Genetics of basal cell carcinoma

[Recurrence of palpebral basal cell carcinoma according to histological margins]

BACKGROUND

Basal cell carcinomas (BCCs) represent 90% of malignant tumors of the eyelids, which can be locally invasive and destructive. The observation of histological safety margins (MHS) allows for the prevention of recurrence while maintaining a fair compromise between aesthetics and functionality. However, to date, there is no consensus or national recommendations concerning the MHS to be observed according to the various histological subtypes of BCCs.

METHODS

Through a retrospective analysis of patient records and corresponding excisional slides, we studied the 6-year recurrence rate of 98 patients who underwent surgery for palpebral BCC.

RESULTS

MHS were mostly absent in the excisional specimens of recurrent BCCs and significantly more narrow than in non-recurrent BCCs, on average over 2mm.

CONCLUSION

The results of our study suggest that an average MHS greater than 2mm prevents most recurrences.

Molecular Mechanisms and Targeted Therapies of Advanced Basal Cell Carcinoma

Among human cutaneous malignancies, basal cell carcinoma is the most common. Solid advances in unveiling the molecular mechanisms of basal cell carcinoma have emerged in recent years. In Gorlin syndrome, which shows basal cell carcinoma predisposition, identification of the patched 1 gene (PTCH1) mutation was a dramatic breakthrough in understanding the carcinogenesis of basal cell carcinoma. PTCH1 plays a role in the hedgehog pathway, and dysregulations of this pathway are known to be crucial for the carcinogenesis of many types of cancers including sporadic as well as hereditary basal cell carcinoma. In this review, we summarize the clinical features, pathological features and hedgehog pathway as applied in basal cell carcinoma. Other crucial molecules, such as p53 and melanocortin-1 receptor are also discussed. Due to recent advances, therapeutic strategies based on the precise molecular mechanisms of basal cell carcinoma are emerging. Target therapies and biomarkers are also discussed.

Periocular Pigmented Basal Cell Carcinomas: Clinicopathologic Features and Mutational Profile

PURPOSE

Pigmented basal cell carcinomas (PBCC) is an uncommon variant of basal cell carcinoma of the periocular region with limited information in the literature. We highlight the clinicopathological profile and somatic mutations in periocular PBCC.

METHODS

The clinicopathological features and somatic mutations in patients with periocular PBCC were examined and compared with periocular non-PBCC reported in the literature. Next-generation sequencing panel analysis for the excised tumors identified somatic mutations.

RESULTS

In a total of 31 patients, PBCC was common in females (54%; p = 0.03); as a unilateral lower eyelid (n = 22; 71%), solitary mass (n = 30; 98%). Pathologic subtypes were variable. Most were nodular or mixed variants (n = 23; 74%). During the follow up (2.5-4.5 years), 1 patient (3.5%) had a recurrence. The clinical and pathologic features of PBCC were similar to those reported in nonperiocular locations. Somatic mutations detected in 25/31 tumors. Variants in 50/161 genes in the panel were noted. PTCH1 (14/31), TERT (12/31), and SMO (7/31) variants were common. Fifteen patients had novel drivers, including POLE, FANCD2, and CREBBP. SMO mutations were significantly more common in females (7/7), lower eyelid (5/7), and TERT mutations were more common in nodular subtype (10/12).

CONCLUSIONS

In this large cohort of a relatively uncommon variant of BCC, the clinicopathological features and tumor behavior of PBCC was similar to periocular non-PBCC. The somatic mutation spectrum of PBCC resembles that reported in nonperiocular cutaneous BCC with novel drivers identified. We identified several potential actionable mutations that could be targeted with molecular therapy.

Non-coding RNA dysregulation in skin cancers

Skin cancers are the most common cancers worldwide. They can be classified in melanoma and non-melanoma skin cancer (NMSC), the latter includes squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and merkel cell carcinoma (MCC). In recent years, the crucial role of non-coding RNAs (ncRNAs) in skin cancer pathogenesis has become increasingly evident. NcRNAs are functional RNA molecules that lack any protein-coding activity. These ncRNAs are classified based on their length: small, medium-size, and long ncRNAs. Among the most studied ncRNAs there are microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNA (circRNAs). ncRNAs have the ability to regulate gene expression at transcriptional and post-transcriptional levels and are involved in skin cancer cell proliferation, angiogenesis, invasion, and metastasis. Many ncRNAs exhibit tissue- or cell-specific expression while others have been correlated to tumor staging, drug resistance, and prognosis. For these reasons, ncRNAs have both a diagnostic and prognostic significance in skin cancers. Our review summarizes the functional role of ncRNAs in skin cancers and their potential clinical application as biomarkers.

Subtype-Specific Analyses Reveal Infiltrative Basal Cell Carcinomas Are Highly Interactive with their Environment

Little is known regarding the molecular differences between basal cell carcinoma (BCC) subtypes, despite clearly distinct phenotypes and clinical outcomes. In particular, infiltrative BCCs have poorer clinical outcomes in terms of response to therapy and propensity for dissemination. In this project, we aimed to use exome sequencing and RNA sequencing to identify somatic mutations and molecular pathways leading to infiltrative BCCs. Using whole-exome sequencing of 36 BCC samples (eight infiltrative) combined with previously reported exome data (58 samples), we determine that infiltrative BCCs do not contain a distinct somatic variant profile and carry classical UV-induced mutational signatures. RNA sequencing on both datasets revealed key differentially expressed genes, such as POSTN and WISP1, suggesting increased integrin and Wnt signaling. Immunostaining for periostin and WISP1 clearly distinguished infiltrative BCCs, and nuclear β-catenin staining patterns further validated the resulting increase in Wnt signaling in infiltrative BCCs. Of significant interest, in BCCs with mixed morphology, infiltrative areas expressed WISP1, whereas nodular areas did not, supporting a continuum between subtypes. In conclusion, infiltrative BCCs do not differ in their genomic alteration in terms of initiating mutations. They display a specific type of interaction with the extracellular matrix environment regulating Wnt signaling.

