Smoothened-activating oxysterol production may be therapeutically useful for patients with Hedgehog-associated cancers.

Diagnostic delay in Hidradenitis suppurativa investigated using data from social media and from statutory health insurances.

BACKGROUND: The chronic inflammatory skin disease hidradenitis suppurativa (HS) leads to severe pain and reduced quality of life. Nonetheless, it often takes years until a correct diagnosis is made. In this analysis, disease-related experiences and pathways of patients with HS were investigated and compared with the physicians' perspective. METHODS: Public posts on forums and social media as well as results of a survey conducted among dermatologists and their patients on the actual medical care reality of HS in Germany were analysed. Furthermore, claims data from German health insurance companies were evaluated. RESULTS: Patients with HS suffer from a 43.3% reduction in working ability. Dermatology (26.5%) was the most frequently consulted specialty, with HS diagnosed predominantly in the inpatient setting (43.8%). Abscesses were described as the most frequent alternative diagnosis in HS patients (53.2%). Patient-reported changes of physicians in dermatology (34.1%) and surgery (42.4%) occurred predominantly within the specialty. Dermatology received most referrals from general practitioners (67.1%), but only 12.1% from surgeons. CONCLUSION: There is an urgent need to reduce the delay in diagnosis and the prolonged burden of disease in patients with HS. Therefore, awareness of the disease, its detection and treatment which goes beyond dermatology should be promoted, if possible as part of medical studies.

Synergistic cross-talk of hedgehog and interleukin-6 signaling drives growth of basal cell carcinoma.

Persistent activation of hedgehog (HH)/GLI signaling accounts for the development of basal cell carcinoma (BCC), a very frequent nonmelanoma skin cancer with rising incidence. Targeting HH/GLI signaling by approved pathway inhibitors can provide significant therapeutic benefit to BCC patients. However, limited response rates, development of drug resistance, and severe side effects of HH pathway inhibitors call for improved treatment strategies such as rational combination therapies simultaneously inhibiting HH/GLI and cooperative signals promoting the oncogenic activity of HH/GLI. In this study, we identified the interleukin-6 (IL6) pathway as a novel synergistic signal promoting oncogenic HH/GLI via STAT3 activation. Mechanistically, we provide evidence that signal integration of IL6 and HH/GLI occurs at the level of cis-regulatory sequences by co-binding of GLI and STAT3 to common HH-IL6 target gene promoters. Genetic inactivation of Il6 signaling in a mouse model of BCC significantly reduced in vivo tumor growth by interfering with HH/GLI-driven BCC proliferation. Our genetic and pharmacologic data suggest that combinatorial HH-IL6 pathway blockade is a promising approach to efficiently arrest cancer growth in BCC patients.

Data on Ocrelizumab Treatment Collected by MS Patients in Germany Using Brisa App.

BACKGROUND: With a rising number of multiple sclerosis (MS) cases and increasing pressure on health systems, digital companion apps like Brisa, designed specifically for people with MS, can play an important role in the patient journey. These apps enable the collection of real-time longitudinal data that are critical to our understanding of the pathophysiology and progression of MS. METHODS: This retrospective, descriptive analysis consists of data from Brisa users who registered between 6 August 2021 and 8 September 2022. Of the unique users, 37.7% (n = 1593) fulfilled the inclusion criteria including information about medication and demographics and tracked one or more symptoms and/or patient-reported outcomes. Users were classified as moderate-efficacy treatment users, high-efficacy treatment users and ocrelizumab users, and the reporting frequency and scores of symptoms and patient-reported outcomes were analyzed. RESULTS: The largest cohort of Brisa users (405) reported treatment with ocrelizumab and were mostly diagnosed 2-5 years before the survey. The most reported MS symptoms were similar between OUs (ocrelizumab users), HETUs (high-efficacy treatment users) and METUs (moderate-efficacy treatment users). OUs on average reported symptoms and answered questionnaires more frequently. Baseline scores between HETUs and OUs were similar, whereas baseline scores of METUs were slightly lower in comparison. In a further analysis of OUs, disability scores increased with age; users aged 26-45 years had higher pain scores than 18-25-year-olds. No significant differences were found in quality of life, bowel control and vision between age groups. CONCLUSION: These findings show that the characteristics of the Brisa cohort are similar to the results of other studies and registries and can provide a representative overview of everyday disease management. Thereby, these results can bridge the gap between clinical research and real patient experience, but they also raise new questions, such as how often the hard-and-early therapy approach is already used and whether baseline characteristics and reasons for choosing a particular treatment contribute to the different outcomes over time. Answering these questions requires further research and analysis.

