Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA.
Oncogene. 2010 Aug 5;29(31):4399-411. doi: 10.1038/onc.2010.198. Epub 2010 May 31.
The malignant phenotype in breast cancer is driven by aberrant signal transduction pathways. Mixed-lineage kinase-3 (MLK3) is a mammalian mitogen-activated protein kinase kinase kinase (MAP3K) that activates multiple MAPK pathways. Depending on the cellular context, MLK3 has been implicated in apoptosis, proliferation, migration and differentiation. Here we investigated the effect of MLK3 and its signaling to MAPKs in the acquisition of malignancy in breast cancer. We show that MLK3 is highly expressed in breast cancer cells. We provide evidence that MLK3's catalytic activity and signaling to c-jun N-terminal kinase (JNK) is required for migration of highly invasive breast cancer cells and for MLK3-induced migration of mammary epithelial cells. Expression of active MLK3 is sufficient to induce the invasion of mammary epithelial cells, which requires AP-1 activity and is accompanied by the expression of several proteins corresponding to AP-1-regulated invasion genes. To assess MLK3's contribution to the breast cancer malignant phenotype in a more physiological setting, we implemented a strategy to inducibly express active MLK3 in the preformed acini of MCF10A cells grown in 3D Matrigel. Induction of MLK3 expression dramatically increases acinar size and modestly perturbs apicobasal polarity. Remarkably, MLK3 expression induces luminal repopulation and suppresses the expression of the pro-apoptotic protein BimEL, as has been observed in Her2/Neu-expressing acini. Taken together, our data show that MLK3-JNK-AP-1 signaling is critical for breast cancer cell migration and invasion. Our current study uncovers both a proliferative and novel antiapoptotic role for MLK3 in the acquisition of a malignant phenotype in mammary epithelial cells. Thus, MLK3 may be an important therapeutic target for the treatment of invasive breast cancer.
乳腺癌的恶性表型是由异常信号转导途径驱动的。混合谱系激酶 3（MLK3）是一种哺乳动物丝裂原活化蛋白激酶激酶激酶（MAP3K），可激活多种 MAPK 途径。根据细胞环境的不同，MLK3 已被牵连到细胞凋亡、增殖、迁移和分化中。在这里，我们研究了 MLK3 及其对 MAPK 的信号转导在乳腺癌获得恶性表型中的作用。我们表明，MLK3 在乳腺癌细胞中高度表达。我们提供的证据表明，MLK3 的催化活性及其对 c-Jun N 端激酶（JNK）的信号转导对于高度侵袭性乳腺癌细胞的迁移以及 MLK3 诱导的乳腺上皮细胞迁移是必需的。表达活性 MLK3 足以诱导乳腺上皮细胞的侵袭，这需要 AP-1 活性，并伴随着几种与 AP-1 调节的侵袭基因相对应的蛋白的表达。为了在更生理的环境中评估 MLK3 对乳腺癌恶性表型的贡献，我们实施了一种策略，即在 MCF10A 细胞预先形成的空泡中，在 3D Matrigel 中诱导表达活性 MLK3。MLK3 表达的诱导显著增加了空泡的大小，并适度扰乱了顶端基底极性。值得注意的是，MLK3 表达诱导腔的再填充，并抑制促凋亡蛋白 BimEL 的表达，这在 Her2/Neu 表达的空泡中已经观察到。总之，我们的数据表明，MLK3-JNK-AP-1 信号对于乳腺癌细胞的迁移和侵袭至关重要。我们目前的研究揭示了 MLK3 在乳腺上皮细胞获得恶性表型中的增殖和新的抗凋亡作用。因此，MLK3 可能是治疗侵袭性乳腺癌的重要治疗靶点。
