Chen Hwudaurw, Sells Earlphia, Pandey Ritu, Abril Edward R, Hsu Chiu-Hsieh, Krouse Robert S, Nagle Raymond B, Pampalakis Georgios, Sotiropoulou Georgia, Ignatenko Natalia A
University of Arizona Cancer Center, Tucson, AZ, USA.
Biochemistry and Molecular and Cellular Biology Graduate Program, Department of Molecular and Cellular Biology, College of Science, University of Arizona, Tucson, AZ, USA.
Oncotarget. 2019 Oct 22;10(58):6062-6078. doi: 10.18632/oncotarget.27153.
Kallikrein-related peptidase 6 (KLK6) overexpression is commonly observed in primary tumors of colorectal cancer (CRC) patients and has been associated with tumor aggressiveness, metastasis, and poor prognosis. We previously established a unique contribution of KLK6 in colon cancer metastasis via a specific network of microRNAs and mRNAs. Here we evaluated the cellular functions of KLK6 protease in Caco-2 colon adenocarcinoma cell line after introduction of the enzymatically active or inactive form of the enzyme. We found that proteolytically active KLK6 increased Caco-2 cells invasiveness and decreased the animal survival in the orthotopic colon cancer model. The active KLK6 induced phosphorylation of SMAD 2/3 proteins leading to the altered expression of the epithelial-mesenchymal transition (EMT) markers. KLK6 overexpression also induced the RNA-binding protein LIN28B and high-mobility group AT-hook 2 (HMGA2) transcription factor, two essential regulators of cell invasion and metastasis. In the CRC patients, KLK6 protein levels were elevated in the non-cancerous distant and adjacent tissues, compared to their paired tumor tissues ( < 0.0001 and = 0.0157, respectively). Patients with mutant K-RAS tumors had significantly higher level of KLK6 protein in the luminal surface of non-cancerous distant tissue, compared to the corresponding tissues of the patients with K-RAS wild type tumors ( ≤ 0.05). Furthermore, KLK6 and HMGA2 immunohistochemistry (IHC) scores in patients' tumors and paired adjacent tissues positively correlated (Spearman correlation < 0.01 and = 0.03, respectively). These findings demonstrate the critical function of the KLK6 enzyme in colon cancer progression and its contribution to the signaling network in colon cancer.
激肽释放酶相关肽酶6（KLK6）的过表达在结直肠癌（CRC）患者的原发性肿瘤中普遍存在，并且与肿瘤侵袭性、转移及不良预后相关。我们之前通过特定的微小RNA和信使核糖核酸网络确定了KLK6在结肠癌转移中的独特作用。在此，我们在引入该酶的酶活性或无活性形式后，评估了KLK6蛋白酶在Caco-2结肠腺癌细胞系中的细胞功能。我们发现，具有蛋白水解活性的KLK6增加了Caco-2细胞的侵袭性，并降低了原位结肠癌模型中的动物存活率。活性KLK6诱导SMAD 2/3蛋白磷酸化，导致上皮-间质转化（EMT）标志物表达改变。KLK6的过表达还诱导了RNA结合蛋白LIN28B和高迁移率族AT钩2（HMGA2）转录因子，这两者是细胞侵袭和转移的两个重要调节因子。在CRC患者中，与配对的肿瘤组织相比，非癌性远处和相邻组织中的KLK6蛋白水平升高（分别为<0.0001和=0.0157）。与K-RAS野生型肿瘤患者的相应组织相比，K-RAS突变型肿瘤患者的非癌性远处组织腔表面的KLK6蛋白水平显著更高（≤0.05）。此外，患者肿瘤及配对相邻组织中的KLK6和HMGA2免疫组化（IHC）评分呈正相关（Spearman相关性分别为<0.01和=0.03）。这些发现证明了KLK6酶在结肠癌进展中的关键作用及其对结肠癌信号网络的贡献。
