The genomic landscapes of individual melanocytes from human skin.

Every cell in the human body has a unique set of somatic mutations, but it remains difficult to comprehensively genotype an individual cell1. Here we describe ways to overcome this obstacle in the context of normal human skin, thus offering a glimpse into the genomic landscapes of individual melanocytes from human skin. As expected, sun-shielded melanocytes had fewer mutations than sun-exposed melanocytes. However, melanocytes from chronically sun-exposed skin (for example, the face) had a lower mutation burden than melanocytes from intermittently sun-exposed skin (for example, the back). Melanocytes located adjacent to a skin cancer had higher mutation burdens than melanocytes from donors without skin cancer, implying that the mutation burden of normal skin can be used to measure cumulative sun damage and risk of skin cancer. Moreover, melanocytes from healthy skin commonly contained pathogenic mutations, although these mutations tended to be weakly oncogenic, probably explaining why they did not give rise to discernible lesions. Phylogenetic analyses identified groups of related melanocytes, suggesting that melanocytes spread throughout skin as fields of clonally related cells that are invisible to the naked eye. Overall, our results uncover the genomic landscapes of individual melanocytes, providing key insights into the causes and origins of melanoma.

Identifying critical quality metrics in Mohs Surgery: A national expert consensus process.

BACKGROUND: Amid a movement toward value-based healthcare, increasing emphasis has been placed on outcomes and cost of medical services. To define and demonstrate the quality of services provided by Mohs surgeons, it is important to identify and understand the key aspects of Mohs micrographic surgery (MMS) that contribute to excellence in patient care. OBJECTIVE: The purpose of this study is to develop and identify a comprehensive list of metrics in an initial effort to define excellence in MMS. METHODS: Mohs surgeons participated in a modified Delphi process to reach a consensus on a list of metrics. Patients were administered surveys to gather patient perspectives. RESULTS: Twenty-four of the original 66 metrics met final inclusion criteria. Broad support for the initiative was obtained through physician feedback. LIMITATIONS: Limitations of this study include attrition bias across survey rounds and participation at the consensus meeting. Furthermore, the list of metrics is based on expert consensus instead of quality evidence-based outcomes. CONCLUSION: With the goal of identifying metrics that demonstrate excellence in performance of MMS, this initial effort has shown that Mohs surgeons and patients have unique perspectives and can be engaged in a data-driven approach to help define excellence in the field of MMS.

αE-catenin inhibits a Src-YAP1 oncogenic module that couples tyrosine kinases and the effector of Hippo signaling pathway.

Cell-cell adhesion protein αE-catenin inhibits skin squamous cell carcinoma (SCC) development; however, the mechanisms responsible for this function are not completely understood. We report here that αE-catenin inhibits ß4 integrin-mediated activation of SRC tyrosine kinase.SRCis the first discovered oncogene, but the protein substrate critical for SRC-mediated transformation has not been identified. We found that YAP1, the pivotal effector of the Hippo signaling pathway, is a direct SRC phosphorylation target, and YAP1 phosphorylation at three sites in its transcription activation domain is necessary for SRC-YAP1-mediated transformation. We uncovered a marked increase in this YAP1 phosphorylation in human and mouse SCC tumors with low/negative expression of αE-catenin. We demonstrate that the tumor suppressor function of αE-catenin involves negative regulation of the ß4 integrin-SRC signaling pathway and that SRC-mediated phosphorylation and activation of YAP1 are an alternative to the canonical Hippo signaling pathway that directly connect oncogenic tyrosine kinase signaling with YAP1.

Enhanced metastatic risk assessment in cutaneous squamous cell carcinoma with the 40-gene expression profile test.

Aim: To clinically validate the 40-gene expression profile (40-GEP) test for cutaneous squamous cell carcinoma patients and evaluate coupling the test with individual clinicopathologic risk factor-based assessment methods. Patients & methods: In a 33-site study, primary tumors with known patient outcomes were assessed under clinical testing conditions (n = 420). The 40-GEP results were integrated with clinicopathologic risk factors. Kaplan-Meier and Cox regression analyses were performed for metastasis. Results: The 40-GEP test demonstrated significant prognostic value. Risk classification was improved via integration of 40-GEP results with clinicopathologic risk factor-based assessment, with metastasis rates near the general cutaneous squamous cell carcinoma population for class 1 and ≥50% for class 2B. Conclusion: Combining molecular profiling with clinicopathologic risk factor assessment enhances stratification of cutaneous squamous cell carcinoma patients and may inform decision-making for risk-appropriate management strategies.

