BRAF mutation in sporadic colorectal cancer and Lynch syndrome.

The aim of the study was to detect mutations of BRAF oncogene in colorectal cancer and to use this information to identify Lynch syndrome patients. Consecutive cases of primary colorectal cancer (n = 137) were analyzed for MLH1 protein expression using immunohistochemistry (IHC). BRAF V600E mutation was detected by IHC using a specific monoclonal antibody (VE1) and by qPCR. All MLH1 protein-negative cases were subjected to microsatellite instability analysis and MLH1 promoter methylation assay. MLH1 protein expression deficiency and high microsatellite instability (MSI-H) were detected in 18 of the 137 (13.1%) consecutive colorectal cancer specimens. Detection of the BRAF V600E mutation by IHC was 100% sensitive and specific as compared to qPCR, and this mutation was frequently present in the MSI-H group (77.8%; 14/18) and less frequently in the microsatellite-stable group (7.6%; 9/118). All BRAF V600E mutated cases of the MSI-H group presented with a MLH1 promoter methylation (14/14) as detected by methylation-specific multiplex ligation-dependent probe amplification. When BRAF was wild type in the MSI-H group, only one MLH1 promoter methylation was detected (1/4), and of the remaining three cases without MLH1 methylation, two were identified to harbor an MLH1 mutation consistent with Lynch syndrome. Finally, 11 previously confirmed Lynch syndrome cases were analyzed for BRAF V600E mutation, and all of them were wild type. In conclusion, detection of BRAF V600E in colorectal cancer specimens by IHC is sensitive and specific and may help to identify Lynch syndrome patients.

Inhibition of cyclooxygenase-2 causes regression of gastric adenomas in trefoil factor 1 deficient mice.

Cyclooxygenase-2 (Cox-2) expression is a marker of reduced survival in gastric cancer patients, and inhibition of Cox-2 suppresses gastrointestinal carcinogenesis in experimental animal models. To investigate the role of Cox-2 in gastric carcinogenesis in vivo, we utilized trefoil factor 1 (Tff1) deficient mice, which model the neoplastic process of the stomach by developing gastric adenomas with full penetrance. These tumors express Cox-2 protein and mRNA, and we have now investigated the effects of genetic deletion of the mouse Cox-2 gene [also known as prostaglandin-endoperoxide synthase 2 (Ptgs2)] and a Cox-2 selective drug celecoxib. Our results show that genetic deletion of Cox-2 in the Tff1 deleted background resulted in reduced adenoma size and ulceration with a chronic inflammatory reaction at the site of the adenoma. To characterize the effect of Cox-2 inhibition in more detail, mice that had already developed an adenoma were fed with celecoxib for 8-14 weeks, which resulted in disruption of the adenoma that ranged from superficial erosion to deep ulcerated destruction accompanied with chronic inflammation. Importantly, mice fed with celecoxib for 16 weeks, followed by control food for 9 weeks, redeveloped a complete adenoma with no detectable inflammatory process. Finally, we determined the identity of the Cox-2 expressing cells and found them to be fibroblasts. Our results show that inhibition of Cox-2 is sufficient to reversibly disrupt gastric adenomas in mice.

Role of RNA binding protein HuR in ductal carcinoma in situ of the breast.

HuR is a ubiquitously expressed RNA-binding protein that modulates gene expression at the post-transcriptional level. It is predominantly nuclear, but can shuttle between the nucleus and the cytoplasm. While in the cytoplasm HuR can stabilize its target transcripts, many of which encode proteins involved in carcinogenesis. While cytoplasmic HuR expression is a marker of reduced survival in breast cancer, its role in precursor lesions of malignant diseases is unclear. To address this we explored HuR expression in atypical ductal hyperplasia (ADH) and in ductal in situ carcinomas (DCIS). We show that cytoplasmic HuR expression is elevated in both ADH and DCIS when compared to normal controls, and that this expression associated with high grade, progesterone receptor negativity and microinvasion and/or tumour-positive sentinel nodes of the DCIS. To study the mechanisms of HuR in breast carcinogenesis, HuR expression was silenced in an immortalized breast epithelial cell line (184B5Me), which led to reduction in anchorage-independent growth, increased programmed cell death and inhibition of invasion. In addition, we identified two novel target transcripts (CTGF and RAB31) that are regulated by HuR and that bind HuR protein in this cell line. Our results show that HuR is aberrantly expressed at early stages of breast carcinogenesis and that its inhibition can lead to suppression of this process. ArrayExpress Accession No. E-MEXP-3035.

Basal cytokeratins in breast tumours among BRCA1, BRCA2 and mutation-negative breast cancer families.

