Agents In Preclinical Models Research Articles

Cytotoxicity, Proapoptotic Activity and Drug-like Potential of Quercetin and Kaempferol in Glioblastoma Cells: Preclinical Insights

Despite the increasing understanding of the pathogenesis of glioblastoma (GBM), treatment options for this tumor remain limited. Recently, the therapeutic potential of natural compounds has attracted great interest. Thus, dietary flavonoids quercetin (QCT) and kaempferol (KMF) were investigated as potential cytostatic agents in GBM. Moreover, the physicochemical properties of QCT and KMF, determining their bioavailability and therapeutic efficiency, were evaluated. We proved that both polyphenols significantly reduced the viability of GBM cells. We also demonstrated that both QCT and KMF evoked the cytotoxic effect in T98G cells via induction of apoptotic cell death as shown by increased activity of caspase 3/7 and caspase 9 together with an overexpression of the cleaved form of PARP. Apoptosis was additionally accompanied by the activation of stress responses in QCT- and KMF-treated cells. Both polyphenols caused oxidative stress and endoplasmic reticulum (ER) stress, as demonstrated by the increased generation of reactive oxygen species (ROS), deregulated expressions of superoxide dismutases (SOD2 and Sod1 on protein and transcriptomic levels, respectively), as well as an overexpression of ERO1α, GRP78, p-JNK, and an up-regulation of Chop, Atf4 and Atf6α genes. The antitumor effect of QCT and KMF was also confirmed in vivo, showing reduced growth of tumor xenografts in the chick chorioallantoic membrane (CAM) experiment. Moreover, electrophoretic light scattering (ELS) was used to measure the zeta potential of cell membranes upon exposition to QCT and KMF. Additionally, on the basis of existing physicochemical data, the drug-likeness score of QCT and KMF was evaluated. Analyses showed that both compounds accomplish Lipinski’s Rule of 5, and they both fit into the criteria of good central nervous system (CNS) drugs. Altogether, our data support the idea that QCT and KMF might be plausible candidates for evaluation as therapeutic agents in preclinical models of glioblastoma.

Rocuronium-specific antibodies drive perioperative anaphylaxis but can also function as reversal agents in preclinical models.

Neuromuscular blocking agents (NMBAs) relax skeletal muscles to facilitate surgeries and ease intubation but can lead to adverse reactions, including complications because of postoperative residual neuromuscular blockade (rNMB) and, in rare cases, anaphylaxis. Both adverse reactions vary between types of NMBAs, with rocuronium, a widely used nondepolarizing NMBA, inducing one of the longest rNMB durations and highest anaphylaxis incidences. rNMB induced by rocuronium can be reversed by the synthetic γ-cyclodextrin sugammadex. However, in rare cases, sugammadex can provoke anaphylaxis. Thus, additional therapeutic options are needed. Rocuronium-induced anaphylaxis is proposed to rely on preexisting rocuronium-binding antibodies. To understand the pathogenesis of rocuronium-induced anaphylaxis and to identify potential therapeutics, we investigated the memory B cell antibody repertoire of patients with suspected hypersensitivity to rocuronium. We identified polyclonal antibody repertoires with a high diversity among V(D)J genes without evidence of clonal groups. When recombinantly expressed, these antibodies demonstrated specificity and low affinity for rocuronium without cross-reactivity for other NMBAs. Moreover, when these antibodies were expressed as human immunoglobulin E (IgE), they triggered human mast cell activation and passive systemic anaphylaxis in transgenic mice, although their affinities were insufficient to serve as reversal agents. Rocuronium-specific, high-affinity antibodies were thus isolated from rocuronium-immunized mice. The highest-affinity antibody was able to reverse rocuronium-induced neuromuscular blockade in nonhuman primates with kinetics comparable to that of sugammadex. Together, these data support the hypothesis that antibodies cause anaphylactic reactions to rocuronium and pave the way for improved diagnostics and neuromuscular blockade reversal agents.

Abstract A004: Radiotherapy sensitizes preclinical models to DNA damage response agents

Abstract Introduction Radiotherapy is a key treatment for various cancers, with nearly 50% of all cancer patients receiving it as part of their therapeutic plan. It can activate cytotoxic signaling pathways to promote cancer cell death but also trigger cytoprotective mechanisms that respond to cellular damage. These cytoprotective mechanisms can be inhibited by targeted anticancer agents such as DNA damage response (DDR) agents, suggesting that radiotherapy could enhance the efficacy of these drugs. This study presents data showing radiotherapy enhances the potency of DDR agents in preclinical models. Methods and experimental procedures The MDA-MB-436 breast and A549 lung cancer cell lines were utilized to establish in vitro assays and in vivo models for the study. Agents targeting DNA-PK (AZD7648) and PARP (niraparib) were used as they work on pathways crucial for the repair of radiation-induced DNA double-strand breaks. The effects on cell viability and DDR biomarkers were assessed after treatment with irradiation (IR), compound or in combination both in vitro and in vivo. Targeted X-rays were delivered using an Xstrahl CIX3 cabinet irradiator, in vivo radiotherapy was delivered to the tumor only. Data An increased sensitivity to DDR agents when combined with radiotherapy was observed in vitro in both cell lines, compared to standalone treatments. A single dose of radiotherapy significantly reduced cell viability beyond the effects of radiotherapy or compound treatment alone. The induction of biomarkers by radiotherapy as monotherapy or in combination with DDR inhibitors was assessed. Changes in biomarker expression were consistent with those observed in the in vivo xenograft models. The administration of fractionated dosing regimens for radiotherapy was well-tolerated in vivo. Combination of radiotherapy with the DDR compounds led to tumor growth delay and enhanced survival outcomes. Conclusion In summary, in vitro assays and in vivo models have been established to investigate the synergistic effects of the combination of radiotherapy and DDR agents. Radiotherapy increased sensitivity of 2 human cancer cell lines to the DDR agents in vitro, and lead to tumor growth delay in vivo. These assays can be used as preclinical tools to identify novel compounds or mechanisms that can be successfully combined with radiotherapy. Citation Format: Pablo Binder, Theoni Katopodi, Lyndsey Hanson, Charlotte R. Bell, Eimear Flanagan, Paul Farrington, Nick Moore, Emily Wright, Yin Xin Ho, Tobias Bunday, Stewart Brown, Amy Cantrell, Yael Mamane, Jon Greenall, Shannon Sharman, John Woolley, Lorraine M. Mooney, Jane Kendrew. Radiotherapy sensitizes preclinical models to DNA damage response agents [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr A004.

