E1A基因对头颈部淋巴结转移鳞癌细胞体外生长的抑制和化放疗增敏的作用

Effect of E1A Gene on In Vitro Growth Inhibition and Radiochemosensitivity of Lymph Node Metastasis Cells of Human Head and Neck Squamous Cell Carcinoma

背景与目的:腺病毒5型早期区1A基因(early region 1A,E1A)是新近发现的一个具有抑癌作用的基因,E1A蛋白能够从正、负两种途径调控多种基因的表 达,具有诱导肿瘤细胞分化、逆转其恶性表型、降低其体内致瘤性和抗转移等活性,但E1A基因在头颈淋巴结转移鳞癌治疗中的作用尚少见报道。本研究的目的是探讨E1A基因对头颈淋巴结转移鳞癌细胞体外生长的抑制作用和化、放疗增敏作用及其初步的作用机理。方法:经脂质体介导,将真核细胞高效表达E1A基因的重组质粒peDNA3-E1A导入人舌鳞癌的淋巴结转移癌细胞系686LN-1。通过测绘生长曲线和计算倍增时间,观察E1A基因对该细胞系生长的抑制作用。用MTT法测定转染E1A基因前后,癌细胞对顺铂、泰素、5-氟尿嘧啶和博来霉素等化疗药物以及放疗敏感性的改变。流式细胞术和免疫细胞化学染色检测转染前后的细胞周期分布以及p53和HER-2/neu表达情况。结果:转染E1A基因细胞群体生长缓慢,倍增时间延长(是转染空载体细胞的1.48倍)。与686LN-1-vect比较,686LN-1-E1A细胞对顺铂、博来霉素、泰素和射线的敏感性(IC_(50))分别提高了8倍、20倍、10倍和1倍。细胞周期出现G_2/M期阻滞;免疫细胞化学染色显示E1A基因能抑制HER-2/neu的表达。

BACKGROUND & OBJECTIVE: Adenovirus type 5 early region 1A (E1A) gene has been found to be a tumor suppression gene recently. The protein of E1A gene regulates the expression of many cellular genes positively or negatively, and possesses the activities of inducing differentiation of tumor cell, reversing of malignant phenotype, anti-carcinogenesis and anti-metastasis. Study of E1A protein on the treatment of lymph node metastasis of human head and neck squamous cell carcinoma (HNSCC) was not reported. This study was designed to investigate the growth inhibition and radiochemosensitivity of E1A gene on human lymph node metastasis cell line 686LN-1 derived from the patient with human tongue squamous cell carcinoma in vitro and its mechanism. METHODS: The pcDNA3-E1A recombinant plasmid, designed for high-level expression of E1A gene in a variety of eukaryotic cell lines, was transfected into 686LN-1 cells mediated by lipofectamine? To observe the growth inhibition of E1A gene on the cells, the growth curve and doubling time were investigated. Cells before and after transfection were treated with cisplatin, paclitaxel, bleomycin, and 5-fluorouracil (5-FU) for 24 hours or irradiation, respectively, then the changes of sensitivity were tested by MTT assay. The redistributions of cell cycle were analyzed by flow cytometry. Immunocytochemical staining was used to detect the expression of p53 and HER-2/neu. RESULTS: Compared with the vector-transfected cells (686LN-1-vect ceils), the E1 A-transfected cells (686LN-1-E1A cells) grew slowly, and the doubling time elongated (1.41-fold). 686LN-1-E1A cells showed distinct sensitivity to the anticancer drugs and irradiation. According to the IC50 value, the sensitivity of 686LN-1-E1A cells increased approximately 8-fold to cisplatin, 20-fold to bleomycin, 10-fold to paclitaxel, 1 -fold to irradiation compared with 686LN-1-vect cells. However, the sensitivity to 5-FU did not change. The cell cycle was dramatically arrested at G2/M phase in the 686LN-1-E1A cells. E1A gene remarkably suppressed the expression of HER-2/neu gene in 686LN-1-E1A cells. CONCLUSION: E1A gene can significantly inhibit the growth rate of lymph node metastasis cell line 686LN-1 of HNSCC. Moreover, it also slightly enhance the cell sensitivity to antitumor drugs and irradiation. These functions of E1A gene may be associated with its ability to suppress the HER-2/neu expression and to arrest the cell at G2/ M phase.