5E10: a prostate-specific surface-reactive monoclonal antibody Oskar W. Rokhlin a, *, George J. Weiner b , Michael B. Cohen a,c,d a Department of Pathology, University of Iowa, 118 ML, Iowa City, IA 52242, USA b Department of Internal Medicine, University of Iowa, Iowa City, IA, USA c Department of Urology, University of Iowa, Iowa City, IA, USA d University of Iowa Cancer Center, University of Iowa, Iowa City, IA, USA Received 24 September 1997; received in revised form 26 November 1997; accepted 26 November 1997 Abstract We created mAb that reacted solely with prostate epithelial cells. The strategy involved immunizing mice with a mixture of six different prostatic carcinoma cell lines and selecting by flow cytometry only those antibodies that bind whole cells. The primary screening was performed using a mixture of all six prostate cell lines used in immunization together with six non- prostate cell lines in the same tube. Antibodies that gave a bimodal pattern of surface staining were selected for further evaluation. The most attractive clone, designated 5E10, produced IgG1 mAb that recognized four of the six prostatic cell lines and did not react with non-prostate tumor cell lines, peripheral blood and bone marrow mononuclear cells and endothelial and bone marrow stromal cells. 5E10 mAb reacted with both benign and malignant prostate in eight of eight histological samples and no reactivity was noted with non-prostate normal tissues. The 5E10 antigen is a transmembrane glycoprotein with a molecular weight of 110 kDa and the epitope recognized by 5E10 is extracellular. Ongoing studies are exploring the nature of this antigen in more depth.  1998 Published by Elsevier Science Ireland Ltd. All rights reserved Keywords: Prostatic neoplasms; Surface antigen; Monoclonal antibody 1. Introduction The incidence of prostate cancer is increasing in the USA. In 1996, prostate cancer accounted for 41% of the new cancer diagnoses in American men and was estimated to have been responsible for about 41 000 deaths in 1996 [1]. Current effective treatment ap- proaches include surgery, radiation and hormonal therapy. These can control local disease in the prostate and palliate metastatic disease. Unfortunately, at the present time there are no curative therapies for the significant percentage of patients that present with metastatic disease or develop metastatic disease after local therapy. New treatment modalities are clearly needed. Recent clinical trials have shown that tumor-speci- fic monoclonal antibodies (mAbs) will likely have a significant role in the management of cancer. For example, radiolabeled mAbs can be effective as ima- ging agents in cancer patients [2,3]. Therapy studies are also very promising and have shown that mAbs can lead to tumor regression in a significant percen- Cancer Letters 131 (1998) 129–136 0304-3835/98/$ - see front matter  1998 Published by Elsevier Science Ireland Ltd. All rights reserved PII S0304-3835(98)00150-5 * Corresponding author. Tel.: +1 319 3358214; fax: +1 319 3358348.