Suppression of osteosarcoma in vitro by coexpression of antisense VEGF165 cDNA and thymidine kinase gene / 中华病理学杂志

<p><b>OBJECTIVE</b>To investigate the effect of VEGF expression in osteosarcoma cell line and the target killing effect of HSV1-TK/GCV system on transfected osteosarcoma cells under hypoxia conditions.</p><p><b>METHODS</b>Eukaryotic expression plasmid with HRE promoter was constructed to express the antisense VEGF165 cDNA and Hygromycin phospho-transferase-thymidine kinase (HyTK) fusion gene. The recombinant vectors were then transfected into osteosarcoma cell line MG63 with lipofectin mediated gene transfer methods. PCR and RT-PCR were used to confirm the presence and expression of TK gene. The sensitivity of transfected cells to GCV and "bystander effect (BSE)" of HSV1-TK/GCV system under normoxia or hypoxia conditions were measured by MTT assay and mixed co-culture experiment. The expression of VEGF protein was detected by ELISA under hypoxia condition. Cell cycle phase distribution was determined by flow cytometry. In addition, electromicroscopy was used to document ultrastructural alterations.</p><p><b>RESULTS</b>The eukaryotic expression vector pBI-HRE-AsVEGF165 -HyTK was constructed successfully. The transfected cell line MG63TV was established and confirmed by PCR and RT-PCR of the presence of transgene and its mRNA expression. GCV was toxic to transfected cells in a concentration-dependent manner. The sensitivity to GCV toxicity was 100 times higher under hypoxia condition than that under normoxic condition. The mixed culture experiments showed that the "bystander effect" was enhanced significantly under hypoxia condition. VEGF expression of transgene cells under hypoxia condition decreased 50% compared to that of normal condition. Under hypoxia and GCV, DNA synthesis of MG63TV cells was inhibited along with an increase of cells at G0 approximately G1 phase, apoptosis and necrosis.</p><p><b>CONCLUSIONS</b>Antisense VEGF expression driven by HRE promoter in combination with hypoxia can provide a target inhibition of VEGF expression in human osteosarcoma cells, with an enhanced selective killing effect and BSE of the HSV-TK/GCV system. The double-gene co-expression system in study provides experimental basis for therapy against osteosarcoma by a synchronous antiangiogenic and suicide gene approach.</p>

The role of CD44 in the proliferation, adhesiveness and invasiveness of osteosarcoma cell lines / 中华病理学杂志

<p><b>OBJECTIVE</b>To study the influence of CD44 a cell-matrix adhesion molecule on the proliferation, adhesiveness and invasiveness of osteosarcoma cell lines, in order to investigate the growth and invasion mechanism of osteosarcoma.</p><p><b>METHODS</b>Three osteosarcoma cell lines MG-63, HOS and U2-OS were routinely cultured. Flow cytometry and Western blot analysis were used for detecting the positive rates and relative amount of CD44 protein in the three cell lines. RT-PCR method was also used to compare the differences in the expression of CD44 mRNA among the 3 cell lines. Then, MTT method, adhesion detection, and Microcon-migration assay were used to detect the changes of the cells' proliferation rate, adhesive and invasive abilities after blocking the role of CD44 by using a special neutralizing antibody.</p><p><b>RESULTS</b>The results of flow cytometry showed that the percentage of CD44 positive cells were both over 99% in HOS and U2-OS, while that in MG-63 was only (2.10 +/- 0.46)%. The average fluorescence density of CD44 in HOS was significantly higher than in U2-OS. Western blot also showed that the relative content of CD44 protein in HOS was notably higher than that in U2-OS, while CD44 was negatively expressed in MG-63. The expression of CD44 mRNA was significantly lower in MG-63 than in both HOS and U2-OS, which were consistent with the expression of CD44 protein. The proliferation rates and adhesive abilities of MG-63 and HOS have no significant difference, but both were significantly higher than that of U2-OS. The invasive abilities of HOS was dramatically higher than MG-63 and U2-OS. After the role of CD44 was blocked by anti-CD44 neutralizing antibody, the proliferation rates of the 3 cell lines did not change significantly. While the HOS and MG-63 adhesion indices decreased dramatically (P < 0.05), the invasive abilities of HOS and U2-OS also decreased notably (P < 0.01).</p><p><b>CONCLUSIONS</b>CD44 could promote the adhesiveness and invasiveness of osteosarcoma cell line HOS. CD44 may take part in promoting the process of U2-OS invasion and the adhesion of MG-63. On the other hand, CD44 could not affect the osteosarcoma cell proliferation rates.</p>

Targeted inhibition of vascular endothelial growth factor (VEGF) expression in human osteosarcoma cell line by antisense VEGF165 cDNA promoted by hypoxia reaction element / 中华病理学杂志

<p><b>OBJECTIVE</b>Utilizing the hypoxia inducible factor 1/hypoxia reaction element (HIF-1/ HRE) gene regulation system to construct antisense vascular endothelial growth factor (VEGF165) cDNA eukaryotic expression vector promoted by HRE, and investigate its targeted inhibiting VEGF expression of osteosarcoma cells in hypoxia environment.</p><p><b>METHODS</b>Eukaryotic expression plasmid with HRE promoter was constructed containing luciferase reporter gene and antisense VEGF165 cDNA by using PCR and recombinant DNA techniques. The recombinant vectors were transfected into osteosarcoma cells with lipofectin method. Hypoxia-inducible reporter gene expression was determined by liquid scintillation analyzer and the expression of VEGF protein was detected by ELISA method.</p><p><b>RESULTS</b>The eukaryotic expression plasmid containing antisense VEGF165 and luciferase promoted by HRE was constructed successfully. After being transferred into MG63 cells, luciferase expression was increased 3.5 x 10(2) times and VEGF protein expression decreased 45% under hypoxia condition.</p><p><b>CONCLUSION</b>Antisense VEGF165 cDNA expression, efficiently realized by HRE promoter under hypoxia condition, provides an experimental basis for targeted antiangiogenesis of tumors.</p>