Human iPSC-derived Committed Cardiac Progenitors Generate Cardiac Tissue Grafts in a Swine Ischemic Cardiomyopathy Model without Triggering Ventricular Arrhythmias

BACKGROUND

The adult human heart following a large myocardial infarction is unable to regenerate heart muscle and instead forms scar with the risk of progressive heart failure. Large animal studies have shown that intramyocardial injection of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) following a myocardial infarction result in cell grafts but also ventricular arrhythmias. We hypothesized that intramyocardial injection of committed cardiac progenitor cells (CCPs) derived from iPSCs, combined with cardiac fibroblast-derived extracellular matrix (cECM) to enhance cell retention will: i) form cardiomyocyte containing functional grafts, ii) be free of ventricular arrhythmias and iii) restore left ventricular contractility in a post-myocardial infarction (MI) cardiomyopathy swine model.

METHODS

hiPSCs were differentiated using bioreactors and small molecules to produce a population of committed cardiac progenitor cells (CCPs). MI was created using a coronary artery balloon occlusion and reperfusion model in Yucatan mini pigs. Four weeks later, epicardial needle injections of CCPs+cECM were performed in a small initial feasibility cohort, and then transendocardial injections (TEI) of CCPs+cECM, CCPs alone, cECM alone or vehicle control into the peri-infarct region in a larger randomized cohort. A 4-drug immunosuppression regimen was administered to prevent rejection of human CCPs. Arrhythmias were evaluated using implanted event recorders. Magnetic resonance imaging (MRI) and invasive pressure volume assessment were used to evaluate left ventricular anatomic and functional performance, including viability. Detailed histology was performed on the heart to detect human grafts.

RESULTS

A scalable biomanufacturing protocol was developed generating CCPs which can efficiently differentiate to cardiomyocytes or endothelial cells in vitro. Intramyocardial delivery of CCPs to post-MI porcine hearts resulted in engraftment and differentiation of CCPs to form ventricular cardiomyocyte rich grafts. There was no significant difference in cardiac MRI-based measured cardiac volumes or function between control, CCP and CCP+cECM groups; however, dobutamine stimulated functional reserve was improved in CCP and CCP+cECM groups. TEI delivery of CCPs with or without cECM did not result in tumors or trigger ventricular arrhythmias.

CONCLUSIONS

CCPs are a promising cell source for post-MI heart repair using clinically relevant TEI with a low risk of engraftment ventricular arrhythmias.

Tumor-selective anti-cancer effects of the synthetic alkyl phosphocholine analog CLR1404 in neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumor in children and is associated with high mortality in advanced stages. Survivors suffer from long-term treatment-related sequelae. Thus, new targeted treatment options are urgently needed. 18-(p-[(127)I] iodophenyl) octadecyl phosphocholine (CLR1404) is a novel, broadly tumor targeted small molecule drug suitable for intravenous injection with highly selective tumor uptake. As a carrier molecule for radioactive iodine, CLR1404 is in clinical trials as cancer imaging agent and radiotherapeutic drug. Chemically, CLR1404 belongs to the anti-tumor alkyl phospholipids, a class of drugs known to have intrinsic cytotoxic effects on cancer cells. Therefore, we hypothesized that CLR1404 could be a tumor-targeted anti-cancer agent for neuroblastoma, and investigated its effect in vitro and in vivo. CLR1404 was taken up by NB cells in a highly tumor-selective manner both in vitro and in vivo, confirmed by flow cytometry and PET/CT imaging of mouse flank xenografts with (124)I-CLR1404, respectively. Using flow cytometry, MTT assay, Western blotting and caspase 3/7 assay, we confirm that in vitro treatment with CLR1404 leads to robust apoptosis and cell death in multiple NB cell lines and is associated with Akt inhibition, while sparing normal cells. Treatment with CLR1404 in doses of 10 or 30 mg/kg administered by intravenous injection once weekly for 7 weeks significantly inhibited the tumor growth rate in a mouse flank xenograft model of NB (P<0.001) when compared to control cohorts, without causing drug-related hematotoxicity or other noticeable adverse effects, which was determined by serial tumor volume measurements, complete blood counts, and monitoring of animal-specific health parameters. We conclude that CLR1404 warrants clinical exploration as a novel, tumor selective anticancer agent in NB and potentially other cancers.

Abstract 1169: TPL2 kinase regulates the inflammatory milieu of the myeloma niche

Early-stage myeloma tumor cells are critically dependent on paracrine cytokine support originating from their bone marrow microenvironment whereas advanced-stage myeloma tumor cells may elaborate autocrine cytokine production mechanisms and/or cell-autonomous mutations in critical downstream signaling pathways (e.g., NFκB pathway). However, the molecular mechanisms underpinning the paracrine network in myeloma are unclear. The pro-inflammatory cytokine IL-1β has emerged as a major link between inflammation and cancer and has been validated as a therapeutic target in high-risk monoclonal gammopathy, the precursor to myeloma, as well as early-stage myeloma. To determine the source of IL-1β production in early-stage myeloma we analyzed paired purified cell fractions obtained from each of 5 patients at diagnosis: CD138+ tumor cells, CD14+ bone marrow-resident monocyte/macrophages as well as bone marrow-derived stromal/mesenchymal cells (BM-MSC). We found that in all cases, monocytes/macrophages were the predominant IL-1β synthesizer cell type in the myeloma microenvironment. Cytokine production by activated macrophages is controlled by the MAP3 kinase, TPL2 (Cot, MAP3K8). We have previously detected constitutive activation of TPL2-regulated signaling pathways in human myeloma-associated macrophages but its precise functional consequences have been unclear. To dissect the relevant mechanisms, we ablated Tpl2 in the genetically-engineered myeloma in vivo model, Vκ*MYC. Vκ*MYC animals activate MYC sporadically in B lymphocytes participating in germinal center reactions and develop a disease analogous to human multiple myeloma with production of paraprotein (monoclonal immunoglobulin), plasma cell infiltration of the bone marrow as well as end-organ damage (“myeloma kidney”, osteolytic lesions). Vκ*MYC+/Tpl2-null animals developed myeloma with a significantly prolonged latency and the disease burden was lower at all timepoints tested compared to controls. Analysis of monocytic cells from myeloma lesions showed that loss of Tpl2 did not result in macrophage repolarization to an unopposed M1 (tumoricidal/cytotoxic) phenotype. Instead, Tpl2-null myeloma-associated monocytes/macrophages exhibited severe defects in production of inflammatory cytokines, predominantly IL-1β, but also IL-6. Tpl2 loss did not have discernible impacts on tumor cell-autonomous growth and survival. Our results suggest that monocytes/macrophages and TPL2 kinase activity play a central role in orchestrating the inflammatory milieu of the myeloma niche. Disruption of the myeloma cytokine network through pharmacologic TPL2 kinase inhibition could provide novel therapeutic opportunity by interfering with the co-ordinate regulation of key pro-myeloma inflammatory cytokines through a targeted approach.