INTRODUCTION: Finding new immunohistochemical markers that are specific to hereditary breast cancer could help us to select candidates for BRCA1/BRCA2 mutation testing and to understand the biological pathways of tumour development. METHODS: Using breast cancer tumour microarrays, immunohistochemical expression of cytokeratin (CK)-5/6, CK-14 and CK-17 was evaluated in breast tumours from BRCA1 families (n = 46), BRCA2 families (n = 40), non-BRCA1/BRCA2 families (n = 358) and familial breast cancer patients with one first-degree relative affected by breast or ovarian cancer (n = 270), as well as from patients with sporadic breast cancer (n = 364). Staining for CK-5/6, CK-14 and CK-17 was compared between these groups and correlated with other clinical and histological factors. RESULTS: CK-5/6, CK-14 and CK-17 were detected mostly among oestrogen receptor (ER)-negative, progesterone receptor (PR)-negative and high-grade tumours. We found the highest percentages of samples positive for these CKs among ER-negative/HER2-negative tumours. In univariate analysis, CK-14 was significantly associated with tumours from BRCA1 (39%; P < 0.0005), BRCA2 (27%; P = 0.011), and non-BRCA1/BRCA2 (21%; P < 0.005) families, as compared with sporadic tumours (10%). However, in multivariate analysis, CKs were not found to be independently associated with BRCA1 or BRCA2 mutation status, and the most effective predictors of BRCA1 mutations were age at onset, HER2 status, and either ER or PR status. CONCLUSION: Although our study confirms that basal CKs can help to identify BRCA1 mutation carriers, this effect was weaker than previously suggested and CKs did not independently predict BRCA1 mutation either from sporadic or familial breast cancer cases. The most effective, independent predictors of BRCA1 mutations were age at onset, HER2 status, and either ER or PR status, as compared with sporadic or non-BRCA1/BRCA2 cancers.

Prognostic role of HuR in hereditary breast cancer.

PURPOSE: HuR is an mRNA-binding protein that enhances the stability of certain transcripts and can regulate their translation. Elevated cytoplasmic expression of HuR protein has been linked to carcinogenesis and is associated with reduced survival in breast, ovarian, and gastric adenocarcinomas. EXPERIMENTAL DESIGN: Here, we have explored the relevance of HuR in familial breast cancer. Tumor samples were collected from patients with identified BRCA1 (n = 51) or BRCA2 (n = 47) mutations or familial non-BRCA1/2 cases (n = 525), and analyzed by immunohistochemistry. RESULTS: Among familial non-BRCA1/2 breast cancer patients, cytoplasmic HuR protein expression was present in 39.4% of the cases and was associated with estrogen receptor negativity, progesterone receptor negativity, p53 positivity, high tumor grade, and ductal type of the tumor. In multivariate analysis, cytoplasmic HuR expression was an independent marker of reduced survival in the non-BRCA1/2 group along with tumor size >2 cm, lymph node metastasis, and high histologic grade. In patients with BRCA1 or BRCA2 mutations, cytoplasmic HuR expression was more frequent (62.7% for BRCA1 and 61.7% for BRCA2) than in the non-BRCA1/2 group, but in BRCA-mutated subgroups cytoplasmic HuR expression did not associate with survival. CONCLUSIONS: Our results show that HuR is an important prognostic factor in familial breast cancer patients and may contribute to carcinogenesis in this disease.

Expression of cyclooxygenase-2 is regulated by glycogen synthase kinase-3beta in gastric cancer cells.

Cyclooxygenase-2 (COX-2) expression is a marker of poor prognosis in gastric cancer patients, and its inhibition suppresses gastric tumorigenesis in experimental animal models. The mechanism that leads to COX-2 overexpression in this tumor type is unknown. We have now shown that inhibition of phosphatidylinositol 3-kinase by LY294002 suppresses both basal and phorbol myristate acetate-induced COX-2 expression in TMK-1 and MKN-28 gastric cancer cells. Furthermore, inhibition of glycogen synthase kinase-3beta (GSK-3beta) by SB415286 induced expression of COX-2 mRNA and protein as well as the enzyme activity in the gastric cancer cells. The effect of SB415286 was confirmed by the use of two additional GSK-3beta inhibitors, lithium chloride and SB216763. SB415286 had a modest 1.6-fold stimulatory effect on a 2-kb COX-2 promoter reporter construct, but more importantly, it was shown to block the decay of COX-2 mRNA. In contrast to modulation of phosphatidylinositol 3-kinase/Akt/GSK-3beta pathway, inhibitors of mitogen-activated protein kinases (MEK 1/2, p38, JNK) or the mammalian target of rapamycin did not alter COX-2 expression in gastric cancer cells. Our data show that inhibition of GSK-3beta stimulates COX-2 expression in gastric cancer cells, which seems to be primarily facilitated via an increase in mRNA stability and to a lesser extent through enhanced transcription.

