REACTIVITY OF ANTI-ARAC-RESISTANT CELL MONOCLONAL-ANTIBODY, YU-311, IN FORMALIN-FIXED PARAFFIN-EMBEDDED SPECIMENS OF VARIOUS HEMATOPOIETIC DISORDERS

YU-311 is a monoclonal antibody reacting with cytosine arabinoside (Ar aC)-resistant human leukemic cell line and identifies a 92kDa membrane protein. We have examined YU-311 reactivity with various hematopoieti c disorders by an immunohistochemical method and evaluated a correlati on between YU-311 expression and refractoriness to chemotherapy, retro spectively. YU-311 reacted with AraC-resistant human leukemia cell lin es, in which a 92 kDa membrane protein was identified by Western blott ing, whereas drug-resistant cell lines to other than AraC failed to ex press YU-311 antigen. The frequency of YU-311 positivity was significa ntly increased in relapsed cases, Only five cases were positive for YU -311 at diagnosis and 24 cases at relapse. Unexpectedly, only eight ca ses of relapsed leukemia/lymphoma expressed YU-311 and P-glycoprotein simultaneously, Most of the YU-311-positive relapsed cases showed clin ical refractoriness for chemotherapy and then failed to induct complet e remission or relapsed at short periods with short disease-free durat ion. These findings indicate that YU-311 expression is closely associa ted with some aspects of drug resistance, especially with AraC resista nce, Copyright (C) 1996 Elsevier Science Ltd.