Lentiviral interferon with immune checkpoint blockade: A novel method for gene therapy in bladder cancer.

Abstract

33 Background: Gene therapy for bladder cancer (BLCA) is rapidly evolving. We reported that intravesical adenoviral interferon-alpha (Ad-IFNα) produced a complete response in 35% of patients with BCG-unresponsive BLCA enrolled in a Phase II trial. Lentivirus (LV) is another potential vector for intravesical delivery of IFNα. LV can infect non-dividing cells and integrate into the host’s genome, making it more efficient gene delivery vectors. As treatment with IFN upregulates checkpoint inhibitors, we also wanted to investigate the role of checkpoint inhibitors with and without IFN gene therapy. Methods: Murine BLCA cell lines were transduced in-vitro with LV-IFNα (MOI 2:1). IFNα levels were measured by ELISA. Cell viability was assessed using Trypan blue dye exclusion. qPCR was used to identify expression of IFNα target genes. A LV-βGalactosidase reporter construct was delivered intravesically, and urinary IFNα levels were measured in mice treated with LV-IFNα or control virus to assess gene transfer. To assess survival benefit, the MB49 intravesical tumor model and p53+/- C57/B6 mouse model were employed. We also assessed the role of combination therapy with immune checkpoint blockade using PD1 antibody using our MB49 intravesical model. Results: Efficient LV-IFNα transduction of BLCA cells resulted in increased expression of IFNα and its target genes and reduced cell viability vs. controls (p<0.001). Mechanistically, TRAIL dependent cytotoxicity in the LV-IFNα cells was rescued by Caspase8 inhibition. Urinary IFNα levels were elevated in mice receiving LV-IFNα compared with control virus. Overall survival improved in the MB49 model and BBN model in treated mice. LV-IFN induced intratumoral CD8+ T cell infiltration, high expression of PD-L1, and inhibited angiogenesis in BBN model whereas in the MB49 tumor response was mediated by TRAIL. Combination therapy with PD1 resulted in further improved survival. Conclusions: LV-IFNα effectively upregulated IFNα target genes, was cytotoxic to murine BLCA cells, and improved the survival in mouse models. Combining it with PD1 therapy appears to further improve survival.