Butyrate is a well known colonic luminal short chain fatty acid, which arrests cell growth and induces differentiation in various cell types. We examined the effect of butyrate on the expression of WAF1/Cip1, a potent inhibitor of cyclin-dependent kinases, and its relation to growth arrest in a p53-mutated human colon cancer cell line WiDr. Five millimolar butyrate completely inhibited the growth of WiDr and caused G 1 -phase arrest. WAF1/Cip1 mRNA was rapidly induced within 3 h by treatment with 5.0 mM butyrate, and drastic WAF1/Cip1 protein induction was detected. Using several mutant WAF1/Cip1 promoter fragments, we found that the butyrate-responsive elements are two Sp1 sites at ؊82 and ؊69 relative to the transcription start site. We also found that a TATA element at ؊46 and two overlapping consensus Sp1 sites at ؊60 and ؊55 are essential for the basal promoter activity of WAF1/Cip1. These findings suggest that butyrate arrests the growth of WiDr by activating the WAF1/Cip1 promoter through specific Sp1 sites in a p53-independent fashion.Butyrate is one of the most abundant short chain fatty acids in the large intestine, generated by bacterial fermentation of dietary fibers (1). Butyrate shows potent effects on growth arrest and differentiation in vitro in various malignant tumor cell lines, such as breast cancer cells, hepatoma cells, and others (2-5). In colorectal cancer cells, butyrate inhibits cell growth and induces differentiation marker proteins such as alkaline phosphatase and carcinoembryonic antigen (6 -9). Furthermore, butyrate arrests the cell cycle progression at the G 1 phase (9) and decreases c-myc oncogene expression in human colon cancer cell lines (9, 10). However, the precise mechanism of growth suppression by butyrate in colon cancer cells has not been clarified. WAF1/Cip1 protein potently inhibits the various G 1 cyclindependent kinases activities (11-13) by suppressing the phosphorylation of retinoblastoma (RB) protein, thereby supposedly inhibiting the G 1 -S phase transition (11,14). Besides its role as a kinase inhibitor, it has been reported recently that WAF1/ Cip1 at low doses assembles kinase complexes and promotes a kinase activity (15). Furthermore, the transcription of the WAF1/Cip1 gene is directly activated by wild-type p53 protein (16). Thus, WAF1/Cip1 could play a key role as a downstream mediator of the p53-induced cell growth arrest.Several studies have already shown the p53-independent induction of WAF1/Cip1 by serum, transforming growth factor ␤, and other differentiation-inducers (17)(18)(19)(20). In addition, butyrate has been reported to induce WAF1/Cip1 mRNA independently of p53 during differentiation of hematopoietic cells, hepatoma cells, and colon cancer cells in vitro (18,21). Butyrate can also dephosphorylate the retinoblastoma protein in mouse fibroblasts (22). To investigate the mechanism of butyrateinduced growth arrest, we used a human colon cancer cell line WiDr harboring a point mutation in p53 at codon 273 (23) and examined the effect of butyrate on t...

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A stimulatory GDP/GTP exchange protein for smg p21 is active on the post-translationally processed form of c-Ki-ras p21 and rhoA p21 (ras ABSTRACTWe have purified a stimulatory GDP/GTP exchange protein for smg p21A and -B, ras p21-like small GTP-binding proteins (G proteins), cloned its cDNA, and named it GDP dissociation stimulator (smg p21 GDS). We show here that smg p21 GDS is active not only on smg p21A and -B but also on c-Ki-ras p21 and rhoA p21, all of which are post-translationally processed. Furthermore, we show that smig p21 GDS is inactive on the post-translationally unprocessed form of these proteins and on the post-translationally processed form of c-Ha-ras p21 and smg p25A. All of the small G proteins recognized by smg p21 GDS have a cDNA-predicted C-terminal "CAAX" motif (where C is cysteine, A is an aliphatic amino acid, and X is any amino acid) and a polybasic region upstream of this motif. These results suggest that smg p21 GDS is at least active on a group of small G proteins having these unique C-terminal structures. Moreover, they suggest that the C-terminal post-translational processing of these small G proteins, by farnesylation or geranylgeranylation of the C-terminal cysteine residue, removal of amino acids in positions denoted "AAX", and carboxyl methylation of the exposed cysteine residue, is important for the sing p21 GDS action.

Trichostatin A (TSA), a specific histone deacetylase inhibitor, induces histone hyperacetylation and modulates the expression of some genes. We examined the effects of TSA on MG63 cells. TSA induced growth arrest and expression of the p21/WAF1/Cip1 protein. A close correlation between the level of histone acetylation and induction of the p21/WAF1/Cip1 protein was detected. Using several mutant p21/WAF1/Cip1 promoter fragments, mutation of either of two Sp1 sites at -82 or -69 of the p21/WAF1/Cip1 promoter reduced the responsiveness to TSA. This finding indicates that TSA activates the p21/WAF1/Cip1 promoter through the Sp1 sites in a p53-independent manner.

