Methioninase/selenomethionine and bcl-2

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Methioninase gene therapy with selenomethionine induces apoptosis in bcl-2-overproducing lung cancer cells

Norio Yamamoto1,2,3, Anshu Gupta1,2, Mingxu Xu1, Kenji Miki1,4, Yoshihide Tsujimoto5, Hiroyuki Tsuchiya3, Katsuro Tomita3, A R Moossa2 and R M Hoffman1,2

1AntiCancer, Inc., 7917 Ostrow Street, San Diego, California 92111, USA

2Department of Surgery, University of California at San Diego, 200 West Arbor Drive, San Diego, California 92103-8220, USA

3Department of Orthopedic Surgery, Graduate School of Medicine, Kanazawa University, 13-1 Takaramachi, Kanazawa 920-8641, Japan

4Department of Surgery, Graduate School of Medicine, University of Tokyo, Japan

5Graduate School of Medicine, Osaka University, Japan

Correspondence to: RM Hoffman, AntiCancer, Inc., 7917 Ostrow Street, San Diego, CA 92111, USA. E-mail: all@anticancer.com.

Abstract

We have previously shown that the toxic pro-oxidant methylselenol is released from selenomethionine (SeMET) by cancer cells transformed with the adenoviral methionine ,-lyase (methioninase, MET) gene cloned from Pseudomonas putida. Methylselenol damaged the mitochondria via oxidative stress, and caused cytochrome c release into the cytosol thereby activating caspase enzymes and thereby apoptosis. However, gene therapy strategies are less effective if tumor cells overexpress the antiapoptotic mitochondrial protein bcl-2. In this study, we investigated whether rAdMET/SeMET was effective against bcl-2-overproducing A549 lung cancer cells. We established two clones of the human lung cancer A549 cell line that show moderate and high expression levels of bcl-2, respectively, compared to the parent cell line, which has very low bcl-2 expression. Staurosporine-induced apoptosis was inhibited in the bcl-2-overproducing clones as well as in the parental cell line. In contrast to staurosporine, apoptosis was induced in the bcl-2-overproducing clones as well as the parental cell line by AdMET/SeMET. Apoptosis in the rAdMET-SeMET-treated cells was determined by fragmentation of nuclei, and release of cytochrome c from mitochondria to the cytosol. A strong bystander effect of AdMET/SeMET was observed on A549 cells as well as the bcl-2-overproducing clones. rAdMET/SeMET prodrug gene therapy is therefore a promising novel strategy effective against bcl-2 overexpression, which has blocked other gene therapy strategies.

Cancer Gene Therapy (2003) 10, 445-450. doi:10.1038/sj.cgt.7700587

Keywords

MET-gene therapy; prodrug; suicide therapy; methyl selenol; A549