Combination Treatment with Intravesical Interferon-Alpha Gene Therapy and Oral Pan-ErbB Receptor Family Blocker Improves Survival in Mice with Bladder Cancer.

PURPOSE: Intravesical interferon-alpha (IFNα) gene therapy has shown promise in treating BCG-unresponsive non-muscle invasive bladder cancer (NMIBC). Ongoing work in our lab aims to further improve its treatment efficacy by identifying resistance mechanisms and deploying targeted combination treatment strategies.

EXPERIMENTAL

DESIGN

We performed end-tumor RNA-seq analysis of MB49 murine tumors treated with IFNα gene therapy, identifying the ErbB pathway as a resistance mechanism. We consequently hypothesized that a combination treatment involving an ErbB pathway blocker and IFNα could yield improved outcomes. MB49 cells were treated in vitro with lentiviral IFNα (LV-IFNα) gene therapy, with/without Afatinib, a pan-ErbB inhibitor, and cell viability and migration assays were performed. Next, in vivo studies were conducted in the syngeneic MB49 orthotopic murine bladder cancer model. The mice were randomized into 5 treatment groups (n=10 each): saline (Ctrl), LV-Ctrl, oral Afatinib monotherapy, intravesical LV-IFNα monotherapy, and the experimental intravesical LV-IFNα + oral Afatinib combination therapy. Overall survival (OS) and drug toxicity were assessed.

RESULTS

Combination therapy significantly reduced MB49 cell viability in vitro compared to all other treatment conditions (mean relative ATPase activity at 72 h for the combination treatment was 4%, compared to 100%, 26%, and 28% for Ctrl, LV-IFNα, and Afatinib, respectively, p<0.001). This additive effect on cell viability appeared to be driven by a combination of early-cytostatic and late-cytolytic effects. The combination treatment also markedly inhibited cell migration (mean migrated cells/10x Boyden chamber assay at 36 h were: 92.3 for the combination therapy and 631.0, 600.4, and 270.3 for Ctrl, LV-IFNα, and Afatinib, respectively, p<0.001). Finally, the in vivo studies demonstrated improved OS with combination therapy (median OS was 49 d in the combination group vs 15, 29, and 26 d in Ctrl, LV-IFNα, and Afatinib groups, respectively, Log-rank p<0.001). No mice in the combination therapy group died of drug toxicity.

CONCLUSIONS

Our preliminary findings suggest that the ErbB pathway may serve as a clinically significant resistance mechanism to intravesical IFNα gene therapy, and when targeted concurrently, may improve treatment efficacy.