Sabrina Angelini

Activating BRAF and N-Ras mutations in sporadic primary melanomas: an inverse association with allelic loss on chromosome 9.

We searched and report mutations in the BRAF and N-ras genes in 22 out of 35 (63 percent) primary sporadic melanomas. In three melanomas, mutations were concomitantly present in both genes. In all, 10 out of 12 mutations in the BRAF gene involved the ‘hot spot’ codon 600 (In all communications on mutations in the BRAF gene, the nucleotide and codon numbers have been based on the NCBI gene bank nucleotide sequence NM_004333. However, according to NCBI gene bank sequence with accession number NT_007914, there is a discrepancy of one codon (three nucleotides) in exon 1 in the sequence with accession number NM_004333. The sequence analysis of exon 1 of the BRAF gene in our laboratory has shown that the sequence derived from NT_007914 is correct (Kumar et al., 2003). Due to the correctness of the latter, sequence numbering of codons and nucleotides after exon 1 are changed by +1 and +3, respectively.), one tandem CT1789-90TC base change represented a novel mutation and another mutation caused a G466R amino-acid change within the glycine-rich loop in the kinase domain. Mutations in the N-ras gene in 11 melanomas were at codon 61 whereas two melanomas carried mutations in codon 12 including a tandem mutation GG>AA. We observed an inverse association between BRAF/N-ras mutations and the frequency of loss of heterozygosity (LOH) on chromosome 9 at 10 different loci. Melanomas with BRAF/N-ras mutations showed a statistically significant decreased frequency of LOH on chromosome 9 compared with cases without mutations (mean fractional allelic loss (FAL)=0.29±0.23 vs 0.72±0.33; t-test, P=0.0001). Difference in the FAL value between tumours with and without BRAF/N-ras mutations on 33 loci on five other chromosomes was not statistically significant (mean FAL 0.17±0.19 vs 0.25±0.22; t-test, P=0.24). Melanoma cases with BRAF/N-ras mutations were also associated with lower age at diagnosis than cases without mutations (mean age 80.38±7.24 vs 65.77±19.79 years; t-test, P=0.02). Our data suggest that the occurrence of BRAF/N-ras mutations compensate the requirement for the allelic loss at chromosome 9, which is one of the key events in melanoma.

Mutations in the BRAF and N-ras genes in childhood acute lymphoblastic leukaemia

selected cell line models, suppression of Ras signaling or the farnesylated Rho-B proteins promotes heterotypic adhesion through activation of beta-1 and/or beta-2 integrin binding avidity or increased sensitivity to the inhibitory effects of TGFb, suggesting that promotion of heterotypic adhesion may arise as a class effect of Ras protein signal inhibition. Additional investigations are necessary to discern the relevant cellular target(s) of lonafarnib and possibly other FTIs that may promote transient expansion of leukemia mass and possibly predispose to endovascular complications.

Low frequency of BRAF and CDKN2A mutations in endometrial cancer.

Several pathways have been implicated in the pathogenesis of endometrial carcinoma. Based on recent reports, BRAF mutations provide an alternative route for activation of the RAS signalling pathway. The CDKN2A (p16) tumour suppressor gene is also altered in several tumour types. We therefore wanted to assess the pattern and prognostic impact of BRAF mutations and p16 alterations in endometrial carcinomas. Only 1 of 48 tumours (2%) was found to have a BRAF mutation in exon 15, whereas 8 of 45 tumours (18%) had a K‐ras mutation. Homozygous deletion, amplification, promoter region methylation or mutation of the p16 gene was seen in 6 cases (13%), and 18 cases (38%) carried polymorphisms in the p16 gene. All tumours with presence of p16 methylation, non‐sense mutation, deletion or amplification exhibited loss of p16 expression as evaluated by immunohistochemistry. Presence of a p16 hit was significantly correlated with high FIGO stage (p = 0.04), high histologic grade (p = 0.02), estrogen receptor negativity (p = 0.05), pathologic expression of p53 (p = 0.02), pathologic expression of p16 (p = 0.05) and poor survival (p = 0.02). There was also a significant correlation between loss of p16 expression and K‐ras mutations, pathologic p53 expression and serous papillary/clear cell histologic types (p = 0.05/p = 0.001/p = 0.002). In conclusion, BRAF mutation is an infrequent finding in endometrial carcinomas. Loss of p16 expression is seen in all cases with alterations of the p16 gene. The presence of a p16 hit might be important in a subset of endometrial carcinomas with aggressive clinical behaviour. However, the mechanism of p16 inactivation remains unclear for the majority of cases exhibiting loss of expression, but the interactions with K‐ras and p53 should be further studied.

Role of quercetin in modulating rat cardiomyocyte gene expression profile

Despite extensive studies, the fundamental mechanisms responsible for the development and progression of cardiovascular diseases have not yet been fully elucidated. Recent experimental and clinical studies have suggested that reactive oxygen species play a major pathological role. Oxidative stress reduction induced by flavonoids has been regarded by many as the most likely mechanism in the protective effects of these compounds; however, there is an emerging view that flavonoids may also exert modulatory actions on protein kinase and lipid kinase signaling pathways. Quercetin, a major flavonoid present in the human diet, has been widely studied, and its biological properties are consistent with its protective role in the cardiovascular system. However, it remains unknown whether the cardioprotective effects of quercetin may also occur through the modulation of genes involved in cell survival. The main goal of this study was to examine the gene expression profiling of cultured rat primary cardiomyocytes treated with quercetin using DNA microarrays and to relate these data to functional effects. Results showed distinct temporal changes in gene expression induced by quercetin and a strong upregulation of phase 2 enzymes, highlighting quercetin ability to act also with an indirect antioxidant mechanism.

Influence of XPD variant alleles on p53 mutations in lung tumors of nonsmokers and smokers

Abstract The DNA repair protein XPD is involved in the transcription-coupled nucleotide excision repair of DNA lesions induced by many tobacco and environmental carcinogens. Common polymorphisms in XPD exon 10 (G>A, Asp312Asn) and exon 23 (A>C, Lys751Gln) have been identified, and lung cancer cases homozygous for the variant allele in either exon have been reported to have a reduced repair capacity against benzo[ a ]pyrene-induced DNA damage. We therefore investigated a possible effect of these variant alleles on the p53 mutation frequency and spectrum among 97 Swedish lung cancer patients. Transversions were found to occur more frequently among patients with at least one variant allele than among wild type homozygotes. The XPD variant alleles may thus be associated with reduced DNA repair proficiency. This finding is not in accord with the previous report that associated the exon 23 wild type allele with increased frequency of X-ray-induced chromatid aberrations.