Undifferentiated carcinoma with osteoclastic giant cells of pancreas: Case report and brief literature review

Undifferentiated carcinoma with osteoclastic giant cells is a distinctive rare neoplasm involving pancreas and rarely bile ducts. This neoplasm shows characteristic histologic features with variable admixture of mononuclear histiocytic cells, non- neoplastic osteoclastic giant cells and neoplastic mononuclear cell component. Though, this tumor has been shown to share genetic alterations with pancreatic ductal adenocarcinoma, clinically, it behaves unpredictably with a substantial proportion of patient showing prolonged survival period. We present a case of this rare pancreatic tumour with brief literature review discussing the key pathologic features, immunophenotype, genetic profile and clinical behavior. Undifferentiated carcinoma with osteoclastic giant cells is a rare neoplasm in pancreas which is believed to be of epithelial origin and shares genetic aberrations with ductal adenocarcinoma. Despite this, these tumours have better prognosis with prolonged survival period.

Therapeutic Targeting of Mertk and BCL-2 in T-Cell and Early T-Precursor Acute Lymphoblastic Leukemia

Introduction T-cell acute lymphoblastic leukemia (T-ALL) accounts for 15% of childhood ALL and is associated with inferior outcomes relative to B-cell ALL. Early T-precursor ALL (ETP-ALL) is a subset of T-ALL characterized by an immature T cell phenotype, resistance to therapy, and high rates of induction failure. MERTK receptor tyrosine kinase is ectopically expressed in 40-50% of T-ALLs, particularly those with an immature T cell phenotype, suggesting a role in ETP-ALL. Inhibition of MERTK using shRNA delayed leukemia progression and prolonged survival in a T-ALL xenograft model, implicating MERTK as a therapeutic target. MRX-2843 is an orally available dual MERTK/FLT3 inhibitor currently in phase I clinical trials. The anti-apoptotic protein B-cell lymphoma-2 (BCL-2) is specifically expressed in immature T cell precursors, is preferentially expressed in ETP-ALL compared to other T-ALLs, is essential for ETP-ALL cell survival, and is regulated downstream of MERTK in acute leukemia cells. Thus, combination therapies targeting these two proteins may be particularly effective to treat ETP-ALL. Methods Loucy and PEER ETP-ALL cell lines were cultured with vehicle or MRX-2843. Phosphorylated and total MERTK were assessed by immunoblot. Relative cell numbers were measured using Presto Blue reagent. Cells were stained with PoPro-1-iodide and propidium iodide and apoptotic and dead cells were quantitated by flow cytometry. T-ALL patient samples were cultured with UNC2025, a close analogue of MRX-2843, and relative cell numbers were assessed using MTS reagent. Orthotopic xenografts were established in NSG or NSGS mice using luciferase-expressing Jurkat cells (T-ALL), luciferase-expressing Loucy cells (ETP-ALL) or an ETP-ALL patient sample and leukemia burden was monitored by bioluminescence imaging or flow cytometry. MRX-2843 (65 mg/kg or 75 mg/kg) or saline vehicle were administered orally once daily. Differences in disease burden were assessed with the Mann-Whitney-U test or one-way ANOVA. Survival was determined by Kaplan-Meier analysis. Loucy and PEER cells were plated and screened in quadruplicate against >150 pairwise combinations of MRX-2843 and the BCL-2 inhibitor venetoclax in a high-throughput format. Synergy was calculated using the response additivity model. Results Treatment with MRX-2843 mediated a dose-dependent decrease in phosphorylated MERTK, inhibited expansion of ETP-ALL cells, and induced cell death in vitro. Fifty-four percent (21/39) of primary T-ALL patient samples were sensitive to UNC2025 with an IC 50≤550 nM, including 2/5 (40%) pediatric samples and 10/19 (53%) adolescent/young adult samples. Treatment with MRX-2843 significantly reduced leukemia burden in cell line-derived T-ALL and ETP-ALL xenograft models and prolonged survival by 50% and 13% in the T-ALL (n=10, p<0.0001) and ETP-ALL (n=10, p=0.0136) models, respectively. Similarly, in a patient-derived ETP-ALL xenograft model, treatment with MRX-2843 reduced peripheral blood disease burden by 83% and spleen weight by 64% compared to vehicle-treated mice (n=8, p<0.001) and prolonged survival by 41% (n=8, p=0.0016). MRX-2843 mediated anti-leukemia activity in combination with venetoclax and a dose ratio of 1:20 MRX-2843:venetoclax provided optimal synergy in Loucy and PEER ETP-ALL cells in vitro (Figure 1). Conclusions MRX-2843 has therapeutic activity in ETP-ALL cell culture and xenograft models and over half of T-ALL patient samples were sensitive to MERTK/FLT3 inhibition. MRX-2843 also mediated synergistic anti-leukemia activity against ETP-ALL cells in combination with venetoclax, with an optimal molar ratio of 1:20. These data demonstrate the therapeutic potential of MRX-2843 in patients with T-ALL, suggest that MRX-2843 may be particularly active alone and in combination with venetoclax in the ETP-ALL subset, and provide rationale for clinical testing of MRX-2843, with the ultimate goal to progress to trials evaluating MRX-2843 in combination with other agents. Toward this end, MRX-2843 monotherapy will be tested in patients with relapsed leukemia in an upcoming clinical trial (NCT04872478). Figure 1 Figure 1. Disclosures Wang: Meryx: Other: Equity ownership; University of North Carolina: Patents & Royalties. Frye: University of North Carolina: Patents & Royalties; Meryx: Membership on an entity's Board of Directors or advisory committees, Other: Equity ownership. Earp: Meryx: Membership on an entity's Board of Directors or advisory committees, Other: Equity ownership. Tyner: Petra: Research Funding; Incyte: Research Funding; Takeda: Research Funding; Janssen: Research Funding; Astrazeneca: Research Funding; Array: Research Funding; Constellation: Research Funding; Seattle Genetics: Research Funding; Schrodinger: Research Funding; Genentech: Research Funding; Gilead: Research Funding; Agios: Research Funding. DeRyckere: Meryx: Other: Equity ownership. Graham: Meryx: Membership on an entity's Board of Directors or advisory committees, Other: Equity ownership.

