Patient-derived Xenograft Mouse Research Articles

Targeting of FSP1 regulates iron homeostasis in drug-tolerant persister head and neck cancer cells via lipid-metabolism-driven ferroptosis.

Research has demonstrated that some tumor cells can transform into drug-tolerant persisters (DTPs), which serve as a reservoir for the recurrence of the disease. The persister state in cancer cells arises due to temporary molecular reprogramming, and exploring the genetic composition and microenvironment during the development of head and neck squamous cell carcinoma (HNSCC) can enhance our comprehension of the types of cell death that HNSCC, thus identifying potential targets for innovative therapies. This project investigated lipid-metabolism-driven ferroptosis and its role in drug resistance and DTP generation in HNSCC. High levels of FSP1 were discovered in the tissues of patients who experienced relapse after cisplatin treatment. RNA sequencing indicated that a series of genes related to lipid metabolism were also highly expressed in tissues from these patients. Consistent results were obtained in primary DTP cells isolated from patients who experienced relapse. The Cancer Genome Atlas database confirmed this finding. This revealed that the activation of drug resistance in cancer cells is influenced by FSP1, intracellular iron homeostasis, and lipid metabolism. The regulatory roles of ferroptosis suppressor protein 1 (FSP1) in HNSCC metabolic regulation were investigated. We generated human oral squamous cell carcinoma DTP cells (HNSCC cell line) to cisplatin and observed higher expression of FSP1 and lipid-metabolism-related targets in vitro. The shFSP1 blockade attenuated HNSCC-DTP cell stemness and downregulated tumor invasion and the metastatic rate. We found that cisplatin induced FSP1/ACSL4 axis expression in HNSC-DTPC cells. Finally, we evaluated the HNSCC CSC-inhibitory functions of iFSP1 (a metabolic drug and ferroptosis inducer) used for neo-adjuvant chemotherapy; this was achieved by inducing ferroptosis in a patient-derived xenograft mouse model. The present findings elucidate the link between iron homeostasis, ferroptosis, and cancer metabolism in HNSCC-DTP generation and acquisition of chemoresistance. The findings may serve as a suitable model for cancer treatment testing and prediction of precision treatment outcomes. In conclusion, this study provides clinically oriented platforms for evaluating metabolism-modulating drugs (FSP1 inhibitors) and new drug candidates of drug resistance and ferroptotic biomarkers.

Patient-Derived Orthotopic Xenograft Models for High-Grade Pediatric Brain Cancers.

Patient-derived orthotopic xenograft (PDOX) mouse models are considered the gold standard for evidence-based preclinical research in pediatric neuro-oncology. This protocol describes the generation of PDOX models by intracranial implantation of human pediatric brain cancer cells into immune-deficient mice, and their continued propagation to establish cohorts of animals for preclinical research.

A patient-derived xenograft mouse platform from epithelioid glioblastoma provides possible druggable screening and translational study

A patient-derived xenograft mouse platform from epithelioid glioblastoma provides possible druggable screening and translational study

BLU-945, a potent and selective next-generation EGFR TKI, has antitumor activity in models of osimertinib-resistant non-small-cell lung cancer.

Despite the availability of several epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), most patients with non-small-cell lung cancer (NSCLC) eventually develop resistance to these agents. Notably, EGFR_C797S mutations confer resistance to the third-generation EGFR-TKI osimertinib and no approved post-osimertinib targeted pharmacology options are currently available. BLU-945 is a novel, reversible, and orally available next-generation EGFR-TKI that selectively targets EGFR-activating (EGFRm) and resistance mutations (including EGFR_C797S) with nanomolar potency while sparing wild-type EGFR in vitro. In vitro activity of BLU-945 as a single agent and in combination with osimertinib was tested in engineered EGFR-mutant cell lines as well as patient-derived cells and patient-derived organoids. In vivo activity was evaluated in osimertinib-resistant patient-derived xenograft mouse models. Three patient cases from the global, first-in-human, phase I/II SYMPHONY trial (NCT04862780) demonstrating the clinical efficacy of BLU-945 were reported. In vitro BLU-945 demonstrated inhibited cell viability and growth of EGFR-mutant/osimertinib-resistant cell lines. BLU-945 demonstrated in vivo tumor shrinkage in osimertinib-resistant models of NSCLC (osimertinib second line: EGFR_L858R/C797S and third line: EGFR_ex19del/T790M/C797S and L858R/T790M/C797S) both as monotherapy and in combination with osimertinib. BLU-945 also demonstrated tumor shrinkage in patients from the SYMPHONY trial. Our findings demonstrate the preclinical and early clinical activity of BLU-945 in EGFRm NSCLC progressing on previous EGFR-TKIs.

Neutralization of p40 Homodimer and p40 Monomer Leads to Tumor Regression in Patient-Derived Xenograft Mice with Pancreatic Cancer.

Pancreatic cancer is a highly aggressive cancer with a high mortality rate and limited treatment options. It is the fourth leading cause of cancer in the US, and mortality is rising rapidly, with a 12% relative 5-year survival rate. Early diagnosis remains a challenge due to vague symptoms, lack of specific biomarkers, and rapid tumor progression. Interleukin-12 (IL-12) is a central cytokine that regulates innate (natural killer cells) and adaptive (cytokine T-lymphocytes) immunity in cancer. We demonstrated that serum levels of IL-12p40 homodimer (p402) and p40 monomer (p40) were elevated and that of IL-12 and IL-23 were lowered in pancreatic cancer patients compared to healthy controls. Comparably, human PDAC cells produced greater levels of p402 and p40 and lower levels of IL-12 and IL-23 compared to normal pancreatic cells. Notably, neutralization of p402 by mAb a3-1d and p40 by mAb a3-3a induced the death of human PDAC cells, but not normal human pancreatic cells. Furthermore, we demonstrated that treatment of PDX mice with p402 mAb and p40 mAb resulted in apoptosis and tumor shrinkage. This study illustrates a new role of p402 and p40 monomer in pancreatic cancer, highlighting possible approaches against this deadly form of cancer with p402 and p40 monomer immunotherapies.