Cytoplasmic HuR expression correlates with epithelial cancer cell but not with stromal cell cyclooxygenase-2 expression in mucinous ovarian carcinoma.

UNLABELLED: Cyclooxygenase-2 (COX-2) expression has been found to associate with poor prognosis in several types of carcinomas. HuR is an mRNA stability protein and it regulates the expression of COX-2. OBJECTIVES AND METHODS: We analyzed the expression of COX-2 and HuR in 64 mucinous ovarian carcinoma specimens by immunohistochemistry. RESULTS: In mucinous tumors, high COX-2 protein expression was found in epithelial cancer cells in 39% (22/56) and in stromal cells in 24% (13/55) of the specimens. The expression of COX-2 in cancer cells correlated with high grade (P = 0.0285), but stromal COX-2 expression had no correlation with any clinical parameter tested. Cytoplasmic HuR protein expression was observed in cancer cells in 47% (27/57) and in stromal cells in 7% (4/56) of the mucinous tumors, and it correlated with COX-2 expression in the cancer cells (P = 0.0162) but not in the stroma. CONCLUSION: Our results support the hypothesis that cytoplasmic HuR is connected to COX-2 expression in ovarian carcinoma, but that its role is restricted to the transformed epithelial cancer cells.

Breast cancer patients with p53 Pro72 homozygous genotype have a poorer survival.

PURPOSE: The p53 R72P polymorphism has been suggested to play a role in many cancers, including breast cancer. Our aim was to evaluate association of R72P with breast cancer risk as well as histopathologic features of the breast tumors and survival. EXPERIMENTAL DESIGN: The germ line R72P genotype was defined among 939 Finnish familial and 888 unselected breast cancer patients and 736 healthy population controls. The clinical and biological variables were tested for association by univariate analysis and the effects of several variables on survival by Cox's proportional hazards regression model. RESULTS: The distribution of the genotypes was similar in all groups studied, suggesting no association with breast cancer risk. Unselected breast cancer patients with 72P homozygous genotype presented significantly more often with lobular carcinoma, whereas R72 allele carriers had a significantly higher frequency of ductal carcinomas (P = 0.004). No significant association with other histopathologic variables, like tumor grade, hormone receptor status (estrogen and progesterone receptors), or tumor-node-metastasis stage, was observed. Survival analysis showed that unselected breast cancer patients with 72P homozygous genotype had significantly poorer survival than patients with other genotypes (P = 0.003). This effect on survival was independent of p53 expression in the tumors and multivariate analysis showed that 72P homozygous genotype was overall an independent prognostic factor (risk ratio of death, 2.1; 95% confidence interval, 1.4-3.3; P = 0.001). CONCLUSIONS: These results suggest no effect of either R72P allele on breast cancer risk but a significantly reduced survival for 72P homozygous breast cancer patients. The finding of codon 72 genotype as an independent prognostic marker for breast cancer warrants further studies.

Cytoplasmic HuR expression is a prognostic factor in invasive ductal breast carcinoma.

HuR is a ubiquitously expressed mRNA-binding protein. Intracellular localization of HuR is predominantly nuclear, but it shuttles between the nucleus and the cytoplasm. In the cytoplasm it can stabilize certain transcripts. Because nucleocytoplasmic translocation of HuR is necessary for its activity, it was hypothesized that cytoplasmic HuR expression in cancer cells could be a prognostic marker. To test the significance of HuR in carcinogenesis of the breast, we have investigated HuR expression in a mouse mammary gland tumor model and from 133 invasive ductal breast carcinoma specimens. HuR expression was elevated in the cyclooxygenase-2 transgene-induced mouse mammary tumors, and its expression was predominantly cytoplasmic in the tumor cells. In the human carcinoma samples, high cytoplasmic immunoreactivity for HuR was found in 29% (38 of 133) of the cases. Cytoplasmic HuR expression associated with high grade (P = 0.0050) and tumor size over 2 cm (P = 0.0082). Five-year distant disease-free survival rate was 42% [95% confidence interval (95% CI), 26-58] in cytoplasm-high category and 84% (95% CI, 76-91) in cytoplasm-negative or -low category (P < 0.0001), and high cytoplasmic expression of HuR was an independent prognostic factor in a Cox multivariate model (relative risk 2.07; 95% CI, 1.05-4.07). Moreover, high cytoplasmic HuR immunopositivity was significantly associated with poor outcome in the subgroup of node-negative breast cancer in a univariate analysis (P < 0.0007). Our results show that high cytoplasmic HuR expression is associated with a poor histologic differentiation, large tumor size, and poor survival in ductal breast carcinoma. Thus, HuR is the first mRNA stability protein of which expression associates with poor outcome in breast cancer.