Basal cell carcinoma - molecular biology and potential new therapies

Patched Receptors Sense, Interpret, and Establish an Epidermal Hedgehog Signaling Gradient

By using the sensitivity of single-molecule fluorescent in situ hybridization, we have precisely quantified the levels and defined the temporal and spatial distribution of Hedgehog signaling activity during embryonic skin development and discovered that there is a Hedgehog signaling gradient along the proximal-distal axis of developing hair follicles. To explore the contribution of Hedgehog receptors Ptch1 and Ptch2 in establishing the epidermal signaling gradient, we quantitated the level of pathway activity generated in Ptch1- and Ptch1;Ptch2-deficient skin and defined the contribution of each receptor to regulation of the levels of Hedgehog signaling identified in wild-type skin. Moreover, we show that both the cellular phenotype and level of pathway activity featured in Ptch1;Ptch2-deficient cells faithfully recapitulates the Peak level of endogenous Hedgehog signaling detected at the base of developing follicles, where the concentration of endogenous Shh is predicted to be highest. Taken together, these data show that both Ptch1 and Ptch2 play a crucial role in sensing the concentration of Hedgehog ligand and regulating the appropriate dose-dependent response.

The Use of Noninvasive Optical Coherence Tomography to Monitor the Treatment Progress of Vismodegib and Imiquimod 5% Cream in a Transplant Patient with Advanced Basal Cell Carcinoma of the Nose

Immunosuppressed transplant recipients have increased risk for the development of basal cell carcinoma skin cancers. While oral vismodegib therapy has been successful in treating locally advanced basal cell tumors, few studies document its use and efficacy in organ transplant patients. In this immunocompromised population, topical imiquimod 5% cream has been shown to be an effective and well-tolerated option for superficial and nodular basal cell carcinomas. To the authors' knowledge, no data documents the use of optical coherence tomography, a noninvasive imaging technique, to monitor progress of such combined therapies on in vivo skin. The authors report the successful treatment of an extensive basal cell carcinoma on the nose of an immunosuppressed 54-year-old Caucasian man with a history of kidney and pancreas transplantations. By combining continuous noninvasive lesion monitoring with vismodegib 150mg/d therapy and adjuvant imiquimod 5% topical cream, the patient showed complete disease clearance on clinical, optical coherence tomography, and histological evaluation. This report supports the feasibility and efficacy of nonsurgical treatment of basal cell lesions in complicated transplant patients and the need for individualized treatment plans. A noninvasive follow-up tool, especially during nonsurgical therapy, is of critical value to ensure the best possible treatment outcome for the patient.

AKT1 Activation is Obligatory for Spontaneous BCC Tumor Growth in a Murine Model that Mimics Some Features of Basal Cell Nevus Syndrome

Patients with basal cell nevus syndrome (BCNS), also known as Gorlin syndrome, develop numerous basal cell carcinomas (BCC) due to germline mutations in the tumor suppressor PTCH1 and aberrant activation of Hedgehog (Hh) signaling. Therapies targeted at components of the Hh pathway, including the smoothened (SMO) inhibitor vismodegib, can ablate these tumors clinically, but tumors recur upon drug discontinuation. Using SKH1-Ptch1^+/- as a model that closely mimics the spontaneous and accelerated growth pattern of BCCs in patients with BCNS, we show that AKT1, a serine/threonine protein kinase, is intrinsically activated in keratinocytes derived from the skin of newborn Ptch1^+/- mice in the absence of carcinogenic stimuli. Introducing Akt1 haplodeficiency in Ptch1^+/- mice (Akt1^+/- Ptch1^+/-) significantly abrogated BCC growth. Similarly, pharmacological inhibition of AKT with perifosine, an alkyl phospholipid AKT inhibitor, diminished the growth of spontaneous and UV-induced BCCs. Our data demonstrate an obligatory role for AKT1 in BCC growth, and targeting AKT may help reduce BCC tumor burden in BCNS patients. Cancer Prev Res; 9(10); 794-802. ©2016 AACR.

Immune-competent human skin disease models

All skin diseases have an underlying immune component. Owing to differences in animal and human immunology, the majority of drugs fail in the preclinical or clinical testing phases. Therefore animal alternative methods that incorporate human immunology into in vitro skin disease models are required to move the field forward. This review summarizes the progress, using examples from fibrosis, autoimmune diseases, psoriasis, cancer and contact allergy. The emphasis is on co-cultures and 3D organotypic models. Our conclusion is that current models are inadequate and future developments with immune-competent skin-on-chip models based on induced pluripotent stem cells could provide a next generation of skin models for drug discovery and testing.

