Somatic p16INK4a loss accelerates melanomagenesis

Loss of p16INK4a–RB and ARF–p53 tumor suppressor pathways, as well as activation of RAS–RAF signaling, is seen in a majority of human melanomas. Although heterozygous germline mutations of p16INK4a are associated with familial melanoma, most melanomas result from somatic genetic events: often p16INK4a loss and N-RAS or B-RAF mutational activation, with a minority possessing alternative genetic alterations such as activating mutations in K-RAS and/or p53 inactivation. To generate a murine model of melanoma featuring some of these somatic genetic events, we engineered a novel conditional p16INK4a-null allele and combined this allele with a melanocyte-specific, inducible CRE recombinase strain, a conditional p53-null allele and a loxP-stop-loxP activatable oncogenic K-Ras allele. We found potent synergy between melanocyte-specific activation of K-Ras and loss of p16INK4a and/or p53 in melanomagenesis. Mice harboring melanocyte-specific activated K-Ras and loss of p16INK4a and/or p53 developed invasive, unpigmented and nonmetastatic melanomas with short latency and high penetrance. In addition, the capacity of these somatic genetic events to rapidly induce melanomas in adult mice suggests that melanocytes remain susceptible to transformation throughout adulthood

Immune signatures in human PBMCs of idiotypic vaccine for HCV-related lymphoproliferative disorders

Hepatitis C virus (HCV) is one of the major risk factors for chronic hepatitis, which may progress to cirrhosis and hepatocellular carcinoma, as well as for type II mixed cryoglobulinemia (MC), which may further evolve into an overt B-cell non-Hodgkin's lymphoma (NHL)

Transcriptional impairment of beta-catenin/E-cadherin complexis not associated with beta-catenin mutations in colorectal carcinomas

We report the absence of beta-catenin mutations in 63 sporadic colorectal carcinomas (SCRCs) with demonstrated decreased beta-catenin and E-cadherin mRNA expression and E-cadherin protein expression in a subset of carcinomas examined, suggesting that beta-catenin mutations are an extremely rare phenomenon in SCRCs and are not responsible for the transcriptional impairment of the beta-catenin/E-cadherin adhesion complex observed in these tumours. (C) 2003 Cancer Research UK

Hypermethylation-associated transcriptional silencing of E-cadherin in primary sporadic colorectal carcinomas

Loss of E (epithelial)-cadherin expression has been previously documented in sporadic colorectal carcinomas (SCRCs), but not as a consequence of mutations or allelic loss. In this study, the methylation status of the E-cadherin promoter was examined by, utilizing the methylation-specific polymerase chain reaction (MSP) assay in 63 primary SCRCs and paired adjacent normal tissues. This was correlated with F-cadherin expression at both the RNA and the protein levels using multiplex reverse transcription (RT)-PCR and immunohistochemistry (IHC), respectively. Data were associated with the patients’ clinicopathological features. Methylated alleles were present in 34/61 (56%) of the samples examined. Decreased E-cadherin mRNA expression was demonstrated in 29/61 carcinomas (47.5%) and was significantly associated with lymph node (LN) metastases (p = 0.03, Kruskal-Wallis) and tumour stages Astler-Coller B1 and B2 (p = 0.01, chi(2)). E-cadherin IHC expression was significantly associated with the absence of LN metastases (p = 0.01, chi2) and tumour stages Astler-Coller B1 and B2 (p = 0.002, Kruskal-Wallis) in 28/63 (44.4%) of the samples examined. Twenty-three out of 29 (79.3%) samples with decreased mRNA expression and 20/33 (60.6%) with detected protein expression revealed methylated (p = 0.03, Kruskal-Wallis) and unmethylated (p = 0.01, Kruskal-Wallis) alleles, respective]),. In agreement with previous work demonstrating that somatic mutations and loss of heterozygosity of the E-cadherin gene are rare or absent in the majority, of SCRCs studied so far, this study reports a consistent and uniform decrease or absence of E-cadherin expression. associated with aberrant methylation, in the majority of carcinomas examined, suggesting an epigenctically mediated loss of E-cadherin function in these carcinomas. Copyright (C) 2002 John Wiley Sons, Ltd