Continuous cell lines consist of cultured cells derived from a specific donor and tissue of origin that have acquired the ability to proliferate indefinitely. These cell lines are well‐recognized models for the study of health and disease, particularly for cancer. However, there are cautions to be aware of when using continuous cell lines, including the possibility of contamination, in which a foreign cell line or microorganism is introduced without the handler's knowledge. Cross‐contamination, in which the contaminant is another cell line, was first recognized in the 1950s but, disturbingly, remains a serious issue today. Many cell lines become cross‐contaminated early, so that subsequent experimental work has been performed only on the contaminant, masquerading under a different name. What can be done in response—how can a researcher know if their own cell lines are cross‐contaminated? Two practical responses are suggested here. First, it is important to check the literature, looking for previous work on cross‐contamination. Some reports may be difficult to find and to make these more accessible, we have compiled a list of known cross‐contaminated cell lines. The list currently contains 360 cell lines, drawn from 68 references. Most contaminants arise within the same species, with HeLa still the most frequently encountered (29%, 106/360) among human cell lines, but interspecies contaminants account for a small but substantial minority of cases (9%, 33/360). Second, even if there are no previous publications on cross‐contamination for that cell line, it is essential to check the sample itself by performing authentication testing.

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Lymphomas are assumed to originate at different stages of lymphocyte development through chromosomal aberrations. Thus, different lymphomas resemble lymphocytes at distinct differentiation stages and show characteristic morphologic, genetic, and transcriptional features. Here, we have performed a microarray-based DNA methylation profiling of 83 mature aggressive B-cell non-Hodgkin lymphomas (maB-NHLs) characterized for their morphologic, genetic, and transcriptional features, including molecular Burkitt lymphomas and diffuse large B-cell lymphomas. Hierarchic clustering indicated that methylation patterns in maB-NHLs were not strictly associated with morphologic, genetic, or transcriptional features. By supervised analyses, we identified 56 genes de novo methylated in all lymphoma subtypes studied and 22 methylated in a lymphoma subtype-specific manner. Remarkably, the group of genes de novo methylated in all lymphoma subtypes was significantly enriched for polycomb targets in embryonic stem cells. De novo methylated genes in all maB-NHLs studied were expressed at low levels in lymphomas and normal hematopoietic tissues but not in nonhematopoietic tissues. These findings, especially the enrichment for polycomb targets in stem cells, indicate that maB-NHLs with different morphologic, genetic, and transcriptional background share a similar stem cell-like epigenetic pattern. This suggests that maB-NHLs originate from cells with stem cell features or that stemness was acquired during lymphomagenesis by epigenetic remodeling. (Blood. 2009; 113:2488-2497 IntroductionAberrant DNA methylation is a hallmark of cancer. Virtually all cancer types are associated with alterations of the methylome. These include global DNA hypomethylation, mostly targeting DNA repeats, and hypermethylation of CpG islands located in the promoter regions of tumor suppressor genes. [1][2][3][4] It is widely accepted that tumor suppressor gene inactivation by DNA hypermethylation allows the tumor clone to obtain a selective (eg, proliferative) advantage. However, recent reports have provided evidence for an instructive mechanism behind aberrant DNA methylation in cancer, which might indicate that specific sequences are predisposed to acquire epigenetic alterations. [5][6][7][8][9] Remarkably, 3 independent reports have recently shown that a highly significant proportion of genes becoming hypermethylated in cancer were already repressed at the embryonic stem cell (ESC) stage by polycomb group (PcG) marks. 7-9 These findings are considered to support the "cancer stem cell theory" in which The online version of this article contains a data supplement.The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked ''advertisement'' in accordance with 18 USC section 1734. For personal use only. on May 13, 2018. by guest www.bloodjournal.org From aberrant epigenetic changes of PcG target genes occurring in a cell with stem cell features might represent the ...

