Expression of mismatch repair enzymes, hMLH1 and hMSH2 is not associated with microsatellite instability and P53 protein accumulation in basal cell carcinoma

Microsatellite instability (MSI) constitutes an alternative-to the chromosomal instability-pathway of carcinogenesis for certain tumour types with prognostic and therapeutic significance for the respective patients. MSI is caused by mutations in mismatch repair (MMR) genes, mainly hMLH1, hMSH2, leading to a defective MMR system. The role of MSI in basal cell carcinoma (BCC) has not been clearly delineated yet. p53 gene as a target for ultraviolet radiation-induced mutations may enhance genomic instability in BCC, with loss of its function. Our aim was to investigate the involvement of MSI and expression of hMLH1 and hMSH2 in parallel with P53 protein accumulation in the pathogenesis of BCC and its possible correlation to the clinicopathological features of the patients. The presence of MSI was investigated in 76 BCCs using mononucleotide microsatellite markers, BAT-25, BAT-26 and TGF-beta receptor type II (TGF-beta-RII). Additionally, 3 dinucleotide markers were analysed in 20 cases in which matched normal tissue was available. The expression of hMLH1, hMSH2 and P53 proteins was evaluated by immunohistochemical analysis. Alterations of the BAT-26 marker were observed in one fibroepithelioma of Pincus, one nodular and one multifocal superficial BCC. A keratotic BCC showed an altered BAT-25 locus. Two samples, a multifocal superficial and a nodular BCC, displayed MSI at two markers (BAT-25 and BAT-26; and BAT-25 and TGF-beta-RII, respectively). Three more cases, a metatypical, a multifocal superficial and a signet ring BCC exhibited frameshift mutations in the TGF-beta-RII. No sample showed length alterations at the dinucleotide markers examined. hMLH1 and hMSH2 protein immunohistochemical expression was scored positive in 46 and 49 out of 52 cases respectively. P53 accumulation was observed in 27 out of 56 samples. Correlation of the molecular and immunohistochemical findings with the clinicopathological parameters produced no statistically significant results. No correlation between MSI and hMLH1, hMSH2 or P53 protein expression was determined. MSI appears to play a minor role in the pathogenesis of BCCs being present only in a small subset of such tumours

Mutations of microsatellite instability target genes in sporadic basal cell carcinomas

Microsatellite instability (MSI) caused by a defective DNA mismatch repair (MMR) system is one of the phenotypes of genomic instability, accounting for the tumorigenesis of certain types of cancers conveying clinical and prognostic significance. Genes such as TGF-βRII, IGFIIR, hMSH3, and hMSH6 include coding mononucleotide repeats that are known targets for mutations in MSI-high tumors. The aim of our study was to investigate the prevalence of mutations in the above 4 MSI target genes in correlation with the MSI status of 75 basal cell carcinomas (BCCs), including aggressive-growth BCCs and cases with perineural invasion. TGF-βRII or hMSH3 frameshift mutations were identified in 5% of the BCCs, including two cases of aggressive-growth subtype, whereas there were no microsatellite alterations in the IGFIIR and hMSH6 genes. Mutations at the mononucleotide repeats within the hMSH3 and TGF-βRII genes occurred in certain BCCs, not always in association with MSI. It seems likely that microsatellite alterations may be important in the development of individual cases of BCCs despite the low frequency of MSI in our cohort. © 2007 Elsevier GmbH. All rights reserved

