Department of Oral and Maxillofacial-Head & Neck Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Zhizaoju Road No. 639, Huangpu District, Shanghai, 200011, China.
Clin Transl Oncol. 2022 Jul;24(7):1311-1321. doi: 10.1007/s12094-021-02769-5. Epub 2022 Feb 5.
Oral squamous cell carcinoma (OSCC) is the most frequent type of oral cancer and is associated with high mortality. Membrane-associated ring-CH type finger 1 (MARCH1) is an E3 ubiquitin ligase with roles in immune regulation and cancer development. Whether MARCH1 has a specific role in OSCC, and if so through what mechanism, has not been explored.
Immunohistochemistry was performed to examine MARCH1 expression in OSCC clinical samples and adjacent paracancerous tissues. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and Western blot were conducted to determine mRNA expression and protein levels, respectively. Knockdown and overexpression experiments were carried out to evaluate the effects of MARCH1 on proliferation and apoptosis. To test protein-protein interaction, co-immunoprecipitation assay was performed. Finally, tumor cell grafting was utilized to test the function of MARCH in vivo.
High MARCH1 expression in OSCC clinical samples correlated with poor patient prognosis. Functionally, MARCH1 knockdown in OSCC cells suppressed proliferation and promoted apoptosis, while MARCH1 overexpression displayed the opposite effects. We identified PH Domain And Leucine Rich Repeat Protein Phosphatase (PHLPP) 2 as an important target of MARCH1. Mechanistically, MARCH1 interacted with PHLPP2 and promoted PHLPP2 ubiquitination. Lastly, MARCH1 knockdown suppressed OSCC tumorigenicity in vivo and increased PHLPP2 protein level.
Our study uncovered a function of MARCH1 in OSCC and identified PHLPP2 as an important target of MARCH1 to modulate OSCC cell proliferation and apoptosis.
口腔鳞状细胞癌（OSCC）是最常见的口腔癌类型，与高死亡率相关。膜相关环-CH 型手指 1（MARCH1）是一种 E3 泛素连接酶，在免疫调节和癌症发展中发挥作用。MARCH1 是否在 OSCC 中具有特定作用，如果有，其机制是什么，尚未得到探索。
通过免疫组织化学检测 OSCC 临床样本和相邻癌旁组织中 MARCH1 的表达。采用定量逆转录聚合酶链反应（qRT-PCR）和 Western blot 分别检测 mRNA 表达和蛋白水平。通过敲低和过表达实验评估 MARCH1 对增殖和凋亡的影响。为了测试蛋白-蛋白相互作用，进行了共免疫沉淀实验。最后，利用肿瘤细胞移植实验检测 MARCH1 在体内的功能。
OSCC 临床样本中 MARCH1 高表达与患者预后不良相关。功能上，OSCC 细胞中 MARCH1 的敲低抑制增殖并促进凋亡，而过表达则显示相反的效果。我们鉴定出 PH 结构域和亮氨酸丰富重复蛋白磷酸酶（PHLPP）2 是 MARCH1 的重要靶标。在机制上，MARCH1 与 PHLPP2 相互作用并促进 PHLPP2 的泛素化。最后，MARCH1 的敲低抑制了 OSCC 在体内的致瘤性，并增加了 PHLPP2 蛋白水平。
本研究揭示了 MARCH1 在 OSCC 中的功能，并鉴定出 PHLPP2 是 MARCH1 调节 OSCC 细胞增殖和凋亡的重要靶标。
