Therapeutic HER2/Neu DNA Vaccine Inhibits Mouse Tumor Naturally Overexpressing Endogenous Neu

Abstract

The therapeutic efficacy of HER2/c-erbB-2/neu DNA immunization on mouse tumor cells expressing exogenous human or rat p185neu but not on mouse tumor cells naturally expressing mouse p185neu has been demonstrated. We investigated the feasibility of using N-terminal rat neu DNA immunization on mouse tumor overexpressing endogenous p185neu and enhancing the therapeutic efficacy of this vaccine by fusion to various cytokine genes, including interleukin-2 (IL-2), interleukin-4 (IL-4), or granulocyte-macrophage colony-stimulating factor. In a therapeutic model, N'-neu-IL-2 DNA vaccine was significantly better than N'-neu DNA vaccine, and N'-neu DNA vaccine was significantly better than control DNA or N'-neu-IL-4 DNA vaccine. The therapeutic efficacy of DNA vaccines was correlated with tumor infiltration of CD8+ T cells. Depletion of CD8+ T cells completely abolished the therapeutic effects of N'-neu-IL-2 DNA vaccine and N'-neu DNA vaccine. Depletion of CD4+ T cells after tumor implantation had no influence on N'-neu-IL-2 DNA vaccine, but enhanced the therapeutic efficacy of N'-neu DNA vaccine. Our results demonstrate that rat N'-neu DNA vaccine has a therapeutic effect on established tumor through the CD8+ T-cell-dependent pathway. Depletion of CD4+ T cells or fusion to the IL-2 gene can thus further enhance the therapeutic effects of N'-neu DNA immunization on mouse tumor expressing endogenous p185neu.

RNA interference-mediated silencing of Foxo3 in antigen-presenting cells as a strategy for the enhancement of DNA vaccine potency

“…36 We have also shown that the combination of CD4 + T-cell depletion and intramuscular injection of the hN'-neu DNA vaccine causes dramatic increases in CD8 + T-cell responses and antitumor effects in a MBT-2 tumor model. 22 We propose that both CD8 + T cells and conventional CD4 + T-helper cells may contribute to the antitumor immunity against HER-2/neu-expressing tumors effected by the HER-2/neu DNA vaccine delivered by a gene gun. Moreover, this notion suggests that the removal of CD4 + Treg lymphocytes may further increase the effectiveness of hN'-neu DNA vaccination.…”

“…45 We further observed the surface expression of p185neu and major histocompatibility complex class I molecules on MBT-2 cells using flow cytometry. 22 Plasmid construction and preparation of the DNA vaccine A shRNA was constructed within a pHsU6 vector as described previously. 46 The targets were 5¢-GCAGCCGTGCCTTGTCAAA-3¢ÿ (for mouse Foxo3 shRNA) and 5¢-GCCGACCCGGTGTACTATA-3¢ÿ (for scramble shRNA).…”

“…22 In brief, female C3/HeN mice were challenged by subcutaneous injection in the flank with 1Â10 6 MBT-2 cells in 0.5 ml of cold phosphatebuffered saline. On day 10 when tumors were palpable, mice received 10 mg of scrambled shRNA, Foxo3 shRNA, hN'-neu-scramble shRNA or hN'-neu-Foxo3 shRNA DNA plasmid dissolved in 20 ml of autoclaved double-distilled water; each of these solutions was directly added to the loading hole near the nozzle and then delivered to the shaved abdominal region of the mice at a discharge pressure of 60 p.s.i.…”

“…22 . Briefly, mice received intraperitoneal treatment of rat anti-mouse mAb (clone 2.43, 0.5 mg per /mouse per week for CD8; GK 1.5, 0.5 mg per mouse per week for CD4; or PC61, 0.5 mg per mouse per week for CD25).…”

“…18 Effective HER-2/neu DNA vaccines may potentially be used for the therapeutic control of HER-2/neu-overexpressing tumor growth in several preclinical models. [19][20][21][22][23] We demonstrated that the hN'-neu-Foxo3 shRNA vaccine enhanced the therapeutic antitumor effect of the HER-2/neu DNA vaccine and also significantly increased the level of HER-2/neuspecific CD8 + T cells. Accordingly, we propose that the suppression of Foxo3 in APCs has implications for the design of future clinical trials aimed to evaluate novel DNA cancer vaccines.…”