Latent membrane protein-1 of Epstein-Barr virus induces the expression of B-cell integration cluster, a precursor form of microRNA-155, in B lymphoma cell lines.

miR-155, a microRNA, and its precursor form, B-cell integration cluster (BIC), are involved in tumor growth. Epstein-Barr virus (EBV)-associated malignancies are categorized into three types, based on their latent gene expression pattern: latency I, II, and III. In the present study, we found that infection with EBV increased the expression of BIC; in addition, substantial expression of BIC/miR-155 was detected in latency III-, but not in latency I-type cells. In comparison, latent membrane protein-1 (LMP1) was expressed in latency III-type cells. When LMP1 was over-expressed, BIC expression increased, indicating LMP1 mediates BIC expression. LMP1 is a membrane-associated protein known to activate signaling pathways. With the use of pathway inhibitors, we found that LMP1-induced strong BIC expression, primarily through NF-kappaB and p38/MAPK pathways. These results suggest that BIC/miR-155 play a role in lymphomagenesis through NF-kappaB and p38/MAPK pathways in response to activation by EBV LMP1.

Effects of soy protein and isoflavones on insulin resistance and adiponectin in male monkeys.

Isoflavones may influence insulin action by means of their well-known receptor-mediated estrogenic activity. However, isoflavones also bind to peroxisome proliferator-activated receptors (PPARs) that are strongly associated with insulin action. Soy protein with its isoflavones has previously been shown to improve glycemic control in diabetic postmenopausal women and to improve insulin sensitivity in ovariectomized monkeys. The purpose of the current report was to extend our studies of dietary soy protein to male monkeys and determine effects of the soy isoflavones on insulin resistance. Two studies are reported here. Study one involved 91 male monkeys consuming 3 diets differing only by the source of protein (casein-lactalbumin, soy protein with a low isoflavone concentration, or soy protein with a high isoflavone concentration). Intravenous glucose tolerance tests were done, and plasma adiponectin and lipoprotein concentrations were determined after 25 months of study. Samples of visceral fat were obtained at 31 months for assessment of adiponectin and PPARgamma expression. The second study involved 8 monkeys in a Latin-square design that compared the effects of diets with casein/lactalbumin, soy protein with a high isoflavone concentration, or soy protein that was alcohol-washed to deplete the isoflavones. After 8 weeks of treatment, insulin sensitivity and plasma lipoproteins were assessed. At 10 weeks, a biopsy of the skeletal muscle was performed for determination of insulin receptor, PPARalpha, and PPARgamma content. The major findings were that consumption of isoflavone-containing soy protein dose-dependently increased insulin responses to the glucose challenge and decreased plasma adiponectin, whereas isoflavone-depleted soy protein decreased body weight and had no effect on plasma adiponectin concentrations. Muscle PPARalpha and gamma expression was also increased with the isoflavone-depleted soy relative to either casein or soy protein containing the isoflavones. Further studies are needed to determine the mechanisms involved in these effects of a high-soy isoflavone diet and to optimize dietary isoflavone content for maximal health benefits in male subjects.

ATR alterations in Hodgkin's lymphoma.

Hodgkin's lymphoma (HL) is characterized by the presence of neoplastic Hodgkin and Reed-Sternberg cells (HRSC) in a background of inflammatory cells. Free radicals and oxidative stress generated in the inflammatory lesions could cause DNA damage, thus providing a basis for lymphomagenesis. Ataxia-telangiectasia mutated (ATM) and Rad3-related (ATR) genes are responsive genes for DNA damage, therefore the potential involvement of the ATR gene in HL pathogenesis was examined in 8 HL cell lines and 7 clinical cases. ATR alterations were detected in 6 out of 8 HL lines. Most aberrant transcripts observed were heterozygous deletions, which may have resulted from aberrant splicing. ATR aberrant transcripts were also detected in 3 out of 7 clinical cases. Three alterations, del exon 4, deletion exon 29-34 and insertion of 137 bp in exon 46/47 were commonly observed in both cell lines and clinical samples. HL cells with ATR alterations except del exon 4 showed a delay/abrogation in repair for DNA double-strand breaks (DSBs) and single-strand break (SSB) as well as exhibiting a defect in p53 accumulation. These findings suggested the role of ATR gene alterations in HL lymphomagenesis.

Condensin mutations and abnormal chromosomal structures in pyothorax-associated lymphoma.

Transfer of genetic information during mitosis is accurately conducted by proper condensation and segregation of chromosomes, for which condensins play a central role. Both condensin I and II have common structural maintenance of chromosomes subunits, named hCAP-C and hCAP-E. Pyothorax-associated lymphoma (PAL) is a non-Hodgkin's lymphoma developing in the pleural cavity of patients with long-standing pyothorax. Mutations of hCAP-C and hCAP-E were investigated in 24 leukemia-lymphoma cell lines including eight PAL cell lines, and their influences in chromosome morphology were evaluated. Heterozygous point mutations within hCAP-C were found in two PAL cell lines and corresponding tumor samples (OPL-3 and OPL-7). Deletion of exon 24 within hCAP-E and a point mutation at the donor splice site of intron 24 were detected in OPL-5 and original tumor samples. OPL-5 showed an extensive reduction in expression of not only hCAP-E but also hCAP-C proteins. OPL-5 occasionally showed the chromosome bridge in anaphase and telophase, indicating that segregation is not accurate. OPL-7 showed reduced hCAP-C protein expression, abnormality in chromosome length and width, and abnormal aggregates of hCAP-C protein. These findings indicated that condensin gene alteration might play a role in genome instability, which accelerates the accumulation of other gene alterations in PAL.

Telomere dysfunction and inactivation of the p16(INK4a)/Rb pathway in pyothorax-associated lymphoma.

Previous studies have indicated that genome instability is involved in the lymphomagenesis of pyothorax-associated lymphoma (PAL), which develops in patients with a long-standing history of pyothorax. One of the well-known causes of genome instability is telomere dysfunction. In the present study, the condition of telomeres was analyzed in the cell lines and clinical samples from PAL. Telomere length (TL) in PAL cell lines was extremely short (<4.5 kbp). TL in tumor samples was broad in range, and shorter than that in the peripheral blood leukocytes from the matched patients. Three of five PAL cell lines showed frequent loss of telomere signals (telomere erosion); however, telomerase activity in PAL cell lines was similar to that in Burkitt lymphoma cell lines. Rb expression was detected in three PAL cell lines and four of 15 clinical samples, respectively. Rb protein expressed in three PAL cell lines was heavily phosphorylated, indicating that function of Rb protein was suppressed. p16(INK4a) expression was not detected in either cell lines or clinical samples. The promoter region in p16(INK4a) was heavily methylated in all cell lines as well as the clinical samples. Inactivation of the p16(INK4a)/Rb pathway may allow continuous cell division and critical telomere shortening, which induce genome instability, finally leading to malignant transformation. Taken together, telomere dysfunction and inactivation of the p16(INK4a)/Rb pathway might play a role for PAL development.