Molecular diagnosis of basal cell carcinoma and other basaloid cell neoplasms of the skin by the quantification of Gli1 transcript levels

Utility of GLI1 RNA Chromogenic in Situ Hybridization in Distinguishing Basal Cell Carcinoma From Histopathologic Mimics

Basal cell carcinoma (BCC) is the most common human malignancy and is a leading cause of nonmelanoma skin cancer-related morbidity. BCC has several histologic mimics which may have treatment and prognostic implications. Furthermore, BCC may show alternative differentiation toward a variety of cutaneous structures. The vast majority of BCCs harbor mutations in the hedgehog signaling pathway, resulting in increased expression of the GLI family of transcription factors. GLI1 immunohistochemistry has been shown to discriminate between several tumor types but demonstrates high background signal and lack of specificity. In this study, we evaluated the utility of GLI1 RNA chromogenic in situ hybridization (CISH) as a novel method of distinguishing between BCC and other epithelial neoplasms. Expression of GLI1 by RNA CISH was retrospectively evaluated in a total of 220 cases, including 60 BCCs, 37 squamous cell carcinomas (SCCs) including conventional, basaloid, and human papillomavirus infection (HPV)-associated tumors, 16 sebaceous neoplasms, 10 Merkel cell carcinomas, 58 benign follicular tumors, and 39 ductal tumors. The threshold for positivity was determined to be greater than or equal to 3 GLI1 signals in at least 50% of tumor cells. Positive GLI1 expression was identified in 57/60 BCCs, including metastatic BCC, collision lesions with SCC, and BCCs with squamous, ductal, or clear cell differentiation or with other unusual features compared to 1/37 SCCs, 0/11 sebaceous carcinomas, 0/5 sebaceomas, 1/10 Merkel cell carcinomas, 0/39 ductal tumors, and 28/58 follicular tumors. With careful evaluation, GLI1 RNA CISH is highly sensitive (95%) and specific (98%) in distinguishing between BCC and nonfollicular epithelial neoplasms. However, GLI1 CISH is not specific for distinguishing BCC from most benign follicular tumors. Overall, detection of GLI1 RNA by CISH may be a useful tool for precise classification of histologically challenging basaloid tumors, particularly in the setting of small biopsy specimens, metaplastic differentiation, or metastatic disease.

Updates on the Systemic Treatment of Advanced Non-melanoma Skin Cancer

Non-melanoma skin cancers (NMSCs), which represent a diverse group of cutaneous malignancies, are the most common forms of human neoplasia. The incidence of these diseases is increasing due to a number of factors, including that of increasing human lifespans. The majority of NMSCs are basal cell carcinomas (BCC) and cutaneous squamous cell carcinomas (cSCC), with the remainder being various rare skin cancers, including extramammary Paget's disease (EMPD), Merkel cell carcinoma (MCC), and several skin adnexal carcinomas. Of these, MCC usually shows aggressive behavior with a high mortality rate. On the other hand, BCC, cSCC, EMPD, and skin adnexal tumors usually show an indolent clinical course and metastasize only rarely. Nevertheless, the metastatic forms of these tumors commonly lead to poor patient outcome. A definitive management strategy for the treatment of advanced NMSC has not been established, mainly due to their rarity and lack of reliable information based on well-controlled randomized trials. Chemotherapeutic regimens for treatment of these diseases have been mainly based on the observations of isolated, small case series or clinical trials with a limited numbers of patients. However, accumulating evidence regarding their pathobiological backgrounds as well as recent advances in molecular biotechnology have facilitated the development of novel drugs for treatment of these diseases. Over the past decade, the U.S. Food and Drug Administration has approved several molecular targeting therapies, including Hedgehog inhibitors for BCC, monoclonal antibodies targeting anti-programmed death ligand-1 and anti- programmed cell death 1 (PD-1) for MCC, and anti-PD-1 for cSCC. Here, we review their clinical utility and discuss updated systemic treatment strategies for advanced NMSC.