The Role of Smoothened-Dependent and -Independent Hedgehog Signaling Pathway in Tumorigenesis

The Hedgehog (Hh)-glioma-associated oncogene homolog (GLI) signaling pathway is highly conserved among mammals, with crucial roles in regulating embryonic development as well as in cancer initiation and progression. The GLI transcription factors (GLI1, GLI2, and GLI3) are effectors of the Hh pathway and are regulated via Smoothened (SMO)-dependent and SMO-independent mechanisms. The SMO-dependent route involves the common Hh-PTCH-SMO axis, and mutations or transcriptional and epigenetic dysregulation at these levels lead to the constitutive activation of GLI transcription factors. Conversely, the SMO-independent route involves the SMO bypass regulation of GLI transcription factors by external signaling pathways and their interacting proteins or by epigenetic and transcriptional regulation of GLI transcription factors expression. Both routes of GLI activation, when dysregulated, have been heavily implicated in tumorigenesis of many known cancers, making them important targets for cancer treatment. Hence, this review describes the various SMO-dependent and SMO-independent routes of GLI regulation in the tumorigenesis of multiple cancers in order to provide a holistic view of the paradigms of hedgehog signaling networks involving GLI regulation. An in-depth understanding of the complex interplay between GLI and various signaling elements could help inspire new therapeutic breakthroughs for the treatment of Hh-GLI-dependent cancers in the future. Lastly, we have presented an up-to-date summary of the latest findings concerning the use of Hh inhibitors in clinical developmental studies and discussed the challenges, perspectives, and possible directions regarding the use of SMO/GLI inhibitors in clinical settings.

Ultraviolet Radiation and Basal Cell Carcinoma: An Environmental Perspective

Ultraviolet radiation (UVR) is a known carcinogen participated for the development of skin cancers. Solar UVR exposure, particularly ultraviolet B (UVB), is the mostly significant environmental risk factor for the occurrence and progress of basal cell carcinoma(BCC). Both cumulative and intermittent high-grade UVR exposure could promote the uncontrolled replication of skin cells. There are also exsiting other contributing environmental factors that combine with the UVR exposure to promote the development of BCC. DNA damage in formation of skin cancers is considered to be a result of UVR toxicity. It is UVR that could activate a series of oncogenes simultaneously inactivating tumor suppressor genes and aberrant proliferation and survival of keratinocytes that repair these damages. Furthermore, mounting evidence demonstrates that inflammatory responses of immune cells in the tumor microenvironment plays crucial role in the skin tumorigenesis as well. In this chapter, we will follow the function of UVR in the onset and development of BCC. We describe the factors that influence BCC induced by UVR, and also review the recent advances of pathogenesis of BCC induced by UVR from the genetic and inflammatory aspects.

Inhibitors of Nucleotide Excision Repair Decrease UVB-Induced Mutagenesis-An In Vitro Study

The high incidence of skin cancers in the Caucasian population is primarily due to the accumulation of DNA damage in epidermal cells induced by chronic ultraviolet B (UVB) exposure. UVB-induced DNA photolesions, including cyclobutane–pyrimidine dimers (CPDs), promote mutations in skin cancer driver genes. In humans, CPDs are repaired by nucleotide excision repair (NER). Several commonly used and investigational medications negatively influence NER in experimental systems. Despite these molecules’ ability to decrease NER activity in vitro, the role of these drugs in enhancing skin cancer risk is unclear. In this study, we investigated four molecules (veliparib, resveratrol, spironolactone, and arsenic trioxide) with well-known NER-inhibitory potential in vitro, using UVB-irradiated CHO epithelial and HaCaT immortalized keratinocyte cell lines. Relative CPD levels, hypoxanthine phosphoribosyltransferase gene mutation frequency, cell viability, cell cycle progression, and protein expression were assessed. All four molecules significantly elevated CPD levels in the genome 24 h after UVB irradiation. However, veliparib, spironolactone, and arsenic trioxide reduced the mutagenic potential of UVB, while resveratrol did not alter UVB-induced mutation formation. UVB-induced apoptosis was enhanced by spironolactone and arsenic-trioxide treatment, while veliparib caused significantly prolonged cell cycle arrest and increased autophagy. Spironolactone also enhanced the phosphorylation level of mammalian target of rapamycin (mTOR), while arsenic trioxide modified UVB-driven mitochondrial fission. Resveratrol induced only mild changes in the cellular UVB response. Our results show that chemically inhibited NER does not result in increased mutagenic effects. Furthermore, the UVB-induced mutagenic potential can be paradoxically mitigated by NER-inhibitor molecules. We identified molecular changes in the cellular UVB response after NER-inhibitor treatment, which may compensate for the mitigated DNA repair. Our findings show that metabolic cellular response pathways are essential to consider in evaluating the skin cancer risk–modifying effects of pharmacological compounds.

Haplotypes of (-794(CATT)5-8/-173G>C) MIF gene polymorphisms and its soluble levels in basal cell carcinoma in western Mexican population

Basal cell carcinoma (BCC) is the most common dermatological neoplasms in Caucasian populations. In Mexico, a prevalence of 3.9 per 1000 habitants is estimated. Recently, the macrophage migration inhibitory factor (MIF) has been related to different types of cancer. Therefore, this study aimed to investigate the genetic association of haplotypes of [-794(CATT)5-8/-173G>C]MIF gene polymorphisms and its soluble levels in BCC. A total of 360 individuals were recruited for the study, that is, 180 of the total amounts were patients with BCC histologically confirmed and the remaining 180 individuals were identified as control subjects (CS). Both polymorphisms were genotyped by PCR and PCR-RFLP (restriction fragment length polymorphism), and MIF serum levels were measured by ELISA kit. A borderline difference was found between the 55 genotype and the susceptibility to BCC (5.6% vs 1.7% in BCC and CS, respectively, OR=3.7 and p=0.04). Furthermore, the haplotype 7G showed a significant association with BCC (p=0.02, OR=1.99). Concerning MIF soluble levels, patients with BCC showed a media of 2.1 ng/mL and CS showed 4.4 ng/mL, the comparison between groups was significant (p<0.01). Our findings suggest that the 55 genotype and the haplotype 7G are associated with the susceptibility to BCC; furthermore, a significant difference was found between MIF soluble levels in both study groups.

