Recent studies have demonstrated that the immunomodulatory drugs (IMiDs) lead to the degradation of the transcription factors Ikaros and Aiolos. However, why their loss subsequently leads to multiple ...myeloma (MM) cell death remains unclear. Using CRISPR-Cas9 genome editing, we have deleted IKZF1/Ikaros and IKZF3/Aiolos in human MM cell lines to gain further insight into their downstream gene regulatory networks. Inactivation of either factor alone recapitulates the cell intrinsic action of the IMiDs, resulting in cell cycle arrest and induction of apoptosis. Furthermore, evaluation of the transcriptional changes resulting from their loss demonstrates striking overlap with lenalidomide treatment. This was not dependent on reduction of the IRF4-MYC “axis,” as neither protein was consistently downregulated, despite cell death occurring, and overexpression of either factor failed to rescue for Ikaros loss. Importantly, Ikaros and Aiolos repress the expression of interferon-stimulated genes (ISGs), including CD38, and their loss led to the activation of an interferon-like response, contributing to MM cell death. Ikaros/Aiolos repressed CD38 expression through interaction with the nucleosome remodeling and deacetylase complex in MM. IMiD-induced loss of Ikaros or treatment with interferon resulted in an upregulation of CD38 surface expression on MM cells, priming for daratumumab-induced NK cell-mediated antibody-dependent cellular cytotoxicity. These results give further insight into the mechanism of action of the IMiDs and provide mechanistic rationale for combination with anti-CD38 monoclonal antibodies.
•Inactivation of Ikaros and Aiolos recapitulates the cell-intrinsic action of the IMiDs in MM, as well as transcriptional changes.•Loss of Ikaros or Aiolos results in upregulation of ISGs, including CD38, priming MM cells for anti-CD38 targeting.
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The transcription factor interferon regulatory factor 4 (IRF4) is critical for the development, maintenance, and function of plasma cells. The mechanism by which IRF4 exerts its action in mature ...plasma cells has been elusive due to the death of all such cells upon IRF4 loss. While we identify apoptosis as a critical pathway for the death of plasma cells caused by IRF4 loss, we also determine that IRF4 did not regulate the intrinsic apoptotic pathway directly. By using an inducible IRF4 deletion system in the presence of the overexpression of anti-apoptotic BCL2, we identify genes whose expression is coordinated by IRF4 and that in turn specify plasma cell identity and mitochondrial homeostasis.
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•IRF4 is a regulator of mitochondrial homeostasis in plasma cells•IRF4 regulates transcription of genes that specify plasma cell identity•Induction of IRF4 deletion leads to BCL2-inhibitable apoptosis in plasma cells
Plasma cells can provide lifelong immunity by the continued production of high-affinity, antigen-specific antibody. Low et al. reveal that the transcription factor IRF4 acts within established plasma cells to prevent apoptosis and maintain cellular identity and mitochondrial homeostasis.
Antibody-secreting plasma cells (PCs) are generated in secondary lymphoid organs but are reported to reside in an emerging range of anatomical sites. Analysis of the transcriptome of different ...tissue-resident (Tr)PC populations revealed that they each have their own transcriptional signature indicative of functional adaptation to the host tissue environment. In contrast to expectation, all TrPCs were extremely long-lived, regardless of their organ of residence, with longevity influenced by intrinsic factors like the immunoglobulin isotype. Analysis at single-cell resolution revealed that the bone marrow is unique in housing a compendium of PCs generated all over the body that retain aspects of the transcriptional program indicative of their tissue of origin. This study reveals that extreme longevity is an intrinsic property of TrPCs whose transcriptome is imprinted by signals received both at the site of induction and within the tissue of residence.
Antibody Secreting Cells (ASCs) are a fundamental component of humoral immunity, however, deregulated or excessive antibody production contributes to the pathology of autoimmune diseases, while ...transformation of ASCs results in the malignancy Multiple Myeloma (MM). Despite substantial recent improvements in treating these conditions, there is as yet no widely used ASC-specific therapeutic approach, highlighting a critical need to identify novel methods of targeting normal and malignant ASCs. Surface molecules specifically expressed by the target cell population represent ideal candidates for a monoclonal antibody-based therapy. By interrogating the ASC gene signature that we previously defined we identified three surface proteins, Plpp5, Clptm1l and Itm2c, which represent potential targets for novel MM treatments.
,
and
are highly and selectively expressed by mouse and human ASCs as well as MM cells. To investigate the function of these proteins within the humoral immune system we have generated three novel mouse strains, each carrying a loss-of-function mutation in either
,
or
. Through analysis of these novel strains, we have shown that Plpp5, Clptm1l and Itm2c are dispensable for the development, maturation and differentiation of B-lymphocytes, and for the production of antibodies by ASCs. As adult mice lacking either protein showed no apparent disease phenotypes, it is likely that targeting these molecules on ASCs will have minimal on-target adverse effects.
