Gain of 11q/cyclin D1 overexpression is an essential early step in skin cancer development and causes abnormal tissue organization and differentiation

Homeostases of epidermis and hair follicle, and development of basal cell carcinoma

Hedgehog signaling (Hh) plays a critical role in embryogenesis. On the other hand, its overactivity may cause basal cell carcinoma (BCC), the most common human cancer. Further, epidermal and hair follicle homeostases may have a key role in the development of BCC. This article describes the importance of different signaling pathways in the different stages of the two processes. The description of the homeostases brought up the importance of the Notch signaling along with the sonic hedgehog (Shh) and the Wnt pathways. Loss of the Notch signaling adversely affects the late stages of hair follicle formation and allows the bulge cells in the hair follicles to take the fate of the keratinocytes in the interfollicular epidermis. Further, the loss of Notch activity upregulates the Shh and Wnt activities, adversely affecting the homeostases. Notably, the Notch signaling is suppressed in BCC, and the peripheral BCC cells, which have low Notch activity, show drug resistance in comparison to the interior suprabasal BCC cells, which have high Notch activity.

Computer Image Analysis Reveals C-Myc as a Potential Biomarker for Discriminating between Keratoacanthoma and Cutaneous Squamous Cell Carcinoma

The distinction between Keratoacanthoma (KA) and Cutaneous Squamous Cell Carcinoma (cSCC) is critical yet usually challenging to discriminate clinically and histopathologically. One approach to differentiate KA from cSCC is through assessing the immunohistochemical staining patterns of the three indicators, β-catenin, C-Myc, and CyclinD1, which are critical molecules that play important roles in the Wnt/β-catenin signaling pathway. Ki-67, as a proliferation biomarker for human tumor cells, was also assessed as an additional potential marker for differentiating KA from cSCC. In this report, these four indicators were analyzed in 42 KA and 30 cSCC cases with the use of the computer automated image analysis system. Computer automated image analysis is a time-based and cost-effective method of determining IHC staining in KA and cSCC samples. We found that C-Myc staining was predominantly localized in the nuclei of basal cells within KA patients, whereas cSCC staining was predominantly localized in the nuclei of diffuse cells. This C-Myc staining pattern has a sensitivity of 78.6% and a specificity of 66.7% for identifying KA. Moreover, positive rates of distinct expression patterns of C-Myc and Ki-67 may also serve as a means to clinically distinguish KA from cSCC. Taken together, our results suggest that these markers, in particular C-Myc, may be useful in differentiating KA from cSCC.

Regional Variation in Epidermal Susceptibility to UV-Induced Carcinogenesis Reflects Proliferative Activity of Epidermal Progenitors

To better understand the influence of ultraviolet (UV) irradiation on the initial steps of skin carcinogenesis, we examine patches of labeled keratinocytes as a proxy for clones in the interfollicular epidermis (IFE) and measure their size variation upon UVB irradiation. Multicolor lineage tracing reveals that in chronically irradiated skin, patches near hair follicles (HFs) increase in size, whereas those far from follicles do not change. This is explained by proliferation of basal epidermal cells within 60 μm of HF openings. Upon interruption of UVB, patch size near HFs regresses significantly. These anatomical differences in proliferative behavior have significant consequences for the cell of origin of basal cell carcinomas (BCCs). Indeed, a UV-inducible murine BCC model shows that BCC patches are more frequent, larger, and more invasive near HFs. These findings have major implications for the prevention of field cancerization in the epidermis.

Organotypic Co-Cultures as a Novel 3D Model for Head and Neck Squamous Cell Carcinoma

Background: Head and neck squamous cell carcinomas (HNSCC) are phenotypically and molecularly heterogeneous and frequently develop therapy resistance. Reliable patient-derived 3D tumor models are urgently needed to further study the complex pathogenesis of these tumors and to overcome treatment failure. Methods: We developed a three-dimensional organotypic co-culture (3D-OTC) model for HNSCC that maintains the architecture and cell composition of the individual tumor. A dermal equivalent (DE), composed of healthy human-derived fibroblasts and viscose fibers, served as a scaffold for the patient sample. DEs were co-cultivated with 13 vital HNSCC explants (non-human papillomavirus (HPV) driven, n = 7; HPV-driven, n = 6). Fractionated irradiation was applied to 5 samples (non-HPV-driven, n = 2; HPV-driven n = 3). To evaluate expression of ki-67, cleaved caspase-3, pan-cytokeratin, p16^INK4a, CD45, ∝smooth muscle actin and vimentin over time, immunohistochemistry and immunofluorescence staining were performed Patient checkup data were collected for up to 32 months after first diagnosis. Results: All non-HPV-driven 3D-OTCs encompassed proliferative cancer cells during cultivation for up to 21 days. Proliferation indices of primaries and 3D-OTCs were comparable and consistent over time. Overall, tumor explants displayed heterogeneous growth patterns (i.e., invasive, expansive, silent). Cancer-associated fibroblasts and leukocytes could be detected for up to 21 days. HPV DNA was detectable in both primary and 3D-OTCs (day 14) of HPV-driven tumors. However, p16^INK4a expression levels were varying. Morphological alterations and radioresistant tumor cells were detected in 3D-OTC after fractionated irradiation in HPV-driven and non-driven samples. Conclusions: Our 3D-OTC model for HNSCC supports cancer cell survival and proliferation in their original microenvironment. The model enables investigation of invasive cancer growth and might, in the future, serve as a platform to perform sensitivity testing upon treatment to predict therapy response.

