EXPRESSION OF ONCOGENIC MOLECULES IN PRIMARY CENTRAL-NERVOUS-SYSTEM LYMPHOMAS IN IMMUNOCOMPETENT PATIENTS

We studied overexpression of p53, Bcl-2, Bcl-6, c-Myc and Mdm2 protein s by immunohistochemistry for a total of 27 primary central nervous sy stem B cell lymphomas (CNS lymphomas) in immunocompetent patients and one CNS lymphoma in an AIDS patient. The expression of Epstein-Barr (E B) virus-encoded small RNA-1 (EBER-1) was also analysed using in situ hybridisation. Overexpression (more than 20% of cells stained) of p53 protein was detected in 8 of 27 immunocompetent cases (30%); 6 cases s howed a nuclear stain and 2 cases showed cytoplasmic stain (nuclear ex clusion). Strong Bcl-2 or Bcl-6 immunoreactivity suggestive of overexp ression was seen, respectively, in 5 (19%) and 6 (22%) cases; 2 cases were positive for both immunoreactivities. Interestingly, overexpressi on of Bcl-2 or Bcl-6 was not seen in the cases which showed p53 overex pression (P < 0.03; chi-square test). EBER-1 expression was not detect ed in any of the 27 immunocompetent cases, but was found in the AIDS-r elated CNS lymphoma, which also showed an overexpression of Bcl-6, but not Bcl-2. None of the cases showed c-Myc or Mdm2 overexpression. Tak en together, it is suggested that CNS lymphoma in immunocompetent host s is a distinct disease that has a different molecular profile from th ose of systemic lymphoma and/or AIDS-related CNS lymphoma.