Significant Reduction In Tumor Burden Research Articles

ROBO1 CAR-T CELL THERAPY FOR TREATMENT REFRACTORY BRAIN CANCER

Abstract BTFC travel award recipient Glioblastoma (GBM) is the most common malignant adult brain tumor, with a dismal prognosis. Despite the multimodal treatment regimen, tumor recurrence is inevitable, and no standardized treatment exists for recurrent glioblastoma (rGBM). Neurodevelopment signaling pathways are often hijacked during tumor progression. Roundabout guidance receptor 1 (ROBO1) protein is involved in axonal guidance during neurodevelopment. Our preliminary findings implicated aberrant ROBO1 signaling axis to be associated with higher tumorigenecity in GBM, making it a functionally relevant therapeutic target. Moreover, ROBO1 was highly expressed on the surface of malignant and treatment-refractory brain tumor initiating cells (BTICs) in rGBM, brain metastasis (BM) and medulloblastoma (MB), prompting the development of an anti-ROBO1 CAR-T cell therapy. Here we report the development and validation of second-generation CAR-T cells using a single-domain antibody targeting ROBO1 expressing BTICs across three different brain tumors. We validated anti-ROBO1 CAR-T cells in-vitro and in-vivo using our established patient derived tumor models. In-vitro studies demonstrated upregulation of activation markers, enhanced cytokine release, markedly increased proliferation, and induction of potent and specific tumor cell death with ROBO1 CAR-T cells as compared to untransduced cells (UT) in all the three cancers. These findings were further validated in-vivo using 3 different BTIC lines one each from rGBM, MB and BM. ROBO1 CAR-T showed significant reduction in tumor burden and significant increase in survival of the mice treated with ROBO1 CAR-T cells in all the three cohorts. Thus, targeting ROBO1 could be a therapeutically tractable strategy for treating rGBM as well as other brain malignancies.

Abstract LB201: A novel combination of Listeria-based immunotherapy and repurposed drug combats colorectal cancer

Abstract Background: Colorectal cancer (CRC) has been a difficult-to-treat cancer with a significant proportion of microsatellite stable (MSS-CRC) patients who do not respond to immunotherapy. Currently, various strategies are being investigated to sensitize MSS-CRC tumors by converting them to immunologically “hot” tumors and improve responsiveness to immunotherapy. In this study, we demonstrate a novel strategy of combining a repurposed FDA-approved compound, Pimavanserin tartrate (PVT), with a Listeria monocytogenes (Lm)-based vaccine targeting Interferon-Stimulated Gene 15(ISG15), Lm-LLO-ISG15, against MSS-CRC tumors. Our findings demonstrate that both agents synergize to produce CD8+ T cell-dependent therapeutic efficacy in immunotherapy-resistant MSS-CRC tumors. Methods: The direct killing effect of PVT in vitro was confirmed by cytotoxic SRB assay. BALB/c mice bearing CT26, a murine model of MSS-CRC, were randomly assigned to receive either PBS, PVT, Lm-LLO-ISG15, or PVT+Lm-LLO-ISG15. Mice were monitored for tumor growth kinetics to study the anti-cancer effect of each monotherapy and the combination therapy. Changes in immune-related gene and protein expression were analyzed by qPCR and Western blot, respectively. Various immune cell subsets in the tumors and spleens were evaluated by multi-color flow cytometry and immunohistochemistry. In addition, organs such as the liver, kidney, heart, lungs, spleen, brain, and pancreas were collected for safety analysis. Results: PVT efficiently induced apoptosis and directly killed both human and mouse MSS-CRC cell lines in vitro. Further, PVT treatment enhanced T-cell activation and induced ISG15 expression, thus, sensitizing the tumor cells to targeting by the CTL-mediated immunotherapy, Lm-LLO-ISG15. While each monotherapy failed to demonstrate anti-tumor efficacy, treatment with the combination therapy (PVT + Lm-LLO-ISG15) significantly controlled tumor burden and extended the median survival. The therapeutic efficacy of the combination approach was associated with a higher infiltration of CD8+ T cells in the TME and an increased population of effector memory T cells (CD4+CD44hiCD62Llo) in the spleen. The anti-tumor efficacy of combination therapy on subcutaneous CT26 tumor growth was completely abrogated after the depletion of CD8+ T cells. Moreover, the safety profile of dual therapy was comparable to that of each monotherapy and PBS. Conclusions: MSS-CRCs are considered “immunologically cold” tumors that represent great challenges for any standalone therapies. In this study, we evaluated, for the first time, the therapeutic efficacy of a novel combination of PVT and Lm-LLO-ISG15 in an aggressive MSS-CRC mouse model. Combination therapy demonstrated a synergistic effect that led to a significant reduction of tumor burden and an extension of median survival. While the underlying mechanism for synergism requires further examination, our findings strongly suggest that combining PVT and Lm-LLO-ISG15 could be a promising approach for MSS-CRC patients. Citation Format: Shreyas Ramchandra Gaikwad, Hong My Nguyen, Sanjay K. Srivastava, Laurence Wood. A novel combination of Listeria-based immunotherapy and repurposed drug combats colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB201.

