title: Targeting inhibition of K-ras enhances Ad.mda-7-induced growth suppression and apoptosis in mutant K-ras colorectal cancer cells.
abstract: Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a cancer-specific, growth-suppressing and apoptosis-inducing gene with broad-spectrum antitumor activity. However, when administered by means of a replication-incompetent adenovirus, Ad.mda-7, several colorectal carcinoma cell lines are resistant to its antiproliferative and antisurvival effects. We have presently endeavored to determine if K-ras mutations, present in approximately 40-50% of colorectal cancers and which may mediate resistance to chemotherapy and radiotherapy, represent a predisposing genetic factor mitigating reduced sensitivity to Ad.mda-7. To suppress ras expression, three structurally different replication-incompetent adenoviral vectors were engineered that express (1) an intracellular, neutralizing single-chain antibody (scAb) to p21 ras (Ad.K-ras scAb), (2) an antisense (AS) K-ras gene (Ad.K-ras AS) or (3) both mda-7/IL-24 and a K-ras AS gene in a single bipartite virus (Ad.m7.KAS). Simultaneous inhibition of K-ras and expression of mda-7/IL-24 enhanced killing of colorectal carcinoma cells with mutated K-ras, but not with wild-type K-ras. The extent of killing depended on the degree of K-ras downregulation, with Ad.K-ras AS being generally more efficient than Ad.K-ras scAb in combination with Ad.mda-7. These findings support an effective dual-combinatorial approach for the therapy of colorectal cancers that employs a unique cancer-specific suppressor gene (mda-7/IL-24) with targeted inhibition of oncogene (ras) expression.
authors.affiliation: Department of Pathology, Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, College of Physicians and Surgeons, New York, NY 10032, USA.
authors.forename: I V
authors.initials: IV
authors.lastname: Lebedeva
authors.forename: Z-Z
authors.initials: ZZ
authors.lastname: Su
authors.forename: L
authors.initials: L
authors.lastname: Emdad
authors.forename: A
authors.initials: A
authors.lastname: Kolomeyer
authors.forename: D
authors.initials: D
authors.lastname: Sarkar
authors.forename: S
authors.initials: S
authors.lastname: Kitada
authors.forename: S
authors.initials: S
authors.lastname: Waxman
authors.forename: J C
authors.initials: JC
authors.lastname: Reed
authors.forename: P B
authors.initials: PB
authors.lastname: Fisher
mesh_terms: D000256:Adenoviridae; D000276:Adjuvants, Immunologic; D017209:Apoptosis; D015152:Blotting, Northern; D015153:Blotting, Western; D002453:Cell Cycle; D002454:Cell Differentiation; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D011905:Genes, ras / Q000502:physiology*; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D007378:Interleukins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics*; D009336:Necrosis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014161:Transduction, Genetic; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism; D000099180:Interleukin-24
chemical_list: D000276:Adjuvants, Immunologic; D007378:Interleukins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D000099180:Interleukin-24