Changes in immune cell populations following KappaMab, lenalidomide and low-dose dexamethasone treatment in multiple myeloma

Objectives

Lenalidomide (LEN) is used to treat multiple myeloma (MM) and shows in vitro synergy with KappaMab (KM), a chimeric antibody specific for Kappa Myeloma antigen, an antigen exclusively expressed on the surface of kappa-restricted MM cells. Lenalidomide, dexamethasone (DEX) and KM control MM via multiple immunomodulatory mechanisms; however, there are several additional effects of the drug combination on immune cells. Lenalidomide can increase T cell and NKT cell cytotoxicity and dendritic cell (DC) activation in vitro. We investigated the immune cell populations in bone marrow of patients treated with KM, LEN and low-dose DEX in kappa-restricted relapsed/refractory MM ex vivo and assessed association of those changes with patient outcome.

Methods

A cohort (n = 40) of patients with kappa-restricted relapsed/refractory MM, treated with KM, LEN and low-dose DEX, was analysed using a mass cytometry panel that allowed identification of immune cell subsets. Clustering analyses were used to determine significant changes in immune cell populations at time periods after treatment.

Results

We found changes in five DC and 17 T-cell populations throughout treatment. We showed an increase in activated conventional DC populations, a decrease in immature/precursor DC populations, a decrease in activated CD4 T cells and an increase in effector-memory CD4 T cells and effector CD8 T cells, indicating an activated immune response.

Conclusion

These data characterise the effects of LEN, DEX, and KM treatment on non-target immune cells in MM. Treatment may support destruction of MM cells by both direct action and indirect mechanisms via immune cells.

Response adaptive salvage with KTd and ASCT for functional high-risk multiple myeloma-The Australasian Leukemia and Lymphoma Group (ALLG) MM17 Trial

We evaluated re-induction incorporating carfilzomib-thalidomide-dexamethasone (KTd) and autologous stem cell transplantation (ASCT) for newly diagnosed multiple myeloma (NDMM) refractory, or demonstrating a suboptimal response, to non-IMID bortezomib-based induction. KTd salvage consisted of thalidomide 100 mg daily and dexamethasone 20 mg orally combined with carfilzomib 56 mg/m² days 1, 2, 8, 9, 15 and 16, of each 28-day cycle. Following four cycles, patients achieving a stringent complete response proceeded to ASCT whereas those who did not received a further two cycles then ASCT. Consolidation consisted of two cycles of KTd then Td to a total of 12 months post-ASCT therapy. Primary end-point was the overall response rate (ORR) with KTd prior to ASCT. Fifty patients were recruited. The ORR was 78% with EuroFlow MRD negativity of 34% in the intention-to-treat population and 65% in the evaluable population at 12 months post-ASCT. With follow-up >38 months median PFS and OS have not been reached with PFS and OS at 36 months of 64% and 80%, respectively. KTd was well tolerated with grade 3 and grade ≥4 adverse events rates of 32% and 10%, respectively. Response adaptive utilisation of KTd with ASCT is associated with both high-quality responses and durable disease control in functional high-risk NDMM.

Abstract 782: Circulating tumour DNA-based molecular response predicts treatment outcome in multiple myeloma

Background: Multiple myeloma (MM) is an incurable and multi-focal plasma cell malignancy manifesting predominantly within the bone marrow (BM). BM-based minimal residual disease (MRD) assessment utilising next generation flow (NGF - EuroFlowTM) has become an important measure of treatment response and a validated predictor of patient outcome. However, MRD is a single-site BM-derived assay and is conceptually limited due to the spatially heterogenous nature of MM and response to treatment.

Objective: We investigated if the evaluation of circulating tumour DNA (ctDNA) can be utilised as an adjunct to MRD analysis in predicting patient outcome.

Methods: Peripheral blood plasma was obtained at baseline (B), cycle 3 day 1 (C3D1) and end of study (EOS)/relapse from a phase II, multicentre single arm study of carfilzomib-thalidomide-dexamethasone (KTd) in 50 transplant-eligible newly diagnosed MM patients who were refractory to or had demonstrated a suboptimal response to first-line therapy. Extracted ctDNA was assessed utilising high-sensitivity targeted amplicon sequencing (TAS) of 22 MM-relevant genes. The variant allele frequency (VAF) of mutations at B was utilised to calculate a fold change in VAF at C3D1 and/or EOS. A negative fold change was defined as a decrease in VAF (ctDNA-) and a positive fold change an increase in VAF (ctDNA+) with the average fold change across all mutations calculated for each patient. EuroflowTM was performed on BM obtained pre and post-autologous stem cell transplant (ASCT) and at EOS and the ‘best MRD response’ achieved (MRD+ or MRD-) was recorded. The ctDNA and MRD responses were combined and correlated with progression-free survival (PFS) calculated using Kaplan-Meier estimates.

Results: A total of 45 patients had one or more mutations identified at B that could be tracked at C3D1 and/or EOS and 40 patients had one or more mutations that emerged at C3D1, EOS and/or relapse. Of these, 33 patients were evaluable for both MRD and ctDNA response. Patients that were MRD- and ctDNA- as best response for B mutations had a significantly longer PFS compared to those who were MRD+/ctDNA- or MRD-/ctDNA+ (p<0.0001, Log-rank tests; 23.9 months vs not reached for MRD-ctDNA-, Log rank-tests). Patients that were MRD- and ctDNA- at C3D1 (as early response for B mutations) had a significantly longer PFS compared to those that were MRD+/ctDNA- or MRD-/ctDNA+ (p=0.0011, 26.4 months vs not reached in MRD-ctDNA-, Log-rank tests).

Conclusions: Our results demonstrate that treated MM patients manifesting a molecular response, as defined by a reduction in ctDNA mutational burden, and who are also MRD- have a superior outcome to those patients who are MRD- but without a molecular response. These results for the first time confirm the utility of ctDNA-based early molecular response as a predictor of patient outcome in MM.

Citation Format: Sridurga Mithraprabhu, Tiffany Khong, Flora Yuen, John Reynolds, Brian Durie, Andrew Spencer. Circulating tumour DNA-based molecular response predicts treatment outcome in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 782.

Abstract 2366: Myeloma-derived circulating extracellular vesicles affect human stromal cell behaviour and promote tumor progression: A multi-omic approach

Background: We have shown that human stromal cells (HS5) treated with small extracellular vesicles (EV) derived from plasma of myeloma (MM) patients (MM-EV) promoted adhesion of human MM cell lines (HMCL), with preliminary proteomic profiling of MM- vs healthy donors HD-EV revealing enrichment of factors implicated in cell migration and adhesion.

Aims: 1) Demonstrate that MM-EV induce the formation of a tumour microenvironment (TME) favouring MM progression; 2) identify the protein content of MM-EV promoting this; 3) discover signaling drivers of EV-mediated functional remodelling of HS5 towards a pre-metastatic phenotype.

Methods: EV were enriched from 1mL plasma using a commercial kit. We performed: proteomic profiling of EV [x10 HD, x8 MM, x4 asymptomatic MM, x10 premalignant stage MGUS]; phosphoproteomic profiling and gene expression analysis by RNA sequencing of HS5 cells pre-treated with MM- vs HD/MGUS-EV; functional studies (co-culture HS5:HMCL).

Results: HS5 cells treated with MM-EV induced HMCL proliferation (p =.0026) and drug resistance (p =.0013) to anti-MM drugs (proteasome inhibitors) when compared to untreated HS5-cells.412 proteins were quantified by proteomic profiling of EV with 8/13 corresponding to universal cancer EV markers (Hoshino et al, Cell 2020). Gene ontology analysis of identified proteins (G:Profiler; p <.05) revealed enrichment for cellular component terms such as “extracellular vesicles/exosomes” and for biological processes including “cell communication”, “endocytosis”. Comparative analysis between our dataset and publicly available datasets revealed EV-markers with potential discriminatory specificity for MM. Comparative analysis revealed 40 proteins differentially regulated between HD- and MM-EV (p <.05; log2 fold change ≥2). A specific protein signature was found in ≥30% of MM-EV vs ≤30% HD-EV. A specific protein signature was also identified in ≥30% of MGUS-EV vs ≤30% HD/MM/SMM-EV. These proteins were not found in human whole plasma (Lehallier et al, Nat Med 2019) or solid tumors-EV (Hoshino et al, Cell 2020; Vinik et al, Science Advances 2020).120 phosphosites were differentially expressed between HS5 pre-treated with MM-EV vs HD-EV (>1.5-fold change, p<.05). Among the differentially expressed proteins were kinases,

phosphatases, translation and transcription regulators. 624 gene terms were differentially expressed between HS5 pre-treated with MM- vs HD-EV (GSEA, FDR < 0.05), including epidermal growth factor (EGF), tumor necrosis factor alpha (TNFA), epithelial to mesenchymal transition (EMT) signaling.

