Genetic and epigenetic marker-based DNA test of stool is a promising approach for colorectal cancer screening.

Colorectal cancer (CRC) is one of the most common malignancies and leading cause of cancer-related deaths in the world.1 However, it may be treated effectively by surgical removal of the cancerous tissue if detected at early stages. Conventional tools for screening CRC are either invasive or inaccurate. Therefore, there is an urgent need to develop a reliable screening tools for CRC to significantly reduce its morbidity. In this regard, a novel DNA markers-based detection in stool is emerging as a promising approach.

Cyclic induction of senescence with intermittent AZT treatment accelerates both apoptosis and telomere loss.

BACKGROUND: 3'-azido-2',3'-dideoxythymidine (AZT) is phosphorylated intracellularly to 3'-azido-3'-deoxythymidine-5'-triphosphate (AZT-TP), which is incorporated into telomeric DNA, thereby blocking chain elongation. AZT is also known to inhibit reverse transcriptase, as well as other cellular enzymes including DNA polymerase gamma, thymidine kinase, and telomerase. METHODS: We induced cancer cell senescence by treating MCF-7 cells with AZT in dosages of IC10 and IC20 for an extended period (about 120 population doublings (PD)). We then investigated the sequential changes in cellular growth, expression of telomerase subunits and transcription factors (c-Myc, Mad1), telomerase activity and telomere length. RESULTS: Senescence, apoptosis, growth delay, inhibition of telomerase activity and shortening of telomere length were all observed in a dose- and time-dependent manner. After the onset of senescence, the apoptosis rate increased slowly during early PDs. In contrast to senescence, the apoptotic rate showed little change after AZT removal, while it increased suddenly and significantly in a dose-dependent manner upon the second introduction of AZT. Continuous shortening of the telomeric length was observed with AZT, and, upon re-exposure to AZT, shortening of the telomere occurred more rapidly than with first exposure. Of the telomerase subunits, telomerase reverse transcriptase (hTERT) and c-Myc were the first to show a reduction in activity after AZT treatment, followed by changes in hTER , Mad1 and hTEP-1. CONCLUSION: Cyclic treatment with AZT initially suppressed hTERT and c-Myc, followed by suppression of hTER, Mad1 and hTEP-1. Furthermore, the treatment accelerated both telomere loss and apoptosis, even when administered at a senescence-inducing dosage level.

Attenuation of telomerase activity by hammerhead ribozyme targeting human telomerase RNA induces growth retardation and apoptosis in human breast tumor cells.

Ribozyme possesses specific endoribonuclease activity and catalyzes the hydrolysis of specific phosphodiester bonds, which results in the cleavage of target RNA sequences. Here, we evaluated the ability of hammerhead ribozymes targeting human telomerase RNA (hTR) to inhibit the catalytic activity of telomerase and the proliferation of cancer cells. Hammerhead ribozymes were designed against 7 NUX sequences located in open loops of the hTR secondary structure. We verified the ribozyme specificity by in vitro cleavage assay by using a synthetic RNA substrate. Subsequently, we introduced ribozyme expression vector into human breast tumor MCF-7 cells and assessed the biologic effects of ribozyme. Hammerhead ribozyme R1 targeting the template region of hTR efficiently cleaved hTR in vitro, and stable transfectants of this ribozyme induced the degradation of target hTR RNA and attenuated telomerase activity in MCF-7 cells. Moreover, the ribozyme R1 transfectant displayed a significant telomere shortening and a lower proliferation rate than parental cells. Clones with reduced proliferation capacity showed enlarged senescence-like shapes or highly differentiated dendritic morphologies of apoptosis. In conclusion, the inhibition of telomerase activity by hammerhead ribozyme targeting the template region of the hTR presents a promising strategy for inhibiting the growth of human breast cancer cells.

Genome-scale analysis of resveratrol-induced gene expression profile in human ovarian cancer cells using a cDNA microarray.

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a natural compound found in large quantities, most notably in grapes and red wine, which has been shown to have anti-inflammatory, chemopreventive and anti-angiogenic effects. We examined whether resveratrol has any effect on growth and gene expression in the human ovarian cancer PA-1 cells. We show that resveratrol inhibits cell growth and induces apoptosis in PA-1 human ovarian cancer cells. We also investigated the effect of resveratrol on changes of global gene expression during resveratrol-induced growth inhibition and apoptosis in PA-1 cells using a human cDNA microarray with 7,448 sequence-verified clones. Out of the 7,448 genes screened, 118 genes were founded to be affected in their expression levels by more than 2-fold after 24-h treatment with 50 micro M resveratrol. Resveratrol treatment of PA-1 cells at the final concentration of 50 micro M for 6, 12, 24 and 48 h and gene expression patterns were analyzed by microarray. Clustering of the genes modulated more than 2-fold at three of the above times points divided the genes into 2 groups. Within these groups, there were specific subgroups of genes whose expressions were substantially changed at the specified time points. One of the most highly up-regulated genes found in this study was NAD(P)H quinone oxidoreductase 1(NQO-1), which has recently been shown to be involved in p53 regulation. Although the precise roles of genes whose expression levels were found to fluctuate after resveratrol treatment remain to be elucidated, we hope that the new view of gene expression in human ovarian cancer cells following resveratrol exposure, as offered by this study, provides clues for the mechanism of resveratrol action.