T-lymphocyte profiles differ between keratoacanthomas and invasive squamous cell carcinomas of the human skin

BACKGROUND

T-lymphocytes are involved in tumor progression and regression. Actinic keratoses (AK) are atypical proliferations of keratinocytes of the skin. Some AK progress into invasive cutaneous squamous cell carcinomas (cSCC). Keratoacanthomas (KA) are either classified as a cSCC subtype or a benign tumor with histologic resemblance to well-differentiated cSCC as it is supposed to regress spontaneously. In contrast, cSCC represent malignant tumors that may metastasize.

OBJECTIVES

To compare the T-lymphocyte profiles of AK, KA and cSCC in relation to PD-L1 expression.

METHODS

Tissue micro-arrays of 103 cases of AK, 43 cases of KA and 106 cases of cSCC were stained by immunohistochemistry for E-cadherin, CD3, CD4, CD8, FOXp3, and the receptor-ligand pair PD-1/PD-L1. Immunohistological scores were computationally determined to assess PD-L1 expression as well as the expression profiles of T-lymphocytes.

RESULTS

AK had lower numbers of CD3+ and PD-1+ cells compared to KA and lower numbers of CD3+, CD8+ and PD-1+ cells in comparison with cSCC. KA showed significantly higher numbers of CD4+ and FOXp3+ cells as well as lower numbers of CD8+ cells in comparison with invasive cSCC. cSCC expressed significantly more PD-L1 in comparison with AK and KA. Among cSCC PD-L1 expression was higher in moderately and poorly-differentiated cSCC than in well-differentiated cSCC. Increased PD-L1 expression also correlated with increased numbers of CD4+, CD8+ and FOXp3+ cells in cSCC.

CONCLUSIONS

Tumor-associated T-lymphocyte infiltrates showed significant differences between AK, KA and invasive cSCC. PD-L1 expression correlated with invasion of T-cell infiltrates in invasive cSCC.

Epidermal Differentiation Complex: A Review on Its Epigenetic Regulation and Potential Drug Targets

The primary feature of the mammalian skin includes the hair follicle, inter-follicular epidermis and the sebaceous glands, all of which form pilo-sebaceous units. The epidermal protective layer undergoes an ordered/programmed process of proliferation and differentiation, ultimately culminating in the formation of a cornified envelope consisting of enucleated corneocytes. These terminally differentiated cells slough off in a cyclic manner and this process is regulated via induction or repression of epidermal differentiation complex (EDC) genes. These genes, spanning 2 Mb region of human chromosome 1q21, play a crucial role in epidermal development, through various mechanisms. Each of these mechanisms employs a unique chromatin re-modelling factor or an epigenetic modifier. These factors act to regulate epidermal differentiation singly and/or in combination. Diseases like psoriasis and cancer exhibit aberrations in proliferation and differentiation through, in part, dysregulation in these epigenetic mechanisms. Knowledge of the existing mechanisms in the physiological and the aforesaid pathological contexts may not only facilitate drug development, it also can make refinements to the existing drug delivery systems.

Isorhapontigenin suppresses growth of patient-derived glioblastoma spheres through regulating miR-145/SOX2/cyclin D1 axis

BACKGROUND

Glioblastoma (GBM) is the most common malignant brain tumor, and glioma stem cells (GSCs) are considered a major source of treatment resistance for glioblastoma. Identifying new compounds that inhibit the growth of GSCs and understanding their underlying molecular mechanisms are therefore important for developing novel therapy for GBM.

METHODS

We investigated the potential inhibitory effect of isorhapontigenin (ISO), an anticancer compound identified in our recent investigations, on anchorage-independent growth of patient-derived glioblastoma spheres (PDGS) and its mechanism of action.

RESULTS

ISO treatment resulted in significant anchorage-independent growth inhibition, accompanied with cell cycle G0-G1 arrest and cyclin D1 protein downregulation in PDGS. Further studies established that cyclin D1 was downregulated by ISO at transcription levels in a SOX2-dependent manner. In addition, ISO attenuated SOX2 expression by specific induction of miR-145, which in turn suppressed 3'UTR activity of SOX2 mRNA without affecting its mRNA stability. Moreover, ectopic expression of exogenous SOX2 rendered D456 cells resistant to induction of cell cycle G0-G1 arrest and anchorage-independent growth inhibition upon ISO treatment, whereas inhibition of miR-145 resulted in D456 cells resistant to ISO inhibition of SOX2 and cyclin D1 expression. In addition, overexpression of miR-145 mimicked ISO treatment in D456 cells.

CONCLUSIONS

ISO induces miR-145 expression, which binds to the SOX2 mRNA 3'UTR region and inhibits SOX2 protein translation. Inhibition of SOX2 leads to cyclin D1 downregulation and PDGS anchorage-independent growth inhibition. The elucidation of the miR-145/SOX2/cyclin D1 axis in PDGS provides a significant insight into understanding the anti-GBM effect of ISO compound.

Expression of G1/S-cyclins and cyclin-dependent kinase inhibitors in actinic keratosis and squamous cell carcinoma

BACKGROUND

Actinic keratosis (AK) and Bowen's disease (squamous cell carcinoma in situ, SCCIS) are pre-invasive stages in the development of squamous cell carcinoma (SCC).

METHODS

Immunohistochemical study of cyclin D1, cyclin E, p16(INK4a) and p21(Cip1) (/Waf1) in AK (53 cases), SCCIS (16 cases) and SCC (40 cases), in relation to the type of the lesion and SCC prognostic parameters (grade, diameter and thickness).

