The natural antioxidant alpha-lipoic acid induces p27(Kip1)-dependent cell cycle arrest and apoptosis in MCF-7 human breast cancer cells.

Unlike normal cells, tumor cells survive in a specific redox environment where the elevated reactive oxygen species contribute to enhance cell proliferation and to suppress apoptosis. Alpha-lipoic acid, a naturally occurring reactive oxygen species scavenger, has been shown to possess anticancer activity, due to its ability to suppress proliferation and to induce apoptosis in different cancer cell lines. Since at the moment little information is available regarding the potential effects of alpha-lipoic acid on breast cancer, in the present study we addressed the question whether alpha-lipoic acid induces cell cycle arrest and apoptosis in the human breast cancer cell line MCF-7. Moreover, we investigated some molecular mechanisms which mediate alpha-lipoic acid actions, focusing on the role of the PI3-K/Akt signalling pathway. We observed that alpha-lipoic acid is able to scavenge reactive oxygen species in MCF-7 cells and that the reduction of reactive oxygen species is followed by cell growth arrest in the G1 phase of the cell cycle, via the specific inhibition of Akt pathway and the up-regulation of the cyclin-dependent kinase inhibitor p27(kip1), and by apoptosis, via changes of the ratio of the apoptotic-related protein Bax/Bcl-2. Thus, the anti-tumor activity of alpha-lipoic acid observed in MCF-7 cells further stresses the role of redox state in regulating cancer initiation and progression.

C/EBP beta gene inactivation causes both impaired and enhanced gene expression and inverse regulation of IL-12 p40 and p35 mRNAs in macrophages.

The transcription factor C/EBPbeta is believed to play a fundamental role in regulating activated macrophage functions. However, the molecular mechanisms and the target genes involved have been, so far, poorly characterized, partly due to the difficulty of reproducibly obtaining homogeneous and abundant primary macrophage populations. In this study, we describe the generation and characterization of immortalized macrophage-like cell lines from C/EBPbeta-deficient and wild-type mice. Using these cells, we were able to identify a number of genes involved in activated macrophage functions whose induction was affected in the C/EBPbeta(-/-) cells. IFN-gamma/LPS-dependent induction of IL-6, IL-1beta, TNF-alpha, inducible NO synthase, and plasminogen activator inhibitor-1 mRNAs was variably impaired, while IL-12 p40, RANTES and macrophage inflammatory protein-1beta mRNAs were up-regulated in the absence of C/EBPbeta. The differential mRNA expression correlated with differential transcription levels of the corresponding genes, and was in most cases confirmed in primary macrophage populations. Moreover, in sharp contrast to the enhanced induction of IL-12 p40 mRNA, C/EBPbeta(-/-) primary macrophages derived from both the bone marrow and the peritoneal cavity displayed totally defective expression of IL-12 p35 mRNA. Therefore, the IL-12 p35 gene represents a novel obligatory target for C/EBPbeta in macrophages and this may explain the defective production of bioactive IL-12 and the impaired Th1 responses of C/EBPbeta-deficient mice to Candida albicans infection observed in previous work.