without detectable blast infiltration. At diagnosis of MDS, interface cytogenetic and RT-PCR analyses, respectively, showed trisomy 8 and absence of AF9-MLL rearrangement in Introduction the bone marrow (BM). On readmission with florid leukemia, his peripheral white blood cell count was 13 200/mm 3 , with A subtle, reciprocal translocation exchanging the terminal 56% leukemic blasts. His hemoglobin concentration was short and long arm segments of chromosomes 9 and 11, 15.0 g/dl, and his platelet count was 22 000/mm 3 . The bone respectively t(9;11)(p21-22;q23), is associated with acute marrow aspiration showed 92% leukemic blasts, and the mormyeloid leukemia (AML)-M5, 1 particularly the M5a subtype. 2 phological diagnosis was made as AML-M5a. Cytogenetic Ascertainment may be difficult in suboptimal preparations analysis was interpreted as: 47, XY, +8, t(9;11)(p22;q23). and, despite being regarded as the 'standard' cytogenetic Immunophenotyping analysis of fresh leukemia blasts change in acute monoblastic leukemia, its overall incidence revealed no significant expression of CD antigens associated and pattern of associations remain uncertain. 2 A recent study with the myelo-monocytic lineage. CD34 was 30% positive comparing AML-M1 and -M5 patients, analyzed simuland non-lineage-associated HLA-DR was found to be positive taneously by reverse transcriptase-polymerase chain reaction at 70%; whereas those indicative of lymphoid lineage includ-(RT-PCR), Southern blotting and fluorescence in situ hybridizing CD3, CD4, CD8, CD10, CD19 were absent or weakly ation (FISH) with an MLL-specific yeast artificial chromosome expressed. Myeloperoxidase activity was weakly detected on (YAC) probe, suggests the overall incidence of MLL rearrangethe fresh leukemic blasts. Despite receiving chemotherapy, he ment in AML-M5 may be as high as 60%. 3 It was apparent in succumbed to rapidly progressive leukemia on 15 August that study that approximately half the cases with MLL 1995. rearrangement went undetected by cytogenetic methods, including a cryptic t(6;11)(q27;q23) resulting from a cytogenetically invisible insertion juxtaposing AF6 and MLL.Materials and methods A case of AML-M5a with de novo MLL-AF9 fusion evolving from MDS with trisomy 8 present at all phases has recently Cell culture been described. 4 We describe a pair of cell lines, MOLM-13 During relapse, after chemotherapy, a heparinized peripheral blood specimen, obtained with informed consent, was proCorrespondence: Y Matsuo,

Exosomes (EVs) have relevance in cell-to-cell communication carrying pro-tumorigenic factors that participate in oncogenesis and drug resistance and are proposed to have potential as self-delivery systems. Advancing on our studies of EVs in triple-negative breast cancer, here we more comprehensively analysed isogenic cell line variants and their EV populations, tissues cell line variants and their EV populations, as well as breast tumour and normal tissues. Profiling 384 miRNAs showed EV miRNA content to be highly representative of their cells of origin. miRNAs most substantially down-regulated in aggressive cells and their EVs originated from 14q32. Analysis of miR-134, the most substantially down-regulated miRNA, supported its clinical relevance in breast tumours compared to matched normal breast tissue. Functional studies indicated that miR-134 controls STAT5B which, in turn, controls Hsp90. miR-134 delivered by direct transfection into Hs578Ts(i)8 cells (in which it was greatly down-regulated) reduced STAT5B, Hsp90, and Bcl-2 levels, reduced cellular proliferation, and enhanced cisplatin-induced apoptosis. Delivery via miR-134-enriched EVs also reduced STAT5B and Hsp90, reduced cellular migration and invasion, and enhanced sensitivity to anti-Hsp90 drugs. While the differing effects achieved by transfection or EV delivery are likely to be, at least partly, due to specific amounts of miR-134 delivered by these routes, these EV-based studies identified miRNA-134 as a potential biomarker and therapeutic for breast cancer.