Reciprocal interplay between thyroid hormone and microRNA-21 regulates hedgehog pathway-driven skin tumorigenesis

The thyroid hormone-inactivating (TH-inactivating) enzyme type 3 iodothyronine deiodinase (D3) is an oncofetal protein that is rarely expressed in adult life but has been shown to be reactivated in the context of proliferation and neoplasms. D3 terminates TH action within the tumor microenvironment, thereby enhancing cancer cell proliferation. However, the pathological role of D3 and the contribution of TH metabolism in cancer have yet to be fully explored. Here, we describe a reciprocal regulation between TH action and the cancer-associated microRNA-21 (miR21) in basal cell carcinoma (BCC) skin tumors. We found that, besides being negatively regulated by TH at the transcriptional level, miR21 attenuates the TH signal by increasing D3 levels. The ability of miR21 to positively regulate D3 was mediated by the tumor suppressor gene GRHL3, a hitherto unrecognized D3 transcriptional inhibitor. Finally, in a BCC mouse model, keratinocyte-specific D3 depletion markedly reduced tumor growth. Together, our results establish TH action as a critical hub of multiple oncogenic pathways and provide functional and mechanistic evidence of the involvement of TH metabolism in BCC tumorigenesis. Moreover, our results identify a miR21/GRHL3/D3 axis that reduces TH in the tumor microenvironment and has potential to be targeted as a therapeutic approach to BCC.

Free perforating branch flap for primary repairing the huge soft-tissue defects on the scalp and face

OBJECTIVE

This study aimed to explore the effect of free perforating branch flap on the reconstruction of huge soft-tissue defects on the scalp and face.

METHODS

Sixteen cases of huge soft-tissue defects on the scalp and face were reconstructed by nine latissimus dorsi-free perforator flaps and seven anterolateral thigh-free perforator flaps. The defects area was from 12 cm× 7 cm to 20 cm × 11 cm, while the flaps area was from 14 cm × 8 cm to 23 cm × 12 cm. The survival, planeness, chromatic aberration, radiotherapy toleration of flap and the function, scar of donor site were observed postoperatively.

RESULT

All of the flaps were survived completely, and 15 cases presented for primary reconstruction; one underwent secondary reconstruction. One of the patients died one-year postoperatively due to intracranial tumor recurrence and the others had no recurrence. All of the flaps showed perfect shape and appropriate thickness. No roentgen ulcer was observed except for some extent of chromatic aberration. The donor-site scar was larvaceous and the function was good.

CONCLUSION

This study indicated that the latissimus dorsi-free perforator flap or anterolateral thigh-free perforator flap was an ideal choice for the reconstruction of defects on the scalp and face.

Ionizing Radiation Exposure and Basal Cell Carcinoma Pathogenesis

This commentary summarizes studies showing risk of basal cell carcinoma (BCC) development in relationship to environmental, occupational and therapeutic exposure to ionizing radiation (IR). BCC, the most common type of human cancer, is driven by the aberrant activation of hedgehog (Hh) signaling. Ptch, a tumor suppressor gene of Hh signaling pathway, and Smoothened play a key role in the development of radiation-induced BCCs in animal models. Epidemiological studies provide evidence that humans exposed to radiation as observed among the long-term, large scale cohorts of atomic bomb survivors, bone marrow transplant recipients, patients with tinea capitis and radiologic workers enhances risk of BCCs. Overall, this risk is higher in Caucasians than other races. People who were exposed early in life develop more BCCs. The enhanced IR correlation with BCC and not other common cutaneous malignancies is intriguing. The mechanism underlying these observations remains undefined. Understanding interactions between radiation-induced signaling pathways and those which drive BCC development may be important in unraveling the mechanism associated with this enhanced risk. Recent studies showed that Vismodegib, a Smoothened inhibitor, is effective in treating radiation-induced BCCs in humans, suggesting that common strategies are required for the intervention of BCCs development irrespective of their etiology.

Clinical significance of IL-2 and IL-10 gene polymorphisms and serum levels in patients with basal-cell carcinoma

Materials & methods: Polymorphic variants of IL-2 gene (-330 T/G and +166 G/T), IL-10 gene (-1082 G/A and -819 C/T) and serum cytokines concentrations in the group of 179 patients with BCC and 173 controls were analyzed. Results: The presence of the IL-2 -330 GG genotype or IL-10 -1082 GA increased the risk of BCC (OR 3.68) (OR 3.07). IL-10 -1082 AA or GA and IL-2 -330 GG genotype increased the risk of BCC (OR 9.63). IL-2 serum levels were significantly lower (p < 0.0004) in BCC patients while IL-10 concentration was significantly higher (p < 0.00001). Conclusion: The polymorphisms in IL-2 and IL-10 genes may contribute to BCC susceptibility and influence the clinical course of BCC in polish population.

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

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

Topical treatment of basal cell carcinoma with the immune response modifier imiquimod

Imiquimod, a TLR7 agonist, is a novel immune response modifier currently widely used in the treatment of actinic keratoses (in situ squamous cell carcinoma). Imiquimod has revolutionized the treatment of field cancerization and has been approved for the treatment of superficial basal cell carcinoma with the recommendation of a 6-week treatment strategy, offering an alternative to surgery or other destructive treatment strategies.