Plain language summary Cutaneous squamous cell carcinoma is a common skin cancer, with approximately 2 million cases diagnosed each year in the USA. Because substantial numbers of patients experience metastasis, which can result in death, accurate metastatic risk assessment is important. Clinicians use clinicopathologic factors to determine risk for disease progression. However, traditional methods miss pinpointing many patients who experience metastasis and sometimes categorize patients as at risk who do not develop metastasis, indicating that additional tools are needed. A molecular test, the 40-gene expression profile (40-GEP), was developed to predict metastatic risk based on the biology of the tumor. This study demonstrates that the 40-GEP, either as an independent tool or together with traditional methods, accurately identifies patients' risk of metastasis. Using the 40-GEP could improve patient management to improve patient outcomes.

Single-cell RNA sequencing of psoriatic skin identifies pathogenic Tc17 cell subsets and reveals distinctions between CD8+ T cells in autoimmunity and cancer.

BACKGROUND: Psoriasis is an inflammatory, IL-17-driven skin disease in which autoantigen-induced CD8+ T cells have been identified as pathogenic drivers. OBJECTIVE: Our study focused on comprehensively characterizing the phenotypic variation of CD8+ T cells in psoriatic lesions. METHODS: We used single-cell RNA sequencing to compare CD8+ T-cell transcriptomic heterogeneity between psoriatic and healthy skin. RESULTS: We identified 11 transcriptionally diverse CD8+ T-cell subsets in psoriatic and healthy skin. Among several inflammatory subsets enriched in psoriatic skin, we observed 2 Tc17 cell subsets that were metabolically divergent, were developmentally related, and expressed CXCL13, which we found to be a biomarker of psoriasis severity and which achieved comparable or greater accuracy than IL17A in a support vector machine classifier of psoriasis and healthy transcriptomes. Despite high coinhibitory receptor expression in the Tc17 cell clusters, a comparison of these cells with melanoma-infiltrating CD8+ T cells revealed upregulated cytokine, cytolytic, and metabolic transcriptional activity in the psoriatic cells that differed from an exhaustion program. CONCLUSION: Using high-resolution single-cell profiling in tissue, we have uncovered the diverse landscape of CD8+ T cells in psoriatic and healthy skin, including 2 nonexhausted Tc17 cell subsets associated with disease severity.

Validation of a 40-gene expression profile test to predict metastatic risk in localized high-risk cutaneous squamous cell carcinoma.

BACKGROUND: Current staging systems for cutaneous squamous cell carcinoma (cSCC) have limited positive predictive value for identifying patients who will experience metastasis. OBJECTIVE: To develop and validate a gene expression profile (GEP) test for predicting risk for metastasis in localized, high-risk cSCC with the goal of improving risk-directed patient management. METHODS: Archival formalin-fixed paraffin-embedded primary cSCC tissue and clinicopathologic data (n = 586) were collected from 23 independent centers in a prospectively designed study. A GEP signature was developed using a discovery cohort (n = 202) and validated in a separate, nonoverlapping, independent cohort (n = 324). RESULTS: A prognostic 40-GEP test was developed and validated, stratifying patients with high-risk cSCC into classes based on metastasis risk: class 1 (low risk), class 2A (high risk), and class 2B (highest risk). For the validation cohort, 3-year metastasis-free survival rates were 91.4%, 80.6%, and 44.0%, respectively. A positive predictive value of 60% was achieved for the highest-risk group (class 2B), an improvement over staging systems, and negative predictive value, sensitivity, and specificity were comparable to staging systems. LIMITATIONS: Potential understaging of cases could affect metastasis rate accuracy. CONCLUSION: The 40-GEP test is an independent predictor of metastatic risk that can complement current staging systems for patients with high-risk cSCC.

Clinical Considerations for Integrating Gene Expression Profiling into Cutaneous Squamous Cell Carcinoma Management.