Conclusion: In this first of its kind studies in MM we show that MM-EV may play a key role in disease progression by re-programming the TME. Ongoing studies will indicate: the value of MM-EV as biomarkers; whether targeting interactions MM-EV:HS5 could enforce current therapeutic strategies.

Citation Format: Antonia Reale, Rong Xu, Irena Carmichael, Haoyun Fang, Jaynish S Sha, Tiffany Khong, Nicholas Bingham, Malarmathy Ramachandran, Maoshan Chen, David W Greening, Andrew Spencer. Myeloma-derived circulating extracellular vesicles affect human stromal cell behaviour and promote tumor progression: A multi-omic approach [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2366.

Extracellular Vesicles and Their Roles in the Tumor Immune Microenvironment

Tumor cells actively incorporate molecules (e.g., proteins, lipids, RNA) into particles named extracellular vesicles (EVs). Several groups have demonstrated that EVs can be transferred to target (recipient) cells, making EVs an important means of intercellular communication. Indeed, EVs are able to modulate the functions of target cells by reprogramming signaling pathways. In a cancer context, EVs promote the formation of a supportive tumor microenvironment (TME) and (pre)metastatic niches. Recent studies have revealed that immune cells, tumor cells and their secretome, including EVs, promote changes in the TME and immunosuppressive functions of immune cells (e.g., natural killer, dendritic cells, T and B cells, monocytes, macrophages) that allow tumor cells to establish and propagate. Despite the growing knowledge on EVs and on their roles in cancer and as modulators of the immune response/escape, the translation into clinical practice remains in its early stages, hence requiring improved translational research in the EVs field. Here, we comprehensively review the current knowledge and most recent research on the roles of EVs in tumor immune evasion and immunosuppression in both solid tumors and hematological malignancies. We also highlight the clinical utility of EV-mediated immunosuppression targeting and EV-engineering. Importantly, we discuss the controversial role of EVs in cancer biology, current limitations and future perspectives to further the EV knowledge into clinical practice.

Abstract 3412: Liquid biopsy for t(11;14)/blc2 identification in multiple myeloma

Background: Multiple myeloma (MM) is a spatially heterogeneous plasma cell malignancy of the bone marrow (BM). Venetoclax is a potent inhibitor of the anti-apoptotic protein BCL2 with evidence in MM that t(11;14) and high BCL2 expression confers greater sensitivity to venetoclax. BM biopsy is required for fluorescent in-situ hybridisation (FISH) detection of t(11;14) and the evaluation of MM cell BCL2 expression, with success being entirely dependent on the quality of the BM sample procured. We hypothesised that a liquid biopsy strategy to enable interrogation of cell-free circulating tumour (ct)DNA and extra-cellular (ex)RNA would represent a more practical and less invasive alternative strategy to BM biopsy for the detection of t(11;14) and the determination of MM cell BCL2 expression, respectively.

Methods: Blood and BM were obtained from 24 FISH characterised MM patients - normal karyotype (n=9), t(11;14) (n=11) and t(4;14) (n=4). Plasma derived ctDNA and exRNA was extracted utilising the QIAamp circulating nucleic acid kit and matched PBMC DNA was obtained for germ line controls. BM CD138+ MM cells for DNA and RNA extraction were selected with Miltenyi Biotec CD138 microbeads. A low density custom panel of unique capture probes (SSEL XT HS2, SureSelect Custom Tier 2, Agilent Technology), spanning approximately 10% of the CCND1 and IGH loci involved in t(11;14), was used for sequencing with approximately 5 million reads per sample with adapter sequences trimmed from the reads and aligned to the hg38 using bwa mem algorithm. Structural variant caller, Lumpy was used for identifying translocations, with low confidence reads excluded with a defined Z-score threshold. Droplet digital PCR (ddPCR) for BCL2 was performed on exRNA.

Results: The low-density capture seq identified t(11;14) in 6 of 11 (55%) of the CD138+ BM samples, but not in paired germ-line samples nor in the non-t(11;14) cohort BM samples. Interrogation of ctDNA identified t(11;14) in 1 of 11 samples but also in ctDNA from a patient labelled as being t(4;14) positive raising questions about the validity of the FISH attribution. We are now utilising a modification of the assay using ultra-high density capture probes with coverage approaching 100% of the IGH region and higher ctDNA input to detect translocations involving the IGH region on chromosome 14 with any partner chromosome, including translocations undetectable by FISH. BCL2 exRNA transcripts were detected in all patients with a range of 2-120 copies/ml of plasma with 79% of patients classified as ‘high’ BCL2 expression (>40 copies/ml of plasma) compared to 59% of the matched CD138+ BM samples.

Conclusion: We provide proof-of-concept of the potential of ctDNA and exRNA for t(11;14) detection and ddPCR quantitation of BCL2 expression, respectively, providing a rationale for further exploration of ctDNA and exRNA liquid biopsy testing as a strategy for identifying patients with t(11;14) and/or high BCL2.

Citation Format: Andrew Spencer, Sridurga Mithraprabhu, Jaynish Shah, Kawa Choi, Ashley George, Carlos Hader, Tiffany Khong. Liquid biopsy for t(11;14)/blc2 identification in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3412.

Abstract 3373: Circulating tumour DNA mutations correlate with relapse in a phase II trial of bortezomib-primary refractory multiple myeloma patients receiving salvage therapy

Background: Multiple myeloma (MM), an incurable plasma cell malignancy, has a relative 5-year overall survival (OS) of 48.5% for newly diagnosed patients. Prospective real-world data reveals that 23% of transplant eligible MM patients relapse within 12 months of starting first-line bortezomib based therapy with a median OS of only 16.8 months (high-risk - HR). Genomic studies for these HR patients could inform rational secondary therapeutic options and prolong survival. Bone marrow (BM) genomic analysis in MM has methodological and conceptual shortcomings owing to the spatially and genomically heterogeneous nature of MM that can be largely overcome with circulating tumour DNA (ctDNA) analysis.

Objective: To determine whether ctDNA analysis can define the mutational spectrum of patients with HR MM.

Design: Phase II, multicentre single arm study of carfilzomib-thalidomide-dexamethasone (KTd) in 50 transplant-eligible newly diagnosed MM patients from September 2016 to April 2018 (Australasian Leukaemia and Lymphoma Group (ALLG) - MM17 trial) who were refractory (REF) to or demonstrated a suboptimal response (SOR) to bortezomib-based induction therapy. A total of 186 peripheral blood plasma and BM samples were obtained at baseline, at Cycle 3 day 1 (C3D1), end of the study (EOS) and/or at relapse. Somatic variants were identified with an ultra-sensitive targeted amplicon sequencing (TAS) assay incorporating 22-genes known to be mutated in MM. The mutational spectrum was correlated with progression-free survival (PFS) and OS.

Results: TAS of 31 BM samples and 48 ctDNA samples revealed that in BM, KRAS mutations were detected in 42% of patients followed by ATR in 29% while in ctDNA, ATR mutations were prominent (36%), followed by FGFR3 and ATM (27% and 26.8%). We compared the ctDNA mutational spectrum at baseline between non-relapse and relapse patients on KTd and identified a significant difference in the proportion of patients with specific mutations - RAS/RAF: 3% vs 25%; ATM/ATR/TP53: 17% vs 41%, respectively (p<0.0001). Patients with RAS/RAF and/or ATM/ATR/TP53 ctDNA mutations at baseline had significantly shorter PFS and OS (p=0.003 and p=0.02, respectively). Comparative ctDNA TAS for baseline, C3D1, EOS/relapse, demonstrated that in 87.5% of patients, one or more dominant mutations driving relapse in KTd were already present prior to starting salvage therapy. We also performed ctDNA analysis to compare patients who were REF or SOR to front-line therapy and identified 62% of REF patients had RAS/RAF or ATM/ATR/TP53 mutation compared to 35% of SOR patients (p=0.0002, Fisher’s exact test).

