Background:Long non-coding RNA (lncRNA) was identified as a novel diagnostic biomarker in gastric cancer (GC). However, the functions of lncRNAs in immuno-microenvironments have not been comprehensively explored. In this study, we explored a critical lncRNA, LOC339059, that can predict the clinical prognosis in GC related to the modulation of PD-L1 and determined its influence upon macrophage polarization via the IL-6/STAT3 pathway.Methods:To date, accumulating evidence has demonstrated that the dysregulation of LOC339059 plays an important role in the pathological processes of GC. It acts as a tumor suppressor, regulating GC cell proliferation, migration, invasion, tumorigenesis, and metastasis. A flow cytometry assay showed that the loss of LOC339059 enhanced PDL1 expression and M2 macrophage polarization. RNA sequencing, RNA pull-down, RNA immunoprecipitation, Chip-PCR, and a luciferase reporter assay revealed the pivotal role of signaling alternation between LOC339059 and c-Myc.Results:A lower level of LOC339059 RNA was found in primary GC tissues compared to adjacent tissues, and such a lower level is associated with a poorer survival period (2.5 years) after surgery in patient cohorts. Moreover, we determined important immunological molecular biomarkers. We found that LOC339059 expression was correlated with PD-L1, CTLA4, CD206, and CD204, but not with TIM3, FOXP3, CD3, C33, CD64, or CD80, in a total of 146 GC RNA samples. The gain of LOC339059 in SGC7901 and AGS inhibited biological characteristics of malignancy, such as proliferation, migration, invasion, tumorigenesis, and metastasis. Furthermore, our data gathered following the co-culture of THP-1 and U937 with genomic GC cells indicate that LOC339059 led to a reduction in the macrophage cell ratio, in terms of CD68+/CD206+, to 1/6, whereas the selective knockdown of LOC339059 promoted the abovementioned malignant cell phenotypes, suggesting that it has a tumor-suppressing role in GC. RNA-Seq analyses showed that the gain of LOC339059 repressed the expression of the interleukin family, especially IL-6/STAT3 signaling. The rescue of IL-6 in LOC339059-overexpressing cells reverted the inhibitory effects of the gain of LOC339059 on malignant cell phenotypes. Our experiments verified that the interaction between LOC339059 and c-Myc resulted in less c-Myc binding to the IL-6 promoter, leading to the inactivation of IL-6 transcription.Conclusions:Our results establish that LOC339059 acts as a tumor suppressor in GC by competitively inhibiting c-Myc, resulting in diminished IL-6/STAT3-signaling-mediated PDL1 expression and macrophage M2 polarization.
背景：长链非编码RNA（lncRNA）已被确定为胃癌（GC）的新型诊断生物标志物。然而，lncRNA在免疫微环境中的功能尚未得到全面探索。本研究探讨了一个关键lncRNA——LOC339059，它能够预测与PD-L1调控相关的GC临床预后，并通过IL-6/STAT3通路确定其对巨噬细胞极化的影响。 方法：迄今为止，越来越多的证据表明LOC339059的失调在GC的病理过程中发挥重要作用。它作为肿瘤抑制因子，调控GC细胞的增殖、迁移、侵袭、肿瘤发生和转移。流式细胞术分析显示，LOC339059的缺失增强了PD-L1表达和M2巨噬细胞极化。RNA测序、RNA pull-down、RNA免疫沉淀、Chip-PCR和荧光素酶报告基因实验揭示了LOC339059与c-Myc之间信号转导改变的关键作用。 结果：与癌旁组织相比，原发性GC组织中LOC339059 RNA水平较低，且这种较低水平与患者队列术后较差的生存期（2.5年）相关。此外，我们确定了重要的免疫分子生物标志物。在146例GC RNA样本中，我们发现LOC339059表达与PD-L1、CTLA4、CD206和CD204相关，但与TIM3、FOXP3、CD3、C33、CD64或CD80无关。在SGC7901和AGS细胞中过表达LOC339059可抑制增殖、迁移、侵袭、肿瘤发生和转移等恶性生物学特征。此外，THP-1和U937细胞与基因组GC细胞共培养的数据表明，LOC339059使巨噬细胞CD68+/CD206+比例降至1/6，而选择性敲低LOC339059则促进上述恶性细胞表型，提示其在GC中具有肿瘤抑制作用。RNA-Seq分析显示，LOC339059过表达抑制了白细胞介素家族的表达，特别是IL-6/STAT3信号通路。在LOC339059过表达细胞中恢复IL-6表达，可逆转LOC339059过表达对恶性细胞表型的抑制作用。实验证实LOC339059与c-Myc的相互作用减少了c-Myc与IL-6启动子的结合，导致IL-6转录失活。 结论：我们的研究结果证实，LOC339059通过竞争性抑制c-Myc在GC中发挥肿瘤抑制作用，从而减少IL-6/STAT3信号介导的PD-L1表达和巨噬细胞M2极化。
肿瘤(癌症)患者之家