Diagnosis and Management of Basal Cell Carcinoma

OPINION STATEMENT

Basal cell carcinomas (BCCs) are common skin cancers that tend to appear on sun-exposed skin. Pathobiologically, activation of the Hedgehog signaling pathway characterizes the majority of cases. In general, BCCs are slow-growing and rarely metastasize. Nevertheless, they are locally invasive and can be destructive. While typical cases are diagnosed based on clinical findings, the clinicopathological manifestations are varied. Consequently, skin biopsy is essential to confirm the diagnosis and evaluate the risk of recurrence. In the treatment of primary lesions, the initial goal is to complete tumor removal, whether by conventional surgical excision, Mohs micrographic surgery, cryosurgery, electrodesiccation and curettage, topical application of imiquimod or fluorouracil, photodynamic therapy, or radiation therapy. Of these treatments, surgical excision and Mohs surgery are the most commonly used because of their association with a low recurrence rate and the ability to confirm residual tumor pathologically. However, other treatment options may be preferred according to patient condition, tumor location, and risk of recurrence. In the treatment of metastatic or locally advanced lesions, smoothened inhibitors, which inhibit Hedgehog signaling pathway activation, were recently approved and impressive tumor shrinkage effects have been described. Although the exact prognosis of metastatic BCC has not been analyzed, it is probably poor due to the rarity of such condition. However, emerging molecular targeting agents hold therapeutic promise.

Immunohistochemical visualization of the signature of activated Hedgehog signaling pathway in cutaneous epithelial tumors

Activation of the Hedgehog (HH) signaling pathway plays a critical role in the development of basal cell carcinoma (BCC). HH signaling activity is produced by nuclear translocation of transcription factors, glioma-associated oncogene homolog (GLI). Among three GLI subfamilies, GLI1 is the only full-length transcriptional activator, and its nuclear localization is recognized as a signature event in HH signaling activation. However, limited published work has investigated the nuclear staining of GLI1 protein in human tumor tissue samples by immunohistochemical analysis. In this study, we performed immunohistochemical staining of GLI1 in 382 cases of cutaneous epithelial tumors, including 196 BCC cases, using rabbit monoclonal antihuman GLI1 antibody (C68H3). As a result, 98.2% cases of BCC showed a diffuse and strong nuclear staining pattern regardless of the histological subtype. Positive staining was mainly restricted to the tumor nests, while the overlying epidermis was negative suggesting specificity of the antibody. In further analysis of other cutaneous epithelial tumors, 100% (4/4) cases of trichoblastoma, 15.1% (5/33) Bowen's disease, 3.5% (1/28) actinic keratosis and 12.5% (4/32) squamous cell carcinoma showed the nuclear staining pattern of GLI1. This suggested that HH signaling is also dysregulated in some other cutaneous malignant tumors. In conclusion, the C68H3 antibody is a useful tool for revealing activation of HH signaling in immunohistochemical analysis.

Downregulation of the Sonic Hedgehog/Gli pathway transcriptional target Neogenin-1 is associated with basal cell carcinoma aggressiveness

Basal Cell Carcinoma (BCC) is one of the most diagnosed cancers worldwide. It develops due to an unrestrained Sonic Hedgehog (SHH) signaling activity in basal cells of the skin. Certain subtypes of BCC are more aggressive than others, although the molecular basis of this phenomenon remains unknown. We have previously reported that Neogenin-1 (NEO1) is a downstream target gene of the SHH/GLI pathway in neural tissue. Given that SHH participates in epidermal homeostasis, here we analyzed the epidermal expression of NEO1 in order to identify whether it plays a role in adult epidermis or BCC. We describe the mRNA and protein expression profile of NEO1 and its ligands (Netrin-1 and RGMA) in human and mouse control epidermis and in a broad range of human BCCs. We identify in human BCC a significant positive correlation in the levels of NEO1 receptor, NTN-1 and RGMA ligands with respect to GLI1, the main target gene of the canonical SHH pathway. Moreover, we show via cyclopamine inhibition of the SHH/GLI pathway of ex vivo cultures that NEO1 likely functions as a downstream target of SHH/GLI signaling in the skin. We also show how Neo1 expression decreases throughout BCC progression in the K14-Cre:Ptch1^lox/lox mouse model and that aggressive subtypes of human BCC exhibit lower levels of NEO1 than non-aggressive BCC samples. Taken together, these data suggest that NEO1 is a SHH/GLI target in epidermis. We propose that NEO1 may be important in tumor onset and is then down-regulated in advanced BCC or aggressive subtypes.

