The effects of two polyphenols, chebulinic acid and tellimagrandin I, on DNA strand breaks mediated by H2O2/Cu(Ⅱ), hydroquinone (HQ)/Cu(Ⅱ) and H2O2/Fe(Ⅱ) in pBR322 plasmid DNA and genomic DNA of cultured MRC-5 human embryo lung fibroblasts were examined. The results demonstrated that chebulinic acid and tellimagrandin I obviously inhibited HQ/Cu(Ⅱ)-and H2O2/Cu(Ⅱ)-mediated pBR322 DNA strand breaks. When MRC-5 cells were treated with HQ/Cu(Ⅱ), the presence of chebulinic acid or tellimagrandin I inhibited HQ/Cu(Ⅱ)-mediated double strand breaks of genomic DNA. The presence of chebulinic acid or tellimagrandin I did not affect the H2O2-and HQ-mediated reduction of Cu(Ⅱ) to Cu(I). Both polyphenols could slightly inhibit H2O2/Fe(Ⅱ)-mediated plasmid DNA strand break at the lower concentration (1-10 lM), but potentiate the DNA strand break at the higher concentration (over 50 lM). These results demonstrated that chebulinic acid and tellimagrandin I possessed antioxidant action in certain conditions and exerted prooxidant action on DNA strand breaks in other conditions.

Tellimagrandin I and chebulinic acid, two hydrolysable tannins, have been shown to exert anti-tumor properties. Dysfunctional gap junctional communication (GJIC) has been recognized as being involved in carcinogenesis. The human cervical carcinoma HeLa cells have been reported to be deficient in functional GJIC. In present study, we investigated whether tellimagrandin I and chebulinic acid might restore functional GJIC in HeLa cells. Both compounds could inhibit the growth of HeLa cells. Either Lucifer yellow transfer assay or calcein transfer assay demonstrated that tellimagrandin I improved GJIC in HeLa cells while chebulinic acid showed no effect on GJIC. The GJIC enhancement by tellimagrandin I occurred along with an increase of Cx43 gene expression atmRNAand protein levels. Exposure to tellimagrandin I also led to inhibition of proliferation and anchorage-independent growth of HeLa cells. In addition, tellimagrandin I decreased the percentage of cells in the G0/G1 and G2/M phases coinciding with an increase in the percentage of cells in the S phase. The accumulation of cells in S phase was coupled with a decreased expression of cyclin A that was critical to the progression of S phase. These results suggested that restoring GJIC might be one explanation for tellimagrandin I antitumor effects, whereas chebulinic acid exerted antitumor action through other pathways.

Methyl protodioscin is a furostanol bisglycoside with antitumor properties. The present study investigated its effects on human chronic myelogenous leukemia K562 cells. Cell cycle analysis showed that methyl protodioscin caused distinct G2/M arrest, with the appearance of polyploidy population. The levels of cyclin B1 decreased, whereas Cdc2 kept at a steady level. Subsequent apoptosis after G2/M blockage was demonstrated through DNA fragmentation and the annexin V staining assay. Methyl protodioscin induced a biphasic alteration (i.e. an early hyperpolarization, followed by depolarization) in mitochondrial membrane potential of K562 cells. The transient decline of intracellular Ca2C concentration was observed at early stage. The generation of reactive oxygen species was also detected. The anti-apoptotic Bcl-xL transiently increased and then decreased. And the pro-apoptotic Bax was markedly up-regulated. Taken together, these data demonstrated that methyl protodioscin inhibits K562 cell proliferation via G2/M arrest and apoptosis, with mitochondrial hyperpolarization and the disruption of Ca2C homeostasis playing important roles.

A novel human gene full-length cDNA sequence-TSARG2 was identified from a human testis cDNA library using the SRG2 gene (GenBank Accession No. AF395083), which was significantly up-regulated in cryptorchidism, as an electronic probe. TSARG2 was 1223 bp in length. The putative protein encoded by this gene was 305 amino acids with a theoretical molecular weight of 34,751 and isoelectric point of 9.85. The sequence shared no significant homology with any known protein in databases except SRG2. Northern blot analysis revealed that 1.7 kb TSARG2 transcript was detected selectively in human testis. Furthermore, results of in situ hybridization assay confirmed that TSARG2 was expressed in seminiferous tubules, more precisely in spermatogonia and spermatocyte. No mutation was found by PCR-SSCP in 122 cases of azoospermia, severe oligzoospermia, and cryptorchidism. The green fluorescence produced by pEGFP-C1/TSARG2 was detected on the nucleus of COS7 cells after 24 h post-transfection. The pcDNA3.1())/TSARG2 plasmid was constructed and introduced into MCF7 cells by liposome transfection. TSARG2 can accelerate MCF7 cells to traverse the S-phase and enter the G2-phase compared with the control without transfection of TSARG2, which suggested that this gene plays an important role in the development of cryptorchid testis and is a testis-specific apoptosis candidate oncogene.