Center for Experimental Medicine, Institute of Biochemistry and Signal Transduction, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
Center for Experimental Medicine, Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
Cells. 2021 Feb 18;10(2):430. doi: 10.3390/cells10020430.
Bone metastases frequently occur in breast cancer patients and lack appropriate treatment options. Hence, understanding the molecular mechanisms involved in the multistep process of breast cancer bone metastasis and tumor-induced osteolysis is of paramount interest. The serine/threonine kinase AKT plays a crucial role in breast cancer bone metastasis but the effect of individual AKT isoforms remains unclear. Therefore, AKT isoform-specific knockdowns were generated on the bone-seeking MDA-MB-231 BO subline and the effect on proliferation, migration, invasion, and chemotaxis was analyzed by live-cell imaging. Kinome profiling and Western blot analysis of the TGFβ/CTGF axis were conducted and metastasis was evaluated by intracardiac inoculation of tumor cells into NOD scid gamma (NSG) mice. MDA-MB-231 BO cells exhibited an elevated AKT3 kinase activity in vitro and responded to combined treatment with AKT- and mTOR-inhibitors. Knockdown of AKT3 significantly increased migration, invasion, and chemotaxis in vitro and metastasis to bone but did not significantly enhance osteolysis. Furthermore, knockdown of AKT3 increased the activity and phosphorylation of pro-metastatic HER2 and DDR1/2 but lowered protein levels of CTGF after TGFβ-stimulation, an axis involved in tumor-induced osteolysis. We demonstrated that AKT3 plays a crucial role in bone-seeking breast cancer cells by promoting metastatic potential without facilitating tumor-induced osteolysis.
乳腺癌患者常发生骨转移，且缺乏合适的治疗选择。因此，深入了解乳腺癌骨转移和肿瘤诱导性溶骨性这一多步骤过程中涉及的分子机制至关重要。丝氨酸/苏氨酸激酶 AKT 在乳腺癌骨转移中发挥着关键作用，但各 AKT 同工型的作用尚不清楚。因此，在觅骨性 MDA-MB-231 BO 亚系中生成 AKT 同工型特异性敲低，并通过活细胞成像分析对增殖、迁移、侵袭和趋化作用进行分析。对 TGFβ/CTGF 轴进行激酶组分析和 Western blot 分析，并通过将肿瘤细胞心内接种到 NOD scid gamma (NSG) 小鼠中来评估转移。体外研究显示 MDA-MB-231 BO 细胞中 AKT3 激酶活性升高，并对 AKT 和 mTOR 抑制剂联合治疗有反应。AKT3 敲低显著增加了体外迁移、侵袭和趋化作用以及骨转移，但并未显著增强溶骨性。此外，AKT3 敲低增加了 HER2 和 DDR1/2 的促转移活性和磷酸化，但在 TGFβ 刺激后降低了 CTGF 的蛋白水平，该轴参与了肿瘤诱导性溶骨性。我们证明，AKT3 通过促进转移潜能而不是促进肿瘤诱导性溶骨性在觅骨性乳腺癌细胞中发挥关键作用。
