¹Department of Urology, Herbert Irving Comprehensive Cancer Center, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA

²Department of Pathology, Herbert Irving Comprehensive Cancer Center, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA

³Department of Neurosurgery, Herbert Irving Comprehensive Cancer Center, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA

⁴Introgen Therapeutics Incorporated, Houston, Texas, TX 77030, USA

⁵Center for Mechanistic Biology and Biotechnology, Argonne National Laboratories, Argonne, Illinois, IL 60439, USA

⁶Department of Molecular Genetics and Microbiology, University of Medicine and Dentistry of New Jersey, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey, NJ 08854, USA

Correspondence to: P B Fisher, Departments of Pathology and Urology, Columbia University, College of Physicians and Surgeons, BB 15-1501, 630 West 168th Street, New York, NY 10032, USA; E-mail: pbf1@columbia.edu

^aCurrent address: Bristol Myers-Squibb, Age-related Diseases, MCDD 311 Pennington-Rocky Hill Road, Pennington, NJ 08534, USA

^bCurrent address: DGI Biotechnologies Incorporated, Molecular Biology, 40 Talmadge Road, Edison, NJ 08818, USA

^cEY Huang, MT Madireddi, RV Gopalkrishnan, M Leszczyniecka, Z-z Su and IV Lebedeva contributed equally to this manuscript

Abnormalities in cellular differentiation are frequent occurrences in human cancers. Treatment of human melanoma cells with recombinant fibroblast interferon (IFN-) and the protein kinase C activator mezerein (MEZ) results in an irreversible loss in growth potential, suppression of tumorigenic properties and induction of terminal cell differentiation. Subtraction hybridization identified melanoma differentiation associated gene-7 (mda-7), as a gene induced during these physiological changes in human melanoma cells. Ectopic expression of mda-7 by means of a replication defective adenovirus results in growth suppression and induction of apoptosis in a broad spectrum of additional cancers, including melanoma, glioblastoma multiforme, osteosarcoma and carcinomas of the breast, cervix, colon, lung, nasopharynx and prostate. In contrast, no apparent harmful effects occur when mda-7 is expressed in normal epithelial or fibroblast cells. Human clones of mda-7 were isolated and its organization resolved in terms of intron/exon structure and chromosomal localization. Hu-mda-7 encompasses seven exons and six introns and encodes a protein with a predicted size of 23.8 kDa, consisting of 206 amino acids. Hu-mda-7 mRNA is stably expressed in the thymus, spleen and peripheral blood leukocytes. De novo mda-7 mRNA expression is also detected in human melanocytes and expression is inducible in cells of melanocyte/melanoma lineage and in certain normal and cancer cell types following treatment with a combination of IFN- plus MEZ. Mda-7 expression is also induced during megakaryocyte differentiation induced in human hematopoietic cells by treatment with TPA (12-O-tetradecanoyl phorbol-13-acetate). In contrast, de novo expression of mda-7 is not detected nor is it inducible by IFN-+MEZ in a spectrum of additional normal and cancer cells. No correlation was observed between induction of mda-7 mRNA expression and growth suppression following treatment with IFN-+MEZ and induction of endogenous mda-7 mRNA by combination treatment did not result in significant intracellular MDA-7 protein. Radiation hybrid mapping assigned the mda-7 gene to human chromosome 1q, at 1q 32.2 to 1q41, an area containing a cluster of genes associated with the IL-10 family of cytokines. Mda-7 represents a differentiation, growth and apoptosis associated gene with potential utility for the gene-based therapy of diverse human cancers. Oncogene (2001) 20, 7051-7063.

melanoma differentiation associated gene-7; terminal cell differentiation; gene expression; genomic structure; IL-10 cytokine family