Comprehensive Single-Cell Immune Profiling Defines the Patient Multiple Myeloma Microenvironment Following Oncolytic Virus Therapy in a Phase Ib Trial

PURPOSE

Our preclinical studies showed that the oncolytic reovirus formulation pelareorep (PELA) has significant immunomodulatory anti-myeloma activity. We conducted an investigator-initiated clinical trial to evaluate PELA in combination with dexamethasone (Dex) and bortezomib (BZ) and define the tumor immune microenvironment (TiME) in patients with multiple myeloma treated with this regimen.

PATIENTS AND METHODS

Patients with relapsed/refractory multiple myeloma (n = 14) were enrolled in a phase Ib clinical trial (ClinicalTrials.gov: NCT02514382) of three escalating PELA doses administered on Days 1, 2, 8, 9, 15, and 16. Patients received 40 mg Dex and 1.5 mg/m2 BZ on Days 1, 8, and 15. Cycles were repeated every 28 days. Pre- and posttreatment bone marrow specimens (IHC, n = 9; imaging mass cytometry, n = 6) and peripheral blood samples were collected for analysis (flow cytometry, n = 5; T-cell receptor clonality, n = 7; cytokine assay, n = 7).

RESULTS

PELA/BZ/Dex was well-tolerated in all patients. Treatment-emergent toxicities were transient, and no dose-limiting toxicities occurred. Six (55%) of 11 response-evaluable patients showed decreased paraprotein. Treatment increased T and natural killer cell activation, inflammatory cytokine release, and programmed death-ligand 1 expression in bone marrow. Compared with nonresponders, responders had higher reovirus protein levels, increased cytotoxic T-cell infiltration posttreatment, cytotoxic T cells in significantly closer proximity to multiple myeloma cells, and larger populations of a novel immune-primed multiple myeloma phenotype (CD138+ IDO1+HLA-ABCHigh), indicating immunomodulation.

CONCLUSIONS

PELA/BZ/Dex is well-tolerated and associated with anti-multiple myeloma activity in a subset of responding patients, characterized by immune reprogramming and TiME changes, warranting further investigation of PELA as an immunomodulator.

Abstract 6354: Using imaging mass cytometry to visualize the multiple myeloma tumor microenvironment post immune priming

Background: Multiple myeloma (MM) is an incurable cancer characterized by clonal plasma cell proliferation in the bone marrow, accounting for approximately 10% of all hematologic malignancies. Recently, patients with relapsed or refractory disease have been treated with a combination of the oncolytic reovirus Pelareorep, bortezomib, and dexamethasone, which was well-tolerated and led to prolonged progression free survival of over 3 years in a subset of patients. To understand the complex tumor immune microenvironment (TiME) and immune responses in patients before and after this treatment, we used imaging mass cytometry (IMC) to perform single cell, highly multiplexed, analysis of these patients’ bone marrow samples.

Methods: We comprehensively characterized the changes in the MM TIME in pre and post bone marrow biopsy specimens taken from patients treated on a Phase 1b study with a combination of Pelareorep, bortezomib, and dexamethasone. For analysis with IMC, a marker panel of 35 antibodies was assembled to interrogate the various immune subsets of the bone marrow biopsies; each of these antibodies were conjugated to a unique metal isotope. After validation, the antibody cocktail was used to stain the biopsies. Pixel-based classification was performed in Ilastik to generate cell probability masks and processed in Cellprofiler. PhenoGraph was run in HistoCAT to identify the unique phenotypes. Rstudio was used for t-stochastic neighborhood embedding (tSNE) plot generation, and nearest neighbor analyses. ImaCytE was used for image visualization and spatial analysis.

Results: Initial visualization of the raw, unsegmented data showed increased infiltration of natural killer cells and T cells in the post-treatment samples when compared against the pre-treatment samples. These changes correlated with immunohistochemical findings, clinical response to treatment, and changes in T cell clonality. After segmentation, the marker expression heatmaps for each of the clusters identified by PhenoGraph and the further subphenotyping in Rstudio showed complex ecosystems of cell-cell interactions. Nearest neighbor spatial analysis of the post-treatment samples revealed that NK cells (NKG2D+ and NKG2A+ subsets), monocytes (CD14+), macrophages (CD68+), cytotoxic T cells (CD3+, CD8+), and T helper cells (CD3+, CD4+) were significantly closer to the Pelareorep-primed MM than the non-primed MM. Further analysis in ImaCytE highlighted specific instances of these immune neighborhoods.