RESULTS

Diffuse cyclin D1 distribution was more frequent in SCCIS and SCC than in AK (p = 0.03) and similar pattern was observed for p16(INK4a) . For cyclin E, central distribution dominated in SCC compared with the AK (p = 0.001) and SCCIS (p = 0.03). p21(Cip1) (/Waf1) displayed suprabasal distribution more frequently in AK than in SCCIS (p = 0.001) and SCC (p = 0.0004). Semiquantitative assessment showed more positive cells in AK (p = 0.04) and SCCIS (p = 0.04) than in SCC for cyclin E. SCC with diameter over 20 mm and those thicker than 6 mm revealed higher labeling index with p16(INK4a) and p21(Cip1) (/Waf1) , respectively.

CONCLUSIONS

Our results suggest different alterations for p16(INK4a) and p21(Cip1) (/Waf1) in AK, SCCIS and SCC. Immunostaining distribution showed closer correlation with the type of the lesion, whereas percentage of positive cells displayed better association with the SCC prognostic parameters.

Combined cutaneous tumors with a melanoma component: A clinical, histologic, and molecular study

BACKGROUND

The histogenesis and clinical behavior of combined cutaneous tumors (CCTs) in which the mesenchymal component consists of melanoma remain unclear.

OBJECTIVE

We sought to characterize the clinical, histologic, and molecular findings in CCTs with an epithelial and a melanoma component.

METHODS

We retrospectively reviewed the records from 2 institutions for CCTs. Fluorescence in situ hybridization was performed to assess chromosomal copy number alterations in both components.

RESULTS

Sixteen CCTs were included. The most common subtype was the squamomelanocytic tumor (11), followed by the basomelanocytic tumor (3) and the trichoblastomelanoma (2). CCTs were more common in men (87%), on the head and neck (57%), and had extensive solar elastosis (81%). The median follow-up was 25 months (range, 8-167 months). One case had an adverse outcome. Fluorescence in situ hybridization revealed chromosomal alterations in approximately 55% of the cases. Five cases showed chromosomal gains only in the melanocytic component. One case showed 11q13 gains in both the epithelial and melanocytic components.

LIMITATIONS

Our study is retrospective and the sample is small.

CONCLUSIONS

The low incidence of adverse outcomes suggests that CCT may be more indolent than noncombined tumors. 11q13 amplification in both components supports the theory of dual differentiation from a common progenitor cell.

Squamous Cell Carcinoma - Similarities and Differences among Anatomical Sites

Squamous cell carcinoma (SCC) is an epithelial malignancy involving many anatomical sites and is the most common cancer capable of metastatic spread. Development of early diagnosis methods and novel therapeutics are important for prevention and mortality reduction. In this effort, numerous molecular alterations have been described in SCCs. SCCs share many phenotypic and molecular characteristics, but they have not been extensively compared. This article reviews SCC as a disease, including: epidemiology, pathology, risk factors, molecular characteristics, prognostic markers, targeted therapy, and a new approach to studying SCCs. Through this comparison, several themes are apparent. For example, HPV infection is a common risk factor among the four major SCCs (NMSC, HNSC, ESCC, and NSCLC) and molecular abnormalities in cell-cycle regulation and signal transduction predominate. These data reveal that the molecular insights, new markers, and drug targets discovered in individual SCCs may shed light on this type of cancer as a whole.

Cyclin d1 downregulation contributes to anticancer effect of isorhapontigenin on human bladder cancer cells

Isorhapontigenin (ISO) is a new derivative of stilbene compound that was isolated from the Chinese herb Gnetum Cleistostachyum and has been used for treatment of bladder cancers for centuries. In our current studies, we have explored the potential inhibitory effect and molecular mechanisms underlying isorhapontigenin anticancer effects on anchorage-independent growth of human bladder cancer cell lines. We found that isorhapontigenin showed a significant inhibitory effect on human bladder cancer cell growth and was accompanied with related cell cycle G(0)-G(1) arrest as well as downregulation of cyclin D1 expression at the transcriptional level in UMUC3 and RT112 cells. Further studies identified that isorhapontigenin downregulated cyclin D1 gene transcription via inhibition of specific protein 1 (SP1) transactivation. Moreover, ectopic expression of GFP-cyclin D1 rendered UMUC3 cells resistant to induction of cell-cycle G(0)-G(1) arrest and inhibition of cancer cell anchorage-independent growth by isorhapontigenin treatment. Together, our studies show that isorhapontigenin is an active compound that mediates Gnetum Cleistostachyum's induction of cell-cycle G(0)-G(1) arrest and inhibition of cancer cell anchorage-independent growth through downregulating SP1/cyclin D1 axis in bladder cancer cells. Our studies provide a novel insight into understanding the anticancer activity of the Chinese herb Gnetum Cleistostachyum and its isolate isorhapontigenin.

Cutaneous squamous cell carcinoma: defining the high-risk variant

With a lifetime incidence of approximately 10% in the general population, cutaneous squamous cell carcinoma (CSCC) is the second most common type of nonmelanoma skin cancer. Most CSCCs are benign and can be completely eradicated by surgery or other dermatological procedures. There is, however, a subgroup associated with an increased likelihood of lymph node metastases and, therefore, with high morbidity and mortality. This article analyzes the various factors that define aggressive CSCC. We propose a method for defining high-risk SCC on the basis of a series of major and minor criteria. This method will allow better prognostic evaluation and enable personalized management of patients with high-risk SCC, possibly leading to improved overall survival.