Shifting from the treat-to-target to the early highly effective treatment approach in patients with multiple sclerosis - real-world evidence from Germany.

Background: While evidence highlights the effectiveness of initiating disease-modifying therapy with a high-efficacy medication for multiple sclerosis (MS) patients with poor prognostic factors, it remains unclear whether this approach has been adopted by a broad range of MS providers in Germany yet. Objective: To assess the adoption of the early highly effective treatment (EHT) compared to the treat-to-target treatment approach with the option of escalating treatment efficacy over time in Germany based on real-world evidence data. Design: Patient-level pharmacy dispensing data from the Permea platform were analysed from 2020 to 2022. Methods: In total, 29,529 therapy beginners (>18 years) were included to analyse shifts in treatment approaches over time and switching behaviour. Medication classification adhered to the German Society of Neurology guidelines and designated fumarates, glatiramer acetate, teriflunomide and interferons as low-efficacy category 1 medications; cladribine and S1P-modulators as medium-efficacy category 2 medications; and alemtuzumab, natalizumab, ocrelizumab, ofatumumab and rituximab (off-label) as high-efficacy category 3 medications. Results: Our results show that 70.0% of patients redeemed their first prescription for category 1 medication, 16.3% for category 2 and 13.7% for category 3 medications. The proportion of prescriptions filled shifted from 2020 to 2022 with a decrease of 14.7% for category 1 drugs and an increase of 12.5% for category 3 drugs. 93.2% of patients stayed on their initially prescribed medication category. 3.2% of category 1 and 3.7% of category 2 therapy beginners escalated to category 3 medication. 3.4% of category 3 medication users de-escalated their treatment to category 1 or category 2. Conclusion: While most individuals started their treatment according to the treat-to-target approach and remained on their initially prescribed medication category, there has been a steadily increasing shift towards the EHT approach since 2020. These insights demonstrate that, while not officially recommended by German guidelines, MS providers increasingly adopt the EHT approach.

Real-world demographic patterns of users of a digital primary prevention service for diabetes.

Rapid urbanization has led to an exponential increase in lifestyle-associated metabolic disorders presenting a huge socioeconomic burden. Waya is a digital prevention program that guides overweight and obese individuals to maintain a healthy lifestyle through exercise, diet, and educational videos. Objectives and aims: We aimed to study the demographic patterns of the Waya cohort and examine the prevalence of diabetes (the most common lifestyle-associated metabolic disorder) and its risk factors in comparison to the GEDA 2014/2015-European Health Interview Survey population. Methods: Waya participants who registered by 1 October 2020 and who answered at least one health survey question were included in this study. Factors such as obesity, hypertension, and diabetes between the two populations were compared using Chi-square test. Results: Of the 837 participants, 86.1% were women. The proportion of obese participants was higher in Waya than in the German Health Update (GEDA) cohort (women: 39.4% vs. 18%, P < 0.05; men: 37.1% vs. 18.3%, P < 0.05), whereas the proportion of participants with hypertension (women: 12.1% vs. 30.9% in GEDA, P < 0.05; men: 22.4% vs. 32.8% in GEDA, P < 0.05) was lower. The proportion of women with diabetes was low in our cohort (3.9% vs. 7% in GEDA, P < 0.05); however, the proportion of men with diabetes remained the same between the two groups. We observed significant differences between the GEDA and Waya cohorts due to changes in the prevalence pattern over time or target bias of the digital program. Conclusion: These findings showcase the usability of Waya in collecting real-world insights, which will be beneficial in monitoring the prevalence of chronic metabolic disorders and associated risk factors over time.

Drug switching in axial spondyloarthritis patients in Germany - a social listening analysis.

