Epigenetic regulation and role of metastasis suppressor genes in pancreatic ductal adenocarcinoma

Metastasis suppressor genes in clinical practice: are they druggable?

Since the identification of NM23 (now called NME1) as the first metastasis suppressor gene (MSG), a small number of other gene products and non-coding RNAs have been identified that suppress specific parameters of the metastatic cascade, yet which have little or no ability to regulate primary tumor initiation or maintenance. MSG can regulate various pathways or cell biological functions such as those controlling mitogen-activated protein kinase pathway mediators, cell-cell and cell-extracellular matrix protein adhesion, cytoskeletal architecture, G-protein-coupled receptors, apoptosis, and transcriptional complexes. One defining facet of this gene class is that their expression is typically downregulated, not mutated, in metastasis, such that any effective therapeutic intervention would involve their re-expression. This review will address the therapeutic targeting of MSG, once thought to be a daunting task only facilitated by ectopically re-expressing MSG in metastatic cells in vivo. Examples will be cited of attempts to identify actionable oncogenic pathways that might suppress the formation or progression of metastases through the re-expression of specific metastasis suppressors.

KISS1 in metastatic cancer research and treatment: potential and paradoxes

The significance of KISS1 goes beyond its original discovery as a metastasis suppressor. Its function as a neuropeptide involved in diverse physiologic processes is more well studied. Enthusiasm regarding KISS1 has cumulated in clinical trials in multiple fields related to reproduction and metabolism. But its cancer therapeutic space is unsettled. This review focuses on collating data from cancer and non-cancer fields in order to understand shared and disparate signaling that might inform clinical development in the cancer therapeutic and biomarker space. Research has focused on amino acid residues 68-121 (kisspeptin 54), binding to the KISS1 receptor and cellular responses. Evidence and counterevidence regarding this canonical pathway require closer look at the covariates so that the incredible potential of KISS1 can be realized.

The complex genetics of hypoplastic left heart syndrome

Congenital heart disease (CHD) affects up to 1% of live births. Although a genetic etiology is indicated by an increased recurrence risk, sporadic occurrence suggests that CHD genetics is complex. Here, we show that hypoplastic left heart syndrome (HLHS), a severe CHD, is multigenic and genetically heterogeneous. Using mouse forward genetics, we report what is, to our knowledge, the first isolation of HLHS mutant mice and identification of genes causing HLHS. Mutations from seven HLHS mouse lines showed multigenic enrichment in ten human chromosome regions linked to HLHS. Mutations in Sap130 and Pcdha9, genes not previously associated with CHD, were validated by CRISPR-Cas9 genome editing in mice as being digenic causes of HLHS. We also identified one subject with HLHS with SAP130 and PCDHA13 mutations. Mouse and zebrafish modeling showed that Sap130 mediates left ventricular hypoplasia, whereas Pcdha9 increases penetrance of aortic valve abnormalities, both signature HLHS defects. These findings show that HLHS can arise genetically in a combinatorial fashion, thus providing a new paradigm for the complex genetics of CHD.

Expression and prognostic significance of lncRNA MALAT1 in pancreatic cancer tissues

BACKGROUND

Long non-coding RNAs (lncRNAs) have been recently observed in various human cancers. However, the role of lncRNAs in pancreatic duct adenocarcinoma (PDAC) remains unclarified. The aim of this study was to detect the expression of lncRNA MALAT1 in PDAC formalin-fixed, paraffin embedded (FFPE) tissues and to investigate the clinical significance of the MALAT1 level.

METHODS

The expression of MALAT1 was examined in 45 PDAC and 25 adjacent non-cancerous FFPE tissues, as well as in five PDAC cell lines and a normal pancreatic epithelium cell line HPDE6c-7, using qRT-PCR. The relationship between MALAT1 level and clinicopathological parameters of PDAC was analyzed with the Kaplan-Meier method and Cox proportional hazards model.

RESULTS

The relative level of MALAT1 was significantly higher in PDAC compared to the adjacent normal pancreatic tissues (p=0.009). When comparing the MALAT1 level in the cultured cell lines, remarkably higher expression of MALAT1 was found in aspc-1 PDAC cells compared with the immortal pancreatic duct epithelial cell line HPDE6c-7 (q=7.573, p<0.05). Furthermore, MALAT1 expression level showed significant correlation with tumor size (r=0.35, p=0.018), tumor stage (r=0.439, p=0.003) and depth of invasion (r=0.334, p=0.025). Kaplan-Meier analysis revealed that patients with higher MALAT1 expression had a poorer disease free survival (p=0.043). Additionally, multivariate analysis indicated that overexpression of MALAT1, as well as the tumor location and nerve invasion, was an independent predictor of disease-specific survival of PDAC.

CONCLUSION

MALAT1 might be considered as a potential prognostic indicator and may be a target for diagnosis and gene therapy for PDAC.

Upregulated UHRF1 promotes bladder cancer cell invasion by epigenetic silencing of KiSS1

Ubiquitin-like with PHD and RING finger domains 1 (UHRF1), as an epigenetic regulator, plays important roles in the tumorigenesis and cancer progression. KiSS1 functions as a metastasis suppressor in various cancers, and epigenetic silencing of KiSS1 increases the metastatic potential of cancer cells. We therefore investigated whether UHRF1 promotes bladder cancer cell invasion by inhibiting KiSS1. The expression levels of UHRF1 and KiSS1 were examined by quantitative real-time PCR assay in vitro and in vivo. The role of UHRF1 in regulating bladder cancer metastasis was evaluated in bladder cancer cell. We found that UHRF1 levels are upregulated in most clinical specimens of bladder cancer when compared with paired normal tissues, and UHRF1 expression levels are significantly increased in primary tumors that subsequently metastasized compared with non-metastatic tumors. Forced expression of UHRF1 promotes bladder cancer cell invasion, whereas UHRF1 knockdown decreases cell invasion. Overexpression of UHRF1 increases the methylation of CpG nucleotides and reduces the expression of KiSS1. UHRF1 and KiSS1 expression level is negatively correlated in vivo and in vitro. Knockdown of KiSS1 promotes bladder cancer cell invasion. Importantly, forced expression of KiSS1 partly abrogates UHRF1-induced cell invasion. These data demonstrated that upregulated UHRF1 increases bladder cancer cell invasion by epigenetic silencing of KiSS1.