A functional SNP in the MDM2 promoter mediates E2F1 affinity to modulate cyclin D1 expression in tumor cell proliferation

BACKGROUND

The MDM2 oncogene, a negative regulator of p53, has a functional polymorphism in the promoter region (SNP309) that is associated with multiple kinds of cancers including non-melanoma skin cancer. SNP309 has been shown to associate with accelerated tumor formation by increasing the affinity of the transcriptional activator Sp1. It remains unknown whether there are other factors involved in the regulation of MDM2 transcription through a trans-regulatory mechanism.

METHODS

In this study, SNP309 was verified to be associated with overexpression of MDM2 in tumor cells. Bioinformatics predicts that the T to G substitution at SNP309 generates a stronger E2F1 binding site, which was confirmed by ChIP and luciferase assays.

RESULTS

E2F1 knockdown downregulates the expression of MDM2, which confirms that E2F1 is a functional upstream regulator. Furthermore, tumor cells with the GG genotype exhibited a higher proliferation rate than TT, correlating with cyclin D1 expression. E2F1 depletion significantly inhibits the proliferation capacity and downregulates cyclin D1 expression, especially in GG genotype skin fibroblasts. Notably, E2F1 siRNA effects could be rescued by cyclin D1 overexpression.

CONCLUSION

Taken together, a novel modulator E2F1 was identified as regulating MDM2 expression dependent on SNP309 and further mediates cyclin D1 expression and tumor cell proliferation. E2F1 might act as an important factor for SNP309 serving as a rate-limiting event in carcinogenesis.

Blocking glutamate-mediated signalling inhibits human melanoma growth and migration

Glutamate is an excitatory neurotransmitter that has been shown to regulate the proliferation, migration and survival of neuronal progenitors in the central nervous system through its action on metabotropic and ionotropic glutamate receptors (GluRs). Antagonists of ionotropic GluRs have been shown to cause a rapid and reversible change in melanocyte dendritic morphology, which is associated with the disorganization of actin and tubulin microfilaments in the cytoskeleton. Intracellular expression of microtubule-associated protein (MAP) 2a affects the assembly, stabilization and bundling of microtubules in melanoma cells; stimulates the development of dendrites; and suppresses melanoma cell migration and invasion. In this study, we investigated the relationship between glutamate-mediated signalling and microtubules, cell dendritic morphology and melanoma cell motility. We found that metabotropic GluR1 and N-methyl-d-aspartate receptor antagonists increased dendritic branching and inhibited the motility, migration and proliferation of melanoma cells. We also demonstrated that the invasion and motility of melanoma cells are significantly inhibited by the combination of increased expression of MAP2a and either metabotropic GluR1 or N-methyl-d-aspartate receptor antagonists. Moreover, the blockade of glutamate receptors inhibited melanoma growth in vivo. Collectively, these results demonstrate the importance of glutamate signalling in human melanoma and suggest that the blockade of glutamate receptors is a promising novel therapy for treating melanoma.

Increased expression of MAP2 inhibits melanoma cell proliferation, invasion and tumor growth in vitro and in vivo

Malignant melanoma (MM) is characterized by aggressive metastasis and high mortality rate. Microtubule-associated proteins 2 (MAP2) is expressed abundantly in majority of melanocytic nevi and primary melanomas, but absent in metastatic melanomas. To determine whether MAP2 correlates with tumor progression of MM, we investigated the effects of MAP2 inhibition on the biological behaviour of metastatic melanoma in vitro and in vivo. Our results demonstrated that adenovirus-mediated MAP2 induced apoptotic cell death and cell cycle arrest in metastatic human and mouse melanoma cell lines in vitro, and substantially inhibited the growth of melanomas in nude mice in vivo. In addition, intracellular expression of MAP2 was found to induce the morphologic alteration, suppress the migration and invasion and affect the assembly, stabilization and bundling of microtubules in melanoma cells. This is the first study that MAP2 expression significantly inhibits the growth of MM in vivo. Our results suggest that MAP2 may serve as a promising molecular target for therapy and chemoprevention of MM in humans.

