A promising cancer gene therapy agent based on the matrix protein of vesicular stomatitis virus.

The matrix (M) protein of vesicular stomatitis virus (VSV) plays a key role in inducing cell apoptosis during infection. To investigate whether M protein-mediated apoptosis could be used in cancer therapy, its cDNA was amplified and cloned into eukaryotic expression vector pcDNA3.1(+). The recombinant plasmid or the control empty plasmid pcDNA3.1(+) was mixed with cationic liposome and introduced into various tumor cell lines in vitro, including lung cancer cell LLC, A549, colon cancer cell CT26 and fibrosarcoma cell MethA. Our data showed that the M protein induced remarkable apoptosis of cancer cells in vitro compared with controls. Fifty micrograms of plasmid in a complex with 250 microg cationic liposome was injected intratumorally into mice bearing LLC or MethA tumor model every 3 days for 6 times. It was found that the tumors treated with M protein plasmid grew much more slowly, and the survival of the mice was significantly prolonged compared with the mice treated with the control plasmid. In MethA fibrosarcoma, the tumors treated with M protein plasmid were even completely regressed, and the mice acquired longtime protection against the same tumor cell in rechallenge experiments. Both apoptotic cells and CD8(+) T cells were widely distributed in M protein plasmid-treated tumor tissue. Activated cytotoxic T lymphocytes (CTLs) were further detected by means of (51)Cr release assay in the spleen of the treated mice. These results showed that M protein of VSV can act as both apoptosis inducer and immune response initiator, which may account for its extraordinary antitumor effect and warrant its further development in cancer gene therapy.

Vesicular stomatitis virus matrix protein gene enhances the antitumor effects of radiation via induction of apoptosis.

Vesicular stomatitis virus (VSV) matrix (M) protein can directly induce apoptosis by inhibiting host gene expression when it is expressed in the absence of other viral components. Previously, we found that the M protein gene complexed to DOTAP-cholesterol liposome (Lip-MP) can suppress malignant tumor growth in vitro and in vivo; however, little is known regarding the biological effect of Lip-MP combined with radiation. The present study was designed to determine whether Lip-MP could enhance the antitumor activity of radiation. LLC cells treated with a combination of Lip-MP and radiation displayed apparently increased apoptosis compared with those treated with Lip-MP or radiation alone. Mice bearing LLC or Meth A tumors were treated with intratumoral or intravenous injections of Lip-MP and radiation. The combined treatment significantly reduced mean tumor volumes compared with either treatment alone in both tumor models and prolonged the survival time in Meth A tumor models and the intravenous injection group of LLC tumor models. Moreover, the antitumor effects of Lip-MP combined with radiation were greater than their additive effects when compared with the expected effects of the combined treatment in vivo. This study suggests that Lip-MP enhanced the antitumor activity of radiation by increasing the induction of apoptosis.

Diluted povidone-iodine inhibits tumor growth through apoptosis-induction and suppression of SOD activity.

Povidone-iodine (PVP-I) is widely used in clinical practice as an antiseptic and flushing agent after surgery to remove a tumor. Our present study was designed to determine whether diluted PVP-I is cytotoxic to colon cancer cells and ascetic tumor cells in vitro and to examine its antitumor effects in vivo. In vitro, CT26 and H22 cells treated with different concentrations of diluted PVP-I (0-1.56 µg/ml) were analyzed using the mononuclear cell direct cytotoxicity assay (MTT) and a flow cytometry assay. In vivo, Balb/c mice injected in the abdominal cavity with CT26 cells or H22 cells were treated intraperitoneally with different concentrations of PVP-I (0-312.5 µg/mouse), cisplatin (40 mg/kg) or 5'-FU (30 mg/kg) or left untreated. In vitro, the studies demonstrated the antiproliferative and significant apoptosis-inducing effects of PVP-I in a dose- and time-dependent manner. In vivo, PVP-I significantly repressed the growth of H22 and CT26 cells in Balb/c mice compared to controls. To explore the mechanism of the antitumor effect of PVP-I, the superoxide dismutase (SOD) activity of ascites extracted from a mouse model and the supernatant of CT26 cells was detected by an SOD kit. The activity of SOD was significantly inhibited in the experimental groups. Taken together, our data suggest that PVP-I exhibits a strong inhibitory effect on tumor growth in colon cancer (CT26) and hepatoma (H22) resulting from apoptosis, both in vitro and in vivo, suggesting a new potential therapeutic approach after tumor excision surgery to colon cancer and hepatoma.

Antitumor effect of mSurvivinThr34→Ala in murine colon carcinoma when administered intravenously.

Colorectal cancer is one of the most common cancers. Survivin is strongly immunogenic in a fraction of colorectal cancer patients. The present study was designed to determine whether full-length mouse Survivin dominant-negative mutant SurvivinT34A has the antitumor activity in a murine colon carcinoma model. The complex of cationic liposome (DOTAP/Chol) to plasmid pORF9-mSurvivin T34A was administered intravenously in a mouse subcutaneous (S. C.) CT 26 tumor model. Apoptotic cells and anti-angiogenesis were evaluated by fluorescent in situ TUNEL assay and by immunohistochemistry with an antibody reactive to CD31, respectively. A 4 h 51Cr release assay was performed to determine Survivin-specific cytotoxicity. The adoptive transfer of CD8+ or CD4+ T-lymphocytes assay was to further explore the roles of immune cell subsets. We demonstrated the complex of cationic liposome (DOTAP/Chol) to plasmid pORF9--mSurvivin T34A when administered intravenously induced an efficient antitumor activity in a S. C. CT26 tumor model in mice. The main mechanism is involved in three aspects: triggering the apoptosis of tumor cells, inhibiting angiogenesis, and inducing Survivin-specific immune response. Our observations may have potential implications for the further exploration of the treatment of human colorectal cancer by intravenous delivery of dominant-negative mutant Survivin T34A.