High anti-tumor activity of a novel alpha-fetoprotein-maytansinoid conjugate targeting alpha-fetoprotein receptors in colorectal cancer xenograft model

The alpha-fetoprotein receptor (AFPR) is a novel target for cancer therapeutics. It is expressed on most cancers and myeloid derived suppressor cells (MDSCs) but generally absent on normal tissues. Studies were performed to investigate the use of recombinant human AFP (ACT-101) conjugated with maytansinoid toxins for targeted toxin delivery to cancer. Four structurally different ACT-101-maytansinoid conjugates containing cleavable glutathione sensitive linkers were initially investigated in a mouse xenograft model of colorectal cancer. Reduction in tumor volume was seen for all four conjugates compared to control (p < 0.05). The anti-tumor effects of the conjugate selected for further development (ACT-903) persisted after treatment discontinuation, with tumors becoming undetectable in 9 of 10 mice, and all 10 mice surviving through Day 60 with no obvious signs of toxicity. A follow-up study performed in the same model compared the effects of single intravenous doses of ACT-903 (10–50 mg/kg) to that of control groups receiving vehicle or ACT-101. A significant reduction of tumor burden compared to control was achieved in the 40 and 50 mg/kg dose groups. Survival was significantly prolonged in these 2 groups (40 mg/kg (p < 0.0001); 50 mg/kg (p = 0.0037). Free maytansine blood levels at 4 h were 0.008% of the dose, indicating stability of the conjugate in circulation as was expected based on in vitro plasma stability studies. No obvious signs of toxicity were seen in any of the treated groups. Observed efficacy and excellent tolerability of ACT-903 in these xenograft models support advancing the development of ACT-903 toward clinical use.

Abstract 1791: Next generation UltraCAR-T® cells with intrinsic checkpoint inhibition and overnight manufacturing overcome suppressive tumor microenvironment leading to sustained antitumor activity

Abstract The UltraCAR-T® platform, with decentralized overnight manufacturing, has shifted the autologous CAR-T manufacturing paradigm. This disruptive approach has been validated in clinical and pre-clinical studies for both hematologic and solid tumors. UltraCAR-T cells, manufactured using an overnight process with minimal ex vivo manipulation of autologous T cells. UltraCAR-T cells are engineered to co-express CAR, membrane bound IL-15, and kill switch genes using non-viral gene transfer via high-throughput UltraPorator™ system. Multigenic design and overnight manufacturing renders UltraCAR-T cells with enhanced in vivo expansion and persistence for durable antitumor activity. Chronic antigen stimulation from the tumor can lead to CAR T having an exhausted phenotype contributing to treatment failures. Next generation UltraCAR-T cells also incorporate a novel cell intrinsic blockade of PD-1, superseding the need for combination therapy with checkpoint inhibitors and mitigate classic T cell exhaustion that occurs from chronic stimulation, thereby expanding the therapeutic window for efficacy. Using mesothelin (MSLN) as an exemplar from the CAR-target library, we developed a robust in vitro and in vivo model of continuous tumor antigen exposure to evaluate antitumor activity of the UltraCAR-T cells. MSLN UltraCAR-T cells were generated with and without intrinsic PD-1 blockade. In vitro, UltraCAR-T cells with intrinsic PD-1 blockade demonstrated enhanced inflammatory cytokine expression and cytotoxicity at low effector:target ratios. In long-term co-culture assays with recurring challenge of MSLN+ PD-L1+ tumor cells every 2-3 days, UltraCAR-T cells with intrinsic PD-1 blockade showed sustained potent cytotoxicity which was superior to CAR-T cells lacking PD-1 blockade and in combination with αPD-1 antibody. Intrinsic PD-1 blockade markedly enhanced polyfunctionality of UltraCAR-T cells in the presence of MSLN+ PD-L1+ tumor. In xenograft solid tumor model, a single administration of MSLN UltraCAR-T cells manufactured using UltraPorator demonstrated significant antitumor efficacy. Blood analysis showed sustained downregulation of PD-1, robust antigen specific expansion and durable persistence with central memory/stem-cell memory as the dominant phenotype of UltraCAR-T in vivo. Rechallenging the mice, who became tumor-free after a single UltraCAR-T infusion, with tumor for a second time to simulate tumor relapse led to the significant reduction in tumor burden without additional UltraCAR-T treatment. Collectively, these pre-clinical data highlight the improved efficacy of intrinsic PD-1 blockade in next generation UltraCAR-T cells using non-viral gene delivery and an established rapid, decentralized manufacturing process. Citation Format: Giorgio Zenere, Carol Poortman, Afreen Sayed, Devi Gunasekera, Cheryl Bolinger, Pooja Chauhan, Jacques Plummer, Shamim Ahmad, Rutul R. Shah, Helen Sabzevari, Douglas E. Brough, Tim Chan. Next generation UltraCAR-T® cells with intrinsic checkpoint inhibition and overnight manufacturing overcome suppressive tumor microenvironment leading to sustained antitumor activity [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 1791.

Abstract 6246: The MTA-cooperative PRMT5 inhibitor AM-9747 exhibits robust antitumor activity in combination with clinically relevant chemotherapies and targeted agents in MTAP null tumor models