Peripheral T-cell Lymphoma with Cyclin D1 overexpression: a case report

Peripheral T-cell lymphomas not otherwise specified are generally considered aggressive non-Hodgkin lymphomas, because of poor natural outcome and response to therapy. They show a complex karyotype without any specific genetic hallmark. We report a case of peripheral T-cell lymphoma not otherwise specified with heterogeneous nuclear Cyclin D1 immunohistochemical overexpression, due to gene copy gain, a phenomenon similar to that observed in Mantle Cell Lymphoma characterized by t(11;14)(q13;q32). In this case report we underline the diagnostic pitfall rapresented by Cyclin D1 immunoistochemical overexpression in a T-cell lymphoma. Several pitfalls could lead to misinterpretation of diagnosis, therefore, we underlined the need to integrate the classical histology and immunohistochemistry with molecular tests as clonality or Fluorescence in situ hybridization.

Association of bromodomain BET proteins with chromatin requires dimerization through the conserved motif B

BET (bromodomain and extra terminal domain) family proteins are unique among bromodomain-containing proteins in that they not only associate with acetylated chromatin in interphase, but also remain attached to chromosomes during mitosis. Although the two tandem bromodomains are essential to display this behaviour, they do not suffice. In this work we report that a small conserved domain, motif B, is also required. A deletion mutant of this domain dissociates from mitotic chromosomes. However, inhibition of histone deacetylases alleviates dissociation. We also show that motif-B-dependent association with chromosomes is not restricted to mitosis. Interestingly, our results indicate that motif B constitutes a surface for homo- and hetero-dimerization between BET proteins. Finally, linked to the prominent role BET proteins play in cell proliferation, we report that ectopic expression of the family member Brd2 interferes with neuronal differentiation in P19 cells and in the vertebrate neural tube, probably because of preservation of adequate levels of cyclin A2 and cyclin D1. By contrast, a deletion mutant of motif B fails to perform in this way, highlighting the relevance of this domain for Brd2 function.

Stem cells of the human epidermis and their niche: composition and function in epidermal regeneration and carcinogenesis

Skin, as the largest organ, has long been subject of excellent and pioneering studies on stem cells and their role in tissue regulation and tumor formation. In particular, intensive research on mouse skin, and here especially the hair follicle, has largely extended our knowledge. Surprisingly, human skin, although the most easily accessible tissue in man, is far less conceived with regard to its stem cells and their specific environment (the niche). In consequence, these features are as yet only insufficiently defined and it still has to be elucidated how insights in cutaneous stem cell biology gained in mice can be extrapolated to humans. In the last few years, human model systems such as humanized mice or in vitro organotypic cultures that support maintenance or reconstruction of human skin and long-term epidermal regeneration have been developed. These models allow lineage tracing experiments and can be modified by adopting genetically manipulated cell types. Accordingly, they represent proper tools for human stem cell research and will clearly help to improve our still incomplete understanding. Like normal skin, the non-melanoma skin cancers and their respective tumors have gained considerable interest in basic as well as in clinical research. Being the most frequent human tumors globally, basal cell carcinomas and cutaneous squamous cell carcinomas (SCCs) continue to increase in incidence and specifically SCCs predominate in immunosuppressed transplant recipients. This review intends to compile the present knowledge on keratinocyte stem cells and their niches in normal skin and skin carcinomas with a special focus on the human situation. In particular, the role of the microenvironment, the niche, is emphasized, promoting our view of the decisive importance of the niche as a key regulatory element for controlling position, fate and regenerative potential of the stem cell population both in healthy skin and in carcinomas.

Nuclear translocation of β-catenin synchronized with loss of E-cadherin in oral epithelial dysplasia with a characteristic two-phase appearance

AIMS

One of the important histopathological characteristics of oral epithelial dysplasia is a two-phase appearance of rete processes, comprising an upper layer of keratinized cells and a lower layer of basaloid cells, and thereby creating a sharp contrast between these two separate cell populations. The aim of this study was to determine the cellular adhesion status of the basaloid cells.

METHODS AND RESULTS

Immunohistochemistry for β-catenin, E-cadherin and their related molecules was carried out in surgical specimens of two-phase epithelial dysplasia of the oral mucosa. The lower-half basaloid cells and the upper keratinized cells were microdissected separately, and extracted DNA samples were subjected to methylation-specific polymerase chain reaction amplification for E-cadherin. β-Catenin was immunolocalized within the nuclei and cytoplasm of Ki67-positive lower-half basaloid cells, as well as on the cell membrane of upper parakeratotic cells. The basaloid cells of the lower-half were also positive for matrix metalloproteinase-7 and cyclin D1, β-catenin target gene products, α-dystroglycan, tenascin-C, and perlecan, but not for E-cadherin. The promoter region of the E-cadherin gene was hypermethylated.

CONCLUSIONS

The solid proliferation of lower-half E-cadherin-free basaloid cells is enhanced by Wnt signalling cascades, as well as by the intraepithelial extracellular matrix or its bound growth factors.

Cyclin D1 and cyclin D-dependent kinases enhance oral keratinocyte proliferation but do not block keratinocyte differentiation

Maintenance of oral epithelial homeostasis requires a fine balance between cell proliferation and differentiation. However, the molecular mechanisms that couple these processes, and its deregulation in tumorigenesis are not fully understood. Cyclin D1 and its kinase partners CDK4 and CDK6 play an important role in regulating the G1-S phase of the cell cycle. Deregulation of cyclin D1 is a frequent event in oral squamous cell carcinoma. Here, we examined whether overexpression of cyclin D1, CDK4 and CDK6 can deregulate the link between oral keratinocyte proliferation and differentiation. Our results show that cyclin D1 and its kinase partners CDK4 and CDK6 enhance keratinocyte proliferation, but are not sufficient to block calcium-induced keratinocyte differentiation and suggest that deregulation of these G1-regulatory kinases alone is insufficient to uncouple the link between proliferation and differentiation.