Dual and Triple Incretin-Based Co-agonists: Novel Therapeutics for Obesity and Diabetes.

The discovery of long-acting incretin receptor agonists represents a major stride forward in tackling the dual epidemic of obesity and diabetes. Here we outline the evolution of incretin-based pharmacotherapy, from exendin-4 to the discovery of the multi-incretin hormone receptor agonists that look set to be our next step toward curing diabetes and obesity. We discuss the multiagonists currently in clinical trials and the improvement in efficacy each new generation of these drugs bring. The success of these agents in preclinical models and clinical trials suggests a promising future for multiagonists in the treatment of metabolic diseases, with the most recent glucose-dependent insulinotropic peptide receptor:glucagon-like peptide1 receptor:glucagon receptor (GIPR:GLP-1R:GCGR) triagonists rivaling the efficacy of bariatric surgery. However, further research is needed to fully understand how these therapies exert their effect on body weight and in the last section we cover open questions about the potential mechanisms of multiagonist drugs, and the understanding of how gut-brain communication can be leveraged to achieve sustained body weight loss without adverse effects.

Abstract 627: IL-6 signaling via JAK/STAT axis influences PIM1 expression in renal cell carcinoma

Abstract Renal cell carcinoma (RCC) is a top ten malignancy in the U.S. Overexpression of the proviral integration site for moloney murine leukemia virus 1 (PIM1) kinase is associated with poor clinical outcomes in RCC patients. PIM1 is a constitutively active serine/threonine kinase promoting cell proliferation, apoptosis resistance, invasion, and migration. The mechanisms underlying PIM1 expression and its function in RCC are not fully delineated. IL-6 is a pleiotropic cytokine that activates the JAK/STAT signaling cascade. High serum IL-6 levels are associated with the poor prognosis of RCC patients and may contribute to RCC invasion and metastasis. STAT3/5 binds directly to the PIM1 promoter inducing PIM1 expression. An IL-6/STAT3/PIM1 axis exists in pancreatic and breast cancer. We previously reported that PIM1 is overexpressed in a panel of human RCC cell lines relative to normal and immortalized renal proximal tubule epithelial cells. We also identified that RCC cells secrete IL-6. Our prior studies suggest that differential expression of PIM1 may be linked to autocrine IL-6 signaling. We thus hypothesize that an IL-6/JAK/STAT pathway regulates the expression of PIM1 in RCC. To understand how IL-6 signaling through the JAK/STAT pathway may regulate PIM1 expression in RCC cells, we examined whether IL-6 blockade using anti-IL-6 antibody or tocilizumab, would modulate PIM1 expression. Similarly, we assessed whether ruxolitinib, and LLL12, a STAT3 inhibitor could regulate PIM1 expression. We then evaluated the effect of ruxolitinib treatment on cell viability. In RCC cell lines, IL-6 blockade through either anti-IL-6 antibody or tocilizumab was sufficient to decrease PIM1 protein levels. Treatment with ruxolitinib leads to a dose and time-dependent decrease in PIM1 levels. Incubation with a STAT3 inhibitor also resulted in decreased PIM1 levels in RCC cells. Treatment with ruxolitinib also appears to decrease cell viability in a dose-dependent manner. These results suggest that differential expression of PIM1 in RCC may be linked to autocrine IL-6 signaling via a JAK/STAT/PIM1 axis. Multiple FDA-approved agents are available that target this pathway. Further investigation is required to determine the efficacy of these agents in pre-clinical models and even clinical trials. Citation Format: Kimberly S. Meza, Kimberly Seymour, Sheldon L. Holder. IL-6 signaling via JAK/STAT axis influences PIM1 expression in renal cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 627.