Abstract A030: Treatment with sustained-release anagrelide reduces tumor volume and has antiproliferative effects in a patient-derived GIST xenograft mouse model

Abstract Anagrelide is a phosphodiesterase 3A inhibitor that is used to treat essential thrombocythemia. The drug stabilizes the interaction of PDE3A and Schlafen 12 (SLFN12), resulting in complex stabilization, activation of SLFN12 RNase activity and cytotoxic effects in cancer cells. Gastrointestinal stromal tumors (GIST) exhibit high levels of PDE3A expression compared to other cancers or healthy tissue. Orally administered anagrelide has shown antitumor effects in patient-derived GIST xenograft (PDX) mouse models. In this study, we investigated the efficacy of subcutaneously administered, sustained-release anagrelide in UZLX-GIST2B, a PDX mouse model characterized by a KIT mutation in exon 9 and typical dose-dependent imatinib sensitivity. We assessed changes in tumor volume and evaluated histological drug responses including hyalinization, fibrosis, myxoid generation, and tumor necrosis. Anagrelide was administered either orally (2.5 mg/kg, twice a day) or subcutaneously (35 mg/kg and 70 mg/kg, every fourth day) for a duration of 11 days. Treatments with both 35 mg/kg and 70 mg/kg doses resulted in a significant reduction in average tumor volume compared to untreated control mice (both doses 25% vs.129%, P < 0.001) or mice treated with oral anagrelide (25% vs. 61%, P =0 .08, P < 0.05, respectively). The histological response in tumor tissue was positively correlated with dose level, and tumors treated with the highest dose exhibited grade 3 to 4 responses in all cases. These results suggest that sustained-release anagrelide holds promise as a therapeutic option for the treatment of GIST. Further preclinical studies are warranted to investigate the pharmacokinetics and toxicity of this treatment approach. Citation Format: Kirsi Toivanen, Luna De Sutter, Agnieszka Wozniak, Tom Böhling, Patrick Schöffski, Harri Sihto. Treatment with sustained-release anagrelide reduces tumor volume and has antiproliferative effects in a patient-derived GIST xenograft mouse model [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A030.

Fucoxanthin Inhibits Development of Sigmoid Colorectal Cancer in a PDX Model With Alterations of Growth, Adhesion, and Cell Cycle Signals.

Fucoxanthin (Fx), a dietary marine xanthophyll, exerts potent anticancer effects in various colorectal cancer (CRC) animal models. However, therapeutic effects of Fx in human cancer tissues remain unclear. A patient-derived xenograft (PDX) mouse model transplanted with cancer tissues from patients is widely accepted as the best preclinical model for evaluating the anticancer potential of drug candidates. Herein, we investigated the anticancer effects of Fx in PDX mice transplanted with cancer tissues derived from a patient with CRC (CRC-PDX) using LC-MS/MS- and western blot-based proteome analysis. The tumor in the patient with CRC was a primary adenocarcinoma (T3N0M0, stage II) showing mutations of certain genes that were tumor protein p53 (TP53), AT-rich interaction domain 1A (ARID1A), neuroblastoma RAS viral oncogene homolog (NRAS), and PMS1 homolog 2 (PMS2). Administration of Fx significantly suppressed the tumor growth (0.6-fold) and tended to induce differentiation in CRC-PDX mice. Fx up-regulated glycanated-decorin (Gc-DCN) expression, and down-regulated Kinetochore-associated protein DSN1 homolog (DSN1), phospho(p) focal adhesion kinase (pFAK)(Tyr397), pPaxillin(Tyr31), and c-MYC involved in growth, adhesion, and/or cell cycle, in the tumors of CRC-PDX mice than in control mice. Alterations in the five proteins were consistent with those in human CRC HT-29 and HCT116 cells treated with fucoxanthinol (FxOH, a major metabolite of Fx). Fx suppresses development of human-like CRC tissues, especially through growth, adhesion, and cell cycle signals.

Nanobody-based trispecific T cell engager (Nb-TriTE) enhances therapeutic efficacy by overcoming tumor-mediated immunosuppression

BackgroundT cell engagers (TCEs) have been established as an emerging modality for hematologic malignancies, but solid tumors remain refractory. However, the upregulation of programmed cell death 1 (PD-1) is correlated with T cell dysfunction that confer tumor-mediated immunosuppression. Developing a novel nanobody-based trispecific T cell engager (Nb-TriTE) would be a potential strategy to improve therapeutic efficacy.MethodsGiven the therapeutic potential of nanobodies (Nbs), we first screened Nb targeting fibroblast activation protein (FAP) and successfully generated a Nb-based bispecific T cell engager (Nb-BiTE) targeting FAP. Then, we developed a Nb-TriTE by fusing an anti-PD-1 Nb to the Nb-BiTE. The biological activity and antitumor efficacy of the Nb-TriTE were evaluated in vitro and in both cell line-derived and patient-derived xenograft mouse models.ResultsWe had for the first time successfully selected a FAP Nb for the generation of novel Nb-BiTE and Nb-TriTE, which showed good binding ability to their targets. Nb-TriTE not only induced robust tumor antigen-specific killing, potent T cell activation and enhanced T cell function in vitro, but also suppressed tumor growth, improved survival and mediated more T cell infiltration than Nb-BiTE in mouse models of different solid tumors without toxicity.ConclusionsThis novel Nb-TriTE provides a promising and universal platform to overcome tumor-mediated immunosuppression and improve patient outcomes in the future.

Probiotic-Derived Heptelidic Acid Demonstrates Therapeutic Efficacy Against Pediatric B-Cell Acute Lymphoblastic Leukemia

Introduction Pediatric B-cell acute lymphoblastic leukemia (B-ALL) is known to be sensitive to chemotherapy. However, approximately 15-20% of pediatric B-ALL patients experience relapse, and survival rates after relapse can drop to 5-10%. Therefore, new drugs need to be developed. Probiotics are live microorganisms with potential health benefits. Heptelidic acid (HA) from the probiotic Aspergillus oryzae has been shown to exert antitumor effects against pancreatic cancer, lung cancer, thyroid cancer, breast cancer and melanoma in vivo as well as in vitro. In this study, we assessed the antitumor effects of HA in B-ALL, which is the most common type of pediatric cancer. Methods Two B-ALL cell lines (JM1 and Reh), four CD34 + hematopoietic stem cells (HSCs) and three high-risk patient-derived B-ALL cells (s90: age < 1 year old, s96: age > 10 years old, s98: relapse) collected from the spleen or bone marrow of a patient-derived xenograft (PDX) model were used in this study. Cytotoxicity of HA was assessed by MTS assay. GAPDH activity and intracellular ATP contents were measured, as HA binds to cysteine 152 of GAPDH, a crucial region for its enzymatic activity and ATP production in glycolysis. The synergistic effects of HA with therapeutics, vincristine (VCR), doxorubicin (DXR) and L-asparaginase (L-Asp), were evaluated. GAPDH is involved not only in glucose metabolism but also in amino acid and fatty acids for energy production. Therefore, we analyzed whether HA exerted cytotoxicity under glucose, amino acid or fatty acid-deprived conditions in Reh cells. To analyze the underlying mechanism for HA's cytotoxicity against B-ALL, cell cycle analysis by flowcytometry, western blotting of cleaved PARP, caspase assays, and inhibitory assays using specific inhibitors for PCD mechanisms, such as RIPK-1 inhibitor, MLKL inhibitor, and autophagy inhibitor, were conducted. In vivo studies were done using a B-ALL PDX model. Oral administration of 0.5mg/kg HA was carried out for 21 days, while intraperitoneal injection of 0.15mg/kg VCR was performed once per week for 3 cycles in the HA-VCR combinational therapeutic efficacy study. Results HA exhibited significant cytotoxicity in JM1 (IC50: 169 ng/ml), Reh (IC50: 126.5 ng/ml), and three samples obtained from PDX mice (s90 IC50: 66.6 ng/ml, s96 IC50: 89.9 ng/ml, and s98 IC50: 275.6 ng/ml), while sparing CD34 + HSCs. GAPDH activity of CD34+ HSCs was significantly lower than both B-ALL cell lines and patient-derived cells. The cytotoxic effect of HA was associated with the reduction of GAPDH activity and ATP contents, suggesting glycolysis inhibition. Glucose deprivation induced significant reduction of cell viability, and HA showed the cytotoxicity in amino acid and fatty acid deprived media in Reh cells. Oral daily administration of HA prolonged the survival of the B-ALL PDX mice (34.5 days, n=8) compared to control mice (28 days, n=7) without causing body weight loss (p<0.05) (Figure 1A). The effects of over 0.5mg/kg of HA was confirmed by the reduction in GAPDH activity observed in leukemia cells isolated from the bone marrow. HA demonstrated synergistic effects when combined with chemotherapeutic agents, especially VCR. The combination therapy of HA and VCR resulted in improved survival outcomes in the B-ALL PDX model (49 days, n=5) compared to single-agent treatments (HA: 28 days, n=5, VCR: 40 days, n=5) and control groups (26 days, n=5) (p<0.05) (Figure 1B). Mechanistic studies revealed that HA induced PCD in B-ALL cells. HA treatment caused G2/M arrest (Control: 18.8%, HA: 27.6% in JM1; Control: 13.3%, HA: 18.3% in Reh), and this was accompanied by increased cleavage of PARP, a hallmark of PCD, in both cell lines. Moreover, the cytotoxicity of HA was attenuated by RIPK1 inhibition in JM1 and Reh. Conclusion We have demonstrated that B-ALL cells utilize glucose for their survival and HA is cytotoxic in B-ALL cells by disrupting glycolysis through the inhibition of GAPDH. The therapeutic efficacy of HA is further enhanced when combined with chemotherapeutic agents. The underlying mechanisms of HA involve the induction of RIPK-1 mediated PCD. This is the first study to demonstrate HA as a novel therapeutic agent for B-ALL.

