Inherited duplications of PPP2R3B predispose to nevi and melanoma via a C21orf91-driven proliferative phenotype

PURPOSE

Much of the heredity of melanoma remains unexplained. We sought predisposing germline copy-number variants using a rare disease approach.

METHODS

Whole-genome copy-number findings in patients with melanoma predisposition syndrome congenital melanocytic nevus were extrapolated to a sporadic melanoma cohort. Functional effects of duplications in PPP2R3B were investigated using immunohistochemistry, transcriptomics, and stable inducible cellular models, themselves characterized using RNAseq, quantitative real-time polymerase chain reaction (qRT-PCR), reverse phase protein arrays, immunoblotting, RNA interference, immunocytochemistry, proliferation, and migration assays.

RESULTS

We identify here a previously unreported genetic susceptibility to melanoma and melanocytic nevi, familial duplications of gene PPP2R3B. This encodes PR70, a regulatory unit of critical phosphatase PP2A. Duplications increase expression of PR70 in human nevus, and increased expression in melanoma tissue correlates with survival via a nonimmunological mechanism. PPP2R3B overexpression induces pigment cell switching toward proliferation and away from migration. Importantly, this is independent of the known microphthalmia-associated transcription factor (MITF)-controlled switch, instead driven by C21orf91. Finally, C21orf91 is demonstrated to be downstream of MITF as well as PR70.

CONCLUSION

This work confirms the power of a rare disease approach, identifying a previously unreported copy-number change predisposing to melanocytic neoplasia, and discovers C21orf91 as a potentially targetable hub in the control of phenotype switching.

The Genomic Landscape of Actinic Keratosis

Actinic keratoses (AKs) are lesions of epidermal keratinocyte dysplasia and are precursors for invasive cutaneous squamous cell carcinoma (cSCC). Identifying the specific genomic alterations driving the progression from normal skin to skin with AK to skin with invasive cSCC is challenging because of the massive UVR-induced mutational burden characteristic at all stages of this progression. In this study, we report the largest AK whole-exome sequencing study to date and perform a mutational signature and candidate driver gene analysis on these lesions. We demonstrate in 37 AKs from both immunosuppressed and immunocompetent patients that there are significant similarities between AKs and cSCC in terms of mutational burden, copy number alterations, mutational signatures, and patterns of driver gene mutations. We identify 44 significantly mutated AK driver genes and confirm that these genes are similarly altered in cSCC. We identify azathioprine mutational signature in all AKs from patients exposed to the drug, providing further evidence for its role in keratinocyte carcinogenesis. cSCCs differ from AKs in having higher levels of intrasample heterogeneity. Alterations in signaling pathways also differ, with immune-related signaling and TGFβ signaling significantly more mutated in cSCC. Integrating our findings with independent gene expression datasets confirms that dysregulated TGFβ signaling may represent an important event in AK‒cSCC progression.

The burden of cutaneous disease in solid organ transplant recipients of color

Organ transplant recipients (OTRs) are at increased risk of cutaneous malignancy. Skin disorders in OTRs of color (OTRoC) have rarely been systematically assessed. We aimed to ascertain the burden of skin disease encountered in OTRoC by prospectively collecting data from OTRs attending 2 posttransplant skin surveillance clinics: 1 in London, UK and 1 in Philadelphia, USA. Retrospective review of all dermatological diagnoses was performed. Data from 1766 OTRs were analyzed: 1024 (58%) white, 376 (21%) black, 261 (15%) Asian, 57 (3%) Middle Eastern/Mediterranean (ME/M), and 48 (2.7%) Hispanic; and 1128 (64%) male. Viral infections affected 45.1% of OTRs, and were more common in white and ME/M patients (P < .001). Fungal infections affected 28.1% and were more common in ME/M patients (P < .001). Inflammatory skin disease affected 24.5%, and was most common in black patients (P < .001). In addition, 26.4% of patients developed skin cancer. There was an increased risk of skin cancer in white vs nonwhite OTRs (HR 4.4, 95% CI 3.5-5.7, P < .001): keratinocyte cancers were more common in white OTRs (P < .001) and Kaposi sarcoma was more common in black OTRs (P < .001). These data support the need for programs that promote targeted dermatology surveillance for all OTRs, regardless of race/ethnicity or country of origin.