Abstract Homozygous deletion of chr9p21, containing genes CDKN2A and MTAP, occurs in about 15% of cancers. MTAP loss, a key enzyme in the methionine and adenine salvage pathways, leads to the accumulation of its substrate MTA. MTA competes with the methyl donor SAM for binding to type II arginine methyltransferase PRMT5, placing PRMT5 in a hypomorphic state and vulnerable to further PRMT5 inhibition. MTA-cooperative PRMT5 inhibitors are an emerging class of therapeutics targeting MTAP null tumors. AMG 193, currently in Phase 1 trials, and its representative analog AM-9747 have broad spectrum activity in MTAP null tumor models across hematologic and solid tumor indications. Mechanistically, AM-9747 induces DNA damage, shown by increased phosphorylated H2AX, resulting in cell cycle arrest and senescence. Exploration of clinically relevant therapeutic combinations with standard of care (SOC) chemotherapies or targeted agents that could potentiate this DNA damage or target orthogonal pathways is a rational therapeutic approach. Here, we evaluated AM-9747 in combination with SOC chemotherapies and assessed synergy using the Chou-Talalay Method to generate Combination Index (CI) scores. SOC agents representing a variety of mechanisms of action (paclitaxel, carboplatin, gemcitabine, pemetrexed, irinotecan, 5-FU) were evaluated and results ranged from strongly synergistic (CI&amp;lt;0.3) to additive (CI=1) in a panel of non-small cell lung carcinoma (NSCLC) and pancreatic cancer cell lines. The SOC combinations augmented AM-9747 induced DNA damage resulting in increased cell cycle arrest and nuclear count assays confirmed the synergistic antiproliferative effects of the combinations. Combinations of AM-9747 and one strongly synergistic agent (carboplatin) and one moderately synergistic agent (paclitaxel) were evaluated in H292 NSCLC xenografts. Significant reductions in tumor burden compared to single agent treatments were observed with AM-9747 + paclitaxel (67% TGI) and AM-9747 + carboplatin (82% TGI). Additionally, roughly 2-3% of NSCLC tumors harbor both MTAP loss and a KRAS G12C mutation. To target both pathways we combined the FDA-approved KRAS G12C inhibitor sotorasib with AM-9747 and observed synergy (CI&amp;lt;0.6) in MIAPACA2 cells. Nuclear counts confirmed a greater cell growth inhibition in the combination and immunoblots confirmed on target inhibition of both pathways. Combination treatment of AM-9747 and sotorasib in LU99 NSCLC xenografts resulted in significant tumor regression compared to each single agent with 10/10 mice tumor free. This combination is being tested in additional MTAP null KRAS G12C mutant models. Overall, our data suggests that combining MTA-cooperative inhibitor AM-9747 with SOC or clinically relevant targeted agents is a compelling therapeutic strategy for the treatment of MTAP null cancers. Citation Format: Katherine Slemmons, Brian Belmontes, Siyuan Liu, Jodi Moriguchi, Antonia Policheni, Paul E. Hughes. The MTA-cooperative PRMT5 inhibitor AM-9747 exhibits robust antitumor activity in combination with clinically relevant chemotherapies and targeted agents in MTAP null tumor models. [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 6246.

Abstract 4462: Immunoregulatory effects of NNMT-expressing cancer-associated fibroblasts

Abstract Nicotinamide N-methyltransferase (NNMT) is highly expressed in the stroma of several malignancies and has been shown to drive the transformation of resting fibroblasts into cancer-associated fibroblasts (CAFs) through epigenetic changes. Given that CAFs can promote immunosuppression in cancer, the aim of our study was to investigate the effect of NNMT-expressing CAFs on the tumor-immune environment. Using a co-culture system of normal fibroblasts and activated PBMCs, we found that IFN-γ produced by PBMCs upregulates NNMT expression in fibroblasts. We confirmed this mechanism in vivo in IFN-γ knockout mice and identified T cells as the main source of IFN-γ in the tumor. Gene expression and protein analysis showed that upregulation of NNMT in CAFs induces the secretion of the chemokine CXCL1, a critical chemoattractant for immunosuppressive myeloid-derived suppressor cells (MDSCs). Upregulation of NNMT induces CXCL1 secretion directly through promoter hypomethylation, and in vitro migration assays show that NNMT-expressing CAFs recruit high numbers of MDSCs. Using spectral flow cytometry, we analyzed the tumor-immune cell infiltration in whole-body NNMT-knockout mice and discovered that NNMT knockout of the stroma significantly reduced the abundance of MDSCs and increased the number of functional CD8+ T cells. Increased T cell cytotoxicity was associated with a significant reduction in tumor burden in the syngeneic ID8 ovarian and MC38 colon cancer models. These findings were confirmed after adoptive transfer of NNMT-wildtype immune cells into irradiated whole-body NNMT-knockout mice. Moreover, in scRNA-seq data of various human malignancies, we found a strong correlation between NNMT and CXCL1 expression in CAFs. In summary, our results support a model in which cancer cells induce IFN-γ secretion by T-cells, thereby upregulating NNMT expression in fibroblasts, leading to CXCL1 secretion. CXCL1 secreted by CAFs recruits MDSCs to the tumor, which in turn suppress the anti-tumor T cell response. Citation Format: Janna Heide, Andras Piffko, Agnes J. Bilecz, Ethan A. Teich, Lisa Schweizer, Sayed R. Alhunayan, Kaiting Yang, Ernst Lengyel. Immunoregulatory effects of NNMT-expressing cancer-associated fibroblasts. [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 4462.

Abstract 837: Preclinical development of ELU001: A folate receptor alpha (FRα)-targeted C’Dot drug conjugate (CDC) for the treatment of brain metastases