Gene expression profile (GEP) testing is now commercially available for metastatic risk prediction in patients with cutaneous squamous cell carcinoma (CSCC) and one or more high-risk factors. The purpose of this article is to provide an early framework for healthcare providers looking to integrate patient-specific tumor biology into their clinical practice using GEP testing. To develop a framework for clinical use, an expert panel was convened to identify CSCC management decision points where GEP testing may be immediately incorporated into practice until the definitive results of prospective trials become available. Based on their discussion, the expert panel focused on the areas of nodal evaluation, adjuvant radiation therapy, and follow-up and surveillance. The panel emphasized that GEP prognostic test results should not currently be used as a surrogate for standard of care treatment but as an additional data point when determining individualized management for patients with high-risk CSCC. Whenever possible, decisions on management plans for these patients should be developed with multidisciplinary input. J Drugs Dermatol. 2021;20:6(Suppl):s5-11. doi:10.36849/JDD.6068.

Field cancerization: Treatment.

The goal of field cancerization treatment is to reduce the risk of developing keratinocyte carcinoma. Selecting the appropriate therapy depends on the degree of field cancerization and the number of invasive cutaneous squamous cell carcinomas. Other considerations include treatment efficacy, cost, side effects, and patient preference. Field therapies are preferred because they address clinically visible disease and subclinical atypia. However, lesion-directed therapies are useful for lesions that are more difficult to treat or those where a histologic diagnosis is required. Patients with extensive field cancerization benefit from a combination of field-directed and lesion-directed treatments. The second article in this continuing medical education series provides a framework to guide evidence-based decision making for field cancerization treatment.

Field cancerization: Definition, epidemiology, risk factors, and outcomes.

Field cancerization was first described in 1953 when pathologic atypia was identified in clinically normal tissue surrounding oropharyngeal carcinomas. The discovery of mutated fields surrounding primary tumors raised the question of whether the development of subsequent tumors within the field represented recurrences or additional primary tumors. Since this initial study, field cancerization has been applied to numerous other epithelial tissues, including the skin. Cutaneous field cancerization occurs in areas exposed to chronic ultraviolet radiation, which leads to clonal proliferations of p53-mutated fields and is characterized by multifocal actinic keratoses, squamous cell carcinomas in situ, and cutaneous squamous cell carcinomas. In the first article in this continuing medical education series, we define field cancerization, review the available grading systems, and discuss the epidemiology, risk factors, and outcomes associated with this disease.

Validation of the English Basal and Squamous Cell Carcinoma Quality of Life (BaSQoL) Questionnaire.

BACKGROUND: Keratinocyte carcinomas (KC) impact patient quality of life (QoL). There is a need for validated QoL instruments specific to KC. The Basal and Squamous Cell Carcinoma QoL (BaSQoL) questionnaire was developed to comprehensively measure issues of importance to patients with KC. OBJECTIVE: To validate and characterize the BaSQoL questionnaire for QoL measurement after diagnosis and treatment of KC. METHODS: This was a prospective, observational study. Patients with basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) were asked to fill out BaSQoL, Skin Cancer Index (SCI), and Hospital Anxiety and Depression Scale (HADS) questionnaires. Descriptive statistics and classical test theory were used to assess validity. RESULTS: One hundred eighty-seven subjects enrolled in this study: 122 with BCC and 65 with SCC. One hundred seventy-one subjects (91.4%) completed questionnaires at all 3 time points; 16 patients (8.6%) were lost to follow-up. Overall performance using classical test theory was good, with good internal consistency (Cronbach's α 0.63-0.80). BaSQoL subscales were strongly correlated with subscales of the SCI, demonstrating convergent validity, and weakly correlated with HADS, showing divergent validity. CONCLUSION: The English language version of BaSQoL has good face, content, and construct validity. This study validates BaSQoL for use in English-speaking patients with BCC and SCC.

Predicting skin cancer in organ transplant recipients: development of the SUNTRAC screening tool using data from a multicenter cohort study.

