dos Santos N R, Torensma R, de Vries T J, Schreurs M W, de Bruijn D R, Kater-Baats E, Ruiter D J, Adema G J, van Muijen G N, van Kessel A G
Department of Human Genetics, University Hospital Nijmegen, The Netherlands.
Cancer Res. 2000 Mar 15;60(6):1654-62.
The SSX genes, located on the X chromosome, encode a family of highly homologous nuclear proteins. The SSX1 and SSX2 genes were initially identified as fusion partners of the SYT gene in t(X;18)-positive synovial sarcomas. Recently, however, it was found that these two genes, as well as the highly homologous SSX4 and SSX5 genes, are aberrantly expressed in different types of cancers, including melanomas. Because normal SSX expression has been detected only in the testis and, at very low levels, the thyroid, these proteins are considered as new members of the still growing family of cancer/testis antigens. These antigens are presently considered as targets for the development of cancer immunotherapy protocols. In the present study, we developed a monoclonal antibody found to recognize SSX2, SSX3, and SSX4 proteins expressed in formaldehyde-fixed and paraffin-embedded tissues. This antibody was used to investigate SSX expression in normal testis and thyroid, benign melanocytic lesions, melanoma lesions, and melanoma cell lines. SSX nuclear expression in the testis was found to be restricted to spermatogenic cells, mainly spermatogonia. Of 18 melanoma cell lines analyzed, 9 showed SSX RNA and protein expression, although heterogeneously and at variable levels. Treatment of an SSX-negative cell line with 5-aza-2'-deoxycytidine, a demethylating agent, led to SSX RNA and protein expression, indicating a role for methylation in transcription regulation. Thirty-four of 101 primary and metastatic melanoma cases and 2 of 24 common nevocellular and atypical nevus cases showed SSX nuclear staining. Again, SSX expression was heterogeneous, ranging from widespread to scarce. Our findings stress the importance of assessing the a priori SSX expression status of melanoma cases that may be selected for immunotherapeutic trials.
SSX基因位于X染色体上，编码一族高度同源的核蛋白。SSX1和SSX2基因最初被鉴定为t(X;18)阳性滑膜肉瘤中SYT基因的融合伴侣。然而，最近发现这两个基因以及高度同源的SSX4和SSX5基因在包括黑色素瘤在内的不同类型癌症中异常表达。由于仅在睾丸以及甲状腺中检测到极低水平的正常SSX表达，这些蛋白被认为是不断增加的癌/睾丸抗原家族的新成员。目前这些抗原被视为癌症免疫治疗方案开发的靶点。在本研究中，我们开发了一种单克隆抗体，发现它能识别在甲醛固定石蜡包埋组织中表达的SSX2、SSX3和SSX4蛋白。该抗体用于研究正常睾丸和甲状腺、良性黑素细胞病变、黑色素瘤病变及黑色素瘤细胞系中的SSX表达。发现睾丸中的SSX核表达仅限于生精细胞，主要是精原细胞。在所分析的18个黑色素瘤细胞系中，9个显示出SSX RNA和蛋白表达，尽管表达不均一且水平各异。用去甲基化剂5-氮杂-2'-脱氧胞苷处理一个SSX阴性细胞系，导致了SSX RNA和蛋白表达，表明甲基化在转录调控中起作用。101例原发性和转移性黑色素瘤病例中的34例以及24例普通痣细胞痣和非典型痣病例中的2例显示出SSX核染色。同样，SSX表达是不均一的，从广泛表达到稀少表达不等。我们的发现强调了评估可能被选入免疫治疗试验的黑色素瘤病例的先验SSX表达状态的重要性。