P53 in skin cancer: From a master player to a privileged target for prevention and therapy

The increasing incidence of skin cancer (SC) is a global health concern. The commonly reported side effects and resistance mechanisms have imposed the pursuit for new therapeutic alternatives. Moreover, additional preventive strategies should be adopted to strengthen prevention and reduce the rising number of newly SC cases. This review provides relevant insights on the role of p53 tumour suppressor protein in melanoma and non-melanoma skin carcinogenesis, also highlighting the therapeutic potential of p53-targeting drugs against SC. In fact, several evidences are provided demonstrating the encouraging outcomes achieved with p53-activating drugs, alone and in combination with currently available therapies in SC. Another pertinent perspective falls on targeting p53 mutations, as molecular signatures in premature phases of photocarcinogenesis, in future SC preventive approaches. Overall, this review affords a critical and timely discussion of relevant issues related to SC prevention and therapy. Importantly, it paves the way to future studies that may boost the clinical translation of p53-activating agents, making them new effective alternatives in precision medicine of SC therapy and prevention.

Basal Cell Carcinoma: A Comprehensive Review

Basal cell carcinoma (BCC) is the most common type of carcinoma worldwide. BCC development is the result of a complex interaction between environmental, phenotypic and genetic factors. However, despite the progress in the field, BCC biology and mechanisms of resistance against systemic treatments have been poorly investigated. The aim of the present review is to provide a revision of BCC histological and molecular features, including microRNA (miRNA) dysregulation, with a specific focus on the molecular basis of BCC systemic therapies. Papers from the last ten years regarding BCC genetic and phenotypic alterations, as well as the mechanism of resistance against hedgehog pathway inhibitors vismodegib and sonidegib were included. The involvement of miRNAs in BCC resistance to systemic therapies is emerging as a new field of knowledge.

Polydactyly Patient Carried a Mutation of PTCH1 Which Has Been Identified in Nevoid Basal Cell Nevus Syndrome

Polydactyly frequently exhibits autosomal dominant inheritance, which is characterized by supernumerary fingers or toes. The growth of the limb was controlled by three signaling pathways in three-dimensional axis. Sonic Hedgehog signaling, which controls the anterior to posterior (radial to ulnar) orientation has been suspected to be a main cause for polydactyly. To determine the pathogenesis of the patients with polydactyly, we recruited a polydactyly family with two patients. Taking advantage of next-generation sequencing technology, we applied whole-exome sequencing and Sanger sequencing to the proband and her daughter. The analysis of the whole-exome sequencing showed a heterozygous missense mutation c.3617G>A (p.R1206H) in the PTCH1 gene. The results of Sanger sequencing also verified this mutation. Our research discovered a candidate gene of polydactyly-PTCH1. We are the first to point out the relationship between polydactyly and PTCH1 mutation in human. As the PTCH1 gene mutations have been identified in nevoid basal cell nevus syndrome (NBCCS), and polydactyly is one phenotype of NBCCS, it may provide a new clue to the study of the genotype-phenotype correlations between the PTCH1 gene mutations and NBCCS.

Sonic Hedgehog Pathway Inhibition in the Treatment of Advanced Basal Cell Carcinoma

OPINION STATEMENT

Advanced basal cell carcinoma (BCC) represents a small proportion of BCCs that are not amenable to standard therapies due to lack of efficacy, high recurrence risk, and excessive morbidity. Implication of the Sonic hedgehog (Shh) pathway in the development of BCC has led to the development of systemic Shh pathway inhibitors, providing patients with advanced BCCs new treatment options and improved survival. There are currently two Food and Drug Administration (FDA)-approved Shh inhibitors, vismodegib and sonidegib, for advanced basal cell carcinomas. Vismodegib has approval for locally advanced BCCs (laBCC) and metastatic BCC (mBCC), while sonidegib has approval for laBCC. These agents have also been used for prevention in nevoid basal cell carcinoma syndrome and as neoadjuvant therapy before surgery, and we feel that there is a growing role of Shh inhibitors in these settings. Head-to-head randomized controlled trials comparing vismodegib to sonidegib are lacking. Adverse events can limit the utility of these medications by leading to treatment discontinuation in a large proportion of patients, and it is thus essential that prescribers be able to anticipate and manage the most frequent side effects of muscle spasms, alopecia, dysgeusia, nausea, and weight loss. Other Shh inhibitors, including the antifungal itraconazole, have been investigated in small trials, but further research is needed before recommending their routine clinical use. Additionally, there are several new agents under investigation that may have improved efficacy for resistant tumors by utilizing different mechanisms of action than the two currently approved medications.

Gene networks in basal cell carcinoma of the eyelid, analyzed using gene expression profiling

Basal cell carcinoma (BCC) is the most frequent malignant tumor of the eyelid; it progresses slowly and rarely metastasizes. However, BCC of the eyelid is partially invasive and can extend to the surrounding ocular adnexa even if appropriate treatment is performed. To understand the molecular mechanism underlying its pathogenesis, global gene expression analysis of surgical tissue samples of BCC of the eyelid (n=2) and normal human epidermal keratinocytes was performed using a GeneChip^® system. The histopathological examination of surgically removed eyelid tissues showed the tumor nest composed with small basaloid. In the samples from patients 1 and 2, 687 and 713 genes were identified, respectively, demonstrating ≥5.0-fold higher expression than that noted in normal human epidermal keratinocytes. For the 640 genes with upregulated expression in both patient samples, Ingenuity^® pathway analysis showed that the gene network in BCC of the eyelid included many BCC-associated genes, such as the following: BCL2 apoptosis regulator; Patched-1; and SRY-box 9. In addition, unique gene networks related to cancer cell growth, tumorigenesis, and cell survival were identified. These results of integrating microarray analyses provide further insights into the molecular mechanisms involved in BCC of the eyelid and may provide a therapeutic approach for this disease.

