Tsai C M, Chang K T, Perng R P, Mitsudomi T, Chen M H, Kadoyama C, Gazdar A F
Chest Department, Veterans General Hospital-Taipei, Taiwan.
J Natl Cancer Inst. 1993 Jun 2;85(11):897-901. doi: 10.1093/jnci/85.11.897.
At diagnosis, most small-cell lung cancers (SCLCs) are chemosensitive, whereas non-small-cell lung cancers (NSCLCs) are usually chemoresistant. Activation of ras genes and HER-2/neu genes (also known as ERBB2) is encountered in subpopulations of NSCLC but not in SCLC and has been linked to shortened survival. Therefore, activation of these genes may be associated with intrinsic chemoresistance in NSCLC. Studies have also suggested that the multidrug-resistant phenotype expressed by the MDR1 gene (also known as PGY1) does not correlate with the in vitro chemosensitivity of NSCLC cells or with clinical response to therapy and does not explain the spectrum of cross-resistance to drugs.
The purpose of this study was to investigate the relationships between chemoresistance and the presence of ras gene point mutations and overexpression of the HER-2/neu gene in NSCLC cell lines, which indicates gene activation.
Using a panel of 20 NSCLC cell lines established from untreated patients, we assessed the differences in HER-2/neu messenger RNA (mRNA) expression in the cell lines with or without ras mutations. We performed in vitro drug sensitivity testing by the tetrazolium-based MTT [i.e., 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H- tetrazolium bromide] assay with doxorubicin, carmustine, cisplatin, melphalan, mitomycin, and etoposide, and we determined the differences in IC50 values (i.e., the drug concentrations required to inhibit cell growth by 50%) for the cell lines.
We found a statistically significant correlation between the IC50 values for all six drugs and the degree of HER-2/neu gene expression in all 20 cell lines (r = .67-.86; P < .005) as well as in the subpopulation of eight cell lines with ras mutations (r = .83-.98; P < .05). The IC50 values for doxorubicin, carmustine, cisplatin, and melphalan were not significantly different in the cell lines with or without ras mutations, but the values for mitomycin and etoposide in lines with ras mutations were slightly lower than in those without ras mutations (borderline significance, P = .031). Levels of HER-2/neu expression in cell lines with ras mutations were lower than those without ras mutations, but the difference was not statistically significant.
Our findings indicate that overexpression of HER-2/neu is a marker for intrinsic multidrug resistance in NSCLC cell lines.
If the clinical relevance of our findings is confirmed, HER-2/neu gene expression can be used as a predictor of therapeutic failure in NSCLCs. The relationships between HER-2/neu gene expression, cell proliferation, and chemoresistance in NSCLC require further investigation.
在诊断时，大多数小细胞肺癌（SCLC）对化疗敏感，而非小细胞肺癌（NSCLC）通常对化疗耐药。Ras基因和HER-2/neu基因（也称为ERBB2）的激活在NSCLC亚群中存在，但在SCLC中不存在，并且与生存期缩短有关。因此，这些基因的激活可能与NSCLC的内在化疗耐药性相关。研究还表明，MDR1基因（也称为PGY1）所表达的多药耐药表型与NSCLC细胞的体外化疗敏感性或临床治疗反应无关，也无法解释对药物的交叉耐药谱。
本研究的目的是调查NSCLC细胞系中化疗耐药性与ras基因点突变的存在以及HER-2/neu基因过表达之间的关系，后者表明基因激活。
使用从未经治疗的患者中建立的一组20个NSCLC细胞系，我们评估了有或无ras突变的细胞系中HER-2/neu信使核糖核酸（mRNA）表达的差异。我们通过基于四氮唑的MTT[即3-(4,5-二甲基-2-噻唑基)-2,5-二苯基-2H-溴化四氮唑]法，使用阿霉素、卡莫司汀、顺铂、美法仑、丝裂霉素和依托泊苷进行体外药物敏感性测试，并确定了各细胞系的IC50值（即抑制细胞生长50%所需的药物浓度）的差异。
我们发现，所有六种药物的IC50值与所有20个细胞系中HER-2/neu基因的表达程度之间存在统计学上的显著相关性（r = 0.67 - 0.86；P < 0.005），在八个有ras突变的细胞系亚群中也是如此（r = 0.83 - 0.98；P < 0.05）。有或无ras突变的细胞系中，阿霉素、卡莫司汀、顺铂和美法仑的IC50值没有显著差异，但有ras突变的细胞系中丝裂霉素和依托泊苷的值略低于无ras突变的细胞系（临界显著性，P = 0.031）。有ras突变的细胞系中HER-2/neu的表达水平低于无ras突变的细胞系，但差异无统计学意义。
我们的研究结果表明，HER-2/neu的过表达是NSCLC细胞系中内在多药耐药的一个标志物。
如果我们研究结果的临床相关性得到证实，HER-2/neu基因表达可作为NSCLC治疗失败的一个预测指标。NSCLC中HER-2/neu基因表达、细胞增殖和化疗耐药性之间的关系需要进一步研究。
