Systematic search for single nucleotide polymorphisms in the 5' flanking region of the human phosphodiesterase 3B gene: absence of evidence for major effects of identified polymorphisms on susceptibility to Japanese type 2 diabetes.

The activation of phosphodiesterase 3B (PDE3B) reduces free fatty acid output from adipocytes. A reduced PDE3B gene expression could lead to insulin resistance. To determine whether there are polymorphisms associated with type 2 diabetes in PDE3B gene promoter, this 5(') flanking region was isolated. The transcription initiation site was located 206bp upstream from the translation start site. Sequences of 2kb of the 5(') flanking region for 24 type 2 diabetic Japanese subjects were initially analyzed using PCR direct sequencing, and the regions including the identified polymorphisms were then examined. In 98 controls and 98 type 2 diabetic subjects, -1947T>C, -567G>A, -465G>T, -458T>C, and -1727_-1726insTCAATT were found. Only -465G>T and this insertion had more than 5% frequencies. Since a complete linkage disequilibrium existed between them, -465G>T was further analyzed, along with a previously identified +1389G>A in the coding region, in a total of 200 controls and 207 type 2 diabetic subjects. These allele frequencies were not significantly different between these two groups (controls vs. cases; -465G>T, 12.0% vs. 10.1%, P=0.435; +1389G>A, 30.3% vs. 33.3%, P=0.408). These genotype distributions were not significantly different between these two groups. The T/T genotype at -465 was rare although this frequency could be higher in type 2 diabetes (4/207 subjects) than controls (0/200 subjects). The linkage disequilibrium existed between -465G>T and +1389G>A, and the estimated haplotype frequencies defined by these SNPs were not significantly different between the cases and controls. Thus, the identified polymorphisms are unlikely to have major effects on susceptibility to Japanese type 2 diabetes.

The role of insulin-like growth factor-II in cancer growth and progression evidenced by the use of ribozymes and prostate cancer progression models.

Towards understanding the IGF system during cancer growth and progression, progressive prostate cancer models, such as SV40 large T antigen immortalized human prostate epithelial cells (P69, M2182, M2205, and M12) and LNCaP sublines (C4, C4-2, and C4-2B4), were used. IGF-II mRNA levels progressively increase as prostate cancer cells become more tumorigenic and metastatic, suggesting that IGF-II contributes in part to prostate cancer progression. The role of IGF-II in cancer cell growth was evaluated in LNCaP, PC3, and M12 prostate cancer cell lines and MCF-7 breast cancer cell line by ribozyme/antisense strategies which were previously shown to suppress endogenous IGF-II expression and cell growth in PC-3 cells [Xu et al., Endocrinol 140 (1999) 2134]. Retroviral mediated transient expression of IGF-II-specific ribozyme (RZ) caused extensive cell death. In stably cloned cell lines, both RZ and mutant ribozyme (MRZ) inhibited cancer cell growth, suggesting that antisense effects of MRZ may be sufficient for cell growth inhibition. These results confirm an important role of IGF-II in cancer cell growth and progression, and support further development of gene therapy targeting IGF-II.