COL8A1调控AKT促进乳腺癌上皮间质转化 (EMT) 及转移的分子机制

Metastasis, which is associated with epithelial mesenchymal transition (EMT) and tumor microenvironment, is the leading cause of death in breast cancer. COL8A1, as a novel type of extracellular matrix collagen proteins within the tumor microenvironment, is involved in cell growth and metastasis, but its functions in the metastasis of breast cancer is still not clear. Our previous studies found that COL8A1 expression correlated with the metastatic potential of breast cancer. The blockade of COL8A1 by RNAi in breast cancer cells could inhibit EMT, cell migration and invasion through up-regulating E-cadherin, down-regulating N-cadherin and Snail, and decreasing p-AKT activity. In the current project, we will focus on both in vitro and in vivo molecular mechanism of COL8A1 in regulating EMT and metastasis through AKT. This study includes three aspects: ① To explore the correlation within the COL8A1, p-AKT and EMT expressions in metastasis and prognosis in breast cancer specimens. ② To explore the molecular mechanism of COL8A1 in regulation of breast cancer EMT and metastasis via AKT by constructing stable cells model with higher or lower COL8A1 expression. ③ To confirm whether COL8A1 can promote tumor growth and metastasis through AKT/EMT in mouse model. Our study will shed light on the role of COL8A1 in breast cancer metastasis, and develop new therapeutic strategy for metastasis cancers by targeting COL8A1.

转移是乳腺癌患者死亡主要原因，肿瘤侵袭和转移与上皮间质转化 (EMT) 及肿瘤微环境密切相关。COL8A1是细胞外基质胶原蛋白家族成员，参与细胞增殖和转移，但在乳腺癌转移中的作用机制尚不明确。前期研究发现，COL8A1基因表达与乳腺癌转移相关；沉默乳腺癌细胞COL8A1基因，可显著下调p-AKT活性，抑制EMT发生，并降低迁移和侵袭能力。本课题将对COL8A1通过AKT调节乳腺癌EMT发生和转移的分子机制进行研究。包括三个方面：临床样本研究COL8A1表达、p-AKT活化和EMT发生及乳腺癌转移预后的关系；构建COL8A1高、低表达细胞模型，研究该基因在乳腺癌EMT发生和转移中的作用以及AKT参与的分子机制；小鼠模型验证COL8A1体内促癌和促转移作用，及对p-AKT活性和EMT发生的影响。本研究的成功将有助于阐释COL8A1在乳腺癌转移中的作用和发展靶向COL8A1的转移性肿瘤治疗策略。

乳腺癌是目前世界女性最常见、最严重的恶性肿瘤之一，发病率呈持续上升趋势。复发和转移是乳腺癌死亡的主要原因，上皮细胞－间充质转化（EMT）是上皮性肿瘤细胞侵袭和转移过程中重要步骤。COL8A1是细胞外基质胶原蛋白家族成员，参与细胞增殖和转移。我们发现COL8A1在乳腺癌组织和乳腺癌细胞中高表达，COL8A1表达水平高的患者生存率低于COL8A1表达低的患者，并且在转移组织中COL8A1更高。通过Transwell实验发现COL8A1促进乳腺癌细胞迁移和侵袭，促进乳腺癌细胞中金属蛋白酶的表达。阻断COL8A1抑制EMT相关因子中间质细胞标志物N-cadherin、Snail的表达，提高上皮细胞标志物E-Cadherin的表达，表明COL8A1改变乳腺癌细胞EMT表型。联合AKT抑制剂和过表达AKT，发现AKT在COL8A1介导的乳腺癌细胞转移中发挥作用。裸鼠尾静脉肿瘤细胞动物模型发现抑制COL8A1能够降低乳腺癌细胞体内转移能力，且AKT活性、EMT发生受到抑制。研究发现两种天然小分子通过抑制AKT发挥抗炎、抗癌作用。本研究证实COL8A1与乳腺癌肿瘤细胞恶性行为相关，高表达COL8A1提示患者预后不良。体内外实验证明COL8A1通过活化AKT信号调节乳腺癌细胞EMT进而促进转移。本研究说明COL8A1参与乳腺癌发生和转移，靶向COL8A1和阻断下游AKT通路可以达到抑制肿瘤的作用。