The Role of Genotyping in Diagnosing Cardiac Channelopathies

Genetic testing for long QT syndrome and the category of cardiac ion channelopathies

Cardiac ion channel mutational analysis is a category of genetic testing used in clinical practice for determining the status of long QT syndrome, short QT syndrome, catecholaminergic polymorphic ventricular tachycardia, and Brugada syndrome genes in blood, saliva, or tissue from patients and family members at risk for cardiac events such as syncope and sudden death. Such testing is most informative following careful phenotypic characterization. Individuals with ion channelopathies may benefit from prevention (avoidance of triggers and predisposing drugs) and treatment (e.g., beta blocker therapy, implantable cardioverter-defibrillator (ICD) placement) modalities.

Deregulation of 2 potassium channels in pancreas adenocarcinomas: implication of KV1.3 gene promoter methylation

OBJECTIVES

The aim of this study was to examine expression of 2 potassium (K) channels in pancreatic adenocarcinoma.

METHODS

The immunohistochemical and mRNA expression of GIRK1 (G-protein inwardly rectifying K channel 1) and KV1.3 channel (voltage-dependent K channel) was studied in 55 and 18 adenocarcinomas and 33 and 8 normal pancreas specimens, respectively. The methylation status of KV1.3 promoter was studied by methyl-specific polymerase chain reaction in 33 pancreatic adenocarcinomas. The results were correlated with the patients' prognosis.

RESULTS

GIRK1 was highly expressed in 80% (44/55) of adenocarcinoma samples versus 57.6% (19/33) of normal samples (P=0.03), as confirmed by reverse transcriptase-polymerase chain reaction results (P=0.007). KV1.3 expression was decreased in pancreatic adenocarcinomas compared with normal tissue (7.3% vs 39.4%; P=0.0005). KV1.3 down-expression was associated with metastatic tumors (P=0.018). KV1.3 promoter methylation was observed in 69.7% (22/33) of adenocarcinomas.

CONCLUSION

This is the first report of deregulation of 2 K channels in pancreatic adenocarcinoma. GIRK1 was highly expressed in pancreatic adenocarcinomas, corresponding to its role in cell proliferation. Methylation of KV1.3 gene promoter could explain the decrease of KV1.3 expression in adenocarcinomas. New therapeutic agents, such as DNA methylation inhibitors, could be useful against this dramatic cancer.