Cross-Talk between Wnt and Hh Signaling Pathways in the Pathology of Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most frequently occurring form of all cancers. The cost of care for BCC is one of the highest for all cancers in the Medicare population in the United States. Activation of Hedgehog (Hh) signaling pathway appears to be a key driver of BCC development. Studies involving mouse models have provided evidence that activation of the glioma-associated oncogene (GLI) family of transcription factors is a key step in the initiation of the tumorigenic program leading to BCC. Activation of the Wnt pathway is also observed in BCCs. In addition, the Wnt signaling pathway has been shown to be required in Hh pathway-driven development of BCC in a mouse model. Cross-talks between Wnt and Hh pathways have been observed at different levels, yet the mechanisms of these cross-talks are not fully understood. In this review, we examine the mechanism of cross-talk between Wnt and Hh signaling in BCC development and its potential relevance for treatment. Recent studies have identified insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1), a direct target of the Wnt/&beta;-catenin signaling, as the factor that binds to GLI1 mRNA and upregulates its levels and activities. This mode of regulation of GLI1 appears important in BCC tumorigenesis and could be explored in the treatment of BCCs.

Hedgehog signaling pathway: Epigenetic regulation and role in disease and cancer development

The evolutionarily conserved Hedgehog (Hh) signaling pathway have critical roles in development and homeostasis of tissues. Under physiological conditions, Hh is controlled at different levels via stem cell maintenance and tissue regeneration. Aberrant activation of this signaling pathway may occur in a wide range of human diseases including different types of cancer. In this review we present a concise overview on the key genes composing Hh signaling pathway and provide recent advances on the molecular mechanisms that regulate Hh signaling pathway from extracellular and receptors to the cytoplasmic and nuclear machinery with a highlight on the role of microRNAs. Furthermore, we focus on critical studies demonstrating dysregulation of the Hh pathway in human disease development, and potential therapeutic implications. Finally, we introduce recent therapeutic drugs acting as Shh signaling pathway inhibitors, including those in clinical trials and preclinical studies.

Establishment of basal cell carcinoma animal model in Chinese tree shrew (Tupaia belangeri chinensis)

Basal cell carcinoma (BCC) is the most common skin cancer worldwide, with incidence rates continuing to increase. Ultraviolet radiation is the major environmental risk factor and dysregulation of the Hedgehog (Hh) signaling pathway has been identified in most BCCs. The treatment of locally advanced and metastatic BBCs is still a challenge and requires a better animal model than the widely used rodents for drug development and testing. Chinese tree shrews (Tupaia belangeri chinensis) are closely related to primates, bearing many physiological and biochemical advantages over rodents for characterizing human diseases. Here, we successfully established a Chinese tree shrew BCC model by infecting tail skins with lentiviral SmoA1, an active form of Smoothened (Smo) used to constitutively activate the Hh signaling pathway. The pathological characteristics were verified by immunohistochemical analysis. Interestingly, BCC progress was greatly enhanced by the combined usage of lentiviral SmoA1 and shRNA targeting Chinese tree shrew p53. This work provides a useful animal model for further BCC studies and future drug discoveries.

Understanding the Molecular Genetics of Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common human cancer and represents a growing public health care problem. Several tumor suppressor genes and proto-oncogenes have been implicated in BCC pathogenesis, including the key components of the Hedgehog pathway, PTCH1 and SMO, the TP53 tumor suppressor, and members of the RAS proto-oncogene family. Aberrant activation of the Hedgehog pathway represents the molecular driver in basal cell carcinoma pathogenesis, with the majority of BCCs carrying somatic point mutations, mainly ultraviolet (UV)-induced, and/or copy-loss of heterozygosis in the PTCH1 gene. Recent advances in sequencing technology allowed genome-scale approaches to mutation discovery, identifying new genes and pathways potentially involved in BCC carcinogenesis. Mutational and functional analysis suggested PTPN14 and LATS1, both effectors of the Hippo–YAP pathway, and MYCN as new BCC-associated genes. In addition, emerging reports identified frequent non-coding mutations within the regulatory promoter sequences of the TERT and DPH3-OXNAD1 genes. Thus, it is clear that a more complex genetic network of cancer-associated genes than previously hypothesized is involved in BCC carcinogenesis, with a potential impact on the development of new molecular targeted therapies. This article reviews established knowledge and new hypotheses regarding the molecular genetics of BCC pathogenesis.

Histologic Mimics of Basal Cell Carcinoma

CONTEXT

- Basal cell carcinoma (BCC) is the most common human malignant neoplasm and is a frequently encountered diagnosis in dermatopathology. Although BCC may be locally destructive, it rarely metastasizes. Many diagnostic entities display morphologic and immunophenotypic overlap with BCC, including nonneoplastic processes, such as follicular induction over dermatofibroma; benign follicular tumors, such as trichoblastoma, trichoepithelioma, or basaloid follicular hamartoma; and malignant tumors, such as sebaceous carcinoma or Merkel cell carcinoma. Thus, misdiagnosis has significant potential to result in overtreatment or undertreatment.

OBJECTIVE

- To review key features distinguishing BCC from histologic mimics, including current evidence regarding immunohistochemical markers useful for that distinction.

DATA SOURCES

- Review of pertinent literature on BCC immunohistochemistry and differential diagnosis.

CONCLUSIONS

- In most cases, BCC can be reliably diagnosed by histopathologic features. Immunohistochemistry may provide useful ancillary data in certain cases. Awareness of potential mimics is critical to avoid misdiagnosis and resulting inappropriate management.

Pigmented Paraaxillary Located "Complex" Basal Cell Carcinoma Imitating clinically irritated Melanocytic Lesion - Succesfull Surgical Approach in Bulgarian Patient

BACKGROUND

Basal cell carcinoma (BCC) is the most frequently encountered neoplasm worldwide. While nodular BCC is the most frequent clinical subtype, other forms of BCC, such as superficial, cystic, morpheiform, infiltrative, and pigmented may also be encountered.