Basal cell carcinoma of the skin (part 1): epidemiology, pathology and genetic syndromes

Basal cell carcinoma (BCC) is the most common skin cancer worldwide with increasing incidence, but difficult to assess due to the current under registration practice. Despite the low mortality rate, BCC is a cause of great morbidity and an economic burden to health services. There are several risk factors that increase the risk of BCC and partly explain its incidence. Low-penetrance susceptibility alleles, as well as genetic alterations in signaling pathways, namely SHH pathway, also contribute to the carcinogenesis. BCC associate with several genetic syndromes, of which basal cell nevus syndrome is the most common.

Vismodegib induces significant clinical response in locally advanced trichoblastic carcinoma

Patients with advanced basal cell carcinoma due to local extension or metastatic disease were previously at a therapeutic impasse. Targeted inhibition of the sonic hedgehog pathway by vismodegib represents a new therapeutic strategy. Adnexal carcinomas are rare malignant skin tumours derived from epithelial annexes. Conventional treatment of adnexal tumours is based on surgical excision. Although the radiosensitivity of adnexal carcinomas has not been established, radiotherapy could be offered alone or in combination in locally advanced or inoperable disease. Chemotherapy represents a therapeutic option in the treatment of metastatic adnexal tumours. Currently there is no effective treatment for these tumours when they become metastatic or unresectable, and treatment is palliative. Sunitinib represents a new therapeutic strategy, with efficiency described in the literature for a small number of patients. However, its efficacy is partial, and its tolerance is not always good. We report a patient with trichoblastic carcinoma, initially diagnosed as basal cell carcinoma, treated effectively with vismodegib. The remarkable response we have observed in this patient suggests an encouraging therapeutic role of vismodegib in trichoblastic carcinoma that should be evaluated in a carefully designed trial.

Markers for Sebaceoma Show a Spectrum of Cell Cycle Regulators, Tumor Suppressor Genes, and Oncogenes

BACKGROUND

Sebaceoma is a tumor for which the causative oncogenes are not well-understood. Sebaceomas demonstrate some histopathologic features similar to basal cell carcinoma (BCC), such as palisading borders and basaloid cells with additional features, including foamy cytoplasm and indented nuclei.

AIMS

We examine multiple cell-cycle, oncogene, and tumor suppressor gene markers in sebaceomas, to try to find some suitable biological markers for this tumor, and compare with other published studies.

MATERIALS AND METHODS

We investigated a panel of immunohistochemical (IHC) stains that are important for cellular signaling, including a cell cycle regulator, tumor suppressor gene, oncogene, hormone receptor, and genomic stability markers in our cohort of sebaceomas. We collected 30 sebaceomas from three separate USA dermatopathology laboratories. The following IHC panel: Epithelial membrane antigen (EMA)/CD227, cytokeratin AE1/AE3, cyclin D1, human breast cancer 1 protein (BRCA-1), C-erb-2, Bcl-2, human androgen receptor (AR), cyclin-dependent kinase inhibitor 1B (p27(kip1)), p53, topoisomerase II alpha, proliferating cell nuclear antigen, and Ki-67 were tested in our cases.

RESULTS

EMA/CD227 was positive in the well-differentiated sebaceomas (13/30). Cyclin-dependent kinase inhibitor 1B was positive in tumors with intermediate differentiation (22/30). The less well-differentiated tumors failed to stain with EMA and AR. Most of the tumors with well-differentiated palisaded areas demonstrated positive staining for topoisomerase II alpha, p27(kip1), and p53, with positive staining in tumoral basaloid areas (22/30). Numerous tumors were focally positive with multiple markers, indicating a significant degree of variability in the complete group.

CONCLUSIONS

Oncogenes, tumor suppressor genes, cell cycle regulators, and hormone receptors are variably expressed in sebaceomas. Our results suggest that in these tumors, selected marker staining seems to correlate with tumor differentiation; that is, well-differentiated tumors as a group stained with EMA and AR, and palisaded areas demonstrated consistent p53, topoisomerase II alpha and p27(kip1) staining. In contrast, less well-differentiated areas stained with a different spectrum of markers.

Neural Hedgehog signaling maintains stem cell renewal in the sensory touch dome epithelium

The touch dome is a highly patterned mechanosensory structure in the epidermis composed of specialized keratinocytes in juxtaposition with innervated Merkel cells. The touch dome epithelium is maintained by tissue-specific stem cells, but the signals that regulate the touch dome are not known. We identify touch dome stem cells that are unique among epidermal cells in their activated Hedgehog signaling and ability to maintain the touch dome as a distinct lineage compartment. Skin denervation reveals that renewal of touch dome stem cells requires a perineural microenvironment, and deleting Sonic hedgehog (Shh) in neurons or Smoothened in the epidermis demonstrates that Shh is an essential niche factor that maintains touch dome stem cells. Up-regulation of Hedgehog signaling results in neoplastic expansion of touch dome keratinocytes but no Merkel cell neoplasia. These findings demonstrate that nerve-derived Shh is a critical regulator of lineage-specific stem cells that maintain specialized sensory compartments in the epidermis.