Abstract B016: Novel curcumin analogues as therapies for endometrial cancer with TP53 mutations

Abstract The protein p53 is designated as the guardian of the genome because it is the principal tumor suppressor and functions to surveil the genome, enforce cell cycle checkpoints, and trigger apoptosis when genomic instability is beyond repair. Mutations in TP53 are found in >50% of human tumors and in 25% of the deadliest endometrial malignancies. Yet, few studies have targeted the mutant protein to restore its wild type (WT) tumor suppressor functions. Curcumin, a turmeric derivative, has been shown to help return WT function to mutant p53. However, curcumin is not bioavailable to most of the body because of its water insolubility, hydrophobic nature and rapid metabolization. Our laboratory is testing novel, more bioavailable analogs of curcumin including HO-3867 and AKT-100. In these studies, we tested these agents in preclinical models of serous endometrial cancer to assess their effects on cell growth and p53-dependent signaling. We used CyQUANT cell proliferation assay to identify IC50 values for HO-3867 and AKT-100 in ECC-1 and KLE endometrial cancer cell lines. We performed RNA sequencing to elucidate mechanisms of action and verified p53 expression changes via Western blotting. IC50 values ranged from 100 nanomolar (AKT-100) to low micromolar (HO-3867). RNA sequencing data revealed the re-enforcement of cell cycle checkpoints including the upregulation of CDKN1A (p21) and GADD45 (Gadd45). Proliferative signaling downstream of ATM, an important protein kinase stimulating cell growth, was downregulated by both agents. Western blotting confirmed the classic negative feedback loop of p53, where total p53 levels decreased after drug treatment. Taken together, our findings show that AKT-100 and HO-3867 are able to restore WT tumor suppressor function in otherwise oncogenic mutant p53 by reducing cell replication and promoting apoptosis. Thus, curcumin analogues such as AKT-100 and HO-3867 show promise in the treatment of a subset of endometrial tumors expressing mutant p53 by returning WT p53 functionality, and future studies will move to in vivo analyses of curcumin analogue function. Citation Format: Kimberly K. Leslie, Alex Goss, Jamie Padilla, Lane E. Smith. Novel curcumin analogues as therapies for endometrial cancer with TP53 mutations [abstract]. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(5_Suppl):Abstract nr B016.

Clinicopathological and Molecular Characteristics of IDH-Wildtype Glioblastoma with FGFR3::TACC3 Fusion.

The World Health Organization Classification of Tumors of the Central Nervous System recently incorporated histological features, immunophenotypes, and molecular characteristics to improve the accuracy of glioblastoma (GBM) diagnosis. FGFR3::TACC3 (F3T3) fusion has been identified as an oncogenic driver in IDH-wildtype GBMs. Recent studies have demonstrated the potential of using FGFR inhibitors in clinical trials and TACC3-targeting agents in preclinical models for GBM treatment. However, there is limited information on the clinicopathological and genetic features of IDH-wildtype GBMs with F3T3 fusion. The aim of this study was to comprehensively investigate the clinical manifestations, histological features, and mutational profiles of F3T3-positive GBMs. Between September 2017 and February 2023, 25 consecutive cases (5.0%) of F3T3-positive GBM were extracted from 504 cases of IDH-wildtype GBM. Clinicopathological information and targeted sequencing results obtained from 25 primary and 4 recurrent F3T3-positive GBMs were evaluated and compared with those from F3T3-negative GBMs. The provisional grades determined by histology only were distributed as follows: 4 (26/29; 89.7%), 3 (2/29; 6.9%), and 2 (1/29; 3.4%). Grade 2-3 tumors were ultimately diagnosed as grade 4 GBMs based on the identification of the TERT promoter mutation and the combined gain of chromosome 7 and loss of chromosome 10 (7+/10-). F3T3-positive GBMs predominantly affected women (2.6 females per male). The mean age of patients with an F3T3-positive GBM at initial diagnosis was 62 years. F3T3-positive GBMs occurred more frequently in the cortical locations compared to F3T3-negative GBMs. Imaging studies revealed that more than one-third (12/29; 41.4%) of F3T3-positive GBMs displayed a circumscribed tumor border. Seven of the seventeen patients (41.2%) whose follow-up periods exceeded 20 months died of the disease. Histologically, F3T3-positive GBMs more frequently showed curvilinear capillary proliferation, palisading nuclei, and calcification compared to F3T3-negative GBMs. Molecularly, the most common alterations observed in F3T3-positive GBMs were TERT promoter mutations and 7+/10-, whereas amplifications of EGFR, PDGFRA, and KIT were not detected at all. Other genetic alterations included CDKN2A/B deletion, PTEN mutation, TP53 mutation, CDK4 amplification, and MDM2 amplification. Our observations suggest that F3T3-positive GBM is a distinct molecular subgroup of the IDH-wildtype GBM. Both clinicians and pathologists should consider this rare entity in the differential diagnosis of diffuse astrocytic glioma to make an accurate diagnosis and to ensure appropriate therapeutic management.

Narazaciclib, a Differentiated CDK4/6 Antagonist, Prolongs Cell Cycle Arrest and Metabolomic Reprogramming, Enabling Restoration of Ibrutinib Sensitivity in Btki-Resistant Mantle Cell Lymphoma

