Fundamentals of transcription factors and their impact on pancreatic development and cancer

Computational analyses reveal a prognostic impact of TULP3 as a transcriptional master regulator in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is recognized world-wide as an aggressive disease with poor prognosis in patients with or without resection. Further knowledge about the biological mechanisms of PDAC is necessary to enable the identification of novel molecular markers and therapeutic targets for early diagnosis and improved treatment. Transcription factors are the final effectors of signaling pathways and regulate a number of cellular functions. Changes in their expression may contribute to cellular transformation and tumor progression. Thus, the aim of the present study was to identify the Master Regulators (MRs) of transcription potentially involved in PDAC disease. To achieve this goal, we utilized microarray data to correlate MR genes with the tumor phenotype. Analyses were performed with RTN, Limma, and Survival packages in the R environment. We identified Tubby-like protein 3 (TULP3) as a MR of transcription in PDAC samples. The prognostic value of TULP3 was assessed in three independent cohort analyses. Our data demonstrated that pancreatic cancer patients exhibiting high transcriptional levels of TULP3 showed a poor overall survival rate. High expression levels of TULP3 may play an essential role in pancreatic cancer progression and possibly lead to a poor clinical outcome. Our results highlight the potential use of TULP3 as a clinical prognostic biomarker for pancreatic adenocarcinoma.

The sunset of somatic genetics and the dawn of epigenetics: a new frontier in pancreatic cancer research

PURPOSE OF REVIEW

The excitement of finding a cancer modulator which is either mutated or deleted in vivo (genetics), unfortunately, is shadowed by the fact that we scientists have failed to live to the promise of gene therapy, and therefore, these genes cannot be replaced to cure the patients. On the contrary, both DNA methylation and chromatin-mediated inactivation of tumor suppressor genes (epigenetics), for example, are reversible as demonstrated by the relative success of emerging therapies. Therefore, epigenetics with its molecular basis (DNA methylation and chromatin modification) is among the most promising areas of cancer research and is a nascent field in pancreatic cancer research.

RECENT FINDINGS

Here, we review and update novel findings on epigenetics as it applies to pancreatic cancer.

SUMMARY

Special focus has been given to novel potential therapeutic targets and currently available drugs, which are emerging from this exciting new field of pancreatic cancer research.

Aberrant gata-3 expression in human pancreatic cancer

Gata-3 has been shown to specifically alter its expression patterns in different types of cancers. Recent evidence suggests that an interference of Gata-3 exists in the TGF-beta signaling pathway. To determine the role of Gata-3 in pancreatic cancer, pancreatic cancer samples were analyzed in comparison to normal pancreatic tissues. Furthermore, four different pancreatic cancer cell lines with different alterations of the TGF-beta pathway were studied. To evaluate if a potential relationship with TGF-beta signaling pathway exists, we correlated mRNA expression levels with the expression of TGF-betas, TGF-beta receptors, and Smad-3. Finally, we analyzed the influence of TGF-beta on Gata-3 expression in vitro. All pancreatic cancer samples demonstrated a marked overexpression of Gata-3 mRNA and protein. Immunohistochemical staining revealed strong and persistent cytoplasmic Gata-3 immunoreactivity in cancer cells. In an electrophoretic mobility shift assay, a disturbed nuclear translocation was confirmed. The expression of Gata-3 showed a significant correlation with the expression of TGF-betas, TGF-beta receptors, and Smad-3. TGF-beta responsive cell lines showed a downregulation of Gata-3 mRNA upon TGF-beta exposure, whereas in TGF-beta-unresponsive cell lines, Gata-3 mRNA expression persisted at high levels. Furthermore, strong specific upregulation of Gata-3 impaired nuclear translocation and its cooperative action with the TGF-beta pathway, suggesting that Gata-3 plays a central role in human pancreatic cancer.

Characterization of risk for general population exposure to perfluorooctanoate

Perfluorooctanoate (PFOA), an environmentally and metabolically stable perfluorinated carboxylic acid, has been detected in the serum of children, adults and the elderly from the United States with the upper bound of the 95th percentile estimate in the range of 0.011-0.014 microg/mL (ppm). In this risk characterization, margins of exposure (MOE), which can provide a realistic perspective on potential for human risk, were determined by comparison of general population serum PFOA concentrations with serum concentrations from toxicological studies that are associated with the lower 95% confidence limit of a modeled 10 percent response or incidence level (LBMIC(10)) using USEPA BMDS software. The LBMIC(10) was estimated using surrogate data from other studies or pharmacokinetic relationships if serum PFOA data were not available. Modeled dose-responses (with resulting LBMIC(10) values) included post-natal effects in rats (29 microg/mL), liver-weight increase (23 microg/mL), and body-weight change (60 microg/mL) in rats and monkeys, and incidence of Leydig cell adenoma (125 microg/mL) in rats. MOE values based on the upper bound 95th percentile population serum PFOA concentration were large, ranging from 1600 (liver-weight increase) to 8900 (Leydig cell adenoma). These MOE values represent substantial protection of children, adults, and the elderly.