Ber-EP4 is a useful marker for follicular germinative cell differentiation of cutaneous epithelial neoplasms

Ber-EP4 is a monoclonal antibody that recognizes 34-kDa and 39-kDa non-covalently linked glycopolypeptides expressed by most human epithelial cells and carcinomas. In this study, we performed immunohistochemical staining of 31 cases of basal cell carcinoma (BCC); 20 cases of trichoblastoma (TB), including ten cases of nodular type, eight cases of cribriform type (trichoepithelioma) and two cases of columnar type (desmoplastic trichoepithelioma); 16 cases of actinic keratosis (AK); and 10 cases each of Bowen's disease, poroma and seborrheic keratosis. Six cases of BCC and AK were co-lesions of both neoplasms. In normal skin tissue, Ber-EP4 reacted positively with the secretory portion of eccrine glands and follicular germinative cells at the lower end of catagen hairs. Neoplastic cells in 97% of cases with BCC reacted positively with Ber-EP4 in at least 5% of neoplastic cells. Those in 90% with nodular type TB and 50% with trichoepithelioma also reacted positively in at least 5% of neoplastic cells. No cases of poroma, seborrheic keratosis, AK or Bowen's disease were immunohistochemically positive for Ber-EP4 in neoplastic cells. In all six cases with co-lesions of BCC and AK, neoplastic cells of BCC reacted positively with Ber-EP4 and those of AK were negative. Immunohistochemical examination using the Ber-EP4 antibody is a useful tool for diagnosing neoplasms with follicular germinative differentiation, such as TB, TE or BCC, and for differentiating those from squamous cell carcinoma in situ, poroma or seborrheic keratosis.

Multimodal imaging to study the morphochemistry of basal cell carcinoma

Basal cell carcinoma is the most abundant malignant neoplasm in humans, the pathology of which is characterized by an abnormal proliferation of basal cells. Basal cell carcinoma can show a variety of different morphologies, which are based on different cellular biology. Furthermore, the carcinoma often grows invisibly to the eye imbedded in the surrounding skin. Therefore, in some cases its clinical detection is challenging. Thus, our work aims at establishing an unsupervised tissue classification method based on multimodal imaging and the application of chemometrics to discriminate basal cell carcinoma from non-diseased tissue. A case study applying multimodal imaging to ex-vivo sections of basal cell carcinoma is presented. In doing so, we apply a combination of various linear and non-linear imaging modalities, i.e. fluorescence, Raman and second-harmonic generation microscopy, to study the morphochemistry of basal cell carcinoma. The joint information content obtained by such multimodal approach in studying various aspects of the malignant tissue alterations associated with basal cell carcinoma is discussed.

Elastic fiber staining and cytokeratin 15 expression pattern in trichoepithelioma and basal cell carcinoma

Trichoepithelioma (TE) is a benign neoplasm of the skin that resembles basal cell carcinoma (BCC) in its clinical and histological features. In this study, we evaluate the usefulness of elastic fiber staining and cytokeratin 15 expression pattern in terms of distinguishing TE from BCC. Eleven TE and 17 BCC were examined histochemically and immunohistochemically. It was found that BCC contain more elastic fiber than TE, and that more TE show peripheral localization than BCC in cytokeratin 15 expression patterns. The present study shows that elastic fiber staining and cytokeratin 15 expression pattern may aid the differentiation of TE from BCC.