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Targeting genetic alterations of oncogenes by moleculartargeted agents (MTA) is an effective approach for treating cancer. However, there are still no clinical MTA options for many cancers, including esophageal cancer. We used a short hairpin RNA library to screen for a new oncogene in the esophageal cancer cell line KYSE70 and identified YES proto-oncogene 1 (YES1) as having a significant impact on tumor growth. An analysis of clinical samples showed that YES1 gene amplification existed not only in esophageal cancer but also in lung, head and neck, bladder, and other cancers, indicating that YES1 would be an attractive target for a cancer drug. Because there is no effective YES1 inhibitor so far, we generated a YES1 kinase inhibitor, CH6953755. YES1 kinase inhibition by CH6953755 led to antitumor activity against YES1-amplified cancers in vitro and in vivo. Yes-associated protein 1 (YAP1) played a role downstream of YES1 and contributed to the growth of YES1amplified cancers. YES1 regulated YAP1 transcription activity by controlling its nuclear translocation and serine phosphorylation. These findings indicate that the regulation of YAP1 by YES1 plays an important role in YES1-amplified cancers and that CH6953755 has therapeutic potential in such cancers. Significance: These findings identify the SRC family kinase YES1 as a targetable oncogene in esophageal cancer and describe a new inhibitor for YES1 that has potential for clinical utility. See related commentary by Rai, p. 5702

We have recently purified to near homogeneity the stimulatory GDP/GTP exchange protein for smg p2ls (ras p21-like GTP-binding proteins) from bovine brain cytosol. This regulatory protein, named GDP dissociation stimulator (GDS), stimulates the GDP/GTP exchange reaction of smg p2ls by stimulating the dissociation of GDP from and the subsequent binding of GTP to them. In this study, we have isolated and sequenced the cDNA of smg p21 GDS from a bovine brain cDNA library by using an oligonucleotide probe designed from the partial amino acid sequence of the purified smg p21 GDS. The cDNA has an open reading frame encoding a protein of 558 amino acids with a calculated Mr value of 61,066, similar to the Mr of 53,000 estimated for the purified smg p21 GDS by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and sucrose density gradient ultracentrifugation. The isolated cDNA is expressed in Escherichia coli, and the encoded protein exhibits smg p21 GDS activity. smg p21 GDS is overall hydrophilic, but there are several short hydrophobic regions. The smg p21 GDS mRNA is present in bovine brain and various rat tissues. smg p21 GDS has low amino acid sequence homology with the yeast CDC25 and SCD25 proteins, which may regulate the GDP/GTP exchange reaction of the yeast RAS2 protein, but not with ras p21 GTPase-activating protein, the inhibitory GDP/GTP exchange proteins (GDP dissociation inhibitor) for smg p25A and rho p2ls, and the IVy subunits of heterotrimeric GTP-binding proteins such as G. and G;. smg p2ls are members of the ras p21/ras p21-like small GTP-binding protein (G protein) superfamily and are composed of smg p21A and -B (26, 35; for reviews, see references 1 and 50). smg p21A is identical to the raplA and Krev-1 proteins, and smg p21B is identical to the raplB protein (26,29,35,42,43). Both smg p21A and -B have the same putative effector domain as those of Ha-, N-, Ki(2A)-, and Ki(2B)-ras p2ls (1,26,29,35,42,43). This structural property suggests that smg p2is share the same effector protein(s) with ras p2is and exert actions similar or antagonistic to those of ras p2is in addition to their own specific actions. Consistently, the Krev-1 gene has been shown to suppress the transforming activity of the activated Ki-ras gene in NIH 3T3 cells (29). Both smg p21A and -B have the consensus motif Cys-A-A-X (where A is an aliphatic amino acid and X is any amino acid) in their C-terminal region, the same motif as that of ras p2ls (1,26,29,35,42,43,50). This consensus motif of ras p2ls is known to be posttranslationally processed (for a review, see reference 44). smg p21B also undergoes three posttranslational modifications in the C-terminal region: geranylgeranylation at the cysteine residue, removal of the three C-terminal amino acids, and carboxyl methylation of the exposed cysteine residue (24).Both smg p21A and -B have GDP-bound inactive and GTP-bound active forms, as described for ras p2ls (1, 50). The conversion of smg p2ls from the GDP-bound to GTPbound form is induced by the GDP/GTP exchange reaction,...

An aqueous methanol extract of the Oriental crude drug "sohaku-hi", the root barks of Morus alba, prominently reduced the plasma sugar level in mice. Activity-guided fractionation of the extract furnished a glycoprotein, moran A, which elicited remarkable hypoglycemic effects in normal and alloxan-induced hyperglycemic mice.