The esophageal epithelium is subject to damage from bile acid reflux that promotes normal tissue injury resulting in the development of Barrett's epithelium. There is a selection pressure for mutating p53 in this preneoplastic epithelium, thus identifying a physiologically relevant model for discovering novel regulators of the p53 pathway. Proteomic technologies were used to identify such p53 regulatory factors by identifying proteins that were overexpressed in Barrett's epithelium. A very abundant polypeptide selectively expressed in Barrett's epithelium was identified as anterior gradient-2. Immunochemical methods confirmed that anterior gradient-2 is universally up-regulated in Barrett's epithelium, relative to normal squamous tissue derived from the same patient. Cancer development is a multistep process involving sequential mutation in oncogenes and tumor suppressor genes that give selective advantage to the evolving cancer cells. The major clinical models that are giving novel molecular mechanistic insight into the multistep evolution of human neoplasia include colorectal and esophageal cancer. Colorectal cancer progression is perhaps the most well-characterized model whereby cancer development evolves through histopathological stages termed dysplasia, adenoma, and carcinoma, which can eventually metastasize. Classic molecular studies in colorectal cancer have indicated that RAS and APC mutations occur earlier in this progression sequence, while p53 mutations occur relatively later (1). Additional modifying factors include genome instability, (2), DNA methylation (3), and associated epigenetic changes in the expression of regulatory genes that can have profound effects on cancer incidence (4).Esophageal adenocarcinoma cancer progression also proceeds through a set of morphological intermediates termed metaplasia and dysplasia, which are collectively called Barrett's esophagus or Barrett's epithelium (5, 6). Barrett's epithelium is thought to develop as an adaptive response following exposure to gastric and duodenal contents refluxed into the esophagus. Barrett's epithelium is a premalignant lesion, and although the progression from Barrett's cell types to adenocarcinoma is not inevitable, the risk is estimated at an increase of 30-to 125-fold as compared with the normal population (7-9) The incidence of Barrett's epithelium has dramatically increased over the last decade; however, more alarming is the parallel increase in adenocarcinoma of the esophagus over a similar period of time (10). Barrett's epithelium being hyperproliferative is believed to be a fertile field for malignant transformation, and such early premalignant lesions produce biological and genetic heterogeneity as seen in previous studies by p53 mutations, aneuploidy, and abnormal methylation resulting in stepwise changes in differentiation, proliferation, and apoptosis (11). However, the environmental, genetic, and metabolic factors that regulate stress responses in normal and Barrett's epithelium, as well as the associated transformation o...

The DEAD box RNA helicase, p68, is upregulated in exponentially growing cells and shows cell cycledependent changes in nuclear localization. Although some other DEAD box proteins have been implicated in cancer, there have been no reports of any link between p68 status and carcinogenesis. In the present study we have analysed specimens from 50 patients with colorectal adenocarcinomas, including cases in which an adenomatous polyp was also present, by immunohistochemistry and Western blotting. Our data indicate that p68 protein is consistently overexpressed in tumours as compared with matched normal tissue. Examination of the levels of p68 mRNA from both normal and tumour tissue showed no obvious speci®c increase in p68 mRNA levels in tumours nor any evidence of underlying mutations in the p68 coding region. Interestingly, however, the accumulated p68 appears to be poly-ubiquitylated, suggesting a possible defect in proteasome-mediated degradation in these tumours. This overexpression/ubiquitylation is observed in both pre-invasive and invasive lesions suggesting that the dysregulation of p68 expression occurs early during tumour development. Finally, we demonstrate that ubiquitylation of p68 occurs in cultured cells, thereby providing a model for the molecular analysis of this process and its potential role in tumorigenesis. Oncogene (2001) 20, 7734 ± 7743.

Background:Observations that diabetics treated with biguanide drugs have a reduced risk of developing cancer have prompted an enthusiasm for these agents as anti-cancer therapies. We sought to determine the efficacy of the biguanide phenformin in the chemoprophylaxis and in the treatment of oestrogen receptor (ER)-positive MCF7 and receptor triple-negative MDAMB231 xenografts in immunocompromised mice. We also compared the efficacy of phenformin and metformin in the treatment of MDAMB231.Methods:Immunocompromised mice were divided into groups: (1) phenformin administered for 2 weeks prior to cell injection; (2) established tumours treated with phenformin; (3) established tumours treated with metformin (only for MDAMB231 tumours); (4) untreated controls. Post-treatment tumours, liver and spleen were harvested for further analysis.Results:Phenformin significantly inhibited both the development and growth of MCF7 and MDAMB231 tumours, and for MDAMB231 at greater efficacy than metformin without murine toxicity. The number of mitotic figures was significantly fewer in xenografts treated with phenformin compared with controls. Results suggested that the mechanism of action of phenformin in vivo is consistent with AMPK activation.Conclusion:Phenformin has clinical potential as an antineoplastic agent and should be considered for clinical trials both in ER-positive and triple-negative breast cancer.