Targeting Sumoylation Sensitizes Acute Myeloid Leukemia to Venetoclax Treatment

Acute myeloid leukemia (AML) is a hematopoietic cancer characterized by aberrant immature myeloid progenitor blasts in bone marrow and peripheral blood. Venetoclax (VEN), a BCL-2 inhibitor, is FDA-approved for AML treatment with hypomethylating agents (HMA). Despite the improvement of VEN and HMA, not all patients respond, and most patients develop resistance. This presents an urgent need for new therapies to overcome VEN resistance and enhance VEN efficacy. We propose SUMOylation inhibition as a novel therapy to address this need. SUMOylation regulates protein function by covalently attaching Small Ubiquitin-like MOdifier (SUMO) proteins to target proteins. SUMOylation plays an important role in tumor progression and immune response. Our study aims to evaluate the effects of SUMOylation inhibition on anti-AML activity of VEN and the mechanism. We firstly generated VEN-resistant cell lines Molm13-VR and MV411-VR by culturing Molm13 and MV4-11 cells in increasing doses of VEN. SUMO E1 (SAE2) and global SUMOylation levels were remarkably upregulated in VEN-resistant cell lines, suggesting SUMOylation plays a role in VEN resistance. We evaluated the antileukemic effects of TAK-981 (subasumstat), a novel and specific SUMO E1 inhibitor, alone and in combination with VEN, using AML cell lines and primary blasts isolated from refractory/relapsed (R/R) AML patients. Different AML cell lines and blast samples showed various sensitivities to VEN (IC 50 10nM ~ 5,000nM), but significant synergism was observed with TAK-981 and VEN in cell viability assay. TAK-981 synergized with VEN at inducing AML cell apoptosis determined by annexin-V staining with flow cytometry as well as increased levels of cleaved-PARP and cleaved caspase-3 by western blotting. The mechanism of action of VEN is dependent on BCL-2 mediated mitochondrial function and metabolism. We assessed mitochondrial membrane potential using TMRM probe. TAK-981 reduced mitochondrial membrane potential in both VEN-sensitive and resistant AML lines, further in combination with VEN. Because mitochondrial membrane potential is maintained by normal mitochondrial structure, we performed electron microscopy to determine mitochondrial structure. VEN had limited effect on mitochondria in resistant cells. However, TAK-981 induced abnormal ultrastructure mitochondria with fewer cristae, worsened by TAK-981+VEN combination. Since TAK-981 treatment caused mitochondrial structure defects, we determine the mitochondrial function using Seahorse XF assay. VEN decreased oxygen consumption rate (OCR), indicating inhibition of oxidative phosphorylation (OXPHOS), further suppressed by TAK-981. Metabolomic profiling by mass spectrometry indicated TAK-981+VEN treated AML cells displayed striking decreases in TCA cycle intermediates and reduced electron transport chain (ETC) activity. Pathway analysis of the metabolomics data revealed significant enrichment in amino acids metabolism. Notably, RNA-sequencing and GSEA analysis showed consistent findings that TAK-981+VEN showed suppressed signaling pathways in mitochondrial function, glycolysis and amino-acid metabolisms, indicating TAK-981 targeted mitochondrial metabolism to enhance VEN activity. We then determined whether TAK-981 enhanced antileukemic effect of VEN ex vivo and in vivo. TAK-981 synergized with VEN at reducing colony formation capacity in colony formation assay using leukemia stem cells (LSCs) isolated from relapse AML blasts. More importantly, TAK-981 showed remarkable therapeutic effect in patient-derived xenograft (PDX) mouse model engrafted with blasts isolated from R/R AML patients, and significantly synergized with VEN at extending mice survival in vivo. In conclusion, TAK-981 enhances the antileukemic activity of VEN by targeting mitochondria function and metabolism, offering a potent therapy for refractory/relapsed AML.

Identification of Mir-532-5p As a Reliable miRNA Reference in Acute Lymphoblastic Leukemia