Mitogen-activated protein kinases and Hedgehog-GLI signaling in cancer: A crosstalk providing therapeutic opportunities?

The Hedgehog-GLI (HH-GLI) signaling is of critical importance during embryonic development, where it regulates a number of cellular processes, including patterning, proliferation and differentiation. Its aberrant activation has been linked to several types of cancer. HH-GLI signaling is triggered by binding of ligands to the transmembrane receptor patched and is subsequently mediated by transcriptional effectors belonging to the GLI family, whose function is fine tuned by a series of molecular interactions and modifications. Several HH-GLI inhibitors have been developed and are in clinical trials. Similarly, the mitogen-activated protein kinases (MAPK) are involved in a number of biological processes and play an important role in many diseases including cancer. Inhibiting molecules targeting MAPK signaling, especially those elicited by the MEK1/2-ERK1/2 pathway, have been developed and are moving into clinical trials. ERK1/2 may be activated as a consequence of aberrant activation of upstream signaling molecules or during development of drug resistance following treatment with kinase inhibitors such as those for PI3K or BRAF. Evidence of a crosstalk between HH-GLI and other oncogenic signaling pathways has been reported in many tumor types, as shown by recent reviews. Here we will focus on the interaction between HH-GLI and the final MAPK effectors ERK1/2, p38 and JNK in cancer in view of its possible implications for cancer therapy. Several reports highlight the existence of a consistent crosstalk between HH signaling and MAPK, especially with the MEK1/2-ERK1/2 pathway, and this fact should be taken into consideration for designing optimal treatment and prevent tumor relapse.

ERBB3 is required for tumor promotion in a mouse model of skin carcinogenesis

The epidermal growth factor receptor (EGFR) plays a key role in skin inflammation, wound healing, and carcinogenesis. Less is known about the functions of the structurally related receptor ERBB3 (HER3) in the skin. We assessed the requirement of ERBB3 for skin homeostasis, wound healing, and tumorigenesis by crossing mice carrying a conditional Erbb3 allele with animals expressing cre under the control of the keratin 5 promoter. Erbb3(del) mice, lacking ERBB3 specifically in keratinocytes, showed no obvious abnormalities. The EGFR was upregulated in Erbb3(del) skin, possibly compensating the loss of ERBB3. Nonetheless, healing of full-thickness excisional wounds was negatively affected by ERBB3 deficiency. To analyze the function of ERBB3 during tumorigenesis, we employed the established DMBA/TPA multi-stage chemical carcinogenesis protocol. Erbb3(del) mice remained free of papillomas for a longer time and had significantly reduced tumor burden compared to control littermates. Tumor cell proliferation was considerably reduced in Erbb3(del) mice, and loss of ERBB3 also impaired keratinocyte proliferation after a single application of TPA. In human skin tumor samples, upregulated ERBB3 expression was observed in squamous cell carcinoma, condyloma, and malignant melanoma. Thus, we conclude that ERBB3, while dispensable for the development and the homeostasis of the epidermis and its appendages, is required for proper wound healing and for the progression of skin tumors during multi-stage chemical carcinogenesis in mice. ERBB3 may also be important for human skin cancer progression. The latter effects most probably reflect a key role for ERBB3 in increasing cell proliferation after stimuli as wounding or carcinogenesis.

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.

Intraflagellar transport 27 is essential for hedgehog signaling but dispensable for ciliogenesis during hair follicle morphogenesis

Hair follicle morphogenesis requires precisely controlled reciprocal communications, including hedgehog (Hh) signaling. Activation of the Hh signaling pathway relies on the primary cilium. Disrupting ciliogenesis results in hair follicle morphogenesis defects due to attenuated Hh signaling; however, the loss of cilia makes it impossible to determine whether hair follicle phenotypes in these cilia mutants are caused by the loss of cilia, disruption of Hh signaling, or a combination of these events. In this study, we characterized the function of Ift27, which encodes a subunit of intraflagellar transport (IFT) complex B. Hair follicle morphogenesis of Ift27-null mice was severely impaired, reminiscent of phenotypes observed in cilia and Hh mutants. Furthermore, the Hh signaling pathway was attenuated in Ift27 mutants, which was in association with abnormal ciliary trafficking of SMO and GLI2, and impaired processing of Gli transcription factors; however, formation of the ciliary axoneme was unaffected. The ciliary localization of IFT25 (HSPB11), the binding partner of IFT27, was disrupted in Ift27 mutant cells, and Ift25-null mice displayed hair follicle phenotypes similar to those of Ift27 mutants. These data suggest that Ift27 and Ift25 operate in a genetically and functionally dependent manner during hair follicle morphogenesis. This study suggests that the molecular trafficking machineries underlying ciliogenesis and Hh signaling can be segregated, thereby providing important insights into new avenues of inhibiting Hh signaling, which might be adopted in the development of targeted therapies for Hh-dependent cancers, such as basal cell carcinoma.

