The potent oncogene NPM-ALK mediates malignant transformation of normal human CD4(+) T lymphocytes.

With this study we have demonstrated that in vitro transduction of normal human CD4(+) T lymphocytes with NPM-ALK results in their malignant transformation. The transformed cells become immortalized and display morphology and immunophenotype characteristic of patient-derived anaplastic large-cell lymphomas. These unique features, which are strictly dependent on NPM-ALK activity and expression, include perpetual cell growth, proliferation, and survival; activation of the key signal transduction pathways STAT3 and mTORC1; and expression of CD30 (the hallmark of anaplastic large-cell lymphoma) and of immunosuppressive cytokine IL-10 and cell-surface protein PD-L1/CD274. Implantation of NPM-ALK-transformed CD4(+) T lymphocytes into immunodeficient mice resulted in formation of tumors indistinguishable from patients' anaplastic large-cell lymphomas. Our findings demonstrate that the key aspects of human carcinogenesis closely recapitulating the features of the native tumors can be faithfully reproduced in vitro when an appropriate oncogene is used to transform its natural target cells; this in turn points to the fundamental role in malignant cell transformation of potent oncogenes expressed in the relevant target cells. Such transformed cells should permit study of the early stages of carcinogenesis, and in particular the initial oncogene-host cell interactions. This experimental design could also be useful for studies of the effects of early therapeutic intervention and likely also the mechanisms of malignant progression.

Dynamic Changes in Gene Mutational Landscape With Preservation of Core Mutations in Mantle Cell Lymphoma Cells.

While studies have identified a number of mutations in mantle cell lymphoma (MCL), the list may still be incomplete and contribution to the pathogenesis remains unclear. We analyzed the mutational landscape of four mantle cell lymphoma biopsies obtained during an 8-year period from the same patient with his normal cells serving as control; we also established a cell line from the final stage of the disease. Numerous mutations with high allelic burden have been identified in all four biopsies. While a large subset of mutations was seen only in individual biopsies, the core of 21 mutations persisted throughout the disease. This mutational core is also maintained in the cell line that also displays DNA-methylation and cytokine secretion profiles of the primary mantle cell lymphoma cells. This cell line is uniquely sensitive to clinically relevant inhibitors of Bruton's Tyrosine Kinase. The response to Bruton Tyrosine Kinase's inhibition is enhanced by inhibitors of CDK4/6 and mTOR. Among the mutations seen in the primary and cultured MCL cells, mutations of three genes are involved in the control of H3K4 methylation: demethylase KDM5C, present already in the early disease, and methyltransferase KMT2D and cofactor BCOR, both of which are seen late in the disease and are novel and predicted to be pathogenic. The presence of these mutations was associated with hypermethylation of H3K4. Restoration of KDM5C expression affected expression of numerous genes involved in cell proliferation, adherence/movement, and invasiveness.

Multifocal mantle cell lymphoma in situ in the setting of a composite lymphoma.

OBJECTIVES: Mantle cell lymphoma in situ (MCLIS) consists of immunophenotypically defined but histologically inapparent neoplastic cells restricted to narrow mantle zones, without expansion or invasion beyond the mantle zone. We report a unique case of MCLIS associated with a much more manifest nodal marginal zone lymphoma (MZL) in an inguinal lymph node, porta hepatis lymph node, and bone marrow. METHODS: Biopsies from all three locations were evaluated using standard H&E-stained sections, immunohistochemistry, flow cytometry, metaphase cytogenetics, and/or fluorescence in situ hybridization (FISH). RESULTS: This case is unique for three reasons. First, the histologically covert mantle cell lymphoma was multifocal, detected in all three locations using one or more of flow cytometry, immunohistochemistry, cytogenetics, and FISH. Second, the MCLIS was always accompanied by a more histologically dominant MZL. Third, where evaluable, it did not grow in an appreciable mantle zone distribution, presumably due to destruction of the normal nodal architecture by the neoplastic MZL cells and the resulting absence of recognizable follicles and mantle zones. CONCLUSIONS: This unique case provides new insight into the pathogenesis of MCLIS.