Loss of RUNX3 expression is suggested to be causally related to gastric cancer as 45% to 60% of gastric cancers do not express RUNX3 mainly due to hypermethylation of the RUNX3 promoter. Here, we examined for other defects in the properties of RUNX3 in gastric cancers that express RUNX3. Ninety-seven gastric cancer tumor specimens and 21 gastric cancer cell lines were examined by immunohistochemistry using novel anti-RUNX3 monoclonal antibodies. In normal gastric mucosa, RUNX3 was expressed most strongly in the nuclei of chief cells as well as in surface epithelial cells. In chief cells, a significant portion of the protein was also found in the cytoplasm. RUNX3 was not detectable in 43 of 97 (44%) cases of gastric cancers tested and a further 38% showed exclusive cytoplasmic localization, whereas only 18% showed nuclear localization. Evidence is presented suggesting that transforming growth factor-B is an inducer of nuclear translocation of RUNX3, and RUNX3 in the cytoplasm of cancer cells is inactive as a tumor suppressor. RUNX3 was found to be inactive in 82% of gastric cancers through either gene silencing or protein mislocalization to the cytoplasm. In addition to the deregulation of mechanisms controlling gene expression, there would also seem to be at least one other mechanism controlling nuclear translocation of RUNX3 that is impaired frequently in gastric cancer. (Cancer Res 2005; 65(17): 7743-50)

The NAD(+)-dependent protein deacetylase SIRT1 is linked to cellular survival pathways by virtue of keeping the tumor suppressor gene p53 and members of the forkhead transcription factor family deacetylated. To validate SIRT1 as a therapeutic anti-cancer target, we performed immunohistochemistry experiments to study the in vivo expression of SIRT1 in cancer specimens. We show that human SIRT1 is highly expressed in cancer cell lines as well as in tissue samples from colon carcinoma patients. Interestingly, there is a strong cytosolic component in the SIRT1 expression pattern. We further characterized SIRT1 in p53-wild-type and -mutant cell lines and show that SIRT1 mRNA-knockdown leads to a p53-independent decrease of cell proliferation and induction of apoptosis. In addition, SIRT1 expression has been found to be inducible upon DNA damage. A previously discovered small molecule SIRT1 inhibitor with nanomolar in vitro activity has been tested in cancer relevant assays. The SIRT1 inhibitory compound showed no potent anti-proliferative activity despite hitting its molecular target within tumor cells. From these studies we conclude that it may not be sufficient to block the catalytic function of SIRT1, and that its survival effects may be mainly brought about by means other then the deacetylase function. The increased cytosolic expression of SIRT1 in cancer cells could be an indicator of such novel functions.

Basal cell carcinomas (BCC), which are the most common form of skin malignancy, are invariably associated with the deregulation of the Sonic Hedgehog (Shh) signalling pathway. As such, BCC represent a unique model for the study of interactions of the Shh pathway with other genes and pathways. We constructed a tissue microarray (TMA) of 75 paired BCC and normal skin and analysed the expression of b-catenin and RUNX3, nuclear effectors of the wingless-Int (Wnt) and bone morphogenetic protein/ transforming growth factor-b pathways, respectively. In line with previous reports, we observed varying subcellular expression pattern of b-catenin in BCC, with 31 cases (41%) showing nuclear accumulation. In contrast, all the BCC cases tested by the TMA showed RUNX3 protein uniformly overexpressed in the nuclei of the cancer cells. Analysis by Western blotting and DNA sequencing indicates that the overexpressed protein is normal and full-length, containing no mutation in the coding region, implicating RUNX3 as an oncogene in certain human cancers. Our results indicate that although the deregulation of Wnt signalling could contribute to the pathogenesis of a subset of BCC, RUNX3 appears to be a universal downstream mediator of a constitutively active Shh pathway in BCC.

