Masayuki Kurooka

Inactivated Sendai Virus Particles Eradicate Tumors by Inducing Immune Responses through Blocking Regulatory T Cells

UV-inactivated, replication-defective Sendai virus particles [hemagglutinating virus of Japan envelope (HVJ-E)] injected into murine colon carcinoma (CT26) tumors growing in syngeneic BALB/c mice eradicated 60% to 80% of the tumors and obviously inhibited the growth of the remainder. Induced adaptive antitumor immune responses were dominant in the tumor eradication process because the effect was abrogated in severe combined immunodeficient mice. Murine and human dendritic cells underwent dose-dependent maturation by HVJ-E in vitro. Profiles of cytokines secreted by dendritic cells after HVJ-E stimulation showed that the amount of interleukin-6 (IL-6) released was comparable to that elicited by live HVJ. Real-time reverse transcription-PCR and immunohistochemistry revealed that HVJ-E induced a remarkable infiltration of dendritic cells and CD4+ and CD8+ T cells into tumors. In addition, CT26-specific CTLs were induced with the evidence of enhanced CD8+ T-cell activation in a CD4+CD25- T cell-dependent manner. On the other hand, conditioned medium from dendritic cells stimulated by HVJ-E rescued CD4+CD25- effector T-cell proliferation from Foxp3+CD4+CD25+ regulatory T cell (Treg)-mediated suppression and IL-6 was presumably dominant for this phenomenon. We also confirmed such rescue in mice treated with HVJ-E in vivo. Moreover, antitumor effect of HVJ-E was significantly reduced by an in vivo blockade of IL-6 signaling. This is the first report to show that HVJ-E alone can eradicate tumors and the mechanism through which it induces antitumor immune responses. Because it can enhance antitumor immunity and simultaneously remove Treg-mediated suppression, HVJ-E shows promise as a novel therapeutic for cancer immunotherapy.

Intratumoral injection of inactivated Sendai virus particles elicits strong antitumor activity by enhancing local CXCL10 expression and systemic NK cell activation

We have already demonstrated that inactivated, replication-defective Sendai virus particles (HVJ-E) have a powerful antitumor effect by both the generation of tumor-specific cytotoxic T cells and inhibition of regulatory T cell activity. Here, we report that HVJ-E also has an antitumor effect through non-T cell immunity. Microarray analysis revealed that direct injection of HVJ-E induced the expression of CXCL10 in established Renca tumors. CXCL10 was secreted by dendritic cells in the tumors after HVJ-E injection. Quantitative real-time RT-PCR and immunohistochemistry revealed that CXCR3+ cells (predominantly NK cells) infiltrated the HVJ-E-injected tumors. Moreover, HVJ-E injection caused systemic activation of NK cells and enhanced their cytotoxity against tumor cells. In an in vivo experiment, approximately 50% of tumors were eradicated by HVJ-E injection, and this activity of HVJ-E against Renca tumors was largely abolished by NK cell depletion using anti-asialo GM1 antibody. Since HVJ-E injection induced systemic antitumor immunity by enhancing or correcting the chemokine-chemokine receptor axis, it might be a potential new therapy for cancer.

Sendai virus F glycoprotein induces IL-6 production in dendritic cells in a fusion-independent manner

We previously reported that inactivated Sendai virus particle (hemagglutinating virus of Japan envelope; HVJ‐E) has anti‐tumor effects by eliciting IL‐6 production in dendritic cells (DCs). In the present study, we investigated which components of HVJ‐E elicit IL‐6 production. HVJ‐E containing F0 protein inactive for virus envelope–cell membrane fusion enhanced IL‐6 production. Reconstituted liposomes containing F protein stimulated IL‐6 production. The antibody against F protein inhibited IL‐6 secretion by HVJ‐E. When carbohydrate chains of the F glycoprotein were removed, HVJ‐E lost the ability to stimulate IL‐6 secretion. These results suggest that F glycoprotein is required for IL‐6 production in DCs.

Morphology and function of human benign tumors and normal thyroid tissues maintained in severe combined immunodeficient mice

In the improved SCID (severe combined immunodeficient) mice, various human benign tumors of the head and neck region were well maintained morphologically and functionally for 3 years until the experiments were terminated, e.g. transplanted parathyroid adenoma secreted parathyroid hormone (PTH) in the SCID mice for more than 1 year. Normal human thyroid tissue was also well maintained in the SCID mice for 3 years. Rapid and high uptake of radioiodine into the transplanted human thyroid tissue was observed. Furthermore, transplanted human thyroid tissue secreted thyroid hormone (T3) and T3 secretion was stimulated by the injection of human thyroid stimulating hormone (TSH). These findings suggest that the improved SCID mice will provide an invaluable experimental system for investigating the function of normal human tissues and the influence of endogenous and exogenous factors on human tissues.

High incidence of esophageal cancer in esophageal achalasia by the oral administration of N-amyl-N-methylnitrosamine and its prevention by nicardipine hydrochloride in mice.

Esophageal achalasia (EA) is a rare disease in man and animals and there are many discussions on its higher risk of esophageal cancer. N-Amyl-N-methylnitrosamine (AMN) which specifically induces esophageal tumors in mice and rats was given to three mutant mouse strains, i.e. 101/N, STX/Le and BXH-8, which develop a high incidence of EA. The incidence of EA in 101/N, STX/Le, BXH-8 and normal C57BL/6J mice was 38.5% (110/286), 30.1% (43/143), 91.8% (190/207) and 0% (0/167), respectively. The average numbers of AMN-induced esophageal tumors in EA(+) were significantly higher than those of EA(-) in all of the 101/N, STX/Le and BXH-8 mice. Furthermore, significantly larger size tumors and invasive squamous cell carcinomas were found in EA(+) mice than in EA(-) mice. These results indicate the higher sensitivity of EA for both tumor induction and promotion, possibly due to the longer retention of AMN. In fact, relaxation of the lower esophagus by a smooth muscle relaxing calcium-channel blocker, nicardipine hydrochloride, significantly prevented the induction of esophageal tumors.