Epidermal hyperplasia and oral carcinoma in mice overexpressing the transcription factor ATF3 in basal epithelial cells

ATF3 is a highly conserved eukaryotic transcription factor that is ubiquitously upregulated transcriptionally during cellular responses to a variety of stresses, in particular DNA damage. However, the role of ATF3 in the DNA damage response is unclear. Transgenic mice that overexpress human ATF3 in basal epithelial cells under the control of the bovine keratin 5 (K5) promoter were constructed and characterized for epidermal alterations. Strong, nuclear expression of the exogenous ATF3 protein was seen in basal cells of the epidermis, hair follicles, and oral mucosa. Hyperplastic changes in the K5-expressing, outer root sheath (ORS) cells of the hair follicle were observed in young mice, resulting in multiple layers of ORS cells in the mature follicle and large aberrantly shaped follicles. Mild hyperplasia of the interfollicular epidermis was also noted, increasing with age. However, no epidermal tumors were identified in BK5.ATF3 mice observed for 16 mo. At 16 mo of age, most transgenic mice exhibited multi-focal areas of hyperplasia and dysplasia in the oral mucosa, with cellular atypia and underlying acute inflammatory changes. Neoplastic lesions were also seen in the oral cavity of BK5.ATF3 mice, including oral squamous cell carcinoma (60% incidence) and basal cell tumors with follicular differentiation (70% incidence), but not in non-transgenic FVB/N littermates. Heterogeneous nuclear expression (or stabilization) of p53 protein was seen in some oral dysplasias, with a patchy distribution primarily in the least differentiated layers of the lesions. This represents the first indication that ATF3 may have oncogenic properties in epithelial cells.

Investigation of the molecular profile of basal cell carcinoma using whole genome microarrays

Background

Skin cancer accounts for 1/3 of all newly diagnosed cancer. Although seldom fatal, basal cell carcinoma (BCC) is associated with severe disfigurement and morbidity. BCC has a unique interest for researchers, as although it is often locally invasive, it rarely metastasises. This paper, reporting the first whole genome expression microarray analysis of skin cancer, aimed to investigate the molecular profile of BCC in comparison to non-cancerous skin biopsies. RNA from BCC and normal skin specimens was analysed using Affymetrix whole genome microarrays. A Welch t-test was applied to data normalised using dCHIP to identify significant differentially-expressed genes between BCC and normal specimens. Principal component analysis and support vector machine analysis were performed on resulting genelists, Genmapp was used to identify pathways affected, and GOstat aided identification of areas of gene ontology more highly represented on these lists than would be expected by chance.

Results

Following normalisation, specimens clustered into groups of BCC specimens and of normal skin specimens. Of the 54,675 gene transcripts/variants analysed, 3,921 were differentially expressed between BCC and normal skin specimens. Of these, 2,108 were significantly up-regulated and 1,813 were statistically significantly down-regulated in BCCs.

Conclusion

Functional gene sets differentially expressed include those involved in transcription, proliferation, cell motility, apoptosis and metabolism. As expected, members of the Wnt and hedgehog pathways were found to be significantly different between BCC and normal specimens, as were many previously undescribed changes in gene expression between normal and BCC specimens, including basonuclin2 and mrp9. Quantitative-PCR analysis confirmed our microarray results, identifying novel potential biomarkers for BCC.

Genética molecular aplicada ao câncer cutâneo não melanoma

Os cânceres cutâneos não melanoma são as neoplasias malignas mais comuns em humanos. O carcinoma basocelular e o carcinoma espinocelular representam cerca de 95% dos cânceres cutâneos não melanoma, o que os torna um crescente problema para a saúde pública mundial devido a suas prevalências cada vez maiores. As alterações genéticas que ocorrem no desenvolvimento dessas malignidades cutâneas são apenas parcialmente compreendidas, havendo muito interesse no conhecimento e determinação das bases genéticas dos cânceres cutâneos não melanoma que expliquem seus fenótipos, comportamentos biológicos e potenciais metastáticos distintos. Apresenta-se uma revisão atualizada da genética molecular aplicada aos cânceres cutâneos não melanoma, em especial ao carcinoma basocelular e carcinoma espinocelular, enfatizando os mais freqüentes genes e os principais mecanismos de instabilidade genômica envolvidos no desenvolvimento dessas malignidades cutâneas.

Basal cell carcinoma: biology, morphology and clinical implications

Basal cell carcinoma (BCC) is the most common malignant neoplasm of humans. Rising dramatically in incidence in North America, as likely reflects changing habits of the population and a move from more northerly climes to the sunbelt of the Southern and Southwestern United States, the incidence is surely to rise even higher in the future. The last decade has seen significant advances in our understanding of BCC biology and novel approaches to therapy, which hinge upon accurate diagnosis and subclassification by pathologists. The purpose of this review article is to summate the research advances in our understanding of BCC biology and to acquaint pathologists and clinicians to the practical issues in BCC diagnosis and subclassification which flow there from.