The prevalence of human leucocyte antigen and human papillomavirus DNA in penile intraepithelial neoplasia in England 2011-2012

BACKGROUND

The pathogenesis of penile intraepithelial neoplasia (PeIN) is unclear but human papillomavirus (HPV) infection and polymorphisms in human leucocyte antigen (HLA).

OBJECTIVES

To examine the prevalence of HPV DNA and HLA in PeIN.

METHODS

Adult Caucasian men with a clinical and histological diagnosis of PeIN, that is, Bowenoid papulosis (BP), Bowen's disease of penis (BDP) and erythroplasia of Queyrat (EQ) were selected and phenotyped from the clinical records. DNA was extracted from blood and paraffin-embedded sections for HLA and HPV typing, respectively. Human leucocyte antigen allele frequencies were compared with those derived from the UK-based Caucasian population.

RESULTS

Seventy-two cases of PeIN (20 BP, 34 BDP and 18 EQ) were studied. Human papillomavirus DNA was identified in 65/72 (90.2%) PeIN; Alphapapillomavirus types were detected in 62/72 (85%) followed by Betapapillomavirus types in 9/72 (12.5%) and cutaneous types in 7/72 (9.7%); HPV16 was the most prevalent genotype at 35/72 (48.6%) followed by HPV33 at 7/72 (9.7%); multiple infections were seen in 18/72 (25%) PeIN. HLA-C*15 (Bonferroni corrected p = 0.049) confers susceptibility to PeIN, whereas HLA-DQA1*01 (corrected p = 0.02) protects against PeIN. HPV16-associated PeIN cases showed no statistically significant association with HLA genotype after multiple corrections.

CONCLUSION

Human papillomavirus is involved in the pathogenesis of PeIN. Immunogenotype may play a role in the pathogenesis of PeIN.

Development of a core outcome set for cutaneous squamous cell carcinoma trials: identification of core domains and outcomes

BACKGROUND

The lack of uniformity in the outcomes reported in clinical studies of the treatment of cutaneous squamous cell carcinoma (cSCC) complicates efforts to compare treatment effectiveness across trials.

OBJECTIVES

To develop a core outcome set (COS), a minimum set of agreed-upon outcomes to be measured in all clinical trials of a given disease or outcome, for the treatment of cSCC.

METHODS

One hundred and nine outcomes were identified via a systematic literature review and interviews with 28 stakeholders. After consolidation of this long list, 55 candidate outcomes were rated by 19 physician and 10 patient stakeholders, in two rounds of Delphi exercises. Outcomes scored 'critically important' (score of 7, 8 or 9) by ≥ 70% of patients and ≥ 70% of physicians were provisionally included. At the consensus meeting, after discussion and voting of 44 international experts and patients, the provisional list was reduced to a final core set, for which consensus was achieved among all meeting participants.

RESULTS

A core set of seven outcomes was finalized at the consensus meeting: (i) serious or persistent adverse events, (ii) patient-reported quality of life, (iii) complete response, (iv) partial response, (v) recurrence-free survival, (vi) progression-free survival and (vii) disease-specific survival.

CONCLUSIONS

In order to increase the comparability of results across trials and to reduce selective reporting bias, cSCC researchers should consider reporting these core outcomes. Further work needs to be performed to identify the measures that should be reported for each of these outcomes.

Loss of the laminin subunit alpha-3 induces cell invasion and macrophage infiltration in cutaneous squamous cell carcinoma

BACKGROUND

Cutaneous squamous cell carcinoma (cSCC) is a common cancer that invades the dermis through the basement membrane. The role of the basement membrane in poorly differentiated cSCC is not well understood.

OBJECTIVES

To study the effect that loss of the laminin subunit alpha-3 (α3) chain from the tumour microenvironment has on tumour invasion and inflammatory cell recruitment.

METHODS

We examined the role of the basement membrane proteins laminin subunits α3, β3 and γ2 in SCC invasion and inflammatory cell recruitment using immunohistochemistry, short hairpin RNA knockdown, RNA-Seq, mouse xenograft models and patient tumour samples.

