ABSTRACT
STGC3 is a potential tumor suppressor that inhibits the growth of the nasopharyngeal carcinoma cell line CNE2; the expression of this protein is reduced in nasopharyngeal carcinoma compared with normal nasopharyngeal tissue. In this study, we investigated the tumor-suppressing activity of STGC3 in nude mice injected subcutaneously with Tet/pTRE-STGC3/CNE2 cells. STGC3 expression was induced by the intraperitoneal injection of doxycycline (Dox). The volume mean of Tet/pTRE-STGC3/CNE2+Dox xenografts was smaller than that of Tet/pTRE/CNE2+Dox xenografts. In addition, Tet/pTRE-STGC3/CNE2+Dox xenografts showed an increase in the percentage of apoptotic cells, a decrease in Bcl-2 protein expression and an increase in Bax protein expression. A proteomic approach was used to assess the protein expression profile associated with STGC3-mediated apoptosis. Western blotting confirmed the differential up-regulation of prohibitin seen in proteomic analysis. These results indicate that overexpression of STGC3 inhibits xenograft growth in nude mice by enhancing apoptotic cell death through altered expression of apoptosis-related proteins such as Bcl-2, Bax and prohibitin. These data contribute to our understanding of the function of STGC3 in human nasopharyngeal carcinoma and provide new clues for investigating other STGC3-associated tumors.
Subject(s)
Animals , Male , Genes, Tumor Suppressor , Nasopharyngeal Neoplasms , Neoplasm Proteins , Apoptosis , Electrophoresis , Mice, NudeABSTRACT
STGC3, a novel tumor related gene, was cloned recently. The previous studies indicated that STGC3 can inhibit the proliferation of CNE2 cell line in vitro. To examine the effect of STGC3 on the tumorigenicity of CNE2 cell line and explore its mechanism in nude mice. The Tet/pTRE/CNE2-STGC3 cell line was planted under the front leg skin of nude mice and induced by doxycycline (Dox). The mRNA and protein level of STGC3 in transplanted tumor tissues were detected with RT-PCR and Western Blotting. The apoptosis ratio of the tumor cell was analyzed with flow cytometry. STGC3, Bcl-2 and Bax proteins were examined by immunohistochemistry method. The results indicated that high level of STGC3 expression can inhibit tumorigenicity of CNE2 cell line in nude mice. Tumor grew slowly, later and smaller. Cell apoptotic percentage increased. Bcl-2 protein expression was down-regulated and Bax protein expression was up-regulated in Tet/pTRE/CNE2-STGC3 cell line (P
ABSTRACT
In an attampt to establish the functional expression of STGC3 with doxycycline (Dox) induced Tet-onregulating system in human nasopharyngeal carcinoma cell line CNE2, an ideal experimental platform wasprovided for further studies of STGC3. pTet-on regulating plasmid was transfected into CNE2, and stableexpression of Tet-on was established in CNE2 through G418 select. Then the response plasmid of recombinantpTRE-STGC3 was steadily transfected into positive CNE2/Tet-on cells with hygromycin screen. Dox was used toinduce the expression of STGC3 and a cell clone sensitive to Dox was selected. The best-induced concentrationwas determined with different concentration of Dox induction. Growth curves, clone formation rate and cell cycledistribution were detected after STGC3 gene up-regulated expression with Dox induction. The growth capacity andclone formation potential of CNE2/Tet /pTRE-STGC3 was significantly suppressed, compared with the controls(P