Bruton tyrosine kinase inhibitors (BTKi) have transformed the therapeutic landscape of mantle cell lymphoma (MCL); however, primary and acquired resistance to these agents remains a challenge. Previous studies have suggested that narazaciclib (ON123300), a second-generation, orally bioavailable and clinical-stage CDK4/6 inhibitor (CDKi), may trigger cell cycle arrest and significant tumor growth inhibition (TGI) in BTKi-resistant MCL. We compared the efficacy and safety profiles of narazaciclib with three health authority-approved CDKi (palbociclib, abemaciclib or ribociclib) in association with covalent (ibrutinib, acalabrutinib) and non-covalent (pirtobrutinib, ARQ-531) BTKi, across a panel of 10 MCL cell lines with distinct sensitivity to the first-in-class BTKi, ibrutinib. We integrated RNA sequencing and gene set enrichment analysis (GSEA) coupled to phospho-proteomics and kinase-substrate enrichment analysis (KSEA) to unravel the molecular bases of BTKi-CDKi drug interaction in MCL. CellTiter-Glo proliferation assay, FACS-mediated quantification of cell cycle and apoptosis, RT-PCR and western blot approaches followed by Seahorse-mediated metabolic assays were carried out for validation purposes. Finally, we evaluated the safety and efficacy of narazaciclib/ibrutinib combo in vivo in three immune-competent chicken embryo chorioallantoic membrane (CAM) MCL xenograft models. We found that narazaciclib exhibited the highest antitumor activity among MCL cell lines (mean IC 50: 3.61 ± 2.1 µM), regardless of the sensitivity of these to ibrutinib. Although there was no correlation between CDKi sensitivity and direct repression of the CDK4/CDK6-pRb pathway in MCL, transcriptomic and phenotypic analyses revealed a predominant downregulation of E2F target genes and G2/M checkpoint response upon narazaciclib treatment. This feature was linked to intracellular accumulation of p21, p16, and phospho-p27, decreased mitotic index, G1 cell cycle blockade, and apoptosis onset. When combined with ibrutinib, but not with the second-generation acalabrutinib, narazaciclib achieved significant synergistic antitumor activity in both BTKi-sensitive and BTKi-resistant cells. The combination was not associated with improved apoptosis, but rather with a slight but constant augmentation in G1 phase blockade and the down-modulation of cell cycle-associated transcriptome, although similar features were found when substituting narazaciclib with abemaciclib. The integration of transcriptomic and phospho-proteomic synergistic signatures further revealed that narazaciclib-ibrutinib combo modulated signatures related to DNA repair, P53 signaling, and glycolytic activity. Accordingly, in this model, narazaciclib/ibrutinib-exposed cells underwent a metabolic switch from glycolytic to oxidative phosphorylation (OxPhos) phenotype accompanied by intracellular accumulation of mitochondria and increased mtDNA copy number. This switch appeared to be specific to MCL cells rendered refractory to ibrutinib upon activation of alternative NFkB signaling, as it was not found in MCL-BTKmut cells. In vivo, while narazaciclib single agent achieved a moderate TGI in the CAM model, the narazaciclib/ibrutinib combo reduced tumor spreading by 65% and allowed a 50% reduction in malignant B cell infiltration into host bone marrow, with no detectable toxicity. In conclusion, our findings demonstrate that narazaciclib is safe and effective as a single agent in preclinical models of MCL, including BTKi-resistant cases. Its combination with ibrutinib achieved a synergistic tumoricidal effect in vitro and in vivo, accelerating cell cycle blockade and reverting the metabolic reprogramming characterizing MCL refractoriness to BTKi therapy.

The radioprotectant nano-genistein enhances radiotherapy efficacy of lung tumors in mice.

Radiotherapy for non-small cell lung cancer (NSCLC) can be dose-limiting due to treatment-related toxicities. Genistein has been shown to be a robust radioprotective agent in preclinical models. A novel genistein oral nanosuspension formulation (nano-genistein) has demonstrated efficacy in mitigating radiation-induced lung damage in preclinical animal models. However, while those studies have confirmed that nano-genistein can protect normal lung tissue from radiation-induced toxicities, no studies have assessed the effect of nano-genistein on lung tumors. Here, we evaluated the impact of nano-genistein on the efficacy of radiation treatment of lung tumors in a mouse xenograft model. Two separate studies were conducted utilizing human A549 cells implanted either dorsally within the upper torso or in the flank. Daily oral administration of nano-genistein (200 or 400 mg/kg/day) occurred prior to and after exposure to a single dose of thoracic or abdominal 12.5 Gy radiation. Tumor growth was monitored twice weekly, nano-genistein treatment continued for up to 20 weeks and histopathology of tissues was completed post euthanasia. Continuous nano-genistein dosing was safe across all study groups in both studies. Animals receiving nano-genistein better maintained body weight following irradiation compared to corresponding vehicle treated animals. Animals that received nano-genistein also had reduced tumor growth and improved normal lung histopathology compared to those receiving vehicle suggesting that nano-genistein does not protect tumors from radiotherapy but is radioprotective of the lungs. There were no treatment-related histopathological findings noted in the skin adjacent to the tumor, esophagus, or uterus. These results, including the safety following extended dosing, support the continued evaluation of nano-genistein as an adjunctive treatment for patients with NSCLC undergoing radiotherapy and serve as the basis of a phase 1b/2a multicenter clinical trial.

