Effect of recombinant interferon-alpha on bleomycin-induced chromosome damage in hamster cells

DNA and chromosome damage induced by bleomycin in mammalian cells: An update

Bleomycin (BLM) is an antibiotic isolated from Streptomyces verticillus. It has radiomimetic actions on DNA thus it has been widely used in clinical chemotherapy for the treatment of different types of cancer, including head and neck tumors, lymphomas, squamous-cell carcinomas and germ-cell tumors. Because of this, the study of BLM genotoxicity is of practical interest. This antibiotic is an S-independent clastogen and an agent that generates free radicals and induces single- and double-strand breaks in DNA. In the present review, we will summarize our current knowledge concerning the DNA and chromosome damage induced by BLM in mammalian cells, with emphasis on new developments published since 1991.

Cytogenetic effects of recombinant interferon-gamma on lymphocytes cultures from patients with non-small cell lung cancer

Therapeutic effects of human interferons (IFN) on malignancies and infectious diseases have been demonstrated in several clinical trials. The effects of IFN alone or combined with other treatment modalities (radiotherapy and chemotherapy) in lung cancer are under investigation. Experimental data suggest that some cytokines, such as IFN-alpha and IFN-gamma, exhibit cytogenetic properties in human normal lymphocytes from peripheral blood, but the mechanisms are not clear. The aim of the present study was to investigate the in vivo cytotoxic and cytostatic activity of IFN-gamma. Patients with certain cases of non-small cell lung cancer not eligible for chemotherapy or chemoradiotherapy were treated with thoracic radiotherapy. After tumor relapse, local treatment with instillations of IFN-gamma through the fiberoptic bronchoscope followed. To clarify the cytogenetic activity of IFN-gamma, sister chromatid exchange (SCE) and proliferation rate index (PRI) were evaluated in lymphocyte cultures from these patients' peripheral blood samples immediately after diagnosis (baseline), 30 days after radiotherapy, and after the fifth instillation of IFN-gamma. Our results show a decrease in SCE frequency and PRI values in lymphocytes after treatment with IFN-gamma, suggesting that IFN-gamma does not have cytotoxic activity but, in contrast, may induce repair mechanisms, as shown in earlier studies in other biologic models.

Effect of recombinant interferon-alpha on streptozotocin-induced chromosome aberrations and sister-chromatid exchanges in hamster cells

We assessed the effect of recombinant IFN-alpha-2a (rIFN-alpha-2a) on the induction of CAs and sister-chromatid exchanges (SCEs) by the methylating compound streptozotocin (STZ), in Chinese Hamster Ovary (CHO) cells. The cytokine was added to cell cultures 30 min before STZ and left in the culture medium until the end of the treatment. A statistically significant increase in the frequency of CAs and SCEs was observed following treatment with STZ alone (p < 0.05) compared to control, whereas treatments with rIFN-alpha-2a alone did not produce any significant increase of CAs or SCEs over the control values (p < 0.05). Moreover, rIFN-alpha-2a had a marked inhibitory effect on the frequency of STZ-induced CAs--both chromosome- and chromatid-type--(p < 0.05) but was unable to prevent SCEs induced by the antibiotic (p > 0.05). A decrease in the replication index (RI) was observed in the combined treatments compared with STZ alone-treated cultures, indicating inhibition of DNA synthesis. It is suggested that rIFN-alpha-2a exerts its protective action against the induction of CAs by STZ by stimulating DNA repair.

Effect of recombinant interferon-alpha on streptonigrin-induced chromosome aberrations and sister-chromatid exchanges in hamster cells

The effect of recombinant interferon-alpha-2a (rIFN-alpha-2a) on the induction of chromosomal aberrations (CAs) and sister-chromatid exchanges (SCEs) by the radiomimetic antibiotic streptonigrin (SN, 250 ng/ml, 20 min, 37 degrees C) in Chinese hamster ovary (CHO) cells was investigated. Recombinant IFN-alpha-2a (4500-45,000 IU/ml) was added to the cell cultures 30 min before SN and left in the culture medium until the end of SN treatment or until cell harvesting. A statistically significant increase in the frequency of CAs and SCEs was observed following treatment with SN (P < 0.05), whereas treatments with rIFN-alpha-2a alone did not produce any significant increase of CAs and SCEs over control values. Low rIFN-alpha-2a doses produced a reduction in the frequency of CAs and an increase in the yield of SCEs induced by SN, while high doses of the cytokine caused an increase in the yield of CAs and a reduction in the frequency of SCEs induced by the antibiotic. In addition, rIFN-alpha-2a caused a marked inhibition (around 50%) on the yield of SN-induced chromatid-type aberrations in the G(2) phase of the cell cycle. It is suggested that the inhibitory effect of rIFN-alpha-2a on the SN-induced chromosome damage is due to the stimulation of DNA synthesis and repair by the cytokine. On the other hand, our results give further support to our previous hypothesis that the induction of CAs and SCEs by SN is based on different mechanisms.