Background: Axial spondyloarthritis (axSpA) is a chronic inflammatory disease which primarily affects the axial skeleton resulting in chronic back pain and stiffness. According to the guideline, the first-line treatment includes non-steroidal anti-inflammatory drugs (NSAIDs), conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) and non-pharmacological treatment. Second line treatment involves biological disease-modifying antirheumatic drugs (bDMARDs) such as tumour necrosis factor and interleukin-17 inhibitors. Objectives: The aim of this social media listening research project was to analyse switches of medication and the reasons thereof to gain valuable insights into real-life journeys of patients suffering from axSpA. Methods: Publicly available posts in German-speaking disease-specific forums were scanned for disease-specific keywords and commonly used drugs by axSpA patients on the Permea platform. Posts containing at least two key words were selected and switches between medications were manually labelled. A total of 287 scraped posts between 01 July 2010 and 04 Feb 2022 were analysed. Results: The largest group of described medication switches was initially using bDMARDs. Switches to a different bDMARD, termination of medication and switches to glucocorticoids were most frequently named. Patients on NSAIDs switched to glucocorticoids, a different NSAID or bDMARD, whereas patients on csDMARDs most frequently changed to bDMARDs. In all medication groups the main reason for switching was insufficient efficacy and side effects. Additionally, for the medication groups bDMARDs, csDMARDs and corticosteroids, pregnancy and lactation were given as a reason for switching, whereas patients in the NSAID group never mentioned pregnancy and breastfeeding as a reason for switching treatment. Conclusion: Our analysis shows medication switches based on real-life patient experiences shared with peers in a social listening setting. We also show medication switches differing from advised guidelines. Gathering real-life insights into patients' journey dealing with chronic diseases allows us to understand, and thereby improve patient care and treatment.

The influence of the COVID-19 pandemic on the prescription of multiple sclerosis medication in Germany.

BACKGROUND: Real-word evidence from diverse data sources is increasingly important in terms of generating rapid insights to effectively manage patient populations, especially during major public health disruptions such as the ongoing COVID-19 pandemic. Patients with chronic and inflammatory diseases - such as multiple sclerosis (MS) - were reported to experience potentially negative effects due to the use of immunosuppressive drugs in combination with a COVID-19 infection. In this research, we explored the impact of the COVID-19 pandemic on medication use in patients with MS in Germany. METHODS: Patient-level pharmacy dispensing data from the Permea platform - covering approximately 44% of all community pharmacy dispensing in Germany - were analysed from 2019 - 2021. Longitudinal use patterns of MS medication and antidepressants and patient demographics were assessed. Daily variation in MS medication use was specifically studied around the dates of the first and second lockdowns in Germany. RESULTS: We included data from 539,400 prescriptions which included at least 1 MS drug. The medication data showed a stable level of monthly prescriptions for MS medication at 2.02 ± 0.03 prescriptions per pharmacy during the study period. Although there was a sharp increase in daily prescriptions before the first lockdown (from an average 660.08 ± 137.59 daily prescriptions in the observed period to a maximum dispensing number of 998 daily prescriptions), the overall number of prescriptions remained at pre-pandemic levels (603 ± 90.31 daily prescriptions in 2019). Similar trends were observed for monthly co-prescribed antidepressant use per pharmacy (0.10 ± 0.01 in 2019-0.11 ± 0.02 in 2020). CONCLUSION: Throughout the COVID-19 pandemic, the use of MS medications and co-prescribed antidepressants was stable. These insights from real-world data demonstrate the value of evidence-based insights for managing patient care.

Preclinical study of CD19 detection methods post tafasitamab treatment.