Abstract LB301: Molecular pharmacology and broad synergy of the novel ATR inhibitor M1774 with DNA damaging anticancer agents

Abstract Ataxia telangiectasia and Rad3-related (ATR) checkpoint kinase orchestrates DNA damage response and repair pathways stimulated by replicative stresses. Recent studies have established that pharmacological inhibition of ATR is clinically promising. As M1774 is an oral ATR inhibitor in clinical development, we explored the molecular basis by which M1774 induces cancer cell death. As a single agent, we found that M1774 suppresses cancer cell viability at nanomolar concentrations with a potency higher than ceralasertib and berzosertib, but lower than gartisertib (M4344) and elimusertib in the small cell lung cancer (SCLC) cell lines H146, H82, and DMS114. We found that M1774 efficiently suppresses the ATR/CHK1 checkpoints. While M1774 alone induced apoptosis and G2/M cell cycle arrest at micromolar concentrations, at a non-toxic low dose, M1774 enhanced TOP1 inhibitor-mediated cancer cell death by preventing replication arrest and inducing DNA damage detected by EdU and γH2AX staining. Tandem mass tagging (TMT) coupled with mass spectrometry revealed that M1774 combined with SN-38 increases the expression of replication-related proteins (TIPIN, CDC45, TIMELESS, and RPA1) and G2/M-related proteins (PLK1 and CCNB1). To establish the synergistic combinations of M1774 with clinical anticancer DNA damaging agents in preclinical models, we performed experiments in cancer cell lines, patient-derived organoids, and xenograft models. Low doses of M1774 significantly synergized with the clinical TOP1 inhibitor SN-38, the TOP2 inhibitor etoposide, cisplatin, and the PARP inhibitor talazoparib in SCLC cell lines. We also found that M1774 significantly reversed chemoresistance to DNA-damaging agents in cancer cells lacking SLFN11 expression, suggesting that SLFN11 expression can be utilized for combination therapy with M1774 as a biomarker. The synergistic efficacy between M1774 and DNA-damaging agents was confirmed in SCLC patient-derived organoids, colon cancer patient-derived organoids, and H82 SCLC xenografts. Together, these results provide insights into the molecular mechanism and potential combination strategies for M1774 in cancer therapy. Citation Format: Ukhyun Jo, Yasuhiro Arakawa, Astrid Zimmermann, Daiki Taniyama, Makito Mizunuma, Lisa M Jenkins, Suresh Kumar, Frank T Zenke, Yves Pommier. Molecular pharmacology and broad synergy of the novel ATR inhibitor M1774 with DNA damaging anticancer agents [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 LB301.

Cancer Cell-Specific Fluorescent Prodrug Delivery Platforms.

Targeting cancer cells with high specificity is one of the most essential yet challenging goals of tumor therapy. Because different surface receptors, transporters, and integrins are overexpressed specifically on tumor cells, using these tumor cell-specific properties to improve drug targeting efficacy holds particular promise. Targeted fluorescent prodrugs not only improve intracellular accumulation and bioavailability but also report their own localization and activation through real-time changes in fluorescence. In this review, efforts are highlighted to develop innovative targeted fluorescent prodrugs that efficiently accumulate in tumor cells in different organs, including lung cancer, liver cancer, cervical cancer, breast cancer, glioma, and colorectal cancer. The latest progress and advances in chemical design and synthetic considerations in fluorescence prodrug conjugates and how their therapeutic efficacy and fluorescence can be activated by tumor-specific stimuli are reviewed. Additionally, novel perspectives are provided on strategies behind engineered nanoparticle platforms self-assembled from targeted fluorescence prodrugs, and how fluorescence readouts can be used to monitor the position and action of the nanoparticle-mediated delivery of therapeutic agents in preclinical models. Finally, future opportunities for fluorescent prodrug-based strategies and solutions to the challenges of accelerating clinical translation for the treatment of organ-specific tumors are proposed.

Abstract 6276: SKL27969, an oral selective PRMT5 inhibitor, sensitizes the effect of DNA-damaging agents in preclinical models of multiple solid tumors

Abstract Background: Protein arginine methyltransferase 5 (PRMT5) is overexpressed in various human malignancies and induces epigenetic and post-translational changes, which have a significant impact on cell growth, proliferation, apoptosis, and DNA damage repair. SKL27969 is a potent and selective brain-penetrating PRMT5 inhibitor demonstrating antitumor activity in the preclinical models of glioblastoma (GBM) and non-small cell lung cancer (NSCLC) and triple-negative breast cancer (TNBC) brain metastasis models. In this study, we evaluated the antitumor activity of SKL27969 alone or in combination with DNA-damaging agents in various cancer models. Methods: Cell cycle analysis, apoptosis, proliferation, and invasion assays were conducted to determine in vitro profiles of SKL27969. In vivo efficacy of SKL27969 was evaluated in human cancer cell line-derived xenograft (CDX) or patient-derived xenograft (PDX) models. Immunohistochemistry and RNA-sequencing analysis in tumor samples from animal models were conducted to confirm the in vivo mechanism of action (MoA). In vitro synergistic effects of SKL27969 with combination partner drugs were analyzed using Combenefit software. Results: SKL27969 exhibits strong anti-proliferative effect by inducing cell cycle arrest and apoptosis and also inhibits invasion of cancer cells. An evaluation of SKL27969 in a panel of over 100 cancer cell lines revealed a broad spectrum of anti-proliferative activity in various cancer types, and an especially more sensitive response in cell lines harboring genetic alterations in the mitotic DNA damage checkpoint, DNA repair, or RNA processing pathways. Administration of SKL27969 demonstrated significant tumor growth inhibition, with a decrease in tumor symmetric dimethylarginine (SDMA) in NSCLC and TNBC subcutaneous xenograft models. Transcriptome and immunohistochemical analysis of SKL27969-treated tumors revealed that the cell cycle checkpoint pathways and DNA damage repair genes were downregulated, supporting the rationale for combination treatment with DNA-damaging agents such as chemotherapeutic agents. Robust antitumor effects were observed after treatment with SKL27969 in combination with paclitaxel or gemcitabine in NSCLC PDX or pancreatic cancer CDX models. Further ex vivo studies to confirm the in vivo MoA of this synergism, and in vivo combination studies of SKL27969 with standard chemotherapeutic agents in other solid cancer CDX models, are ongoing. Conclusion: This is the first preclinical study that suggests the therapeutic potential of SKL27969 in combination with currently approved DNA-damaging agents, and supports further clinical investigation of SKL27969’s role in improving the therapeutic benefit of standard therapies. Citation Format: Mijin Moon, Yongje Shin, Soyoung Ki, Jungtae Na, Ho Yeon Lee, Ilkyoo Koh, Beomjin Hong, Jiyeon Yun, Janice Laramy, Vijaykumar Vashi, Sook-Kyung Park. SKL27969, an oral selective PRMT5 inhibitor, sensitizes the effect of DNA-damaging agents in preclinical models of multiple solid tumors. [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 6276.