Abstract Antibody-drug conjugates (ADCs) exhibit limited efficacy against brain malignancies due to their inability to cross the blood-brain barrier (BBB) and penetrate into solid tumors. In clinical imaging studies C’Dots readily crossed tumor-disrupted BBB and penetrated across/localized in tumors in the brain avoiding healthy brain. CDCs are ultra-small (6-7 nm) nanoparticles with a silica core coated by short polyethylene glycol chains conjugated to up to 80 small payload and targeting moieties, creating highly potent and avid agents. CDCs’ small size mediates rapid renal clearance leading to limited exposure to healthy tissues. ELU001 is a potent anti-FRα CDC with an average of 21 exatecan topoisomerase-1 inhibitor payload molecules and 13 folic acid targeting molecules on its surface. ELU001 is currently in a dose escalation trial in patients with systemic solid tumor indications that have the potential to overexpress FRα. Early signs of activity with a manageable safety profile have been seen across antigen expression levels. ELU001 exhibits in vitro potency in the sub/low nanomolar range against cancer cell lines that express 3+, 2+ or 1+ levels of FRα. In studies performed in immunodeficient mice bearing intracranial NCI-H2228-luc bioluminescent non-small cell lung cancer tumors, ELU001 was observed to penetrate across disrupted BBB and localize in tumors. Microscopic analysis revealed that ELU001 distributed throughout the tumors but not into the healthy brain. Treatment with a single cycle of ELU001 Q3Dx3 in mice bearing either early (Day 7) or late (Day 14) brain tumors was well tolerated and resulted in significant reduction in tumor burden measured by bioluminescence as well as a prolonged survival benefit. Retreatment of these animals resulted in an additional decrease in tumor burden. These results suggest that ELU001 may have promise for the treatment of metastatic brain tumors that are difficult to treat with currently available agents. Citation Format: Gregory P. Adams, Tin Khor, Feng Chen, Kai Ma, Marion Scocca, Aranapakam Venkatesan, Cathy Reddick, Mary Hilgart, Thomas Gardinier, Fei Wu, Melik Turker, Peiming Chen, Vaibhav Patel, Eliel Bayever. Preclinical development of ELU001: A folate receptor alpha (FRα)-targeted C’Dot drug conjugate (CDC) for the treatment of brain metastases [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 837.

Abstract 4429: ‘Free’ ISG15 acts as an immunoadjuvant to enhance CD8+ T cell-mediated anti-tumor immunity

Abstract Interferon-stimulated gene 15 (ISG15) is a ubiquitin-like molecule that is primarily involved in antiviral responses. ISG15 can either exist in the conjugated form, where it is covalently bound to proteins in a process termed ISGylation or can be released extracellularly in the cytokine-like “free” form. Although conjugated ISG15 often indicates poor prognosis in cancers, ‘free’ ISG15 is suggested to have immunostimulatory properties, owing to its ability to stimulate the production of IFN-gamma from lymphocytes and natural killer (NK) cells. While the immunomodulatory properties of free ISG15 are known, its ability to improve the antigen-specific T-cell response mediated by tumor immunotherapies has not been fully elucidated. The need for CD8+ T cell-based immunoadjuvant in cancer immunotherapy is underscored by the current failure in the generation of optimum CD8+ T cell response by the multitude of cancer vaccines in clinical trials. In this study, we demonstrated that ISG15 is vital for the generation of antigen-specific adaptive immunity; we showed that ISG15 deficient (ISG15-/-) mice do not develop effective systemic CD8+ T cell response after ovalbumin protein vaccination in non-tumor bearing mice. Upon tumor challenge of ISG15-/- mice and wild type C57/BL6 mice with B16-OVA melanoma tumors, effective OVA-specific CD8+ T cell-mediated anti-tumor immunity was not elicited, and the tumors progressed at a faster rate in the ISG15-/- mice. We then utilized a clinically relevant model to evaluate the therapeutic benefits of ‘free’ ISG15. We used a synergistic therapeutic approach that involved the concomitant administration of a DNA-construct encoding ‘free’ ISG15(mutISG15) and a Listeria-monocytogenes(Lm)-based cancer vaccine directed against the tumor vasculature (Lm-LLO-CD105A) to intervene in murine models of renal cell carcinoma (Renca) and breast cancer (4T1-Luc). The combination of Lm-LLO-CD105A and mutISG15 led to a significant reduction in tumor burden in both syngeneic models. This tumor control was mediated by the expansion of a population of highly polyfunctional CD8+ T cells in the combinatorial therapy group. These CD8+ T cells were characterized by the robust production of multiple cytokines, including IFN-gamma, IL-2, and TNF-alpha.Moreover, we confirmed that mutISG15 significantly increased the antigen (CD105)-specific anti-tumor response generated by Lm-LLO-CD105A. Not surprisingly, in-vitro studies demonstrated that mutISG15 probably potentiates the induction of maturation, activation, and antigen-presentation of dendritic cells to facilitate the activation and effective functionality of tumor-specific T cells. Conclusively, our results positions ‘free’ ISG15 as a powerful T-cell stimulant that may provide a suitable therapeutic option for improving the effectiveness of therapeutic cancer vaccines. Citation Format: Mariam Oladejo, Laurence Wood. ‘Free’ ISG15 acts as an immunoadjuvant to enhance CD8+ T cell-mediated anti-tumor immunity. [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 4429.

INNATE TL1A SIGNALING PROMOTES INTESTINAL NEUTROPHIL ACTIVATION AND COLITIS ASSOCIATED CANCER

Intestinal inflammation associated with chronic inflammatory bowel disease (IBD) increases the risk of developing colitis-associated cancer (CAC), but the cellular mechanisms driving CAC are not well defined. Polymorphisms in TNFSF15 (called TNF-like cytokine 1a or TL1A) are highly associated with IBD and the aim of this work is to evaluate a potential mechanistic role of TL1A in regulating CAC. Data from the human atlas protein database revealed that TL1A protein is present in 50% of colorectal cancer tissue samples and that high expression of TNFSF15 correlated with reduced survival. To test the functional role for TL1A in tumorigenesis, we used the well-established AOM/DSS model of CAC in mice deficient for the TL1A receptor (called death receptor 3 or DR3) and mice deficient for myeloid derived TL1A (CD11C cre+TNFSF15fl/fl). We found that both DR3-deficient mice and myeloid derived TL1A deficient mice had a significant reduction in tumor number compared to heterozygous littermate controls. To evaluate the contribution of innate lymphocytes, we used DR3-deficient mice on a RAG-deficient background in our AOM/DSS model. Even in the absence of B and T cells, DR3-deficient mice still showed significant reduction in tumor burden, suggesting innate lymphoid cell (ILC) contribution. DR3-deficient mice also revealed a significant reduction in neutrophil infiltration. Neutrophil depletion with α-Ly6G similarly resulted in a significant reduction of tumor numbers in our CAC model in a DR3 dependent manner. To test the direct regulation of neutrophils by ILCs, we establish a co-culture model. TL1A activated ILCs triggered neutrophil activation (CD177) and maturation (CD11B) which required GM-CSF. In vivo activation with a DR3 agonist confirmed intestinal ILC3 production of GM-CSF but also impacted bone marrow granulopoiesis by expanding both mature neutrophils and granulocyte-macrophage progenitors (GMPs).