Cancer etiology. Variation in cancer risk among tissues can be explained by the number of stem cell divisions

Some tissue types give rise to human cancers millions of times more often than other tissue types. Although this has been recognized for more than a century, it has never been explained. Here, we show that the lifetime risk of cancers of many different types is strongly correlated (0.81) with the total number of divisions of the normal self-renewing cells maintaining that tissue's homeostasis. These results suggest that only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions. The majority is due to "bad luck," that is, random mutations arising during DNA replication in normal, noncancerous stem cells. This is important not only for understanding the disease but also for designing strategies to limit the mortality it causes.

Silibinin and its 2,3-dehydro-derivative inhibit basal cell carcinoma growth via suppression of mitogenic signaling and transcription factors activation

Basal cell carcinoma (BCC) is the most common cancer worldwide, and its current treatment options are insufficient and toxic. Surprisingly, unlike several other malignancies, chemopreventive efforts against BCC are almost lacking. Silibinin, a natural agent from milk thistle seeds, has shown strong efficacy against several cancers including ultraviolet radiation-induced skin (squamous) cancer; however, its potential activity against BCC is not yet examined. Herein, for the first time, we report the efficacy of silibinin and its oxidation product 2,3-dehydrosilibinin (DHS) against BCC both in vitro and in vivo using ASZ (p53 mutated) and BSZ (p53 deleted) cell lines derived from murine BCC tumors. Both silibinin and DHS significantly inhibited cell growth and clonogenicity while inducing apoptosis in a dose- and time-dependent manner, with DHS showing higher activity at lower concentrations. Both agents also inhibited the mitogenic signaling by reducing EGFR, ERK1/2, Akt, and STAT3 phosphorylation and suppressed the activation of transcription factors NF-κB and AP-1. More importantly, in an ectopic allograft model, oral administration of silibinin and DHS (200 mg/kg body weight) strongly inhibited the ASZ tumor growth by 44% and 71% (P < 0.05), respectively, and decreased the expression of proliferation biomarkers (PCNA and cyclin D1) as well as NF-κB p50 and c-Fos in the tumor tissues. Taken together, these results provide the first evidence for the efficacy and usefulness of silibinin and its derivative DHS against BCC, and suggest the need for additional studies with these agents in pre-clinical and clinical BCC chemoprevention and therapy models.

Immunohistochemical analysis of the mechanistic target of rapamycin and hypoxia signalling pathways in basal cell carcinoma and trichoepithelioma

BACKGROUND

Basal cell carcinoma (BCC) is the most common cancer in Caucasians. Trichoepithelioma (TE) is a benign neoplasm that strongly resembles BCC. Both are hair follicle (HF) tumours. HFs are hypoxic microenvironments, therefore we hypothesized that hypoxia-induced signalling pathways could be involved in BCC and TE as they are in other human malignancies. Hypoxia-inducible factor 1 (HIF1) and mechanistic/mammalian target of rapamycin (mTOR) are key players in these pathways.

OBJECTIVES

To determine whether HIF1/mTOR signalling is involved in BCC and TE.

METHODS

We used immunohistochemical staining of formalin-fixed paraffin-embedded BCC (n = 45) and TE (n = 35) samples to assess activity of HIF1, mTORC1 and their most important target genes. The percentage positive tumour cells was assessed manually in a semi-quantitative manner and categorized (0%, <30%, 30-80% and >80%).

RESULTS

Among 45 BCC and 35 TE examined, expression levels were respectively 81% and 57% (BNIP3), 73% and 75% (CAIX), 79% and 86% (GLUT1), 50% and 19% (HIF1α), 89% and 88% (pAKT), 55% and 61% (pS6), 15% and 25% (pMTOR), 44% and 63% (PHD2) and 44% and 49% (VEGF-A). CAIX, Glut1 and PHD2 expression levels were significantly higher in TE when only samples with at least 80% expression were included.

CONCLUSIONS

HIF and mTORC1 signalling seems active in both BCC and TE. There are no appreciable differences between the two with respect to pathway activity. At this moment immunohistochemical analyses of HIF, mTORC1 and their target genes does not provide a reliable diagnostic tool for the discrimination of BCC and TE.

Heterogeneity and plasticity of epidermal stem cells

The epidermis is an integral part of our largest organ, the skin, and protects us against the hostile environment. It is a highly dynamic tissue that, during normal steady-state conditions, undergoes constant turnover. Multiple stem cell populations residing in autonomously maintained compartments facilitate this task. In this Review, we discuss stem cell behaviour during normal tissue homeostasis, regeneration and disease within the pilosebaceous unit, an integral structure of the epidermis that is responsible for hair growth and lubrication of the epithelium. We provide an up-to-date view of the pilosebaceous unit, encompassing the heterogeneity and plasticity of multiple discrete stem cell populations that are strongly influenced by external cues to maintain their identity and function.

