Expression profiling of sodium butyrate (NaB)-treated cells: identification of regulation of genes related to cytokine signaling and cancer metastasis by NaB.

Histone deacetylase (HDAC) inhibitors induce growth arrest and apoptosis in a variety of human cancer cells. Sodium butyrate (NaB), a short chain fatty acid, is a HDAC inhibitor and is produced in the colonic lumen as a consequence of microbial degradation of dietary fibers. In order to dissect out the mechanism of NaB-induced growth inhibition of cancer cells, we carried out expression profiling of a human lung carcinoma cell line (H460) treated with NaB using a cDNA microarray. Of the total 1728 genes analysed, there were 32 genes with a mean expression value of 2.0-fold and higher and 66 genes with a mean expression value 3.0-fold and lower in NaB-treated cells. For a few selected genes, we demonstrate that their expression pattern by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis is matching with the results obtained by microarray analysis. Closer view at the expression profile of NaB-treated cells revealed the downregulation of a total of 16 genes associated with cytokine signaling, in particular, interferon gamma (IFNgamma) pathway. In good correlation, NaB-pretreated cells failed to induce interferon regulatory factor 1, an INFgamma target gene, efficiently upon IFNgamma addition. These results suggest that NaB inhibits proinflammatory cytokine signaling pathway, thus providing proof of mechanism for its anti-inflammatory activity. We also found that NaB induced three genes, which are known metastatic suppressors, and downregulated 11 genes, which have been shown to promote metastasis. Upregulation of metastatic suppressor Kangai 1 (KAI1) by NaB in a time-dependent manner was confirmed by RT-PCR analysis. The differential regulation of metastasis-associated genes by NaB provides explanation for the anti-invasive properties of NaB. Therefore, our study presents new evidence for pathways regulated by NaB, thus providing evidence for the mechanism behind anti-inflammatory and antimetastatic activities of NaB.

p73 beta-expressing recombinant adenovirus: a potential anticancer agent.

Tumor suppressor p53-based gene therapy strategy is ineffective in certain conditions. p73, a p53 homologue, could be a potential alternative gene therapy agent as it has been found to be an important determinant of chemosensitivity in cancer cells. Previously, we have reported the generation of a replication-deficient adenovirus expressing p73 beta (Ad-p73). In this study, we evaluated the therapeutic potential of Ad-p73 against a panel of cancer cells (n=12) of different tissue origin. Ad-p73 infected all the cell lines tested very efficiently resulting in several-fold increase in p73 beta levels, which is also functional as it activated the known target gene p21(WAF1/CIP1). Infection with Ad-p73 resulted in potent cytotoxicity in all the cell lines tested. The mechanism of p73-induced cytotoxicity in these cell lines is found to be due to a combination of cell cycle arrest and induction of apoptosis. In addition, exogenous overexpression of p73 by Ad-p73 infection increased the chemosensitivity of cancer cells by many fold to commonly used drug adriamycin. Moreover, Ad-p73 is more efficient than Ad-p53 in enhancing the chemosensitivity of mutant p53 harboring cells. Furthermore, Ad-p73 infection did not induce apoptosis in human normal lung fibroblasts (HEL 299) and human immortalized keratinocytes (HaCaT). These results suggest that Ad-p73 is a potent cytotoxic agent specifically against cancer cells and could be developed as a cancer gene therapy agent either alone or in combination with chemotherapeutic agents.