Epigenetic alterations in sporadic basal cell carcinomas

Basal cell carcinoma (BCC) is the most common malignant human neoplasm characterized by slow growth and virtual absence of metastases. Recently, it has become evident that along with genetic mutations epigenetic alterations play a key role in the pathogenesis of human cancer. We searched for promoter methylation of hMLH1, RASSF1A, DAPK, APC, DCR1 and DCR2 genes and BRAF mutations in BCCs in association with the clinicopathological parameters and the histological subtypes of the tumours. Fifty-two BCCs, 17 FFPE along with 35 fresh tissue samples with matching normal tissues for 26 cases were analyzed by methylation-specific PCR to assess the methylation status of hMLH1, RASSF1A, DAPK, APC, DCR1 and DCR2 genes after sodium bisulfite treatment of the tumour and normal DNA. hMLH1 and DCR1 gene expression was investigated by immunohistochemistry. BRAF mutations were studied by high resolution melting analysis. Methylation was detected at a variable frequency of 44, 33, 32.5, 32 and 14 % of DCR2, APC, DCR1, RASSF1 and DAPK promoters, respectively, whereas methylation of hMLH1 promoter was absent. No BRAF mutations were found. There was no correlation between the frequency of the promoter methylation of the above-mentioned genes and the clinicopathological features or the histological subtypes of the tumours. The relatively high frequency of RASSF1A, DCR1, DCR2 and APC promoter methylation may imply that methylation constitutes an important pathway in the tumourigenesis of BCC that could provide new opportunities in developing epigenetic therapies for BCC patients. Nevertheless, further studies are needed to establish the above-mentioned hypothesis. © 2014 Springer-Verlag

B-Raf mutations, microsatellite instability and p53 protein expression in sporadic basal cell carcinomas

Basal Cell Carcinoma (BCC) is the most common skin malignancy. Genes related to the Ras/Raf signalling pathway have been implicated in the pathogenesis of skin cancer. The objective of this study was to investigate the presence of B-Raf mutations in sporadic BCCs as well as its correlation with the phenotype of microsatellite instability (MSI), the clinicopathological parameters of the tumours and p53 protein expression. 83 BCC specimens were screened for B-Raf mutations, applying polymerase chain reaction, single-stranded conformation polymorphism (PCR-SSCP) and DNA sequencing. MSI status was examined using mononucleotide microsatellite markers and p53 protein expression was demonstrated by immunohistochemical staining. A C to T transition at 1790 nucleotide leading to a silent mutation L597L; and a T to A transversion causing an amino acid change (F610I) have been found. MSI was detected in 5% of the cases and p53 accumulation was present in 37/83 samples studied. Although rare B-Raf alterations have been observed in BCC, none of them harboured the hot-spot mutation T1799A commonly present in melanomas and colon carcinomas. Consequently, no correlation could be determined between B-Raf alterations, MSI status, the clinicopathological features and p53 protein expression. Our results are in favour of a secondary importance for Ras signalling cascade genes in BCC pathogenesis. © 2011 Arányi Lajos Foundation

Comparative immunohistochemical analysis of aurora-A and aurora-B expression in human glioblastomas. Associations with proliferative activity and clinicopathological features

In the present study, we carried out a comparative immunohistochemical analysis of aurora-A and aurora-B expression in 40 patients with primary glioblastomas, and attempted to identify any associations with Ki-67 index and the patients' clinical features. The impact of various treatment modalities and proliferative activity on patient outcome was also assessed. Immunohistochemistry was carried out using formalin-fixed and paraffin-embedded tissue sections. Aurora-A expression was higher in tumors with high Ki-67 expression (p=0.01) and was positively, though marginally, related to aurora-B expression (p=0.085). Aurora-B expression was not linked to Ki-67 expression (p=0.182). Lower aurora-A immunohistochemical expression, chemotherapy administration, and tumor localization in one lobe of the brain implied a greater probability of patient survival in univariate analysis (p=0.044, p=0.008, p=0.041, respectively). Ki-67 and aurora-B immunoreactivities were not associated with patient survival (p=0.918 and p=0.539, respectively). To our knowledge, for the first time, the association between aurora-A and aurora-B expression, the correlation of aurora-A with Ki-67 index, and the prognostic impact of aurora-A expression were assessed in glioblastomas. Although we addressed a prognostic connotation of aurora-A, we presume that aurora-A and aurora-B play a complicated role within glioblastomas. Further examinations of larger series are required, so that definite conclusions can be drawn. © 2009 Elsevier GmbH. All rights reserved