| Mucoepidermoid carcinoma is one of the most common malignant neoplasms of salivary glands and the high-grade mucoepidermoid carcinoma is characterized by biological aggression, high incidence of metastasis and poor prognosis. Treatment of the high-grade mucoepidermoid carcinoma is surgery with adjunct chemotherapy or radiotherapy, and sometimes it is not effect enough, especially in the cases with high-grde lesion. Tumor suppressor gene therapeutics is one of strategy for treatment of human tumors. PTEN (phosphatase and tensin homology deleted on chromosome 10) is a newly discovered tumor suppressor gene that is mutated in a variety of advanced and metastatic cancers. PTEN alteration is possibly involved in the tumor progression and metastasis. Many studies have demonstrated that over-expression of exogenous wild-type PTEN in some of human tumor cell lines, such as human glioblastoma cells ,-prostate cancer cells and breast cancer cells, lead to the suppression of cell growth. To our knowledge, study of gene therapy of mucoepidermoid carcinoma has not been reported heretofore. This study shows the effects of exogenous wild-type PTEN gene on the highly metastatic cell line M3SP2 of human mucoepidermoid carcinoma.1. Establishment of hignly metastatic mucoepidermoid carcinoma cell line which stably expresses exogenous wild-type PTEN geneImmunohistochemical staining was carried out to detect PTEN expression in 8 human cancer cell lines including mucoepidermoid carcinoma cell line MEC-1, adenoid cystic carcinoma cell line SACC83, tongue cancer cell lines Tca8113 and HSC-3, oral cheek mucosa cancer cell line BcaCDSSS, oral bottom mucosa cancer cell line HSC-2, highly metastatic mucoepidermoid carcinoma cell line M3SP2 and highly metastatic tongue cancer cell line Tb-TLP. M3SP2, Tb-TLP and BcaCD885 showed no expression of endogenous PTEN protein. Retrovirus expression vector containing wild-type PTEN gene or control vector were introduced into the M3SP2 cells by using cationic liposome, the transfected cells were selected by puromycin, and then immunohistochemical staining and western blotting were applied fordetection of exogenous PTEN expression. The exogenous PTEN expressing cells were named as M3SP2-PTEN, the control vector transfected cells as M3SP2-pBp.2. Effect of exogenous PTEN on the growth of highly metastatic mucoepidermoid carcinoma cell lineMorphological methods, cell growth test, soft agar clonogenic assay and xenograft experiment were used to evaluate the effects of exogenous PTEN on cell growth. Compared with the control cells M3SP2-pBp, exogenous PTEN expressing cells M3SP2-PTEN showed morphological changes and growth inhibition in vitro and in vivo. The M3SP2-PTEN cells , in part, revealed vacuole denaturalization, shrinkage, less microvillus, chondripsome swelling, lysosome amalgamation, and chromatin agglutination. The cell growth inhibition rate at day 7, mitosis index, clone formation inhibition rate, and in vivo xenograft growth inhibition rate of the M3 SP2-PTEN cells were 7 1 .46%, 1 6.2%o, 72.0%, and 63 .82 % , respectively.3. Mechanism of the effects of PTEN on the highly metastatic mucoepidermoid carcinoma cell lineFlow cytometry, morphological observation, in situ apoptosis asaay, telomerase activity assay and immunohistochemical staining were used to evaluate the mechanism of the effects of exogenous PTEN on the highly metastatic mucoepidermoid carcinoma cell line. Expression of wild-type PTEN gene in the highly metastatic mucoepidermoid carcinoma cell line resulted in the cell growth inhibition, which was associated with blockage of cell cycle at Gl phase, increase of cell apoptosis ( 7.5% of apoptosis in the transfected cells, 1.2% of apoptosis in control cells ), decrease of cell sensitivity to EOF, inhibition of telomerase ( by 20.6% ), decrease of protein expression of PCNA, EGF-receptor, cdk4, Bcl-2, C-myc and H-ras, and increase of protein expression of pi 6, p53 and p57Kip2.4. Effects of PTEN on adhesion, migration and invasion of highly me...
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