CASE PRESENTATION

We present the case of a 67-year-old male with a relatively well-defined infiltrative, pigmented plaque with multiple colours and peripheral growth situated in the right axillary region. The histopathologic examination performed after complete surgical excision of the tumour revealed a complex pigmented BCC with macronodular, fibroepithelioma-like, cystic, focally infiltrative and basosquamous features.

CONCLUSION

Uncommon locations of BCCs in sun-protected areas such as the axillary region require a higher degree of suspicion for diagnosis. The complex histology of the presented case, including subtypes with differing biologic attributes, emphasises the importance of histopathological examination in the diagnosis and therapeutic management of BCC.

Basal Cell Carcinoma Surgery: Simple Undermining Approach in Two Patients with Different Tumour Locations

Basal cell carcinoma (BCC) is the most common human malignancy, accounting for the majority of all non-melanoma skin cancers (NMSC). In the past several decades the worldwide incidence of BCC has constantly been increasing. Even though it is a slow growing tumour that, left untreated, rarely metastasizes, it has a distinctive invasive growth pattern, posing a considerable risk for local invasion and destruction of underlying tissues, such as muscle, cartilage, bone or vital structures. Advanced BCCs include such locally invasive or metastatic tumours. Complete surgical excision is the standard therapy for most uncomplicated BCC cases with good prognosis and cure rates. Treatment of advanced forms of BCCs poses significant therapeutic challenges, most often requiring complicated surgery, radiotherapy, and/or targeted therapies directed towards the sonic hedgehog signalling pathway (SHH). We present two cases of large BCCs located on the scalp and posterior thorax, which underwent surgical excision with clear margins, followed by reconstruction of the defect after extensive undermining of the skin.

Epigenetic Determinants of Cancer

SUMMARYEpigenetic changes are present in all human cancers and are now known to cooperate with genetic alterations to drive the cancer phenotype. These changes involve DNA methylation, histone modifiers and readers, chromatin remodelers, microRNAs, and other components of chromatin. Cancer genetics and epigenetics are inextricably linked in generating the malignant phenotype; epigenetic changes can cause mutations in genes, and, conversely, mutations are frequently observed in genes that modify the epigenome. Epigenetic therapies, in which the goal is to reverse these changes, are now one standard of care for a preleukemic disorder and form of lymphoma. The application of epigenetic therapies in the treatment of solid tumors is also emerging as a viable therapeutic route.

Comparison of PTCH1, COX-2, p53, and Ki-67 protein expression in basal cell carcinomas of nodular and superficial subtypes arising on the head and trunk

BACKGROUND

There is some evidence that basal cell carcinomas (BCCs) arising on different anatomic sites and developing to different histological subtypes differ in their pathophysiology. The expression of a number of proteins, including PTCH1, COX-2, p53, and Ki-67, is frequently altered in BCC development.

OBJECTIVES

This study sought to determine whether protein expression differs between BCCs at different anatomic sites and of different histological subtypes.

METHODS

Expression of PTCH1, COX-2, p53, and Ki-67 proteins was compared between: (i) BCCs arising on the head (n = 55) and trunk (n = 53), and (ii) nodular (n = 52) and superficial (n = 43) BCCs. The intensity of immunohistochemistry (IHC) staining (low, moderate, strong, very strong) for PTCH1 and COX-2 proteins was measured and the proportions of p53- and Ki-67-positive cells quantified.

RESULTS

The proportion of cells expressing Ki-67 was higher in tumor tissue than in non-malignant epidermis, whereas the opposite was found for PTCH1. The IHC staining intensity for PTCH1 was substantially greater in truncal BCCs than in BCCs on the head (odds ratio [OR] 3.82, 95% confidence interval [CI] 1.63-8.96). The intensity of staining for PTCH1 was greater for superficial than for nodular BCCs (OR 3.70, 95% CI 1.53-8.97), and superficial BCCs showed a higher proportion of Ki-67-positive cells (OR 5.57, 95% CI 1.66-18.67).

CONCLUSIONS

These differences suggest that the pathophysiology of BCC differs between lesions on the head and trunk and between nodular and superficial subtypes, perhaps indicating differences in their etiology.

Chemopreventive opportunities to control basal cell carcinoma: Current perspectives

Basal cell carcinoma (BCC) is a major health problem with approximately 2.8 million new cases diagnosed each year in the United States. BCC incidences have continued to rise due to lack of effective chemopreventive options. One of the key molecular characteristics of BCC is the sustained activation of hedgehog signaling through inactivating mutations in the tumor suppressor gene patch (Ptch) or activating mutations in Smoothened. In the past, several studies have addressed targeting the activated hedgehog pathway for the treatment and prevention of BCC, although with toxic effects. Other studies have attempted BCC chemoprevention through targeting the promotional phase of the disease especially the inflammatory component. The compounds that have been utilized in pre-clinical and/or clinical studies include green and black tea, difluoromethylornithine, thymidine dinucleotide, retinoids, non-steroidal anti-inflammatory drugs, vitamin D3, and silibinin. In this review, we have discussed genetic and epigenetic modifications that occur during BCC development as well as the current state of BCC pre-clinical and clinical chemoprevention studies.

Basal cell carcinoma-treatments for the commonest skin cancer

BACKGROUND

With an incidence of 70 to over 800 new cases per 100 000 persons per year, basal cell carcinoma (BCC) is a very common disease, accounting for about 80% of all cases of non-melanoma skin cancer. It very rarely metastasizes. A variety of treatments are available for the different subtypes and stages of BCC.

METHOD

This review is based on pertinent literature retrieved by a selective search in the Medline database, as well as the American Cancer Society guidelines on BCC and the German guidelines on BCC and skin cancer prevention.