Introduction: Several CD19 targeted antibody-based therapeutics are currently available for patients with diffuse large B-cell lymphoma (DLBCL), including the Fc-modified antibody immunotherapy tafasitamab. This therapeutic landscape warrants the evaluation of potential sequencing approaches. Prior to a subsequent CD19-targeted therapy, CD19 expression on tafasitamab-treated patient biopsy samples may be assessed. However, no standardized methods for its detection are currently available. In this context, selecting a tafasitamab-competing CD19 detection antibody for immunohistochemistry (IHC) or flow cytometry (FC) may lead to misinterpreting epitope masking by tafasitamab as antigen loss or downregulation. Methods: We analyzed a comprehensive panel of commercially available CD19 detection antibody clones for IHC and FC using competition assays on tafasitamab pre-treated cell lines. To remove bound tafasitamab from the cell surface, an acidic dissociation protocol was used. Antibody affinities for CD19 were measured using Surface Plasmon Resonance (SPR) or Bio-Layer Interferometry (BLI). Results: While CD19 was successfully detected on tafasitamab pre-treated samples using all 7 tested IHC antibody clones, all 8 tested FC antibody clones were confirmed to compete with tafasitamab. An acidic dissociation was demonstrated essential to circumvent CD19 masking by tafasitamab and avoid false negative FC results. Discussion: The current study highlights the importance of selecting appropriate CD19 detection tools and techniques for correct interpretation of CD19 expression. The findings presented herein can serve as a guideline to investigators and may help navigate treatment strategies in the clinical setting.

The IMPACT of the COVID-19 Pandemic on Prescription Drug Use in Patients with Psoriasis Vulgaris in Germany.

INTRODUCTION: Real-world evidence (RWE) data is increasingly important to generate rapid insights to effectively manage patient populations. Disruptions like the coronavirus disease 2019 (COVID-19) pandemic may negatively impact the choice of medications used for managing chronic diseases such as psoriasis (PSO). Here, we explored the effect of the COVID-19 pandemic on the sales volumes of treatment guideline-based PSO medication in Germany. METHODS: Patient-level pharmacy dispensing data from the Permea platform, covering approximately 44% of all community pharmacy dispensing in Germany, were analysed from 2019 through to 2021. Patient demographics and PSO indicated medication sales were assessed specifically before and during the pandemic in Germany. RESULTS: We included 6,865,852 sold PSO related drugs from April 2019 to March 2021. Medication sales increased during the pandemic compared with before the pandemic for treatment classes of first-line biological and second-line drugs. The increase was observed across all age groups, but monthly variations could not be detected. Furthermore, we observed increased sales in first-line biological and second-line medications when comparing low to high COVID-19 incidence state. CONCLUSION: Throughout the COVID-19 pandemic the PSO indicated medication sales increased for first-line biological and second-line treatment. This shows that despite the pandemic impact, there continues to be an increase in sales volume for biologics. Only German federal states with intermittently very high COVID-19 incidences show a stagnation in sales volume. The reasons for this need to be investigated in further studies to possibly gain a better understanding of the concerns and uncertainties of patients with PSO.

Correlation and differences of patient-reported outcomes vs. Likert-Rating of MS symptoms in a real-world cohort using a digital patient app.

Background: Multiple Sclerosis (MS) is a chronic and progressive neurological autoimmune disease currently affecting 250,000 individuals in Germany. Patients suffering from the disease can be severely impaired in their day-to-day activities. BRISA is a digital app specifically designed to help MS patients monitor their disease by regularly tracking symptoms. Lengthy and time-consuming questionnaires for patient-reported outcomes (PRO) are the standard method to assess the patients' current condition. Here, we examine whether simplified versions of these questionnaires can provide comparable information regarding individual symptom presentations in BRISA users. Methods: 828 users were included in the analysis. Patients who provided onboarding information and answered at least one questionnaire and the corresponding simplified smiley symptoms assessment were included. Correlation of questionnaire and symptom scores was calculated using Pearson's correlation. Results: Our analysis cohort predominantly consisted of female, 26-55-year-olds. Relapsing-remitting MS (RRMS) was the most common MS type recorded. Most patients were diagnosed 2-5 years ago. Questionnaires regarding fatigue and vision impairment were among the most answered, those regarding bowel movement and sexual satisfaction received fewest responses. Overall, the scores from questionnaires and symptoms correlated positively. Scoring correlation could also be shown across the subgroups divided by gender, age groups, type of MS, and time since diagnosis of the disease. Conclusion: Scores recorded from traditional PRO questionnaires can be reflected more easily as a trend in a simplified scale using smileys. Nevertheless, traditional questionnaires are needed to also maintain a more objective assessment. In conclusion, the patient will benefit most from an adaptive combination of regular traditional PRO questionnaire assessments and simplified symptom recording.

