| Objective:Adenoid cystic carcinoma (ACC) is a rare epithelial tumor entity and comprises about 1% of all malignant tumor of the oral and maxillofacial region. Half of these tumors occur in glandular areas other than the major salivary glands, principally in the hard palate, but they also arise in the tongue andminor salivary glands. Unusual locations include the external auditory canal, nasopharynx, lacrimal,glands, breast, vulva, esophagus, cervix, and Cowper glands . It is a slowly growing but highly invasive cancer with high recurrence rate, and insensitive to chemotherapy and radiotherapy. With the development of biomedicine, molecular biology, gene therapy become a new strategy to treat adenoid cystic carcinoma.Mda-7/IL-24 is a originally novel gene, It selectively induces programmed cell death (apoptosis) in multiple human cancers without harming normal cells, enhances the sensitivity of cancer cells to radiation and chemotherapy, inhibits tumor angiogenesis and the invasion and metastasis of tumor cells. It is a hot topic of gene therapy research. Taking the advantage of Ad5 and MoMLV, hybrid adenoretroviral vector offers ease of production, high titers and efficient transduction of a wide variety of dividing and non-dividing cell types. It has low efficiency of integration, and also, can mediate long-term gene expression in vivo. It is a kind of safe and ideal vector for gene therapy.In this work, we constructed the hybrid adenortroviral vector (AdLTR2-EF1α- mda-7/IL-24) that can express mda-7/IL-24 gene,and then injected it into tumors of ACC in nude mice to assess its effects on inhibiting the growth of ACC and inducing apoptosis of ACC cells in vivo.Materials and Methods:First , we detected the expression of mda-7/IL-24 gene in SACC-83 cell lines and L-929 cell lines through RT-PCR. In vivo, thirty-three Male Balb/c-nude mice (15g-20g) were injected with SACC-83 cells (2.0×106/mouse) into the dorsal flank to create subcutaneous tumors. When the tumor's diameter reached to 5 mm-10mm , the mice were randomly divided into three groups (n = 11) and intratumorally administered with AdLTR2EF1α-mda-7/IL-24, AdLTR2EF1α-EGFP and serum-free medium respectively. The size of the tumor was measured every 2-3 days with its volume calculated (a x b2 x 0.5; a: largest diameter, b: smallest diameter). Five mice in each group were randomly sacrificed when the tumor's diameter reached to 1.5cm. For the observation of survival time, the rest mice were sacrificed when the size of the tumor (1.5cm–2.0 cm) or the mice's general condition (such as ulcer on the skin, palsy and cachexia) suggested that the animals would die within one week. The survival time of the mice was estimated based on the date when they were sacrificed. The morphology of organs and tumors were detected through hematoxylin-eosin staining and immunohistochemistry staining,and the blood of the nude mice were analyzed in order to illuminate the function and safety of AdLTR2-EF1α-mda-7/IL-24.Results:The expression of mda-7/IL-24 was detected in both transfected SACC-83 cell lines and L-929 cell lines by RT-PCR. In vivo, The tumors were observed at the dorsal flank of the mice 7 days after the SACC-83 cells were injected. By the 48th day, the average tumor volume of the mice in the AdLTR2-EF1α-mda-7/IL-24 group was 97 mm3, significantly smaller (p < 0.01) than that of the AdLTR2EF1α-EGFP group and control group. The survival time of mice treated with AdLTR2-EF1α-mda-7/IL-24 was markedly longer (p < 0.01) than that of the other two groups. Hematoxylin-eosin staining and immunohistochemistry analysis showed that: large areas of necrosis were found in the tumors of the AdLTR2EF1α-EGFP group with a great many of apoptotic cells, and the MVD were markedly smaller than that of the AdLTR2EF1α-EGFP group and control group. After injection of AdLTR2-EF1α-mda-7/IL-24, no obviously change on morphology of organs and elements of blood in nude mice were found until the mice were sacrificed.Conclusions:AdLTR2-EF1α-mda-7/IL-24 could inhibit the tumor growth of adenoid cystic carcinoma and prolong the survive time of nude mice, and has no or little effect on most normal cells and tissues , which will develop a new way to treat salivary gland tumors.
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