Research Of Lipocalin-type Prostaglandin D Synthase In Glioma

Lipocalin-type prostaglandin D synthase (LPGDS) catalyzes the isomerization of PGH2, a common precursor of various prostanoids, to PGD2. It was recently identified to be the same protein asβ-trace, which was originally discovered in 1961 as a major protein of human cerebrospinal fluid(CSF). It was found that PGDS belongs to the lipocalin family of protein, whose common function is to bind and transport small hydrophobic ligands in the plasma. LPGDS is mainly localized in the central nervous system, male genital organs of various mammals and human heart.It was found that the CSF concentration of LPGDS exceeds the blood concentration 34-fold. Saso et al determined expression of LPGDS of CSF in dementia, hydrocephalus, optic neuritis, and brain tumor, found that only in brain tumor, the concentration of LPGDS was significantly reduced when compared to control healthy samples. It is known that LPGDS protein in CSF originates exclusively from the brain. Furthermore, the expression of LPGDS is studied in brain tumor tissues by immunohistochemistry. It was found that LPGDS showed negligible immunoreactivity in malignant astrocytomas, oligodendrogliomas. It was further indicated that the expression of LGPDS decreased in brain tumor. But it is not reported for expression of LPGDS mRNA in brain tumor. It is imperative for understanding molecular basis of LPGDS change to detect expression of LPGDS mRNA in brain tumor. The glioma is most common tumor in central nervous system. The median survival time for patients with glioma remain poor, despite the use of all available treatments. Thus, there is a critical need to identify novel therapeutic targets for single and combined modality approaches to glioma tumor treatment.Hence, we investigate molecular mechanism of change and role of LPGDS in growth and progression of glioma.1. The Detection of LPGDS mRNA in Glioma by Real-time Quantitative Reverse Transcription Ploymerase Chain Reaction (FQ-RT-PCR). The LPGDS mRNA was determined with real-time quantitative RT-PCR in 35 glioma specimens and 5 healthy brain specimens. Results indicate that LPGDS mRNA expresses in 35 glioma specimens. The mean value is 0.100(0.076 inglioma(I, II), 0.015(0.012 in glioma (III, IV); In 5 normal brain specimens, the mean value is 1.020(0.174, statistic analysis indicates a distinct discrepancy(p<0.05). It was found that the expression level of LPGDS mRNA is lower in gliomas than in healthy brain tissues. In addition, statistical analysis revealed that significant difference is obtained when LPGDS mRNA values were compared with the histological grade of tumors. The expression level of LPGDS mRNA was higher in well differentiated carcinomas (gradeⅠ,Ⅱ) than those poorly differentiated carcinomas (gradeⅢ,Ⅳ). We also investigated the expression of LPGDS in cultured cell line U251, the objective being to exclude the influence of endothelial cells and infiltrated cells that could be observed in tumors and could express LPGDS. Compared to healthy brain tissues, expression of LPGDS mRNA also reduced in U251 cells. This implies that LPGDS has a potential value for diagnosis and therapy of glioma.2. Effect of LPGDS in Biological Feature of Glioma Cell Lines U251 in Vitro.LPGDS was shown to induce apoptosis in PC12 cells and kidney LLC-PK1 cells. It was well known that the apoptosis is important to homeostasis. It is very vital for growth and proliferation of cancer cells to evade apoptosis. We transfected LPGDS gene into glioma U251 cell lines. The experiments presented here show that the little difference was noted up to 4 days during which time LPGDS-transfected cultures proliferated at rates similar to that observed for the control vector transfectants. After 4 days, however, the rate of proliferation in cells transfected with LPGDS was substantially smaller than that observed in cells transfected with empty pcDNA3 vector. Colony formation reflects ability of suspension growth and proliferation of cells. Normal cells do not grow in condition of suspension. Colony form...