ALBERT

Beschreibung: The transcription factor IRF4 is essential for the survival of both normal plasma cells and the plasma cell malignancy multiple myeloma (MM). However the basis for this dependency remains uncertain, with the prevailing view that IRF4 loss in MM induces "death by a thousand cuts." Here we have explored the genetic basis for IRF4 addiction through CRISPR-Cas9 mediated deletion of IRF4 in three lenalidomide sensitive MM cells lines (MM1S, OPM2 and H929) and one resistant cell line (RPMI-8226). Loss of IRF4 resulted in marked loss of viability, irrespective of lenalidomide sensitivity, which was driven by two distinct mechanisms: 1) induction of apoptosis, which was rescued through prior deletion of apoptotic mediators BAX and BAK, and 2) proliferative arrest, which persisted despite rescue from apoptosis. RNA-sequencing following IRF4 inactivation identified a core group of 86 genes whose dysregulation was shared across all 4 MM cell lines. We identified 31 common down-regulated genes (IRF4 activated), including several with previously described roles in survival (such as KLF2, TNFRSF17/BCMA and MYB). Furthermore, MYC, a previously identified target of IRF4 known to play an important role in MM pathogenesis and survival, was down-regulated in 3 of the 4 cell lines. Most surprisingly, IRF4 inactivation resulted in 55 common up-regulated genes that included two BH3-only pro-apoptotic proteins, BMF and BCL2L11 (BIM). Up-regulation of BMF appeared more marked than BIM with an average fold change of 6.5x (range 2.7 - 10.3) vs 1.9x (range: 1.8 - 2.2) respectively. Remarkably, genetic ablation of BMF in the OPM2 cell line and BMF/BIM in the MM1S largely protected from the cell death observed following IRF4 inactivation, suggesting that IRF4 maintains MM survival through the transcriptional repression of BMF and BIM. Our results confirm the vital role of IRF4 for MM proliferation and survival, and shed further light into its critical downstream transcriptional targets. Most interestingly, we have demonstrated that the 'killer blow' appears to be the concerted effect of the BH3-only pro-apoptotic proteins BMF and BIM. Disclosures Huang: Genentech: Patents & Royalties: DCSH is an employee of the Walter and Eliza Hall Institute which receives milestone and royalty payments related to venetoclax.

Beschreibung: 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.

