Characterization and expression of CT45 in Hodgkin's lymphoma.
OBJECTIVE
The monoclonal antibody Ki-A10 (IgG1) generated after immunization of mice with Hodgkin's lymphoma cell line L428 detects a nuclear antigen in human tissues with a restricted distribution pattern similar to cancer/testis antigens. The aim of this study was to characterize the antigen and to determine the expression profile in Hodgkin's lymphoma.


METHODS
The half-life and phosphorylation of the antigen were determined by radiolabeling. The antigen was characterized by immunopurification and sequencing. Demethylation of genes is used to induce cancer/testis antigens. Ki-A10-negative cells were treated with 5-aza-2'-deoxycytidine. The Ki-A10 expression in paraffin-embedded tumors was determined immunohistochemically.


RESULTS
Immunopurification of the 25/22-kDa antigen and sequencing revealed a peptide of 14 amino acids corresponding to the gene product of the newly described gene family MGC27005, located on chromosome Xq26.3, now termed CT45. CT45 is significantly phosphorylated and down-regulated during mitosis. Demethylation of CT45-negative HeLa cells and stimulated peripheral blood lymphocytes induced CT45 expression. Except testis, immunohistochemical stainings of normal tissues, reactive lymphoid lesions, and most malignant tumors were negative. In comparison, 54 of 99 (55%) samples from pediatric and adolescent Hodgkin's lymphoma patients enrolled in the multicenter trial HD-95 stained Ki-A10 positive. Ki-A10 expression correlated with histologic subtypes (nodular sclerosis Hodgkin's lymphoma 68% versus mixed cellularity Hodgkin's lymphoma 40% versus nodular lymphocyte predominant Hodgkin's lymphoma 9%; P < 0.001).


CONCLUSIONS
Ki-A10 is the first monoclonal antibody that detects CT45. As benign lymphoid lesions did not express CT45, the use of Ki-A10 antibody will facilitate the discrimination of Hodgkin's lymphoma from reactive lymphadenopathies.
Heidebrecht
Hans-Jürgen
HJ
Department of Hematopathology and Lymph Node Registry, University of Kiel, Kiel, Germany. hheidebrecht@path.uni-kiel.de
Claviez
Alexander
A
Kruse
Marie Luise
ML
Pollmann
Marc
M
Buck
Friedrich
F
Harder
Sönke
S
Tiemann
Markus
M
Dörffel
Wolfgang
W
Parwaresch
Reza
R
D000293:Adolescent; D000911:Antibodies, Monoclonal / Q000276:immunology; D000951:Antigens, Neoplasm / Q000096:biosynthesis* / Q000276:immunology / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D005260:Female; D006367:HeLa Cells; D006689:Hodgkin Disease / Q000276:immunology* / Q000473:pathology; D006801:Humans; D008223:Lymphoma / Q000276:immunology / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; C502804:CT45A1 protein, human