A retrospective real-world observational pilot analysis of Waya: a self-monitoring fitness app in Germany.

The increasing prevalence of lifestyle-driven metabolic disorders poses a heavy burden on the healthcare system. Several low-cost, easily accessible, and effective weight loss interventions are being developed to improve this situation. Waya is one such German digital application that guides users to reach their desired weight in a healthy manner, by monitoring their eating habits and physical activity levels. In this retrospective real-world observational pilot study, we aimed to identify if the use of Waya helps in reducing weight as intended and the underlying factors associated with it. Methods: Data from healthy overweight or obese participants who provided their weight information and answered the short form of the Weight Efficacy Lifestyle Questionnaire and the International Physical Activity Questionnaire activity questionnaires once before the completion of the first module (baseline) were compared with data provided after the beginning of the last module. Age and sex-based distribution were studied and the correlation between nutrition, physical activity, and weight was analyzed. Results: Waya participants showed an improvement in nutritional behavior, physical activity levels, and weight reduction compared with baseline. These changes were independent of age and sex. Weight loss mainly correlated with improvements in nutritional behavior but not physical activity. Conclusion: The results from our pilot study showed that Waya is beneficial in bringing about short-term weight loss mainly through behavioral changes in nutrition. Although physical activity levels improved, its influence on weight loss was not apparent.

Demographic Patterns of MS Patients Using BRISA: An MS-Specific App in Germany.

BACKGROUND: Multiple sclerosis (MS) is a chronic, progressive neurological autoimmune disease impacting quality of life. BRISA is an app designed to help MS patients in Germany track their disease course by symptom-monitoring. This study aimed to understand demographic and health-related characteristics of BRISA users. METHODS: Demographic data provided by 2095 users were analyzed to describe characteristics such as sex, age, type of MS, and medication. The distribution of tracked symptoms based on age and time since diagnosis were studied. Furthermore, the covariance of specific symptom pairs was analyzed. RESULTS: BRISA users are predominantly female and between 26 and 55 years old. Relapsing-remitting MS was the most prevalent form of MS. First-line category 1 drugs were most frequently used, followed by high-efficacy category 3 drugs (e.g., monoclonal antibodies). The relative frequencies of use of category 1 and category 2 drugs (e.g., spingosine-1-phosphate-receptor modulators) significantly altered with time since diagnosis. Fatigue, concentration disorders, tingling, forgetfulness, and pain were the top five symptoms affecting users. CONCLUSION: The results highlight the diversity among MS patients and the need for extensive cohort characterization in the real-world scenario. In-depth analysis could help in identifying novel insights that could aid in disease management.

Basal cell carcinomas acquire secondary mutations to overcome dormancy and progress from microscopic to macroscopic disease.

Basal cell carcinomas (BCCs) frequently possess immense mutational burdens; however, the functional significance of most of these mutations remains unclear. Here, we report that loss of Ptch1, the most common mutation that activates upstream Hedgehog (Hh) signaling, initiates the formation of nascent BCC-like tumors that eventually enter into a dormant state. However, rare tumors that overcome dormancy acquire the ability to hyperactivate downstream Hh signaling through a variety of mechanisms, including amplification of Gli1/2 and upregulation of Mycn. Furthermore, we demonstrate that MYCN overexpression promotes the progression of tumors induced by loss of Ptch1. These findings suggest that canonical mutations that activate upstream Hh signaling are necessary, but not sufficient, for BCC to fully progress. Rather, tumors likely acquire secondary mutations that further hyperactivate downstream Hh signaling in order to escape dormancy and enter a trajectory of uncontrolled expansion.

Tumor Architecture and Notch Signaling Modulate Drug Response in Basal Cell Carcinoma.

Hedgehog (Hh) pathway inhibitors such as vismodegib are highly effective for treating basal cell carcinoma (BCC); however, residual tumor cells frequently persist and regenerate the primary tumor upon drug discontinuation. Here, we show that BCCs are organized into two molecularly and functionally distinct compartments. Whereas interior Hh+/Notch+ suprabasal cells undergo apoptosis in response to vismodegib, peripheral Hh+++/Notch- basal cells survive throughout treatment. Inhibiting Notch specifically promotes tumor persistence without causing drug resistance, while activating Notch is sufficient to regress already established lesions. Altogether, these findings suggest that the three-dimensional architecture of BCCs establishes a natural hierarchy of drug response in the tumor and that this hierarchy can be overcome, for better or worse, by modulating Notch.