Mcm2 Deficiency Leads to Bone Marrow Failure and Lymphoid Malignancies Dependent on Age and Genetic Background

DNA replicative stress is associated with malignant transformation. Mini-chromosome maintenance 2 (hereafter Mcm2) is a component of the DNA helicase complex that plays a pivotal role in DNA replication. The Mcm2-7 complex is loaded onto chromatin during the G1-phase of the cell cycle and is required for initiation of DNA replication in the subsequent S-phase. Mice with a Cre cassette inserted into the 3'UTR of the Mcm2 gene (designated Mcm2 Cre) were generated as a tool to assess Mcm2 expression. Unexpectedly, mice with two copies of this allele (Mcm2 Cre/Cre) had decreased expression of Mcm2 protein (~20-30% of the wild type (WT) expression level), likely due to decreased RNA stability caused by insertion of the Cre cassette. Surprisingly, all Mcm2 Cre/Cre mice developed a lethal pre-T lymphoblastic leukemia/lymphoma (pre-T LBL) with a median survival of under 3 months. These pre-T LBL were characterized by 10-20 interstitial deletions of approximately 50-1000 kb, often involving genes known to be mutated or deleted in human pre-T LBL, such as Notch1, Pten, Tcf3, and Cdkn2a. Thus, Mcm2 Cre/Cre mice display a novel mutator/deletor phenotype that results in malignant transformation. Although the Mcm2 hypomorph is a germline defect, the malignancies we identified in Mcm2 Cre/Cre mice were restricted to thymocytes. We hypothesized that Mcm2 Cre/Cre mice were susceptible to non-thymocyte malignancies, but due to the early onset of pre-T LBL (within 4 months of age), these putative non-thymocyte malignancies did not have an opportunity to develop. We transplanted Mcm2 Cre/Cre Lin-Sca-1+Kit+ (LSK) hematopoietic stem/progenitor cells (HSPCs) isolated from 5-week-old Mcm2 Cre/Cre bone marrow into WT recipients, which led to marked anemia and thrombocytopenia without evidence of leukemic transformation at 5 months post-transplant. Consistent with this finding, bone marrow from 5-week-old Mcm2 Cre/Cre mice also showed decreased LSK and Lin-Sca-1-Kit+ (LK) cells compared to WT mice, suggesting that the bone marrow failure was uncovered by the more prolonged survival of Mcm2 Cre/Cre LSK recipients vs. non-transplanted Mcm2 Cre/Cre mice (5 mos. vs. <3 mos.) . As an alternate approach to preventing pre-T LBL, we crossed the Mcm2 Cre allele onto a nude (nu/nu) background, as nude mice lack thymic epithelial cells, preventing T cell development. Mcm2 Cre/Cre nu/nu mice had markedly prolonged survival compared to Mcm2 Cre/Cre (median 296.5 vs. 80.5 days, respectively; P < 0.0001). Most of the Mcm2 Cre/Cre nu/nu mice succumbed to B-cell precursor acute lymphoblastic leukemia (BCP-ALL) within 10 months of life. To determine whether Mcm2 Cre/Cre nu/nu would develop acute myeloid leukemia (AML) if placed on myeloid leukemia sensitized background, we crossed Mcm2 Cre/Cre nu/nu mice with mice expressing a NUP98-PHF23 (NP23) transgene, as the NP23 fusion gene predisposes mice to develop AML. All Mcm2 Cre/Cre nu/nu NP23 mice died within 5 months of age, primarily due to BCP-ALL. Sparse whole-genome sequencing (WGS) was used to detect copy number aberration (CNA), and we identified recurrent deletions of 100-1000 kb that involved genes known or suspected to be involved in BCP-ALL, including Pax5, Ikzf3, Il7r, and Bcor. Whole-exome sequencing identified recurrent mutations, Jak1/Jak3, Ptpn11, and Kras. In an effort to identify 100-1000 kb interstitial deletions in non-hematopoietic tissue, we used sparse WGS to identify CNA in single-cell cloned mouse embryo fibroblasts (MEF) from Mcm2 Cre/Cre, Mcm2 Cre/Wt, and Mcm2 Wt/Wt mice. Very few CNAs were identified in any of the MEFs. We conclude that this unique deletor phenotype found in Mcm2 Cre/Cre mice is a powerful tool for the identification of tumor suppressor genes in lymphoid leukemia, and that B- and T- lymphocytes are uniquely susceptible to this deletor phenotype. Disclosures No relevant conflicts of interest to declare.