In acute lymphoblastic leukemia (ALL) cure rates have reached >90%, however, therapy resistance and relapses occur. Hence, the major interest in leukemia research is the understanding of ALL biology and, based on that, the development of new targeted therapies. As patient-derived xenograft (PDX) mouse models, such as the NOD/SCID/human ALL xenotransplantation model, are systems resembling the human disease with leukemia engraftment and manifestation in bone marrow (BM), central nervous system (CNS), and spleen, they provide reliable models to study ALL biology and preclinically evaluate new treatment strategies. MicroRNAs (miRNAs) are described to post-transcriptionally regulate the expression of genes coding for critical regulators of leukemogenesis either functioning as tumor-suppressors or oncomirs. Moreover, ALL miRNA profiles can serve as biomarkers indicating disease stages and distribution and can be used for patient risk stratification. To reliably compare miRNA data across different samples and, most importantly, across various cohorts, data normalization with a constantly expressed miRNA reference in the respective samples is required. We aimed at identifying a reliable miRNA reference which shows a stable and constant expression in different ALL samples in a series of cell lines and PDX ALL specimens derived from different organ compartments. We analyzed the expression of 6 frequently used miRNA references (RNU6, RNU1A1, SNORD44, 5sRNA, miR-103a-3p and miR-532-5p) by real-time quantitative PCR. All together 9 ALL cell lines (NALM-6, REH, RS4;11, KOPN-8, UoCB6, RCH-ACV, MHH-CALL4, EU3, and HAL-01), 22 PDX specimens including CNS-, BM-, and spleen-derived ALL cells, and peripheral blood mononuclear cells of 6 healthy controls (HC-PBMCs) were investigated. Expression stabilities of the respective miRNA references were assessed applying four different algorithms (geNorm, BestKeeper, Normfinder, ∆CT). MiRNA scores were ranked according to their performance using RefFinder. Finally, the impact of using various miRNA references on data normalization was evaluated in different ALL and control samples. Analyzing the stability of miRNAs within the ALL cohort, we identified miR-532-5p in combination with miR-103a-3p (geNorm), miR-532-5p (BestKeeper and NormFinder), and miR-103a-3p followed by miR-532-5p (∆CT; mean standard deviation of miR-103a-3p and miR-532-5p: 2.215 and 2.220, respectively) as the most stably expressed miRNAs. Importantly, the RefFinder algorithm identified miR-532-5p as the most reliable reference. Next, we assessed the stability of miRNA expression in HC-PBMCs, and identified SNORD44 (NormFinder, BestKeeper, ∆CT) or SNORD44 in combination with RNU6 (geNorm) as the miRNAs showing the lowest variation. These data were further substantiated by using RefFinder which identified SNORD44 as the most reliable miRNA reference in HC-PBMCs. Interestingly, when we combined the cohorts of ALL and HC samples and applied RefFinder, miR-532-5p in combination with miR-103a-3p were identified as the most stable miRNAs. Last, we analyzed the influence of using expression levels of different miRNAs for data normalization. We assessed the expression of miR-181a-5p, a miRNA described to be frequently overexpressed in ALL cells as compared to HC-PBMCs and used expression data of different miRNAs for normalization: miR-532-5p (most stably expressed in ALL cohort), miR-532-5p/miR-103a-3p (combining the most stable miRNA references in ALL cohort and HCs), or SNORD44 (most stably expressed in HC-PBMCs). Interestingly and in line with its described upregulation in ALL, we identified a significant overexpression of miR-181a-5p in BM-derived PDX samples as compared to HC-PBMCs when using miR-532-5p or miR-532-5p/miR-103a-3p for data normalization. However, when SNORD44 was used as a reference, no differential expression of miR-181a-5p in HC-PBMCs and BM-ALL cells was found indicating a critical impact of the normalization reference. In summary, we identified miR-532-5p to be constantly expressed across different leukemia samples providing a reliable miRNA reference for data normalization in ALL miRNA expression studies. Moreover, these data clearly emphasize that the chosen reference critically depends on the cellular background of the specific samples and requires careful selection and verification within the respective sample types.

Development and Efficacy of a Novel Bromodomain and Extraterminal Domain Degrader K-256 in MYC/BCL2-Related Lymphoma

Background: Although intensive chemotherapy is widely used to treat MYC/BCL2-related lymphoma, the efficacy of this treatment modality remains limited and a novel treatment method targeting MYC and BCL2 is therefore desired. While the addition of the BH3 mimetic, venetoclax, to standard immunochemotherapy has shown efficacy in treating diffuse large B-cell lymphoma (DLBCL) with BCL2 expression, bromodomain and extraterminal domain (BET) inhibitors, which suppress MYC transcription, have shown limited efficacy in treating MYC-driven lymphomas. Recently, BET degraders have been developed that irreversibly degrade BET proteins and durably suppress MYC; these degraders show promising therapeutic potential. Method: To improve the prognosis of MYC/BCL2-related lymphoma, we developed a novel BET degrader, K-256, and explored its efficacy both in vitro and in vivo using preclinical models. First, we evaluated the binding activity of K-256 to 32 bromodomains using BROMOscan. Then, we compared the therapeutic effect of K-256 with existing BET inhibitors, including JQ1, OTX-015, and ABBV-075, as well as BET degraders, including dBET6 and ARB-771 in the MYC/BCL2-related lymphoma cell lines SU-DHL4 and SU-DHL6. The therapeutic effects of BET-targeting drugs combined with venetoclax were also evaluated. Finally, we verified the efficacy of K-256 using five MYC/BCL2-related, patient-derived xenograft (PDX) mouse models. Results: K-256 bound selectively to BRD2, BRD3, BRD4, and BRDT, and the Kd value for BRD4, which is most important for MYC transcription, was the lowest (bromodomain 1, 0.027 nM and bromodomain 2, 0.044 nM). We then confirmed that K-256 degraded BRD4 at lower concentrations compared to dBET6 and ARB-771 in SU-DHL4 and SU-DHL6. The GI 50 of K-256 in SU-DHL4 and SU-DHL6 was 12.8 nM and 7.50 nM, respectively, and K-256 induced cell death at lower concentrations than existing drugs (vs. JQ1, OTX-015, and ABBV-075, p < 0.0001; vs. dBET6 and ARV-771, p < 0.01). Immunoblotting analysis showed that K-256, even at a tenth of the concentration, suppressed MYC expression more effectively than existing BET inhibitors and was comparable to existing BET degraders. Moreover, combining K-256 with venetoclax exhibited synergistic effects, both inhibiting cell proliferation and inducing apoptosis in SU-DHL4 and SU-DHL6 cell lines (combination index (CI) of 0.23 and 0.41 for inhibiting cell proliferation, and 0.43 and 0.64 for inducing apoptosis, respectively). In experiments using five MYC/BCL2 PDX cells, K-256 inhibited cell proliferation (GI 50 ranging from 24 to 213 nM) and induced apoptosis (IC 50 ranging from 24 to 229 nM) at lower concentrations than existing BET inhibitors and degraders. As expected, the combination of K-256 with venetoclax also demonstrated synergistic effects in PDX cells, similar to those observed in cell lines (CI of 0.515 to 0.762 for inhibiting cell proliferation; 0.085 to 0.995 for inducing apoptosis). Finally, we confirmed that K-256 showed a stronger therapeutic effect than OTX-015 and ARV-771 in in vivo PDX models. Conclusions : The novel BET degrader, K-256, bound to BET proteins at lower concentrations than existing BET inhibitors and degraders, strongly suppressing MYC expression, primarily via BRD4 degradation. Additionally, K-256 demonstrated superior therapeutic effects in MYC/BCL2-related PDX models both in vitro and in vivo, suggesting that this novel drug could be a promising therapeutic agent for MYC/BCL2-related lymphoma. Its translation to future clinical applications warrants further consideration.