A decisive function of transforming growth factor-β/Smad signaling in tissue morphogenesis and differentiation of human HaCaT keratinocytes

By interfering with the TGFβ/Smad pathway in the human HaCaT keratinocytes, this study provides novel insights into the role of Smad signaling for regular tissue homeostasis and demonstrates its crucial role in terminal epidermal differentiation and in the decision between alternative epithelial differentiation programs.

 The mechanism by which transforming growth factor-β (TGFβ) regulates differentiation in human epidermal keratinocytes is still poorly understood. To assess the role of Smad signaling, we engineered human HaCaT keratinocytes either expressing small interfering RNA against Smads2, 3, and 4 or overexpressing Smad7 and verified impaired Smad signaling as decreased Smad phosphorylation, aberrant nuclear translocation, and altered target gene expression. Besides abrogation of TGFβ-dependent growth inhibition in conventional cultures, epidermal morphogenesis and differentiation in organotypic cultures were disturbed, resulting in altered tissue homeostasis with suprabasal proliferation and hyperplasia upon TGFβ treatment. Neutralizing antibodies against TGFβ, similar to blocking the actions of EGF-receptor or keratinocyte growth factor, caused significant growth reduction of Smad7-overexpressing cells, thereby demonstrating that epithelial hyperplasia was attributed to TGFβ-induced “dermis”-derived growth promoting factors. Furthermore impaired Smad signaling not only blocked the epidermal differentiation process or caused epidermal-to-mesenchymal transition but induced a switch to a complex alternative differentiation program, best characterized as mucous/intestinal-type epithelial differentiation. As the same alternative phenotype evolved from both modes of Smad-pathway interference, and reduction of Smad7-overexpression caused reversion to epidermal differentiation, our data suggest that functional TGFβ/Smad signaling, besides regulating epidermal tissue homeostasis, is not only essential for terminal epidermal differentiation but crucial in programming different epithelial differentiation routes.

BAG-1 enhances cell-cell adhesion, reduces proliferation and induces chaperone-independent suppression of hepatocyte growth factor-induced epidermal keratinocyte migration

Cell motility is important in maintaining tissue homeostasis, facilitating epithelial wound repair and in tumour formation and progression. The aim of this study was to determine whether BAG-1 isoforms regulate epidermal cell migration in in vitro models of wound healing. In the human epidermal cell line HaCaT, endogenous BAG-1 is primarily nuclear and increases with confluence. Both transient and stable p36-Bag-1 overexpression resulted in increased cellular cohesion. Stable transfection of either of the three human BAG-1 isoforms p36-Bag-1 (BAG-1S), p46-Bag-1 (BAG-1M) and p50-Bag-1 (BAG-1L) inhibited growth and wound closure in serum-containing medium. However, in response to hepatocyte growth factor (HGF) in serum-free medium, BAG-1S/M reduced communal motility and colony scattering, but BAG-1L did not. In the presence of HGF, p36-Bag-1 transfectants retained proliferative response to HGF with no change in ERK1/2 activation. However, the cells retained E-cadherin localisation at cell-cell junctions and exhibited pronounced cortical actin. Point mutations in the BAG domain showed that BAG-1 inhibition of motility is independent of its function as a chaperone regulator. These findings are the first to suggest that BAG-1 plays a role in regulating cell-cell adhesion and suggest an important function in epidermal cohesion.

PI3K/Akt/JNK/c-Jun signaling pathway is a mediator for arsenite-induced cyclin D1 expression and cell growth in human bronchial epithelial cells

Arsenite exposure is associated with an increased risk of human lung cancer. However, the molecular mechanisms underlying the arsenite-induced human lung carcinogenesis remain elusive. In this study, we demonstrated that arsenite upregulates cyclin D1 expression/activity to promote the growth of human bronchial epithelial Beas-2B cells. In this process, the JNKs (c-Jun N-terminal kinases)/c-Jun cascade is elicited. The inhibition of JNKs or c-Jun by chemical or genetic inhibitors blocks the cyclin D1 induction mediated by arsenite. Furthermore, using a loss of function mutant of p85 (Deltap85, a subunit of PI3K) or dominant-negative Akt (DN-Akt), we showed that PI3K and Akt act as the upstream regulators of JNKs and c-Jun in arsenite-mediated growth promotion. Overall, our data suggest a pathway of PI-3K/Akt/JNK/c-Jun/cylin D1 signaling in response to arsenite in human bronchial epithelial cells.

Copy number gain and oncogenic activity of YWHAZ/14-3-3zeta in head and neck squamous cell carcinoma

Gene amplification, a common mechanism for oncogene activation in cancers, has been used in the discovery of novel oncogenes. Low-level copy number gains are frequently observed in head and neck squamous cell carcinomas (HNSCCs) where numerous amplification events and potential oncogenes have already been reported. Recently, we applied restriction landmark genome scanning to study gene amplifications in HNSCC and located novel and uncharacterized regions in primary tumor samples. Gain on chromosome 8q22.3, the location of YWHAZ (14-3-3zeta), is found in 30-40% HNSCC cases. Data obtained from fluorescence in situ hybridization and immunohistochemistry on HNSCC tissue microarrays confirmed frequent low-level YWHAZ copy number gain and protein overexpression. YWHAZ mRNA was frequently upregulated in patients' tumor tissues. Furthermore, YWHAZ RNAi significantly suppressed the growth rate of HNSCC cell lines, and overexpression of YWHAZ in HaCaT immortalized human skin keratinocytes promotes overgrowth, as well as morphological changes. Reduced YWHAZ levels increased the G1/G0-phase proportion, decreased the S-phase proportion and the rate of DNA synthesis. Based on this evidence, we suggest that YWHAZ is a candidate proto-oncogene and deserves further investigation into its role in HNSCC carcinogenesis.

