Non-homologous end joining pathway is the major route of protection against 4ß-hydroxywithanolide E-induced DNA damage in MCF-7 cells.

4ß-Hydroxywithanolide E is a bioactive withanolide extracted from Physalis peruviana. 4ß-Hydroxywithanolide E caused reactive oxygen species production and cell apoptosis in human breast cancer MCF-7 cells. We further found that 4ß-hydroxywithanolide E induced DNA damage and regulated the DNA damage signaling in MCF-7 cells. The DNA damage sensors and repair proteins act promptly to remove DNA lesions by 4ß-hydroxywithanolide E. The ataxia-telangiectasia mutated protein (ATM)-dependent DNA damage signaling pathway is involved in 4ß-hydroxywithanolide E-induced apoptosis of MCF-7 cells. Non-homologous end joining pathway, but not homologous recombination, is the major route of protection of MCF-7 cells against 4ß-hydroxywithanolide E-induced DNA damage. 4ß-Hydroxywithanolide E had no significant impact on the base excision repair pathway. In this study, we examined the 4ß-hydroxywithanolide E-induced DNA damage as a research tool in project investigating the DNA repair signaling in breast cancer cells. We also suggest that 4ß-hydroxywithanolide E assert its anti-tumor activity in carcinogenic progression and develop into a dietary chemopreventive agent.

Cyclopeptide alkaloids from Paliurus ramossisimus.

Seven zizyphine A-type cyclopeptide alkaloids were isolated from the roots of Paliurus ramossisimus by the combination of centrifugal partition chromatography and conventional separation methods. The novel structures of paliurines A-F (1-6) were characterized and established on the basis of MS and elaborate NMR spectral analyses. Terminal dipeptide stereochemistry was confirmed by correlation with the synthetic dipeptides via comparison of their (13)C NMR data.

Decrease in nucleophosmin/B23 mRNA and telomerase activity during indomethacin-induced apoptosis of gastric KATO-III cancer cells.

The mRNA expression of nucleophosmin/B23 in gastric cancers (T) and the matched adjacent "normal" gastric mucosa (N) obtained from patients without any preoperative treatment were determined. Telomerase activity was detected in tumor tissues from six of seven patients. Analysis of the adjacent "normal" gastric mucosa in the same patients revealed all seven were negative for telomerase activity. In comparing clinical data for all seven patients, the stages of cancer seemed to be associated with T/N nucleophosmin/B23 mRNA expression. Cancers of later stages seemed to have higher T/N nucleophosmin/B23 mRNA ratio. After 3-4 days of 1 mM indomethacin treatment about 60-85% of gastric cultured KATO III cancer cells exhibited the features with highly condensed nuclei and decrease in cell size. Concomitant with the increase in the percentage of KATO III cells exhibiting the morphological features of apoptosis, there was a decrease in the viability of cells as determined by exclusion of trypan blue. A decline in telomerase activity in indomethacin-treated versus untreated cells was observed over times (2-4 days). The steady-state level of nucleophosmin/B23 mRNA, as determined by the levels of radioactivity of the hybridizing bands also decreased during the indomethacin treatment. At some times after the removal of indomethacin, cell growth and telomerase activity resumed in little extent (approx. 60%). When nucleophosmin/B23 antisense oligonucleotide was included in the cell culture upon removal of indomethacin, virtually no recovery of cell growth and telomerase activity were observed.

Tandem duplications and large-scale deletions of mitochondrial DNA are early molecular events of human aging process.

Large-scale deletions and tandem duplications of mtDNA, which were originally identified in the patients with KSS or CPEO, have recently been found, although with lower abundance, in various tissues of aged individuals. By use of PCR techniques with back-to-back primers, we demonstrated for the first time that small tandem duplications occur in the D-loop of mtDNA in an age-dependent manner in human tissues. A total of 10 types of such tandem duplications were identified and confirmed by primer-shift PCR and DNA sequencing. Based on the sequence characteristics of the junction sites, we classified these small tandem duplications into 3 groups. Most of the tandem duplications were found to occur at hot spots containing poly C runs, and the number of C residues exhibited wide variations in type I, II, V, VI, VII, and VIII duplications. These observations suggest that these tandem duplications may be generated through similar recombination mechanisms. Among them, type I, II, III, IV and IX duplications were found to occur more frequently and abundantly in aging human tissues. They were not detectable in muscle, testis or skin tissues of young subjects or blood cells from subjects of any age. On the other hand, we also analyzed the samples for the aging-associated 4,977-bp and 7,436-bp mtDNA deletions. The results showed that these two deletions and some of the small tandem duplications could occur alone or in different combinations in human tissues in the aging process. From our data, no clear association between tandem duplications and large-scale deletions of mtDNA could be established. However, one common and important observation is that the incidence and abundance of some of the tandem duplications as well as the large-scale deletions were increased in an age-dependent manner. On the basis of these findings and data reported from this and other laboratories, we propose that tandem duplications and large-scale deletions of mtDNA are early molecular events of the human aging process.