Liu Chaoqi, Lu Jiao, Tian Huiqun, Du Wei, Zhao Lin, Feng Jing, Yuan Ding, Li Zhiying
Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, China Three Gorges University, Yichang, Hubei 443001, P.R. China.
The Second Clinical Medical College, China Three Gorges University, Yichang, Hubei 443001, P.R. China.
Mol Med Rep. 2016 Dec 23. doi: 10.3892/mmr.2016.6073.
Cytotoxic T lymphocyte dysfunction is frequently associated with PD‑L1/PD‑1 pathway activation, and is a principal obstacle in cancer therapy. In the present study, the mechanisms underlying the human papillomavirus (HPV)‑induced evasion of cervical cancer cells to the host immune system via the programmed death ligand 1/programmed death 1 (PD‑L1/PD‑1) signaling pathway was investigated. A significant increase in the expression of the HPV16E7 viral protein and PD‑L1 in cervical tissues was observed when compared with normal cervical tissues. In addition, a positive correlation between HPV16E7 and PD‑L1 expression was observed by immunohistochemical staining and reverse transcription‑polymerase chain reaction. Overexpressing HPV16E7 oncoprotein in the epithelial carcinoma of PC3 cells increased the expression level of the PD‑L1 protein and inhibited peripheral blood mononuclear cell (PBMC) proliferation and cytotoxic T lymphocyte (CTL) activity. Upon knockdown of HPV16E7 in HPV16‑associated CaSki cervical cancer cells with a relevant siRNA, a reduction in PD‑L1 protein expression was observed, as well as a significant increase in PBMC proliferation and CTL activity. A recombinant plasmid, MSCVPIG‑soluble PD‑1, was constructed and transfected into the CaSki cell line, and was co‑cultured with PBMCs. PBMC proliferation and CTL activity were observed to increase significantly. In conclusion, the results presented in the current study suggest that overexpression of PD‑L1, induced by HPV16E7, may be responsible for lymphocyte dysfunction. In addition, soluble PD‑1 may restore the function of tumor‑infiltrating lymphocytes by inhibiting the PD‑L1/PD‑1 signaling pathway. These results may provide a novel insight for immunotherapeutic approaches in the treatment of cervical cancer.
细胞毒性T淋巴细胞功能障碍常与PD-L1/PD-1通路激活相关，是癌症治疗的主要障碍。在本研究中，探讨了人乳头瘤病毒（HPV）通过程序性死亡配体1/程序性死亡1（PD-L1/PD-1）信号通路诱导宫颈癌细胞逃避免疫系统的机制。与正常宫颈组织相比，观察到宫颈组织中HPV16E7病毒蛋白和PD-L1的表达显著增加。此外，通过免疫组织化学染色和逆转录-聚合酶链反应观察到HPV16E7与PD-L1表达之间呈正相关。在PC3细胞的上皮癌中过表达HPV16E7癌蛋白可增加PD-L1蛋白的表达水平，并抑制外周血单个核细胞（PBMC）增殖和细胞毒性T淋巴细胞（CTL）活性。用相关小干扰RNA（siRNA）敲低HPV16相关的CaSki宫颈癌细胞中的HPV16E7后，观察到PD-L1蛋白表达降低，以及PBMC增殖和CTL活性显著增加。构建了重组质粒MSCVPIG-可溶性PD-1并转染到CaSki细胞系中，并与PBMC共培养。观察到PBMC增殖和CTL活性显著增加。总之，本研究结果表明，HPV16E7诱导的PD-L1过表达可能是淋巴细胞功能障碍的原因。此外，可溶性PD-1可能通过抑制PD-L1/PD-1信号通路恢复肿瘤浸润淋巴细胞的功能。这些结果可能为宫颈癌的免疫治疗方法提供新的见解。