Cyclin D1 downregulation is important for permanent cell cycle exit and initiation of differentiation induced by anchorage-deprivation in human keratinocytes

To understand the relationship between permanent cell cycle exit and differentiation the immortalized keratinocyte cell line, SIK and the squamous cell carcinoma, SCC9 were compared during differentiation induced by anchorage-deprivation. The SIK cells when placed in suspension culture promptly lost almost all ability to reinitiate growth by 2 days concomitantly expressing the differentiation specific proteins, transglutaminase (TGK) and involucrin. These cells rapidly underwent G1 cell cycle arrest with complete disappearance of phosphorylated RB. In contrast SCC9 cells neither showed TGK expression nor increase in involucrin. They decreased their colony-forming ability much more slowly, which coordinated well with a gradual decrease in phosphorylated RB, demonstrating the significant resistance to loss of colony-forming ability and cell cycle exit. In accordance, cyclin D1, a positive regulator of cyclin-dependent kinase (CDK) 4/6 which phosphorylates RB decreased drastically in anchorage deprived SIK but not in SCC9 cells. Endogenous cyclin D1 knockdown in SCC9 cells by siRNA enhanced loss of the colony-forming ability during anchorage-deprivation. Conversely enforced expression of cyclin D1 in SIK cells and in another immortalized keratinocyte cell line, HaCaT, partly prevented loss of their colony-forming abilities. Cyclin D1 overexpression antagonized Keratin 10 expression in suspended HaCaT cells. The result demonstrates the importance of cyclin D1 down regulation for proper initiation of keratinocyte differentiation.

Prognostic criteria for squamous cell cancer of the skin

BACKGROUND

Non-well-differentiated cutaneous squamous cell carcinomas may display a more aggressive behavior. It is important to better define prognostic criteria for these tumors.

METHODS

This was a retrospective case-control analysis of a squamous cell carcinoma database. Patients with non-well-differentiated and well-differentiated tumors were matched based on site of tumor, age, and immunocompromised status. Comparisons included demographics, histology, immunohistochemical protein expressions (Ki-67, p53, E-cadherin, cyclin D1), and clinical outcomes.

RESULTS

Demographic features were similar between cases (n=30) and controls (n=30). Non-well-differentiated tumors were larger (1.8 cm versus 1.3 cm, P=0.08), deeper (0.81 cm versus 0.32 cm, P<0.0001), and had greater recurrence (P=0.003). Non-well-differentiated tumors showed increased proliferation rate, Ki-67 index (77% versus 61%, P=0.001); no significant difference in activity of p53, E-cadherin, and cyclin D1 between the two groups.

CONCLUSIONS

Tumor differentiation and depth are important pathologic and prognostic criteria for cutaneous squamous cell carcinoma. Immunohistochemistry helps describe patterns of biomarker protein expression and may exemplify aggressive subtypes.

Stromal control of oncogenic traits expressed in response to the overexpression of GLI2, a pleiotropic oncogene

Hedgehog signaling is often activated in tumors, yet it remains unclear how GLI2, a transcription factor activated by this pathway, acts as an oncogene. We show that GLI2 is a pleiotropic oncogene. Overexpression induces genomic instability and blocks differentiation, likely mediated in part by enhanced expression of the stem cell gene SOX2. GLI2 also induces TGFβ dependent transdifferentiation of foreskin and tongue, but not gingival fibroblasts into myofibroblasts, creating an environment permissive for invasion by keratinocytes, which are in various stages of differentiation having down regulated GLI2. Thus, up-regulated GLI2 expression is sufficient to induce a number of the acquired characteristics of tumor cells; however the stroma, in a tissue specific manner, determines whether certain GLI2 oncogenic traits are expressed.

Fos cooperation with PTEN loss elicits keratoacanthoma not carcinoma, owing to p53/p21WAF-induced differentiation triggered by GSK3β inactivation and reduced AKT activity

To investigate gene synergism in multistage skin carcinogenesis, the RU486-inducible cre/lox system was employed to ablate Pten function (K14.cre/Δ5Ptenflx) in mouse epidermis expressing activated Fos (HK1.Fos). RU486-treated HK1.Fos/Δ5Ptenflx mice exhibited hyperplasia, hyperkeratosis and tumours that progressed to highly differentiated keratoacanthomas, rather than to carcinomas, owing to re-expression of high p53 and p21WAF levels. Despite elevated MAP kinase activity, cyclin D1 and cyclin E2 overexpression, and increased AKT activity that produced areas of highly proliferative papillomatous keratinocytes, increasing levels of GSK3β inactivation induced a novel p53/p21WAF expression profile, which subsequently halted proliferation and accelerated differentiation to give the hallmark keratosis of keratoacanthomas. A pivotal facet to this GSK3β-triggered mechanism centred on increasing p53 expression in basal layer keratinocytes. This increase in expression reduced activated AKT expression and released inhibition of p21WAF, which accelerated keratinocyte differentiation, as indicated by unique basal layer expression of differentiation-specific keratin K1 alongside premature filaggrin and loricrin expression. Thus, Fos synergism with Pten loss elicited a benign tumour context where GSK3β-induced p53/p21WAF expression continually switched AKT-associated proliferation into differentiation, preventing further progression. This putative compensatory mechanism required the critical availability of normal p53 and/or p21WAF, otherwise deregulated Fos, Akt and Gsk3β associate with malignant progression.

