Search

N6-isopentenyladenosine (i6A) is a modified nucleoside with a pentaatomic isopentenyl derived from mevalonate that induces inhibition of tumor cell proliferation and apoptosis in several tumor cell lines. In this study, we reported that N6-isopentenyladenosine inhibited the proliferation and promotes apoptosis in DLD1 human colon cancer cells. It suppressed the proliferation of cells through inhibition of DNA synthesis, causing a cell cycle arrest that correlated with a decrease in the levels of cyclin E, cyclin A and cyclin D1 and with a concomitant increase in the levels of cyclin-dependent kinase inhibitor p21waf and p27kip1. Moreover, it induced apoptosis through an increase in the number of annexin V-positive cells, a downregulation of antiapoptotic products and caspase-3 activation. The apoptotic effects of N6-isopentenyladenosine were accompanied by sustained phosphorylation and activation of c-jun N-terminal kinase (JNK) that induced phosphorylation of c-jun. Overall, our data show that JNK, could play an important role in i6A-mediated apoptosis in DLD1 human colon cancer cells © 2008 Wiley-Liss, Inc.

A common modification of eukaryotic and bacterial tRNAs is isopentenylation of the adenosine at position 37, with the formation of isopentenyladenosine. N6-Isopentenyladenosine plays a major role in posttranscriptional processes, including the function of mammalian selenocysteine tRNA. This molecule seems to have metabolic effects that, for its relationships with isoprenoid metabolism and its direct biological activities, affects mammalian cell cytoskeleton, proliferation and apoptosis. In addition, preliminary clinical observation seems to indicate a possible use of N6-Isopentenyladenosine as anticancer drug.

Cannabinoids are a class of compounds that have the ability to activate two specific receptor subtypes, the cannabinoid CB1 and CB2 receptors. CB1 receptor is a G-protein-coupled receptor that is linked to the signal transduction pathways. The cumulative effects of this receptor have important implications in the control of cell survival and cell death having the potential to regulate tumor cell growth. In this connection, interest has been focused on factors such as sex steroid hormones, which regulate CB1 receptor expression. The aim of this study was to investigate the effects of 17beta-estradiol exposure on the CB1 receptor gene and its protein expression in human primary tumor colon cancer cell lines, such as DLD-1, HT-29 and one lymph node metastatic cell line, SW620.CB1 gene expression was determined using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in DLD-1, HT-29 and SW620 cells treated at different times and doses of 17beta-estradiol exposure. CB 1 protein expression was detected by Western immunoblot.17beta-estradiol induced CB1 gene expression in all the human colon cancer cells studied. The early induction of CB1 receptor mRNA in DLD-1 and SW620 cells was mediated by the estrogen receptor because the pure estrogen antagonist, ICI 182,780, was able to counteract this effect. Estrogenic induction of the CB1 receptor was also detectable at protein level in all cell types tested.The CB1 receptor can be considered an estrogen-responsive gene in DLD-1, HT-29 and SW620 cells. Up-regulation of CB1 expression by 17beta-estradiol is a further mechanism of estrogens to control colon cancer proliferation.

During the ageing process in rats hypercholesterolemia occurs in concert with full activation, lowered degradation rate and an unchanged level of the rate limiting cholesterol biosynthesis enzyme, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoAR). The molecular bases of the HMG-CoAR unchanged level and lowered degradation rate in aged rats is not clear. In fact no data are available during ageing, on transcription and degradation of HMG-CoAR, so well defined in adult animal. So, aim of this work was to measure mRNA levels of the enzyme and the level of the proteins of the regulatory complex responsible of the cholesterol metabolism. To complete the picture, the level of sterol regulatory element binding proteins (SREBPs), SREBP cleavage activating protein, and insulin-induced gene has been measured. The levels of other related proteins, whose transcription is SREBP dependent, that is low density lipoprotein receptor (LDLr) and Caveolin 1, have been also measured. The age-related reduced Insigs levels, joined to a reduced insulin sensitivity, could explain the decreased degradation rate of the HMG-CoAR and the increased active SREBP-2. The SREBP-2 in particular seems to be committed in multiple way to gene transcription. The obtained data represent a good contribution to explain the age-related hypercholesterolemia. J. Cell. Biochem. 98: 1044–1053, 2006. © 2006 Wiley-Liss, Inc.

