Expression of bcl-2 oncogene product in primary non-Hodgkin's malignant lymphoma of the oral cavity

Lymphomas of the oral cavity: histology, immunologic type, and incidence of Epstein-Barr virus infection

The purpose of this study was to determine the histologic class and immunologic phenotype of lymphomas presenting initially in the oral cavity and whether this correlated to a high incidence of Epstein-Barr virus (EBV) infection as has been reported with lymphomas in the nasal cavity. Seventy-one cases of oral lymphomas from the oral pathology referral service were analyzed retrospectively. They were classified according to the Revised European American Lymphoma (REAL) classification system using routine immunohistochemistry. EBV infection was determined by detection of early viral RNA sequences (EBER) and latent membrane protein (LMP-1) expression. Only non-Hodgkin's lymphomas were observed, with a female predominance of 2:1. They were primarily of B-cell origin and histologically classified mainly as large B-cell type (68%); T-cell lymphomas were rare (8%). EBV infection was observed in 14% of the B-cell lymphomas, an incidence rate higher than that reported in studies of B-cell lymphomas not located in the oral cavity but not as high as that observed in pleomorphic T-cell lymphomas (all sites, 36%) or nasal cavity T-cell lymphomas (nearly 100%). Interestingly, EBV proliferation did not correlate with expression of either Bcl-2 or p53.

Apoptosis-associated proteins in oral lymphomas from HIV-positive patients

Extranodal oral lymphomas, seen with increasing frequency in HIV infection, may have dysfunctional apoptotic mechanisms that favor tumor progression. The purpose of this study was to evaluate extranodal lymphomas from HIV-positive patients for expression of apoptosis-associated proteins. Correlations were made with 10 histologically comparable extranodal lymphomas from HIV-negative patients and 6 hyperplastic lymph nodes from otherwise healthy young adults. Formalin-fixed tissue sections were immunohistochemically stained for apoptosis-associated proteins (Bcl-2, Bcl-x, Bax, Bak, p53, MDM2, BHRF). In situ hybridization was also done on deparaffinized sections for Epstein-Barr virus EBER mRNA. Eighteen consecutive oral lymphomas were studied in HIV/AIDS-positive patients. Four of 5 intermediate-grade lymphomas expressed Bcl-2 to a greater degree than did high-grade lymphomas (4 of 13). Most lymphomas were positive for Bcl-x and Bax, and few expressed Bak. The staining patterns for these proteins were similar to those seen in HIV-negative patients. Staining patterns were relatively consistent in the hyperplastic lymph nodes, whereas such patterns were irregular in lymphomas. Positive p53 staining was seen in 11 of 18 HIV-positive cases; 9 of these were also MDM2-positive. Double stains suggested that both p53 and MDM2 proteins were expressed in the same cells in these nine cases. Epstein-Barr virus-EBER mRNA was detected in 14 of 18 cases and in 3 of 10 cases from HIV-negative patients. BHRF staining was evident in only a few cells of three HIV-positive lymphomas. The irregular expression of Bcl-2, Bcl-x, Bax, and Bak in oral lymphomas indicates dysfunctional apoptotic mechanisms in these tumors. Bcl-2 staining differs with tumor grade. Positive staining for p53 and MDM2 proteins is a notable feature of lymphomas in HIV-positive patients and may relate to binding of MDM2 to wild-type p53. Epstein-Barr virus is more commonly associated with oral lymphomas in HIV-positive patients, although the Epstein-Barr virus-produced protein BHRF, which has Bcl-2-like activity, is minimally expressed.

Detection of the apoptosis-suppressing oncoprotein bcl-2 in salivary gland lymphoma

The bcl-2 proto-oncogene encodes an inner mitochondrial membrane protein that blocks apoptosis and programmed cell death in human lymphoid tissue. In this study a monospecific anti-human bcl-2 antibody that is reactive in formalin-fixed tissues was used with an avidin-biotin complex immunoperoxidase method to evaluate 41 cases of lymphoproliferative disorders of the salivary gland. The study cases were 26 primary salivary gland lymphomas (including 21 B-cell lymphomas four T-cell lymphomas and one true histiocytic lymphoma) and 15 cases of myoepithelial sialadenitis. Bcl-2 expression is restricted to the mantle zone and interfollicular lymphocytes around reactive germinal centers of myoepithelial sialadenitis. Seventeen of the 21 B-cell lymphomas were positive for bcl-2, and were composed of mucosa-associated lymphoid tissue (MALT), centrocytic, centroblastic-centrocytic and centroblastic lymphomas. Noticeably, all 11 cases of MALT lymphoma were bcl-2 positive. In contrast, staining for bcl-2 was present in only one of four cases of T-cell lymphomas and was negative in one true histiocytic lymphoma. The expression of bcl-2 protein was also investigated in the ductal systems and epimyoepithelial islands of salivary glands from patients with malignant lymphoma and myoepithelial sialadenitis. While salivary ducts in eight of 15 cases of myoepithelial sialadenitis immunostained for bcl-2, epimyoepithelial islands showed bcl-2 expression in only five cases of myoepithelial sialadenitis. We found that ductal cells in the salivary gland from patients with primary non-Hodgkin's lymphomas expressed bcl-2 protein. It was of interest that epimyoepithelial islands in all cases of MALT lymphoma displayed bcl-2 expression whereas other subtypes of B-cell lymphoma, T-cell lymphoma and true histiocytic lymphoma were invariably negative. These results indicate that bcl-2 is expressed in a wide variety of non-Hodgkin's lymphomas, especially when all 11 cases of MALT lymphoma are bcl-2 positive. Epimyoepithelial islands in MALT lymphoma express this oncoprotein, and their ability to induce bcl-2 synthesis resulted in the prevention of apoptosis and prolonged cell survival. Furthermore, the expression of bcl-2 protein in the lymphoma cells may be responsible for the induction of bcl-2 expression in the adjacent epimyoepithelial islands through a lymphocyte chemical mediator.