Multiple myeloma is an incurable and fatal cancer of immunoglobulin-secreting plasma cells. Most conventional therapies aim to induce apoptosis in myeloma cells but resistance to these drugs often ...arises and drives relapse. In this study, we sought to identify the best adjunct targets to kill myeloma cells resistant to conventional therapies using deep profiling by mass cytometry (CyTOF). We validated probes to simultaneously detect 26 regulators of cell death, mitosis, cell signaling, and cancer-related pathways at the single-cell level following treatment of myeloma cells with dexamethasone or bortezomib. Time-resolved visualization algorithms and machine learning random forest models (RFMs) delineated putative cell death trajectories and a hierarchy of parameters that specified myeloma cell survival versus apoptosis following treatment. Among these parameters, increased amounts of phosphorylated cAMP response element-binding protein (CREB) and the pro-survival protein, MCL-1, were defining features of cells surviving drug treatment. Importantly, the RFM prediction that the combination of an MCL-1 inhibitor with dexamethasone would elicit potent, synergistic killing of myeloma cells was validated in other cell lines, in vivo preclinical models and primary myeloma samples from patients. Furthermore, CyTOF analysis of patient bone marrow cells clearly identified myeloma cells and their key cell survival features. This study demonstrates the utility of CyTOF profiling at the single-cell level to identify clinically relevant drug combinations and tracking of patient responses for future clinical trials.
BACKGROUND
Demand for platelet (PLT) and plasma transfusions is increasing. Improved clinical supply and contingency planning requires greater understanding of usage profiles and urgency of clinical ...requirement.
STUDY DESIGN AND METHODS
This study was a random‐sample survey of PLT and plasma units produced in Victoria, Australia, to determine product disposition, recipient demographics, clinical indications for transfusion, and urgency (or “deferability”) of need. PLTs and fresh‐frozen plasma (FFP) were tagged with a case report form before distribution.
RESULTS
A total of 1252 PLT and 1837 FFP units were tagged, comprising 8.3 and 13.3% of all products issued during the study period. The fate of 1243 PLT and 1808 FFP units was determined. Of products issued, 72.2% of PLTs and 87.8% of FFP were transfused. Hematologic and oncologic disorders accounted for 63.9% of PLT transfusions, with acute myeloid leukemia alone accounting for 26%. Conversely, surgical patients received the largest proportion of FFP (40.4%), predominantly for cardiothoracic, solid organ transplant, and vascular surgery. Approximately 15% of PLT transfusions and 35% of plasma transfusions were required within 1 hour, and 80% of PLT transfusions and 90% of FFP transfusions were required within 24 hours. Wastage rates were higher in regional blood banks.
CONCLUSION
The PUPPY study is a comprehensive and detailed population‐based assessment of PLT and plasma usage, including urgency of use. It identifies specific clinical areas with high demand for PLT and FFP transfusion and demonstrates the high urgency of need for both products. These data inform clinical supply and contingency planning activities.
Background
Histologic transformation (HT) is an important event with adverse prognosis in the natural history of indolent lymphomas. There are minimal data on HT in the Australian setting.
Aims
To ...characterise patients with biopsy‐proven HT and their outcomes identified at a tertiary Australian Hospital.
Methods
All patients with biopsy‐proven HT during a 15‐year period (2002–2017) were included. Clinico‐pathological data were systematically collected from review of patient records. Survival estimates were assessed using the Kaplan–Meier method and compared using the log‐rank test. Associations between variables and clinical outcomes were evaluated using Cox's proportional hazards model.
Results
A cohort of 45 patients was identified with a median age of 66 years and the majority (59%) having high‐risk disease (Revised‐International Prognostic Index score ≥3). R‐CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone) induction was used in 69%, with an overall response rate of 82% (complete response (CR), 75%). Sixty‐one percent of these induction responders received consolidation, with autologous stem cell transplant (ASCT) performed in only 17% and rituximab maintenance given to 31%. With a median follow up of 47 months (range: 4–136), the 5‐year overall survival (OS) was 69% (95% CI: 52%, 81%). Chemotherapy‐naivety at HT was associated with a superior rate of CR (84% vs 54%, P = 0.057) and 5‐year OS (82% vs 46%, P = 0.012). Rituximab maintenance was associated with a durable progression‐free survival in induction responders.
Conclusions
Excellent OS was observed in this modern cohort of patients treated with rituximab‐containing induction and low rate of consolidation by ASCT, particularly in those who were chemotherapy‐naïve at HT.
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