中性粒细胞的浸润对减毒鼠伤寒沙门氏菌介导犬乳腺肿瘤治疗的影响及其机理研究

Importantly, when avoiding tumor infiltration of neutrophils by neutrophil depletion at the time of infection, a higher total number of Salmonella typhimurium were found in the tumor inside and the formation of necrosis was strongly increased. However, systemic netrohil depletion seems unrealistic for humans. A possible alternative could be the local depletion of neutrophils, e.g., via engineered bacteria that secrete inhibitory molecular of neutrophil recruitment. The Del-1 is an anti-adhesive factor that interferes with the integrin LFA-1-dependent netrophil-endothelial adhesion and derived by endothelial cell. To inhibition of netrophils infiltration, we engineered S.t ΔppGpp/pBAD-Del-1. The mechanism by netrophil exerts the bacterial cancer therapy remains unclear. Understanding the mechanism imperative to develop therapeutic modality against the tumor growth, that is the purpose of this proposal. Using S.t ΔppGpp/pBAD-Del-1 and breast cancer model of mice and canine, we will determine effect of nertrophil infiltration on bacterial cancer therapy, which will help us uncover the nertrophil-mediated tumor microenvironment.

中性粒细胞在细菌靶向肿瘤治疗过程中，像屏障一样包围肿瘤坏死区域，对治疗起阻碍作用。Del-1来源于胚胎和成年内皮细胞，是整合素LFA-1的配体，也是中性粒细胞募集的有效抑制剂。本项目在已建立的肿瘤治疗用工程菌S.t ΔppGpp-Del-1和小鼠乳腺肿瘤模型的基础上：（1）通过小动物活体成像、肿瘤大小及肿瘤内的细菌数量，评价肿瘤治疗效果；（2）利用荧光定量PCR和ELISA，分析肿瘤的细胞因子表达；（3）采用免疫组化和流式细胞仪，评价Del-1在肿瘤内抑制中性粒细胞募集的效果；（4）采用免疫荧光染色，分析中性粒细胞募集的抑制是否影响IL-1β / TNF-α介导的免疫应答；（5）对已确诊的乳腺肿瘤犬作为肿瘤模型对其进行S.t ΔppGpp-Del-1治疗，并采用PEC/CT对治疗效果进行影像学的跟踪。

细菌介导的肿瘤治疗引发肿瘤内的中性粒细胞募集，中性粒细胞像屏障一样阻止细菌进入到肿瘤细胞活性区域。我们从基因治疗角度，让细菌携带中性粒细胞募集抑制剂del-1进入到肿瘤内；从化学药物角度，绿原酸、洛伐他丁、熊果酸等天然产物与细菌进行了联合治疗。无论是基因治疗或天然产物治疗，都能通过抑制中性粒细胞的募集，显著提高细菌的肿瘤治疗效果。

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