Study Of Inhibition Effect Of Cantide Combined With 5-Fluorouracil On Hepatocellular Carcinoma

Objective: Telomere is the specific protein-DNA structure of karyotic chromosome end. Telomere can maintain stability of chromosome and make cells replicate normally. Generally, telomere is synthesized by telomerase. A lot of studies discovered that telomerase activity is highly expressed in all immortal cells and a vast majority of malignant tumors (85%). The specific relationship between telomerase and biological characteristics of tumors make telomerase have a important application value in the diagnosis and therapy of tumors. Telomerase could become a new target in the diagnosis and therapy of tumors. Many observations suggest that abnormality of telomeric dynamics has a profound relationship with senescence and tumorigenesis of cells. Telomerase activity plays a important role in telomeric dynamics of tumor cells. Inhibition (dedine or deletion) of telomerase activity would lead to inhibition of tumor cell growth and apoptosis; but molecular mechanism of the reversal of tumor growth by telomerase inhibition remains unclear. As a new treatment stategy for human cancer, the development of new anticancer drugs targeted against telomerase have been a hot spot in the field of oncology. Telomerase is a unique reverse transcriptase consisiting of two major components, the RNA moiety (hTER) and the catalytic subunit (hTERT). In the process of telomeric dynamics, hTER is used as a templet; but the expression of hTERT is the rate-limiting step of cell regulating telomerase activity. Becauseof specifictity in the structure and function of hTERT, antisense strategy that can kill tumor cells through inhibitting telomerase activity is a feasible approach of telomerase inhibition as cancer therapy. hTERT gene is termed hEST2. hEST2 is the target gene of antisense oligodeoxynucleotide (ASODN). Our laboratory has been studyinganti-sense nucleotide drugs for about ten years. We havemade a great progression in the field of anti-virus ASODN. Flutide (FC) and Hepatide C (HT-C) are two new ASODNs that can inhibit proliferation of influenza virus and Hepatitis C virus by antisense action which block expression of specific target genes respectively. Anti-virus effect of FC and HT-C has been tested in experimental animal models and good therapy response was observed. FC and HT-C have been patented. On the basis of FC and HT-C, our groupview telomerase as a therapeutic target for tumors and synthesize a series of specific ASODNs directed against hEST2 and systematically evaluate antitumor activity of those ASODNs to develop ASODN drugs targeted against telomerase for cancer therapy. We designed and synthesized twelve ASODNs for hEST2. After strigent in vitro and in vivo evaluation of those ASODNs, We successfully screened a ASODN termed Cantide(CT) which can effectively inhibit Hepatocellular carcinoma (HCC) growth. Cantide is directed against 3 UTR of hEST2. Target sequence (5'-3') isACTCACTCAGGCCTCAGACT, located at 3565~3584bp of hEST2 gene, ie. 20nt. Cantide was further studied in those aspects that included in vitro and in vivo evaluation of antitumor activity, molecular mechanism of antitumor action and toxicology. Evaluation of antitumor activity showed that Cantide had an exact inhibitory effect on tumor, especially on HCC. Toxicological test suggested that toxic effect of Cantide was weak or mild and experimental animal had a good tolerance to toxicity. Antitumor mechanism was that Cantide induced apoptosis of tumor cells by blocking expression of hEST2 gene and inhibitting telomerase. High metastasis model of human hepatocellular carcinoma in nude mice by orthotopical transplantation (HCM-Y89) is the first animal model of HCC in the world that is best similar to the original HCC in all kinds of biological characteristics. Especially referred to, HCM-Y89 can wholly mimic the natural invasion and metastasis of HCC patients. HCM-Y89 has generally been used in basic and clinical researches of HCC. The research item was based on prephase work of Cantide. We used HCM-Y89 to evaluate inhibitory effect of...