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

Area of Science:

• Oncolytic virotherapy
• Gene therapy vectors
• Adenovirus engineering

Background:

• Replication-competent adenovirus vectors (KD1, KD3) were developed for cancer gene therapy, featuring E1A gene deletions for cancer cell specificity and enhanced cell lysis/spread via adenovirus death protein.
• These vectors exhibit limited replication in normal cells but efficient replication in cancer cells, with improved oncolytic properties.

Purpose of the Study:

• To engineer a novel replication-competent adenovirus vector, KD1-SPB, with enhanced tumor-specific targeting for cancer gene therapy.
• To evaluate the replication, cell lysis, and spread capabilities of KD1-SPB in cancer cell lines with and without surfactant protein B (SPB) promoter activity.
• To assess the in vivo antitumor efficacy of KD1-SPB in xenograft models of human lung and liver cancer.

Main Methods:

• Development of the KD1-SPB vector by replacing the E4 promoter of the KD1 vector with the SPB promoter, which is active in lung epithelial cells.
• In vitro assessment of vector replication (E4ORF3 protein expression, viral DNA, fiber synthesis, virus yield), cell lysis (lactate dehydrogenase release), and cell-to-cell spread in H441 (SPB-positive) and Hep3B (SPB-negative) cancer cell lines.
• In vivo evaluation of KD1-SPB antitumor activity by intratumoral injection into H441 and Hep3B tumor xenografts in nude mice, comparing efficacy to the parental KD1 vector.

Main Results:

• KD1-SPB demonstrated robust replication, cell lysis, and spread in H441 lung cancer cells, comparable to the KD1 vector, due to active SPB promoter.
• Replication and spread of KD1-SPB were significantly impaired in Hep3B liver cancer cells and other cancer cell lines lacking SPB promoter activity.
• In vivo, KD1-SPB significantly suppressed H441 tumor growth in mice, similar to KD1, but had minimal effect on Hep3B tumors, confirming promoter-driven tumor specificity.
• The engineered vector exhibited three safety features: tissue-specific promoter, E1A mutations for replication restriction, and E3 gene deletion for immune evasion.

Conclusions:

• The E4 promoter of replication-competent adenovirus vectors can be successfully replaced with a tissue-specific promoter, such as SPB, to achieve targeted oncolytic activity.
• KD1-SPB exhibits promising potential for the treatment of human lung cancers where the SPB promoter is active, offering a targeted and potentially safer gene therapy approach.
• The engineered safety features of KD1-SPB enhance its potential therapeutic application by improving tumor specificity and reducing off-target effects.