RESULTS

Analysis of SCC tumours and cell lines using antibodies specific to laminin chains α3, β3 and γ2 identified a link between poorly differentiated SCC and reduced expression of laminin α3 but not the other laminin subunits investigated. Knockdown of laminin α3 increased tumour invasion both in vitro and in vivo. Western blot and immunohistochemical staining identified increased phosphorylated myosin light chain with loss of laminin α3. Inhibition of ROCK (rho-associated protein kinase) but not Rac1 significantly reduced the invasive potential of laminin α3 knockdown cells. Knockdown of laminin subunits α3 and γ2 increased monocyte recruitment to the tumour microenvironment. However, only the loss of laminin α3 correlated with increased tumour-associated macrophages both in xenografted tumours and in patient tumour samples.

CONCLUSIONS

These data provide evidence that loss of the laminin α3 chain in cSCC has an effect on both the epithelial and immune components of cSCC, resulting in an aggressive tumour microenvironment.

Immunogenetics and human papillomavirus (HPV) in male genital lichen sclerosus (MGLSc)

BackgroundThe pathogenesis of male genital lichen sclerosus (MGLSc) is controversial. Incriminated factors include infection with human papillomavirus (HPV) and autoimmunity (e.g. Human Leukocyte Antigen [HLA]). To address the roles of HLA and HPV in MGLSc we studied adult Caucasian males with a clinical and histological diagnosis of MGLSc. The men in the study attended two specialised Male Genital Dermatoses Clinics between July 2011 and September 2012 and were selected and phenotyped from the clinical records. DNA was extracted from blood and paraffin-embedded biopsy sections, for HLA and HPV typing, respectively. HLA allele frequencies were compared with those derived from the UK-based Caucasian population. Eighty-eight cases of MGLSc were identified. HPV DNA was detected in 33/88 (37.5%) cases of MGLSc. HPV16 was the most prevalent type found: 11/88 (12.5%) MGLSc. No statistically significant HLA associations were established but HLA-B*35, -B*51, -C*15, -DRB1*04, -DRB1*10 (predisposition) and -DQA1*01 (protection) were revealed as alleles of interest. HPV16-associated MGLSc cases showed no statistically significant association with HLA genotype. The relationship between HPV and MGLSc suggests a passenger effect rather than a pathogenic role. HLA is not associated with MGLSc nor co-existent HPV16.

A 10-year review of surgical management of dermatofibrosarcoma protuberans

BACKGROUND

Dermatofibrosarcoma protuberans (DFSP) is a rare skin cancer. Standard treatment in the UK is either wide local excision (WLE) or Mohs micrographic surgery (MMS). It is unclear which approach has the lower recurrence rate.

OBJECTIVES

We undertook a retrospective comparative review of surgical management of DFSP in the UK National Health Service in order to define (i) current surgical practice for primary and recurrent DFSP, (ii) local recurrence rates for primary DFSP and (iii) survival outcomes for DFSP.

METHODS

A retrospective clinical case-note review of patients with histologically confirmed DFSP (January 2004 to December 2013) who have undergone surgical treatment.

RESULTS

The surgical management of 483 primary and 64 recurrent DFSP in 11 plastic surgery and 15 dermatology departments was analysed. Almost 75% of primary DFSP (n = 362) were treated with WLE and 20% (n = 97) with MMS. For recurrent DFSP, 69% (n = 44) and 23% (n = 15) of patients underwent WLE and MMS, respectively. Recurrent primary DFSP occurred in six patients after WLE and none after MMS. The median follow-up time was 25·5 months (interquartile range 6·8-45·1) for new and 19·8 (IQR 4·5-44·5) for recurrent DFSP [Correction added on 1 Feb 2021, after first online publication: 4.8 years (interquartile range 3.5-5.8) was incorrect], with eight reported deaths during the follow-up analysis period (one confirmed to be DFSP related).

CONCLUSIONS

WLE was the most common surgical modality used to treat DFSP across the UK. The local recurrence rate was very low, occurring only after WLE. Although a prospective randomized controlled trial may provide more definitive outcomes, in the absence of a clearly superior surgical modality, treatment decisions should be based on patient preference, clinical expertise and cost.

