Aim: To evaluate the in vivo antitumor effects of Cantide and the combined effect with 5-fluorouracil. Methods: An in situ human hepatocellular carcinoma model was established in mice livers orthotopically. Drugs were administered intravenously and tumor sizes were monitored with calipers. Plasma alpha-fetoprotein (AFP) were detected by radiation immunoassay. Morphology of tumors was evaluated by hematoxylin-eosin (H&E) staining of histological sections. Human telomerase reverse transcriptase (hTERT) protein levels were detected by Western blotting. Results: Cantide significantly inhibit in situ human hepatocellular carcinoma growth in mice with a 75 and 50 mg kg~(-1) d~(-1) administration of Cantide compared to the saline group in a dose-dependent manner, which included injecting Cantide 25 mg kg~(-1) d~(-1)-75 mg kg~(-1) d~(-1) by iv for 20 d after surgically removing the tumor in liver. Cantide was also found to prevent tumor recurrence in the liver and metastasis in the lung, showing a dose-dependent response. When Cantide was administered by iv combined with 5-fluorouracil, it resulted in a significant reduction in tumor growth compared to either agent alone treatment group. After the treatment with Cantide alone or combined with 5-fluorouracil, plasma AFP concentration decreased in a dose-dependent manner. Conclusion: These results demonstrated that Cantide was an effective antitumor antisense oligonucleotide in vivo and has the potential to be developed into a clinical anti-cancer drug. Aim: To evaluate the in vivo antitumor effects of Cantide and the combined effect with 5-fluorouracil. Methods: An in situ human hepatocellular carcinoma model was established in mice livers orthotopically. Drugs were administered intravenously and tumor sizes were monitored with calipers. Plasma alpha Morphology of tumors was evaluated by hematoxylin-eosin (H & E) staining of histological sections. Human telomerase reverse transcriptase (hTERT) protein levels were detected by Western blotting. Results: Cantide significantly inhibit in situ human hepatocellular carcinoma growth in mice with a 75 and 50 mg kg -1 d -1 administration of Cantide compared to the saline group in a dose-dependent manner, which included injectable Cantide 25 mg kg -1 ) d ~ (-1) -75 mg kg ~ (-1) d ~ (-1) by iv for 20 d after surgically removing the tumor in liver. Cantide was also found to prevent tumor recurrence in the liver and metastasis in the lung, showi When cantide was administered by iv combined with 5-fluorouracil, it resulted in a significant reduction in tumor growth compared to either agent alone treatment group. After the treatment with Cantide alone or combined with 5-fluorouracil, plasma Conclusion: These results in that cantide was an effective antitumor antisense oligonucleotide in vivo and has the potential to be developed into a clinical anti-cancer drug.