Conclusions: Our results demonstrate that RAS/RAF and ATM/ATR/TP53 mutations in ctDNA are prognostic biomarkers of outcome to secondary salvage therapy in HR patients thus enabling design of targeted therapeutic approaches to improve survival.

Citation Format: Sridurga Mithraprabhu, John Reynolds, Anna Kalff, Krystal Bergin, Rose Turner, Hang Quach, Noemia Horvath, Ian Kerridge, Flora Yuen, Kawa Choi, Malarmathy Ramachandran, Ashley George, Tiffany Khong, Brian Durie, Andrew Spencer. Circulating tumour DNA mutations correlate with relapse in a phase II trial of bortezomib-primary refractory multiple myeloma patients receiving salvage therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3373.

Abstract 3491: New targets and new approaches for multiple myeloma: Extracellular vesicles as functional liquid biomarkers

Background: We have previously demonstrated that stromal cells (HS5) pre-treated with small extracellular vesicles (sEV) enriched from blood plasma of myeloma (MM) patients promoted adhesion of human MM cell lines (HMCL), with preliminary proteomic profiling of MM-sEV (vs healthy donors-HD) revealing enrichment of factors implicated in cell migration and adhesion.

Aims: To demonstrate that plasma-derived MM-sEV induce a microenvironment favoring MM progression and identify the protein content of plasma-sEV that promotes this.

Methods: sEV were enriched from plasma (1mL) using a commercial kit. Proteomic profiling (nLC and high-resolution mass spectrometry, Orbitrap HF-X) of plasma-sEV derived from HD (x10) and patients with MM (x8) or pre-malignant conditions (monoclonal gammopathy of undetermined significance - MGUS x10; smouldering/asymptomatic MM - SMM x4), and functional studies (co-culture system HS5:HMCL) were performed.

Results: Stromal cells pre-treated with MM-sEV induced both HMCL proliferation (p < 0.05) and drug resistance (p < 0.0001) to anti-MM drugs (proteasome inhibitors) when compared to untreated stromal cells.The protein concentrations of MM-sEV positively correlated with tumor burden (r0.77; p=0.024).A total of 412 proteins were detected and quantified by proteomic profiling of plasma-sEV with 13 reported as highly enriched in EV marker databases (ExoCarta top 100) and 8/13 corresponding to universal cancer EV-markers proposed by Hoshino et al, Cell 2020. Gene ontology analysis of identified proteins (G:Profiler; p < 0.05) revealed enrichment for cellular component terms such as “extracellular vesicles/exosomes” and for several biological processes including “cell communication”, “endocytosis”, “cell migration”, “cellular response to stimulus”, “immune response”. Comparative analysis between our dataset and several publicly available datasets revealed sEV-markers with potential discriminatory specificity for MM, MGUS or SMM. Comparative analysis revealed 40, 40 and 41 proteins differentially regulated between HD-sEV and MM-sEV or MGUS-sEV or SMM-sEV (P < 0.05; log2 fold change ≥2). A specific protein signature identified in MM-sEV was found in ≥30% of MM-sEV but <30% HD-sEV. Specific protein signatures were also identified in MGUS-sEV (≥30% of MGUS-sEV but <30% HD-sEV or MM-sEV or SMM-sEV) and SMM-sEV (≥30% of SMM-sEV but <30% HD-sEV or MM-sEV or MGUS-sEV). These proteins were not found in human whole plasma (Lehallier et al, Nat medicine 2019) or solid tumors-derived sEV described by Hoshino et al (Cell 2020) and Vinik et al (Science Advances 2020).

Conclusions: MM-sEV may play an important role in disease progression by re-programming the tumor microenvironment. The characterization and proteomic profiling of disease-specific circulating sEV as a biomarker discovery strategy may provide translational applications in MM.

Citation Format: Antonia Reale, Tiffany Khong, Rong Xu, Irena Carmichael, Haoyun Fang, Nicholas Bingham, Sridurga Mithraprabhu, Maoshan Chen, Malarmathy Ramachandran, David W. Greening, Andrew Spencer. New targets and new approaches for multiple myeloma: Extracellular vesicles as functional liquid biomarkers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3491.

Circulating tumor DNA analysis and association with relapse in patients with primary refractory multiple myeloma receiving secondary salvage therapy

8037

Background: Multiple myeloma (MM) is an incurable plasma cell malignancy with a 5 year-median overall survival (OS) in newly diagnosed (ND) patients. Real-world data reveals that 23% of transplant eligible (TE) ND MM patients relapse within 12 months of starting first-line bortezomib (1LB) based therapy and of these ̃50% will fail secondary therapy and die within 18 months. It is currently impossible to identify these high-risk patients and genomic studies could potentially inform alternative secondary therapeutic options. We propose that circulating tumour DNA (ctDNA) analysis could provide a more holistic approach to determine genomics of high-risk patients than bone marrow (BM) tumour DNA analysis in this genetically heterogenous multi-site malignancy. Methods: Peripheral blood plasma and BM samples (n = 186) were obtained at baseline, cycle 3 day 1 (C3D1), end of the study (EOS) and/or relapse, whichever appeared earlier, from a Phase II multicentre single arm study of carfilzomib-thalidomide-dexamethasone (KTd) in 50 TE ND MM patients who were refractory or registered suboptimal response to 1LB (Australasian Leukaemia and Lymphoma Group - MM17 trial). Somatic variants were identified in BM or ctDNA with ultra-sensitive targeted amplicon sequencing of 22-genes known to be mutated in MM. Mutational spectrum was correlated to standard MM risk factors including International Staging System (ISS), response to 1LB and KTd, cytogenetics/FISH, lactate dehydrogenase (LDH) levels, progression-free survival (PFS) and OS. Results: Our initial analysis of ctDNA mutational proportions between patients who did not or did experience relapse on KTd revealed a significantly higher proportion of RAS/RAF (3% vs 25%), or ATM/ATR/TP53 (17% vs 41%; p < 0.0001), respectively, in relapse patients. Subsequently, we correlated ctDNA RAS/RAF and/or ATM/ATR/TP53 mutational presence to standard MM risk factors. We identified a shorter PFS and OS for ISS Stage 2 and 3 compared to Stage 1 patients (p = 0.002 and p = 0.02, respectively) and a significantly higher proportion of RAS/RAF or ATM/ATR/TP53 mutations in patients with refractory as compared to sub-optimal response to 1LB therapy (p = 0.0002). Patients with RAS/RAF or ATM/ATR/TP53 mutations in ctDNA at the time of starting salvage therapy also had a shorter PFS and OS on KTd (p = 0.003 and p = 0.02, respectively). Sequential ctDNA analysis discovered that in 87.5% of patients, one or more of the dominant mutations present at the time of relapse were already present at the start of salvage therapy. Conclusions: Our analysis reveals that RAS/RAF and ATM/ATR/TP53 mutations in ctDNA could be prognostic biomarkers of response to secondary salvage therapy in primary refractory patients thus providing the opportunity to design targeted salvage treatment paradigms in high-risk MM patients.

Translational Potential of RNA Derived From Extracellular Vesicles in Multiple Myeloma

The cross-talk between tumour cells and stromal cells is a hallmark of multiple myeloma (MM), a blood cancer that still remains incurable despite increased knowledge of its biology and advances in its treatment. Extracellular vesicles (EVs) derived from both tumour and stromal cells have been shown to play an important role in mediating this cross-talk ultimately favouring MM progression and drug resistance. Furthermore, EVs and their content including RNA (EV-RNA) have been successfully isolated from blood and are being explored as liquid biomarkers in MM with the potential to improve diagnosis and monitoring modalities with a minimally-invasive and repeatable analysis, i.e. liquid biopsy. In this review, we describe both the role of EV-RNA in defining the biological features of MM and their potential translational relevance as liquid biomarkers, therapeutic targets and delivery systems. We also discuss the limitations and technical challenges related to the isolation and characterization of EVs and provide a perspective on the future of MM-derived EV-RNA in translational research.