CSIG-17. IMMUNE MODULATORY ROLE OF TYPE I INTERFERON IN SYNGENEIC MOUSE GLIOMA MODELS

Glioblastoma is characterized by a poor prognosis and a challenging phenotype for drug development. Although multimodal treatment, including surgery, radio- and chemotherapy is applied, the overall survival remains just above one year. Numerous clinical trials have studied targeted therapies against commonly deregulated pathways, but an efficient targeted drug is yet to be discovered. Likewise, immunotherapy has not been shown to be active. A subset of glioma tumor cells demonstrates stem-like properties; these cells are commonly referred to as glioma initiating cells (GIC). These types of cells are pluripotent and can by definition initiate and recapitulate glioma growth in experimental animals in vivo. Furthermore, these cells are often resistant to conventional therapies. Interferon β (IFN-β) is an immunomodulatory molecule with anti-cancer properties. We have previously shown that IFN-β greatly reduces sphere-formation capability of GIC. It was also confirmed that IFN-β sensitized resistant GIC to irradiation or the chemotherapeutic agent, temozolomide (TMZ). IFN-β treatment significantly prolonged survival in a xenograft model with GIC cells. In the current project, we want to use syngeneic mouse models to study the immunomodulatory effects of type I IFNs. Preliminary results indicate that abrogation of IFN signalling in tumor cells by CRISPR/Cas9 technology prolonged survival in mice only in cell lines which have substantial baseline autocrine IFN signalling. On the contrary, we did not observe a difference in survival when wild-type tumor cells were implanted in either IFNAR1 deficient or proficient hosts. Flow cytometry analysis will elucidate changes in immune cell recruitment and infiltration upon IFN signalling disruption. Moreover, we explore different treatments in combination with IFN-β as there are indications that TMZ or radiotherapy can have synergistic effects with stimulation of interferon type I signalling.

P.159 Association Between Extent of Resection and Survival in Pediatric Patients with High-Grade Glioma: A Systematic Review and Meta-Analysis

Background: While pediatric high-grade glioma (HGG) has a poor prognosis, the relationship between extent of resection (EOR), tumor location, and survival remains unclear. Our aim is to determine whether gross-total resection (GTR) is associated with prolonged survival relative to subtotal resection (STR) and biopsy. Methods: PubMed, Ovid EBM Reviews, Embase, and MEDLINE were systematically reviewed. Eligible articles were included for study-level and individual-patient data (IPD) meta-analysis. Difference by study-level and IPD characteristics were estimated using subgroup meta-analysis and meta-regression. PRISMA guidelines were followed. Results: In total, 33 studies were included. Study-level meta-analysis found GTR conferred decreased mortality relative to STR at 1 year (RR=0.73, 95%CI=0.59-0.89) and 2 years (RR=0.74, 95%CI=0.64-0.84). STR did not demonstrate survival advantages compared to biopsy at 1 year (RR=0.81, 95%CI=0.64-1.03), but showed decreased mortality at 2 years (RR=0.90, 95%CI=0.82-0.99). IPD meta-analysis comprised 186 patients, and indicated that STR (HR=2.61, 95%CI=1.56-4.38) and biopsy (HR=2.83, 95%CI=1.54-5.19) had shortened survival relative to GTR, with no differences between STR and biopsy (HR=0.93, 95%CI=0.55-1.56). In subgroup analysis, GTR was associated with prolonged survival for hemispheric tumors (HR=0.16, 95%CI=0.07-0.36) Conclusions: Among pediatric patients with HGGs, GTR was independently associated with better overall survival compared to STR and biopsy, especially in patients with hemispheric tumors.

