Clemons M J, Bibby M C, El Teraifi H, Forster G, Kelly J, Banerjee S, Cadman B, Ryder W D J, Howell A, Margison G P
Cancer Research UK Department of Medical Oncology, Christie Hospital, Wilmslow Road, Manchester M20 4BX, UK.
Br J Cancer. 2002 Jun 5;86(11):1797-802. doi: 10.1038/sj.bjc.6600324.
An important determinant of cellular resistance to chemotherapeutic O6-alkylating agents, which comprise methylating and chloroethylating agents, is the ability of cells to repair alkylation damage at the O6-position of guanine in DNA. This is achieved by a specific DNA repair enzyme O6-alkylguanine DNA-alkyltransferase. In this study O6-alkylguanine DNA-alkyltransferase expression was measured in human breast tumours using both biochemical and immunohistochemical techniques. O6-alkylguanine DNA-alkyltransferase activity was then compared with known clinical prognostic indices to assess the potential role of O6-alkylguanine DNA-alkyltransferase in predicting the behaviour of this common malignancy. The application of both biochemical and immunohistochemical techniques was feasible and practical. Most breast tumours expressed high levels of O6-alkylguanine DNA-alkyltransferase. Immunohistochemical analysis showed marked variation in expression not only between individuals but also within individual tumours, and in the same patient, between metastases and between primary tumour and metastatic site. O6-alkylguanine DNA-alkyltransferase activity in tissue extracts significantly correlated not only with immunohistochemical staining intensity determined by subjective quantitation, but also with measures of protein levels using a computerised image analysis system including mean grey (P<0.001), percentage of cells positive for O6-alkylguanine DNA-alkyltransferase (P<0.001), and integrated optical density (P<0.001). O6-alkylguanine DNA-alkyltransferase expression did not correlate with any of the established clinical prognostic indicators for current treatment regimens. However, immunohistochemical offers a rapid and convenient method for assessing potential utility of O6-alkylating agents or O6-alkylguanine DNA-alkyltransferase inactivating agents in future studies of breast cancer treatment.
细胞对包括甲基化剂和氯乙基化剂在内的化疗O6-烷基化剂产生抗性的一个重要决定因素是细胞修复DNA中鸟嘌呤O6位烷基化损伤的能力。这是通过一种特定的DNA修复酶O6-烷基鸟嘌呤DNA烷基转移酶来实现的。在本研究中，使用生化和免疫组化技术检测了人乳腺肿瘤中O6-烷基鸟嘌呤DNA烷基转移酶的表达。然后将O6-烷基鸟嘌呤DNA烷基转移酶活性与已知的临床预后指标进行比较，以评估O6-烷基鸟嘌呤DNA烷基转移酶在预测这种常见恶性肿瘤行为中的潜在作用。生化和免疫组化技术的应用都是可行且实用的。大多数乳腺肿瘤表达高水平的O6-烷基鸟嘌呤DNA烷基转移酶。免疫组化分析显示，不仅个体之间，而且个体肿瘤内部，以及同一患者的转移灶之间、原发肿瘤与转移部位之间，表达都存在显著差异。组织提取物中的O6-烷基鸟嘌呤DNA烷基转移酶活性不仅与主观定量确定的免疫组化染色强度显著相关，而且与使用计算机图像分析系统测量的蛋白质水平显著相关，包括平均灰度（P<0.001）、O6-烷基鸟嘌呤DNA烷基转移酶阳性细胞百分比（P<0.001）和积分光密度（P<0.001）。O6-烷基鸟嘌呤DNA烷基转移酶表达与当前治疗方案的任何既定临床预后指标均无相关性。然而，免疫组化提供了一种快速便捷的方法，可用于评估O6-烷基化剂或O6-烷基鸟嘌呤DNA烷基转移酶失活剂在未来乳腺癌治疗研究中的潜在效用。