RESULTS

The gold standard of treatment is surgical excision with histological control of excision margins, which has a 5-year recurrence rate of less than 3% on the face. For superficial BCC, approved medications such as imiquimod (total remission rate, 82-90%) and topical 5-fluorouracil (80%) are available, as is photodynamic therapy (71-87%). Other ablative methods (laser, cryosurgery) are applicable in some cases. Radiotherapy is an alternative treatment for invasive, inoperable BCC, with 5-year tumor control rates of 89-96%. Recently, drugs that inhibit an intracellular signaling pathway have become available for the treatment of locally advanced or metastatic BCC. Phase I and II clinical trials revealed that vismodegib was associated with objective response rates of 30-55% and tumor control rates of 80-90%. This drug was approved on the basis of a non-randomized trial with no control arm. It has side effects ranging from muscle cramps (71%) and hair loss (65%) to taste disturbances (55%) and birth defects.

CONCLUSION

The established, standard treatments are generally highly effective. Vismodegib is a newly approved treatment option for locally advanced BCC that is not amenable to either surgery or radiotherapy.

Efficacy and safety of vismodegib : a new therapeutic agent in the treatment of basal cell carcinoma

INTRODUCTION

Basal cell carcinoma (BCC) is the most common human malignancy. Treatment options for the minority of patients presenting with locally advanced inoperable or metastatic BCC are very limited. The hedgehog (Hh) pathway plays a crucial role in the pathogenesis of BCC. Recent advances in targeting this pathway have led to the development of a first-in-class, small-molecule oral Hh inhibitor, vismodegib (Erivedge®, Genentech).

AREAS COVERED

In this article, we review vismodegib with regard to its mechanism of action, clinical efficacy, safety and tolerability, and we consider the causes of emerging resistance to the drug.

EXPERT OPINION

Vismodegib is a welcome addition to the treatment paradigm for BCC. Approval was based on Phase II evidence, the patient number was relatively small, there was no control group or a comparator group and survival data have not been presented so longer term follow-up and larger exposure to the drug is required to fully appreciate its clinical utility into the future. With ongoing use of the drug in the nontrial population and further studies investigating its use in both early- and later-stage disease, we will get a better understanding of the drug and determine its place in the armamentarium against BCC.

Cutaneous basal cell carcinosarcomas: evidence of clonality and recurrent chromosomal losses

Cutaneous carcinosarcomas are heterogeneous group of tumors composed of malignant epithelial and mesenchymal components. Although mutation analyses have identified clonal changes between these morphologically disparate components in some subtypes of cutaneous carcinosarcoma, few cases have been analyzed thus far. To our knowledge, copy number variations (CNVs) and copy-neutral loss of heterozygosity (CN-LOH) have not been investigated in cutaneous carcinosarcomas. We analyzed 4 carcinosarcomas with basal cell carcinoma and osteosarcomatous components for CNVs/CN-LOH by comparative genomic hybridization/single-nucleotide polymorphism array, TP53 hot spot mutations by polymerase chain reaction and Sanger sequencing, and TP53 genomic rearrangements by fluorescence in situ hybridization. All tumors displayed multiple CNV/CN-LOH events (median, 7.5 per tumor). Three of 4 tumors displayed similar CNV/CN-LOH patterns between the epithelial and mesenchymal components within each tumor, supporting a common clonal origin. Recurrent changes included allelic loss at 9p21 (CDKN2A), 9q (PTCH1), and 17p (TP53). Allelic losses of chromosome 16 including CDH1 (E-cadherin) were present in 2 tumors and were restricted to the sarcomatous component. TP53 mutation analysis revealed an R248L mutation in both epithelial and mesenchymal components of 1 tumor. No TP53 rearrangements were identified. Our findings indicate that basal cell carcinosarcomas harbor CNV/CN-LOH changes similar to conventional basal cell carcinoma, with additional changes including recurrent 9p21 losses and a relatively high burden of copy number changes. In addition, most cutaneous carcinosarcomas show evidence of clonality between epithelial and mesenchymal components.

Noninvasive monitoring of basal cell carcinomas treated with systemic hedgehog inhibitors: pseudocysts as a sign of tumor regression

BACKGROUND

Oral hedgehog inhibitors (HHIs) have shown significant efficacy in the treatment of basal cell carcinoma (BCC). The evaluation of tumor regression has been performed using clinical photography and radiographic scans. Noninvasive imaging techniques, such as reflectance confocal microscopy (RCM) and high-definition optical coherence tomography (HD-OCT), have been shown to be valuable in detecting BCC in the skin.

OBJECTIVE

We monitored HHI-treated BCC using RCM and HD-OCT in vivo and correlated morphologic changes seen on imaging to changes in traditional histopathology.

METHODS

Six BCCs in 5 patients receiving HHIs (vismodegib or sonidegib) were examined by RCM and HD-OCT before and during treatment. Characteristic features were compared to histopathologic findings, including immunohistochemical analysis.

RESULTS

Characteristic features of BCC in RCM and HD-OCT decreased or disappeared completely during HHI treatment. Half of the clinically complete responding tumors still featured tumor residue. Pseudocystic structures ("empty" tumor nests in imaging) and widespread fibrosis (coarse bright fibers) were new findings and could be confirmed by histopathology.

LIMITATIONS

Our study was limited by the number of tumor samples and imaging timepoints.

CONCLUSION

Using RCM and HD-OCT, HHI-induced regression of BCC can be visualized noninvasively in the skin. The formation of pseudocysts and fibrosis were characteristic signs of BCC response to HHIs.

CRB1: one gene, many phenotypes

Mutations in the CRB1 gene cause severe retinal degenerations, which may present as Leber congenital amaurosis, early onset retinal dystrophy, retinitis pigmentosa, or cone-rod dystrophy. Some clinical features should alert the ophthalmologist to the possibility of CRB1 disease. These features are nummular pigmentation of the retina, atrophic macula, retinal degeneration associated with Coats disease, and a unique form of retinitis pigmentosa named para-arteriolar preservation of the retinal pigment epithelium (PPRPE). Retinal degenerations associated with nanophthalmos and hyperopia, or with keratoconus, can serve as further clinical cues to mutations in CRB1. Despite this, no clear genotype-phenotype relationship has been established in CRB1 disease. In CRB1-disease, as in other inherited retinal degenerations (IRDs), it is essential to diagnose the specific disease-causing gene for the disease as genetic therapy has progressed considerably in the last few years and might be applicable.

