| Summary: | 碩士 === 國立中山大學 === 生物科學系研究所 === 93 === Hepatocellular carcinoma (HCC) is one of the most common cancerous diseases worldwide. The annual occurrences exceed one million peoples affected. Currently, the treatment modalities for HCC include surgical resection, trans-arterial embolization (TAE) and chemotherapy. However, these modalities are not completely effective, underscoring the need for development of novel therapeutic approaches.
PTEN, a tumor suppressor that antagonizes the PI3K pathway, is frequently mutated or deleted in various human cancers. Loss of PTEN occurs in 40-50% of surgical resected HCC samples and predicts poor prognosis for HCC patients, suggesting PTEN restoration may constitute
a treatment alternative for HCC. Since PTEN increased ethanol-induced cytotoxicity in hepatoma cells, PTEN gene delivery may serve as an adjuvant therapy in conjunction with ethanol TAE for HCC. In the present study, we evaluated the efficacy of PTEN gene therapy and its combination with ethanol in a syngenic Novikoff hepatoma model by implantation of N1-S1 cells into livers of Sprague Dawley rats. Adenovirus encoding PTEN (Ad-PTEN) or green fluorescent protein (Ad-GFP) was generated for gene delivery studies. The optimal condition for adenovirus vectors to infect N1-S1 cells was determined at multiplicity of infection (MOI) of 100-200. Infection of N1-S1 cells with Ad-PTEN, but not Ad-GFP, increased PTEN levels and led to 40-50% inhibition of cell proliferation via cell cycle arrest. Besides, the half maximal -inhibitory concentration (IC50) for ethanol in N1-S1 cells was determined at 6%. Combination with PTEN gene delivery further augmented the cytotoxicity of ethanol in N1-S1 cells from 40% to 70% inhibition. To evaluate the prevention efficacy of PTEN gene delivery, N1-S1 cells were infected with adenovirus vectors then implanted into livers of Sprague-Dawley rats to induce Novikoff hepatoma. Injection of PBS- or Ad-GFP-treated N1-S1 cells led to large hepatoma (with an average size of 3-4 cm) with tumor incidence of 80-90%. In contrast, injection of Ad-PTEN-infected N1-S1 cells only induced one hepatoma (with size of 0.1 cm) in six rats, suggesting that pretreatment with PTEN gene delivery effectively abolished the tumorigenic potential of N1-S1 hepatoma cells in vivo. In summary, these results validate the feasibility of PTEN gene delivery as a new promising therapeutic strategy for the treatment of orthotopic hepatoma in immune-competent rats.
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