Metformin confers sensitisation to syrosingopine in multiple myeloma cells by metabolic blockage and inhibition of protein synthesis.

Multiple myeloma (MM) remains an incurable haematological malignancy despite substantial advances in therapy. Hypoxic bone marrow induces metabolic rewiring in MM cells contributing to survival and drug resistance. Therefore, targeting metabolic pathways may offer an alternative treatment option. In this study, we repurpose two FDA-approved drugs, syrosingopine and metformin. Syrosingopine was used as a dual inhibitor of monocarboxylate transporter 1 and 4 (MCT1/4) and metformin as an inhibitor for oxidative phosphorylation (OXPHOS). Anti-tumour effects were evaluated for single agents and in combination therapy. Survival and expression data for MCT1/MCT4 were obtained from the Total Therapy 2, Mulligan, and Multiple Myeloma Research Foundation cohorts. Cell death, viability, and proliferation were measured using Annexin V/7-AAD, CellTiterGlo, and BrdU, respectively. Metabolic effects were assessed using Seahorse Glycolytic Rate assays and LactateGlo assays. Differential protein expression was determined using western blotting, and the SUnSET method was implemented to quantify protein synthesis. Finally, the syngeneic 5T33MMvv model was used for in vivo analysis. High-level expression of MCT1 and MCT4 both correlated with a significantly lower overall survival of patients. Lactate production as well as MCT1/MCT4 expression were significantly upregulated in hypoxia, confirming the Warburg effect in MM. Dual inhibition of MCT1/4 with syrosingopine resulted in intracellular lactate accumulation and reduced cell viability and proliferation. However, only at higher doses (>10μm) was syrosingopine able to induce cell death. By contrast, combination treatment of syrosingopine with metformin was highly cytotoxic for MM cell lines and primary patient samples and resulted in a suppression of both glycolysis and OXPHOS. Moreover, pathway analysis revealed an upregulation of the energy sensor p-AMPKα and more downstream a reduction in protein synthesis. Finally, the combination treatment resulted in a significant reduction in tumour burden in vivo. This study proposes an alternative combination treatment for MM and provides insight into intracellular effects. © 2023 The Pathological Society of Great Britain and Ireland.

Small molecule ‘4ab’ induced autophagy and endoplasmic reticulum stress-mediated death of aggressive cancer cells grown under adherent and floating conditions

Metastasis is the leading cause of death in cancer patients and a major challenging aspect of cancer biology. Various adaptive molecular signaling pathways play a crucial role in cancer metastasis and later in the formation of secondary tumors. Aggressive cancer cells like triple negative breast cancer (TNBCs) are more inclined to undergo metastasis hence having a high recurrence rate and potential of micro-metastasis. Tumor cells in circulation known as circulating tumor cells (CTCs) offer an attractive drug target to treat metastatic disease. Cell cycle regulation and stress response of CTCs in blood has a crucial role in their survival and progression and thus may be considered therapeutically active hotspots. The cyclin D/cyclin-dependent kinase (CDK) pathway regulates cell cycle checkpoints, a process that is frequently dysregulated in cancer cells. Selective CDK inhibitors can limit the phosphorylation of cell cycle regulatory proteins by inducing cell cycle phase arrest, and thus may be an effective therapeutic strategy for aggressive cancer cells in their dividing phase at the primary or secondary site. However, during the floating condition, cancer cells halt their multiplication process and proceed through the various steps of metastasis. Current study showed that a novel CDK inhibitor 4ab induced autophagy and endoplasmic reticulum (ER) stress inagressive cancer cells grown under adherent and floating conditions resulting in paraptosis. Further, our results showed that 4ab efficiently induced cell death in aggressive cancer cells through ER stress-mediated activation of JNK signaling. Additionally,was observed that treatment of 4ab in tumor-bearing mice displayed a significant reduction in tumor burden and micro-metastasis. The outcome of these studies showed that 4ab can be a potential anti-tumor and anti-metastatic agent. Graphical representation of 4ab: image representing the effect of 4ab on death-inducing pathways in aggressive cancer cells. 4ab induces ER stress and activates autophagy leading to vacuolation of thereby causing apoptosisin aggressive cancer cells.

The Effect of Iontophoretic-Delivered Polyplex Vaccine on Melanoma Regression.

Although the strategy in cancer vaccination is to provide a therapeutic effect against an established tumor, there is an urgent need to develop prophylactic vaccines for non-viral cancers. In this study, we prepared polyplex nanoparticles through electrostatic interactions between a positively-charged modified tumor associated antigen, namely human derived melanoma gp10025-33 peptide (KVPRNQDWL-RRRR), and a negatively charged cytosine-phosphate-guanosine motif (CpG-ODN) adjuvant. We previously demonstrated successful transdermal delivery of various hydrophilic macromolecules by iontophoresis (IP) using weak electricity. Herein, we investigated the effectiveness of IP in the transdermal delivery of a prophylactic polyplex vaccine. IP was successful in establishing a homogenous distribution of the vaccine throughout skin. Efficacy of the vaccine was demonstrated against melanoma growth. A significant tumor regression effect was observed, which was confirmed by elevated mRNA expression levels of various cytokines, mainly interferon (IFN)-γ, as well as infiltration of cytotoxic CD8+ T cells. Additionally, we evaluated the therapeutic effect of the vaccine and we found a significant reduction in tumor burden. Stimulation of systemic immunity was confirmed by upregulation of IFN-γ. This is the first report to demonstrate the use of IP in the transdermal delivery of a prophylactic melanoma vaccine.