Acitretin induces apoptosis through CD95 signalling pathway in human cutaneous squamous cell carcinoma cell line SCL-1

Skin cancers are by far the most common human malignancies. Retinoids have shown promising preventive and therapeutic effects against a variety of human malignancies. The aim of this study was to investigate the apoptosis-inducing effect of acitretin on human skin squamous cell carcinoma (SCC) SCL-1 cells. We found that acitretin preferentially inhibited the growth of SCL-1 cells in a dose- and time-dependent manner, but not of non-malignant keratinocyte HaCaT cells. This inhibition appeared to be due to induction of apoptosis as revealed by enzyme-linked immunosorbent assay. AnnexinV/propidium iodide assay and morphological observation confirmed the pro-apoptotic effect of acitretin on SCL-1 cells. We further demonstrated that apoptosis was induced within 1-2 days and involved activation of caspases-8, -9, -3 and poly (ADP-ribose) polymerase (PARP). Caspase-8 inhibitor effectively suppressed acitretin-induced apoptosis whereas caspase-9 inhibitor did not. Acitretin increased the levels of CD95 (Fas), CD95-ligand and Fas-associated death domain. Neutralizing ZB4 anti-Fas antibody significantly inhibited the apoptosis in SCL-1 cells induced by acitretin. These results suggest that acitretin is able to induce apoptosis in skin cancer cells possibly via death receptor CD95 apoptosis pathway without affecting the viability of normal keratinocyte.

Loss-of-function mutations of an inhibitory upstream ORF in the human hairless transcript cause Marie Unna hereditary hypotrichosis

Marie Unna hereditary hypotrichosis (MUHH) is an autosomal dominant form of genetic hair loss. In a large Chinese family carrying MUHH, we identified a pathogenic initiation codon mutation in U2HR, an inhibitory upstream ORF in the 5' UTR of the gene encoding the human hairless homolog (HR). U2HR is predicted to encode a 34-amino acid peptide that is highly conserved among mammals. In 18 more families from different ancestral groups, we identified a range of defects in U2HR, including loss of initiation, delayed termination codon and nonsense and missense mutations. Functional analysis showed that these classes of mutations all resulted in increased translation of the main HR physiological ORF. Our results establish the link between MUHH and U2HR, show that fine-tuning of HR protein levels is important in control of hair growth, and identify a potential mechanism for preventing hair loss or promoting hair removal.

Combination of short CAG and GGN repeats in the androgen receptor gene is associated with acne risk in North East China

BACKGROUND

Acne vulgaris is one of the most common skin disorders, and androgen is known to play a key role in the development of acne. However, the exact genetic mechanism by which androgen receptor (AR) gene affects acne development is still unclear.

OBJECTIVE

Our study aimed to investigate whether CAG and GGN polymorphism of the AR gene are associated with acne risk.

PATIENTS AND METHODS

Two hundred thirty-eight patients and 207 controls were included in the study. The repeat lengths of the AR gene were determined by GeneScan analysis.

RESULTS

Men with CAG < 23 and women with CAG < 24 had significant risk compared to those men with CAG > or = 23 [odds ratio (OR), 2.07; 95% confidence interval (95% CI), 1.21-3.54] and women with CAG > or = 24 (OR, 2.05; 95% CI, 1.18-3.56). In males, GGN repeats, considered independently of the CAG repeat, have no significant effect on the acne risk; however, when combined with CAG repeats, the acne patients exhibited significantly higher frequency of the haplotypes CAG < 23/GGN < or = 23 (OR, 3.33; 95% CI, 1.10-10.07; P < 0.05) compared with the controls.

CONCLUSION

Our results of this study strongly indicated that a shorter CAG repeat length and specific haplotypes of AR attributed to the risk of acne development and thus could serve as a susceptibility marker.

Childhood bullous pemphigoid treated by i.v. immunoglobulin

Bullous pemphigoid is an acquired autoimmune subepidermal blistering disorder mostly seen in the elderly. Childhood bullous pemphigoid is very rare. For the first time we report a case of childhood bullous pemphigoid associated with infantile eczema. Two weeks after a routine vaccination, a 3.5-month-old boy with infantile eczema developed a generalized blistering disorder. Histopathology revealed a subepidermal blister. Direct immunofluorescence showed linear depositions of C3 along the basement membrane zone. Indirect immunofluorescence studies demonstrated the presence of circulating immunoglobulin G antibodies directed against the epidermal side of salt-split skin. Enzyme-linked immunosorbent assay demonstrated serum level of anti-BP180 antibody elevated. The patient was successfully treated by high-dose i.v. immunoglobulin.