Conclusions: IMC allows us to analyze the potent immune response and cellular interactions in the tumor microenvironment in multiple myeloma treated with Pelareorep and Bortezomib. Characterization of these complex interactions allows for a deeper understanding of the key mechanisms of action of these treatments and planning of future combination studies.

Citation Format: Julian Olea, Kaijin Wu, Anthony Colombo, Claudia Villa Celi, Thomas Heineman, Matt Coffey, Steffan T. Nawrocki, Akil Merchant, Kevin R. Kelly. Using imaging mass cytometry to visualize the multiple myeloma tumor microenvironment post immune priming [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 6354.

Early graft thrombosis after endovascular aortic aneurysm repair with aortouni-iliac endografts

Endovascular repair of aortic aneurysm has become a viable treatment option in selected patients. However, despite the minimally invasive nature ot this treatment a significant incidence of vascular complications has been reported. Here, we report two cases of acute limbs ischemia due to endograft thrombosis in patients treated with aortouni-iliac devices and we review the etiologic factors related with these events and the treatment options. We suggest that the presence of atherosclerotic plaques within the outflow arteries and coexistent infrainguinal arterial occlusive disease (poor runoff) is an underestimated factor in the risk of graft thrombosis, especially in patients treated with aortouni-iliac devices and we advocate the use in the early follow-up surveillance after endovascular repair of aortic aneurysm of noninvasive test such duplex scanning, segmental pressures and ankle-brachial indices to asses the presence or progress of coexistent occlusive disease. We also suggest that some adverse outcomes ascribed to device failure might be more properly charged to inappropriate patient selection.

Intestinal T-cell lymphoma associated with celiac disease masked by cavernous lymphangioma

We present the case of a patient admitted to our emergency ward with a clinical setting of acute abdominal pain and a history of cavernous lymphangioma, diagnosed in another center by exploratory lapartomy. The patient presented complete analysis including serology tests, as well as an abdominal CT scan that revealed multiple large size retroperitoneal cysts. In view of the clinical symptomatology and results of the tests, a second CT scan was carried out upon admission. As a result of the findings obtained, a second exploratory laparotomy was carried out in which intestinal resection of the perforated jejunal loop and largest cysts was performed. Pathological anatomy diagnosed an intestinal lymphoma associated with enteropathy and abdominal cysts compatible with cavernous lymphangioma. In this work we describe both pathologies, the most characteristic aspects are analyzed and the etiology and possible relation between both entities is discussed.

Comparison between two warm ischemic models in experimental liver transplantation in pigs

BACKGROUND

Experimental models of warm ischemia in liver transplantation have been employed to study the mechanisms and treatment of ischemia reperfusion injury.

METHODS

We compared a control group without (group A, n = 10) versus two models of warm ischemia of liver transplants in pigs: namely, occlusion of the hepatic artery and portal vein for 30 minutes (group B, n = 23) and extraction of the liver 60 minutes after cardiac arrest (group C, n = 5). Liver function tests, coagulation studies, and liver biopsies were performed during the first 24 hours post-liver transplant.

RESULTS

Clamping of the hepatic vasculature in group B produced a significant liver injury compared with the control group: elevation of the ALT and an abnormal 1-hour post-revascularization biopsy similar to that observed in the cardiac arrest group C. The transaminase levels were lower among group A animals (P <.05). But the hepatic synthetic functions as reflected in the protrombin time (PT) were not affected in group B versus group A. The alteration in PT with respect to the initial value was similar among group A and group B animals, which were significantly less than that in group C (P <.05).

CONCLUSIONS

Occlusion of the hepatic artery and portal vein, a simple surgical maneuver, causes moderate damage to a liver graft but less alteration of hepatic synthetic function. Clamping of the hepatic vasculture obtains more long-term survivors after OLT than cardiac arrest.

