Citations

Abstract It is well known that the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) acts synergistically with the DNA methyltransferase (DNMT) inhibitor 5-aza-2′-deoxycytidine (ADC) to reactivate DNA methylation-silenced genes. Moreover, in several studies, TSA was capable of inducing DNA demethylation even in the absence of ADC. Here we describe a mechanism by which HDAC inhibitors affect DNA methylation through their regulation on DNMT3B, a methyltransferase responsible for de novo DNA methylation. Using quantitative real-time PCR and Western blot analysis, we show that TSA down-regulates DNMT3B mRNA and protein expression in human endometrial cancer cells. This decrease in DNMT3B mRNA results in a significant reduction in de novo methylation activities. Further experiments indicated that TSA decreases DNMT3B mRNA stability and reduces its half-life from ∼4 to 2.5 hours. We established that protein synthesis is required for posttranscriptional regulation, suggesting the involvement of an RNase and/or key mRNA stabilization factor(s) controlling the DNMT3B mRNA stability. Therefore, TSA may not only modify histone acetylation, but also potentially alter DNA methylation. Since the HDAC inhibitors are frequently used in epigenetic studies and are considered to be promising anticancer drugs, these new findings will have implications in both laboratory and clinical settings.

Abstract Prostate cancer is the most frequent non–skin cancer in men. Although the mechanisms involved in the progression of prostate cancer are not entirely understood, androgen receptor has been shown to play an important role. Androgen receptor is expressed in both early and late-stage prostate cancer. Also, androgen-regulated pathways are thought to be active as evidenced by elevated levels of prostate-specific antigen (PSA). In addition, several androgen receptor coactivators and cytokines are involved in prostate cancer progression. In this regard, we have shown previously that the coactivator p300 plays a major role in the androgen-independent activation of PSA by interleukin 6 (IL-6), a cytokine involved in late-stage prostate cancer. In this study, we investigated the role of p300 and its homologue CREB-binding protein in prostate cancer cells treated chronically with IL-6. We found that p300 but not CREB-binding protein induced activation of PSA in these cells and that the histone acetyltransferase activity of p300 was critical. This effect was independent of the presence of androgens or antiandrogens. Moreover, we found markedly reduced levels of androgen receptor in these cells and p300 transfection did not affect those levels, suggesting that the p300 effect on PSA could be bypassing the androgen receptor. Transfection with exogenous androgen receptor showed minimal response of PSA to androgens but higher response to p300. We found similar effects of p300 on the androgen response element III, which mediates the androgen receptor–dependent activation of PSA. Finally, we showed that p300 alone regulates expression of the endogenous PSA gene in the IL-6–treated cells. These findings reveal a new insight in the progression of prostate cancer, suggesting that coactivators, such as p300, play more important roles in late-stage prostate cancer, and could regulate androgen-dependent genes in the absence or with very low levels of androgen receptor.

Abstract Recent studies using glycogen synthase kinase-3β (GSK-3β)–deficient mouse embryonic fibroblasts suggest that GSK-3β positively regulates nuclear factor κB (NFκB)–mediated gene transcription. Because NFκB is suggested to participate in cell proliferation and survival pathways in pancreatic cancer, we investigated the role of GSK-3β in regulating these cellular processes. Herein, we show that pancreatic cancer cells contain a pool of active GSK-3β and that pharmacologic inhibition of GSK-3 kinase activity using small molecule inhibitors or genetic depletion of GSK-3β by RNA interference leads to decreased cancer cell proliferation and survival. Mechanistically, we show that GSK-3β influences NFκB-mediated gene transcription at a point distal to the Iκ kinase complex, as only ectopic expression of the NFκB subunits p65/p50, but not an Iκ kinase β constitutively active mutant, could rescue the decreased cellular proliferation and survival associated with GSK-3β inhibition. Taken together, our results simultaneously identify a previously unrecognized role for GSK-3β in cancer cell survival and proliferation and suggest GSK-3β as a potential therapeutic target in the treatment of pancreatic cancer.

ABSTRACTOBJECTIVE:To describe the quality of life (QOL) over time for adults with newly diagnosed high-grade gliomas and to examine the relationship between QOL and outcome data collected in three prospective cooperative group clinical trials.METHODS:The QOL study was a companion protocol for three Phase II high-grade glioma protocols. Five self-administered forms were completed by patients to assess QOL at study entry, 2 months, and 4 months after enrollment.RESULTS:QOL data were available for baseline, first, and second subsequent follow-up evaluations for 89%, 71%, and 69% of patients, respectively. A significant proportion of patients (47.1%) experienced impaired QOL (QOL ≤ 50) in at least one measure at subsequent evaluations, whereas most patients (88%) with impaired QOL at baseline continued to have impaired QOL at subsequent evaluations. On multivariable analyses, baseline QOL measures were predictive of QOL at the time of follow-up. In addition, patients who underwent a gross total resection were much less likely to have impaired QOL (P = 0.006), were less likely to experience worsening depression (P = 0.0008), and were more likely to have improved QOL (P = 0.003) at their first follow-up evaluation. Changes in QOL measures over time were not found to be associated with survival in multivariable analyses that adjusted for known prognostic variables; variables that were independently associated with improved survival were better performance status (P < 0.001), younger age (P < 0.001), and greater extent of resection (P < 0.001).CONCLUSION:Baseline QOL was predictive of QOL over time. Gross total resection was associated with longer survival and improved QOL over time for patients with high-grade gliomas.

AbstractWhile pancreaticoduodenectomy is today performed with an operative mortality of <5%, the incidence of significant operative morbidity remains at least 25%. Albeit rarely, completion pancreatectomy during the early postoperative period may be required to manage uncontrolled pancreatic anastomotic leaks. From 1964 to 1988, pancreaticoduodenectomy was performed on 479 patients at our institution, 178 (37%) of whom required re‐operation in the early postoperative period. Of these, 11 (6%) patients underwent completion pancreatectomy at a mean interval of 18 days following Whipple resection. The indications prompting re‐operation included a suspected pancreatic leak (n=8), intra‐abdominal hemorrhage (n=2), and pancreaticocutaneous fistula (n=1). Operative findings necessitating completion pancreatectomy included pancreatic anastomotic dehiscence with severe surrounding inflammation/necrosis prohibiting reanastomosis or repair (n=10) and necrotizing pancreatitis with uncontrolled hemorrhage (1). Seven (64%) of these 11 patients died postoperatively of sepsis and multiple organ failure. The mean hospital stay in the 4 surviving patients was 46 days (range, 26 to 53 days). These 4 patients survived for a mean period of 24 months following hospital dismissal.