Abstract 5974: Synergistic activity of the CDK4/6 antagonist narazaciclib (ON123300) with irreversible BTK inhibition in ibrutinib-resistant mantle cell lymphoma

Abstract Bruton tyrosine kinase inhibitors (BTKi) have transformed the therapeutic landscape of B-cell lymphoma including the aggressive mantle cell lymphoma (MCL) subtype, although primary and acquired resistance is frequently observed. Interestingly, preliminary results have suggested that the second-generation, orally bioavailable and clinical-stage CDK4/6 inhibitor, ON123300 (narazaciclib), may be effective in preclinical models of BTKi-resistant MCL. We compared the efficacy and safety of ON123300 vs the approved CDK inhibitors palbociclib, abemaciclib or ribociclib, in association with various BTKi, in a panel of 10 MCL cell lines with distinct sensitivity to the first-in-class BTKi, ibrutinib, or the second generation acalabrutinib. We evaluated the effects of these combinations by CellTiter-Glo proliferation assay, FACS-mediated analysis of cell cycle and apoptosis, RT-PCR and western blot. Efficacy and safety of ON123300 in vivo was evaluated in a chicken embryo chorioallantoic membrane (CAM) xenograft model of MCL. We observed that ON123300 exhibited a significant antitumor activity in MCL cell lines independently of their sensitivity to ibrutinib, with IC50 at 72h ranging from 0.7 to 7.1µM (mean: 3.61±2.1µM), while it achieved a 32% tumor growth inhibition, with no detectable toxicity, in the CAM-MCL model. In vitro, ON123300 demonstrated a superior activity than palbociclib and ribociclib, and a similar effect that abemaciclib. Interestingly, ON123300 exhibited an antitumor activity comparable to ibrutinib but was more effective than acalabrutinib. ON123300 single agent treatment repressed several positive regulators of the G2/M cell cycle phase and triggered the accumulation of the CDK inhibitors p21, p16, and phospho-p27, with the consequent loss of phospho-Histone H3 and phospho-CDK2. Accordingly, ON123300 treatment evoked a 20-35% increase in G1 cell cycle fraction at 24h, which preceded the ignition of mitochondrial apoptosis. When combined with ibrutinib, rather than with acalabrutinib, ON123300 exhibited a significant antitumor activity with synergistic combination indexes in both BTK-sensitive and BTK-resistant cell lines. This phenomenon was associated with a slight but constant (+10-15%) augmentation of G1 blockade, histone H3/CDK2 dephosphorylation and p27/p16 accumulation in cells exposed to ibrutinib-ON123300 combination, with no detectable potentiation of apoptosis. In conclusion, ON123300 is safe and effective as single agent in preclinical models of MCL, including BTKi-resistant cases. Due to its complete distinct MoA from BTKi involving the direct modulation of cell cycle, ON123300, but not abemaciclib or palbociclib, can achieve significant synergistic activity in combination with ibrutinib, and in lower extent with acalabrutinib, especially in BTKi-resistant MCL cases. Citation Format: Nuria Profitos-Peleja, Marcelo L. Ribeiro, Adar Makovski Silverstein, Stephen Cosenza, Gaël Roué. Synergistic activity of the CDK4/6 antagonist narazaciclib (ON123300) with irreversible BTK inhibition in ibrutinib-resistant mantle cell lymphoma [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 5974.

Pre-clinical evidence of a dual NADPH oxidase 1/4 inhibitor (setanaxib) in liver, kidney and lung fibrosis.

Fibrosis describes a dysregulated tissue remodelling response to persistent cellular injury and is the final pathological consequence of many chronic diseases that affect the liver, kidney and lung. Nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase (NOX) enzymes produce reactive oxygen species (ROS) as their primary function. ROS derived from NOX1 and NOX4 are key mediators of liver, kidney and lung fibrosis. Setanaxib (GKT137831) is a first-in-class, dual inhibitor of NOX1/4 and is the first NOX inhibitor to progress to clinical trial investigation. The anti-fibrotic effects of setanaxib in liver, kidney and lung fibrosis are supported by multiple lines of pre-clinical evidence. However, despite advances in our understanding, the precise roles of NOX1/4 in fibrosis require further investigation. Additionally, there is a translational gap between the pre-clinical observations of setanaxib to date and the applicability of these to human patients within a clinical setting. This narrative review critically examines the role of NOX1/4 in liver, kidney and lung fibrosis, alongside the available evidence investigating setanaxib as a therapeutic agent in pre-clinical models of disease. We discuss the potential clinical translatability of this pre-clinical evidence, which provides rationale to explore NOX1/4 inhibition by setanaxib across various fibrotic pathologies in clinical trials involving human patients.

