The Hematopathology Section analyzes approximately 200 cases per month, integrates immunohistochemical and molecular diagnostic assays, and evaluates assays under translational testing for possible diagnostic or prognostic utility. Accessioned cases serve as source materials for research and training.

The Immunohistochemistry Laboratory provides immunohistochemical support for all diagnostic pathology services in LP using state-of-the-art automated equipment and serves as a resource for intra- and interdepartmental collaborative research. The service maintains a stock of approximately 120 antibodies for diagnostic studies and processed over 2,600 requests in 1996, staining over 23,000 slides. The immunohistochemistry laboratory seeks out and tests new antibodies for diagnostic or prognostic impact. Current examples of antibodies under investigation include anti-Bax, Mcl-1, perforin, TIA-1, BCL-6, PAX-5, p80, ALK, and Rb.

The Molecular Diagnostics Laboratory performs tests to support the clinical and research activities of LP. Tests involve DNA-PCR, RT-PCR, DGGE, Southern blotting, and in situ hybridization. Clonal analysis for immunoglobulin and TCR rearrangement accounts for over 50 percent of requested tests. Additional tests include analyses of Bcl-1, Bcl-2, NPM/ALK fusion transcripts, HHV8, EBV, and p53. The laboratory also performs EBV in situ hybridization.

Research: Lymphomas account for about 10 percent of human neoplasms. They have a wide range of behavior even within the same histologic subtype. The laboratory's research is directed toward understanding the molecular mechanisms underlying the pathogenesis and progression of lymphomas, and in using this information to develop rational methods for classification and prognostication.

Studies of the molecular abnormalities found in lymphomas have served as prototypes for understanding many of the mechanisms involved in neoplasia and provide lymphoma biologists and pathologists with a rational means of classifying these neoplasms. Our laboratory has focused on several subtypes of non-Hodgkin's lymphomas to identify and evaluate the significance of the presence of various oncogenes and tumor suppressor genes. The laboratory demonstrated that Bcl-1 rearrangement, which results in overexpression of cyclin D1, is the characteristic genetic lesion in mantle cell lymphomas (MCL) and is a useful marker for their identification. We also showed that multiple lymphomatous polyposis, a disease characterized by multiple gastrointestinal polyps, is genetically identical to MCL and represents primary gastrointestinal involvement by MCL. Additional genetic abnormalities accumulate in MCL, and a subset of cases shows either p53 mutations or p16 absence. These cases have a poor prognosis and correlate with the pathologic subgroup "blastic" MCL.

The laboratory has also focused on a common group of large cell lymphomas called anaplastic large cell lymphomas (ALCL) that primarily affects children and young adults. ALCL is characterized by the t(2;5) which results in inappropriate expression of anaplastic lymphoma kinase (ALK) through its fusion with nucleophosmin (NPM). We have shown that NPM/ALK fusion transcripts are specific to ALCL, and do not occur in other lymphomas, including Hodgkin's disease (HD). We also showed that the immuno-histochemical profile of ALCL is different from HD, in that ALCL expresses the cytotoxic granule-associated proteins TIA-1, perforin, and granzyme B. Because some cases of ALCL may simulate HD, these molecular and immunohistochemical markers are useful in distinguishing the two diseases. These types of studies provide an objective basis for using molecular tests diagnostically.

The laboratory also investigates the molecular biology of follicular lymphoma (FL) progression as a general model for cancer progression. The laboratory has shown that p53 mutations occur frequently in progressed FL, and have predictive value when detected in indolent FL. In collaboration with the Medicine Branch of NCI, we have shown that p53 mutations in high-grade lymphomas also predict poor response to chemotherapy. We are studying the role of CDK inhibitors in lymphoma progression and have detected LOH at chromosome 9p13, the locus of p16. Progression is also being investigated by a combination of other techniques, including CGH, LOH, and subtractive library approaches.

The laboratory identified clustered mutations in the coding regions of cMyc in Burkitt's lymphomas. Mutations surrounding a region including Thr 58 and Ser 62 enhance the ability of myc to transform Rat1A cells and deregulate transcriptional activating activity. This is due to the loss in the ability of cyclinA/CDK/p107 complexes to phosphorylate myc at the above sites. We are continuing to investigate the effect of mutations in other regions of cMyc. These studies are providing new information regarding the mechanism of action and control of this critical protein.

Finally, as part of NCI's CGAP initiative, the laboratory is providing tissues for library development which should generate information regarding the genetic pathways involved in different lymphomas as well as in lymphoma progression.

Recent Publications
Wilson, WH, et al. Blood 1997; 89:601-9.
Krenacs, L, et al. Blood 1997; 86:2321-7.
Hernandez, J, et al. Blood 1996; 87:3351-9.
Hoang, AT, et al. Mol Cell Biol 1995; 15:4031-42.

Collaborators
Elaine Jaffe, M.D.; Wyndham Wilson, M.D.; Lance Liotta, M.D., Ph.D.; Michael Emmert-Buck, M.D., Ph.D.; and David Krizman, Ph.D., NIH
Chi V. Dang, M.D., Ph.D., Johns Hopkins University School of Medicine