ID: 2167

• Title:
  PD-1 peptide gene therapy for melanoma therapy
  
  Authors:
  

  Heller1, Loree C, University of South Florida
  Shi, Guilan, University of South Florida
  Sales Conniff, Amanda, University of South Florida
  Singh, Julie, University of South Florida
  Mannarino, Samantha, University of South Florida
  Heller, Richard 

  
  
  Abstract:
  Background and objectives of the study: IL-12 gene electrotransfer (GET) delivery is highly effective in inducing long-term, complete regression in mouse and human melanoma and other solid tumors. Therapeutic efficacy is enhanced by immune checkpoint inhibitors, and the combination of IL-12 plasmid GET (pIL-12 GET) and anti-programmed cell death protein 1 (PD-1) monoclonal antibodies is in late-stage clinical trials. In this study, we designed peptides and plasmids encoding the extracellular domain of mouse PD-1 and the mouse homologs of the pembrolizumab and nivolumab programmed cell death 1 ligand 1 (PD-L1) binding regions. We hypothesized that intratumor autocrine/paracrine peptide expression would block PD-1/PD-L1 binding and provide cancer patients with an effective and cost-efficient treatment alternative to traditional immune checkpoint inhibitors.
  
  
  
  Methods:
  
  In vitro, we tested synthetic peptides by ELISA to determine if these peptides could effectively inhibit PD-1/PD-L1 binding. We confirmed that cells expressed these peptides after melanoma tumor transfection. We used Affymetrix arrays to quantify tumor PD-L1 pathway expression, then confirmed the expression of selected pathway markers in B16-F10 melanoma cells by flow cytometry and multiplex bead array. Finally, we tested this combination therapy in the B16-F10 mouse melanoma model.
  
  
  
  Results:
  
  We demonstrated that the mouse homolog to pembrolizumab was effective at blocking PD-1/PD-L1 in vitro. After intratumor plasmid delivery, these peptides bound PD-L1 on tumor cells. We established that plasmid DNA delivery to tumors in vivo or to tumor cells in vitro upregulated several immune modulators and PD-L1 mRNA and protein, potentiating checkpoint inhbitor therapy. Finally, we tested the efficacy of combined pIL-12 and peptide plasmid GET therapy in the B16-F10 mouse melanoma model. We determined that pIL-12 GET therapeutic efficacy could be enhanced by combination with the plasmid encoding the pembrolizumab mouse homolog.
  
  
  
  Conclusions:
  
  IL-12 plasmid GET combined with intratumor PD-1/PD-L1 blocking peptide expression may be a feasible and less expensive therapeutic option for metastatic melanoma.
  
  
  
  Keywords:
  
  
  Refs:
  
  
  Topic 1:
  6. Cancer treatment and tumor ablation
  
  Topic 2:
  12. Biomedical applications