Cereblon pathway biomarkers and immune profiles in patients with myeloma receiving post-ASCT lenalidomide maintenance (LEOPARD)

LEOPARD was a single arm, phase II study of lenalidomide (LEN) and alternate day prednisolone maintenance in patients with newly diagnosed multiple myeloma (MM) following autologous stem cell transplantation (ASCT). Sixty patients were enrolled. Estimated median potential follow-up was 44 m, median PFS was 38.3 m, median OS was not reached (landmark 36 m OS: 71.4%). Correlative immunohistochemistry performed on pre-ASCT trephines demonstrated high MM tumor cereblon (total/cytoplasmic) was associated with superior OS (p = .045, p = .031, respectively), whereas high c-Myc was associated with inferior PFS (p = .04). Patients with high cereblon (total/nuclear) were more likely to improve depth of response, whereas patients with high c-Myc were less likely, suggesting alternative/more effective post-ASCT strategies for patients with high c-Myc need identification. Peripheral blood immune profiling (mass cytometry) informed a more sustained response to LEN maintenance, demonstrating enrichment of activated/cytotoxic NK cells and cytotoxic T cells in patients with durable responses, contrasting with enrichment of B-regs in early relapsers.

Targeting histone acetylation dynamics and oncogenic transcription by catalytic P300/CBP inhibition

To separate causal effects of histone acetylation on chromatin accessibility and transcriptional output, we used integrated epigenomic and transcriptomic analyses following acute inhibition of major cellular lysine acetyltransferases P300 and CBP in hematological malignancies. We found that catalytic P300/CBP inhibition dynamically perturbs steady-state acetylation kinetics and suppresses oncogenic transcriptional networks in the absence of changes to chromatin accessibility. CRISPR-Cas9 screening identified NCOR1 and HDAC3 transcriptional co-repressors as the principal antagonists of P300/CBP by counteracting acetylation turnover kinetics. Finally, deacetylation of H3K27 provides nucleation sites for reciprocal methylation switching, a feature that can be exploited therapeutically by concomitant KDM6A and P300/CBP inhibition. Overall, this study indicates that the steady-state histone acetylation-methylation equilibrium functions as a molecular rheostat governing cellular transcription that is amenable to therapeutic exploitation as an anti-cancer regimen.

Phase II trial of single-agent panobinostat consolidation improves responses after sub-optimal transplant outcomes in multiple myeloma

Panobinostat is a pan-deacetylase inhibitor that modulates the expression of oncogenic and immune-mediating genes involved in tumour cell growth and survival. We evaluated panobinostat-induced post-transplant responses and identified correlative biomarkers in patients with multiple myeloma who had failed to achieve a complete response after autologous transplantation. Patients received panobinostat 45 mg administered three-times weekly (TIW) on alternate weeks of 28-day cycles commencing 8-12 weeks post-transplant. Twelve of 25 patients (48%) improved their depth of response after a median (range) of 4·3 (1·9-9·7) months of panobinostat. In responders, T-lymphocyte histone acetylation increased after both three cycles (P < 0·05) and six cycles (P < 0·01) of panobinostat when compared to baseline, with no differences in non-responders. The reduction in the proportion of CD127+ CD8+ T cells and CD4:CD8 ratio was significantly greater, after three and six cycles of panobinostat compared to pre-transplant, in non-responders when compared to responders. Whole marrow RNA-seq revealed widespread transcriptional changes only in responders with baseline differences in genes involved in ribosome biogenesis, oxidative phosphorylation and metabolic pathways. This study confirmed the efficacy of panobinostat as a single agent in multiple myeloma and established acetylation of lymphocyte histones, modulation of immune subsets and transcriptional changes as pharmacodynamic biomarkers of clinical benefit.

Human myeloma cell- and plasma-derived extracellular vesicles contribute to functional regulation of stromal cells

Circulating small extracellular vesicles (sEV) represent promising non-invasive biomarkers that may aid in the diagnosis and risk-stratification of multiple myeloma (MM), an incurable blood cancer. Here, we comprehensively isolated and characterized sEV from human MM cell lines (HMCL) and patient-derived plasma (psEV) by specific EV-marker enrichment and morphology. Importantly, we demonstrate that HMCL-sEV are readily internalised by stromal cells to functionally modulate proliferation. psEV were isolated using various commercial approaches and pre-analytical conditions (collection tube types, storage conditions) assessed for sEV yield and marker enrichment. Functionally, MM-psEV was shown to regulate stromal cell proliferation and migration. In turn, pre-educated stromal cells favour HMCL adhesion. psEV isolated from patients with both pre-malignant plasma cell disorders (monoclonal gammopathy of undetermined significance [MGUS]; smouldering MM [SMM]) and MM have a similar ability to promote cell migration and adhesion, suggesting a role for both malignant and pre-malignant sEV in disease progression. Proteomic profiling of MM-psEV (305 proteins) revealed enrichment of oncogenic factors implicated in cell migration and adhesion, in comparison to non-disease psEV. This study describes a protocol to generate morphologically-intact and biologically functional sEV capable of mediating the regulation of stromal cells, and a model for the characterization of tumour-stromal cross-talk by sEV in MM.

TOP2A expression predicts responsiveness to carfilzomib in myeloma and informs novel combinatorial strategies for enhanced proteasome inhibitor cell killing

Microarray was utilized to determine if a genetic signature associated with resistance to carfilzomib (CFZ) could be identified. Twelve human myeloma (MM) cell lines (HMCLs) were treated with CFZ and a cell-viability profile was assessed categorizing HMCLs as sensitive or resistant to CFZ. The gene expression profiles (GEP) of untreated resistant versus sensitive HMCLs revealed 29 differentially expressed genes. TOP2A, an enzyme involved in cell cycle and proliferation, was overexpressed in carfilzomib-resistant HMCLs. TOP2A protein expression levels, evaluated utilizing trephine biopsy specimens acquired prior to treatment with proteasome inhibitors, were higher in patients failing to achieve a response when compared to responding patients. Logistic-regression analysis confirmed that TOP2A protein expression was a highly significant predictor of response to PIs (AUC 0.738). Further, the combination of CFZ with TOP2A inhibitors, demonstrated synergistic cytotoxic effects in vitro, providing a rationale for combining topoisomerase inhibitors with CFZ to overcome resistance in MM.

Brick plots: an intuitive platform for visualizing multiparametric immunophenotyped cell clusters

BACKGROUND

The advent of mass cytometry has dramatically increased the parameter limit for immunological analysis. New approaches to analysing high parameter cytometry data have been developed to ease analysis of these complex datasets. Many of these methods assign cells into population clusters based on protein expression similarity.

RESULTS

Here we introduce an additional method, termed Brick plots, to visualize these cluster phenotypes in a simplified and intuitive manner. The Brick plot method generates a two-dimensional barcode that displays the phenotype of each cluster in relation to the entire dataset. We show that Brick plots can be used to visualize complex mass cytometry data, both from fundamental research and clinical trials, as well as flow cytometry data.

CONCLUSION

Brick plots represent a new approach to visualize complex immunological data in an intuitive manner.

P3839Hypertension or hypertrophic cardiomyopathy? Using cardiovascular magnetic resonance imaging to unmask the great imitator

Background

Structural cardiac adaptations due to hypertension (HTN) present a diagnostic challenge when differentiating from hypertrophic cardiomyopathy (HCM), using traditional imaging techniques such as echocardiography (echo). Cardiac magnetic resonance imaging (CMR) offers reproducible anatomical, functional quantification and myocardial tissue characterisation which discriminates between hypertension and HCM.

Purpose

To identify hypertensive individuals with undiagnosed HCM using CMR imaging.

Methods

100 consecutive hypertensive patients underwent CMR at a tertiary centre dedicated blood pressure clinic (55% male, mean age 51 years). In keeping with ESC guidelines, end diastolic wall thickness (EDWT) ≥15mm identified individuals within the “grey zone” between hypertension and with a potential HCM diagnosis. 19 individuals were referred on to the dedicated inherited cardiac conditions clinic for further evaluation. Four patients expressed a definitive LV phenotype and were diagnosed with HCM. CMR parameters were compared in three groups: Hypertensive (HTN), “grey zone” Hypertensive (GZH) and HCM.