STING Agonists in Head and Neck Squamous Cell Carcinoma.

Despite the development of new treatment paradigms and improved biologic understanding of head and neck squamous cell carcinoma (HNSCC), therapeutic resistance remains a substantial problem, and novel treatment approaches are needed. Stimulator of interferon genes (STING) is a critical regulator of the antitumor response through regulation of both immune-dependent and tumor-intrinsic mechanisms. As such, the STING pathway has emerged as a rational pharmacologic target leading to the development of multiple STING agonists. These compounds have impressive preclinical efficacy as single agents and with PD-1 (programmed death-1) axis agents. However, clinical evaluation in this context has yet to show substantial efficacy. In contrast to monotherapy approaches, activation of STING in combination with DNA-damaging agents has been shown to enhance the effect of these agents in preclinical models and represents a promising approach to improve outcomes in patients with HNSCC. In this review, we will discuss the preclinical and clinical data supporting the use of STING agonists and highlight potential avenues of exploration to unlock the potential of these agents in HNSCC.

Abstract LB530: A potent and selective small molecule antagonist of PD-L1 ABSK043 demonstrates significant anti-tumor efficacy in combination with other agents in preclinical models

Abstract Immunotherapy has revolutionized cancer treatment in the last decade. Several monoclonal PD-1 and PD-L1 antibodies have been approved for various cancers. Unlike antibodies, small molecule inhibitors may offer potential advantages in oral dosing, adjustable control of drug exposure, improved tumor penetration and many other aspects. Therefore, small molecule antagonist which can efficiently abolish interaction of PD-1 and PD-L1 may render a novel alternative treatment approach with potentially improved clinical benefits. ABSK043, an oral small molecule inhibitor of PD-L1 discovered by us, has entered into clinical Phase I in 2021. Preclinically, ABSK043 has shown significant tumor growth inhibition as a single agent in multiple models. To explore potential synergy of ABSK043 with other therapeutic agents, in vivo combination experiments were conducted. In this work, we present in vivo combination results for ABSK043 with several therapeutic agents such as a VEGFR inhibitor axitinib, or carboplatin, a key component of the widely used CRC standard-of care chemotherapy treatment regimen, as well as other immune-oncology agents. These combinations demonstrated strong in vivo synergy in tumor mouse syngeneic models. Taken together, these data for the first time demonstrated combination synergy of a small molecule PD-L1 inhibitor with other agents and pave the road for potential clinical evaluation of combination treatment of ABSK043 with these agents in patients. Citation Format: Haiyan Ying, Yongxian Zhang, Fei Yang, Wenqun Xin, Jiaqi Song, Zhui Chen. A potent and selective small molecule antagonist of PD-L1 ABSK043 demonstrates significant anti-tumor efficacy in combination with other agents in preclinical models [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 LB530.

Cold atmospheric pressure plasma treatment combined with starvation increases autophagy and apoptosis in melanoma invitro and in vivo.

Despite advances in therapy, malignant melanoma remains a fatal disease. Among several emerging approaches to combat cancer, cold atmospheric pressure plasma (CAP) has shown promising results as a novel antitumor agent in preclinical models so far. The technology mainly relies on the emittance of various reactive oxygen and nitrogen species (ROS/RNS) that are tumor-toxic at high concentrations. Moreover, malignant melanoma has a metabolic dimension that can be targeted by mild starvation. To this end, we investigated the combined effect of starvation and CAP treatment on melanoma in vitro and in vivo. In vitro, starvation+CAP led to cell morphology changes, decreased metabolic activity and increased lipid peroxidation accompanied by apoptosis and DNA fragmentation in murine B16 melanoma cells but not murine non-malignant L929 fibroblasts. This was paralleled by increased apoptosis (Bax, Bcl-2 and Caspase-3) and autophagy (Lc3 and Atg5)-related gene expression. In vivo, starvation reduced tumor burden. Combination with CAP treatment augmented this effect significantly, albeit there was no difference of combination treatment to CAP exposure alone. Interestingly, there was an overall greater increase of Lc3 and Atg5 in the tumor tissue compared to CAP exposure alone, while starvation-induced autophagy-related gene expression was similar to in the combination group. These data collectively suggest that CAP-derived ROS/RNS treatment and autophagy-induction augment antitumor effects in malignant melanoma in vitro and in vivo.