Mutations of the TERT promoter are common in basal cell carcinoma and squamous cell carcinoma

Telomerase is frequently expressed in cancer and contributes to carcinogenesis. Two recent publications report the identification of a set of recurrent mutations in melanoma in the promoter of the telomerase reverse transcriptase gene (TERT) that appears to be the result of mutagenesis from ultraviolet (UV) radiation. Both groups reported that the mutations increase the transcription of TERT. This prompted our search for similar mutations in two other UV-related skin cancers, basal cell carcinoma, and squamous cell carcinoma. We found that the activating TERT promoter mutations reported in melanoma are also frequent in squamous cell carcinoma (50%) and basal cell carcinoma, the latter including both sporadic tumors (78%) and tumors from patients with nevoid basal cell carcinoma syndrome (68%). These mutations were found in only 1 of 11 Bowen's disease (squamous cell carcinoma in situ) specimens, and in none of 15 non-malignant skin specimens and 57 blood specimens. The mutations were frequently homozygous or hemizygous, with little or no normal signal at the mutated positions. These data suggest that TERT promoter mutations are the most frequent putative oncogenic mutations in cutaneous cancer.

Epigenetic modifications by dietary phytochemicals: implications for personalized nutrition

In the last two decades, the study of epigenetic modification emerged as one of the major areas of cancer treatment targeted by dietary phytochemicals. Recent studies with various types of cancers revealed that the epigenetic modifications are associated with the food source corresponds to dietary phytochemicals. The dietary phytochemicals have been used in Asian countries for thousands of years to cure several diseases including cancer. They have been reported to modulate the several biological processes including histone modification, DNA methylation and non-coding microRNA expression. These events play a vital role in carcinogenesis. Various studies suggest that a number of dietary compounds present in vegetables, spices and other herbal products have epigenetic targets in cancer cells. Dietary phytochemicals have been reported to repair DNA damage by enhancing histone acetylation that helps to restrain cell death, and also alter DNA methylation. These phytochemicals are able to modulate epigenetic modifications and their targets to cure several cancers. Epigenetic aberrations dynamically contribute to cancer pathogenesis. Given the individualized traits of epigenetic biomarkers, the personalized nutrition will help us to prevent various types of cancer. In this review, we will discuss the effect of dietary phytochemicals on genetic and epigenetic modifications and how these modifications help to prevent various types of cancers and improve health outcomes.

Clinical variants, stages, and management of basal cell carcinoma

Basal cell carcinoma (BCC) is the most common paraneoplastic disease among human neoplasms. The tumor affects mainly photoexposed areas, most often in the head and seldom appears on genitalia and perigenital region. BCC progresses slowly and metastases are found in less than 0.5% of the cases; however, a considerable local destruction and mutilation could be observed when treatment is neglected or inadequate. Different variants as nodular, cystic, micronodular, superficial, pigment BCC are described in literature and the differential diagnosis in some cases could be difficult. The staging of BCC is made according to Tumor, Node, Metastasis (TNM) classification and is essential for performing the adequate treatment. Numerous therapeutic methods established for treatment of BCC, having their advantages or disadvantages, do not absolutely dissolve the risk of relapses. The early diagnostics based on the good knowledge and timely organized and adequate treatment is a precondition for better prognosis. Despite the slow progress and numerous therapeutic methods, the basal cell carcinoma should not be underestimated.

The molecular genetics of eyelid tumors: recent advances and future directions

BACKGROUND

Unprecedented recent advances in the molecular genetics of cutaneous malignancies have markedly improved our ability to diagnose, treat, and counsel patients with skin tumors. This review provides an update on molecular genetics of periocular cutaneous basal cell carcinoma, squamous cell carcinoma, sebaceous carcinoma, Merkel cell carcinoma, and malignant melanoma and describes how the knowledge of molecular genetics is translated into clinical practice.

METHODS

A literature search of peer-reviewed and indexed publications from 1965 to 2012 using the PubMed search engine was performed. Key terms included: molecular genetics, eyelid, basal cell carcinoma, squamous cell carcinoma, sebaceous adenoma, sebaceous epithelioma, sebaceoma, sebaceous carcinoma, Merkel cell carcinoma, and melanoma. Seminal articles prior to 1965 were selected from primary sources and reviews from the initial search. Articles were chosen based on pertinence to clinical, genetic, and therapeutic topics reviewed in this manuscript.

RESULTS

We reviewed the literature regarding the advances in molecular genetics of cutaneous basal cell carcinoma, squamous cell carcinoma, sebaceous neoplasia, Merkel cell carcinoma, and malignant melanoma, and possible future directions towards diagnosing and treating cutaneous tumors at the genetic level. Cell culture experiments, animal models, and molecular genetic studies on the patients' tumor tissues helped to elucidate genetic aberrations in these lesions. Cell culture experiments, animal studies and, ultimately, clinical trials provided means to test and develop novel therapeutic strategies, namely targeted therapy directed at specific molecular genetic defects. While remarkable progress has been made in this process, the complexity of the molecular genetics of skin tumors makes complete elucidation of the genetic mechanisms and the search for ideal therapies challenging.

CONCLUSIONS

The recent studies focusing on molecular genetics of cutaneous malignancies show promising results, thereby improving our ability to diagnose, treat and counsel patients with these lesions. Future studies will hopefully help unravel further molecular mechanisms involved in cutaneous neoplasia and provide insights into novel preventative and therapeutic modalities.

Nucleosome occupancy and gene regulation during tumorigenesis

Nucleosomes are the basic structural units of eukaryotic chromatin. In recent years, it has become evident that nucleosomes and their position, in concert with other epigenetic mechanisms (such as DNA methylation, histone modifications, changes in histone variants, as well as small noncoding regulatory RNAs) play essential roles in the control of gene expression. Here, we discuss the mechanisms and factors that regulate nucleosome position and gene expression in normal and cancer cells.

