No abstract

Summary Our recent analysis of gastric cancers using comparative genomic hybridization (CGH) revealed a novel high frequent copy number increase in the long arm of chromosome 20. Tumour-amplified kinase BTAK was recently cloned from breast cancers and mapped on 20q13 as a target gene for this amplification in human breast cancers. In the study presented here, we analysed BTAK copy-number and expression, and their relation to the ploidy pattern in 72 primary gastric cancers. Furthermore, wild-type BTAK and its deletion mutants were transfected to gastric cancers to examine changes in cell proliferation and DNA ploidy pattern. Evaluation of 72 unselected primary gastric cancers found BTAK amplification in 5% and overexpression in more than 50%. All four clinical samples with BTAK amplification showed aneuploidy and poor prognosis. Transfection of BTAK in near-diploid gastric cancers induced another aneuploid cell population. In contrast, the c-terminal-deleted mutant of BTAK induced no effect in DNA ploidy pattern and inhibited gastric cancer cell proliferation. These results suggest that BTAK may be involved in gastric cancer cell aneuploid formation, and is a candidate gene for the increase in the number of copies of the 20q, and thus may contribute to an increase in the malignant phenotype of gastric cancer.

Primary cardiac lymphoma (PCL) is a rare and usually fatal neoplasma. A case of PCL in a 78-year-old man who complained of exertional dyspnea and peripheral edema is presented. Echocardiography revealed a mass in the right atrium and a diagnosis of low-grade B-cell lymphoma was obtained with the surgically resected tumor. The lesion appeared to have originated in the right atrium and involved the right ventricle. The patient died of bronchopneumonia 8 months after the initial consultation. The present case and 39 patients with PCL reported between 1995 and 2002 were reviewed. Forty patients showed various and non-specific symptoms such as dyspnea, edema, arrhythmia and pericardial effusion. Primary cardiac lymphoma occurred slightly more often in male patients (M : F = 23:17) and in the elderly in general (mean age, 67 years), with lesions found in the following locations, listed in order of frequency: right atrium, pericardium, right ventricle, left atrium, left ventricle, and other sites. Antemortem diagnosis was obtained in 37 of the 40 patients. Thirty-seven cases were of B-cell lineage and two cases were of T-cell lineage. Complete remission was obtained in only 15 of the 40 patients. Although PCL antemortem diagnoses have been made in the majority of recent cases, the prognosis still remains poor.

To identify biologically relevant compounds in basic biology and drug discovery processes, rapid quantitative methods for elucidating protein-protein interactions have become necessary. We describe a novel optical technique for monitoring protein-protein interactions in living cells based on complementation of split luciferase fragments from click beetle (Brazilian Pyrearinus termitilluminans). A new pair of amino-terminal and carboxy-terminal fragments of the luciferase was identified using semirational library screening, demonstrating achieved markedly higher sensitivity and signal-to-background ratio. The identified fragments were applied to the study of five G-protein coupled receptors (GPCR) that interact with beta-arrestin on the plasma membrane. By generating cell lines stably expressing the GPCRs and beta-arrestin connected with the luciferase fragments, we demonstrated rapid and sensitive screening of potential chemicals that act on GPCRs using a 96-well microtiter plate format. The screening time was reduced to 5-10 min after ligand stimulation. The maximum response became more than 15-fold higher than the background signal. This luciferase complementation method also enabled accurate spatial and temporal analyses of interactions in single living cells using bioluminescence microscopy. These GPCR assays will facilitate developments of high-throughput screening systems in a multiwell plate format. Furthermore, using specific proteins of interest, the novel fragments of luciferase will provide different assay methods for the study of many intracellular signals in living cells and animals.