Kuo Po-Lin, Liao Szi-Hui, Hung Jen-Yu, Huang Ming-Shyan, Hsu Ya-Ling
Institute of Clinical Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Biochim Biophys Acta. 2013 Jun;1830(6):3756-66. doi: 10.1016/j.bbagen.2013.02.022. Epub 2013 Mar 1.
Bone is a common site of metastasis for lung cancer, and is associated with significant morbidity and a dismal prognosis. MicroRNAs (miRNAs) are increasingly implicated in regulating the progression of malignancies.
The efficacy of miR-33a or anti-miR-33a plasmid was assessed by Real-time PCR. Luciferase assays were using One-Glo Luciferase Assay System. Measurement of secreted factors was determined by ELISA kit.
We have found that miR-33a, which is downregulated in lung cancer cells, directly targets PTHrP (parathyroid hormone-related protein), a potent stimulator of osteoclastic bone resorption, leading to decreased osteolytic bone metastasis. We also found that miR-33a levels are inversely correlated with PTHrP expression between human normal bronchial cell line and lung cancer cell lines. The reintroduction of miR-33a reduces the stimulatory effect of A549 on the production of osteoclastogenesis activator RANKL (receptor activator of nuclear factor kappa-B ligand) and M-CSF (macrophage colony-stimulating factor) on osteoblasts, while the expression of PTHrP is decreased in A549 cells. miR-33a overexpression also reduces the inhibitory activity of A549 on the production of OPG (osteoprotegerin), an osteoclastogenesis inhibitor. In addition, miR-33a-mediated PTHrP downregulation results in decreased IL-8 secretion in A549, which contributes to decreased lung cancer-mediated osteoclast differentiation and bone resorption.
These findings have led us to conclude that miR-33a may be a potent tumor suppressor, which inhibits direct and indirect osteoclastogenesis through repression of PTHrP.
miR-33a may even predict a poor prognosis for lung cancer patients.
骨是肺癌常见的转移部位，与显著的发病率和不良预后相关。微小RNA（miRNA）越来越多地参与调节恶性肿瘤的进展。
通过实时PCR评估miR-33a或抗miR-33a质粒的疗效。使用One-Glo荧光素酶检测系统进行荧光素酶检测。通过ELISA试剂盒测定分泌因子。
我们发现，在肺癌细胞中表达下调的miR-33a直接靶向甲状旁腺激素相关蛋白（PTHrP），这是一种破骨细胞骨吸收的强效刺激因子，可导致溶骨性骨转移减少。我们还发现，在人正常支气管细胞系和肺癌细胞系之间，miR-33a水平与PTHrP表达呈负相关。重新引入miR-33a可降低A549对破骨细胞生成激活剂核因子κB受体激活剂配体（RANKL）和巨噬细胞集落刺激因子（M-CSF）在成骨细胞上产生的刺激作用，而A549细胞中PTHrP的表达降低。miR-33a过表达还可降低A549对破骨细胞生成抑制剂骨保护素（OPG）产生的抑制活性。此外，miR-33a介导的PTHrP下调导致A549中白细胞介素-8分泌减少，这有助于减少肺癌介导的破骨细胞分化和骨吸收。
这些发现使我们得出结论，miR-33a可能是一种有效的肿瘤抑制因子，通过抑制PTHrP来抑制直接和间接的破骨细胞生成。
miR-33a甚至可能预示肺癌患者的预后不良。