Acquired microRNA-142 Deficit Drives Escape Mechanisms of Anti-Leukemic Surveillance during Blast Crisis Transformation of Chronic Myeloid Leukemia (CML)

CML may evolve from a chronic phase (CP) into blast crisis (BC), but the underlying mechanisms of the transformation remain to be fully elucidated. We reported that microRNA (miR)-142 is downregulated in BC compared with CP patients; and in a murine model of CP CML (i.e., BCR-ABL mouse), miR-142 knock-out (KO) induced a BC-like phenotype, substantiating a mechanistic role of miR-142 deficit in BC transformation. Mechanistically, miR-142 KO induced mitochondrial fusion and increased oxidative phosphorylation (OxPhos) in leukemic stem cells (LSCs), causing a shift of leukemic phenotype from CP to BC ( Nat Commun, in press). Herein, we report that miR-142 deficit also occurs in T lymphocytes of BC patients due to inflammatory cytokines that are aberrantly produced by the proliferating leukemic cells. Using the Mir142 −/−BCR-ABL mouse, we observed that miR-142 deficit resulted in loss of T cell number and activity, suppressed the antileukemic immune surveillance, and contributed to BC transformation. In fact, miR-142 KO hampered thymic lymphoid-primed multipotent progenitor (LMPP) differentiation into T cells and rendered mature T cells dysfunctional and exhausted, with increase of PD-1 levels, and decrease of the apoptotic threshold, cell cycling and cytokine production, via blockade of OxPhos/glycolysis switch that regulates the metabolism of otherwise activated T cells. These changes translated into a decrease of T-cell antileukemic surveillance as demonstrated by increased numbers of BC murine Lin -Sca-1 +c-Kit + (LSKs) or human CD34+ blasts cocultured with Mir142 −/−T-cells vs those cocultured with Mir142 +/+ T-cells. Furthermore, congenic B6 (lethally irradiated to eradicate host T cells) or immunodeficient NSG (no T cells) recipient mice transplanted with Mir142 −/−BCR-ABL LSK and Mir142 −/− T cells had reduced T cells (both: p<0.0001), increased blasts (B6: p=0.01; NSG: p<0.0001) and a shorter survival (median survival for B6: 58 days vs unreached, p=0.008; for NSG: 28 days vs unreached, p<0.0001) compared with the respective controls transplanted with Mir142 −/−BCR-ABL LSK and Mir142 +/+ T cells. Transplantation of Mir142 −/−BCR-ABL LSKs into Mir142 −/− or Mir142 flox(f)/fLck-cre+ (i.e., miR-142 KO only in T cells; Mir142T Δ/Δ) recipients also resulted in a shorter survival than Mir142 +/+ recipients (median survival for Mir142 −/− vs Mir142 +/+ recipients: 44 vs 53 days, p=0.001; for Mir142T Δ/Δ vs Mir142 +/+ recipients: 42 vs 53 days, p=0.0002). To correct miR-142 deficit, we produced a synthetic miR-142 mimic oligonucleotide (CpG-M-miR-142). We treated a cohort of NSG mice transplanted with Mir142 −/−BCR-ABL LSKs and Mir142 −/− T cells, with CpG-M-miR-142 (30mg/kg/day, IV) or CpG-scramble RNA (SCR) for 3 weeks. We observed increased T cells (p=0.04), decreased blasts (p=0.0029) and longer survival (median survival: unreached vs 37 days, p=0.0005) in CpG-M-miR-142-treated recipients vs SCR-treated controls. Similar results were observed in CpG-M-miR-142-treated Mir142 −/−BCR-ABL mice vs SCR-treated controls. To test CpG-M-miR-142 activity in human T cells, a cohort of BC CML patient-derived xenograft (PDX) mice were given patient's autologous T cells and CpG-M-miR-142. Mice receiving T+CpG-M-miR-142 had increased T cell expansion (p=0.04), reduced leukemic cells (p=0.0078), and longer survival (median survival: 53 vs 38 days, p=0.01) than controls receiving T+SCR. In secondary transplants, the recipients of BM from T+CpG-M-miR-142-treated donors survived longer (median survival: 73 vs 53 days, p<0.0001) than the recipients of BM from T+SCR-treated donors, suggesting a decrease in LSC burden. Finally, we tested the efficacy of tyrosine kinase inhibitors (TKIs), which represent the primary targeting approach for CML, in combination with CpG-M-miR-142 and/or PD-1 inhibitor in Mir142 −/−BCR-ABL mice. The mice treated with TKI+CpG-M-miR-142 (median survival: 107 days, p=0.001) or TKI+PD-1 inhibitor (104 days, p=0.002) survived longer than the controls treated with TKI alone (66 days); the triplet combination (TKI+CpG-M-miR-142+PD-1 inhibitor) is expected to improve survival further (ongoing experiment). In summary, CpG-M-miR-142 alone and in combination with TKI or PD-1 inhibitor rescued T-cell antileukemic activity and prolonged survival in BC CML murine and PDX models, thereby providing a potentially new therapeutic approach for BC CML.

In Vivo Ablation of NFκB Cascade Effectors Alleviates Disease Burden in Myeloproliferative Neoplasms

ABAL and TK equal contributors Multilevel regulation of NFκB activation exists in response to microenvironmental cues. Aberrant hyperactivation of the NFκB cascade propagates oncogenic signaling and inflammation, which together augment disease burden in myeloproliferative neoplasms (MPNs). Here, we systematically ablated NFκB signaling effectors to identify core dependencies using a series of primary samples and syngeneic and patient-derived xenograft (PDX) mouse models. We first examined the impact of Rela abrogation in the Jak2 V617F knock-in mouse model that exemplifies polycythemia vera hallmarks and generated Jak2V617FRela flox/flox Ubc-Cre-ERT2 ( Jak2- Rela fl) mice. Evident suppression of leukocytosis was observed within a week of Rela excision and sustained until endpoint. Elevated hematocrit, monocytes, and CD45.2 myeloid cells were suppressed in both the peripheral blood (PB) and bone marrow (BM) and Jak2- Rela flmice had significant reduction of splenomegaly. We then adopted a second MPN model, where MPL W515L retroviral expression produces a phenotype resembling myelofibrosis. Consistent reduction of pathologic WBC counts, monocytes, and PB and BM CD45.2 myeloid cells were observed in MPL- Rela fl mice. Rela ablation also reduced hematocrit, platelet counts, and CD45.2 GFP+ cells. Importantly, we observed a significant attenuation of disease hallmarks with a decrease of spleen weight and dysmegakaryopoiesis, enhanced survival, and reduction of BM reticulin deposition. We next established PDX models where CD34+ cells from MF patients and healthy BM donors (NBM) were transduced with an sgRNA targeting RELA and engrafted into NSGS mice. Across two MPN PDXs, there was significant suppression of leukemic cells and improvement of disease burden, reduced spleen weights and prolonged survival, and subsequent BM histology revealing improved sclerosis, fibrosis, and dysmegakaryopoiesis. In contrast, NSGS mice engrafted with NBM CD34+ cells did not yield disease symptoms, nor did RELA targeting in healthy cells affect hematopoiesis or measured disease hallmarks. RNA-seq on CD34+ cells from four MPN patients following RELA abrogation revealed augmented and altered expression of genes that are 1) regulators of survival and proliferative pathways: MDM2, TP53INP1, and FAS 2) major ferroptosis mediator GPX4, and 3) cell cycle effectors: CDKN1A (p21), E2F4, and CHEK2. In further investigation of NFκB pathway effectors, we genetically targeted upstream effector Myd88 and transduced Kit+ cells from Myd88-null mice with MPL W515L. Consistent with Rela-knockout, Myd88-deficiency also diminished pathogenic WBC and monocyte count upsurgence, inhibited the accumulation of BM CD45.2 myeloid cells, and reduced spleen weights. The rapid lethality governed by mutant MPL was also delayed upon Myd88 loss, consistent with reduced pathology in spleen and BM sections. While Myd88 and Rela activate NFκB, miR-146a is repressive. We performed further knock-out of MIR146A using PDX models and transplanted MIR146A-KO CD34+ cells into NSGS mice and observed enhanced leukemic engraftment, increased spleen weights, earlier lethality, and evidence of BM sclerosis or fibrosis across both MF PDXs. Importantly, these disease parameters remained unchanged in a NBM PDX following MIR146A-KO. Lastly, in our WashU Cohort of RNA-sequencing performed on 90 CD34+ samples encompassing the spectrum of MPN and secondary acute myeloid leukemia (AML) with NBM controls, we observed significant upregulation of IRAK4 and IL1B in MF and sAML compared to NBM, and their significant expression correlation in MPN. We then pharmacologically inhibited IRAK4 using a small molecule, CA-4948, which is currently under evaluation in phase 1/2a trials of relapsed/refractory AML/myelodysplastic syndrome. In PDX experiments, CA-4948 treatment effectively reduced leukemic engraftment and spleen weights of two MF models without inducing toxicity in a NBM PDX. Through qRT-PCR and mass cytometry, we demonstrate that CA-4948 treatment dampened inflammatory cytokine production induced by IL-1β in primary MPN CD14+ monocytes. Overall, we demonstrate that targeting mediators including Rela, Myd88, and IRAK4 specifically alleviated MPN disease burden without toxicity to healthy tissue and further establish CA-4948 as a promising therapeutic avenue for the treatment of MPN.