763 Intratumoral delivery of high potency STING agonists modulates the immunosuppressive myeloid compartment and induces curative responses in checkpoint-refractory glioblastoma models

BackgroundGlioblastoma is an aggressive primary brain malignancy that is characterized by a highly suppressive tumor microenvironment, including myeloid-derived suppressor cells, tumor-associated macrophages, and brain-resident microglia, but lacking significant T cell infiltration.1 2 This phenotype is reflected in the recently developed QKi-/- Pten-/- P53-/- (QPP) tumor model,3 which we show is resistant to PD1 or CTLA-4 blockade, but sensitive to agonists of the innate immune sensor Stimulator of Interferon Genes (STING). We have previously shown that agonists of the innate dsDNA-sensing cGAS-STING pathway are capable of proinflammatory repolarization in in vitro models of suppressive myeloid cells, although their function in the context of the Glioblastoma myeloid compartment in vivo remains poorly understood.4MethodsWe utilized the synthetic cyclic di-nucleotide STING agonists IACS-8803 (8803) and ML-RR-S2-CDA (MLRR) to assess survival and tumor immune infiltrate functional reprogramming in two orthotopic transplantable human and murine Glioblastoma tumor models, U87 and the recently developed QPP8 (Qki-/- Pten-/- P53-/-). Using in vitro models of M2-polarized microglia, we investigated the ability of natural (2'3'-cGAMP) and synthetic (MLRR and 8803) STING agonists to reverse immunosuppressive microglial polarization.ResultsWe found that intratumoral delivery of STING agonists significantly prolonged survival in the murine QPP8 orthotopic Glioblastoma tumor model, in contrast to checkpoint blockade which had no benefit on survival. In huNOG-EXL mice engrafted with human hematopoietic stem cells implanted with orthotopic U87 Glioblastoma, intratumoral delivery of STING agonists significantly prolonged survival and reduced expression of CD163 and CD206 on human tumor-infiltrating myeloid populations. Preliminary data suggests that in vitro suppressively-polarized microglia reduce expression of M2 functional markers, and increase expression of iNOS, PD-L1, CD80, and CD86 in a STING agonist potency-dependent manner.ConclusionsWe found that STING agonists can induce curative responses in checkpoint-refractory murine Glioblastoma models and mediate significant extension of survival in a humanized mouse U87 xenograft setting. This prolonged survival is associated with a decrease in immunosuppressive M2 functional markers in human tumor infiltrating myeloid populations. Additionally, M2-polarized microglia demonstrated a reduction in M2 functional markers and upregulation of proinflammatory M1 markers following treatment with STING agonists. Together these results indicate that delivery of STING agonists can induce proinflammatory repolarization of the Glioblastoma myeloid stroma, including both infiltrating myeloid populations and brain-resident microglia, to drive prolonged survival in refractory models of Glioblastoma.ReferencesGabrusiewicz K, Rodriguez B, Wei J, et al. Glioblastoma-infiltrated innate immune cells resemble M0 macrophage phenotype. JCI Insight 2016;1(2).Quail DF, Joyce JA. The microenvironmental landscape of brain tumors. Cancer Cell 2017;31(3):326–41.Shingu T, Ho AL, Yuan L, et al. Qki deficiency maintains stemness of glioma stem cells in suboptimal environment by downregulating endolysosomal degradation. Nat Genet 2017;49(1):75–86.Ager C, Boda A, Rajapakshe K, et al. (2021) “High potency STING agonists engage unique myeloid pathways to reverse pancreatic cancer immune privilege. JITC (in press)Ethics ApprovalAll experiments were conducted according to protocols approved by the University of Texas MD Anderson Cancer Center Institutional Animal Care and Use Committee.