Abstract P208: Synergistic antitumor activity of lisaftoclax (APG-2575) and alrizomadlin (APG-115) through dual targeting of BCL-2/MDM2-P53 apoptotic pathways in preclinical models of acute myeloid leukemia

Abstract Background: In many hematologic malignancies, BCL-2 is overexpressed and is a viable therapeutic target. In relapsed or refractory acute myeloid leukemia (R/R AML), BCL-2 inhibitor venetoclax as a single agent has limited activity, thereby necessitating combination treatments, some of which are actively under clinical development. In addition, the mutation rate of TP53 is rare in AML, and the frequency of MDM2 overexpression is high, representing an opportunity for pharmacologic intervention of the MDM2-P53 apoptosis pathway. Synergistic effects of MDM2 inhibitor idasanutlin and venetoclax have been reported in preclinical models of TP53 wild-type AML (Pan et al, Cancer Cell 2017). Lisaftoclax (APG-2575) and alrizomadlin (APG-115) are novel BCL-2 and MDM2 inhibitors, respectively. They show unique pharmacological properties as well as clinical activity and tolerable safety profiles in patients with hematologic or solid malignancies (Tolcher et al, J Clin Oncol 2021:2506; Ailawadhi et al, J Clin Oncol 2021:7502). Here, we examined the effects of combined lisaftoclax and alrizomadlin in preclinical models of AML. Materials and Methods: AML cell lines and mouse xenograft models were employed. Antiproliferative activity was measured by CellTiter-Glo luminescent cell viability assay. Apoptosis was evaluated by annexin V/propidium iodide staining and flow cytometry. Meso-Scale Discovery ELISA assay and western blot analyses were used to characterize the mechanisms of the synergistic effects of this combination. In animal studies, clinically relevant doses of lisaftoclax were employed. A pulsed high-dose regimen of alrizomadlin was used to achieve best efficacy and manage on-target toxicity. Results: In TP53 wild-type AML cell lines MOLM-13, MV-4-11, and OCI-AML-3, both single-agent lisaftoclax and alrizomadlin exerted apoptogenic activity. The combination had synergistic apoptogenic and antiproliferative activity. In subcutaneous xenograft models derived from MV-4-11 and OCI-AML-3 cells, the combination substantially inhibited tumor growth relative to the impact observed with either single agent. In a systemic xenograft model derived from MOLM-13 cells, the combination significantly (P < .05) extended the life span of tumor-bearing mice by 135% to 237% compared to that of tumor-bearing mice treated with lisaftoclax or alrizomadlin alone, which resulted in extensions of 4% to 26% and 41% to 95%, respectively. Synergistic anti-leukemic activity was confirmed in a patient-derived systemic AML model. Mechanistically, the combination synergistically downregulated anti-apoptotic proteins MCL-1 and BCL-xL and primed AML cells to apoptosis induced by lisaftoclax. Conclusions: We show a significant synergy of lisaftoclax and alrizomadlin and novel mechanisms associated with the combination of these agents in preclinical models of TP53 wild-type AML. These data support investigation into the clinical outcomes of the combination treatment in patients with TP53 wild-type AML. Citation Format: Douglas D. Fang, Qiuqiong Tang, Qixin Wang, Na Li, Feng Zhou, Guoqin Zhai, Yan Yin, Dajun Yang, Yifan Zhai. Synergistic antitumor activity of lisaftoclax (APG-2575) and alrizomadlin (APG-115) through dual targeting of BCL-2/MDM2-P53 apoptotic pathways in preclinical models of acute myeloid leukemia [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P208.

Cannabinoid Cancer Biology and Prevention.

Plant-based, synthetic, and endogenous cannabinoids have been shown to control a diverse array of biological processes, including regulation of cell fate across cancers. Their promise as broad-based antitumor agents in preclinical models has led to the initiation of pilot clinical trials. Session 5 of the National Cancer Institute's Cannabis, Cannabinoids and Cancer Research Symposium provides an overview of this research topic. Overall, the presentations highlight cannabinoid signal transduction and specific molecular mechanisms underlying cannabinoid antitumor activity. They also demonstrate the broad-based antitumor activity of the plant-based, synthetic, and endogenous cannabinoid compounds. Importantly, evidence is presented demonstrating when cannabinoids may be contraindicated as a treatment for cancer, as in the case of human papilloma virus-meditated oropharynx cancer or potentially other p38 MAPK pathway-driven cancers. Finally, it is discussed that a key to advancing cannabinoids into the clinic is to conduct well-designed, large-scale clinical trials to determine whether cannabinoids are effective antitumor agents in cancer patients.

Manganese-Doped N-Hydroxyphthalimide-Derived Carbon Dots—Theranostics Applications in Experimental Breast Cancer Models

Background: Theranostics, a novel concept in medicine, is based on the use of an agent for simultaneous diagnosis and treatment. Nanomaterials provide promising novel approaches to theranostics. Carbon Dots have been shown to exhibit anti-tumoral properties in various cancer models. The aim of the present study is to develop gadolinium, Fe3+, and Mn2+-doped N-hydroxyphthalimide-derived Carbon Dots. The resulted doped Carbon Dots should preserve the anti-tumoral properties while gaining magnetic resonance imaging properties. Methods: Normal and cancer cell lines have been treated with doped Carbon Dots, and the cell viability has been measured. The doped Carbon Dots that exhibited the most prominent anti-tumoral effect accompanied by the lowest toxicity have been further in vivo tested. Magnetic resonance imaging evaluates both in vitro and in vivo the possibility of using doped Carbon Dots as a contrast agent. Results: According to the results obtained from both the in vitro and in vivo experimental models used in our study, Mn2+-doped Carbon Dots (Mn-CDs-NHF) exhibit anti-tumoral properties, do not significantly impair the cell viability of normal cells, and reduce lung metastasis and the volume of mammary primary tumors while allowing magnetic resonance imaging. Conclusions: Our findings prove that Mn-CDs-NHF can be used as theranostics agents in pre-clinical models.