Abstract 3702: Establishment and characterization of a novel MYC/BCL2 double-hit high-grade B-cell lymphoma cell line HLA-3

The majority of MYC/BCL2 double hit lymphoma (DHL) morphologically resembles diffuse large B-cell lymphoma (DLBCL) or unclassified B-cell lymphoma, with intermediate features of DLBCL and Burkitt’s lymphoma. DHL also typically results in shorter survival time than other lymphomas. To further understand DHL’s biology and identify potential effective agents against DHL, we established a unique MYC/BCL2 high-grade B-cell lymphoma cell line with morphological DLBCL features. The HLA-3 DHL cell line was derived from a MYC/BCL2 high-grade B-cell lymphoma patient-derived xenograft (PDX) model. We performed flow cytometry immunophenotypic analysis and established the HLA-3 cell line after 7 months of continuous culture. We utilized molecular and cellular techniques, including flow cytometry and polymerase chain reaction (PCR) analysis, to characterize the HLA-3 cell line. We performed reverse phase protein array (RPPA) analysis to determine its protein signaling profile. To identify agents with anti-DHL activity, we screened the effects of a panel of agents alone and in combination with ibrutinib on the cell viability of this newly established cell line. The HLA-3 cell line was optimally maintained at a density between 1 and 2 × 10 6 cells/mL and successfully proliferated in a single-cell suspension without cellular clump formation. The HLA-3 cells were EBV-negative and possessed a germinal center B cell immunophenotype. Moreover, the immunophenotypes of the primary patient tumor cells and HLA-3 cells were virtually identical. The HLA-3 cells were positive for CD19, CD45, CD35, CD10 and HLA-ABC, negative for CD3, CD5, CD40, CD34 and TdT, and were dim for CD22, CD56, CD8, CD4 and CD23. Representative flow cytometry histograms showed 99% of the HLA-3 cells were positive for CD19 and CD45, with no detectable surface kappa and lambda light chains. The HLA-3 cells expressed a high level of CD38, an indicator of MYC rearrangement. Similar to the original lymphoma cells, the HLA-3 cells showed dim/low CD20 expression. Based on RPPA data, we constructed a diagram showing activation of the ATM/Chk2 DNA repair and the IGF1R/PI3K/mTOR signaling pathways in the HLA-3 cells. In support of this upregulated activity, we found that 5/7 tested commercial PI3K/mTOR inhibitors significantly reduced the viability of the HLA-3 cells in a dose-dependent manner, with AZD8055 the most sensitive of the tested inhibitors against the cell line. Further, DNA repair pathway inhibitors BMN673 and RG7112 were effective against the HLA-3 cell line. The newly characterized high-grade B-cell lymphoma cell line will provide useful in vitro and in vivo models for biological studies related to human DHL, which is refractory to current therapies and urgently needs novel therapeutic approaches. This work suggests the PI3K/mTOR and DNA repair pathways may be therapeutic targets for MYC/BCL2 double-hit high-grade B-cell lymphoma. Citation Format: Hui Guo, Hui Zhang, Krystle Nomie, Liang Zhang, Kelley P. Murfin, Michael Wang. Establishment and characterization of a novel MYC/BCL2 double-hit high-grade B-cell lymphoma cell line HLA-3 [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 3702.