You L, Jakowlew S B
National Cancer Institute, Medicine Branch, Rockville, Maryland 20850, USA.
Am J Respir Cell Mol Biol. 1997 Nov;17(5):617-24. doi: 10.1165/ajrcmb.17.5.2843.
Cellular regulatory genes including transcription factors may play an important role in the induction, maintenance, and progression of lung cancer. These regulatory genes are inducible by various mitogenic stimuli including phorbol myristate acetate (PMA). The differential mRNA display method was used to identify potential early response genes regulated by PMA in non-small cell lung cancer (NSCLC) cell lines. Using this technique, several cDNA fragments were found to be potentially differentially regulated by PMA in the squamous NSCLC cell line NCI-H157. One of these cDNA fragments of approximately 100 bp was determined to be differentially induced by at least 30-fold by PMA by northern blot analysis and to hybridize to a single 3.4 kb mRNA species. This cDNA fragment was cloned, sequenced, and identified to be identical to a portion of the 3'-untranslated region of the human early growth response gene-1 (Egr-1). Using Egr-1 cDNA as a probe, it was demonstrated that PMA induces Egr-1 mRNA expression in at least three other NSCLC cells as well. In addition, PMA caused a transient increase in expression of the Egr-1 transcript reaching a maximum level by 1 h before decreasing in NCI-H157 and three other types of NSCLC cells. Treatment of these NSCLC cells with TGF-beta1 showed a transient increase in Egr-1 mRNA similar to PMA which also reached a maximum level after 1 h. Normal human bronchial epithelial (NHBE) cells also showed a rapid, transient increase in expression of Egr-1 mRNA after treatment with PMA. In contrast, treatment of NHBE cells with TGF-beta1 showed that expression of Egr-1 mRNA increased by 1 h but reached a maximum level only after 6 h. These results indicate that both PMA and TGF-beta1 can induce Egr- mRNA expression in NSCLC cells and NHBE cells; however, while PMA induces Egr-1 mRNA similarly in both cell types, TGF-beta1 induces Egr-1 mRNA expression more rapidly and more transiently in NSCLC cells than in NHBE cells. Our results suggest that Egr-1 may play different roles in response to mitogens in normal and malignant lung cells.
包括转录因子在内的细胞调节基因可能在肺癌的诱导、维持和进展中发挥重要作用。这些调节基因可被包括佛波酯肉豆蔻酸酯乙酸酯（PMA）在内的各种促有丝分裂刺激所诱导。采用差异mRNA显示法来鉴定非小细胞肺癌（NSCLC）细胞系中受PMA调控的潜在早期反应基因。运用该技术，在鳞状NSCLC细胞系NCI-H157中发现了几个可能受PMA差异调控的cDNA片段。通过Northern印迹分析，其中一个约100 bp的cDNA片段被确定受PMA差异诱导至少30倍，并与一个单一的3.4 kb mRNA种类杂交。该cDNA片段被克隆、测序，并被鉴定与人早期生长反应基因-1（Egr-1）的3'-非翻译区的一部分相同。以Egr-1 cDNA为探针，证实PMA在至少其他三种NSCLC细胞中也诱导Egr-1 mRNA表达。此外，PMA导致Egr-1转录本表达短暂增加，在NCI-H157和其他三种类型的NSCLC细胞中，在1小时达到最高水平，随后下降。用转化生长因子-β1（TGF-β1）处理这些NSCLC细胞，显示Egr-1 mRNA短暂增加，类似于PMA，也在1小时后达到最高水平。正常人支气管上皮（NHBE）细胞在用PMA处理后，Egr-1 mRNA表达也迅速短暂增加。相反，用TGF-β1处理NHBE细胞显示，Egr-1 mRNA表达在1小时增加，但仅在6小时后达到最高水平。这些结果表明，PMA和TGF-β1均可在NSCLC细胞和NHBE细胞中诱导Egr-1 mRNA表达；然而，虽然PMA在两种细胞类型中诱导Egr-1 mRNA的方式相似，但TGF-β1在NSCLC细胞中比在NHBE细胞中更迅速、更短暂地诱导Egr-1 mRNA表达。我们的结果表明，Egr-1在正常和恶性肺细胞对有丝分裂原的反应中可能发挥不同作用。
