Hodgkin’s Lymphoma Cell Lines Have up-Regulated IL-3 Receptor α (IL-3Rα) Expression and Are Sensitive to SL-401, An IL-3Rα Targeted Drug

• Published in: Blood 2011-11, Vol.118 (21), p.3737-3737
• Main Authors: Diefenbach, Catherine S., Sabado, Rachel, Brooks, Christopher L., Baquero-Buitrago, Jairo, Cruz, Crystal, Vengco, Isabelita, Montanari, Francesca, Marchi, Enrica, Scotto, Luigi, Cirrito, Thomas P., Bergstein, Ivan, O'Connor, Owen A.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V118.21.3737.3737

Abstract 3737 Hodgkin lymphoma (HL) is among the most curable lymphomas, however 20%-30% of patients relapse after initial chemotherapy, or have primary refractory disease. While 30–50% of these patients may be cured with second line chemotherapy and autologous stem cell transplant, patients who do not obtain a complete response (CR) prior to transplantation, or who relapse after second line therapy have few effective therapeutic options. Novel treatment strategies for these patients are needed. It has been previously shown that in patients with classical HL the malignant Hodgkin Reed-Sternberg cells (HRS) express a high level of the Interleukin-3 receptor (IL-3R). Therefore, we hypothesized that SL-401, a novel biologic conjugate consisting of IL-3 linked to diphtheria toxin, which targets IL-3R, may be an effective approach for selectively targeting and killing HRS cells. Methods: We first assessed the expression of the IL-3R α-chain (CD123) on two nodular sclerosing (HDLM-2 and L-428) and two mixed cellularity (KM:H2 and L-1236) HL cell lines by flow cytometry. Cells were washed with PBS and stained with CD123 PE (BD Pharmingen) as well as other antibodies, including CD15 FITC (BD Pharmingen), for 20 minutes at 4°C and again washed with PBS. Stained cells were acquired using the LSR II (BD) and data were analyzed using Flow Jo (Tree Star). We then tested the sensitivity of these cell lines to SL-401 using a CellTiter Glo in vitro cytotoxicity assay. A CD123 positive eyrthroleukemic cell line (TF-1/H-ras) with known sensitivity to SL-401 was used as a positive control. The cell lines were cultured in the presence or absence of SL-401 for 48 h and assessed for cell viability at concentrations ranging from 3×10−7 to 1.3 μg/ml. Results: We found high expression of CD123 on HDLM-2 and L-428 HL lines (99% and 89%, respectively) and low-to-moderate expression of the receptor on the L1236 and KM-H2 lines (19.5% and 1%, respectively). Based on CD123 expression, we assessed the sensitivity of these cell lines to SL-401. The L428 and HDLM2 cell lines, which exhibited a high expression of CD123, showed sensitivity to SL-401 relative to control starting at approximately 0.3 ng/ml. Cell viability was reduced to 64.8 ± 5% for L-428 and 68.2 ± 8% for HDLM2 when incubated at the highest concentration of drug (1 μg/ml (L428) and 0.7 μg/ml (HDLM2)). The low CD123 expressing cell lines L1236 and KM:H2 were less sensitive to SL-401 and did not exhibit a significant reductio