CDK12/13: A Promising New Therapeutic Target in ALL

Acute lymphoblastic leukemia (ALL) is an aggressive hematologic malignancy in children and young adults. Upfront resistance to glucocorticoids used as first-line treatment in most regimens confers a poor prognosis for patients with ALL. Of patients who relapse, only half achieve long-term survival. Here we demonstrate that inhibition of cyclin dependant kinases 12 and 13 (CDK12 & CDK13), which are modulators of RNA polymerase II, has a robust synergistic anti-leukemia effect with dexamethasone, in both B-ALL and T-ALL cell lines as well as primary B-ALL patient-derived bone marrow samples. To understand the mechanism underlying the steroid resistance in ALL, we first reanalyzed shRNA screen performed by Poulard et al. This revealed that CDK13 silencing sensitized leukemic cells to dexamethasone. CDK12 is located on chromosome 17q12, containing oncogenic features and genetic alterations in various tumors. CDK12/13 inhibitor exhibits efficacy against an Ewing sarcoma tumor growth in a patient-derived xenograft mouse model. It was shown that the inhibition resensitizes HER2+ breast cancers to HER2-tyrosine kinase inhibitors via suppressing PI3K/AKT in patient-derived organoids in vitro and cell-derived xenograft or patient-derived xenograft in vivo. Forgoing research demonstrates that CDK12/13 inhibition silences transcription of DNA damage response (DDR) genes. In our study, however, we haven't observed a rise in γH2AX, a marker of DNA damage, after CDK12/13 inhibition in ALL cell lines. What we did note was a marked enhancement expression of BIM and SGK1, steroid responsive genes and pro-apoptotic factors, after CDK12/13 inhibition (Figure A). ALL cell lines exhibited high susceptibility to CDK12/13 inhibition with two chemically divergent inhibitors, SR-4835 and THZ-531. We also showcased their synergistic interactions with dexamethasone using flow cytometry and synergyfinder ZIP score analysis (Figure B). Moreover, in the GSEA comparison of ALL cell lines with and without synergy between CDK12/13 inhibitors and dexamethasone, our data underscored significant enrichment in cholesterol biosynthesis-related genesets in cell lines manifesting this synergistic effect. On the other hand, we observed resistance to SR-4835 in cell lines with high enrichment scores in NOTCH, a signaling pathway implicated in about 80% of relapsed T cell ALL/LBL cases. Additionally, new data on mice xenotransplanted with B-ALL CNS-derived patient cells, link upregulated cholesterol biosynthetic pathways to nervous system involvement in childhood ALL. Upon administering CDK12/13 inhibitors, we observed a cell cycle phase shift resulting in G1 arrest and increased apoptosis, whereas human peripheral blood mononuclear cells (PBMCs) from healthy individuals remained unaffected by this treatment. As we continue to decode the pathways through which CDK12/13 inhibitors render ALL cells more susceptible to dexamethasone, our next step includes silencing CDK12/13 using short hairpin RNA models in cell lines and consequently their RNA sequencing. This approach may mitigate the influence of secondary pathways, paving the way for enhanced treatment strategies for relapsed ALL by unmasking the underlying molecular events.

Exploiting the Metabolic Vulnerability of Leukemic Stem Cells (LSCs) in Inv(16) Acute Myeloid Leukemia (AML) with the Combination of Miristen, a Mir-126 Inhibitor, and Venetoclax

