腐植酸（humic Acid，以下簡稱HA）已被證實為台灣西南沿海烏腳病和多種癌症的致病因子之一。本研究將探討HA對A549肺癌細胞的影響。在不同劑量、時間之HA處理後，由傷口癒合、轉移與侵襲試驗，結果顯示HA會增加細胞的移動生長能力，同時也會增加基質黏附能力。另外，由zymography分析結果，發現A549細胞以不同濃度HA處理後，ECM蛋白水解、基質金屬水解蛋白(MMP-9和MMP-2)表現量會增加，且其上游調控蛋白包括FAK、PAK、 ERK1/2、Jun、p38 MAPK及AKT等之蛋白其磷酸化的情形也增加。
綜合以上實驗結果，腐植酸可能經由integrin訊息傳遞、MAPKs和PI3K/Akt訊息傳遞系統調控MMP-9和MMP-2表現量，進而促進A549肺癌細胞轉移。
Humic acid (HA), a group of high-molecular weight polymer, resulting from the decompositing of organic matter has been implicated as a possible etiologic factor for Blackfoot disease and cancers. In this study, we observed that humic acid exerted a dose- and time-dependent promoting effect on the motility and invasion ability of a highly metastatic A549 cells under non-cytotoxic concentrations. In vitro wound-healing assay, cell invasion and migration assay, the results showed that A549 cells with HA pretreatment increased the migrating growth. HA was shown to enhance activation of adhesion molecules in A549 cells. In A549 cells migration and invasion processes, matrix-degrading proteinase are required. A549 cells with HA treatment at various concentrations showed increasing activates of ECM proteinase including matrix metalloproteinases (MMP-9 and MMP-2) by using gelatin and casein zymography analysis. The upstream mediators, FAK, PAK, ERK1/2, Jun, P38 MAPK and Akt were activated by increased phosphorylation of the proteins. Our results suggest that HA may promote a metastic effect involving (1) integrin signaling, (2) mitogen-activated protein kinase (MAPK) and PI3K/Akt signaling pathway to regulate the expression of progelatinase in human A549 lung cells.