A combination therapy of bortezomib, CXCR4 inhibitor, and checkpoint inhibitor is effective in cholangiocarcinoma in vivo

Cholangiocarcinoma (CCA) is a biliary tree malignancy with a dismal prognosis. Tumor microenvironment (TME), including cancer-associated fibroblasts (CAFs) has been shown to be involved in drug resistance. To model the interactions between cancer cells and the TME, we established CCA complex patient-derived organoids (cPDOs) to include epithelial PDO (ePDOs) and matched CAFs. While ePDOs were sensitive to bortezomib, we found the matched cPDOs were relatively resistant. Mechanistically, this resistance was correlated with over-expression of CXCR4 in the CAF component of cPDOs. In accord with the role of CXCR4 in the resistance to bortezomib, we found that a CXCR4 inhibitor can reverse the resistance to bortezomib invivo. Furthermore, we found that the inhibition of CXCR4 allowed bortezomib to sensitize CCA to anti-PD1 treatment, with a significant reduction of tumor burden and long-term overall survival. This novel cancer/stroma/immune triple treatment holds great promise for the treatment of CCA.

INNATE TL1A SIGNALING PROMOTES INTESTINAL NEUTROPHIL ACTIVATION AND COLITIS ASSOCIATED CANCER

Abstract Intestinal inflammation associated with chronic inflammatory bowel disease (IBD) increases the risk of developing colitis-associated cancer (CAC), but the cellular mechanisms driving CAC are not well defined. Polymorphisms in TNFSF15 (called TNF-like cytokine 1a or TL1A) are highly associated with IBD and the aim of this work is to evaluate a potential mechanistic role of TL1A in regulating CAC. Data from the human atlas protein database revealed that TL1A protein is present in 50% of colorectal cancer tissue samples and that high expression of TNFSF15 correlated with reduced survival. To test the functional role for TL1A in tumorigenesis, we used the well-established AOM/DSS model of CAC in mice deficient for the TL1A receptor (called death receptor 3 or DR3) and mice deficient for myeloid derived TL1A (CD11C cre+TNFSF15fl/fl). We found that both DR3-deficient mice and myeloid derived TL1A deficient mice had a significant reduction in tumor number compared to heterozygous littermate controls. To evaluate the contribution of innate lymphocytes, we used DR3-deficient mice on a RAG-deficient background in our AOM/DSS model. Even in the absence of B and T cells, DR3-deficient mice still showed significant reduction in tumor burden, suggesting innate lymphoid cell (ILC) contribution. DR3-deficient mice also revealed a significant reduction in neutrophil infiltration. Neutrophil depletion with α-Ly6G similarly resulted in a significant reduction of tumor numbers in our CAC model in a DR3 dependent manner. To test the direct regulation of neutrophils by ILCs, we establish a co-culture model. TL1A activated ILCs triggered neutrophil activation (CD177) and maturation (CD11B) which required GM-CSF. In vivo activation with a DR3 agonist confirmed intestinal ILC3 production of GM-CSF but also impacted bone marrow granulopoiesis by expanding both mature neutrophils and granulocyte-macrophage progenitors (GMPs). CONCLUSION: Our data reveals a new link between intestinal ILC production of GM-CSF and neutrophil activation that promotes CAC and bone marrow granulopoiesis.

Sequential Administration of Selinexor then CD19 CAR-T Cells Exhibits Enhanced Efficacy in a Mouse Model of Human Non-Hodgkin's Lymphoma

Novel therapeutic approaches are urgently needed for many patients with Non-Hodgkin's Lymphoma (NHL). Approximately 30% of patients die within 5 years of diagnosis and many more relapse. Chimeric Antigen Receptor T cells (CAR-T) directed toward NHL antigens (e.g. CD19) are a promising new class of therapeutics for some patients with relapsed/refractory NHL, though a high percentage of patients (~50%) still fail to enter remission or relapse within one year of CD19 CAR-T therapy. Another approved therapeutic for treatment of a subtype of NHL patients is the nuclear export inhibitor, selinexor. Selinexor binds to exportin 1 and exhibits anti-tumor activity by impairing nuclear export of proteins including oncogenes and tumor suppressor proteins. As both CD19 CAR-T cells and selinexor exhibit activity against lymphoma cells, but suboptimal long term efficacy in patients, we assessed the combination of both treatments in a mouse model of NHL. The combinatorial efficacy was assessed using a circulating model of human NHL whereby RAJI-luciferase cells were intravenously injected into immunocompromised mice. Initial studies initiated treatment 7 days post tumor cell injection. Mice (n=5 NSG mice per cohort) were treated with selinexor alone (10mg/kg gavage 2x week) for study duration, CD19 CAR-T cells alone (single injection of 2.5x106 million cells) or a concurrent combination. Mice were imaged weekly for bioluminescence to monitor tumor progression. While CD19 CAR-T cells alone led to inhibition of tumor growth, there was no further enhancement in efficacy with the addition of concurrent treatment with selinexor (Figure 1A). Interestingly, when selinexor instead was administered only prior to CAR-T cell injection (10mg/kg gavage Day 1 and Day 3 post tumor cell injection followed by CAR-T injection Day 7 post tumor cell injection), there was a significant reduction in tumor burden in the combination group (Figure 1B). These results suggest that the tumor cells become sensitized to CD19 CAR-T mediated cell killing from selinexor administration. As both agents are FDA approved for certain NHL patients, this therapeutic strategy has high clinical relevance. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