Skin cancer is a common post-transplant complication. In this study, the Skin and Ultraviolet Neoplasia Transplant Risk Assessment Calculator (SUNTRAC) was developed to stratify patients into risk groups for post-transplant skin cancer. Data for this study were obtained from the Transplant Skin Cancer Network (TSCN), which conducted a multicenter study across 26 transplant centers in the United States. In total, 6340 patients, transplanted from 2003 and 2008, were included. Weighted point values were assigned for each risk factor based on beta coefficients from multivariable modeling: white race (9 points), pretransplant history of skin cancer (6 points), age ≥ 50 years (4 points), male sex (2 points), and thoracic transplant (1 point). Good prognostic discrimination (optimism-corrected c statistic of 0.74) occurred with a 4-tier system: 0-6 points indicating low risk, 7-13 points indicating medium risk, 14-17 points indicating high risk, and 18-22 points indicating very high risk. The 5-year cumulative incidence of development of skin cancer was 1.01%, 6.15%, 15.14%, and 44.75%, for Low, Medium, High, and Very High SUNTRAC categories, respectively. Based on the skin cancer risk in different groups, the authors propose skin cancer screening guidelines based on this risk model.

Association of Postoperative Antibiotics With Surgical Site Infection in Mohs Micrographic Surgery.

BACKGROUND: Surgical site infection (SSI) is the most frequent complication of Mohs micrographic surgery. Previous studies have identified risk factors for SSI, but it is not known whether antibiotic prophylaxis mitigates this risk. OBJECTIVE: To measure the association between antibiotic prophylaxis and SSI in a convenience sample of Mohs cases and to report on the utility of propensity scoring to control for confounding by indication in registry data. METHODS: Data were drawn from a pilot quality improvement registry of 816 Mohs cases. The relationship between antibiotic prophylaxis and SSI was assessed with logistic regression modeling using propensity score methods to adjust for confounding. RESULTS: One hundred fifty-one cases were prescribed antibiotic prophylaxis (18.5%). Of 467 cases with follow-up, 16 (3.4%) developed SSI. Infection rates were higher in subjects prescribed prophylaxis, but propensity adjustment reduced this effect. Adjusted odds of infection were 1.47-fold higher in subjects prescribed antibiotics and not statistically significant (95% confidence interval 0.29-7.39; p = .64). CONCLUSION: Although there was no significant difference in SSI among patients prescribed prophylactic antibiotics, statistical precision was limited by the low incidence of infection. Larger population-based prospective registry studies including propensity adjustment are needed to confirm the benefit of prophylactic antibiotics in high-risk surgical cases.

Performance Measures in Dermatologic Surgery: A Review of the Literature and Future Directions.

BACKGROUND: In recent years, health care reform initiatives have aimed to assess quality of care through the use of performance measures. Multiple specialties, including dermatology, have implemented registries to track and report health care quality. OBJECTIVE: The authors review the history and rationale for assessing quality in dermatologic surgery. The authors also discuss the different types of performance measures and the current efforts to develop clinically relevant dermatologic surgery-specific measures. MATERIALS AND METHODS: An extensive literature review was conducted using OVID, MEDLINE, PubMed, and government and health care-related websites to identify articles related to surgical performance measures. RESULTS: Few performance measures are established to assess quality in dermatologic surgery. The authors propose specific candidate measures and discuss how clinical registries can capture measures that meet federal reporting requirements. CONCLUSION: Assessment of health care quality will become increasingly important in health care reform. Physicians need to take an active role in selecting appropriate, clinically relevant performance measures that will help improve patient care while containing health care costs and meeting government-mandated reporting requirements.

Why Cockayne syndrome patients do not get cancer despite their DNA repair deficiency.

Cockayne syndrome (CS) and xeroderma pigmentosum (XP) are human photosensitive diseases with mutations in the nucleotide excision repair (NER) pathway, which repairs DNA damage from UV exposure. CS is mutated in the transcription-coupled repair (TCR) branch of the NER pathway and exhibits developmental and neurological pathologies. The XP-C group of XP patients have mutations in the global genome repair (GGR) branch of the NER pathway and have a very high incidence of UV-induced skin cancer. Cultured cells from both diseases have similar sensitivity to UV-induced cytotoxicity, but CS patients have never been reported to develop cancer, although they often exhibit photosensitivity. Because cancers are associated with increased mutations, especially when initiated by DNA damage, we examined UV-induced mutagenesis in both XP-C and CS cells, using duplex sequencing for high-sensitivity mutation detection. Duplex sequencing detects rare mutagenic events, independent of selection and in multiple loci, enabling examination of all mutations rather than just those that confer major changes to a specific protein. We found telomerase-positive normal and CS-B cells had increased background mutation frequencies that decreased upon irradiation, purging the population of subclonal variants. Primary XP-C cells had increased UV-induced mutation frequencies compared with normal cells, consistent with their GGR deficiency. CS cells, in contrast, had normal levels of mutagenesis despite their TCR deficiency. The lack of elevated UV-induced mutagenesis in CS cells reveals that their TCR deficiency, although increasing cytotoxicity, is not mutagenic. Therefore the absence of cancer in CS patients results from the absence of UV-induced mutagenesis rather than from enhanced lethality.