Molecular signatures of basal cell carcinoma susceptibility and pathogenesis: a genomic approach

Gene expression profiling can be useful for phenotypic classification, investigation of functional pathways, and to facilitate the search for disease risk genes through the integration of transcriptional data with available genomic information. To enhance our understanding of the genetic and molecular basis of basal cell carcinoma (BCC) we performed global gene expression analysis to generate a disease-associated transcriptional profile. A gene signature composed of 331 differentially expressed genes (DEGs) was generated from comparing 4 lesional and 4 site-matched control samples using Affymetrix Human Genome U95A microarrays. Hierarchical clustering based on the obtained gene signature separated the samples into their corresponding phenotype. Pathway analysis identified several significantly overrepresented pathways including PPAR-γ signaling, TGF-β signaling and lipid metabolism, as well as confirmed the importance of SHH and p53 in the pathogenesis of BCC. Comparison of our microarray data with previous microarray studies revealed 13 DEGs overlapping in 3 studies. Several of these overlapping genes function in lipid metabolism or are components of the extracellular matrix, suggesting the importance of these and related pathways in BCC pathogenesis. BCC-associated DEGs were mapped to previously reported BCC susceptibility loci including 1p36, 1q42, 5p13.3, 5p15 and 12q11-13. Our analysis also revealed transcriptional 'hot spots' on chromosome 5 which help to confirm (5p13 and 5p15) and suggest novel (5q11.2-14.3, 5q22.1-23.3 and 5q31-35.3) disease susceptibility loci/regions. Integrating microarray analyses with reported genetic information helps to confirm and suggest novel disease susceptibility loci/regions. Identification of these specific genomic and/or transcriptional targets may lead to novel diagnostic and therapeutic modalities.

Cancer genetics and epigenetics: two sides of the same coin?

Epigenetic and genetic alterations have long been thought of as two separate mechanisms participating in carcinogenesis. A recent outcome of whole exome sequencing of thousands of human cancers has been the unexpected discovery of many inactivating mutations in genes that control the epigenome. These mutations have the potential to disrupt DNA methylation patterns, histone modifications, and nucleosome positioning and hence, gene expression. Genetic alteration of the epigenome therefore contributes to cancer just as epigenetic process can cause point mutations and disable DNA repair functions. This crosstalk between the genome and the epigenome offers new possibilities for therapy.

A germline variant in the TP53 polyadenylation signal confers cancer susceptibility

To identify new risk variants for cutaneous basal cell carcinoma, we performed a genome-wide association study of 16 million SNPs identified through whole-genome sequencing of 457 Icelanders. We imputed genotypes for 41,675 Illumina SNP chip-typed Icelanders and their relatives. In the discovery phase, the strongest signal came from rs78378222[C] (odds ratio (OR) = 2.36, P = 5.2 × 10(-17)), which has a frequency of 0.0192 in the Icelandic population. We then confirmed this association in non-Icelandic samples (OR = 1.75, P = 0.0060; overall OR = 2.16, P = 2.2 × 10(-20)). rs78378222 is in the 3' untranslated region of TP53 and changes the AATAAA polyadenylation signal to AATACA, resulting in impaired 3'-end processing of TP53 mRNA. Investigation of other tumor types identified associations of this SNP with prostate cancer (OR = 1.44, P = 2.4 × 10(-6)), glioma (OR = 2.35, P = 1.0 × 10(-5)) and colorectal adenoma (OR = 1.39, P = 1.6 × 10(-4)). However, we observed no effect for breast cancer, a common Li-Fraumeni syndrome tumor (OR = 1.06, P = 0.57, 95% confidence interval 0.88-1.27).

Features of basal cell carcinomas in basal cell nevus syndrome

Basal cell nevus syndrome (BCNS) is an autosomal dominant genodermatosis that is characterized by early onset basal cell carcinomas (BCCs) that define the disease and often lead to diagnosis of the underlying syndrome. The objective of this study was to investigate the anatomic location, subtypes, and impact of BCCs on a group of 61 individuals affected with BCNS attending a research colloquium. Fifty individuals had at least one prior BCC with 22 participants having over 100 lesions. The median age of syndrome diagnosis was 11 years and median age of first BCC was 16 years. Males had more lesions on the upper back, upper extremities, and M-zone of the face, while females had more lesions on the scalp, back, and lower extremities. Pigmented BCCs were concentrated on the neck, upper trunk, and extremities. Subjects with >100 lesions showed wider anatomic distribution. The number of BCCs did not correlate with any of the other major features of the syndrome. Eighty percent of affected individuals reported great concern related to BCCs, citing the limitations and morbidity of available treatments. Vigilant surveillance, which was found to be inconsistent for participants in this study, is warranted. Future work should include development of a consensus guideline on skin examinations and strategies to optimize therapy of BCCs in this syndrome.

Hereditary tumour syndromes featuring basal cell carcinomas

Basal cell carcinoma (BCC) is the most frequent cutaneous malignancy worldwide. This skin tumour is characterized by a broad phenotypic variability and distinct histopathological subtypes. It shows slow, locally invasive growth and only rarely metastasizes. BCCs can occur either sporadically or in the context of genetic syndromes, including Gorlin syndrome, Bazex-Dupré-Christol syndrome, Rombo syndrome, Oley syndrome and xeroderma pigmentosum. Different genes and signalling routes have been shown to play an important role in the development and growth of these tumours, including the hedgehog and Wnt/β-catenin pathway. In some of the aforementioned hereditary disorders the underlying genetic defect is still unknown whereas in others several genes have been demonstrated to be involved. Currently, most therapeutic approaches are based on surgical measures. In the case of superficial BCCs, photodynamic therapy, 5-fluorouracil cream, imiquimod or radiotherapy also may be an option. Elucidation of the molecular mechanisms governing the manifestation of BCCs in monogenetically inherited tumour syndromes will not only contribute to a better understanding of the complex pathogenesis of these tumours but might pave the way to the development of noninvasive, specific and molecule-based therapeutic strategies in the near future.