Sulfonylurea effects on acid and pepsinogen secretion in isolated rabbit gastric glands

The influence of different sulfonylureas on the rate of acid and pepsinogen secretion was studied in isolated rabbit gastric glands. Neither tolbutamide (10-500 microM), chlorpropamide (10-500 microM), glibenclamide (1-50 microM) nor glipizide (1-50 microM) exerted a secretory effect. In contrast, gliquidone caused a marked and dose-dependent stimulation of acid production in gastric glands incubated under basal conditions and potentiated the stimulatory effect of both histamine and carbachol. Gliquidone also increased the rate of pepsinogen release in gastric glands incubated either under basal conditions or in the presence of cholecystokinin-octapeptide or isoproterenol. The secretory effects of gliquidone were associated with a significant increase in the glandular content of cyclic AMP, caused by a competitive inhibition of low-Km cyclic AMP phosphodiesterase. Our results indicate that, among the assayed sulfonylureas, only gliquidone, in the micromolar range, stimulates acid and pepsinogen secretion through a cyclic AMP-dependent mechanism.

Effect of starvation on lipoprotein lipase activity in different tissues during gestation in the rat

This study was addressed to determine whether the tissue-specific LPL activity response to fasting differs between nonpregnant and pregnant rats over the course of pregnancy. Fed and 24-h fasted rats were studied at days 12, 15 or 20 of gestation and were compared to virgin controls. In fed rats at days 15 and 20 of gestation LPL activity decreased in lumbar adipose tissue and the heart and liver, and increased in mammary gland tissue. Fasting decreased LPL activity in lumbar adipose tissue in 12 day pregnant and virgin rats and in mammary gland tissue in pregnant rats at 15 and 20 days of gestation and in virgin rats, whereas it increased LPL activity in heart tissue in rats at day 15 and 20 and in liver at day 20 of gestation. Plasma triacylglycerols were higher in 20 day pregnant rats than in the other groups when fed and this difference was even more noticeable in the fasting condition where the plasma beta-hydroxybutyrate level also reached the highest value in the 20 day pregnant rats. Since tissue LPL activity controls the hydrolysis and uptake of circulating triacylgylcerols, the present results indicate that in fed rats after the 15th day of gestation circulating triacylglycerols are preferentially taken up by the mammary gland instead of being taken up by adipose tissue and heart. However, after fasting, circulating triacylglycerols are driven to the heart and liver in the late pregnant rat, and become a major source for fatty acid oxidation, an effect that seems to be specially evident in the liver of the 20 day pregnant rat where there is an intense increase in LPL activity and the triacylglycerols become preferential substrates for ketone body production.

Fructose 2,6-bisphosphate levels and modulation of glycolysis by histamine, cholecystokinin, and forskolin in isolated rabbit gastric glands

In isolated rabbit gastric glands incubated in the presence of 1 mmol/L glucose, the content of fructose 2,6-bisphosphate (F-2,6-P2) was 5.7 +/- 0.5 pmol/mg dry weight. This value was progressively incremented by increasing glucose concentration in the incubation medium, and was almost doubled at 10 mmol/L glucose. Under these conditions, a close correlation could be established between the levels of F-2,6-P2 and the rate of L-lactate formation (r = .98; P less than .05). Both histamine (0.1 mmol/L) and cholecystokinin octapeptide (CCK-OCT; 0.1 mumol/L) increased L-lactate production, without significant changes in either F-2,6-P2 concentration or the amount of 6-phosphofructo-2-kinase in active form. In contrast, forskolin, which markedly increased the glandular content of cyclic adenosine monophosphate (cAMP), partially blocked glucose consumption and caused a significant reduction in both F-2,6-P2 levels and the proportion of 6-phosphofructo-2-kinase in active form. Furthermore, forskolin partially blocked the rate of glucose uptake by isolated gastric glands. Our results suggest a regulatory role of F-2,6-P2 in the control of the glycolytic flux in response to glucose, but not in its response to histamine or CCK-OCT.

The effect of ligand on the kinetics of the sulfhydryl groups of human hemoglobin with p-mercuribenzoate

The rate of reaction of PMB with the masked sulfhydryls of human hemoglobin derivatives correlates well with the extent of dissociation for various ligands. It is suggested that the alpha1beta2 dimer of hemoglobin participates in the slow step of the reaction with PMB.