Molecular pathology of skin neoplasms of the head and neck

CONTEXT

Skin neoplasms include the most common malignancies affecting humans. Many show an ultraviolet (UV)-induced pathogenesis and often affect the head and neck region.

OBJECTIVE

To review literature on cutaneous neoplasms that show a predilection for the head and neck region and that are associated with molecular alterations.

DATA SOURCES

Literature review.

CONCLUSIONS

Common nonmelanoma skin cancers, such as basal and squamous cell carcinomas, show a UV-induced pathogenesis. Basal cell carcinomas are characterized by molecular alterations of the Hedgehog pathway, affecting patched and smoothened genes. While squamous cell carcinomas show UV-induced mutations in several genes, driver mutations are only beginning to be identified. In addition, certain adnexal neoplasms also predominantly affect the head and neck region and show interesting, recently discovered molecular abnormalities, or are associated with hereditary conditions whose molecular genetic pathogenesis is well understood. Furthermore, recent advances have led to an increased understanding of the molecular pathogenesis of melanoma. Certain melanoma subtypes, such as lentigo maligna melanoma and desmoplastic melanoma, which are more often seen on the chronically sun-damaged skin of the head and neck, show differences in their molecular signature when compared to the other more common subtypes, such as superficial spreading melanoma, which are more prone to occur at sites with acute intermittent sun damage. In summary, molecular alterations in cutaneous neoplasms of the head and neck are often related to UV exposure. Their molecular footprint often reflects the histologic tumor type, and familiarity with these changes will be increasingly necessary for diagnostic and therapeutic considerations.

Tazarotene induces apoptosis in human basal cell carcinoma via activation of caspase-8/t-Bid and the reactive oxygen species-dependent mitochondrial pathway

Previous studies suggest that tazarotene, a new member of the acetylenic class of RARβ/γ selective retinoids which is approved to treat a variety of skin diseases, exhibits an anti-proliferative effect in human basal cell carcinoma (BCC) by triggering caspase-dependent apoptosis. However, the detailed molecular mechanisms underlying the anti-tumor activity of tazarotene are poorly understood. This study aims at investigating the molecular mechanisms of tazarotene-induced apoptosis in human BCC cells. Our results are the first to demonstrate that tazarotene induces mitochondria-dependent cleavage of caspase-9 and -3 and PARP in BCC cells by producing reactive oxygen species (ROS) and activating caspase-8 through both ROS and death receptor signaling. These events are accompanied by a decrease in BCL-2 and BCL-xl anti-apoptotic proteins as well as by survivin and XIAP, two IAP family members. Furthermore, our results presented for the first time that tazarotene triggers a convergence of the intrinsic and extrinsic apoptotic pathways via the caspase-8-truncated Bid signaling pathway. Collectively, these data provide insights into the molecular mechanisms underlying tazarotene-induced apoptosis in human BCC cells, suggesting that this compound is a potential anti-skin cancer drug.

Melanotic and non-melanotic malignancies of the face and external ear - A review of current treatment concepts and future options

Skin has the highest incidence and variety of tumors of all organs. Its structure is of great complexity, and every component has the potential to originate a skin neoplasm (SN). Because of its exposed nature, skin is vulnerable to carcinogenic stimuli such as UV radiation. Various entities can cause SN. Nonmelanotic skin cancers (NMSC) are the most common of all cancers, with over one million cases diagnosed annually in the US. Basal cell carcinoma (BCC) accounts for approximately 80% of all NMSC, most of the remaining 20% being squamous cell carcinoma (SCC). The skin of the head and neck is the most common site for tumors, accounting for more than 80% of all NMSC. BCC, SCC, and malignant melanomas (MM) represent 85-90% of all SN. Merkel cell tumors (MCC), lymphoepithelioma-like carcinomas of the skin (LELCS), dermato-fibro-sarcomas, leiomyosarkomas, and Kaposi-sarcomas are less frequent in the facial skin region and the external ear. Based on data from the German Federal Cancer Registry (2003/2004), 140,000 people in Germany were affected by SN (100,000 BCC, 22,000 SCC, 22,000 MM). This number increases considerably if malignant precursors, such as actinic keratosis, are included. Each year, the frequency of SN diagnosis rises by 3-7%. Among all known malignant tumors, MM exhibits the highest rate of increase in incidence. In the past, SN was primarily diagnosed in people aged 50 years or older. However, recently, the risk for developing SN has shifted, and younger people are also affected. Early diagnosis is significantly correlated with prognosis. Resection of SN creates defects that must be closed with local or microvascular flaps to avoid functional disturbing scar formation and deflection of the nose, eyelids, or lips. All therapeutic strategies for SN, the current standard for adjuvant and systemic treatment, and the management of the increasing number of patients under permanent blood thinner medication are described with regard to the treatment of SN.

