Astrocyte-elevated gene-1基因可調控增加thymidylate synthase的過度表現造成非小細胞肺癌pemetrexed治療後產生抗藥性

Abstract

先前的研究發現astrocyte-elevated gene-1(AEG-1)基因表現與各種抗癌化學治療藥物抗藥性產生的機制有關。故本研究用以探討非小細胞肺癌細胞內AEG-1基因的表現量對thymidylate synthase(TS)調控的作用，以及是否因AEG-1的過度表現進而帶動增加TS的表達，因此造成pemetrexed治療後產生抗藥性。本實驗發現在不同的肺癌細胞株內，TS的表現量與AEG-1的表現量同步，TS的表現量愈高者，AEG-1的表現量也愈高。於肺癌細胞株內TS的表現量較低者，pemetrexed藥物的有效半抑制濃度值(IC50)也較低。本研究同時製造了對pemetrexed具有抗藥性的肺癌PC-9細胞株 (PC-9R-A)，證明轉染了AEG-1 siRNA後，AEG-1表現量減少同時降低了TS的表現，也降低了pemetrexedIC50值。相反的當AEG-1基因有過度表現時，則同時增加了TS表現和pemetrexedIC50值。而轉染了TS siRNA後，雖降低了TS表現，也降低了部分pemetrexedIC50值，但對AEG-1的表現量則沒有產生影響，由此推論TS的表現是受到AEG-1之調控。另外在臨床非小細胞患者切片樣本的免疫組織化學染色顯示，癌細胞內TS蛋白質表現量較低的患者，在接受pemetrexed合併鉑類藥物為第一線化學藥物注射時有較佳的治療反應率，而AEG-1蛋白質表現量較低的患者在接受pemetrexed治療時，可擁有較長的無疾病惡化存活期與整體存活時間。此外當肺腺癌患者在接受pemetrexed治療，從一開始有效的治療到發現疾病惡化時，經過再切片樣本組織的分析，從疾病診斷開始到肺癌經治療後再發生惡化時，發現TS表現量的明顯增加，而AEG-1表現量同時也顯著增加。因此綜合以上我們的研究結果顯示，TS的表現可以受到AEG-1表現量的調控，而這些基因表現量的增加，與非小細胞肺癌疾病的惡化有關，並且可能與pemetrexed治療後產生抗藥性相關。

Previous studies have suggested that astrocyte-elevated gene-1(AEG-1) contributes to the mechanisms of resistance to various chemotherapeutics. In this study, we investigated whether AEG-1 expression level correlated with that of thymidylate synthase(TS), as higher TS expression is known to be associated with the resistance to pemetrexed chemotherapy in patients with advanced lung adenocarcinoma. Using pemetrexed-resistant lung adenocarcinoma PC-9 cell line, we demonstrated that transfection of AEG-1 siRNA lowered TS expression and decreased pemetrexed IC50 value. In contrast, overexpression of AEG-1 was associated with increased expression of TS and higher pemetrexed IC50 value. Immunohistochemical staining of clinical biopsy samples showed that patients with lower AEG-1 expression had longer overall survival time. Moreover, analysis of repeated biopsy samples revealed that an increase in the TS level from baseline to disease progression was significantly associated with the elevation of AEG-1 expression. In conclusion, our data demonstrated that TS expression might be regulated by AEG-1 and that increased expression of these proteins contributes to lung cancer disease progression and may be associated with the development of resistance to pemetrexed.