Tissue-specific, tumor-selective, replication-competent adenovirus vector for cancer gene therapy

We have previously described two replication-competent adenovirus vectors, named KD1 and KD3, for potential use in cancer gene therapy, KD1 and KD3 ha ve two small deletions in the EIA gene that restrict efficient replication of these vectors to human cancer cell lines, These vectors also have increa sed capacity to lyse cells and spread from cell to cell because they overex press the adenovirus death protein, an adenovirus protein required for effi cient cell lysis and release of adenovirus from the cell. We now describe a new vector, named KD1-SPB, which is the KD1 vector with the E4 promoter re placed by the promoter for surfactant protein B (SPB). SPB promoter activit y is restricted in the adult to type II alveolar epithelial cells and bronc hial epithelial cells. Because KD1-SPB has the E1A mutations, it should rep licate within and destroy only alveolar and bronchial cancer cells. We show that KD1-SPB replicates, lyses cells, and spreads from cell to cell as wel l as does KD1 in H441 cells, a human cancer cell line where the SPB promote r is active. KD1-SPB replicates, lyses cells, and spreads only poorly in He p3B liver cancer cells. Replication was determined by expression of the E4O RF3 protein, viral DNA accumulation, fiber synthesis, and virus yield. Cell lysis and vector spread were measured by lactate dehydrogenase release and a "vector spread" assay. In addition to Hep3B cells, KD1-SPB also did not express E4ORF3 in HT29.14S (colon), HeLa (cervix), KB (nasopharynx), or LNC aP (prostate) cancer cell lines, in which the SPB promoter is not expected to be active. Following injection into H441 or Hep3B tumors growing in nude mice, KD1-SPB caused a three- to fourfold suppression of growth of H441 tu mors, similar to that seen with KD1. KD1-SPB had only a minimal effect on t he growth of Hep3B tumors, whereas KD1 again caused a three- to fourfold su ppression. These results establish that the adenovirus E4 promoter can be r eplaced by a tissue-specific promoter in a replication-competent vector. Th e vector has three engineered safety features: the tissue-specific promoter , the mutations in E1A that preclude efficient replication in nondividing c ells, and a deletion of the E3 genes which shield the virus from attack by the immune system. KD1-SPB may have use in treating human lung cancers in w hich the SPB promoter is active.