Purpose: Recently, several studies reported a strong functional link betweenhistone deacetylases (HDAC) and the development of tumors of the large intestine. However, despite the importance of these molecules, comparably little is known on expressionpatterns and functions of specific HDAC isoforms in colorectal cancer. Experimental Design: We characterized class I HDAC isoform expression patterns in a cohort of 140 colorectal carcinomas by immunohistochemistry. In addition, effects of HDAC inhibition by valproic acid and suberoylanilide hydroxamic acid, and specific HDAC isoform knockdown by short interfering RNA, were investigated in a cell culture model. Results: We found class I HDACs highly expressed in a subset of colorectal carcinomas with positivity for HDAC1 in 36.4%, HDAC2 in 57.9%, and HDAC3 in 72.9% of cases. Expression was significantly enhanced in strongly proliferating (P = 0.002), dedifferentiated (P = 0.022) tumors. High HDAC expression levels implicated significantly reduced patient survival (P = 0.001), with HDAC2 expression being an independent survival prognosticator (hazard ratio, 2.6; P = 0.03). Short interfering RNA^based inhibition of HDAC1 and HDAC2 but not HDAC3 suppressed growth of colon cancer cells in vitro, although to a lesser extent than chemical HDAC inhibitors did. Conclusions: The strong prognostic impact of HDAC isoforms in colorectal cancer, the interactions of HDACs with tumor cell proliferation and differentiation in vivo, and our finding that HDACs are differentially expressed in colorectal tumors suggest that the evaluation of HDAC expression in clinical trials for HDAC inhibitors might help to identify a patient subgroup who will exceptionally profit from such a treatment.

BACKGROUNDThe human nuclear export protein chromosomal region maintenance/exportin 1/Xpo1 (CRM1) mediates the nuclear export of proteins and messenger RNAs and, thus, is an important regulator of subcellular distribution of key molecules. Whereas cell‐biologic studies have suggested a fundamental role for CRM1 in the regulation of mitosis, the expression of this protein in human tumor tissue has not been investigated to date.METHODSIn this study, the expression of CRM1 was analyzed in a cohort of 88 ovarian tumors and 12 ovarian cell lines for the first time to the authors' knowledge.RESULTSImmunohistochemistry revealed increased nuclear (52.7%) and cytoplasmic (56.8%) expression of CRM1 in 74 carcinomas compared with the expression revealed in borderline tumors and benign lesions. Similarly, CRM1 expression was increased in ovarian cancer cell lines compared with human ovarian surface epithelial cells. Cytoplasmic CRM1 expression was related significantly to advanced tumor stage (P = .043), poorly differentiated carcinomas (P = .011), and higher mitotic rate (P = .008). Nuclear CRM1 was associated significantly with cyclooxygenase‐2 (COX‐2) expression (P = .002) and poor overall survival (P = .01). Because it was demonstrated previously that blocking of CRM1 by leptomycin B (LMB) contributes to the inhibition of nuclear export, the authors used a set of mechanistic assays to study the effects of CRM1 inhibition in cancer cells. Treatment of OVCAR‐3 cells with LMB revealed a significant reduction of cell proliferation and increased apoptosis as well as suppressed interleukin‐1β‐induced COX‐2 expression.CONCLUSIONSThe current results indicated that CRM1 is expressed in a subpopulation of ovarian carcinomas with aggressive behavior and is related to poor patient outcome. A correlation also was demonstrated between CRM1 and COX‐2 expression in ovarian cancer tissue. Furthermore, the treatment of ovarian cancer cells with LMB revealed a reduction in COX‐2 expression. Therefore, the authors suggest that CRM1 may be an interesting biomarker for the assessment of patient prognosis and a molecular target for anticancer treatment. Cancer 2008. © 2008 American Cancer Society.

p-mTOR expression was associated with nuclear p-4EBP1 expression (P = 0.02), and was more frequent in tumors extending ouside the uterine corpus (P = 0.011). Nuclear p-4EBP1 expression was increased in carcinomas of poor differentiation (P = 0.012). In cultivated PTEN-deficient Ishikawa cells, in addition to an activation of AKT, a phosphorylation of mTOR and 4EBP1 was evident, while PTEN-wild type HEC-1A cells lacked AKT activation but revealed a reduced expression of p-mTOR and p-4EBP1. Rapamycin induced a growth reduction, which was clearly more pronounced in Ishikawa cells than in HEC-1A cells (P < 0.03) and could be observed for up to 6 days. CONCLUSISONS: Expression of mTOR and 4EBP1 characterize high-grade, high-stage endometrial adenocarcinomas and might be predictive markers of a response to rapamycin. Based on our results, we suggest that the expression of elements of the mTOR pathway in human tumor tissue should be further evaluated as a possible predictive marker in large-scale clinical studies as well as translational research protocols in clinical studies with mTOR inhibitors.

The human ELAV-like protein HuR is involved in the stabilization of the mRNAs of a group of genes implicated in the regulation of cellular growth, angiogenesis and rapid inflammatory response. HuR is a nuclear shuttling protein, translocating bound mRNAs from the nucleus to the cytoplasm. We have previously observed an increased expression of cyclooxygenase-2 (COX-2) in prostate cancer while cell culture studies have shown that HuR stabilizes the mRNA of COX-2. Based on these mechanistic data, we aimed to investigate the role of HuR in prostate cancer by a tissue-based analysis combined with functional evaluation using a cell culture approach. Investigating 104 primary prostate carcinomas by immunohistochemistry, we found HuR expression to be shifted from a nuclear staining in normal prostate glands to a cytoplasmic staining in carcinoma tissue (p<0.0001). Cytoplasmic HuR expression was significantly correlated with COX-2 expression (p=0.005). Loss of nuclear HuR expression was an indicator of earlier PSA-relapse both in univariate (p=0.04) and multivariate survival analysis (p=0.04). HuR inhibition by Leptomycin B reduced the inducibility of COX-2 in PC-3 prostate cancer cells. We found that the subcellular localization of HuR is deregulated in a subset of prostate carcinomas, and that this deregulation is linked to an altered expression of the tumorigenic COX-2 protein as well as to an adverse patient prognosis. Our results point to a potential prognostic role of HuR expression in prostate cancer diagnostics and propose HuR as a future therapeutic target in prostate cancer therapy.

BackgroundThe strong association between aberrant HDAC activity and the occurrence of cancer has led to the development of a variety of HDAC inhibitors (HDIs), which emerge as promising new targeted anticancer therapeutics.MethodsDue to the pivotal role of RelA/p65 in the tumorigenesis of pancreatic neoplasia we examined the expression of class I HDACs 1, 2 and 3 in a large cohort of human pancreatic carcinomas and correlated our findings with RelA/p65 expression status. Furthermore, we investigated the impact of the HDIs SAHA and VPA on RelA/p65 activity in pancreatic cancer cell culture models.ResultsClass I HDACs were strongly expressed in a subset of pancreatic adenocarcinomas and high expression was significantly correlated with increased nuclear translocation of RelA/p65 (p = 0.024). The link of HDAC activity and RelA/p65 in this tumor entity was confirmed in vitro, where RelA/p65 nuclear translocation as well as RelA/p65 DNA binding activity could be markedly diminished by HDI treatment.ConclusionThe RelA/p65 inhibitory effects of SAHA and VPA in vitro and the close relationship of class I HDACs and RelA/p65 in vivo suggest that treatment with HDIs could serve as a promising approach to suppress NF-κB activity which in turn may lead to enhanced apoptosis and chemosensitization of pancreatic cancers.