Oncogene In Pancreatic Cancer Research Articles

Abstract 4672: Overexpression of NR5A2/LRH1 in pancreatic cancer and possible association with clinical outcome

Abstract Pancreatic cancer is the 4th leading cause of cancer deaths in the United States and it has the lowest 5-year survival rate in all tumors. Genome-wide association study (GWAS) has identified a significant association between NR5A2/LRH1 gene variants and risk for pancreatic cancer. LRH1, a direct target of PDX1, governs liver and pancreas differentiation in early embryonic development and controls cholesterol/bile-acid homeostasis and steroidogenesis in adulthood. LRH1 promotes cell proliferation by interacting with β-catenin/Tcf4 signaling and upregulating estrogen metabolic genes. We hypothesize that LRH1 acts as an oncogene in pancreatic cancer. We measured LRH1 protein expression by immunohistochemistry (IHC) in 129 resected pancreatic tumors and LRH1 mRNA expression by RT-PCR in 15 frozen paired tumor and adjacent normal tissues. We examined the differences in expression levels between tumor and normal tissues using paired t-test. We evaluated the correlation of protein or mRNA expression levels with overall survival (OS) or tumor characteristics by Cox regression or χ2 test, respectively. IHC showed both nuclear and cytoplasm staining for LRH1. Tumors had a higher level of LRH1 expression than normal tissue did (Mean ± SD of staining score: 5.46 ± 1.64 vs. 3.73 ± 1.77, respectively, p<0.001). Patients with a higher level of nuclear LRH1 expression had worse survival (HR = 2.41, 95% CI=0.97-6.00, p=0.059) but patients with a higher level of cytoplasmic LRH1 expression had better survival (HR = 0.36, 95% CI = 0.09-1.46, p=0.15). Eight out of 8 tumors (100%) with lower nuclear LRH1 expression (staining score <3) were well or moderately differentiated, while 44 out of 121 (36.4%) of tumors with higher nuclear LRH1 expression (staining score ≥ 3) were poorly differentiated (p=0.03). The LRH1 mRNA expression level was 8-fold higher in tumors than in normal tissues (p<0.001). The observed association between LRH1 overexpression and worse clinical outcome and more aggressive tumor type supports the hypothesis that LRH1 acts as an oncogene in pancreatic cancer. Whether LRH1 can be a putative therapeutic target for the treatment of pancreatic cancer needs further investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4672. doi:10.1158/1538-7445.AM2011-4672

Abstract 4011: Evidence supporting a role of c-Myb in pancreatic cancer

Abstract The clinical outcome from pancreatic cancer has not improved over the years. This is, in part, due to not well understood disease mechanisms and consequently there is little progress made in developing intervention therapy. Many genetic alterations have been characterized in pancreatic cancer, of which some have been shown to be functionally relevant. In an earlier study, c-Myb was identified as a candidate oncogene in pancreatic cancer with gene amplification in a subset and overexpression in majority of pancreatic cancer tissues and cell lines. The role of c-Myb in pancreatic cancer, however, has not been defined so far. c-Myb is a cellular progenitor of v-Myb oncogenes, which encodes for a transcription factor and confers its oncogenic activity by regulating the expression of several target genes. To examine the functional role of c-Myb in pancreatic cancer, we silenced its expression in two pancreatic cancer cell lines (Panc1 and MiaPaCa) by stable transfection of a c-Myb-targeted short-hairpin RNA (shRNA)-expression plasmid. Silencing of c-Myb expression resulted in diminished growth and clonogenicity of pancreatic cancer cells. c-Myb knockdown pancreatic cancer cells were arrested at G1/S boundary of cell cycle, and exhibited enhanced apoptosis. Furthermore, we observed decreased migration and invasion in c-Myb silenced pancreatic cancer cells as compared to the control cells. Immunoblot analysis demonstrated gain of epithelial- and loss of mesenchymal- markers in c-Myb knockdown pancreatic cancer cells, thus indicating a reversal of epithelial to mesenchymal transition (EMT). We also observed noticeable changes in cell morphology and actin-organization upon silencing of c-Myb expression that were consistent with loss of mesenchymal features. Together, these findings provide first experimental evidence for a functional role of c-Myb in pancreatic cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4011. doi:10.1158/1538-7445.AM2011-4011