A burgeoning family of p53-related genes have been described recently, including p73 and p63. Both these genes encode proteins with many similarities to p53 but also with the potential for forming a range of related species by alternative promoter usage and alternative splicing. In order to begin the characterization of p63, we generated a polyclonal serum (designated SC1) that recognizes the C-terminus of p63alpha. We have shown that this reagent recognizes p63alpha but not p53 nor p73. By western blot analysis both p63alpha and the N-terminal truncated form of p63alpha (DeltaNp63alpha) were found in a range of cell lines. Similar immunoblot analysis of tissues reveals considerable complexity with at least four SC1-immunoreactive isoforms being identified. In immunohistological studies SC1 immunoreactivity is widely detectable, being predominantly associated with proliferative compartments in epithelia. However, non-proliferative populations can also show SC1 immunostaining. No simple relationship between the isoforms identified by immunoblotting of tissue lysates and the tissue immunostaining characteristics was identified. A previously unrecognized species intermediate in mobility between p63alpha and DeltaNp63alpha was found in several tissues, including nerve and peripheral blood lymphocytes. Interestingly, there is suppression of p63alpha expression in HaCat cells in a time- and concentration-dependent manner after UV and MMS treatment. Our data provide further information about the complexity of p63 and the SC1 serum will prove to be a useful tool in further studies of this p53 homologue.

Mutation of the p53 gene is a common event during tumor pathogenesis. Other mechanisms, such as mdm2 amplification, provide alternative routes through which dysfunction of the p53 pathway is promoted. Here, we address the hypothesis that elevated expression of pim oncogenes might suppress p53 by regulating Mdm2. At a physiological level, we show that endogenous Pim-1 and Pim-2 interact with endogenous Mdm2. Additionally, the Pim kinases phosphorylate Mdm2 in vitro and in cultured cells at Ser 166 and Ser 186 , two previously identified targets of other signaling pathways, including Akt. Surprisingly, at high levels of Pim expression, as would occur in tumors, active, but not inactive, Pim-1 or Pim-2 blocks the degradation of both p53 and Mdm2 in a manner that is independent of Mdm2 phosphorylation, leading to increased p53 levels and, proportionately, p53-dependent transactivation. Additionally, Pim-1 induces endogenous ARF, p53, Mdm2, and p21 in primary murine embryo fibroblasts and stimulates senescence-associated ␤-galactosidase levels, consistent with the induction of senescence. Immunohistochemical analysis of a cohort of 33 human mantle cell lymphomas shows that elevated expression of Pim-1 occurs in 42% of cases, with elevated Pim-2 occurring in 9% of cases, all of which also express Pim-1. Notably, elevated Pim-1 correlates with elevated Mdm2 in MCL with a p value of 0.003. Taken together, our data are consistent with the idea that Pim normally interacts with the p53 pathway but, when expressed at pathological levels, behaves as a classic dominant oncogene that stimulates a protective response through induction of the p53 pathway.

No abstract

Reliable interpretation of results of gene expression at the mRNA level requires standardized protocols for tissue procurement.

The incidence, treatment, and survival of subungual malignant melanomas in Scotland is reviewed from the Scottish Melanoma Group database. Between 1979 and 1989, 100 cases of subungual melanoma were identified (2.8% of all malignant melanomas in Scotland). The tumors tended to be locally advanced at the time of presentation (mean Breslow depth, 4.7 mm +/- 3.0 mm), and this is reflected in an overall 5-year survival of 41%. There was no difference in the survival of patients treated with local/proximal interphalangeal (PIP) joint amputation compared with those having more proximal amputations. Because nearly 70% of these tumors arose on the thumb or hallux, it is concluded that, provided adequate clearance could be obtained, less radical excision should be performed for these lesions to maintain maximum function.