CYCLIN D1 PROTEIN EXPRESSION IN MANTLE CELL LYMPHOMA

Background: The t(11;14)(q13;q32) is a chromosomal abnormality usually associated with mantle cell (centrocytic) lymphomas, although it has occasionally been reported in other chronic lymphoproliferative disord ers such as chronic lymphocytic leukemia, prolymphocytic leukemia, spl enic lymphoma with villous lymphocytes, and multiple myeloma. This abn ormality results in the translocation of the bcl-1 oncogene from chrom osome 11 to the immunoglobulin heavy chain locus on chromosome 14. The bcl-1 oncogene is a member of the cyclin gene family, and high levels of cyclin D1 mRNA are consistently found in malignant B cell prolifer ations with t(11;14). Patients and methods: We examined cyclin D1 prot ein expression in 33 patients with low grade lymphoproliferative disor ders and 2 patients with reactive hyperplasias by Western blot analysi s using a polyclonal antibody. Results: 8/11 mantle cell lymphomas, 0/ 11 chronic lymphocytic leukemias, 0/4 hairy cell leukemias, 0/2 Sezary syndrome, 0/2 monocytoid B-cell lymphomas, 0/3 follicular lymphomas, and 0/2 reactive hyperplasias had overexpression of cyclin D1. Cytogen etic analysis was performed in four cases of mantle cell lymphoma; thr ee of these cases had the t(11;14), one of which was hypotetraploid wi th two copies of t(11;14). Immunophenotypically, all cases of mantle c ell lymphoma and chronic lymphocytic leukemia had coexpression of CD5 and CD20. Conclusion: Mantle cell lymphoma may be difficult to discrim inate from chronic lymphocytic leukemia, a more indolent disease, on m orphologic and immunophenotypic grounds. Our findings suggest that ana lysis of cyclin D1 protein expression may be helpful in differentiatin g mantle cell lymphomas from other low grade lymphoproliferative disor ders.