MLK4, a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family, has been implicated in cancer progression. However, its role in lung adenocarcinoma has not been characterized. Here, we showed that MLK4 was overexpressed in a significant subset of lung adenocarcinoma, associated with a worse prognosis, and exerted an oncogenic function in vitro and in vivo. Bioinformatics analyses of clinical datasets identified phosphoenolpyruvate carboxykinase 1 (PCK1) as a novel target of MLK4. We validated that MLK4 regulated PCK1 expression at transcriptional level, by phosphorylating the transcription factor CREB, which in turn mediated PCK1 expression. We further demonstrated that PCK1 is an oncogenic factor in lung adenocarcinoma. Given the importance of PCK1 in the regulation of cellular metabolism, we next deciphered the metabolic effects of MLK4. Metabolic and mass spectrometry analyses showed that MLK4 knockdown led to significant reduction of glycolysis and decreased levels of glycolytic pathway metabolites including phosphoenolpyruvate and lactate. Finally, the promoter analysis of MLK4 unravelled a binding site of transcription factor KLF5, which in turn, positively regulated MLK4 expression in lung adenocarcinoma. In summary, we have revealed a KLF5-MLK4-PCK1 signalling pathway involved in lung tumorigenesis and established an unusual link between MAP3K signalling and cancer metabolism.

MLK4 是丝裂原激活蛋白激酶激酶 (MAP3K) 家族的成员，与癌症进展有关。然而，其在肺腺癌中的作用尚未得到表征。在这里，我们发现 MLK4 在肺腺癌的一个显着亚型中过度表达，与较差的预后相关，并且在体外和体内发挥致癌功能。临床数据集的生物信息学分析确定磷酸烯醇丙酮酸羧激酶 1 (PCK1) 是 MLK4 的新靶点。我们验证了 MLK4 通过磷酸化转录因子 CREB ​​在转录水平调节 PCK1 表达，而 CREB ​​反过来又介导 PCK1 表达。我们进一步证明PCK1是肺腺癌的致癌因子。鉴于 PCK1 在细胞代谢调节中的重要性，接下来我们破译了 MLK4 的代谢作用。代谢和质谱分析表明，MLK4 敲除导致糖酵解显着减少，并降低了糖酵解途径代谢物（包括磷酸烯醇丙酮酸和乳酸）的水平。最后，MLK4 的启动子分析揭示了转录因子 KLF5 的结合位点，进而正向调节肺腺癌中 MLK4 的表达。总之，我们揭示了参与肺肿瘤发生的 KLF5-MLK4-PCK1 信号通路，并在 MAP3K 信号传导与癌症代谢之间建立了不寻常的联系。MLK4 的启动子分析揭示了转录因子 KLF5 的结合位点，进而正向调节肺腺癌中的 MLK4 表达。总之，我们揭示了参与肺肿瘤发生的 KLF5-MLK4-PCK1 信号通路，并在 MAP3K 信号传导与癌症代谢之间建立了不寻常的联系。MLK4 的启动子分析揭示了转录因子 KLF5 的结合位点，进而正向调节肺腺癌中的 MLK4 表达。总之，我们揭示了参与肺肿瘤发生的 KLF5-MLK4-PCK1 信号通路，并在 MAP3K 信号传导与癌症代谢之间建立了不寻常的联系。