Treatment approaches in immunosuppressed patients with advanced cutaneous squamous cell carcinoma

Immunosuppression, both iatrogenic and disease-related, is associated with a greatly increased incidence of cutaneous SCC (cSCC) and with aggressive cSCC and worse disease outcomes. Consequently, rapid access to skin cancer services and prudent surgical choices, such as circumferential margin assessment, is essential when treating advanced cSCC in an immunosuppressed patient. For high-risk cancers and control of cSCC multiplicity, additional strategies should be actively considered within the multidisciplinary clinical care team. These include minimization or revision of immunosuppressive medications, systemic chemoprevention (including retinoids, nicotinamide, capecitabine) and adjuvant therapies such as radiotherapy. Unfortunately, there is a relative paucity of good evidence for many of these treatments in the immunosuppressed. Systemic treatments for metastatic cSCC are often contraindicated in organ transplant recipients, notably checkpoint inhibitor immunotherapy. There are also toxicity concerns with some conventional chemotherapies and EGFR inhibitors. Until recently, clinical trials have largely excluded immunosuppressed individuals. Development of more effective treatment for advanced cSCC in this high-risk group and prospective clinical trials are now research priorities.

P2X7 in Cancer: From Molecular Mechanisms to Therapeutics

P2X7 is a transmembrane receptor expressed in multiple cell types including neurons, dendritic cells, macrophages, monocytes, B and T cells where it can drive a wide range of physiological responses from pain transduction to immune response. Upon activation by its main ligand, extracellular ATP, P2X7 can form a nonselective channel for cations to enter the cell. Prolonged activation of P2X7, via high levels of extracellular ATP over an extended time period can lead to the formation of a macropore, leading to depolarization of the plasma membrane and ultimately to cell death. Thus, dependent on its activation state, P2X7 can either drive cell survival and proliferation, or induce cell death. In cancer, P2X7 has been shown to have a broad range of functions, including playing key roles in the development and spread of tumor cells. It is therefore unsurprising that P2X7 has been reported to be upregulated in several malignancies. Critically, ATP is present at high extracellular concentrations in the tumor microenvironment (TME) compared to levels observed in normal tissues. These high levels of ATP should present a survival challenge for cancer cells, potentially leading to constitutive receptor activation, prolonged macropore formation and ultimately to cell death. Therefore, to deliver the proven advantages for P2X7 in driving tumor survival and metastatic potential, the P2X7 macropore must be tightly controlled while retaining other functions. Studies have shown that commonly expressed P2X7 splice variants, distinct SNPs and post-translational receptor modifications can impair the capacity of P2X7 to open the macropore. These receptor modifications and potentially others may ultimately protect cancer cells from the negative consequences associated with constitutive activation of P2X7. Significantly, the effects of both P2X7 agonists and antagonists in preclinical tumor models of cancer demonstrate the potential for agents modifying P2X7 function, to provide innovative cancer therapies. This review summarizes recent advances in understanding of the structure and functions of P2X7 and how these impact P2X7 roles in cancer progression. We also review potential therapeutic approaches directed against P2X7.

Targeting p63 Upregulation Abrogates Resistance to MAPK Inhibitors in Melanoma

Targeting the MAPK pathway by combined inhibition of BRAF and MEK has increased overall survival in advanced BRAF-mutant melanoma in both therapeutic and adjuvant clinical settings. However, a significant proportion of tumors develop acquired resistance, leading to treatment failure. We have previously shown p63 to be an important inhibitor of p53-induced apoptosis in melanoma following genotoxic drug exposure. Here, we investigated the role of p63 in acquired resistance to MAPK inhibition and show that p63 isoforms are upregulated in melanoma cell lines chronically exposed to BRAF and MEK inhibition, with consequent increased resistance to apoptosis. This p63 upregulation was the result of its reduced degradation by the E3 ubiquitin ligase FBXW7. FBXW7 was itself regulated by MDM2, and in therapy-resistant melanoma cell lines, nuclear accumulation of MDM2 caused downregulation of FBXW7 and consequent upregulation of p63. Consistent with this, both FBXW7-inactivating mutations and MDM2 upregulation were found in melanoma clinical samples. Treatment of MAPK inhibitor-resistant melanoma cells with MDM2 inhibitor Nutlin-3A restored FBXW7 expression and p63 degradation in a dose-dependent manner and sensitized these cells to apoptosis. Collectively, these data provide a compelling rationale for future investigation of Nutlin-3A as an approach to abrogate acquired resistance of melanoma to MAPK inhibitor targeted therapy. SIGNIFICANCE: Upregulation of p63, an unreported mechanism of MAPK inhibitor resistance in melanoma, can be abrogated by treatment with the MDM2 inhibitor Nutlin-3A, which may serve as a strategy to overcome resistance.

