Department of Clinical Pharmacology, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan.
J Pharmacol Sci. 2010;112(3):320-6. doi: 10.1254/jphs.09348fp. Epub 2010 Feb 20.
We have reported that the differentiation-inducing factors (DIFs) DIF-1 and DIF-3, morphogens secreted from Dictyostelium discoideum, inhibit proliferation of several cancer cells via suppression of the Wnt/beta-catenin signaling pathway. However, the target molecules of DIFs involved in the anti-proliferative effects are still unknown. In the present study, DIF-1-tethered resins were synthesized to explore the target molecules of DIFs, and mitochondrial malate dehydrogenase (mMDH) was identified as one of the target molecules. In the in vitro assay, DIF-1 and other analogs including 2-MIDIF-1, DIF-3, and 6-MIDIF-3 were found to be capable of binding to mMDH but not to cytoplasmic MDH. However, only DIF-1 and 2-MIDIF-1 inhibited the enzymatic activity of mMDH. The effects of DIF analogs on ATP content and cell proliferation were then analyzed using HeLa cells. DIF-1 and 2-MIDIF-1 were found to lower the ATP content and both chemicals inhibited HeLa cell proliferation, suggesting that inhibition of mMDH activity affected cell energy production, probably leading to the inhibition of proliferation. These results suggest that the inhibition of mMDH activity by DIF-1 and 2-MIDIF-1 could be one of the mechanisms to induce anti-proliferative effects, independent of the inhibition of the Wnt/beta-catenin signaling pathway.
我们曾报道过，来源于盘基网柄菌的分化诱导因子（DIFs）DIF-1 和 DIF-3 通过抑制 Wnt/β-连环蛋白信号通路来抑制多种癌细胞的增殖。然而，参与抗增殖作用的 DIFs 的靶分子仍不清楚。在本研究中，合成了 DIF-1 键合树脂，以探索 DIFs 的靶分子，鉴定出线粒体苹果酸脱氢酶（mMDH）为其靶分子之一。在体外试验中，发现 DIF-1 和其他类似物，包括 2-MIDIF-1、DIF-3 和 6-MIDIF-3，能够与 mMDH 结合，但不能与细胞质 MDH 结合。然而，只有 DIF-1 和 2-MIDIF-1 抑制 mMDH 的酶活性。然后用 HeLa 细胞分析 DIF 类似物对 ATP 含量和细胞增殖的影响。发现 DIF-1 和 2-MIDIF-1 降低了 ATP 含量，这两种化学物质均抑制了 HeLa 细胞的增殖，这表明 mMDH 活性的抑制影响了细胞能量的产生，可能导致增殖的抑制。这些结果表明，DIF-1 和 2-MIDIF-1 对 mMDH 活性的抑制可能是诱导抗增殖作用的机制之一，而与抑制 Wnt/β-连环蛋白信号通路无关。
