This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Miki, K. Articles by Hoffman, R. M. Search for Related Content PubMed PubMed Citation Articles by Miki, K. Articles by Hoffman, R. M.

Methioninase Gene Therapy of Human Cancer Cells Is Synergistic with Recombinant Methioninase Treatment

AntiCancer, Inc., San Diego, California 92111 [K. M., W. A-R., M. X., P. J., Y. T., M. Z., A. G., R. M. H.]; Department of Surgery, University of California at San Diego, San Diego, California 92103-8220 [K. M., W. A-R., M. B., A. R. M., R. M. H.]; Department of Surgery, Yokohama City University School of Medicine, Yokohama 236-0004, Japan [T. C., H. S.]; and Department of Surgery, Graduate School of Medicine, University of Tokyo, Tokyo 113-8655, Japan [K. M., M. M.]

Results obtained over the past 40 years have demonstrated that tumor cells of all types tested have an elevated growth requirement for methioninase compared with normal cells. Recombinant methioninase (rMETase) cloned from Pseudomonas putida has been found previously to be an effective antitumor agent attributable to deprivation of the extracellular methionine source of the tumor. To degrade intracellular methioninase, we have now developed an adenoviral vector inserted with the P. putida methioninase (MET) gene (rAd-MET). The in vitro efficacy of rAd-MET was tested on the OVCAR-8 human ovarian cancer cell line, the HT1080 human fibrosarcoma cell line, and human normal fibroblasts. rAd-MET transduction of OVACAR-8 and HT1080 resulted in high levels of methioninase expression up to 10% or more of the total protein of the cells, depending on the multiplicity of infection. The IC₅₀ of rAd-MET for OVCAR-8 cells in 96-well plates was approximately 2 x 10⁶ plaque-forming units (pfu)/well. The IC₅₀ of control adenovirus (control-rAd) was 4 x 10⁷ pfu/well, 20 times higher than rAd-MET. In the presence of the IC₅₀ of 2 x 10⁶ pfu/well of rAd-MET, the addition of 0.025 units/ml of rMETase, which is 25% of the IC₅₀, resulted in a 90% inhibition of tumor cell number. This indicated that rAd-MET enhanced the efficacy of rMETase. In contrast, 2 x 10⁶ pfu/well of control-rAd in combination with 0.025 units/ml of rMETase had an efficacy of only 10% inhibition of cell number. The synergistic effect of the combination of rMETase and rAd-MET was quantitated by calculating the combination index (CI). The CIs for all combinations of rAd-MET and rMETase tested on OVCAR-8 were <0.7 with a mean of 0.5, indicating synergy. Similar synergy of rAd-MET and rMETase was seen on HT1080 human fibrosarcoma cells with a mean of 0.74. In contrast, the CIs of all combinations of rMETase and control adenovirus concentrations tested on both cell lines had a mean CI of 1, which indicated that this combination had only an additive effect. The normal fibroblasts, on the other hand, appeared relatively resistant to the MET gene because in the presence of rMETase, 2.5 x 10⁷ pfu/well of rAd-MET or control rAd had almost an identical effect on cell survival. The selectively strong synergy of rAd-MET and rMETase on cancer cells allows reduced levels of each agent to be used, thus decreasing potential side effects.

This article has been cited by other articles:

				D. Kudou, S. Misaki, M. Yamashita, T. Tamura, T. Takakura, T. Yoshioka, S. Yagi, R. M Hoffman, A. Takimoto, N. Esaki, et al. Structure of the Antitumour Enzyme L-Methionine {gamma}-Lyase from Pseudomonas putida at 1.8 A Resolution J. Biochem., April 1, 2007; 141(4): 535 - 544. [Abstract] [Full Text] [PDF]

				R. Zhao, F. E. Domann, and W. Zhong Apoptosis induced by selenomethionine and methioninase is superoxide mediated and p53 dependent in human prostate cancer cells Mol. Cancer Ther., December 1, 2006; 5(12): 3275 - 3284. [Abstract] [Full Text] [PDF]

				Z. Yang, J. Wang, T. Yoshioka, B. Li, Q. Lu, S. Li, X. Sun, Y. Tan, S. Yagi, E. P. Frenkel, et al. Pharmacokinetics, Methionine Depletion, and Antigenicity of Recombinant Methioninase in Primates Clin. Cancer Res., March 15, 2004; 10(6): 2131 - 2138. [Abstract] [Full Text] [PDF]

				D. E. Epner Can Dietary Methionine Restriction Increase the Effectiveness of Chemotherapy in Treatment of Advanced Cancer? J. Am. Coll. Nutr., October 1, 2001; 20(90005): 443S - 449. [Abstract] [Full Text]

				K. Miki, M. Xu, A. Gupta, Y. Ba, Y. Tan, W. Al-Refaie, M. Bouvet, M. Makuuchi, A. R. Moossa, and R. M. Hoffman Methioninase Cancer Gene Therapy with Selenomethionine as Suicide Prodrug Substrate Cancer Res., September 1, 2001; 61(18): 6805 - 6810. [Abstract] [Full Text] [PDF]