Results

CMR demonstrated end diastolic wall thickness (EDWT) >11 mm in 50% of hypertensives. 73% of the referred patients were Afro-Caribbean (AC) and all 4 HCM patients were AC. All referrals demonstrated EDWTs ≥14mm, 9 (47%) demonstrated late gadolinium enhancement of which 3 (16%) had HCM. Three had asymmetrical septal hypertrophy – 2 were in the HCM cohort and one underwent endomyocardial biopsy confirming HTN. Left ventricular mass index (LVMI) was significantly higher in GZH compared to HTN (p<0.0001) and in HCM compared to HTN (p=0.0004). EDWT was significantly greater in GZH compared to HTN (p<0.0001) and in HCM compared to HTN (p=0.0002). There was no significant difference in these parameters between GZH and HCM.

Table 1. P-values for CMR data in hypertensive (HTN), gray zone hypertensive (GZH) and hypertrophic cardiomyopathy (HCM) cohorts CMR Parameter HCM vs. HTN GZH vs. HTN GZH vs. HCM EDVI NS p=0.025 NS EDWT p=0.0002 p<0.0001 NS LVMI p=0.0004 p<0.0001 NS

Conclusion

This study reports a 4% prevalence of HCM among hypertensive patients - 20 x greater than in the general population - which would be left undiagnosed using echo alone. Screening hypertensive individuals with CMR is not routine but we advocate its use in these individuals especially in Afro Caribbeans and in those in the “grey zone”, to identify undiagnosed HCM, which has significant implications for lifestyle modification and family screening.

Acknowledgement/Funding

Cardiac Risk in the Young

Utility of Circulating Cell-Free RNA Analysis for the Characterization of Global Transcriptome Profiles of Multiple Myeloma Patients

In this study, we evaluated the utility of extracellular RNA (exRNA) derived from the plasma of multiple myeloma (MM) patients for whole transcriptome characterization. exRNA from 10 healthy controls (HC), five newly diagnosed (NDMM), and 12 relapsed and refractory (RRMM) MM patients were analyzed and compared. We showed that ~45% of the exRNA genes were protein-coding genes and ~85% of the identified genes were covered >70%. Compared to HC, we identified 632 differentially expressed genes (DEGs) in MM patients, of which 26 were common to NDMM and RRMM. We further identified 54 and 191 genes specific to NDMM and RRMM, respectively, and these included potential biomarkers such as LINC00863, MIR6754, CHRNE, ITPKA, and RGS18 in NDMM, and LINC00462, PPBP, RPL5, IER3, and MIR425 in RRMM, that were subsequently validated using droplet digital PCR. Moreover, single nucleotide polymorphisms and small indels were identified in the exRNA, including mucin family genes that demonstrated different rates of mutations between NDMM and RRMM. This is the first whole transcriptome study of exRNA in hematological malignancy and has provided the basis for the utilization of exRNA to enhance our understanding of the MM biology and to identify potential biomarkers relevant to the diagnosis and prognosis of MM patients.

Abstract 454: The role of autophagy in multiple myeloma disease progression

Multiple Myeloma (MM) is an incurable hematologic neoplasm characterized by accumulation of malignant plasma cells in the bone marrow (BM). MM cells establish close ties with the BM, however at late stages they utilize as yet unknown mechanisms to acquire independence from the microenvironment and survive in extramedullary/nutrient deprived sites. Autophagy, a process responsible for degradation of proteins and organelles under stress conditions, has been suggested as a mechanism whereby tumor cells can withstand metabolic stress.

Using two newly acquired human myeloma cell lines (HMCL), TK1 and TK2, from the medullary and extramedullary sites of a MM patient respectively, we investigated the ability of autophagy to confer stress/glutamine deprivation tolerance.

Results

HMCLs require exogenous L-Glutamine (Gln) for sustained proliferation in vitro. However, when TK1 and TK2 were grown under Gln deprivation conditions (8mM, 4mM, 2mM, 0mM) we observed striking differences in their growth response. The TK2 (peripheral blood) cell line continued proliferating until day 14 (p=0.0046), whereas proliferation of the TK1 cell line significantly decreased in the absence of Gln (p=0.0028 between 8mM and 0mM). Furthermore, the proliferative advantage of TK2 was abrogated at 2mM and 0mM of Gln by the use of an autophagy inhibitor (chloroquine [CQ] (p=0.000235 and p=0.000069 respectively), implicating this process in Gln deprivation tolerance of TK2.

Additionally, Gln concentration was inversely correlated with TK1 survival, but not TK2, as measured by annexin-V/PI staining. Cell death in TK1 increased at 24h, from 36.022% at Gln 8mM to 56.2% at Gln 0mM, irrespective of autophagy inhibition. In TK2 cells, Gln deprivation did not cause a significant increase in cell death, whereas inhibition of autophagy increased cell death by two-fold. Accordingly, apoptosis (as measured by PARP cleavage) was induced by the addition of CQ only in TK2 under Gln deprivation. Resistance of TK2 cells to metabolic stress also correlated with up-regulation of the autophagic pathway upon CQ exposure, as demonstrated by a higher LC3BII/I turnover and the presence of autophagic vacuoles in TK2 (but not TK1) cells.

In addition to upregulation of autophagy, Gln deprivation also induced the expression of glutamine synthetase in TK2 but not TK1 cells. Chemical inhibition of this enzyme by methionine-sulfoximine (5mM) under Gln deprivation conditions was able to induce significant cell death in TK2 and not TK1 (32.57% and 2.53% increase respectively). These data demonstrate that Gln synthesis is an additional mechanism whereby TK2 cells tolerate Gln starvation.

In conclusion we have shown that MM survival outside the BM can be attributed to the ability of cells to overcome “glutamine addiction” due to up-regulation of autophagy and ability to synthesise Gln. Thus, autophagy inhibition is an attractive alternative approach to target late-stage, Gln independent, metastatic cells.

Citation Format: Ioanna Savvidou, Sahan Chandrasekara, Tiffany Khong, Andrew Spencer. The role of autophagy in multiple myeloma disease progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 454.

Circulating Tumour DNA Analysis for Tumour Genome Characterisation and Monitoring Disease Burden in Extramedullary Multiple Myeloma

Mutational characterisation in extramedullary multiple myeloma (EM-MM) patients is challenging due to inaccessible EM plasmacytomas, unsafe nature of multiple biopsies and the spatial and temporal genomic heterogeneity apparent in MM (Graphical abstract). Conventional monitoring of disease burden is through serum markers and PET-CT, however these modalities are sometimes inadequate (serum markers), not performed in a timely manner (PET-CT) and uninformative for identifying mutations driving disease progression. DNA released into the blood by tumour cells (ctDNA) contains the predominant clones derived from the multiple disease foci. Blood-derived ctDNA can, therefore, provide a holistic illustration of the major drivers of disease progression. In this report, the utility of ctDNA, as an adjunct to currently available modalities in EM-MM, is presented for a patient with EM and oligosecretory (OS) disease. Whole exome sequencing of contemporaneously acquired tumour tissue and matched ctDNA samples revealed the presence of spatial and temporal genetic heterogeneity and the identification of pathways associated with drug resistance. Longitudinal monitoring of plasma samples revealed that ctDNA can be utilised to define the dynamic clonal evolution co-existent with disease progression and as an adjunct non-invasive marker of tumour burden.

Dysregulated Class I histone deacetylases are indicators of poor prognosis in multiple myeloma

Histone deacetylases (HDAC) control gene expression through their ability to acetylate proteins, thereby influencing a diverse range of cellular functions. Class I HDAC (HDAC1-3 and 8) and HDAC6 are predominantly upregulated in malignancies and their altered expression in some cancers has a significant prognostic implication. The expression and prognostic consequence of dysregulated Class I HDAC and HDAC6, key players in multiple myeloma (MM), are unknown. This study hypothesized that HDAC are dysregulated in MM and patients with high expression have significantly poorer prognostic outcomes. Quantitative PCR for 11 HDAC (Class I, II, and IV) was performed in genetically heterogeneous human myeloma cell lines (HMCL) and primary MM and compared to normal plasma cells (PC). In HMCL, HDAC1-3 and 8 (Class I), and HDAC5 and HDAC10 (Class II) were significantly upregulated compared to normal PC. In primary MM, the median expression level of all of the HDAC, except HDAC1 and HDAC11, were elevated when compared to normal PC. Patients with higher levels of HDAC1-3, HDAC4, HDAC6, and HDAC11 transcripts demonstrated a significantly shorter progression-free survival (PFS). Immunohistochemical staining for HDAC1 and HDAC6 on bone marrow trephines from a uniformly treated cohort of transplant eligible MM patients revealed that HDAC1 protein was detectable in most patients and that higher levels of MM cell HDAC1 protein expression (≥90 % versus ≤20 % MM cell positivity) correlated with both shorter PFS (P = 0 .07) and shorter overall survival (P = 0 .003). Conversely, while the majority of patients expressed HDAC6, there was no correlation between HDAC6 levels and patient outcome. Together, these results indicate that overexpression of Class I HDAC, particularly HDAC1, is associated with poor prognosis in MM.