Basal cell carcinoma of the axilla: review of the world literature

Basal cell carcinoma (BCC) of the axilla is rare; indeed, 70 axillary BCCs have been described in 69 patients. Using the PubMed database, an extensive literature search was performed on BCC, axilla, and axillary. Relevant papers were reviewed and the characteristics of individuals with BCC of the axilla were summarized. The calculated prevalence of axillary BCC was 0.17%. They occurred predominantly in Caucasians. The majority of patients had no obvious BCC-associated risk factors. They were observed 1.2 times more often in men than in women and twice as often in the right axilla than the left axilla. They frequently presented as an asymptomatic nodule; however, associated features have included elongation of the tumor along the axillary skin lines, ulceration, and pigmentation. The axillary tumor was typically associated with either the superficial or the nodular histologic subtype of BCC. The prognosis for these patients was usually excellent following complete removal or destruction of the tumor. In conclusion, axillary BCC is a rare clinical variant of this type of skin cancer that usually presents as an asymptomatic nodule in an individual who does not have any traditional risk factors for this malignancy. The cancer was typically associated with a non-aggressive histologic subtype. Recurrence or metastasis was uncommon following treatment of the primary tumor.

Are microRNAs key players in epithelial skin cancers? A review focused on basal cell carcinoma and squamous cell carcinoma

The cancer of the skin is an increasing problem for public health worldwide. The fair skin populations that are environmentally or occupationally exposed to solar ultraviolet (UV)-radiation are the most affected. Intensive research investigating the molecular mechanisms of skin cancer is ongoing, however the role of noncoding RNAs in the pathology of cutaneous cell carcinoma is not fully understood. Accumulating evidence show that miRNAs play an important role in physiologic, pathologic and carcinogenic processes but their role in epithelial skin cancers (i.e. basal cell carcinoma and squamous cell carcinoma) was to date not sufficiently highlighted. MiRNAs are single-stranded small RNAs which specifically target mRNAs for translational repression and/or mRNA decay. In this review we focus on the latest findings in this area of research reviewing the newest research trends and perspectives.

Metatypical Basal cell carcinomas: a successful surgical approach to two cases with different tumor locations

We present 2 rare cases of metatypical basal cell carcinoma - two 72-year-old male patients with ulcerative lesions localized either to the left forehead or the back. The biopsy revealed a metatypical basal cell carcinoma. The treatment consisted of a wide local elliptical excision with good cosmetic results. There was no sign of recurrence or metastasis during a 12 months follow-up period.Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) make up 95% of the most common types of cancer in the world - the non-melanoma skin cancer (NMSC). BCC is known for its potential to be locally invasive while SCC for its potential to metastasize in lymph nodes. The meta-typical basal cell carcinoma (MTBC) is a rare type of tumor which combines the clinical and histopathological features of both BCC and SCC with a 5% risk for the development of metastases. The gold standard for diagnosis lies in the histopathological verification of the lesional tissue. Clinical examinations alone are not enough.

Update of cetuximab for non-melanoma skin cancer

INTRODUCTION

Non-melanoma skin cancer (NMSC) has become the most common malignancy in humans. Targeted therapies are recent developments for these tumors. Monoclonal antibody cetuximab has proven its efficacy and has improved tolerability compared to classical chemotherapy protocols, and this prompted us to analyze new data on the use of cetuximab in cutaneous NMSC.

AREAS COVERED

The monoclonal antibody cetuximab against epidermal growth factor receptor (EGFR) has been investigated for its use in NMSC during the years between 2011 and 2013. A PUBMED research 2011 - 2013 has been conducted using the following terms: 'Non-melanoma skin cancer AND cetuximab', 'cutaneous squamous cell carcinoma AND cetuximab', and 'basal cell carcinoma AND cetuximab' and 'cetuximab AND skin toxicity'. Available data were analyzed - irrespective of their level of evidence, that is, case reports and case series were included.

EXPERT OPINION

Current evidence of cetuximab's efficacy in NMSC was mainly obtained in cutaneous squamous cell carcinoma (SCC) and to a lesser extent in basal cell carcinoma (BCC). Response rates vary for neoadjuvant, adjuvant, monotherapy and combined therapy with cetuximab. Limitations are the low number of patients treated (33 patients with SCC, 4 patients with BCC) and the low quality of studies reported. Management of cutaneous toxicities of EGFR inhibitors is necessary, and guidelines are available. Proactive therapy might also prevent skin toxicity of higher grades, with EGFR inhibitor cetuximab as an option for recurrent or advanced NMSC of the skin. It seems to be justified particularly in very high risk epithelial tumors. There is an urgent need for Phase III trials. In the future, combined drug therapy with other monoclonal antibodies and/or radiotherapy may further improve efficacy and response rates for NMSC.