Beschreibung: Introduction Plasmablastic lymphoma (PBL) is a rare, aggressive large cell lymphoma, first described in 1997. PBL is strongly associated with immunodeficient states, such as HIV infection and solid organ transplantation, but up to one third of cases are reported to occur in immunocompetent patients. The pathogenesis of PBL is incompletely understood, though the oncogenic impact of EBV, in particular in the context of dysregulated immune surveillance, together with acquired abnormalities in the MYC pathway appear to play key roles in many cases. Plasma cell markers such as CD138 and CD38 are typically positive, as well as CD30 in a significant subset. Classical B cell markers such as CD20, CD19 and PAX5 are typically absent. The literature on clinical outcomes in PBL is generally limited to small, single-centre case series. Reports describe an aggressive disease of poor prognosis, with median survival of 8 to 15 months, with one series reporting a longer median survival of 32 months. Methods We retrospectively identified patients diagnosed with PBL between 1999 and 2019 from 16 sites across Australia, the United Kingdom and Canada. Patients aged ≥18 years with confirmed tissue diagnosis of PBL at their local treating centre were included. Factors associated with overall survival (OS) were analysed using Cox regression, stratified by site to account for heterogeneity across sites. Risk time for mortality began on the date of diagnosis and ended on the date of death. Patients who were alive, lost to follow-up or transferred to another centre for care, were censored on the date of last follow-up. Risk factors analysed included age, year of diagnosis, HIV status, MYC rearrangement status, CD30 status, lactate dehydrogenase level, disease stage by Lugano consensus criteria, and bone marrow involvement. Results We identified 197 patients with PBL (Table 1). The median age at diagnosis was 55 years (range 18-95) and there was a male predominance (69%). 37% of patients were HIV positive, 56% were HIV negative and 7% were either not tested or had missing results. Other immunosuppressive risk factors included solid organ transplant, allogeneic stem cell transplant (SCT), and immunosuppressive medication. No immunodeficient state was detected in 44%. Fifty per cent of patients were stage IV at diagnosis. Fifty-four per cent were staged using PET/CT. The median follow-up time from diagnosis was 1.36 years, with the longest follow up out to 18.4 years. There were 87 deaths (44%). For patients receiving first-line treatment with curative intent, the rate of complete remission was 57% (103 of 181 patients). Most patients (53%) received CHOP (cyclophosphamide, doxorubicin, vincristine, prednisolone)-based chemotherapy as first line, and 27% treatment of higher intensity than CHOP. Rituximab was administered to 20% and 10% were exposed to proteasome inhibitors as part of first line therapy. Five percent of patients underwent autologous SCT in first remission, and a further 5% after first relapse or later. The median survival time was 4.8 years, with a 5-year OS of 49% and 10-year OS of 45% (figure 1). In multivariate analysis the only adverse factors associated with OS were bone marrow involvement and stage IV disease. Patients without bone marrow involvement at diagnosis had improved OS, compared to those who did (hazard ratio (HR) 0.36, 95%CI 0.18-0.72, p=0.004) (figure 2). There was an increasing trend for mortality with higher disease stages (p-trend=0.002). The median survival was 14.1 years for stage I, 10.7 years for stage II, 5.1 years for stage III and 1.2 years for stage IV. However, only stage IV disease was independently associated with inferior OS in multivariate analysis (HR 2.93, 95%CI 1.43-6.00, p=0.003) (figure 3). OS did not change depending upon year of diagnosis. Conclusion We report a multinational retrospective cohort of patients diagnosed with PBL and to our knowledge the largest single series of PBL to date. OS was longer than previously published data, particularly in patients with early-stage disease. However, patients with stage IV disease and baseline bone marrow involvement had inferior OS. HIV infection did not affect outcome. These findings suggest that baseline bone marrow biopsy and PET staging are useful prognostic tools. There is also an ongoing need for the evaluation of the predictive value of PET imaging and novel agents in PBL, especially in higher-risk disease. Disclosures Di Ciaccio: Jansen: Honoraria, Other: travel and accomodation grant. Cwynarski:Takeda: Consultancy, Other: Conference/travel support; Roche: Consultancy, Other: Conference/travel support. Burton:Celgene: Honoraria; Leeds Teaching Hospitals NHS Trust: Current Employment; Takeda: Honoraria, Other: Travel Support; BMS: Honoraria; Roche: Honoraria, Other: Travel Support. Kuruvilla:Antengene: Honoraria; Janssen: Honoraria, Research Funding; Roche: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; AbbVie: Consultancy; AstraZeneca Pharmaceuticals LP: Honoraria, Research Funding; Merck: Consultancy, Honoraria; Celgene Corporation: Honoraria; Amgen: Honoraria; TG Therapeutics: Honoraria; Pfizer: Honoraria; Novartis: Honoraria; Bristol-Myers Squibb Company: Consultancy. McKay:Greater Glasgow and Clyde Health Board: Current Employment; Roche, Gilead, Takeda, Janssen: Other: For lectures etc; Roche: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BeiGene: Membership on an entity's Board of Directors or advisory committees; Janssen: Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Speakers Bureau; TAKEDA: Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Speakers Bureau. Linton:BeiGene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Conference/travel support; Roche: Consultancy, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Patents & Royalties; Janssen: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Hartley-Taylor: Honoraria; The Christie NHS Foundation Trust and The University of Manchester: Current Employment. Manos:Bristol-Myers Squibb: Other: Conference sponsorship. Hamad:Abbvie: Honoraria; Novartis: Honoraria.