Gastric cancers show high frequency of DNA aneuploidy, a phenotype of chromosomal instability. It is suggested that the abnormal spindle assembly checkpoint is involved in DNA aneuploidy, but the underlying mechanism is still unclear. We studied the mechanism by assessing the expression of BUBR1 in gastric cancer. The DNA ploidy patterns of 116 gastric cancer samples obtained from the Department of Surgery and Science at Kyushu University Hospital were analyzed. Of those, DNA aneuploidy was seen in 70 (60.3%) cases of gastric cancer. The expression of BUBR1 was studied by immunohistochemistry in 181 gastric cancer samples and by real-time RT-PCR in several gastric cancer cell lines. Ninety-one (50.3%) cases had high expression of BUBR1 and those cases correlated significantly with DNA aneuploidy (P < 0.05). Also high expression of BUBR1 cases had significant correlation with deep invasion, lymph node metastasis, liver metastasis, and poor prognosis. In gastric cancer cell lines, high expression of BUBR1 had a significant relationship with DNA aneuploidy (P < 0.05). Then, gastric cancer cell lines MKN-28 and SNU-1 were transfected with fulllength BUBR1 to observe the significance of the change in BUBR1 expression. Enforced expression of BUBR1 resulted in changes to the ploidy pattern and high Ki-67 expression. Collectively, our clinical and in vitro data indicate that high expression of BUBR1 may be one of causative factors for the induction of DNA aneuploidy and progression of gastric cancer. (Cancer Sci 2010; 101: 639-645)

A 72-year-old man was diagnosed with essential thrombocythemia (ET) and was treated with hydroxyurea for approximately 5 years. He was well until April 2007. In May 2007, a slight fall in hemoglobin levels was found. In June 2007, an upper endoscopy performed to investigate the cause of anemia showed multiple polypoid lesions in the body of the stomach. A gastric biopsy showed a diffuse infiltration of very immature cells. Several additional immunohistochemical staining showed that the cells were positive for CD13, CD34, CD117, and HLA DR, but negative for myeloperoxidase, CD42b, glycophorin, B cell marker, T cell marker, cytokeratin and desmin. We finally diagnosed the condition as myeloid sarcoma. Subsequently, the patient's ET transformed into acute myeloid leukemia. To our knowledge, this is an exceedingly rare event involving a patient with essential thrombocythemia.