Brief Report: Interleukin-17A-Dependent Asymmetric Stem Cell Divisions Are Increased in Human Psoriasis: A Mechanism Underlying Benign Hyperproliferation.

The balance between asymmetric and symmetric stem cell (SC) divisions is key to tissue homeostasis, and dysregulation of this balance has been shown in cancers. We hypothesized that the balance between asymmetric cell divisions (ACDs) and symmetric cell divisions (SCDs) would be dysregulated in the benign hyperproliferation of psoriasis. We found that, while SCDs were increased in squamous cell carcinoma (SCC) (human and murine), ACDs were increased in the benign hyperproliferation of psoriasis (human and murine). Furthermore, while sonic hedgehog (linked to human cancer) and pifithrinα (p53 inhibitor) promoted SCDs, interleukin (IL)-1α and amphiregulin (associated with benign epidermal hyperproliferation) promoted ACDs. While there was dysregulation of the ACD:SCD ratio, no change in SC frequency was detected in epidermis from psoriasis patients, or in human keratinocytes treated with IL-1α or amphiregulin. We investigated the mechanism whereby immune alterations of psoriasis result in ACDs. IL17 inhibitors are effective new therapies for psoriasis. We found that IL17A increased ACDs in human keratinocytes. Additionally, studies in the imiquimod-induced psoriasis-like mouse model revealed that ACDs in psoriasis are IL17A-dependent. In summary, our studies suggest an association between benign hyperproliferation and increased ACDs. This work begins to elucidate the mechanisms by which immune alteration can induce keratinocyte hyperproliferation. Altogether, this work affirms that a finely tuned balance of ACDs and SCDs is important and that manipulating this balance may constitute an effective treatment strategy for hyperproliferative diseases. Stem Cells 2017;35:2001-2007.

Validity of skin cancer malignancy reporting to the Organ Procurement Transplant Network: A cohort study.

BACKGROUND: The Organ Procurement Transplant Network (OPTN) registry collects data on posttransplant malignancies in solid organ transplant recipients. Complete and accurate registry data on skin cancer is critical for research on epidemiology and interventions. OBJECTIVE: The study goal was to determine the validity of Organ Procurement Transplant Network skin cancer data. METHODS: This cohort study compared reporting of posttransplant squamous cell carcinoma (SCC) and malignant melanoma (MM) in OPTN to medical-record review-derived data from the Transplant Skin Cancer Network (TSCN) database. In total, 4934 organ transplant recipients from the TSCN database were linked to patient-level OPTN malignancy data. We calculated sensitivity, specificity, correct classification (CC), positive predictive value (PPV), and negative predictive value (NPV) for SCC and MM reporting in the OPTN database. RESULTS: OPTN reporting for SCC (population prevalence 11%) had sensitivity 41%, specificity 99%, PPV 88%, NPV 93%, and CC 93%. OPTN reporting for MM (population prevalence 1%) had sensitivity 22%, specificity 100%, PPV 73%, NPV 99%, and CC 99%. LIMITATIONS: Only a subset of patients in the TSCN cohort had matched United Network for Organ Sharing cancer registry data for comparison. CONCLUSION: OPTN reporting had poor sensitivity but excellent specificity for SCC and MM. Dermatologists and transplant physicians are encouraged to improve the validity of OPTN skin cancer data through improved communication and reporting.

Undifferentiated pleomorphic sarcoma: Factors predictive of adverse outcomes.