Racial/ethnic Disparities on Inflammation and Response to Methylprednisolone in Severe Covid-19 Pneumonia

BACKGROUNDRacial/Ethnic minorities are at higher risk for Severe COVID-19. This may be related to social determinants that lead to chronic inflammatory states. The aims of the study were to determine if there are racial/ethnic differences between the inflammatory markers of survivors and non-survivors and if there was a dose dependent association of methylprednisolone to in hospital survival. METHODSThis was a secondary analysis of a retrospective cohort. Patients were older than 18 years of age and admitted for severe COVID-19 Pneumonia Between March to June 2020 in 13 Hospitals in New Jersey, United States. Comparison of inflammatory markers used Kruskal-Wallis followed by pairwise comparison using two-sided Wilcoxon rank sum test. A Youden Index Method was used to determine the cut-off between low dose and high dose methylprednisolone. For each racial/ethnic group, cox regression was used to determine the association to survival between no methylprednisolone and methylprednisolone (high dose versus low dose). RESULTSPropensity matched sample (n=759) between no methylprednisolone (n=380) and methylprednisolone (n=379) had 338 Whites, 102 Blacks, 61 Asian/Indians, and 251 Non-Black Non-White Hispanics. Interleukin-6, C-reactive protein, ferritin, and d-dimer values were higher in non-survivors compared to survivors except in Asian/Indian survivors who had higher ferritin values compared to non-survivors (median: 1,265 vs 418 ug/L, P=0.0211). Black and Hispanic survivors had persistently elevated C-reactive protein, (10.2 mg/mL) and (13.70 mg/mL) respectively. Low dose methylprednisolone was associated with prolonged 60 days in hospital survival over no methylprednisolone in Whites (P<0.0001), Asian/Indians (P=0.0180), and Hispanics (P=0.0004). Regardless of dose, methylprednisolone was not associated with prolonged survival in Blacks. High dose methylprednisolone was associated with worse survival in Hispanics. (P=0.0181). CONCLUSIONRacial/Ethnic disparities with inflammatory markers in survivors and non-survivors preclude the use of one marker as predictor of survival. Low dose methylprednisolone is associated with prolonged survival in Asian/Indians, Hispanics, and Whites. Methylprednisolone, regardless of dose, was not associated with prolonged survival in Blacks.

Alveolar Soft Part Sarcoma: Progress Toward Improvement in Survival? A Population-Based Study

Background: Alveolar soft part sarcoma (ASPS) is a rare histological subtype of soft-tissue sarcoma, which remains refractory to conventional cytotoxic chemotherapy. We aimed to characterize ASPS and investigate whether the oncological outcome has improved over the past decade.Methods: One hundred and twenty patients with newly diagnosed ASPS from 2006 to 2017 were identified from the Bone and Soft-Tissue Tumor Registry in Japan. The Kaplan–Meier estimate and Cox proportional hazard model were used to investigate the survival outcomes and factors affecting prognosis.Results: The study cohort comprised 34 (28%) patients with localized ASPS and 86 (72%) with metastatic disease at presentation. The 5-year disease-specific survival (DSS) was 68% for all patients and 86% and 62% for localized and metastatic disease, respectively (p = 0.019). Metastasis at presentation was the only adverse prognostic factor for DSS (hazard ratio [HR]: 7.65; p = 0.048). Patients who were >25 years (80%; p = 0.023), had deep-seated tumors (75%; p = 0.002), and tumors >5 cm (5–10 cm, 81%; >10 cm, 81%; p < 0.001) were more likely to have metastases at presentation. In patients with localized ASPS, adjuvant chemotherapy or radiotherapy did not affect survival, and 13 patients (45%) developed distant metastases in the lung (n = 12, 92%) and brain (n = 2, 15%). In patients with metastatic ASPS (lung, n = 85 [99%]; bone, n = 12 [14%]; and brain n = 9 [11%]), surgery for the primary or metastatic site did not affect survival. The use of pazopanib significantly prolonged survival in patients who received systemic treatment (p = 0.045), whereas doxorubicin-based cytotoxic chemotherapy did not. Overall, a trend toward improved DSS for metastatic ASPS has been observed since 2012 (5-year, 58%–65%; p = 0.117), when pazopanib was approved for use in advanced disease.Conclusion: The national study confirmed a unique feature of ASPS with frequent metastasis to the lung and brain but an indolent clinical course. An overall trend toward prolonged survival after the introduction of targeted drugs encourages continuous efforts to develop novel therapeutic options for this therapeutically resistant soft-tissue sarcoma.