Background: Human epidermal growth factor receptor 2 (HER2) is overexpressed in a subset of cancers including 25% of breast cancers. Since combination therapy consisting of multiple therapeutic approaches is considered a promising regimen, we examined combination treatment modalities in a xenograft model in Balb/c mice injected with 4T1-HER2 cells. We used HER2/neu-loaded bone marrow-derived dendritic cells (BM-DC’s) along with anti-PD-L1 monoclonal antibody in a new combination immunotherapy model.

Methods: The combination was composed of an active immunotherapy (i.e. BM-DC-based vaccine) designed to boost the immune response against target antigen and was augmented by using anti-PD-L1 mAb to prevent immune evasion by the xenografted tumors. The vaccine combination was further supported using a QS-21 saponin adjuvant and the immune response was evaluated.

Results: Mice treated with HER2/neu-loaded BM-DCs, combined with QS-21 and anti-PD-L1 mAb had significantly decreased tumor sizes and their splenocytes had enhanced cytotoxic activity, based on the lactate dehydrogenase (LDH) assay, compared to vaccine and adjuvant groups alone. The same vaccination group demonstrated a remarkable increase in IFN-γ secreting CD8+ T-cells analyzed by flow cytometry. ELISA data also revealed a significant increase in the serum anti-HER2 IgG1 response; in addition, there was significant splenocyte proliferation upon stimulation with antigen compared to vaccine and adjuvant groups. Consistently, a significant infiltration of CD4+, CD8+ immune cells in and around the tumors was observed.

Conclusions: Our data suggest that the BM-DC + HER2/neu + QS-21 + anti-PD-L1 vaccine combination paradigm synergistically generates anti-tumor activity and immune responses against HER2 overexpressing breast cancer in mice.

背景：人类表皮生长因子受体2（HER2）在包括25％的乳腺癌在内的部分癌症中过表达。由于由多种​​治疗方法组成的联合治疗被认为是一种有前途的治疗方案，因此我们在注射了4T1-HER2细胞的Balb / c小鼠中检查了异种移植模型中的联合治疗方式。我们在新的联合免疫治疗模型中使用了HER2 / neu加载的骨髓源性树突状细胞（BM-DC's）和抗PD-L1单克隆抗体。

方法：该组合由旨在增强针对靶抗原的免疫反应的主动免疫疗法（即基于BM-DC的疫苗）组成，并通过使用抗PD-L1 mAb来增强，以防止异种移植肿瘤逃避免疫。使用QS-21皂苷佐剂进一步支持疫苗组合，并评估了免疫反应。

结果：根据乳酸脱氢酶（LDH）分析，与HER2 / neu加载的BM-DCs联合QS-21和抗PD-L1 mAb治疗的小鼠相比，肿瘤大小显着降低，脾细胞的细胞毒活性增强。仅用于疫苗和佐剂组。通过流式细胞仪分析，同一疫苗接种组证明分泌IFN-γ的CD8 + T细胞显着增加。ELISA数据还显示血清抗-HER2 IgG1反应显着增加。此外，与疫苗和佐剂组相比，抗原刺激后脾细胞明显增生。一致地，观察到肿瘤内和周围的CD4 +，CD8 +免疫细胞的显着浸润。

结论：我们的数据表明BM-DC + HER2 / neu + QS-21 +抗PD-L1疫苗组合范例协同产生抗肿瘤活性和针对小鼠HER2过表达乳腺癌的免疫反应。