Reconstructing skin cancers using animal models

The American Cancer Society estimates that skin cancer is the most prevalent of all cancers with over 2 million cases of nonmelanoma skin cancer each year and 75,000 melanoma cases in 2012. Representative animal cancer models are important for understanding the underlying molecular pathogenesis of these cancers and the development of novel targeted anticancer therapeutics. In this review, we will discuss some of the important animal models that have been useful to identify important pathways involved in basal cell carcinoma, squamous cell carcinoma, and melanoma.

EGFR-ras-raf signaling in epidermal stem cells: roles in hair follicle development, regeneration, tissue remodeling and epidermal cancers

The mammalian skin is the largest organ of the body and its outermost layer, the epidermis, undergoes dynamic lifetime renewal through the activity of somatic stem cell populations. The EGFR-Ras-Raf pathway has a well-described role in skin development and tumor formation. While research mainly focuses on its role in cutaneous tumor initiation and maintenance, much less is known about Ras signaling in the epidermal stem cells, which are the main targets of skin carcinogenesis. In this review, we briefly discuss the properties of the epidermal stem cells and review the role of EGFR-Ras-Raf signaling in keratinocyte stem cells during homeostatic and pathological conditions.

Imiquimod directly inhibits Hedgehog signalling by stimulating adenosine receptor/protein kinase A-mediated GLI phosphorylation

Imiquimod (IMQ), a nucleoside analogue of the imidazoquinoline family, is used in the topical treatment of basal cell carcinoma (BCC) and other skin diseases. It is reported to be a TLR7 and TLR8 agonist and, as such, initiates a Th1 immune response by activating sentinel cells in the vicinity of the tumour. BCC is a hedgehog (HH)-driven malignancy with oncogenic glioma-associated oncogene (GLI) signalling activated in a ligand-independent manner. Here we show that IMQ can also directly repress HH signalling by negatively modulating GLI activity in BCC and medulloblastoma cells. Further, we provide evidence that the repressive effect of IMQ on HH signalling is not dependent on TLR/MYD88 signalling. Our results suggest a mechanism for IMQ engaging adenosine receptors (ADORAs) to control GLI signalling. Pharmacological activation of ADORA with either an ADORA agonist or IMQ resulted in a protein kinase A (PKA)-mediated GLI phosphorylation and reduction in GLI activator levels. The activation of PKA and HH pathway target gene downregulation in response to IMQ were abrogated by ADORA inhibition. Furthermore, activated Smoothened signalling, which positively signals to GLI transcription factors, could be effectively counteracted by IMQ. These results reveal a previously unknown mode of action of IMQ in the treatment of BCC and also suggest a role for ADORAs in the regulation of oncogenic HH signalling.

Advanced basal cell carcinoma of the skin: targeting the hedgehog pathway

PURPOSE OF REVIEW

This article provides an update on basal cell carcinoma (BCC), with a focus on the advanced BCC (aBCC), and the recent progress with targeted hedgehog signaling pathway inhibition for treatment of aBCC.

RECENT FINDINGS

The hedgehog signaling pathway is aberrantly activated in most BCC tumors providing an attractive therapeutic target in this cancer. Recently developed targeted hedgehog pathway inhibitors have demonstrated remarkable efficacy in the treatment of aBCC and the first oral hedgehog pathway inhibitor vismodegib was granted the US Food and Drug Administration (FDA) approval. Toxicities of the current hedgehog pathway inhibitors are mostly mild to moderate, but with prolonged treatment can pose a therapeutic challenge.

SUMMARY

Hedgehog pathway inhibition is a novel and powerful approach for treatment of aBCC. Current research efforts aim to enhance the activity and minimize toxicity of this promising new therapy.

Advanced basal cell carcinoma

Basal cell carcinoma (BCC) is the most common skin malignancy worldwide. Ultraviolet light exposure is the best known exogenous factor in BCC development. This is also the target for primary prevention. Advanced BCC include locally advanced tumors and metastatic tumors. Prognosis is worse compared to stage I and II BCCs. Mohs or micrographically controlled surgery is the gold standard of treatment. In patients with tumors that cannot be completely removed radiotherapy was the only alternative in the past. More recently new drugs for targeted therapy of signaling pathways like sonic hedgehog or epidermal growth factor receptor became available. More small molecules are under investigation. Since the complete response rates are limited, future research has to evaluate their combination with surgery.

