Peng Hsuan-Hsiang, Yang Hao-Chin, Rupa Darius, Yen Chun-Han, Chiu Ya-Wen, Yang Wei-Jia, Luo Fuh-Jinn, Yuan Ta-Chun
Department of Life Science, National Dong Hwa University, No. 1, Sec. 2, Da Hsueh Rd., Shoufeng, Hualien, 974301, Taiwan, Republic of China.
Department of Pathology, Mennonite Christian Hospital, Hualien, 970, Taiwan, Republic of China.
J Cell Commun Signal. 2022 Dec;16(4):567-578. doi: 10.1007/s12079-022-00670-6. Epub 2022 Mar 5.
Head and neck squamous cell carcinoma (HNSCC) is a malignancy with a worldwide distribution. Although intensive studies have been made, the underlying oncogenic mechanism of HNSCC requires further investigation. In this study, we examined the oncogenic role of activated Cdc42-associated kinase 1 (ACK1), an oncogenic tyrosine kinase, in regulating the proliferation of HNSCC cells and its underlying molecular mechanism. Results from immunohistochemical studies revealed that ACK1 was highly expressed in HNSCC tumors, with 77% (77/100) of tumors showing a high ACK1 immunoreactivity compared to 40% (8/20) of normal mucosa. Knockdown of ACK1 expression in HNSCC cells resulted in elevated p27 expression, reduced cell proliferation, and G1-phase cell cycle arrest. Rescue of ACK1 expression in the ACK1-knockdown cells suppressed p27 expression and restored cell proliferation. Compared to ACK1-knockdown cells, ACK1-rescued cells exhibited a restored p27 expression after MG132 treatment and showed an elevated level of ubiquitinated p27. Our data further showed that knockdown of ubiquitin ligase Skp2 resulted in elevated p27 expression. Importantly, the expression of p27(WT), p27(Y74F), or p27(Y89F) in ACK1-overexpressed 293T cells or ACK1-rescued SAS cells showed higher levels of tyrosyl-phosphorylated p27 and interaction with ACK1 or Skp2. However, the expression of p27(Y88F) mutant exhibited a relatively low phosphorylation level and barely bound with ACK1 or Skp2, showing a basal interaction as the control cells. These results suggested that ACK1 is highly expressed in HNSCC tumors and functions to promote cell proliferation by the phosphorylation and degradation of p27 in the Skp2-mediated mechanism.
头颈部鳞状细胞癌（HNSCC）是一种在全球范围内分布的恶性肿瘤。尽管已经进行了深入研究，但HNSCC的潜在致癌机制仍需进一步研究。在本研究中，我们研究了致癌酪氨酸激酶——活化的Cdc42相关激酶1（ACK1）在调节HNSCC细胞增殖中的致癌作用及其潜在分子机制。免疫组织化学研究结果显示，ACK1在HNSCC肿瘤中高表达，77%（77/100）的肿瘤显示出高ACK1免疫反应性，而正常黏膜中这一比例为40%（8/20）。敲低HNSCC细胞中ACK1的表达导致p27表达升高、细胞增殖减少以及G1期细胞周期停滞。在ACK1敲低的细胞中恢复ACK1表达可抑制p27表达并恢复细胞增殖。与ACK1敲低的细胞相比，ACK1挽救的细胞在MG132处理后p27表达恢复，并显示泛素化p27水平升高。我们的数据进一步表明，敲低泛素连接酶Skp2会导致p27表达升高。重要的是，在ACK1过表达的293T细胞或ACK1挽救的SAS细胞中，p27（WT）、p27（Y74F）或p27（Y89F）的表达显示出较高水平的酪氨酸磷酸化p27以及与ACK1或Skp2的相互作用。然而，p27（Y88F）突变体的表达显示出相对较低的磷酸化水平，并且几乎不与ACK1或Skp2结合，表现出与对照细胞一样的基础相互作用。这些结果表明，ACK1在HNSCC肿瘤中高表达，并通过Skp2介导的机制对p27进行磷酸化和降解来促进细胞增殖。