Juvenile generalized pustular psoriasis

Generalized pustular psoriasis (GPP) is an erythrodermic, generalized form of pustular psoriasis. GPP is rare in children. The present study describes a case of juvenile GPP and reviews 12 juvenile GPP inpatients treated at our hospital in the period 1978-2005.

Sweet's syndrome associated with skin methicillin-resistant Staphylococcus epidermidis infection

A 53-year-old Chinese man presented with fever, a painful exudative plaque around his left eye and subsequent multiple tender plaques and nodules on his bilateral face, neck and back. He had a 12-year history of refractory anemia, a subtype of myelodysplastic syndrome. Repeated bacterial cultures of exudates from the lesion of the left zygomatic area showed growth of methicillin-resistant Staphylococcus epidermidis. A biopsy of a plaque on the back showed edema of the papillary dermis and marked neutrophilic infiltrates in the upper dermis. The patient was diagnosed with Sweet's syndrome (SS), and responded well to combination therapy of amoxycilline/sulbactam and corticosteroids. To our knowledge, this is the first reported case of SS associated with skin S. epidermidis infection.

Seven novel mutations of the ADAR gene in Chinese families and sporadic patients with dyschromatosis symmetrica hereditaria (DSH)

Dyschromatosis symmetrica hereditaria (DSH) is an autosomal dominant pigmentary genodermatosis characterized by hyperpigmented and hypopigmented macules of on the extremities and caused by the mutations in the ADAR gene(also called DSRAD) encoding for RNA-specific adenosine deaminase. Here we reported clinical and molecular findings of 6 Chinese multi-generation families and 2 sporadic patients with DSH. We found that the same mutation could lead to different phenotypes even in the same family and we did not establish a clear correlation between genotypes and phenotypes. Seven novel heterozygous mutations of ADAR were identified, which were c.2433_2434delAG (p.T811fs), c.2197G>T (p.E733X), c.3286C>T (p.R1096X), c.2897G>T (p.C966F), c.2797C>T (p.Q933X), c.2375delT (p.L792fs) and c.3203-2A>G respectively. Our data add new variants to the repertoire of ADAR mutations in DSH.

Refined localization of dyschromatosis symmetrica hereditaria gene to a 9.4-cM region at 1q21-22 and a literature review of 136 cases reported in China

BACKGROUND

Dyschromatosis symmetrica hereditaria (DSH) is an autosomal dominant pigmentary genodermatosis characterized by hyperpigmented and hypopigmented macules on the extremities, which has recently been mapped to an 11.6-cM interval on chromosome 1q11-21. So far, most cases of DSH have been reported in Japan and dermatologists around the world might think this disorder mainly occurs in Japan. In fact, there are 17 DSH families including 136 cases reported in China since 1980, but most of them are described in Chinese.

OBJECTIVES

To refine the previously mapped region that facilitates the identification of the DSH gene and to delineate the clinical and genetic features of Chinese DSH cases by a literature review of 136 cases reported in China.

METHODS

We performed genotyping and linkage analysis using polymorphic microsatellite markers at 1q11-22 in two Chinese DSH families, and reviewed all of the DSH cases reported in China since 1980.

RESULTS

A cumulative maximum two-point lod score of 3.68 was produced with marker D1S506 at a recombination frequency of theta = 0.00 in these two families. Haplotype analysis refined the DSH locus to a 9.4-cM interval flanked by D1S2343 and D1S2635. The genetic and clinical features of Chinese cases with DSH were summarized. In some Chinese cases, hyperpigmented and hypopigmented macules were scattered on the neck and chest, but among Japanese patients there were no similar skin lesions to be reported on these sites.

CONCLUSIONS

This study confirms linkage of DSH to a previously mapped region and refines the DSH gene to a 9.4-cM interval at 1q21-22. Likewise, the literature review indicates that DSH is not an uncommon disorder in China and the differences in the distribution of skin lesions could be related to race and environment.

Reactivity of monoclonal antibody OKM5 with sebaceous carcinoma

Two cases of sebaceous carcinoma (SC), as well as epithelial tumours, melanoma, and lymphoma, were examined using immunoperoxidase and a panel of monoclonal antibodies on cryostat sections. The results showed that, whereas all SC cells in both cases reacted strongly with monoclonal antibody OKM5, other tumour cells (except juvenile xanthogranuloma cells) did not. The pagetoid cells within the epidermis of SC also reacted with OKM5 antibody. Although the nature of the phenomenon merits further study, this reactivity, or cross-reactivity, might possibly aid diagnosis of SC.