BACKGROUND: Undifferentiated pleomorphic sarcoma (UPS) encompasses rare neoplasms that can arise either in the dermis or in the subfascial soft tissue. The behavior of UPS ranges from indolent to aggressive, but data predicting outcomes are limited. OBJECTIVE: Identify predictors of poor outcomes by analyzing a large collection of UPS cases. METHODS: We evaluated all available cases of UPS (including those termed atypical fibroxanthoma, malignant fibrous histiocytoma, pleomorphic dermal sarcoma, and subfascial UPS) across 3 tertiary care centers. RESULTS: Among the 319 patients, 45 experienced recurrence, 33 experienced metastasis, and 96 died of any cause. Risk factors for recurrence were clinical tumor size larger than 5 cm and invasion beyond subcutaneous fat. Risk factors for distant metastases were tumor site, tumor size larger than 2 cm, invasion beyond subcutaneous fat, and lymphovascular invasion. Risk factors for overall mortality were age, immunosuppression, tumor size larger than 2 cm, and lymphovascular invasion. History of skin cancer was associated with a lower risk of recurrence and metastasis. LIMITATIONS: This was a retrospective study. CONCLUSIONS: Using the unbiased approach of pooling all UPS cases regardless of terminology, we identified clinical and histologic factors predicting poor outcomes. We propose subcategorization of UPS (into superficial versus deep UPS), which is consistent with the American Joint Committee on Cancer staging of soft-tissue sarcoma.

Risk of cutaneous squamous cell carcinoma after treatment of basal cell carcinoma with vismodegib.

BACKGROUND: Vismodegib is a first-in-class agent targeting the hedgehog signaling pathway for treatment of patients with locally advanced basal cell carcinoma (BCC) and metastatic BCC. There have been concerns about the development of squamous cell carcinoma (SCC) in patients treated with this drug. OBJECTIVE: We sought to determine whether treatment with vismodegib is associated with an increase in the risk of cutaneous SCC. METHODS: In this retrospective cohort study, patients treated with vismodegib as part of phase I and II clinical studies were compared with participants from the University of California, San Francisco, Nonmelanoma Skin Cancer Cohort who received standard therapy for primary BCC. In total, 1675 patients were included in the analysis, and the development of SCC after vismodegib exposure was assessed. RESULTS: The use of vismodegib was not associated with an increased risk of subsequent development of SCC (adjusted hazard ratio, 0.57; 95% confidence interval, 0.28-1.16). Covariates including age, sex, history of previous nonmelanoma skin cancer, and number of visits per year were significantly associated with the development of SCC. LIMITATIONS: A limitation of the study was that a historic control cohort was used as a comparator. CONCLUSIONS: Vismodegib was not associated with an increased risk of subsequent SCC when compared with standard surgical treatment of BCC.

Network analysis of psoriasis reveals biological pathways and roles for coding and long non-coding RNAs.

BACKGROUND: Psoriasis is an immune-mediated, inflammatory disorder of the skin characterized by chronic inflammation and hyperproliferation of the epidermis. Differential expression analysis of microarray or RNA-seq data have shown that thousands of coding and non-coding genes are differentially expressed between psoriatic and healthy control skin. However, differential expression analysis may fail to detect perturbations in gene coexpression networks. Sensitive detection of such networks may provide additional insight into important disease-associated pathways. In this study, we applied weighted gene coexpression network analysis (WGCNA) on RNA-seq data from psoriasis patients and healthy controls. RESULTS: RNA-seq was performed on skin samples from 18 psoriasis patients (pre-treatment and post-treatment with the TNF-α inhibitor adalimumab) and 16 healthy controls, generating an average of 52.3 million 100-bp paired-end reads per sample. Using WGCNA, we identified 3 network modules that were significantly correlated with psoriasis and 6 network modules significantly correlated with biologic treatment, with only 16 % of the psoriasis-associated and 5 % of the treatment-associated coexpressed genes being identified by differential expression analysis. In a majority of these correlated modules, more than 50 % of coexpressed genes were long non-coding RNAs (lncRNA). Enrichment analysis of these correlated modules revealed that short-chain fatty acid metabolism and olfactory signaling are amongst the top pathways enriched for in modules associated with psoriasis, while regulation of leukocyte mediated cytotoxicity and regulation of cell killing are amongst the top pathways enriched for in modules associated with biologic treatment. A putative autoantigen, LL37, was coexpressed in the module most correlated with psoriasis. CONCLUSIONS: This study has identified several networks of coding and non-coding genes associated with psoriasis and biologic drug treatment, including networks enriched for short-chain fatty acid metabolism and olfactory receptor activity, pathways that were not previously identified through differential expression analysis and may be dysregulated in psoriatic skin. As these networks are comprised mostly of non-coding genes, it is likely that non-coding genes play critical roles in the regulation of pathways involved in the pathogenesis of psoriasis.