MDX-1097 induces antibody-dependent cellular cytotoxicity against kappa multiple myeloma cells and its activity is augmented by lenalidomide

MDX-1097 is an antibody specific for a unique B cell antigen called kappa myeloma antigen (KMA) that consists of cell membrane-associated free kappa light chain (κFLC). KMA was detected on kappa human multiple myeloma cell lines (κHMCLs), on plasma cells (PCs) from kappa multiple myeloma (κMM) patients and on κPC dyscrasia tissue cryosections. In primary κMM samples, KMA was present on CD38+ cells that were CD138 and CD45 positive and/or negative. MDX-1097 exhibited a higher affinity for KMA compared to κFLC and the latter did not abrogate binding to KMA. MDX-1097-mediated antibody-dependent cellular cytotoxicity (ADCC) and in vitro exposure of target cells to the immunomodulatory drug lenalidomide resulted in increased KMA expression and ADCC. Also, in vitro exposure of peripheral blood mononuclear cells (PBMCs) to lenalidomide enhanced MDX-1097-mediated ADCC. PBMCs obtained from myeloma patients after lenalidomide therapy elicited significantly higher levels of MDX-1097-mediated ADCC than cells obtained prior to lenalidomide treatment. These data establish KMA as a relevant cell surface antigen on MM cells that can be targeted by MDX-1097. The ADCC-inducing capacity of MDX-1097 and its potentiation by lenalidomide provide a powerful rationale for clinical evaluation of MDX-1097 alone and in combination with lenalidomide.

Abstract 1015: Targeting actin cytoskeleton pathway overcomes resistance to histone deacetylase inhibitors in multiple myeloma cells

Histone deacetylase inhibitors (HDACi) are novel therapeutics compounds being utilised in multiple myeloma (MM) clinical trials in combination with approved and investigational agents. While proteasome inhibitors are known to synergise effectively with HDACi, there is a lack of understanding concerning other potential partner drugs. In this report, utilising human myeloma cell lines (HMCL) as a paradigm, gene expression profile was performed to determine if a genetic signature associated with HDACi-resistance could be identified. Nine HMCLs were treated with HDACi (LBH589, SAHA or FK228) and cell death proportion determined after 48 hours through flow cytometric enumeration of propidium iodide staining. Of the nine cell lines, five were sensitive (70-90% cell death), two showed an intermediate response (70-40%) and two were resistant (40-10%) to HDACi. Following the determination of HDACi-response of HMCLs, RNA was extracted from untreated cell lines and gene expression profiling was performed utilising the Illumina HT-12 platform. Analysis revealed that 97 genes were differentially regulated between the sensitive and resistant cell lines. Gene ontology enrichment analysis identified six pathways that were significantly different and these included notch signalling pathway (p=0.01), protein processing in endoplasmic reticulum (p=0.02), glutathione metabolism (p=0.01), melanoma (p=0.02), regulation of actin cytoskeleton (p=0.03) and apoptosis (p=0.03). Furthermore, 4889 probes were tested for their correlation to grade of sensitivity using Spearmann rank algorithm and 35 genes were found to have &gt;80% correlation. Enrichment analyses indicated two pathways as being significantly different based on their correlation to HDACi-sensitivity and these included regulation of actin cytoskeleton (p=0.03) and protein processing in endoplasmic reticulum (p=0.02). The actin cytoskeleton represents a major network of proteins that impinge on motility, invasion, polarity, survival and growth of normal cells, and is often altered in tumour cells. Actin cytoskeleton modifications are known to be involved in MM cell metastasis and a number of agents that destabilize the action cytoskeleton have been utilised in MM pre-clinical studies. When HDACi-resistance cell lines were treated with a combination of HDACi and actin cytoskeleton pathway inhibitors (MEK inhibitor - GSK1120212, focal adhesion inhibitors - TAE-226 and PF-573228 and actin cytoskeleton destabilising agents - NVP-HSP990 and AUY922), synergistic cell death was observed, indicating that these agents can be used in combination with HDACi for MM therapy. This report provides a rationalistic approach for identification of HDACi partner drugs for anti-MM therapy and has provided the framework to identify promising new therapeutic combinations for the treatment of MM utilising HDACi.

Citation Format: Sridurga Mithraprabhu, Tiffany Khong, Andrew Spencer. Targeting actin cytoskeleton pathway overcomes resistance to histone deacetylase inhibitors in multiple myeloma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1015. doi:10.1158/1538-7445.AM2013-1015

Abstract 1007: Histone acetylation mediated by inhibition of Class I histone deacetylases is critical for induction of cell death in multiple myeloma cells

Histone deacetylase inhibitors (HDACi) are being evaluated as novel chemotherapeutics in combination with approved and investigational drugs for multiple myeloma (MM) therapy. Despite the rapid advancement in the use of HDACi in MM therapy, it is still not clear which HDAC needs to be inhibited to attain maximal MM cell death. HDAC6, a mediator of the proteasome pathway through its ability to deacetylate tubulin, is considered to be a critical target to promote MM cell apoptosis. However the contribution of Class I HDACs is still unclear. To determine the HDAC that needs to be inhibited in MM, cell death induced by pan-HDACi (LBH589) was compared to Class I HDACi (FK228), selective Class I and HDAC6 inhibitors (ACY-1215, ACY-738) and a specific HDAC6 inhibitor (ACY-738) utilising human myeloma cell lines (HMCL). The specificity of these HDACi was determined by characterizing the acetylation induced in histones (H2A, H2B, H3 and H4) and tubulin through flow cytometry. The histone acetylation pattern of LBH589 and FK228 were similar, ACY-1215 and ACY-738 have comparatively lesser but discernible histone acetylation, while ACY-775 did not acetylate histones. ACY-1215, ACY-738 and ACY-775 acetylate tubulin at amounts significantly higher than LBH589, while FK228 did not acetylate tubulin. To determine if there was a correlation between the pattern of acetylation and MM cell death, eight HMCLs were treated with each HDACi and proportion of cell death measured through flow cytometric enumeration of propidium iodide staining. LBH589 (50 nM) or FK228 (50 nM) induced the same amount of cell death irrespective of the HMCL used whereas ACY-1215 and ACY-738 were able to induce cell death comparable to the LBH589 and FK228 only at the highest concentration used (10 μM). Conversely, ACY-775, which induces negligible histone acetylation, was not able to induce cell death comparable to the other inhibitors except against RPMI-8226 where ACY-775 (10 μM) alone was able to cause a significant amount of cell death. Assessment of apoptosis following exposure of primary MM cells (n=8) to HDACi recapitulated the findings with the HMCL wherein ACY-775 caused the least amount of cell death. ACY-1215 and ACY-738 at higher concentrations (10 μM) were comparable to LBH589 and FK228 in all samples tested and as in the case with the HMCLs, a minority of patients (2/8) showed some cell death with ACY-775 treatment alone. These data suggest that activity against Class I HDACs is more effective than HDAC6 alone in inducing MM cell death. Specific HDAC6 inhibition does induce comparable cell death of some MM cells suggesting that in a subset of patients, inhibiting HDAC6 alone may be as efficient as Class I HDAC inhibition and identifying these patients is important. However, it is clear that in several instances histone acetylation mediated by inhibition of Class I HDAC is sufficient to induce significant MM cell death.