Therapeutic options for erosive pustular dermatosis of the scalp: a systematic review

BACKGROUND

Erosive pustular dermatosis of the scalp (EPDS) is a chronic condition characterized by erosive plaques and subsequent scarring alopecia as a result of local trauma or inflammation. A number of therapeutic approaches have been described in the literature but there is no consensus of opinion on optimal treatment of the disease.

OBJECTIVES

To provide evidence-based recommendations for topical and systemic treatment of adult patients with EPDS by performing a systematic review.

METHODS

The MEDLINE, MEDLINE In-Process, Embase and Cochrane databases were searched from inception to 26 June 2019 in accordance with the PRISMA guidelines for studies involving adult patients treated for EPDS with at least one reported response to treatment. The study was registered on PROSPERO. Texts were reviewed independently by two authors. The risk of bias and quality of the studies were assessed using the Quality Appraisal Checklist for Case Series Studies.

RESULTS

In total 75 studies were included, involving 168 patients. Many treatments have been reported in the literature, with varying degrees of therapeutic success. The results were highly heterogeneous and methodological quality was very low. We were unable to perform a meta-analysis on the data.

CONCLUSIONS

The limited available evidence supports use of topical corticosteroids, with or without oral zinc, followed by maintenance therapy with topical calcineurin inhibitors as being effective in managing this condition. Topical photodynamic therapy is also potentially beneficial in the management of EPDS. Prospective, comparative, randomized controlled trials are required in order to provide further evidence to guide treatment.

European interdisciplinary guideline on invasive squamous cell carcinoma of the skin: Part 2. Treatment

In order to update recommendations on treatment, supportive care, education and follow-up of patients with invasive cutaneous squamous cell carcinoma (cSCC), a multidisciplinary panel of experts from the European Dermatology Forum, the European Association of Dermato-Oncology and the European Organization of Research and Treatment of Cancer was formed. Recommendations were based on evidence-based literature review, guidelines and expert consensus. Treatment recommendations are presented for common primary cSCC (low risk, high risk), locally advanced cSCC, regional metastatic cSCC (operable or inoperable) and distant metastatic cSCC. For common primary cSCC (the most frequent cSCC type), first-line treatment is surgical excision with postoperative margin assessment or microscopically controlled sugery. Safety margins containing clinical normal-appearing tissue around the tumour during surgical excision and negative margins as reported in the pathology report are necessary to minimise the risk of local recurrence and metastasis. In case of positive margins, a re-excision shall be done, for operable cases. Lymph node dissection is recommended for cSCC with cytologically or histologically confirmed regional nodal involvement. Radiotherapy should be considered as curative treatment for inoperable cSCC, or for non-surgical candidates. Anti-PD-1 antibodies are the first-line systemic treatment for patients with metastatic or locally advanced cSCC who are not candidates for curative surgery or radiation, with cemiplimab being the first approved systemic agent for advanced cSCC by the Food and Drug Administration/European Medicines Agency. Second-line systemic treatments for advanced cSCC include epidermal growth factor receptor inhibitors (cetuximab) combined with chemotherapy or radiation therapy. Multidisciplinary board decisions are mandatory for all patients with advanced disease who require more than surgery. Patients should be engaged with informed decisions on management and be provided with best supportive care to optimise symptom management and improve quality of life. Frequency of follow-up visits and investigations for subsequent new cSCC depend on underlying risk characteristics.

Aggressive Squamous Cell Carcinoma in Organ Transplant Recipients

Importance

Squamous cell carcinoma (SCC) is the most frequent malignant neoplasm found in solid organ transplant recipients and is associated with a more aggressive disease course and higher risk of metastasis and death than in the general population.

Objectives

To report the clinicopathologic features of and identify factors associated with aggressive SCC in solid organ transplant recipients.

Methods

This retrospective multicentric case series included 51 patients who underwent solid organ transplantation and were found to have aggressive SCC, defined by nodal or distant metastasis or death by local progression of primary SCC. Standard questionnaires were completed by the researchers between July 18, 2005, and January 1, 2015. Data were analyzed between February 22, 2016, and July 12, 2016.

