Biomedical Sciences Division, School of Medicine, University of California, Riverside, CA 92521, USA.
Mol Cancer. 2013 Jul 17;12:78. doi: 10.1186/1476-4598-12-78.
Inflammation is a well-known etiological factor for colorectal cancer, but mechanisms underlying the linkage between inflammation and cancer are incompletely understood. We hypothesized that two pro-inflammatory cytokines, TNFα and IL-17, might play a role in promoting colorectal carcinogenesis. Aerobic glycolysis is a metabolic adaptation that promotes the survival/proliferation of cancer cells. Paracrine signaling between tumor cells and cancer-associated fibroblasts also plays a role in carcinogenesis.
The effect of TNFα and IL-17 on aerobic glycolysis and growth factor production in cultured human colorectal cancer cells was investigated. Glucose utilization and lactate production were quantified by measuring the disappearance of glucose and appearance of lactate in the culture medium. Glucose transporter and glycolytic enzyme expression levels were measured by immunoblotting.
TNFα and IL-17 cooperatively stimulated glycolysis in HT-29, T84, Caco-2 and HCT116 colorectal cancer cells. Treatment of HT-29 cells with TNFα plus IL-17 also increased the expression of HIF-1α and c-myc, two factors know to induce the transcription of genes encoding components of the glycolytic pathway. To further investigate mechanisms for cytokine-stimulated glycolysis, the effects of TNFα and IL-17 on expression of six members and one regulator of the glycolytic pathway were investigated. TNFα and IL-17 cooperatively increased the expression of the glucose transporter SLC2A1 and hexokinase-2 but did not regulate expression of glucose transporter SLC2A3, enolase-1, pyruvate kinase M2, lactate dehydrogenase A, or 6-phoshofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3). Experiments with inhibitors indicated that HIF-1α played a role in induction of SLC2A1 and that the transcription factor NF-κB played a role in induction of hexokinase-2 by TNFα and IL-17. TNFα and IL-17 also synergistically stimulated production by HT-29 cells of a growth factor that simulated proliferation/survival of NIL8 fibroblastic cells. The activity of this factor was not specifically inhibited by the EGFR inhibitor AG1478, indicating that it is not an EGFR ligand.
Chronic inflammation is known to promote colorectal tumorigenesis. The pro-inflammatory cytokines TNFα and IL-17 may contribute to this effect by stimulating glycolysis and growth factor production in colorectal cancer cells.
炎症是结直肠癌的已知病因，但炎症与癌症之间的联系机制尚不完全清楚。我们假设两种促炎细胞因子 TNFα 和 IL-17 可能在促进结直肠癌细胞发生癌变方面发挥作用。有氧糖酵解是促进癌细胞存活/增殖的代谢适应。肿瘤细胞与癌相关成纤维细胞之间的旁分泌信号也在癌变中发挥作用。
研究了 TNFα 和 IL-17 对培养的人结直肠癌细胞有氧糖酵解和生长因子产生的影响。通过测量培养基中葡萄糖的消失和乳酸的出现来定量葡萄糖利用和乳酸生成。通过免疫印迹法测量葡萄糖转运蛋白和糖酵解酶的表达水平。
TNFα 和 IL-17 协同刺激 HT-29、T84、Caco-2 和 HCT116 结直肠癌细胞的糖酵解。用 TNFα 加 IL-17 处理 HT-29 细胞也增加了 HIF-1α 和 c-myc 的表达，这两种因子已知可诱导编码糖酵解途径成分的基因的转录。为了进一步研究细胞因子刺激糖酵解的机制，研究了 TNFα 和 IL-17 对糖酵解途径的六个成员和一个调节剂的表达的影响。TNFα 和 IL-17 协同增加葡萄糖转运蛋白 SLC2A1 和己糖激酶-2 的表达，但不调节葡萄糖转运蛋白 SLC2A3、烯醇酶-1、丙酮酸激酶 M2、乳酸脱氢酶 A 或 6-磷酸果糖-2-激酶/果糖-2,6-二磷酸 3（PFKFB3）的表达。用抑制剂进行的实验表明，HIF-1α 在诱导 SLC2A1 中起作用，转录因子 NF-κB 在 TNFα 和 IL-17 诱导己糖激酶-2 中起作用。TNFα 和 IL-17 还协同刺激 HT-29 细胞产生一种生长因子，该因子模拟 NIL8 成纤维细胞的增殖/存活。该因子的活性不能被 EGFR 抑制剂 AG1478 特异性抑制，表明它不是 EGFR 配体。
已知慢性炎症会促进结直肠肿瘤发生。促炎细胞因子 TNFα 和 IL-17 可能通过刺激结直肠癌细胞的糖酵解和生长因子产生来促进这种作用。