Correction: The ratio of STAT1 to STAT3 expression is a determinant of colorectal cancer growth.

[This corrects the article DOI: 10.18632/oncotarget.9315.].

Merkel Cell Polyomavirus Small T Antigen Initiates Merkel Cell Carcinoma-like Tumor Development in Mice.

Merkel cell carcinoma (MCC) tumor cells express several markers detected in normal Merkel cells, a nonproliferative population of neuroendocrine cells that arise from epidermis. MCCs frequently contain Merkel cell polyomavirus (MCPyV) DNA and express viral transforming antigens, sT and tLT, but the role of these putative oncogenes in MCC development, and this tumor's cell of origin, are unknown. Using a panel of preterm transgenic mice, we show that epidermis-targeted coexpression of sT and the cell fate-determinant atonal bHLH transcription factor 1 (ATOH1) leads to development of widespread cellular aggregates, with histology and marker expression mimicking that of human intraepidermal MCC. The MCC-like tumor phenotype was dependent on the FBXW7-binding domain of sT, but not the sT-PP2A binding domain. Coexpression of MCPyV tLT did not appreciably alter the phenotype driven by either sT or sT combined with ATOH1. MCPyV sT, when coexpressed with ATOH1, is thus sufficient to initiate development of epidermis-derived MCC-like tumors in mice. Cancer Res; 77(12); 3151-7. ©2017 AACR.

The ratio of STAT1 to STAT3 expression is a determinant of colorectal cancer growth.

The role of STAT1 and STAT3 for colorectal carcinoma (CRC) development and progression is controversial. We evaluated 414 CRC patient samples on tissue microarrays for differential expression of STAT1 and STAT3 protein levels and correlated ratios with clinical parameters. Concomitant absence of nuclear STAT1 and STAT3 expression was associated with significantly reduced median survival by ≥33 months (p=0.003). To gain insight into underlying mechanisms, we generated four CRC cell lines with STAT3 knockdown. The cell lines harbor different known mutational drivers and were xenografted into SCID mice to analyze the influence of STAT3 on their tumor growth behavior. Experimental downregulation of STAT3 expression had differential, cell-line specific effects on STAT1 expression levels. STAT1 consistently showed nuclear localization irrespective of its tyrosine phosphorylation status. Two characteristic STAT1/3 expression patterns with opposite growth behavior could be distinguished: cell lines with a low STAT1/high STAT3 ratio showed faster tumor growth in xenografts. In contrast, xenografts of cell lines showing high STAT1 and low STAT3 levels grew slower. Importantly, these ratios reflected clinical outcome in CRC patients as well. We conclude that the ratio of STAT1 to STAT3 expression is a key determinant of CRC progression and that STAT1 counteracts pro-tumorigenic STAT3 signaling. Thus, we suggest that the STAT3/STAT1 ratios are better clinical predictors in CRC as compared to STAT3 or STAT1 levels alone.

Basal cell carcinoma preferentially arises from stem cells within hair follicle and mechanosensory niches.

Basal cell carcinoma (BCC) is characterized by frequent loss of PTCH1, leading to constitutive activation of the Hedgehog pathway. Although the requirement for Hedgehog in BCC is well established, the identity of disease-initiating cells and the compartments in which they reside remain controversial. By using several inducible Cre drivers to delete Ptch1 in different cell compartments in mice, we show here that multiple hair follicle stem cell populations readily develop BCC-like tumors. In contrast, stem cells within the interfollicular epidermis do not efficiently form tumors. Notably, we observed that innervated Gli1-expressing progenitors within mechanosensory touch dome epithelia are highly tumorigenic. Sensory nerves activate Hedgehog signaling in normal touch domes, while denervation attenuates touch dome-derived tumors. Together, our studies identify varying tumor susceptibilities among different stem cell populations in the skin, highlight touch dome epithelia as "hot spots" for tumor formation, and implicate cutaneous nerves as mediators of tumorigenesis.