Acadesine Triggers Non-apoptotic Death in Tumor Cells.

We studied the cytotoxicity of acadesine (5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside) for tumor and normal cells of various species and tissue origin. In tumor cells, acadesine triggered non-apoptotic death; the potency of the compound to normal cells was substantially lower. Acadesine was toxic for tumor cells with multidrug resistant phenotypes caused by the transmembrane transporter Р-glycoprotein or lack of proapoptotic p53. Activity of adenosine receptors was required for acadesine-induced cell death, whereas functioning of АМР-dependent protein kinase was not required. A more pronounced cytotoxicity for tumor cells, as well as the non-canonical death mechanism(s), makes acadesine a promising candidate for antitumor therapy.

Expression of peroxiredoxin 1, 2, 3, and 6 genes in cancer cells during drug resistance formation.

We studied the expression of peroxiredoxin genes (PRDX1, PRDX2, PRDX3, and PRDX6) in human erythroleukemia K652, human breast carcinoma MCF-7, and human ovarian carcinoma SKOV-3 cells during cisplatin resistance development. It was found that drug resistance formation was accompanied by a significant increase in the expression of PRDX1, PRDX2, PRDX3, PRDX6 genes in all cancer cell strains, which confirms the important contribution of redox-dependent mechanisms into the development of cisplatin resistance of cancer cells.

Cellular expression of INK4a gene in cells of bladder cancer associated with human papilloma virus-16.

Hyperexpression of p16(INK4a) protein is an early marker of cervical cancer. Hyperexpression of INK4a gene encoding this protein at the level of mRNA and p16(INK4a) was detected in tumor cells of some patients with bladder cancer associated with human papilloma virus-16. However, in contrast to cervical cancer, this phenomenon in urothelial carcinomas does not correlate with expression of human papilloma virus-16 oncogenes E6 and E7.

[Are human papillomaviruses responsible for the occurrence of bladder cancer].

A female patient with recurrent bladder cancer underwent complex examination. The primary tumor removed in 2004 showed human papillomavirus (HPV) 16 DNA, mRNA corresponding to HPV16 oncogene E7, as well as HPV16 protein E7. The patient is a smoker who has been working at a chemical factory for over 20 years. During tumor recurrence in 2009, there was no DNA of high-risk HPV types in the cancer cells. HPV16 E7protein and cellular p 16(INK4alpha), an indicator of HPV-induced carcinogenesis, were not found. Colposcopy revealed no precancerous changes in the epithelium of the cervix uteri. The cervical epitheliocytes contained no high-risk HPV DNA, E7 and p16(INK4alpha) proteins. It seems expedient to continue in vitro studies of the possible role of HPV in urothelial carcinogenesis on an experimental model.

[Mitochondrial mechanisms of apoptosis in response to DNA damage].

Integrity of genome is a prerequisite for cell viability. Therefore, targeted damage of DNA structure is considered the key approach to the induction of cell death. Among the plethora of death execution programs the mitochondrial events are of the utmost importance. However, the epigemetic activation of defense mechanisms in response to DNA damage limit cell death. This review analyses the outcome of the genotoxic stress (i.e., cell death versus survival) as a balance of pro- and anti-apoptotic signaling. Practically speaking, the combinations of DNA damaging agents with the inhibitors of anti-apoptosis would increase the efficacy of anticancer therapy.

[Why does iron abrogate the cytotoxic effect of S-nitrosothiols on human and animal cultured cells?].

It was found that dinitrosyl iron complexes (DNIC) with thiol-containing ligands (cysteine or glutathione) of concentrations up to 1 mM produce no cytotoxic effect on cultured cells from human milk gland carcinoma (MCF-7). The cytotoxic action on MCF-7 cells was produced by S-nitrosocysteine: at a concentration of 1 mM, it induced the death of 50% cells. A more stable S-nitrosothiol, S-nitrosoglutathione, did not produce any cytotoxic effect at the same concentration. It is assumed that the negative action of nitrosocysteine is due to its rapid degradation, which results in the accumulation of large amounts of free NO molecules followed by their oxidation by superoxide ions to peroxynitrite, an efficient inhibitor of metabolic processes. These processes seem to be not characteristic of the more stable S-nitrosoglutathione. The cytotoxic effect of nitrosocysteine was completlly abrogated by the addition of 0.2 mM ferrous citrate complex to the medium. When S-nitrosoglutathione NO (0.5 mM) or S-nitrosoglutathione (0.5 mM) + Fe(2+)-citrate (0.2 mM) were added to the medium, protein-bound dinitrosyl iron complexes formed with the involvement of endogenous or exogenous iron were detected in cells. The amount of the complexes in the presence of exogenous iron increased four times, reaching the value of 1.6 nmole/5 x 10(6) cells. Therefore, it was proposed that the blockade of the cytotoxic action of S-nitrosoglutathione by iron complexes is due to Cys-NO transformation of S-nitrosocysteine into dinitrosyl iron complexes. The high stability of these complexes ensures only a gradual accumulation of nitric oxide in cells.