title: The absence of CD20 messenger RNA in recurrent cutaneous B-cell lymphoma following rituximab therapy.
abstract: BACKGROUND
  Rituximab has been used to treat relapsed low-grade or advanced non-Hodgkin's lymphoma since 1997, targeting the CD20 antigen expressed by B cells. Single-agent rituximab therapy is safe and well tolerated. Recurrences showing a loss of CD20 expression following rituximab therapy have been reported.
  
  
  METHODS
  Four patients with CD20-positive cutaneous B-cell lymphoma received rituximab therapy with subsequent recurrences. The biopsies were assessed for cytoplasmic CD20 expression; CD20 messenger RNA was also assessed where tissue was available.
  
  
  RESULTS
  Cutaneous relapses occurring within 1.5-3 months following the last dose of rituximab were CD20 negative. In three cases, subsequent relapses showed renewed expression of CD20. Those biopsies demonstrating a loss of surface and cytoplasmic CD20 by immunohistochemistry also showed no evidence of messenger RNA for CD20 using an in situ polymerase chain reaction-based methodology.
  
  
  CONCLUSIONS
  Rituximab may be associated with the emergence of CD20-negative B-cell clones, potentially rendering a tumor insensitive to this drug. Conversely, following cessation of the drug, a re-expression of CD20 within the neoplastic cells may occur allowing therapeutic intervention with this monoclonal antibody. The loss of CD20 expression appears to be a direct effect of the drug on CD20 messenger RNA synthesis.
authors.affiliation: Department of Oral and Maxillofacial Pathology, The Ohio State University, Athens, 43210, USA.
authors.forename: Yeshwant B
authors.initials: YB
authors.lastname: Rawal
authors.forename: Gerard J
authors.initials: GJ
authors.lastname: Nuovo
authors.forename: Gwyn E
authors.initials: GE
authors.lastname: Frambach
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Porcu
authors.forename: Robert A
authors.initials: RA
authors.lastname: Baiocchi
authors.forename: Cynthia M
authors.initials: CM
authors.lastname: Magro
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000032:analysis; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D016393:Lymphoma, B-Cell / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000069283:Rituximab; D012878:Skin Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D012333:RNA, Messenger; D000069283:Rituximab