Citation Format: Sridurga Mithraprabhu, Tiffany Khong, Simon S. Jones, Andrew Spencer. Histone acetylation mediated by inhibition of Class I histone deacetylases is critical for induction of cell death in multiple myeloma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1007. doi:10.1158/1538-7445.AM2013-1007

Abstract 2522: The anti-kappa monoclonal antibody MDX-1097 cooperates with Lenalidomide to enhance antibody-dependent cell cytotoxicity of multiple myeloma cells

Multiple Myeloma (MM) is a malignancy of clonal plasma cells in the bone marrow with median overall survival duration of 3-5 years. Recent advances in the treatment and management of MM have improved progression free survival (PFS) and overall survival (OS) and include the use of high-dose chemotherapy, conditioned autologous stem cell transplantation, immunomodulatory drugs (IMiDs) and proteasome inhibitors. Unfortunately, despite these advances, the majority of patients will ultimately relapse and die from their disease. In thIs context novel therapeutic approaches, including the use of antibody-based therapies, are being investigated to further improve the treatment of MM. Currently the anti-kappa monoclonal antibody, MDX-1097, is being assessed as a single agent in a Phase 2 clinical trial for the treatment of kappa light-chain restricted (α-type) MM. MDX-1097 binds to kappa myeloma antigen (KMA) a tumor-specific membrane-associated protein expressed on malignant plasma cells in patients with α-type MM. Previously we have demonstrated that MDX-1097 exerts its anti-tumour effects predominantly via antibody-dependent cell cytotoxicity (ADCC) in the presence of either normal human peripheral blood mononuclear cells (PBMC) or purified natural killer (NK cells). Lenalidomide is an IMiD currently in use for the treatment of MM and has been shown to exert its anti-tumor effects both directly, via apoptotic mechanisms, and indirectly via a number of different mechanisms including the augmentation of NK-dependent cellular cytotoxicity. In this study we report that lenalidomide and MDX-1097 co-operate to promote enhanced ADCC of MM cells via 2 different mechanisms. First, in vitro pre-incubation of normal PBMC with lenalidomide (PBMC/Len) prior to co-culture with MDX-1097 treated α-type MM JJN3 cells resulted in increased ADCC compared to co-culture with control PBMC from the same donor. Second, pre-incubation of JJN3 cells with lenalidomide (JJN3/Len) resulted in increased JJN3 cell surface expression of KMA resulting in enhanced ADCC with PBMC when compared to control JJN3, with a further increment in cell killing seen when utilising the PBMC/Len and JJN3/Len combination. Finally, use of in vivo lenalidomide exposed PBMC isolated from a MM patient treated with lenalidomide demonstrated that these PBMC/Len were more effective in killing MDX-1097 treated JJN3 cells compared to PBMC obtained from the same patient prior to lenalidomide treatment. This study demonstrates that lenalidomide co-operates with MDX-1097 to enhance ADCC-induced MM cell killing and provides a rationale for the clinical evaluation of MDX-1097 and lenalidomide in the treatment of α-type MM.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2522. doi:1538-7445.AM2012-2522

Targeting HSP 90 induces apoptosis and inhibits critical survival and proliferation pathways in multiple myeloma

The second most commonly diagnosed hematologic malignancy, multiple myeloma, affects predominantly older patients (>60s) and is characterized by paraprotein in the serum or urine. Clinical manifestations include anemia, hypercalcaemia, progressive renal impairment, and osteolytic bone destruction. Despite promising new therapies, multiple myeloma eventually relapses in almost all patients. HSP are ubiquitous and highly conserved in prokaryotes and eukaryote organisms. Exposure to a broad range of stimuli results in increased HSP protein expression. These chaperone proteins are involved in protein transportation, prevent protein aggregation, and ensure correct folding of nascent and stress-accumulated misfolded proteins. In cancer, HSP expression is dysregulated, resulting in elevated expression, which promotes cancer by preventing programmed cell death and supporting autonomous cells growth, ultimately leading to resistance to heat, chemotherapy, and other stresses. Client proteins of HSP90 such as AKT, p53, MEK, STAT3, and Bcr-Abl are vital in tumor progression, including multiple myeloma, and their maturation and stability is dependent on HSP90. Therefore, inhibition of HSP90 via a HSP90 inhibitor (such as NVP-HSP990) should interrupt multiple signaling pathways essential for oncogenesis and growth in multiple myeloma. Our study showed that NVP-HSP990 triggered apoptosis in a panel of human multiple myeloma cells, induced cell-cycle arrest, PARP cleavage, downregulation of client proteins, the inability to reactivate phospho-STAT3 following exogenous IL-6 stimulation, and it synergized with azacytidine and bortezomib in cell lines and primary multiple myeloma samples. The mechanism of HSP90 inhibition in multiple myeloma warrants further evaluation.

The novel JAK inhibitor CYT387 suppresses multiple signalling pathways, prevents proliferation and induces apoptosis in phenotypically diverse myeloma cells

Janus kinases (JAKs) are involved in various signalling pathways exploited by malignant cells. In multiple myeloma (MM), the interleukin-6/JAK/signal transducers and activators of transcription (IL-6/JAK/STAT) pathway has been the focus of research for a number of years and IL-6 has an established role in MM drug resistance. JAKs therefore make a rational drug target for anti-MM therapy. CYT387 is a novel, orally bioavailable JAK1/2 inhibitor, which has recently been described. This preclinical evaluation of CYT387 for treatment of MM demonstrated that CYT387 was able to prevent IL-6-induced phosphorylation of STAT3 and greatly decrease IL-6- and insulin-like growth factor-1-induced phosphorylation of AKT and extracellular signal-regulated kinase in human myeloma cell lines (HMCL). CYT387 inhibited MM proliferation in a time- and dose-dependent manner in 6/8 HMCL, and this was not abrogated by the addition of exogenous IL-6 (3/3 HMCL). Cell cycling was inhibited with a G(2)/M accumulation of cells, and apoptosis was induced by CYT387 in all HMCL tested (3/3). CYT387 synergised in killing HMCL when used in combination with the conventional anti-MM therapies melphalan and bortezomib. Importantly, apoptosis was also induced in primary patient MM cells (n=6) with CYT387 as a single agent, and again synergy was seen when combined with conventional therapies.

Deactylase inhibition in myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are clonal haemopoietic progenitor cell disorders characterized by the proliferation of one or more of the haemopoietic lineages (myeloid, erythroid and/or megakaryocytic). The MPNs include eight haematological disorders: chronic myelogenous leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF), systemic mastocytosis (SM), chronic eosinophilic leukemia, not otherwise specified (CEL, NOS), chronic neutrophilic leukemia (CNL), and unclassifiable MPN (MPN, U). Therapeutic interventions for MPNs include the use of tyrosine kinase inhibitors (TKIs) for BCR-ABL1(+) CML and JAK2 inhibitors for PV, ET and PMF. Histone deacetylase inhibitors (HDACi) are a novel class of drugs capable of altering the acetylation status of both histone and non-histone proteins, thereby affecting a repertoire of cellular functions in neoplastic cells including proliferation, differentiation, immune responses, angiogenesis and survival. Preliminary studies indicate that HDACi when used in combination with tyrosine kinase or JAK2 inhibitors may overcome resistance to the latter agents and enhance the pro-apoptotic effects on MPN cells. This review provides a review of pre-clinical and clinical studies that have explored the use of HDACi as potential therapeutics for MPNs.

CYT997 causes apoptosis in human multiple myeloma

Multiple Myeloma (MM) is an incurable malignancy of mature plasma cells. Microtubule targeting agents (MTAs) are an established class of drug that include many conventional and some novel compounds. MTAs function by inhibiting the polymerisation or depolymerisation of microtubules (MTs) within the cell, disrupting various important cellular functions. We have investigated pre-clinically the novel tubulin polymerisation inhibitor CYT997 for the potential treatment of MM. Here we demonstrate the promising anti-myeloma activity of CYT997 as evidenced by tubulin disruption, inhibition of growth and proliferation, cell cycle arrest and most importantly apoptosis of both human myeloma cell lines (HMCLs) and primary MM cells using nanomolar drug concentrations. CYT997 also synergises with bortezomib to produce more potent anti-MM activity. These in vitro observations were validated in vivo by the ability of CYT997 to significantly prolong survival in a murine model of aggressive systemic myelomatosis. These findings provide a basis for continuing pre-clinical and clinical investigations into the anti-MM effects of CYT997.