INNV-18. PROLONGED REMISSION AFTER TREATMENT WITH SINGLE-AGENT IBRUTINIB AS MAINTENANCE THERAPY FOLLOWING SALVAGE RADIATION THERAPY FOR REFRACTORY/RELAPSE PRIMARY CNS LYMPHOMA

Abstract INTRODUCTION Primary central nervous system lymphoma (PCNSL) is a rare and aggressive disease. Standard induction therapy for PCNSL consists of a high-dose methotrexate-based (HD-MTX) regimen. For relapsed or refractory primary CNS lymphoma (r/r PCNSL), most of the non-standard treatment regimens including additional chemotherapy, stem cell transplant, or whole brain radiation therapy (WBRT) may not reach long-term remission due to intolerance of the treatment by the patients or lack of effects. Here we report a case with r/r PCNSL reached more than 50-month remission after salvage WBRT followed by single agent ibrutinib maintenance therapy. CASE REPORT: a 75-year-old female with PCNSL, experienced disease recurrence, despite undergoing multiple lines of treatment including initial HD-MTX, second-line rituximab and temozolomide, repeated HD-MTX, and a clinical trial. Because her disease was refractory to these treatment options, we decided to start WBRT as salvage therapy, which resulted in significant reduction of tumor burden. Prior studies, however, showed that r/r PCNSL patients who underwent salvage WBRT alone had a median survival of only 1-2 years. Therefore, to extend the remission after salvage WBRT, she opted to try ibrutinib, a Bruton’s tyrosine kinase inhibitor with past success in treating r/r PCNSL patients, as maintenance therapy after salvage WBRT. She tolerated well and decided to be off the treatment after 18 month-maintenance therapy. The patient has been stable clinically. She has since survived for more than 50 months after the completion of salvage WBRT plus maintenance therapy with ibrutinib. DISCUSSION Compared to prior reports of 11 to 16 months of median survival after salvage WBRT alone for r/r PCNSL, our case has had prolonged survival, which supports the potential positive effect of ibrutinib as maintenance therapy for r/r PCNSL after salvage WBRT

CNSC-28. IDENTIFICATION OF EAG2-KVß2 POTASSIUM CHANNEL COMPLEX IN NEURON-GBM COMMUNICATIONS REVEALS GBM VULNERABILITY TO DESIGNER INTERFERENCE PEPTIDE

Abstract Glioblastomas (GBMs) are the most aggressive brain tumors. GBM cells form extensive tumoral networks to communicate with each other and with surrounding neurons. Neuronal activity promotes GBM cell proliferation by secreting protumorigenic factors and triggering neuronal-activity-dependent Ca2+ transients, which are persisted and transmitted via tumor networks to promote overall tumor growth and therapy resistance. While how these processes are regulated is largely unknown. Here we show the GBM networks and Ca2+ transients are regulated by a voltage-gated potassium channel complex comprised of EAG2 and Kvβ2. GBM cells selectively overexpress Kvβ2 isoform 4 to facilitate tumor-specific Kvβ2-EAG2 interaction, which regulates neuron-GBM contact-dependent localization of EAG2. Rationally designed interfering peptide K90-114TAT blocks EAG2-Kvβ2 interaction, leading to reduced tumor cell proliferation, increased apoptosis, and prolonged survival of patient-derived xenograft mouse models with no evidence of toxicity to normal tissue. Single-cell RNA sequencing revealed a subgroup of GBM cells is highly sensitive to K90-114TAT treatment. These cells exhibit neuronal signatures and are highly associated with TMZ resistance and worse prognosis. In accordance with the notion, we found neurons promote TMZ resistance of GBM cells, which is regulated by the EAG2-Kvβ2 complex. Treating TMZ-resistant GBM xenograft mice with K90-114TAT yielded significant tumor burden reduction and prolonged survival. Together, our findings revealed the EAG2-Kvβ2 channel complex as a key regulator of neuron promoted GBM progression and designed an interfering peptide with anti-GBM efficacy and low general toxicity, which may have significant clinical impact.

A novel role of Tinospora cordifolia in amelioration of cancer-induced systemic deterioration by taming neutrophil infiltration and hyperactivation

BackgroundCancer has emerged as a systemic disease which targets various organs thus challenging the overall physiology of the host. Recently, we have shown that hyperactive neutrophils infiltrate various organs of tumor bearing host and contribute to gradual systemic deterioration. Therefore, taming neutrophils via potent immunomodulators could be an appropriate therapeutic approach in regulating systemic damage. Tinospora cordifolia (TC), an Ayurvedic panacea, is known for its immense medicinal values in traditional literature and recent reports have also documented its immunomodulatory potential. However, whether TC can regulate neutrophils to exert its therapeutic effectiveness has not been deciphered so far. MethodsFor the in vivo study, we utilized murine model of Dalton's Lymphoma (DL). T. cordifolia extract (TCE) treatment was scheduled at early, mid and advanced stages of tumor growth at a dose of 400 mg/kg b.w for 30 consecutive days. Effect of TCE on neutrophil infiltration was examined by immunostaining. Neutrophil elastase (NE) level in serum, ascitic fluid and various tissues was monitored by ELISA. Further, qPCR was performed to assess transcripts levels of NE, myeloperoxidase (MPO), metalloproteinases (MMP-8, MMP-9) and cathepsin G (CSTG) in various tissues. ROS level in tissue was assessed by DHE staining and organ function was assessed by histology post TCE treatment. ResultsOur findings showed that TC treatment significantly reduced neutrophil count in peripheral blood and their infiltration in vital organs of tumor-bearing host. Further, it ameliorated neutrophil hyperactivation by down regulating the expression of its key cargoes including NE, MPO, MMP-8, MMP-9 and CSTG at early and mid stage of tumor growth. In addition, TC treatment prevented histopathological alterations and restored the normal serum enzyme levels at different stages of tumor growth. Importantly, TC treatment also showed significant reduction in tumor burden which was accompanied by a remarkable increase in survival of the tumor-bearing mice. ConclusionsWe conclude that T. cordifolia could limit systemic damage via regulating neutrophil infiltration and hyperactivation which can further lead to cancer control at both prophylactic and therapeutic level.

