Subclones in B-lymphoma cell lines: isogenic models for the study of gene regulation.

Genetic heterogeneity though common in tumors has been rarely documented in cell lines. To examine how often B-lymphoma cell lines are comprised of subclones, we performed immunoglobulin (IG) heavy chain hypermutation analysis. Revealing that subclones are not rare in B-cell lymphoma cell lines, 6/49 IG hypermutated cell lines (12%) consisted of subclones with individual IG mutations.

BCL6--regulated by AhR/ARNT and wild-type MEF2B--drives expression of germinal center markers MYBL1 and LMO2.

Genetic heterogeneity is widespread in tumors, but poorly documented in cell lines. According to immunoglobulin hypermutation analysis, the diffuse large B-cell lymphoma cell line U-2932 comprises two subpopulations faithfully representing original tumor subclones. We set out to identify molecular causes underlying subclone-specific expression affecting 221 genes including surface markers and the germinal center oncogenes BCL6 and MYC.

Inhibition of PI3K/mTOR overcomes nilotinib resistance in BCR-ABL1 positive leukemia cells through translational down-regulation of MDM2.

Chronic myeloid leukemia (CML) is a cytogenetic disorder resulting from formation of the Philadelphia chromosome (Ph), that is, the t(9;22) chromosomal translocation and the formation of the BCR-ABL1 fusion protein. Tyrosine kinase inhibitors (TKI), such as imatinib and nilotinib, have emerged as leading compounds with which to treat CML. t(9;22) is not restricted to CML, 20-30% of acute lymphoblastic leukemia (ALL) cases also carry the Ph.

DNA methylation regulates expression of VEGF-R2 (KDR) and VEGF-R3 (FLT4).

Background: Vascular Endothelial Growth Factors (VEGFs) and their receptors (VEGF-Rs) are important regulators for angiogenesis and lymphangiogenesis. VEGFs and VEGF-Rs are not only expressed on endothelial cells but also on various subtypes of solid tumors and leukemias contributing to the growth of the malignant cells. This study was performed to examine whether VEGF-R2 (KDR) and VEGF-R3 (FLT4) are regulated by DNA methylation.

BCR-ABL1-independent PI3Kinase activation causing imatinib-resistance.

Background: The BCR-ABL1 translocation occurs in chronic myeloid leukemia (CML) and in 25% of cases with acute lymphoblastic leukemia (ALL). The advent of tyrosine kinase inhibitors (TKI) has fundamentally changed the treatment of CML. However, TKI are not equally effective for treating ALL.

Epigenetic regulation of CD44 in Hodgkin and non-Hodgkin lymphoma.

Background: Epigenetic inactivation of tumor suppressor genes (TSG) by promoter CpG island hypermethylation is a hallmark of cancer. To assay its extent in human lymphoma, methylation of 24 TSG was analyzed in lymphoma-derived cell lines as well as in patient samples.

Methods: We screened for TSG methylation using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) in 40 lymphoma-derived cell lines representing anaplastic large cell lymphoma, Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), Hodgkin lymphoma and mantle cell lymphoma (MCL) as well as in 50 primary lymphoma samples.

CD7 in acute myeloid leukemia: correlation with loss of wild-type CEBPA, consequence of epigenetic regulation.

Background: CD7 is a negative prognostic marker in myeloid malignancies. In acute myeloid leukemia (AML), an inverse correlation exists between expression of wild-type CEBPA and CD7. Aim of this study was to find out whether C/EBPalpha is a negative regulator of CD7 and which other regulatory mechanisms might be involved.

SET-NUP214 fusion in acute myeloid leukemia- and T-cell acute lymphoblastic leukemia-derived cell lines.

Background: SET-NUP214 fusion resulting from a recurrent cryptic deletion, del(9)(q34.11q34.13) has recently been described in T-cell acute lymphoblastic leukemia (T-ALL) and in one case of acute myeloid leukemia (AML).