UVA radiation causes DNA strand breaks, chromosomal aberrations and tumorigenic transformation in HaCaT skin keratinocytes

The role of UVA-radiation-the major fraction in sunlight-in human skin carcinogenesis is still elusive. We here report that different UVA exposure regime (4 x 5 J/cm(2) per week or 1 x 20 J/cm(2) per week) caused tumorigenic conversion (tumors in nude mice) of the HaCaT skin keratinocytes. While tumorigenicity was not associated with general telomere shortening, we found new chromosomal changes characteristic for each recultivated tumor. Since this suggested a nontelomere-dependent relationship between UVA irradiation and chromosomal aberrations, we investigated for alternate mechanisms of UVA-dependent genomic instability. Using the alkaline and neutral comet assay as well as gamma-H2AX foci formation on irradiated HaCaT cells (20-60 J/cm(2)), we show a dose-dependent and long lasting induction of DNA single and double (ds) strand breaks. Extending this to normal human skin keratinocytes, we demonstrate a comparable damage response and, additionally, a significant induction and maintenance of micronuclei (MN) with more acentric fragments (indicative of ds breaks) than entire chromosomes particularly 5 days post irradiation. Thus, physiologically relevant UVA doses cause long-lasting DNA strand breaks, a prerequisite for chromosomal aberration that most likely contribute to tumorigenic conversion of the HaCaT cells. Since normal keratinocytes responded similarly, UVA may likewise contribute to the complex karyotype characteristic for human skin carcinomas.

Cortactin expression predicts poor survival in laryngeal carcinoma

Amplification of the 11q13 region is one of the most frequent aberrations in squamous cell carcinomas of the head and neck region (HNSCC). Amplification of 11q13 has been shown to correlate with the presence of lymph node metastases and decreased survival. The 11q13.3 amplicon carries numerous genes including cyclin D1 and cortactin. Recently, we reported that FADD becomes overexpressed upon amplification and that FADD protein expression predicts for lymph node positivity and disease-specific mortality. However, the gene within the 11q13.3 amplicon responsible for this correlation is yet to be identified. In this paper, we compared, using immunohistochemical analysis for cyclin D1, FADD and cortactin in a series of 106 laryngeal carcinomas which gene correlates best with lymph node metastases and increased disease-specific mortality. Univariate Cox regression analysis revealed that high expression of cyclin D1 (P=0.016), FADD (P=0.003) and cortactin (P=0.0006) predict for increased risk to disease-specific mortality. Multivariate Cox analysis revealed that only high cortactin expression correlates with disease-specific mortality independent of cyclin D1 and/or FADD. Of genes located in the 11q13 amplicon, cortactin expression is the best predictor for shorter disease-specific survival in late stage laryngeal carcinomas.

Genomic imbalances in 5918 malignant epithelial tumors: an explorative meta-analysis of chromosomal CGH data

BACKGROUND

Chromosomal abnormalities have been associated with most human malignancies, with gains and losses on some genomic regions associated with particular entities.

METHODS

Of the 15429 cases collected for the Progenetix molecular-cytogenetic database, 5918 malignant epithelial neoplasias analyzed by chromosomal Comparative Genomic Hybridization (CGH) were selected for further evaluation. For the 22 clinico-pathological entities with more than 50 cases, summary profiles for genomic imbalances were generated from case specific data and analyzed.

RESULTS

With large variation in overall genomic instability, recurring genomic gains and losses were prominent. Most entities showed frequent gains involving 8q2, while gains on 20q, 1q, 3q, 5p, 7q and 17q were frequent in different entities. Loss "hot spots" included 3p, 4q, 13q, 17p and 18q among others. Related average imbalance patterns were found for clinically distinct entities, e.g. hepatocellular carcinomas (ca.) and ductal breast ca., as well as for histologically related entities (squamous cell ca. of different sites).

CONCLUSION

Although considerable case-by-case variation of genomic profiles can be found by CGH in epithelial malignancies, a limited set of variously combined chromosomal imbalances may be typical for carcinogenesis. Focus on the respective regions should aid in target gene detection and pathway deduction.

The multi-step process of human skin carcinogenesis: A role for p53, cyclin D1, hTERT, p16, and TSP-1

