Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA, USA.
Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA, USA.
FASEB J. 2020 Oct;34(10):13935-13948. doi: 10.1096/fj.202001136R. Epub 2020 Aug 26.
Epithelial ovarian carcinoma tissues express high levels of tumor necrosis factor-alpha (TNF-α) and other inflammatory cytokines. The underlying mechanism leading to the abnormal TNF-α expression in ovarian cancer remains poorly understood. In the current study, we demonstrated that lysophosphatidic acid (LPA), a lipid mediator present in ascites of ovarian cancer patients, induced expression of TNF-α mRNA and release of TNF-α protein in ovarian cancer cells. LPA also induced expression of interleukin-1β (IL-1β) mRNA but no significant increase in IL-1β protein was detected. LPA enhanced TNF-α mRNA through NF-κB-mediated transcriptional activation. Inactivation of ADAM17, a disintegrin and metalloproteinase, with a specific inhibitor TMI-1 or by shRNA knockdown prevented ovarian cancer cells from releasing TNF-α protein in response to LPA, indicating that LPA-mediated TNF-α production relies on both transcriptional upregulations of the TNF-α gene and the activity of ADAM17, the membrane-associated TNF-α-converting enzyme. Like many other biological responses to LPA, induction of TNF-α by LPA also depended on the transactivation of the epidermal growth factor receptor (EGFR). Interestingly, our results revealed that ADAM17 was also the shedding protease responsible for the transactivation of EGFR by LPA in ovarian cancer cells. To explore the biological outcomes of LPA-induced TNF-α, we examined the effects of a TNF-α neutralizing antibody and recombinant TNF-α soluble receptor on LPA-stimulated expression of pro-tumorigenic cytokines and chemokines overexpressed in ovarian cancer. Blockade of TNF-α signaling significantly reduced the production of IL-8, IL-6, and CXCL1, suggesting a hierarchy of mechanisms contributing to the robust expression of the inflammatory mediators in response to LPA in ovarian cancer cells. In contrast, TNF-α inhibition did not affect LPA-dependent cell proliferation. Taken together, our results establish that the bioactive lipid LPA drives the expression of TNF-α to regulate an inflammatory network in ovarian cancer.
上皮性卵巢癌组织表达高水平的肿瘤坏死因子-α（TNF-α）和其他炎症细胞因子。导致卵巢癌中 TNF-α 表达异常的潜在机制仍知之甚少。在本研究中，我们证明了存在于卵巢癌患者腹水中的脂质介质溶血磷脂酸（LPA）诱导卵巢癌细胞中 TNF-α mRNA 的表达和 TNF-α 蛋白的释放。LPA 还诱导白细胞介素-1β（IL-1β）mRNA 的表达，但未检测到 IL-1β 蛋白的显著增加。LPA 通过 NF-κB 介导的转录激活增强 TNF-α mRNA。用特异性抑制剂 TMI-1 或 shRNA 敲低使去整合素和金属蛋白酶 17（ADAM17）失活，可防止卵巢癌细胞在 LPA 作用下释放 TNF-α 蛋白，表明 LPA 介导的 TNF-α 产生既依赖于 TNF-α 基因的转录上调，也依赖于 ADAM17 的活性，ADAM17 是膜相关的 TNF-α 转化酶。与 LPA 对许多其他生物学反应一样，LPA 诱导 TNF-α 也依赖于表皮生长因子受体（EGFR）的转激活。有趣的是，我们的结果表明 ADAM17 也是 LPA 在上皮性卵巢癌细胞中通过 EGFR 转激活的脱落蛋白酶。为了研究 LPA 诱导的 TNF-α 的生物学后果，我们检查了 TNF-α 中和抗体和重组 TNF-α 可溶性受体对卵巢癌细胞中过表达的促肿瘤细胞因子和趋化因子的 LPA 刺激表达的影响。阻断 TNF-α 信号显著降低了 IL-8、IL-6 和 CXCL1 的产生，表明在卵巢癌细胞中，LPA 刺激炎症介质的强烈表达存在多种机制。相比之下，TNF-α 抑制不影响 LPA 依赖性细胞增殖。总之，我们的研究结果表明，生物活性脂质 LPA 驱动 TNF-α 的表达，以调节卵巢癌中的炎症网络。
