Pax5 Re-expression in H460 Cells Treated with the Combination of Demethylating Agent and Histone Deacetylase Inhibitor is Associated with the Enhancement of P53 Binding to Pax5 Promoter Region.

BACKGROUND: The epigenetic combinations of DNA demethylating agents and histone deacetylase (HDAC) inhibitors have demonstrated clinical benefits for non-small cell lung cancer (NSCLC) treatment, however, there are few studies uncovering the underlying molecular mechanism of the combinations. Our previous study showed that DNA demethylating agent Azacitidine (Aza) demethylated CpG sites in paired box gene 5 (pax5) promoter region, but did not induce pax5 mRNA or protein expression. METHODS: In this study we used epigenetic combination of Aza and HDAC inhibitor Vorinostat (SAHA) to treat NSCLC cells and to elucidate the underlying molecular mechanism. We treated pax5- silenced NSCLC H460 cells with Aza+SAHA combination at sub-toxic concentration and detected the re-expression of pax5 mNRA and protein. RESULTS: The results showed demethylation of CpG sites in pax5 promoter region by Aza treatment and increased DNA accessibility for protein binding by SAHA treatment. The combination of Aza+SAHA significantly increased p53 protein binding to DNA in pax5 promoter region (p<0.01). More efficient binding of the transcription factor p53 to pax5 promoter region is likely because SAHA increased accessibility of the chromatin conformation and Aza-demethylated DNA was more permissive, allowing transcription factors to bind. CONCLUSION: Our study not only explained an underlying mechanism, that pax5 re-expression was induced by Aza+SAHA combination in H460 cells via p53, but also demonstrated a pattern showing that the combination of demethylating agent and HDAC inhibitor can re-activate tumor suppressor gene (TSG) which is associated with the enhancement of transcription factors binding to the promoter region of the TSG.

Randomized study of gefitinib versus pemetrexed as maintenance treatment in patients with advanced glandular non-small cell lung cancer.

Gefitinib was compared with pemetrexed as maintenance therapy in Patients with Advanced Glandular Non-small Cell Lung Cancer, mainly regarding clinical effect and side effect. A randomized trial of pemetrexed as study group (500 mg/m(2), dl) versus gefitinib as the control group [250 mg on night 1, 250 mg on morning 2 (every day)] was conducted in 188 patients, 94 cases in each group with a therapy cycle of 21 days. In addition, the study group was also treated with folic acid, vitB12 and dexamethasone. Therapeutic effects and adverse reactions of the two groups were compared. Patients of two groups completed four cycles of chemotherapy mostly, and there was no complete remission (CR) case. The median-cycle of chemotherapy was 2 for the study group, and partial response (PR), stable disease (SD), progressive disease (PD) were observed in 28 (29.8%), 34 (36.2%), 32 (34.0%) cases respectively. The median-cycle was 3 for the control group, PR, SD and PD were observed in 17 (18.1%), 23 (24.5%), 54 (57.4%) cases respectively. The effective rates were 29.8% and 18.1% for pemetrexed (28 cases) and gefitinib (17 cases) respectively (P > 0.05). However, there was a statistically significant difference in disease control rates between the 2 groups (65.0% vs 42.6%; P < 0.05). Adverse reactions occurred in two groups were mainly mild adverse reactions of 1-2 degree, without renal failure. The study group and control group had three and five cases of mild infection respectively, without statistically significant difference. There was no significant difference in the incidence rate of rash and alopecia between the two groups (P > 0.05). However, the number of cases with neutropenia, anemia, thrombocytopenia, gastrointestinal reactions and fatigue in the study group was lower than that of the control group, with a statistically significant difference (P < 0.05). Considering the disease control rate and the tolerance of patients with advanced NSCLC, pemetrexed is strongly recommended to be used in clinical.