Down-regulation of CacyBP is associated with poor prognosis and the effects on COX-2 expression in breast cancer

Calcyclin-binding protein (CacyBP) is a tumor suppressor in gastric and renal cell carcinoma, but an oncogene in pancreatic cancer. However, the function of CacyBP in breast cancer has not been well elucidated. In this study, we explored the clinical relevance of CacyBP and investigated the relationship between CacyBP and COX-2 in breast cancer. Immunohistochemical analysis in 172 cases of breast tissues showed that the positive rate of CacyBP protein expression in normal breast tissues (NBT) (89.3%) was higher than that in invasive ductal carcinoma (IDC) (56.1%) (P<0.05). RT-PCR and Western blot analysis showed that CacyBP mRNA and protein expression were significantly lower in tumor tissues as compared to those in the corresponding non-tumorous tissues (P<0.05). The expression trend of COX-2 was opposite with CacyBP in breast carcinogenesis. Moreover, the CacyBP expression was significantly negatively associated with the COX expression in the 132 breast cancer samples (correlation coefficient = 0.505, P<0.001). The clinicopathological data analysis in 132 breast cancer samples showed that CacyBP expression was positively correlated with well differentiated samples (P=0.021), low pathologic TNM stage (P=0.009), and no lymphatic metastasis (P=0.027) of patients with breast cancer. Furthermore, reduced CacyBP expression was associated with poor prognosis. Knockdown of CacyBP gene using siRNA enhanced the proliferation and invasion ability of breast cancer cells, which was dependent on COX-2 expression. In conclusion, CacyBP regulation of COX-2 expression may play an important role in human breast carcinogenesis. Restoration of CacyBP gene is a potential therapeutic target of breast cancer.

Construction of MKK4 adenovirus and its effects on the proliferation and invasion of pancreatic cancer cells

Objective To explore the effects of MKK4 gene on the proliferation and invasion of pancreatic cancer cells. Methods Western blotting was used to assay the expression of MKK4 in pancreatic cancer cell lines AsPC1, BxPC3, Hs766t, MiaPaCa2, and Pancl. MKK4 adenovirus was constructed and transfected into MKK4 negative pancreatic cancer cells. Thymidine incorporation assays were used to measure the DNA synthesis rate and Matrigel assays to measure the invasive ability of pancreatic cells. Results In pancreatic cancer cells, MKK4 lost expression in AsPC1 and BxPC3 cells. MKK4 adenovirus was constructed and transfected into MKK4 negative pancreatic cancer cell lines AsPC1 and BxPC3. The exogenous expression of MKK4 in AsPC1 and BxPC3 increased the proliferation ability by 53% and 61%( P ＜ 0. 05 ), increased the invasion ability by ( 8. 2 ± 2. 7) fold and ( 15.7 ± 1.6) fold ( P ＜ 0. 01 ), respectively. Conclusion The exogenous expression of MKK4 increases the proliferation and invasion of pancreatic cancer cells, which hints that MKK4 gene is a potential oncogene in pancreatic cancer. Key words: Pancreatic carcinoma; MKK4

Notch1 Functions as a Tumor Suppressor in a Model of K-ras–Induced Pancreatic Ductal Adenocarcinoma

K-ras is the most commonly mutated oncogene in pancreatic cancer and its activation in murine models is sufficient to recapitulate the spectrum of lesions seen in human pancreatic ductal adenocarcinoma (PDAC). Recent studies suggest that Notch receptor signaling becomes reactivated in a subset of PDACs, leading to the hypothesis that Notch1 functions as an oncogene in this setting. To determine whether Notch1 is required for K-ras-induced tumorigenesis, we used a mouse model in which an oncogenic allele of K-ras is activated and Notch1 is deleted simultaneously in the pancreas. Unexpectedly, the loss of Notch1 in this model resulted in increased tumor incidence and progression, implying that Notch1 can function as a tumor suppressor gene in PDAC.

