Safety and efficacy of dendritic cell immunotherapy with ad-GMCAIX in an immunocompetent preclinical tumor model of renal cell carcinoma.

Abstract

e13045 Background: We have previously reported the successful ex vivo generation of hCAIX-specific cytotoxic T lymphocytes (CTLs) by adenoviral (Ad) transduction of the GMCAIX fusion protein in dendritic cells (DC). We then produced GMP-grade material (NIH-RAID program, NSC 740833). Now we test, for the first time, the in vivo anti-tumor activity of DC-Ad-GMCAIX against renal cell carcinoma (RCC) in a unique immunocompetent mouse tumor model. Methods: Tumor growth inhibition and specificity were studied in BALB/c mice s.c. transplanted with either syngeneic RENCA cells transduced with hCAIX (URCAIX) or with non-hCAIX-expressing RENCA cells (RENCA). In a tumor prevention model, cohorts of mice were first immunized s.c. twice with DC-Ad-GMCAIX, DC-Ad-null, or no DCs, followed by tumor challenge with s.c. transplantation of URCAIX or RENCA cells. In an intervention model, tumors were first established and then immunotherapy was employed. Tumor volume and body weight were regularly assessed. Partial necropsy, immunohistochemistry of harvested tumors, and complete blood count were performed at termination of each study. Results: In the prevention model, URCAIX tumor growth was specifically and significantly inhibited for 15 days (p<0.0001). At termination, median growth inhibition reached 79% (113 vs. 531 mm3) and half of the mice remained tumor-free. In the intervention model, DC-Ad-GMCAIX-treated mice showed specific and significant growth inhibition of URCAIX tumors for 8 days (p<0.0018) with a median growth inhibition reaching 60% (487 vs. 1,205 mm3). The threshold of 15% weight loss was delayed in the therapeutic groups of both models (p<0.0167). No treatment-related weight loss or organ toxicity was observed. hCAIX staining was absent or minimally present in URCAIX-tumors that evaded DC-Ad-GMCAIX therapy. Conclusions: DC-Ad-GMCAIX therapy in a novel immunocompetent mouse model demonstrated, for the first time, both tumor prevention and growth inhibition of established RCC tumors without evidence of systemic toxicity. These studies form the basis for first-in-human clinical trial in patients with advanced RCC.