Background The enzyme farnesyltransferase has emerged as an important target for anti-cancer therapies. Farnesyltransferase inhibitors have been introduced in clinical trials of subjects with colorectal cancer. We investigated Farnesyltransferase activity, beta-subunit Farnesyltransferase protein expression and its mRNA in patients with colorectal cancer and its relationship with clinicopathological features and K-ras mutation. Methods Farnesyltransferase activity was determined by Farnesyltransferase [3H] SPA enzyme assay. Beta-subunit Farnesyltransferase protein expression was investigated by Western blotting and its mRNA by reverse transcriptase-polymerase chain reaction. K-ras mutation was detected by polymerase chain reaction amplification and restriction enzyme analysis. Multiple linear regression analysis was used to analyse relationships among age, sex, site of tumour, Dukes' stage, histological differentiation, K-ras mutation and Farnesyltransferase activity in normal mucosa and cancer. Results The levels of Farnesyltransferase activity and beta-subunit Farnesyltransferase protein expression were significantly higher in cancer than in normal mucosa. Moreover, tumours located on the right side, with mucinous histological differentiation and with K-ras mutation showed higher levels of Farnesyltransferase activity. Conclusions Our findings suggest that Farnesyltransferase activity may be a potential marker of tumourigenicity. The differences in Farnesyltransferase activity in relation to histological grading, tumour location and K-ras mutation described here may constitute a starting point for investigating the causes of this variation within the large bowel.

Rimonabant (SR141716), a highly selective cannabinoid receptor antagonist, exerts along with its anti-obesity action, pleiotropic functions affecting a broad range of diseases, from obesity-related co-morbidities to drug dependence and cancer. Several studies suggested an anti-tumour activity of rimonabant in several in vitro and in vivo models. In this study, we compared the anti-proliferative effect of SR141716 in the human colon cancer cell line DLD-1 with oxaliplatin, one of the cytotoxic drugs currently used in the treatment of colorectal cancer. We show that SR141716 inhibits DLD-1 cell proliferation similarly to oxaliplatin and if administered in combination SR141716 potentiated the inhibitory effect caused by oxaliplatin. Assessment of drug interaction was performed calculating combination index that showed a strong synergistic effect between the two drugs added to cells in combination. Our findings suggest that the combined synergic effect of SR141716 and oxaliplatin improves the blocking of colon cancer cell proliferation. Therefore, this combination merits further explorations in preclinical and clinical settings.

BACKGROUND: Anandamide (AEA) is an endogenous agonist for cannabinoid receptor CB1-R and seems to be involved in the control of cancer growth. Polyamines are compounds that play an important role in cell proliferation and differentiation. Our aim was to investigate the effect of AEA on the polyamine levels (putrescine, spermidine and spermine) and cell growth of three human colon cancer cell lines, positive for CB1-R. MATERIALS AND METHODS: After AEA treatment of DLD-1, HT-29 and SW620 cells, polyamine analysis was performed by high-performance liquid chromatography (HPLC) and cell growth was measured by 3-(4,5 di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test. CB1 gene expression was determined using reverse transcription and polymerase chain reaction (RT-PCR). RESULTS: AEA significantly reduced polyamine levels and cell proliferation dose-dependently when the tested cell lines were exposed for 24 h and 48 h. This inhibitory effect was mediated by CB1-R, since SR 1411716A, a selective CB-1 receptor antagonist, was able to entirely antagonize the effect of AEA. CB1-R mRNA levels were enhanced after AEA treatment in DLD-1 cells, whereas no induction was found in HT-29 and SW620 cells. CONCLUSION: It appears that mechanisms by which AEA may affect growth of colon cancer cells involve a decrease in cell proliferation rate by reducing the polyamine levels.