Departments of Biochemistry, Medicine, College of Medicine and Health Sciences, Sultan Qaboos University, PC 123, P. O. Box 35, Muscat, Sultanate of Oman.
Qatar University, P. O. Box: 2713, Doha, Qatar.
Hum Cell. 2022 Jul;35(4):1114-1125. doi: 10.1007/s13577-022-00715-3. Epub 2022 May 21.
Gastric cancer (GC) is ranked the third leading cause of cancer-related deaths worldwide. Mutations and epigenetic alterations in several essential genes, including p53, KRAS, PIK3CA, FAT4 and ARID1A, are often reported. Furthermore, loss of SOCS3 expression was reported in GC, suggesting its tumor suppressor role. To assess the mutational and methylation status of SOCS3, we performed gene panel exome sequencing on 47 human GC samples. The SOCS3 gene was rarely mutated, suggesting alternative regulation mechanisms, such as promoter hypermethylation and/or long non-coding RNAs (lncRNAs). We first explored SOCS3 promoter methylation status in 44 human GC samples by methylation-specific PCR (MS-PCR). Thirteen out of forty-four patients (29.5%) displayed a methylation pattern. Then, to see whether SOCS3 expression is silenced by CpG methylation, we examined publicly available databases (cbioportal and The Cancer Genome Atlas (TCGA)). The analysis revealed β values lower than 0.1, indicating hypo-methylation in healthy and GC samples. Moreover, moderate methylation (β < 0.4) and high methylation (β > 0.4) did not affect the free survival, suggesting that methylation is unlikely to be the mechanism ruling SOCS3 silencing in GC. Next, to assess the regulatory effects of lncRNAs on SOCS3, we silenced the AC125807.2-lncRNA and quantified the SOCS3 gene expression in AGS and NCI-N87 gastric cancer cell line. SOCS3 was found to be downregulated following AC125807.2-lncRNA silencing in AGS cells, suggesting the potential implication of lncRNA AC125807.2 in SOCS3 regulation. However, in NCI-N87 cells, there was no significant change in SOCS3 expression. In conclusion, neither mutations nor hypermethylation was associated with the SOCS3 downregulation in GC, and alternative mechanisms, including non-coding RNAs-mediated gene silencing, may be proposed.
胃癌（GC）是全球癌症相关死亡的第三大主要原因。包括 p53、KRAS、PIK3CA、FAT4 和 ARID1A 在内的几个关键基因的突变和表观遗传改变经常被报道。此外，GC 中 SOCS3 表达缺失，提示其具有肿瘤抑制作用。为了评估 SOCS3 的突变和甲基化状态，我们对 47 个人类 GC 样本进行了基因panel 外显子测序。SOCS3 基因很少发生突变，提示存在其他调节机制，如启动子高甲基化和/或长非编码 RNA（lncRNA）。我们首先通过甲基化特异性 PCR（MS-PCR）探索了 44 个人类 GC 样本中 SOCS3 启动子的甲基化状态。44 例患者中有 13 例（29.5%）显示出甲基化模式。然后，为了观察 SOCS3 表达是否因 CpG 甲基化而沉默，我们检查了公共可用数据库（cbioportal 和癌症基因组图谱（TCGA））。分析显示 β 值低于 0.1，表明健康和 GC 样本中的低甲基化。此外，中度甲基化（β < 0.4）和高度甲基化（β > 0.4）并不影响无复发生存，提示甲基化不太可能是 GC 中 SOCS3 沉默的机制。接下来，为了评估 lncRNA 对 SOCS3 的调控作用，我们沉默了 AC125807.2-lncRNA，并在 AGS 和 NCI-N87 胃癌细胞系中定量了 SOCS3 基因表达。在 AGS 细胞中，AC125807.2-lncRNA 沉默后 SOCS3 表达下调，提示 lncRNA AC125807.2 可能参与 SOCS3 调控。然而，在 NCI-N87 细胞中，SOCS3 表达没有明显变化。总之，GC 中 SOCS3 的下调既不是突变也不是高甲基化所致，可能存在包括非编码 RNA 介导的基因沉默在内的其他机制。