AML with inv(16)(p13q22) expresses the leukemogenic fusion gene CBFB-MYH11 and upregulates microRNA (miR)-126 that supports homeostasis, quiescence, and activity of LSCs. Genetic or pharmacologic depletion of miR-126 via miR-126 knock out (KO) or miRisten (a CpG-anti-miR-126 inhibitor) reduces LSCs in a Cbfb-MYH11 ( CM) knock-in (KI) AML model and inv(16) AML patient-derived xenografts (PDXs), respectively [PMID: 34686664]. However, the antileukemic underpinnings of miR-126 inhibition in inv(16) AML remain to be elucidated. LSCs reportedly rely on fatty acid metabolism/oxidative phosphorylation (OXPHOS) for their bioenergetic metabolic needs. To assess the role of miR-126 in metabolism, we performed metabolomic profiling for Lin-/c-Kit+ cells isolated from CM KI AML (miR-126 high) mice and CM with miR-126 KO mice ( CM/miR-126 Δ /Δ). Our data revealed that CM/miR-126 Δ /Δ had a significant decrease of short, medium as well as long-chain acyl carnitines and fatty acid (2 to 11 fold, p<0.05) compared to CM/miR-126 WT/ WT mice, suggesting that miR-126 deficit decreased fatty acid oxidation (FAO). Moreover, electron microscope imaging demonstrated mitochondrial fusion (i.e., larger and networked mitochondria) in CM Lin-/c-Kit+Sca1+ (LSK) cells vs syngeneic controls. In contrast, mitochondria fragmentation (fission) and decreased FAO/OXPHOS were observed in murine CM with miR-126 KO LSK. Accordingly, FAO and Seahorse assays demonstrated miRisten treatment led to mitochondria fragmentation and reduced FAO/OXPHOS and in human CD34 + CD38 ‒ inv(16) blasts (enriched for LSCs) vs normal CD34 + CD38 ‒ cells. Sprouty Related EVH1 Domain Containing 1 (SPRED1), a downstream target of miR-126, inhibits ERK/CREB activation and in turn increases antiapoptotic protein BCL-2 via phosphorylation and stabilization. In inv(16) AML cells, upregulated miR-126 downregulated SPRED1 and in turn increased ERK/CREB signaling and BCL-2 levels. This increase augments the ubiquitination of DRP1, a protein otherwise involved in mitochondrial fission, via NFE2-related factor 2 (NRF2), and increases Carnitine Palmitoyltransferase 1B (CPT1B), a rate-controlling protein for FAO and OXPHOS. In contrast, miR-126 KO or miR-126 inhibition by miRisten led to SPRED1 upregulation and decreased ERK/CREB signaling and BCL-2 levels, thereby resulting in increased Dynamin-related protein 1 (DRP1) and mitochondrial fission and a decrease in CPT1B, FAO, and OXPHOS. Thus, given the interplay of miR-126 with BCL-2 and its implication in mitochondrial fusion and increase of OXPHOS in inv(16) blasts and LSCs, we hypothesized a synergism between miRisten and the BCL-2 inhibitor venetoclax (VEN). In fact, combination of miRisten/VEN synergistically decreased FAO/OXPHOS, enhanced mitochondria fission and increased apoptosis of murine and human inv(16) blasts and LSCs [combination indices (CIs)<1, (ED50-ED95)]. Thus, we treated CM mice with scrambled oligonucleotides (sODN) (20 mg/kg i.v., daily for 3 weeks), miRisten (20 mg/kg i.v., daily for 3 weeks), VEN (100 mg/kg oral gavage, daily for 2 weeks), or miRisten/VEN (same dosages as single agents). Compared with sODN or single agents, miRisten/VEN significantly reduced bone marrow (BM) leukemic blast infiltration [miRisten/VEN 33.6±3.4% vs miRisten 49.8±2.6% (p=0.001), VEN 56.2±4.7% (p=0.001), or sODN 60.0±2.6% (p<0.0001)] and spleen weights [miRisten/VEN 0.228±0.038g vs miRisten 0.495±0.058g (p=0.001), VEN 0.479±0.06g (p=0.002), or sODN 0.853±0.039g (p<0.0001)] and prolonged survival of CM mice [median survival miRisten/VEN 125d vs miRisten 108d (p=0.005), VEN 106.5d (p=0.039), or sODN 91d (p<0.0001), respectively; secondary transplant median survival: miRisten/VEN 92d vs miRisten 70.5d (p=0.048), VEN 54d (p=0.006), or sODN 45d (p=0.0002)]. Similar results were also observed in inv(16) PDXs with significant reduction of BM huCD45+ leukemic blasts by miRisten/VEN compared to single agents or sODN [miRisten/VEN 13.7±1.9% vs miRisten 27.9±3.4% (p=0.003), VEN 25.3±4.6%(p=0.032), or sODN 68.6±5.3% (p<0.0001)]; survival analyses for treated PDX mice and secondary transplant recipients are in progress. In summary, our study provides the mechanism for combining miRisten with VEN in the treatment of inv(16) AML. While VEN is FDA approved for AML, miRisten has just undergone a successful toxicology evaluation and is underway to the clinic.

RSK1 Is an Exploitable Dependency in Myeloid Malignancies

Myeloid malignancies harbor distinct molecular drivers but share convergence of oncogenic signaling pathways and propagation by ripe pro-inflammatory niches. To delineate these hallmarks across the spectrum of myeloid disease states, we established the largest comprehensive atlas of myeloproliferative neoplasms (MPN) and secondary acute myeloid leukemia (sAML) through RNA-sequencing and mass cytometry (CyTOF) of 370 primary samples encompassing CD34+ hematopoietic stem/progenitor cells and CD14+ monocytes, revealing aberrant of PI3K/AKT/mTOR signalling and NFκB-mediated hyper-inflammation. As a central mediator of these hyperactive signaling pathways, ribosomal S6 kinases (RSKs) represent potentially attractive novel therapeutic targets warranting further evaluation. Using both genetic approaches and a first-in-class oral RSK inhibitor, PMD-026, that is currently being evaluated in phase 1/1b clinical trials (NCT04115306) in metastatic and triple negative breast cancer, we found that RSK1 ( RPS6KA1) inhibition potently induced apoptosis and G2/M arrest in leukemia models in conjunction with suppression of PI3K/AKT/mTOR and NFκB signaling. Further NFκB cascade profiling following RSK1 perturbation revealed reduced phosphorylation of IKKα/β and p65/RELA and prevention of p65/RELA nuclear translocation. Using RNA-seq, ATAC-seq and H3K27ac CUT&Tag, we found that PMD-026 treatment altered chromatin accessibility and inhibited NFKB1, TNF, and cell cycle regulators CCNA1/2 and CDK1/2. In cytokine CyTOF, PMD-026 nearly abrogated all induction of inflammatory cytokines including TNF, IL-6, IL-8, CCL3, and CCL4 in primary MPN monocytes to levels substantially below basal conditions. We further extended our findings to de novo AML harboring FLT3 internal tandem duplication ( FLT3-ITD), where FLT3-ITD patients exhibited elevated RPS6KA1 expression and those who developed resistance to gilteritinib demonstrated progressively increased RPS6KA1 expression. FLT3-ITD cells exhibited preferentially sensitivity to RSK1 inhibition, where we uncovered bi-directional regulation. Through cycloheximide, MG-132, and ubiquitination assays, we found that RSK1 regulates FLT3-ITD activity and protein stability through deubiqutinase USP1, and where either RPS6KA1 or USP1 inhibition resulted in concomitant downregulation of FLT3 protein and cell lethality. Multivariate analysis of the TCGA and BeatAML cohorts (n= 568 patients) revealed high median USP1 or RPS6KA1 expression to be significantly associated with poor survival, thus defining a RSK1-USP1-FLT3 axis with prognostic relevance. Across in vivo models, PMD-026 ameliorated MPN disease features driven by MPL W515L including leukocytosis, splenomegaly, and bone marrow fibrosis, while prolonging survival, in conjunction with suppression of inflammatory cytokines including TNF, IL-6 and IL-1b. We then evaluated PMD-026 across five patient-derived xenograft (PDX) models spanning the spectrum of myeloid malignancies including myelofibrosis (MF), sAML, and chronic myelomonocytic leukemia (CMML) encompassing various driver and multiple high-risk mutations. Treatment in MF PDX mice decelerated disease progression, extended survival, and reduced splenomegaly, while in CMML/sAML PDXs, PMD-026 led to a 67 to 96 percent reduction in human CD45+ cells engraftment. Finally, PMD-026 treatment in both mice xenografted with MV4-11 cells and syngeneic Flt3ITDTet2KO mice significantly reduced leukemic cell engraftment and prolonged survival. These data indicate potent efficacy of RSK inhibition across diverse models of chronic and acute myeloid malignancies. Lastly, we investigated the impact of PMD-026 on hematological parameters from 41 breast cancer patients enrolled in the phase 1/1b clinical trial. Overall, there was no sustained suppressive effect on hematological parameters and there were no hematological PMD-026-related toxicities meeting criteria for dose modification during the trial period. These clinical data demonstrate that PMD-026 did not cause myelosuppression. Our findings uncover a novel therapeutic avenue for a conserved RSK1 dependency across chronic and acute myeloid neoplasms. The potent and consistent disease-ameliorating effects across numerous leukemia mouse models demonstrates promise for repurposing PMD-026 for the treatment of myeloid malignancies.