The effect of azacitidine on interleukin-6 signaling and nuclear factor-kappaB activation and its in vitro and in vivo activity against multiple myeloma

BACKGROUND

Azacitidine is a DNA methyltransferase inhibitor and cytotoxic agent known to induce apoptosis of some cancer cells. This study evaluated the pre-clinical potential of azacitidine as a therapeutic agent for multiple myeloma.

DESIGN AND METHODS

Dose responsiveness to azacitidine was determined utilizing a panel of genetically heterogenous human multiple myeloma cell lines. Azacitidine was also tested against primary multiple myeloma cells and in the 5T33MM murine model of systemic myelomatosis. Mechanistic studies included immunoblotting of key apoptosis signaling proteins, analysis of p16 gene methylation status, and characterization of both the interleukin-6 and nuclear factor-kappaB signaling pathways following azacitidine treatment.

RESULTS

Human myeloma cell lines and primary multiple myeloma cells underwent apoptosis following exposure to clinically achievable concentrations of azacitidine (1 microM-20 microM). Similarly, azacitidine prolonged survival from 24.5 days to 32 days (p=0.001, log rank) in the 5T33MM model. At a mechanistic level azacitidine down-regulated two crucial cell survival pathways in multiple myeloma. First, it inhibited the elaboration of both interleukin-6 receptor-alpha and interleukin- 6 resulting in the reduced expression of both phospho-STAT3 and Bcl-xl. Secondly, azacitidine inhibited both nuclear factor-kappaB nuclear translocation and DNA binding in a manner independent of IkappaB. The kinetics of these azacitidine-induced responses was more consistent with protein synthesis inhibition than with either hypomethylation or another DNA-mediated effect.

CONCLUSIONS

Azacitidine rapidly induces apoptosis of multiple myeloma cells, is effective in vivo against multiple myeloma and inhibits two crucial cell survival pathways in this disease. We conclude that azacitidine demonstrates novel and highly relevant anti-myeloma effects and warrants further evaluation in a clinical context.

PKC412 demonstrates JNK-dependent activity against human multiple myeloma cells

The effect and mode of action of the protein kinase C (PKC) inhibitor PKC412 on human multiple myeloma (MM) cell lines (HMCLs) and primary MM cells was explored. We found that PKC412 induced apoptosis of HMCLs and primary MM cells with variable efficacy; however, some activity was seen against all HMCLs and primary MM cells with at least 0.5 microM PKC412. PARP cleavage and decreased PKC activity was observed in all HMCLs tested. Furthermore, PKC412 inhibited C-FOS transcription and nuclear protein expression, induced reactive oxygen species (ROS) production, and induced both sustained C-JUN expression and phosphorylation. The latter was inhibited by cotreatment with the JNK inhibitor SP600125, which similarly abrogated PKC412-induced apoptosis, suggesting that PKC412-induced apoptosis is a JNK-dependent event. PKC412 treatment secondarily induced prosurvival stress responses as evidenced by activation of NFkappaB and increased expression of the heat shock proteins HSP70 and HSP90. Consistent with the former, sequential inhibition of NFkappaB activation with bortezomib or SN50 synergistically enhanced cell killing. Our results demonstrate that PKC412 induces JNK-dependent apoptosis of HMCLs and primary MM cells and that this effect is enhanced by NFkappaB inhibition. The further evaluation of PKC412 in the treatment of MM is justified.

A study of VEGF and its receptors in two rat models of proteinuria

BACKGROUND

The high level of expression of vascular endothelial growth factor (VEGF) in normal podocyte foot processes suggests that VEGF has an important role in maintaining normal glomerular function. While altered VEGF expression occurs in many glomerular diseases, a direct role for VEGF in the pathogenesis of proteinuria has not been demonstrated.

METHODS

Expression of VEGF and its receptors (VEGFR-1 and VEGFR-2) was examined in passive Heymann nephritis (PHN) and puromycin aminonucleoside nephrosis (PAN), by immunohistochemistry, in situ hybridization, Northern and Western blotting. Inhibition of VEGF in the PAN model was performed by administration of a blocking antibody.

RESULTS

In both models, glomeruli showed upregulation of VEGF and VEGF receptors compared to control animals. VEGF mRNA was increased most significantly (5-fold) at day 5 after induction of PHN, prior to the onset of proteinuria, with persistent upregulation (3-fold) at day 21. Increased VEGF mRNA was also seen in PAN, but it was less marked. In situ hybridization and immunohistochemistry localized VEGF predominantly to podocytes. Increased expression of VEGFR-1 and VEGFR-2 protein was seen in glomerular endothelial cells of PHN and PAN rats by immunohistochemistry, as was VEGFR-2 mRNA by in situ hybridization. Upregulation of VEGFR-1 by endothelial cells was more striking in the PAN model than PHN. Administration of a blocking antibody to rats with PAN did not affect proteinuria, creatinine clearance or sodium excretion.

CONCLUSION

The expression of VEGF and its receptors is significantly increased in the PHN and PAN rat models of proteinuria suggesting a role for VEGF in the disease process. VEGF may have an important role in promoting glomerular repair in a variety of glomerular diseases.

Urinary acid-base excretion in normotensives and hypertensives of african origin

Abnormalities in acid-base regulation have previously been reported both in hypertensive humans and animals and a link between abnormalities in renal sodium handling and acid excretion may be particularly important in black hypertensives. The objectives of this study were to compare indices of urinary acid excretion (urinary pH, ammonium and titratable acid excretion) between normotensives and hypertensive people of African origin. Measurements were carried out in 86 black individuals of African origin in a case-control design (19 normotensive; 67 hypertensive). Of these, 17 normotensive and 17 patients with essential hypertension were matched for age, sex and weight. Group comparisons were carried out by unpaired t-tests or two-way analysis of variance and group values are given as means +/- s.d. Urinary pH was significantly higher in the hypertensives both in the unmatched groups and in the matched groups. In the 17 matched pairs: urinary pH in the hypertensive individuals was 6.36 +/- 0.54 and 5.84 +/- 0. 53 in the normotensives, respectively; P = 0.007. Additionally, urinary titratable acidity was significantly lower in the hypertensives than in the normotensives (25.4 +/- 13.7 vs16.7 +/- 10. 7 mmol/24 h; P = 0.047) but there were no significant differences in urinary ammonium excretion. The mechanisms for the apparent reduction in acid excretion in the hypertensives is not clear but these results highlight the possibility that hypertension in blacks is associated with abnormalities of renal sodium and hydrogen exchange with compensatory increases in renal ammonium production.

Heparin-binding epidermal growth factor-like growth factor is expressed in the adhesive lesions of experimental focal glomerular sclerosis

BACKGROUND

In this study, we attempted to determine whether heparin-binding epidermal growth factor-like growth factor (HB-EGF) was up-regulated in two chronic models of proteinuria.

METHODS

Chronic passive Heymann nephritis (PHN) and puromycin aminonucleoside (PAN) models were induced in Sprague-Dawley rats. HB-EGF expression was studied by Northern blotting, in situ hybridization, and immunohistochemistry.

RESULTS

The chronic PAN model was associated with the development of glomerular lesions of focal glomerular sclerosis (FGS), severe interstitial fibrosis, and renal failure. Lesions of FGS were seen in approximately 80% of glomeruli at all time points, with a slight increase in the number of glomeruli showing extensive adhesion between 40 and 90 days. Northern blots of whole kidney tissue showed a 3- to 5.8-fold increased expression of HB-EGF mRNA in the chronic PAN group. Increased mRNA and protein were localized by in situ hybridization and immunohistochemistry to tubules, glomerular epithelial cells (GECs), and cells of Bowman's capsule. HB-EGF mRNA and protein were strongly expressed by epithelial cells involved in the formation of the lesions of FGS. By contrast, in chronic PHN, there was a small increase in HB-EGF, and the extensive lesions of FGS did not develop despite continued, heavy proteinuria.

CONCLUSIONS

These data suggest that HB-EGF may contribute to formation of the lesions of FGS, perhaps through stimulation of abortive mitogenesis in GECs or an adhesive interaction between transmembrane HB-EGF and the exposed glomerular basement membrane.