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Abnormalities of the MYC oncogene on chromosome 8 are characteristic of Burkitt lymphoma and other aggressive B-cell lymphomas, including diffuse large B-cell lymphoma (DLBCL). We recently described a colorimetric in situ hybridization (CISH) method for detecting extra copies of the MYC gene in DLBCL and the frequent occurrence of excess copies of discrete MYC signals in the context of diploidy or polyploidy of chromosome 8, which correlated with increased mRNA signals. We further observed enlarged MYC signals, which were counted as a single gene copy but, by their dimension and unusual shape, likely consisted of “clusters” of MYC genes. In this study, we sought to further characterize these clusters of MYC signals by determining whether the presence of these correlated with other genetic features, mRNA levels, protein, and overall survival. We found that MYC clusters correlated with an abnormal MYC locus and with increased mRNA. MYC mRNA correlated with protein levels, and both increased mRNA and protein correlated with poorer overall survival. MYC clusters were seen in both the germinal center and activated B-cell subtypes of DLBCL. Clusters of MYC signals may be an underappreciated, but clinically important, feature of aggressive B-cell lymphomas with potential prognostic and therapeutic relevance.

Background Cell spheroids and aggregates generated from three-dimensional (3D) cell culture methods are similar to in vivo tumors in terms of tissue morphology, biology, and gene expression, unlike cells grown in 2D cell cultures. Breast cancer heterogeneity is one of the main drug resistant mechanisms and needs to be overcome in order to increase the efficacy of drug activity in its treatments. Methods We performed a unique 3D cell culture and drug efficacy study with trastuzumab emtansine (Kadcyla®, T-DM1) across five breast cancer cell lines (BT-474, SK-BR-3, MDA-MB-361, MDA-MB-175, and MCF-7) that were previously investigated in 2D cell culture. We performed HER2 IHC staining, cell viability experiments, Gene-protein-assay (GPA), and T-DM1 internalization studies. Results We obtained significantly different results including higher IC50 for some of the cell lines. Our GPA showed some significant heterogeneous HER2 gene and protein expression in 3D cultured spheroids or aggregates. The fluorescent images also showed that a longer incubation time is needed for T-DM1 to be internalized effectively into 3D cultured spheroids or aggregates. Conclusion Our study demonstrated that the difference of T-DM1 drug activity in 3D spheroids or aggregates might be due to tumor heterogeneity and less efficient internalization of T-DM1 that is not seen using 2D cell culture models. Drug studies using 3D cell culture are expected to provide biologically relevant models for determining drug activity in tumor tissue in future drug response and resistance research.

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Introduction: Cell spheroids/aggregates generated from three dimensional (3D) cell culture methods are similar to real tumors in terms of tissue morphology, biology, and gene expression. We performed a unique 3D cell culture drug efficacy study with Trastuzumab emtansine (T-DM1) across a number of breast cancer cell lines that were previously investigated in 2D cell culture (Lewis Phillips, et al, 2008). We obtained significantly different results for some cell lines grown as 3D spheroids/aggregates when compared to those grown as 2D cultures. Methodology: We performed 3D cell culture and produced FFPE blocks (using novel methods) from 3D spheroids/aggregates to determine HER2 (IHC) protein expression levels for five cell lines: SK-BR-3; BT-474; MDA-MB-361; MDA-MB-175 and MCF-7. We also performed HER2 gene-protein assay (HER2 GPA) to determine HER2 gene amplification along with IHC protein expression status in four cell lines: SK-BR-3; BT-474; MDA-MB-361 and MDA-MB-175. Drug (T-DM1) activity testing using CellTiterTM-Glo 3D cell viability assay was performed on 3D cell spheroids/aggregates for comparison with 2D cells. Images were obtained of T-DM1 internalization in BT-474 cells and spheroids using pHrodo™ iFL Human IgG Labeling Reagent. Results: In 3D spheroids/aggregates, HER2 IHC staining and GPA assay showed for SK-BR-3 and BT-474 HER2 3+ expression and HER2/CEP17 of ≥ 2; MDA-MB-361 cells with HER2 2+ expression and HER2/CEP17 of ≥ 2.0; MDA-MB-175 cells with HER2 1+ expression and HER2/CEP17 < 2.0 and MCF-7 cells with HER2 0+(IHC staining only without HER2 GPA data). Some of the 3D spheroids/aggregates in MDA-MB-361 cells showed heterogeneous expression of HER2 protein. The IC50 values of 3D spheroids/aggregates for some cell lines were significantly higher than were demonstrated for cell lines grown in 2D cell cultures. The fold changes between 3D spheroids and 2D cells (72h T-DM1 treatment time) are: 4.2 for SK-BR-3; ≳ 10 for BT-474 and 22 for MDA-MB-361. Additionally, the fluorescent images showed that a longer incubation time was required for the T-DM1 drug (3 µg/ml) to be internalized effectively into BT-474 3D spheroids; for example, about 120h for 3D spheroids in comparison to about 36h in 2D cells. Interestingly, the 3D spheroids incubated for 120h with T-DM1 (470 µm) are smaller in size than 3D spheroids in the control group (600 µm) incubated for 120h without T-DM1 treatment. Conclusions: Drug efficacy studies performed on 3D cultured spheroids/aggregates are expected to be very important and biologically relevant for determining drug activity in tumor tissue. Our drug efficacy study using 3D cell culture demonstrated greater concentrations of T-DM1 and longer incubation times were required than for cells grown as 2D in some cell lines, likely due to less efficient internalization. Citation Format: Jean Z. Boyer, Gail Lewis Phillips, Hiro Nitta, Karl Garsha, Eric May, Brittany Admire, Robert Kraft, Megan Peccarelli, Andre Zamorano, Scott Gill, Eslie Dennis, Liz Vela, Penny Towne. Activity of trastuzumab emtansine (T-DM1) in 3D cell culture [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 29.