Human interferon and cell growth inhibition. VII. Reversibility of interferon activities

Increased oxidative stress in dimethylnitrosamine-induced liver fibrosis in the rat: effect of N-acetylcysteine and interferon-alpha

Oxidative stress may represent a common link between chronic liver damage and hepatic fibrosis. Antioxidants and interferon seem to protect against hepatic stellate cell (HSC) activation and liver fibrosis. This study evaluated (1) the effect of the profibrotic agent dimethylnitrosamine (DMN) on the hepatic oxidative balance in the rat; (2) the role played by the antioxidant agent N-acetylcysteine (NAC); and (3) the antifibrotic effects of two different types of interferon-alpha: recombinant alpha-2b (rIFN-alpha) and leukocyte alpha (LeIFN-alpha). Five groups of rats received: (1) saline; (2) DMN; (3) DMN + NAC; (4) DMN + rIFN-alpha; and (5) DMN + LeIFN-alpha. Oxidative balance was evaluated by hepatic glutathione, TBARs, protein carbonyl, and sulfhydryl determination. Fibrosis was determined by hepatic hydroxyproline content and fibronectin (FN) staining (immunohistochemistry). DMN rats showed a diffuse FN deposition, an impaired oxidative balance, and higher hepatic hydroxyproline levels compared to that of controls. NAC administration significantly reduced FN deposition, increased hepatic glutathione, and decreased TBARs and protein carbonyls. Administration of IFN-alpha exerted different effects according to the type used. Both IFNs decreased FN deposition; however, LeIFN-alpha significantly improved histology and oxidative parameters compared to those of untreated DMN and rats treated with rIFN-alpha. This study shows the role of free radicals in this model of hepatic fibrosis; the protective effect of NAC against liver fibrosis; and the antifibrotic effect exerted by IFN-alpha (particularly LeIFN-alpha) independent of its antiviral activity.

Impaired angiogenic balance and suppression of tumorigenicity in HeLa cells chronically exposed to interferon-alpha

We have previously reported that IFNalpha-chronic treatment for 41 days induced a partial phenotype reversion on HeLa cells along with a down-regulation of HPV18 mRNA levels. However, tumorigenicity of these cells in nude mice was unchanged. Interestingly, after 1 year of IFNalpha-chronic exposition, HeLa cells failed to induce s.c. tumors when injected into nude mice. In such experimental conditions both HPV18 DNA integration pattern and viral DNA copy number present in HeLa cells remained intact in the nontumorigenic phenotype cells. As result of the treatment with IFNalpha, HeLa cells rendered more resistant to lysis mediated by activated natural killer cells in vitro. Furthermore, IFNalpha-chronic treatment was able to induce VEGF and decrease bFGF mRNA expression, suggesting a potential effect on the angiogenic behavior of these tumoral cells. Thus, long-term treatment of HeLa cells with IFNalpha can accomplish a reversion of the malignant phenotype by a sequential multistep mechanism, in which the antiangiogenic effect of IFNalpha could be one of the contributing events.

Partial phenotypic reversion of HeLa cells by long-term interferon-alpha treatment

Human papillomaviruses (HPV) are associated with malignant cervical neoplasia. Several HPV-related diseases have been shown to be sensitive to interferon (IFN) treatment. HeLa cells contain and express the HPV type 18 genome and were used as a model for the evaluation of the viral expression regulation and the effect on the malignant phenotype during IFN treatment. Cells were treated continuously with 200 IU/ml IFN-alpha 2b or natural leukocyte INF-alpha for six passages (42 days). Some IFN-induced changes were observed: decrease of HPV-18 mRNA expression, changes of cell morphology, and reduction of clonogenicity in soft agar. Tumorigenicity in nude mice was not modified. Other targets of the IFN system were analyzed, and an increase of the 2',5'-oligoadenylate synthetase mRNA level and a down-regulation of type I IFN receptor were found. These results demonstrate that long-term IFN-alpha treatment induces a partial phenotypic reversion of HeLa cells to a more differentiated stage were down-regulation of HPV-18 expression could play a central role. It therefore confirms that the IFN-alpha treatment may be therapeutically useful in cervix cancer produced by HPV-18.