Faculty of Medicine, Immunology Program, Biomedical Sciences Institute (ICBM), University of Chile, Santiago de Chile, Chile.
Centro de InmunoBiotecnología, Immunology Program, Biomedical Sciences Institute (ICBM), Faculty of Medicine, University of Chile, Santiago de Chile, Chile.
Helicobacter. 2021 Aug;26(4):e12812. doi: 10.1111/hel.12812. Epub 2021 Apr 29.
Natural killer (NK) cells are paramount for immunity against infectious agents and tumors. Their cytokine and cytolytic responses can be mediated by natural killer group 2, member D (NKG2D), an activating receptor whose ligands (NKG2DL) expression is induced in conditions of cell stress and malignant transformation. Since sustained expression of NKG2DL MICA is related to lower survival rates in gastric adenocarcinoma patients, and Helicobacter pylori infection contributes to tumorigenesis; we asked whether H. pylori stimulus could promote NKG2DL expression on human gastric adenocarcinoma cells.
Heat-killed H. pylori (HKHP) was used to stimulate MKN45 cells before analysis of NKG2DL and Toll-like receptor 4 (TLR4) protein levels by flow cytometry and transcripts by real-time PCR. LPS from Rhodobacter sphaeroides and inhibitory peptide Pepinh MYD were used to inhibit TLR4/MyD88 signaling pathway to assess its participation on NKG2DL expression. NK cell-mediated cytotoxicity was measured by lactate dehydrogenase (LDH) and CD107a mobilization assays.
Stimulation of MKN45 cells with HKHP increased MICA, ULBP4 (another NKG2DL), and TLR4 at the protein and transcriptional levels. MICA, but not ULBP4 expression, was upregulated in a TLR4/MyD88-dependent manner. Furthermore, the presence of NKG2DL on the surface of HKHP-stimulated MKN45 cells enabled NK cell cytotoxic activation.
Our data indicate that induction of NKG2DL expression on gastric adenocarcinoma cells by H. pylori promotes an immune response that may ultimately contribute to either gastric tissue damage, as a consequence of persistent activation of immunity, or tumor immune evasion due to chronic NKG2DL expression.
自然杀伤 (NK) 细胞对于抵御感染因子和肿瘤至关重要。其细胞因子和细胞溶解反应可由自然杀伤组 2，成员 D (NKG2D) 介导，该激活受体的配体（NKG2DL）在细胞应激和恶性转化条件下表达。由于胃腺癌患者中 MICA 的持续表达与较低的生存率相关，并且幽门螺杆菌感染有助于肿瘤发生；我们想知道幽门螺杆菌刺激是否可以促进人胃腺癌细胞上 NKG2DL 的表达。
使用热灭活的幽门螺杆菌 (HKHP) 刺激 MKN45 细胞，然后通过流式细胞术分析 NKG2DL 和 Toll 样受体 4 (TLR4) 蛋白水平，并通过实时 PCR 分析转录物。使用来自球形红杆菌的 LPS 和抑制肽 Pepinh MYD 抑制 TLR4/MyD88 信号通路，以评估其对 NKG2DL 表达的参与。通过乳酸脱氢酶 (LDH) 和 CD107a 动员测定测量 NK 细胞介导的细胞毒性。
HKHP 刺激 MKN45 细胞可增加 MICA、ULBP4（另一种 NKG2DL）和 TLR4 的蛋白和转录水平。MICA 的表达上调依赖于 TLR4/MyD88，而 ULBP4 的表达上调则不依赖于 TLR4/MyD88。此外，HKHP 刺激的 MKN45 细胞表面存在 NKG2DL 可使 NK 细胞的细胞毒性激活。
我们的数据表明，幽门螺杆菌诱导胃腺癌细胞 NKG2DL 的表达促进了免疫反应，这可能最终导致胃组织损伤，作为免疫持续激活的结果，或由于慢性 NKG2DL 表达导致肿瘤免疫逃避。