Results

Of the 51 participants, 43 were men and 8 were women, with a median age of 51 years (range, 19-71 years) at time of transplantation and 62 years (range, 36-77 years) at time of diagnosis of aggressive SCC. The distribution of aggressive SCC was preferentially on the face (34 [67%]) and scalp (6 [12%]), followed by the upper extremities (6 [12%]). A total of 21 tumors (41%) were poorly differentiated, with a median tumor diameter of 18.0 mm (range, 4.0-64.0 mm) and median tumor depth of 6.2 mm (range, 1.0-20.0 mm). Perineural invasion was present in 20 patients (39%), while 23 (45%) showed a local recurrence. The 5-year overall survival rate was 23%, while 5-year disease-specific survival was 30.5%.

Conclusions and Relevance

Results of this case series suggest that anatomical site, differentiation, tumor diameter, tumor depth, and perineural invasion are important risk factors in aggressive SCC in solid organ transplant recipients.

Epidemiology of basal and cutaneous squamous cell carcinoma in the U.K. 2013-15: a cohort study

BACKGROUND

Basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC), together known as keratinocyte cancers (KCs), are the commonest cancer in white ethnic populations. Recent improvements to registry data collection in England has allowed more accurate analysis of the epidemiology of BCC and cSCC and for the first time we are able to provide an accurate (representative) tumour burden for KC in the U.K.

OBJECTIVES

To estimate the incidence of BCC and cSCC in the U.K.

METHODS

A cohort of patients with KCs between 2013 and 2015 were identified using linkage to diagnostic codes derived from pathology reports collected into the national cancer registry. Data from England's cancer registry were combined with data from Scotland, Northern Ireland and Wales. European age-standardized incidence rates (EASRs) of the first BCC and cSCC per patient per annum (PPPA) were calculated.

RESULTS

In the U.K, the EASR of the first BCC and cSCC PPPA in 2013-15 were 285 and 77 per 100 000 person years, respectively (211 120 KCs total in 2015). The mean annual percentage increase was 5% between 2013 and 2015 for both BCC and cSCC. By counting the first KC PPPA, we include an additional 51% KCs compared with the previous reporting technique which counts only the first BCC and cSCC in a patient's lifetime, yet it represents a probable underestimation of 5-11% of the true tumour count.

CONCLUSIONS

Based on an improved methodology, a more representative incidence of KC is presented, which is essential to healthcare planning and will lead to improved understanding of the epidemiology of KC. What's already known about this topic? Keratinocyte cancers (KCs) are the most common cancers affecting white ethnic populations. The incidence of basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC) is increasing worldwide including the U.K., most commonly in elderly male Caucasian patients. These cancers are traditionally substantially underreported and frequently excluded from national cancer statistics. What does this study add? Using improved data collection methods in England and validated tumour-reporting techniques, we report the most accurate BCC and cSCC incidence data for the U.K. ever published. Identifying the first BCC and cSCC per patient per annum, the incidence of BCC and cSCC in the U.K. (excluding Wales) was 285 and 77 per 100 000 person years, respectively, between 2013 and 2015, with more than 210 000 KCs in the U.K. in 2015.

A Unique Panel of Patient-Derived Cutaneous Squamous Cell Carcinoma Cell Lines Provides a Preclinical Pathway for Therapeutic Testing

BACKGROUND

Cutaneous squamous cell carcinoma (cSCC) incidence continues to rise with increasing morbidity and mortality, with limited treatment options for advanced disease. Future improvements in targeted therapy will rely on advances in genomic/transcriptomic understanding and the use of model systems for basic research. We describe here the panel of 16 primary and metastatic cSCC cell lines developed and characterised over the past three decades in our laboratory in order to provide such a resource for future preclinical research and drug screening.

METHODS

Primary keratinocytes were isolated from cSCC tumours and metastases, and cell lines were established. These were characterised using short tandem repeat (STR) profiling and genotyped by whole exome sequencing. Multiple in vitro assays were performed to document their morphology, growth characteristics, migration and invasion characteristics, and in vivo xenograft growth.

RESULTS

STR profiles of the cSCC lines allow the confirmation of their unique identity. Phylogenetic trees derived from exome sequence analysis of the matched primary and metastatic lines provide insight into the genetic basis of disease progression. The results of in vivo and in vitro analyses allow researchers to select suitable cell lines for specific experimentation.

CONCLUSIONS

There are few well-characterised cSCC lines available for widespread preclinical experimentation and drug screening. The described cSCC cell line panel provides a critical tool for in vitro and in vivo experimentation.