Abstract 2204: A functional genomics approach using high-throughput RNAi identifies TNK1 as a putative oncogene in pancreatic cancer

Abstract Pancreatic cancer is a deadly disease that kills more than 30,000 people in the United States each year. Pancreatic cancer often presents as an advanced, therapy resistant cancer that is refractory to many forms of chemotherapy. Current therapeutics to treat pancreatic cancer include gemcitabine, yet the one-year survival of pancreatic cancer patients treated with gemcitabine is about 18%, representing a significant but modest advancement in the quality of life. In order to improve gemcitabine response in pancreatic cancer cells, we utilized high-throughput RNAi (HT-RNAi) to identify genes that when silenced would sensitize pancreatic cancer cells to gemcitabine. This screen also identified genes that represent “Achilles Heel” targets, which when silenced, results in a decrease in pancreatic cancer cell viability. A HT-RNAi assay was developed to monitor the growth inhibition of BxPC3 pancreatic cancer cells transfected with siRNA and treated with gemcitabine. For screening, BxPC3 cells were transfected with siRNA from several two siRNA libraries including kinases (574 kinases) and druggable-genome targets (∼7000 genes). Twenty-four hours after siRNA transfection, an EC30 dose of gemcitabine was added and growth was assessed after 72 hours of drug exposure. Results from the screen showed that silencing the TNK1 resulted in a significant decrease in cell viability and also modestly increased sensitivity to gemcitabine. These results were consistent with previous HT-RNAi screens performed on MIA PaCa-2 cells. To confirm TNK1 as a potential target, a panel of pancreatic cancer cells were transfected with one of four different TNK1 siRNA and then treated with a range of gemcitabine doses to evaluate gemcitabine sensitivity following knockdown of TNK1. The TNK1 protein has previously been identified as a putative inhibitor of Ras and an inhibitor of TNFα-induced translocation of NFkB. We were able to confirm this in pancreatic cancer cells by demonstrating an increase in p-MEK 1/2 as well as an increase in NFkB gene targets in TNK1 siRNA-treated cells. Furthermore, we have characterized TNK1 expression in a panel of pancreatic cell lines. Although previous studies suggest that TNK1 may serve as a tumor suppressor, here, we suggest that TNK1 also demonstrates oncogenic properties in pancreatic cancer cells. The role that TNK1 plays in pathways such as K-ras and NFkB indicate it is likely to be an important factor in the development and/or progression of pancreatic cancer. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2204.

Overexpression of HER2/neu oncogene in pancreatic cancer correlates with shortened survival.

For the purpose of determining the prognostic significance of HER2/neu oncogene in pancreatic and ampullary cancers, 21 pancreatic cancers of ductal origin and six cancers of the ampulla of Vater were studied immunohistochemically using the monoclonal antibody (MAb) CB11, specifically reactive with HER2/neu product. Staining of the epithelium of the normal duct and acini was negative or weakly positive. Moderately and strongly positive reactions indicated the overexpression of this gene, and were found in 10 of 21 (47.6%) pancreatic cancers of ductal origin and in 2 of 6 (33.3%) ampullary adenocarcinomas. Overexpression of HER2/neu was closely and inversely related to the survival of the patients with pancreatic cancer of ductal origin: 19.1 +/- 11.7 mo for those not overexpressing vs 7.3 +/- 3.8 mo for the overexpressors (p < 0.01). Among the pancreatic cancer group, 11 patients underwent cancer resection. The average survival for the 7 with nonoverexpressing cancer was 21.4 +/- 14.3 mo vs 10.5 +/- 3.6 mo for those with overexpressing tumor. Among those not undergoing resection, the average survival for the 4 with nonoverexpressing cancer was 15.0 +/- 3.8 mo as contrasted to 5.2 +/- 2.1 mo for the overexpressors (p < 0.01). Although the number of patients is small, these findings suggest that the overexpression of HER2/neu gene product may be frequently found in pancreatic cancer of ductal origin and may be one of the useful prognostic biomarkers for this cancer.