RUNX3 is believed to have tumour suppressor properties in several cancer types. Inactivation of RUNX3 has been shown to occur by methylation-induced transcriptional silencing and by mislocalization of the protein to the cytoplasm. The aim of this study was to examine the clinical significance of RUNX3 expression in a large series of colorectal cancers using immunohistochemistry and tissue arrays. With advancing tumour stage, expression of RUNX3 in the nucleus decreased, whereas expression restricted to the cytoplasmic compartment increased. Nuclear RUNX3 expression was associated with significantly better patient survival compared to tumours in which the expression of RUNX3 was restricted to the cytoplasm (P ¼ 0.025). These results support a role for RUNX3 as a tumour suppressor in colorectal cancer. The RUNX3 gene encodes a protein that belongs to the runt domain family of transcription factors involved in mammalian development pathways (Ito, 2008). RUNX3 protein can mediate the growth suppressive effects of TGF-b by associating with SMAD, a downstream protein in the signalling pathway (Ito and Miyazono, 2003). In RUNX3 knockout mice, the gastric epithelium displays hyperplasia and a reduced sensitivity to TGF-b (Li et al, 2002). The chromosomal locus for RUNX3 (1p36) shows frequent loss of heterozygosity in a variety of cancer types including colon and gastric carcinomas (Ito, 2008). In addition, mutations in RUNX3 have been shown in gastric (Li et al, 2002) and bladder cancers. Recent work from our group has also shown that RUNX3 protein forms a ternary complex with b-catenin/TCF4 . This complex has reduced DNA-binding ability and thus attenuates the level of signalling through the Wnt pathway. The above findings suggest a putative tumour suppressor role for RUNX3 in intestinal tumourigenesis.Other studies have shown methylation-related transcriptional silencing of RUNX3 expression in gastric (Li et al, 2002;Waki et al, 2003), colorectal (CRC) (Goel et al, 2004;Ku et al, 2004) and oesophageal squamous cell (Sakakura et al, 2007) carcinomas. A relatively high frequency of RUNX3 methylation has also been observed in hepatocellular carcinoma and lung, breast and prostate cancers . Mislocalisation of RUNX3 protein to the cytoplasm is another mechanism by which RUNX3 can be inactivated in gastric and breast cancers Lau et al, 2006). Overexpression of the enhancer of zeste homologue 2 (EZH2) protein was recently shown to downregulate RUNX3 expression by increasing histone H3 methylation, thus providing yet another mechanism for inactivation of RUNX3 (Fujii et al, 2008). As might be expected, if RUNX3 were behaving as a tumour suppressor, the decreased expression of this protein in gastric (Wei et al, 2005), lung (Araki et al, 2005) and oesophageal (Sakakura et al, 2007) cancers has been associated with worse patient outcome.As the TGF-b signalling pathway plays an important role in the growth control of human colonic epithelial cells (Xu and Pasche, 2007), RUNX3 may also act as a tumour suppressor gene in this tis...

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Background: Members of the TRIP-Br/SERTAD family of mammalian transcriptional coregulators have recently been implicated in E2F-mediated cell cycle progression and tumorigenesis. We, herein, focus on the detailed functional characterization of the least understood member of the TRIP-Br/SERTAD protein family, TRIP-Br2 (SERTAD2).

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This study aimed to (1) determine if ammonia (as NH(4)Cl) injected intra-peritoneally into the ureogenic slender African lungfish, Protopterus dolloi, was excreted directly rather than being converted to urea; (2) examine if injected urea was retained in this lungfish, leading to decreases in liver arginine and brain tryptophan levels, as observed during aestivation on land; and (3) elucidate if increase in internal ammonia level would affect urea excretion, when ammonia and urea are injected simultaneously into the fish. Despite being ureogenic, P. dolloi rapidly excreted the excess ammonia as ammonia within the subsequent 12 h after NH(4)Cl was injected into its peritoneal cavity. Injected ammonia was not detoxified into urea through the ornithine-urea cycle, probably because it is energetically intensive to synthesize urea and because food was withheld before and during the experiment. In addition, injected ammonia was likely to stay in extracellular compartments available for direct excretion. At hour 24, only a small amount of ammonia accumulated in the muscle of these fish. In contrast, when urea was injected intra-peritoneally into P. dolloi, only a small percentage (34%) of it was excreted during the subsequent 24-h period. A significant increase in the rate of urea excretion was observed only after 16 h. At hour 24, significant quantities of urea were retained in various tissues of P. dolloi. Injection with urea led to an apparent reduction in endogenous ammonia production, a significant decrease in the hepatic arginine content, and a significantly lower level of brain tryptophan in this lungfish. All three phenomena had been observed previously in aestivating P. dolloi. Hence, it is logical to deduce that urea synthesis and accumulation could be one of the essential factors in initiating and perpetuating aestivation in this lungfish. Through the injection of NH(4)Cl + urea, it was demonstrated that an increase in urea excretion occurred in P. dolloi within the first 12 h post-injection, which was much earlier than that of fish injected with urea alone. These results suggest that urea excretion in P. dolloi is likely to be regulated by the level of internal ammonia in its body.