Gene-modified tumor vaccine secreting a designer cytokine Hyper-Interleukin-6 is an effective therapy in mice bearing orthotopic renal cell cancer

Abstract

Although renal cell cancer (RCC) is known to be immunogenic, clinical efficacy of various immunotherapeutic approaches remains unsatisfactory. Novel targeted therapies showing cytostatic rather than cytotoxic activity are unable to cure RCC patients. In our studies, we evaluated the therapeutic efficacy of whole-cell vaccine based on irradiated murine RENCA cells genetically modified to secrete designer cytokine--Hyper-IL6 (H6)--comprising IL-6 and soluble IL-6 receptor. An orthotopic RCC model based on a subcapsular implantation of RENCA cells into kidneys of Balb/C mice was employed. The efficacy of RENCA-H6 vaccine was compared with control vaccine (RENCA-wt) in relation to naive (non-immunized) animals. Three sets of vaccination experiments were carried out in a (i) protective, (ii) palliative and (iii) adjuvant (following nephrectomy) setting. The influence of vaccination on survival of RCC-bearing animals was analyzed. Specificity of vaccine-induced immune response was studied using model antigen-GFP. RCC-bearing animals immunized with RENCA-H6 vaccine showed prolonged survival compared with other groups. In palliative and adjuvant settings the survival RENCA-H6-immunized animals exceeded 75%. Administration of RENCA-H6 inhibited formation and recruitment of Treg cells (CD4+CD25+Foxp3+) and increased maturation of DCs. RENCA tumors in RENCA-H6- vaccinated animals contained large populations of NK cells and activated CD4+, CD8+ T cells. In addition, in mice vaccinated with RENCA-H6 cells large population of CD4+ and CD8+ memory cells (CD62Llow) were detected. In the orthotopic RCC model, RENCA-H6 vaccine showed high therapeutic potential, which resulted from modulation of numerous immunological mechanisms.