As proposed by Hanahan and Weinberg (2000. Cell 100, 57-70) carcinogenesis requires crucial events such as (i) genomic instability, (ii) cell cycle deregulation, (iii) induction of a telomere length maintenance mechanism, and (iv) an angiogenic switch. By comparing the expression of p53, cyclin D1, p16, hTERT, and TSP-1 in spontaneously regressing keratoacanthoma (KA) as a paradigm of early neoplasia, with malignant invasive cutaneous squamous cell carcinoma (SCC) as a paradigm of advanced tumour development, we are now able to assign the changes in the expression of these proteins to specific stages and allocate them to defined roles in the multi-step process of skin carcinogenesis. We show that mutational inactivation of the p53 gene, and with that the onset of genomic instability is the earliest event. Individual p53-positive cells are already seen in "normal" skin, and 3/5 actinic keratoses (AKs), 5/22 KAs, and 13/23 SCCs contain p53-positive patches. Cell cycle deregulation was indicated by the overexpression of the cell cycle regulator cyclin D1, as well as by the loss of the cell cycle inhibitor p16. Interestingly, overexpression of cyclin D1 - observed in 80% of KAs and SCCs, respectively - showed a cell cycle-independent function in HaCaT cell transplants on nude mice. Cyclin D1 overexpression was associated with a massive inflammatory response, finally leading to tissue destruction. Loss of the cell cycle inhibitor p16, on the other hand, correlated with SCCs. Thus, it is tempting to suggest that overexpression of cyclin D1 is an early change that in addition to growth stimulation leads to an altered epithelial-mesenchymal interaction, while functional p16 is able to control this deregulated growth and needs to be eliminated for malignant progression. Another requirement for uncontrolled growth is the inhibition of telomere erosion by up-regulating telomerase activity. As measured by hTERT protein expression, all of the KAs and SCCs studied were positive, with a similar distribution of the protein in both groups and an expression pattern resembling that of normal epidermis. Thus, telomerase may not need to be increased significantly in skin carcinomas. Finally, we show that the angiogenesis inhibitor TSP-1 is strongly expressed in most KAs, and mainly by the tumour cells, while in SCCs the generally weak expression is restricted to the tumour-stroma. Furthermore, we provide evidence that the loss of a copy of chromosome 15 is responsible for reduced TSP-1 expression and thereby this aberration contributes to tumour vascularisation (i.e. the angiogenic switch) required for malignant growth.

Differential expression of D-type cyclins in HaCaT keratinocytes and in psoriasis

In this study, we show that the G0-G1/S phase of HaCaT keratinocyte cell cycle is characterized by D1-type cyclin expression, whereas during the repeated rapid turnover of highly proliferating cells, the expression of cyclins D2 and D3 dominates. Knocking down cyclin D1 mRNA resulted in no change of cell proliferation and morphology, indicating that D2 and D3 cyclins could substitute for D1 in driving the cell cycle. Increased numbers of cyclin D1-expressing keratinocytes were found in the basal layers of the lesional psoriatic epidermis compared to both normal and non-lesional epidermis without increased expression of cyclin D1 mRNA, suggesting a possible dysfunction in the degradation of cyclin D1 protein. We also detected a significant increase in cyclin D2 and D3 mRNA expressions in psoriatic epidermis compared to normal epidermis with no difference in protein expressions. Blocking alpha5-integrin function by a neutralizing antibody in HaCaT keratinocytes downregulated the expression of cyclin D1 mRNA without affecting the expressions of cyclin D2 and D3 indicating a regulatory role for alpha5-integrin in the expression of cyclin D1. Our data suggest a possible role for D-type cyclins in the excessive basal-cell proliferation and perturbed keratinocyte differentiation in the psoriatic epidermis.

Cellular functions of 14-3-3 zeta in apoptosis and cell adhesion emphasize its oncogenic character

14-3-3 proteins are relevant to cancer biology as they are key regulators of major cellular processes such as proliferation, differentiation, senescence and apoptosis. So far, the sigma isoform (14-3-3sigma) has most directly been implicated in carcinogenesis and was recognized as a tumour-suppressor gene. The other six members of the mammalian 14-3-3 gene family likely behave as oncogenes, although direct evidence supporting this view is largely circumstantial. In this report, we show that knockdown of 14-3-3zeta induces at least two isoform-specific phenotypes that are consistent with a potential oncogenic activity during tumorigenesis. Firstly, downregulation of 14-3-3zeta sensitized cells to stress-induced apoptosis and JNK/p38 signalling and secondly, it enforced cell-cell contacts and expression of adhesion proteins. Apparently, the zeta isoform restrains both cell adhesion and the cellular propensity for apoptosis, two activities that are also restrained during carcinogenesis. The assumption that 14-3-3zeta has oncogenic properties was substantiated with a web-based meta-analysis (Oncomine), revealing that 14-3-3zeta is overexpressed in various types of carcinomas. As the highly conserved human 14-3-3 gene family encodes proteins with either tumour-promoting or tumour-suppressing activities, we infer that the cellular balance between the various 14-3-3 isoforms is crucial for the proper functioning of cells.

Iron chelation regulates cyclin D1 expression via the proteasome: a link to iron deficiency-mediated growth suppression

Iron (Fe) plays an important role in proliferation, and Fe deficiency results in G(1)/S arrest. Despite this, the precise role of Fe in cell-cycle control remains unclear. Cyclin D1 plays a critical function in G(1) progression by interacting with cyclin-dependent kinases. Previously, we examined the effect of Fe depletion on the expression of cell-cycle control molecules and identified a marked decrease in cyclin D1 protein, although the mechanism involved was unknown. In this study, we showed that cyclin D1 was regulated posttranscriptionally by Fe depletion. Iron chelation of cells in culture using desferrioxamine (DFO) or 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone (311) decreased cyclin D1 protein levels after 14 hours and was rescued by the addition of Fe. Cyclin D1 half-life in control cells was 80 +/- 15 minutes (n = 5), while in chelator-treated cells it was significantly (P < .008) decreased to 38 +/- 3 minutes (n = 5). Proteasomal inhibitors rescued the Fe chelator-mediated decrease in cyclin D1 protein, suggesting the role of the proteasome. In Fe-replete cells, cyclin D1 was degraded in an ubiquitin-dependent manner, while Fe depletion induced a ubiquitin-independent pathway. This is the first report linking Fe depletion-mediated growth suppression at G(1)/S to a mechanism inducing cyclin D1 proteolysis.