ABSTRACT
BACKGROUND AIMS: Chronic lymphocytic leukemia (CLL) is an indolent disease. It is currently recommended that patients with CLL stages 0 and I follow a watchful waiting strategy. These patients are, therefore, a suitable group for testing immunotherapeutic approaches to avoid problems of immunosuppression as a result of disease progression and chemotherapy. In this study, we investigated the expression of SEMG-1 in early CLL to determine the suitability of SEMG-1 as a target for further development of tumor vaccines for early CLL. METHODS: A combination of reverse transcriptase (RT)-polymerase chain reaction (PCR) and immunocytochemistry was used to evaluate the expression of SEMG-1 in early CLL. The results were correlated with Zap 70 expression. Recombinant SEMG-1 protein was used in an enzyme-linked immunosorbent assay (ELISA) to determine the presence of SEMG-1 antibodies (Ab) in serum from these patients. RESULTS: The SEMG-1 gene was expressed in 19/41 (46%) patients with early CLL. Gene expression was associated with protein synthesis in CLL cells. Protein expression, however, was heterogeneous within individual patients. Only transcripts encoding the SEMG-1(50) variant and not SEMG-1(43) were detected. SEMG-1(50) was expressed irrespective of the Zap 70 status. High-titer SEMG-1 IgG but not IgM Ab were detected in some of these patients, suggesting that SEMG-1-reactive immune responses are intact within the immune repertoire of early CLL patients. CONCLUSIONS: SEMG-1 is expressed in nearly half of patients with early CLL and may be a target for further investigations into its use for immunotherapy of early CLL.
Subject(s)
Antigens, Neoplasm/metabolism , Biomarkers, Tumor/metabolism , Leukemia, Lymphocytic, Chronic, B-Cell/immunology , Seminal Vesicle Secretory Proteins/metabolism , Antibody Formation , Antigens, Neoplasm/genetics , Antigens, Neoplasm/immunology , Biomarkers, Tumor/genetics , Biomarkers, Tumor/immunology , Cancer Vaccines , Enzyme-Linked Immunosorbent Assay , Gene Expression Regulation, Neoplastic , Humans , Immunoglobulin G/blood , Immunoglobulin M/blood , Immunohistochemistry , Leukemia, Lymphocytic, Chronic, B-Cell/blood , Leukemia, Lymphocytic, Chronic, B-Cell/metabolism , Leukemia, Lymphocytic, Chronic, B-Cell/prevention & control , Neoplasm Staging , Reverse Transcriptase Polymerase Chain Reaction , Seminal Vesicle Secretory Proteins/genetics , Seminal Vesicle Secretory Proteins/immunology , ZAP-70 Protein-Tyrosine Kinase/genetics , ZAP-70 Protein-Tyrosine Kinase/immunology , ZAP-70 Protein-Tyrosine Kinase/metabolismABSTRACT
Early chronic lymphocytic leukaemia (CLL) is an ideal disease for immunotherapy. We previously showed that SEMG 1 is a cancer-testis (CT) antigen in CLL. In this study, SEMG 1 was applied as the bait in a yeast two-hybrid system of a testicular cDNA library. Seven clones were isolated and Protamine (Prm) 1 was identified as a novel CT antigen in early CLL. PRM1 transcripts were detected in 11/41 (26.8%) patients. Prm 1 protein was also expressed but heterogeneously within individual patients. Of the 11 patients expressing Prm 1, four expressed Zap 70 protein and seven did not. These results, therefore, indicate that Prm 1 could potentially be a suitable target for the design of tumour vaccine for patients with early CLL, including for those with poor risk CLL. High titres of Prm 1 IgG antibodies could be detected in 20 of these 41 CLL patients but not in any of the 20 healthy donors (P = 0.0001), suggesting the presence of Prm 1-reactive immune responses within the immune repertoire of patients with early CLL. Further work is warranted, especially in approaches to upregulate Prm 1 expression, and to determine the role of Prm 1 as an immunotherapeutic target for early CLL.
