BackgroundMicroRNA-34a (miR-34a) is a transcriptional target of p53 and is down-regulated in pancreatic cancer. This study aimed to investigate the functional significance of miR-34a in pancreatic cancer progression through its epigenetic restoration with chromatin modulators, demethylating agent 5-Aza-2′-deoxycytidine (5-Aza-dC) and HDAC inhibitor Vorinostat (SAHA).Methodology/Principal FindingsRe-expression of miR-34a in human pancreatic cancer stem cells (CSCs) and in human pancreatic cancer cell lines upon treatment with 5-Aza-dC and SAHA strongly inhibited the cell proliferation, cell cycle progression, self-renewal, epithelial to mesenchymal transition (EMT) and invasion. In pancreatic CSCs, modulation of miR-34a induced apoptosis by activating caspase-3/7. Treatment of pancreatic CSCs with the chromatin-modulating agents resulted in the inhibition of Bcl-2, CDK6 and SIRT1, which are the putative targets of miR-34a. MiR-34a upregulation by these agents also induced acetylated p53, p21WAF1, p27KIP1 and PUMA in pancreatic CSCs. Inhibition of miR-34a by antagomiR abrogates the effects of 5-Aza-dC and SAHA, suggesting that 5-Aza-dC and SAHA regulate stem cell characteristics through miR-34a. In CSCs, SAHA inhibited Notch pathway, suggesting its suppression may contribute to inhibition of the self-renewal capacity and induction of apoptosis. Interestingly, treatment of pancreatic CSCs with SAHA resulted in the inhibition of EMT with the transcriptional up-regulation of E-Cadherin and down-regulation of N-Cadherin. Expression of EMT inducers (Zeb-1, Snail and Slug) was inhibited in CSCs upon treatment with SAHA. 5-Aza-dC and SAHA also retard in vitro migration and invasion of CSCs.ConclusionsThe present study thus demonstrates the role of miR-34a as a critical regulator of pancreatic cancer progression by the regulating CSC characteristics. The restoration of its expression by 5-Aza-dC and SAHA in CSCs will not only provide mechanistic insight and therapeutic targets for pancreatic cancer but also promising reagents to boost patient response to existing chemotherapies or as a standalone cancer drug by eliminating the CSC characteristics.

We recently reported that allopolyploid formation in wheat was accompanied by rapid nonrandom elimination of specific low-copy, noncoding DNA sequences. These sequences occur in all diploid progenitors but are chromosome- or genome-specific at the polyploid level. To further investigate this phenomenon, we studied nine of these sequences, six chromosome-specific sequences and three genome-specific sequences, all isolated from common wheat. The various sequences were hybridized to DNA derived from nine newly synthesized amphiploids at different ploidy levels and to DNA from their parental lines. Although sequences homologous to the probes occur in all parental lines, a nonrandom loss of hybridization fragments was found at a high frequency in all amphiploids studied. In addition, a "loss/gain" of a hybridization fragment(s) was noticed in some of the amphiploids at lower frequency. Neither the type nor the frequency of changes was affected by intergenomic recombination or DNA methylation. It is suggested that rapid genomic changes culminated in a "programmed" pattern of elimination and (or) modification of specific low-copy DNA sequences following allopolyploidization. These events augmented the differentiation of homoeologous chromosomes, thus providing the physical basis for the diploid-like cytological behavior of polyploid wheat.Key words: wheat, allopolyploidy, genome evolution, chromosome- or genome-specific sequences, sequence elimination, homoeologous chromosome differentiation.

Multiple lines of evidence suggest that the Sonic Hedgehog (Shh) signaling pathway is aberrantly reactivated in pancreatic cancer stem cells (CSCs). The objectives of this study were to examine the molecular mechanisms by which GANT-61 (Gli transcription factor inhibitor) regulates stem cell characteristics and tumor growth. Effects of GANT-61 on CSC’s viability, spheroid formation, apoptosis, DNA-binding and transcriptional activities, and epithelial-mesenchymal transition (EMT) were measured. Humanized NOD/SCID/IL2Rgammanull mice were used to examine the effects of GANT-61 on CSC’s tumor growth. GANT-61 inhibited cell viability, spheroid formation, and Gli-DNA binding and transcriptional activities, and induced apoptosis by activation of caspase-3 and cleavage of Poly-ADP ribose Polymerase (PARP). GANT-61 increased the expression of TRAIL-R1/DR4, TRAIL-R2/DR5 and Fas, and decreased expression of PDGFRα and Bcl-2. GANT-61 also suppressed EMT by up-regulating E-cadherin and inhibiting N-cadherin and transcription factors Snail, Slug and Zeb1. In addition, GANT-61 inhibited pluripotency maintaining factors Nanog, Oct4, Sox-2 and cMyc. Suppression of both Gli1 plus Gli2 by shRNA mimicked the changes in cell viability, spheroid formation, apoptosis and gene expression observed in GANT-61-treated pancreatic CSCs. Furthermore, GANT-61 inhibited CSC tumor growth which was associated with up-regulation of DR4 and DR5 expression, and suppression of Gli1, Gli2, Bcl-2, CCND2 and Zeb1 expression in tumor tissues derived from NOD/SCID IL2Rγ null mice. Our data highlight the importance of Shh pathway for self-renewal and metastasis of pancreatic CSCs, and also suggest Gli as a therapeutic target for pancreatic cancer in eliminating CSCs.

Activation of the sonic hedgehog (Shh) pathway is required for the growth of numerous tissues and organs and recent evidence indicates that this pathway is often recruited to stimulate growth of cancer stem cells (CSCs) and to orchestrate the reprogramming of cancer cells via epithelial mesenchymal transition (EMT). The objectives of this study were to examine the molecular mechanisms by which (-)-epigallocatechin-3-gallate (EGCG), an active compound in green tea, inhibits self-renewal capacity of pancreatic CSCs, and synergizes with quercetin, a major polyphenol and flavonoid commonly detected in many fruits and vegetables. Our data demonstrated that EGCG inhibited the expression of pluripotency maintaining transcription factors (Nanog, c-Myc and Oct-4), and self-renewal capacity of pancreatic CSCs. Inhibition of Nanog by shRNA enhanced the inhibitory effects of EGCG on self-renewal capacity of CSCs. EGCG inhibited cell proliferation and induced apoptosis by inhibiting the expression of Bcl-2 and XIAP, and activating caspase-3. Interestingly, EGCG also inhibited the components of Shh pathway (smoothened, patched, Gli1 and Gli2) and Gli transcriptional activity. Furthermore, EGCG inhibited EMT by inhibiting the expression of Snail, Slug and ZEB1, and TCF/LEF transcriptional activity, which correlated with significantly reduced CSC’s migration and invasion, suggesting the blockade of signaling involved in early metastasis. Furthermore, combination of quercetin with EGCG had synergistic inhibitory effects on self-renewal capacity of CSCs through attenuation of TCF/LEF and Gli activities. Since aberrant Shh signaling occurs in pancreatic tumorigenesis, therapeutics that target Shh pathway may improve the outcomes of patients with pancreatic cancer by targeting CSCs.