The Expression And Regulation Of PDGF-C Variant In Renal Cell Carcinoma

Objective:Based on the previous identification of PDGF-Cb in our group,we investigated the expression,regulation and the significance of PDGF-C and PDGF-Cb in clear cell renal cell carcinoma and the matched normal tissue,and study the role which PDGF-C and PDGF-Cb may play in the tumorigenesis of renal cell carcinoma.Methods:Our group identified PDGF-Cb through bioinformatics.Western blotting was used to detect the expression of protein,subcellular localization was made through immunofluorescence analysis.Using semi-quantitative reverse transcriptionpolymerase chain reaction(RT-PCR) method,the expression of PDGF-C and PDGF-Cb in 30 clear cell renal cell carcinoma tissues and the matched adjacent normal tissues were detected.The relationship between the expression of PDGF-C and PDGC-Cb was researched too.The impact of Cisplatin on the mRNA expression of PDGF-C and PDGF-Cb in the renal cell line was researched too.Date obtained were statistically analyzed by software package SPSS11.5.Statistical methods paired t-test was used to evaluate the difference of the expression of PDGF-C and PDGF-Cb mRNA in tumor tissues and the matched normal tissues.Results:1 The PDGF-Cb was identified from the human PDGF-C gene,it consisted of seven exons,and differed from the original PDGF-C mRNA only by the presence of exon 2a.PDGF-Cb encodes a shorter protein of 182 amino acids lacking the signal peptide and CUB domain,but maintaining 100%identity to the C-terminal part(including the entire GFD) of PDGF-C.The predicted molecular mass of PDGF-Cb is 20.6 kDa. 2 The PDGF-Cb variant is highly conserved in mammalian species,the two PDGF-C variants were found to be coexpressed in all adult and fetal tissues examined,with some differences in their relative amount.Compared with the matched normal tissues, the expression of PDGF-C mRNA in the tumor tissues increased,as well as the PDGF-C/-Cb ratio.3 The expression of the recombinant PDGF-Cb in COS-7 cells showed that PDGF-C and PDGF-Cb are both located in the endoplasmic reticulum(ER),heterodimerization of PDGF-C and PDGF-Cb can formed in cotransfected COS-7 cells.4 On the mRNA level,Cisplatin down-regulated the expression of PDGF-C and PDGF-Cb,and the effect on the latter was dose-dependently.Conclusion:1 The spliced variant of human PDGF-C,PDGF-Cb,generated by insertion of a novel 61 nucleotides long exon,named exon 2a in intron 1 of PDGF-C.2 The PDGF-Cb variant is highly conserved in mammalian species,with 93-98% identity with human exon 2a in different species.This supports the significance of the finding and further suggests that the variant may be a useful tool in the elucidation of physiological roles of PDGF-C.3 PDGF-Cb is located in cell and can't be secreted out of the cell,but it could form heterodimerization with PDGF-C in cell,impacting the secreting of PDGF-C. PDGF-Cb showed reversely regulation of the secretion of PDGF-C,and this might be involved in RCC tumorigenesis.4 The effects of down regulation of PDGF-C and -Cb caused by Cisplatin provide a potential pathway for the research of the tumorigenesis of renal cell carcinoma.