Penno M B, Askin F B, Ma H, Carbone M, Vargas M P, Pass H I
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, USA.
Cancer J Sci Am. 1995 Sep-Oct;1(3):196-203.
Malignant pleural mesothelioma is a rare malignancy with major environmental implications regarding passive asbestos exposure. We have conducted an immunohistochemical and functional study to address three questions: (1) What is the representation of CD44 on tumor cells as detected by immunohistochemistry? (2) Do cultured cell lines derived from malignant pleural mesothelioma tissue express the same CD44 phenotypes as the original tumors, and can they serve as a model for the study of CD44 in mesotheliomas? (3) What is the functional status of the CD44 expressed on mesotheliomas, with regard to hyaluronan anchorage?
Thirty-seven samples of pleural mesothelioma were obtained from patients entered on phase I/II protocols conducted in the Surgery Branch of the National Cancer Institute since 1991. The diagnosis was confirmed in all 37 patients by means of a battery of immunohistochemical tests for markers differentiating malignant pleural mesothelioma from adenocarcinoma. Tumor-positive lymph nodes and distant metastases were also examined in six of the patients. Cell lines, established from tumor tissue of six of the patients described above, were used in these experiments. Four (H2596, H2461, H2373, H2452) were derived from primary solid tumors and two (HP-1 and HP-3) were derived from effusions.
Immunohistochemical staining with a monoclonal antibody (H4C4) that recognizes a constant region of human CD44 demonstrated that 34 (92%) of the malignant pleural mesotheliomas examined expressed CD44 on 50% to 100% of their cells. The extent of CD44 expression was apparently related to histologic subtype with the highest expression seen in epithelioid mesotheliomas and the least in sarcomatoid tumors. Tumor cell lines established from the primary tumors or effusions of six of the malignant pleural mesothelioma patients showed high expression of the hematopoietic form of CD44. Four of these cell lines exhibited strong attachment to hyaluronan in an in vitro attachment assay, indicating that their CD44 was functional with respect to hyaluronan anchorage. Hyaluronan attachment was specific in that it could be abolished by preincubation with epitope-specific anti-CD44 antibodies or soluble substrate or by hyaluronidase treatment of attachment surfaces.
We conclude that CD44 is highly expressed on human mesotheliomas, that cell lines adequately represent tumor expression, and that CD44 mediates association with hyaluronan, a major component of pleural fluid.
恶性胸膜间皮瘤是一种罕见的恶性肿瘤，在被动接触石棉方面具有重大环境影响。我们进行了一项免疫组织化学和功能研究，以解决三个问题：（1）通过免疫组织化学检测，肿瘤细胞上CD44的表达情况如何？（2）源自恶性胸膜间皮瘤组织的培养细胞系是否表达与原始肿瘤相同的CD44表型，它们能否作为间皮瘤中CD44研究的模型？（3）就透明质酸锚定而言，间皮瘤上表达的CD44的功能状态如何？
自1991年以来，从美国国立癌症研究所外科分部开展的I/II期方案入组患者中获取了37份胸膜间皮瘤样本。通过一系列用于区分恶性胸膜间皮瘤与腺癌的标志物的免疫组织化学检测，在所有37例患者中均确诊了诊断。还对其中6例患者的肿瘤阳性淋巴结和远处转移灶进行了检查。在这些实验中使用了从上述6例患者的肿瘤组织建立的细胞系。其中4株（H2596、H2461、H2373、H2452）源自原发性实体瘤，2株（HP-1和HP-3）源自胸腔积液。
用识别人类CD44恒定区的单克隆抗体（H4C4）进行免疫组织化学染色显示，在所检查的34例（92%）恶性胸膜间皮瘤中，50%至100%的细胞表达CD44。CD44的表达程度显然与组织学亚型有关，在上皮样间皮瘤中表达最高，在肉瘤样肿瘤中表达最低。从6例恶性胸膜间皮瘤患者的原发性肿瘤或胸腔积液中建立的肿瘤细胞系显示造血形式的CD44高表达。在体外黏附试验中，其中4株细胞系对透明质酸表现出强烈黏附，表明它们的CD44在透明质酸锚定方面具有功能。透明质酸黏附具有特异性，因为用表位特异性抗CD44抗体或可溶性底物预孵育或对黏附表面进行透明质酸酶处理可消除这种黏附。
我们得出结论，CD44在人恶性胸膜间皮瘤上高表达，细胞系能充分代表肿瘤表达，且CD44介导与透明质酸的结合，透明质酸是胸腔积液的主要成分。