Hedgehog signaling pathway and its targets for treatment in basal cell carcinoma

Basal cell carcinoma (BCC) of the skin is the most common type of cancer and accounts for up to 40% of all cancers in the US, with a growing incidence rate over recent decades in all developed countries. Surgery is curative for most patients, although it leaves unaesthetic scars, but those that develop locally advanced or metastatic BCC require different therapeutic approaches. Furthermore, patients with BCC present a high risk of developing additional tumors. The increasing economic burden and the morbidity of BCC render primary interest in the development of targeted treatments for this disease. Among the molecular signals involved in the development of BCC, the critical role of the morphogenetic Hedgehog (Hh) pathway has become evident. This pathway is found altered and activated in almost all BCCs, both sporadic and inherited. Given the centrality of the Hh pathway in the pathophysiology of BCC, the primary efforts to identify molecular targets for the topical or systemic treatment of this cancer have focused on the Hh components. Several Hh inhibitors have been so far identified - from the first identified natural cyclopamine to the recently Food and Drug Administration-approved synthetic vismodegib - most of which target the Hh receptor Smoothened (either its function or its translocation to the primary cilium). Other molecules await further characterization (bisamide compounds), while drugs currently approved for other diseases such as itraconazole (an antimicotic agent) and vitamin D3 have been tested on BCC with encouraging results. The outcomes of the numerous ongoing clinical trials are expected to expand the field in the very near future. Further research is needed to obtain drugs targeting downstream components of the Hh pathway (eg, Gli) or to exploit combinatorial therapies (eg, with phosphatidylinositol 3-kinase inhibitors or retinoids) in order to overcome potential drug resistance.

Distinct gene expression profiles of viral- and nonviral-associated merkel cell carcinoma revealed by transcriptome analysis

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine tumor with high mortality rates. Merkel cell polyomavirus (MCPyV), identified in the majority of MCC, may drive tumorigenesis via viral T antigens. However, mechanisms underlying pathogenesis in MCPyV-negative MCC remain poorly understood. To nominate genes contributing to pathogenesis of MCPyV-negative MCC, we performed DNA microarray analysis on 30 MCCs. MCPyV status of MCCs was determined by PCR for viral DNA and RNA. 1593 probe-sets were differentially expressed between MCPyV-negative and -positive MCC, with significant differential expression defined as at least 2-fold change in either direction and p-value of ≤ 0.05. MCPyV-negative tumors showed decreased RB1 expression, whereas MCPyV-positive tumors were enriched for immune response genes. Validation studies included immunohistochemistry demonstration of decreased RB protein expression in MCPyV-negative tumors and increased peritumoral CD8+ T lymphocytes surrounding MCPyV-positive tumors. In conclusion, our data suggest that loss of RB1 expression may play an important role in tumorigenesis of MCPyV-negative MCC. Functional and clinical validation studies are needed to determine whether this tumor suppressor pathway represents an avenue for targeted therapy.

Topical therapies for periorbital cutaneous malignancies: indications and treatment regimens

PURPOSE OF REVIEW

To present a brief review of periorbital cutaneous tumorogenesis, highlighting the steps which might be amenable to topical treatments and then discuss the use of topical agents in the management of periorbital skin malignancy.

RECENT FINDINGS

A rapid expansion in the understanding of the pathogenesis of melanoma and nonmelanoma skin cancer has allowed the development of a number of topical agents targeting specific tumor-forming processes. Topical agents have been shown to be effective in the management of periorbital skin malignancy.

SUMMARY

5-Fluorouracil and imiquimod have established roles in the management of periorbital skin malignancy. Newer agents such as ingenol mebutate, tazarotene, and diclofenac gel probably have evolving roles that require further research but show promise.

Extrinsic aging: UV-mediated skin carcinogenesis

Age-associated skin lesions linked to UV radiation (UVR) include actinic keratosis, non-melanoma skin cancer-such as basal cell carcinoma and squamous cell carcinoma-lentigo senilis and lentigo maligna. Their incidence is increasing worldwide, mainly due to exaggerated UV exposure and to an aging population. Early diagnosis and therapy of pre-malignant cutaneous lesions is crucial for the secondary prophylaxis of invasive and highly aggressive skin cancers. Combined efforts to increase public awareness, patient education about self-examination, prophylactic modalities, such as consistent and sufficient UV protection, and rigorous follow-up of high-risk groups are of highest importance.

Synergy of understanding dermatologic disease and epidermal biology

Dermatologic disease, although seldom life threatening, can be extremely disfiguring and interfere with the quality of life. In addition, as opposed to other organs, just the aging of skin and its adnexal structure the hair follicle can result in cosmetic concerns that affect most of us. The articles in this dermatology Review Series demonstrate recent progress in understanding the cell biology and molecular pathophysiology of the epidermis and hair follicles, which harbor keratinocyte and melanocyte stem cells. They reveal a dynamic relationship between research and clinical care: knowledge of dermatologic disease has facilitated the understanding of the biology of the epidermis and, in turn, progress in basic science has informed our understanding of disease. This type of synergy is a profound strength of clinical research of the type that the JCI is dedicated to publishing.