A novel Fc-enhanced humanized monoclonal antibody targeting B7-H3 suppresses the growth of ESCC

ABSTRACT Esophageal squamous cell carcinoma (ESCC) is a prevalent malignant tumor of the digestive tract with a low 5-year survival rate due to the lack of effective treatment methods. Although therapeutic monoclonal antibodies (mAbs) now play an important role in cancer therapy, effective targeted mAbs are still lacking for ESCC. B7-H3 is highly expressed in a variety of tumors and has emerged as a promising therapeutic target. Several mAbs against B7-H3 have advanced to clinical trials, but their development has not yet been pursued for ESCC. Here, we developed a humanized and Fc-engineered anti-B7H3 mAb 24F-Hu-mut2 and systematically evaluated its anti-tumor activity in vitro and in vivo. The 24F-Hu-mut2 was humanized and modified in Fc fragment to obtain stronger antibody-dependent cell-mediated cytotoxicity(ADCC) activity and nanomolar affinity. Furthermore, both of ESCC cell-derived xenograft (CDX) and patient-derived xenograft (PDX) mice models indicated that 24F-Hu-mut2 displayed potent in vivo anti-tumor activity. In addition, a computational docking model showed that the mAb bound to IgC1 and IgC2 domain of B7-H3, which is closer to the cell membrane. Consistently, our ELISA results verified the binding of 24F-Hu-WT and IgC1 and IgC2. Our results indicate that 24F-Hu-mut2 has significant anti-ESCC activity both in vitro and in vivo, and this monoclonal antibody may be a promising antibody against ESCC and other B7-H3 overexpressing tumors.

LncRNA-CCAT5-mediated crosstalk between Wnt/β-Catenin and STAT3 signaling suggests novel therapeutic approaches for metastatic gastric cancer with high Wnt activity.

Although the constitutively activated Wnt/β-catenin signaling pathway plays vital roles in gastric cancer (GC) progression, few Wnt inhibitors are approved for clinical use. Additionally, the clinical significance of long non-coding RNAs (lncRNAs) in GC intraperitoneal dissemination (IPD) remains elusive. Here, we investigated the function and therapeutic potential of Wnt-transactivated lncRNA, colon cancer-associated transcript 5 (CCAT5), in GC metastasis. LncRNA-sequencing assay was performed to document abundance changes of lncRNAs induced by Wnt family member 3A (Wnt3a) and degradation-resistant β-catenin (S33Y mutated) in ascites-derived GC cells with low Wnt activity. Luciferase reporter, Chromatin immunoprecipitation (ChIP)-re-ChIP assays were performed to determine how CCAT5 was transcribed. The clinical significance of CCAT5 was examined in 2 cohorts of GC patients. The biological function of CCAT5 was investigated through gain- and loss-of-function studies. The molecular mechanism was explored through RNA-sequencing, mass spectrometry, and CRISPR/Cas9-knocknout system. The therapeutic potential of CCAT5 was examined through RNAi-based cell xenograft model and patient-derived xenograft (PDX) model of IPD. We identified a novel Wnt-regulated lncRNA, CCAT5, which was transactivated by the β-catenin/transcription factor 3 (TCF3) complex. CCAT5 was significantly upregulated in GC and predicted poor prognosis. Functional studies confirmed the promotive role of CCAT5 in GC growth and metastasis. Mechanistically, CCAT5 bound to the C-end domain of signal transducer and activator of transcription 3 (STAT3) and blocks Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP-1)-mediated STAT3Y705 dephosphorylation, leading to STAT3 nuclear entry and transactivation, thus accelerating GC progression. Furthermore, we demonstrated that both Wnt3a and β-catenin acted as activator of STAT3 signaling pathway, and the interplay between CCAT5 and STAT3 was functionally essential for Wnt-drived STAT3 signaling and tumor evolution. Finally, we revealed in vivo si-CCAT5 selectively attenuated growth and metastasis of Wnthigh GC, but not Wntlow GC. The combination of si-CCAT5 and oxaliplatin displayed obvious synergistic therapeutic effects on Wnthigh PDX mice. We identified a novel Wnt-transactivated lncRNA, CCAT5. Our study revealed a mechanism of STAT3 signaling regulation via canonical Wnt signaling and the functional significance of CCAT5 as critical mediator. We provided conceptual advance that lncRNAs serve as therapeutic targets reversing GC progression.

CNSC-26. GLIOBLASTOMA-NEURONAL CIRCUIT INTEGRATION IS MODULATED BY INTERLEUKIN-6

Abstract The pleiotropic cytokine interleukin-6 (IL-6) is known to be involved in both pro- and anti-inflammatory signaling cascades. In glioblastoma studies using animal and human models, IL-6 promotes immunosuppression and tumor progression and is negatively associated with survival. Intriguingly, IL-6 also contributes to increased synaptogenesis during development and following focal brain injury. Glioblastoma remodeling of neuronal circuits influences patient survival; therefore, it is possible that IL-6 has mechanistic significance. Here, we investigated IL-6 as a driver of activity-dependent glioblastoma proliferation using patient-derived xenograft (PDX) mouse and human glioblastoma models. We assessed neuronal activity by microelectrode arrays and in vitro calcium imaging using weighted mean firing rate (WMFR), network burst frequency (NBF), and synchrony index. Next, we used bulk and single-cell RNA sequencing on 13,731 cells from ten tumors including pair-matched samples to identify differentially expressed genes in intratumoral regions with elevated functional connectivity and found IL6 to be highly upregulated. Mouse embryonic cortical neurons and cerebral organoids co-cultured with primary patient-derived glioblastoma cells demonstrated concentration-dependent neuronal hyperexcitability (increased WMFR and NBF) in IL-6-overexpressing conditions compared to the neuron-only condition. Pharmacological inhibition using the humanized IL-6 receptor antibody tocilizumab reduced network synchrony across models. These findings suggest that IL-6-induced glioma-neuronal hyperexcitability may be inhibited by the FDA-approved tocilizumab, thereby providing preclinical support for its use to treat activity-dependent mechanisms of glioblastoma proliferation. Future studies are needed to uncover mechanisms and clinical efficacy.