Citation Format: Chelsea Hope, Samuel J. Ollar, Erika Heninger, Jeffrey L. Jensen, Ellen Hebron, Jaehyup Kim, Ioanna Maroulakou, Shigeki Miyamoto, Natalie Callander, Peiman Hematti, Marta Chesi, P. Leif Bergsagel, Fotis Asimakopoulos. TPL2 kinase regulates the inflammatory milieu of the myeloma niche. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1169. doi:10.1158/1538-7445.AM2014-1169

TPL2 kinase regulates the inflammatory milieu of the myeloma niche

Targeted modulation of microenvironmental regulatory pathways may be essential to control myeloma and other genetically/clonally heterogeneous cancers. Here we report that human myeloma-associated monocytes/macrophages (MAM), but not myeloma plasma cells, constitute the predominant source of interleukin-1β (IL-1β), IL-10, and tumor necrosis factor-α at diagnosis, whereas IL-6 originates from stromal cells and macrophages. To dissect MAM activation/cytokine pathways, we analyzed Toll-like receptor (TLR) expression in human myeloma CD14(+) cells. We observed coregulation of TLR2 and TLR6 expression correlating with local processing of versican, a proteoglycan TLR2/6 agonist linked to carcinoma progression. Versican has not been mechanistically implicated in myeloma pathogenesis. We hypothesized that the most readily accessible target in the versican-TLR2/6 pathway would be the mitogen-activated protein 3 (MAP3) kinase, TPL2 (Cot/MAP3K8). Ablation of Tpl2 in the genetically engineered in vivo myeloma model, Vκ*MYC, led to prolonged disease latency associated with plasma cell growth defect. Tpl2 loss abrogated the "inflammatory switch" in MAM within nascent myeloma lesions and licensed macrophage repolarization in established tumors. MYC activation/expression in plasma cells was independent of Tpl2 activity. Pharmacologic TPL2 inhibition in human monocytes led to dose-dependent attenuation of IL-1β induction/secretion in response to TLR2 stimulation. Our results highlight a TLR2/6-dependent TPL2 pathway as novel therapeutic target acting nonautonomously through macrophages to control myeloma progression.

Macrophages in multiple myeloma: emerging concepts and therapeutic implications

Multiple myeloma, a clonal plasma cell malignancy, has long provided a prototypic model to study regulatory interactions between malignant cells and their microenvironment. Myeloma-associated macrophages have historically received limited scrutiny, but recent work points to central and non-redundant roles in myeloma niche homeostasis. The evidence supports a paradigm of complex, dynamic and often mutable interactions between macrophages and other cellular constituents of the niche. We and others have shown that macrophages support myeloma cell growth, viability and drug resistance through both contact-mediated and non-contact-mediated mechanisms. These tumor-beneficial roles have evolved in opposition to, or in parallel with, intrinsic pro-inflammatory and tumoricidal properties. Thus, simple blockade of protective "don't eat me" signals on the surface of myeloma cells leads to macrophage-mediated myeloma cell killing. Macrophages also enhance the tumor-supportive role of mesenchymal stem/stromal cells (MSCs) in the niche: importantly, this interaction is bidirectional, producing a distinct state of macrophage polarization that we termed "MSC-educated macrophages." The intriguing pattern of cross-talk between macrophages, MSCs and tumor cells highlights the myeloma niche as a dynamic multi-cellular structure. Targeted reprogramming of these interactions harbors significant untapped therapeutic potential, particularly in the setting of minimal residual disease, the main obstacle toward a cure.

MAP3K8 kinase regulates myeloma growth by cell-autonomous and non-autonomous mechanisms involving myeloma-associated monocytes/macrophages

Benefit from cytotoxic therapy in myeloma may be limited by the persistence of residual tumour cells within protective niches. We have previously shown that monocytes/macrophages acquire a proinflammatory transcriptional profile in the myeloma microenvironment. Here we report constitutive activation of MAP3K8 kinase-dependent pathways that regulate the magnitude and extent of inflammatory activity of monocytes/macrophages within myeloma niches. In myeloma tumour cells, MAP3K8 acts as mitogen-induced MAP3K in mitosis and is required for TNFα-mediated ERK activation. Pharmacological MAP3K8 inhibition results in dose-dependent, tumour cell-autonomous apoptosis despite contact with primary stroma. MAP3K8 blockade may disrupt crucial macrophage-tumour cell interactions within myeloma niches.