CRISPR-based kinome-screening revealed MINK1 as a druggable player to rewire 5FU-resistance in OSCC through AKT/MDM2/p53 axis

Cisplatin, 5FU and docetaxel (TPF) are the most common chemotherapy regimen used for advanced OSCC. However, many cancer patients experience relapse, continued tumor growth, and spread due to drug resistance, which leads to treatment failure and metastatic disease. Here, using a CRISPR/Cas9 based kinome knockout screening, Misshapen-like kinase 1 (MINK1) is identified as an important mediator of 5FU resistance in OSCC. Analysis of clinical samples demonstrated significantly higher MINK1 expression in the tumor tissues of chemotherapy non-responders as compared to chemotherapy responders. The nude mice and zebrafish xenograft experiments indicate that knocking out MINK1 restores 5FU mediated cell death in chemoresistant OSCC. An antibody based phosphorylation array screen revealed MINK1 as a negative regulator of p53. Mechanistically, MINK1 modulates AKT phosphorylation at Ser473, which enables p-MDM2 (Ser 166) mediated degradation of p53. We also identified lestaurtinib as a potent inhibitor of MINK1 kinase activity. The patient derived TPF resistant cell based xenograft data suggest that lestaurtinib restores 5FU sensitivity and facilitates a significant reduction of tumor burden. Overall, our study suggests that MINK1 is a major driver of 5FU resistance in OSCC. The novel combination of MINK1 inhibitor lestaurtinib and 5FU needs further clinical investigation in advanced OSCC.

Abstract PO032: Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)-TRAIL-R Mediates Cholangiocarcinoma Tumor Immune Evasion by Enhancing Myeloid-Derived Suppressive Cell Population

Abstract Background and Aims: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of TNF superfamily, is predominantly expressed on immune cells. Engagement of TRAIL with its cognate receptor, TRAIL-R (TR), leads to cancer cells apoptosis. Although the anti-tumor role of TRAIL-TR has been extensively studied, TRAIL agonists have had very limited anti-cancer activity in human clinical trials. TRAIL signaling can facilitate the myeloid response. However, this potential immunosuppressive function of TRAIL has not been examined extensively in cancer biology. Cholangiocarcinoma (CCA), a highly lethal biliary tract cancer, has a dense immunosuppressive microenvironment. Accordingly, CCA provides a model to examine the potential immune regulatory function of TRAIL in cancer biology. Methods: Using syngeneic, orthotopic murine models of CCA, (PMID: 29464042), murine CCA cells (SB cells) that express both Trail and Trail receptor (Tr) were implanted into livers of WT Tr− / − and LyzcreTrf/f mice, the latter have a specific deletion of TRAIL-R on myeloid cells. Hence, in this model the host immune cells express Trail but not the receptor; therefore, they would be capable of inducing TRAIL-mediated apoptosis in CCA cells but would be resistant to TRAIL-mediated immunosuppression. After 4 weeks of tumor growth, mice were sacrificed, and tumors were characterized using flow cytometry. Results: We observed that Tr− / − mice had a significant reduction in tumor burden compared to WT mice. Myeloid-derived suppressor cells (MDSCs) were significantly decreased in Tr− / − tumors compared to WT tumors. Implantation of SB cells into LyzcreTrf/f mice resulted in a marked reduction in tumor burden and attenuation of MDSC infiltration compared to Lyzcre mice. In vitro functional studies employing MDSCs from mice deficient in Tr (MDSC-Tr −/−) were carried out. Compared to WT MDSCs, coculture of MDSC-Tr− /- with SB cells resulted in a significant reduction in the proliferation and immunosuppressive function of MDSCs. Moreover, following cocultured with SB cells, immunofluorescence analysis demonstrated that MDSC-Tr− / − had a reduction in the nuclear translocation of the NFkB subunit P65 compared to WT MDSCs. These data suggest that TRAIL-TR augments MDSC proliferation via NFkB. In conclusion, we have demonstrated that Tr− / − mice have a significant reduction in CCA tumor burden and MDSC infiltration. These results indicate that TRAIL-TR facilitates tumor immune escape and progression by fostering MDSC immunosuppressive function and infiltration, in an NFkB-dependent manner. Direct targeting of TRAIL on CCA cells is a potential anti-tumor strategy. Citation Format: Emilien Loeuillard, Jingchun Yang, Dong Haidong, Gregory Gores, Sumera Ilyas. Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)-TRAIL-R Mediates Cholangiocarcinoma Tumor Immune Evasion by Enhancing Myeloid-Derived Suppressive Cell Population [abstract]. In: Proceedings of the AACR Special Conference: Advances in the Pathogenesis and Molecular Therapies of Liver Cancer; 2022 May 5-8; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(17_Suppl):Abstract nr PO032.