In vivo and in vitro sensitivity of blastic plasmacytoid dendritic cell neoplasm to SL-401, an interleukin-3 receptor targeted biologic agent

Abstract

ABSTRACTlabile group of amino acids to a diphtheria toxin (DT) payload that has been truncated at its receptor binding region. 20 Since IL-3, the natural ligand for IL-3R, binds with very high specificity and avidity, 21 SL-401 is able to transport DT efficiently and preferentially to cells that overexpress IL-3R, leading to internalization followed by receptor-mediated endocytosis and localization of SL-401 to early endosomes. After cleavage of the SL-401 DT constituent in the acidic medium of endosomes, DT translocates into the cytosol and binds to ADP-ribosylated elongation factor 2, leading to blockade of protein synthesis and cell death. 22 Given the ubiquitous and high expression of IL-3R by BPDCN and the lack of therapies available to treat BPDCN, SL-401 is a potential therapeutic for BPDCN. The present study evaluated the cytotoxicity of SL-401 against patient-derived BPDCN cell lines (CAL-1 and GEN2.2) and primary BPDCN cells isolated directly from 12 patients. The investigations were performed in vitro, as well as in vivo in a murine model of BPDCN. The aim of the study was to provide further support for the use of SL-401 in patients suffering from BPDCN. Methods Patients' cells and cell linesPeripheral blood or bone marrow cells were obtained for diagnostic purposes from 12 BPDCN patients (Table 1) from our national network that collects data and cells from cases diagnosed in France since (authorization number #DC-2008. BPDCN was diagnosed from the results of histopathology and immunostaining of cutaneous lesions, blood or bone marrow. 2,8 Two established cell lines derived from BPDCN patients were used (GEN 2.2, patent #0215927, Dr. Plumas, EFS Rhone-Alpes, Grenoble, France and CAL-1, Dr. Maeda, Nagasaki University, Japan) as well as TF/H-Ras (Prof. Frankel) and CD123 neg (MFI<800) Daudi cell lines (ACC78, DSMZ Braunschweig, Germany) as positive and negative controls, respectively. Other lymphoid and myeloid leukemic cells used to compare sensitivity to SL-401 are described in the Online Supplementary Appendix. Drug and cultureThe SL-401 drug (Stemline Therapeutics, New York, NY, USA) was stored at -80°C and tested at eight concentrations ranging from 365 pM to 0.08 fM (21 ng/mL to 0.4 ng/mL) in order to cover (including myeloperoxidase, CD13, CD33, CD117, CD15, CD65, CD14, CD64); T : T lymphoid markers (including membrane CD3, intracytoplasmic CD3, CD7, CD5, CD2, CD8) Cytotoxicity evaluation by flow cytometryFlow cytometry was performed using a CANTO II cytometer (BD Biosciences, San Jose, CA, USA) and DIVA 6.2 software (BD Biosciences). The cytotoxic effects of SL-401 and the various drugs were evaluated using annexin-V and 7-amino actinomycin D (AV/7AAD) and a panel of different monoclonal antibodies to gate the blastic population described in the Online Supplementary Appendix. In the mouse model, anti-mouse and anti-human CD45 plus anti-human CD123, CD4, CD56, CD304 were used to identify BPDCN human cells (Online Supplementary Appendix). A defined number of calibrated 3-mm latex beads (Flowco...

A novel agent SL-401 induces anti-myeloma activity by targeting plasmacytoid dendritic cells, osteoclastogenesis and cancer stem-like cells

“…Specifically, we found that pDC-MM cell interactions significantly increases IL-3 secretion; and importantly, that IL-3 both stimulate pDC survival 9 and MM cell growth. 10 Our and other prior studies showed that pDCs, including MM patient pDCs, highly express IL-3 R. 5,11–13 These findings demonstrate functional significance of IL-3 R-mediated signaling during pDC-MM interactions, and provide the rationale for therapeutically targeting IL-3 R-positive pDCs in MM.…”

Treatment of blastic plasmacytoid dendritic cell neoplasm

“…This led to the development of SL-401 an IL-3-diphtheria toxin conjugate that has demonstrated promise for BPCDN in early-phase trials. [61][62][63]65 Thus, a variety of prospective phase trials are greatly needed to unravel the many questions that persist in the treatment of this aggressive and elusive neoplasm.…”

“…Cytotoxicity is mediated by the catalytic domain after processing through the endosome, which inactivates protein synthesis by adenosine 59-diphosphate-ribosylating a diphthamide residue in elongation factor 2, resulting in cell lysis or apoptosis. Angelot-Delettra et al 61 demonstrated that SL-401 decreased viability in 75% of BPDCN primary cells compared with a 13% decrease in ALL and a 26% decrease in AML cells. The degree of cell killing was inversely proportional to the expression of the IL-3Ra chain (CD123) but not the IL-3Rb chain (CD131).…”

LXR agonist treatment of blastic plasmacytoid dendritic cell neoplasm restores cholesterol efflux and triggers apoptosis

“…Therapeutic strategies of BPDCN propose to interfere with IL-3 2,16,34,46 because BPDCNs express high levels of CD123, 2,26 and IL-3 is a BPDCN survival factor. 1,15 Here, we explored how LXR activation and LXR-induced cholesterol efflux interact with this pathway.…”