Cell-derived Xenograft Research Articles

Targeting the splicing factor SNRPB inhibits endometrial cancer progression by retaining the POLD1 intron.

Dysregulated alternative splicing has been closely linked to the initiation and progression of tumors. Nevertheless, the precise molecular mechanisms through which splicing factors regulate endometrial cancer progression are still not fully understood. This study demonstrated elevated expression of the splicing factor SNRPB in endometrial cancer samples. Furthermore, our findings indicate that high SNRPB expression is correlated with poor prognosis in patients with endometrial cancer. Functionally, SNRPB inhibition hindered the proliferative and metastatic capacities of endometrial cancer cells. Mechanistically, we revealed that SNRPB knockdown decreased POLD1 expression and that POLD1 intron 22 was retained after SNRPB silencing in endometrial cancer cells, as determined via RNA sequencing data analysis. The retained intron 22 of POLD1 created a premature termination codon, leading to the absence of amino acids 941-1,107 and the loss of the site of interaction with PCNA, which is essential for POLD1 enzyme activity. In addition, POLD1 depletion decreased the increase in the malignancy of endometrial cancer cells overexpressing SNRPB. Furthermore, miR-654-5p was found to bind directly to the 3' untranslated region of SNRPB, resulting in SNRPB expression inhibition in endometrial cancer. Antisense oligonucleotide-mediated SNRPB inhibition led to a decrease in the growth capacity of a cell-derived xenograft model and a patient with endometrial cancer-derived xenograft model. Overall, SNRPB promotes the efficient splicing of POLD1 by regulating intron retention, ultimately contributing to high POLD1 expression in endometrial cancer. The oncogenic SNRPB-POLD1 axis is an interesting therapeutic target for endometrial cancer, and antisense oligonucleotide-mediated silencing of SNRPB may constitute a promising therapeutic approach for treating patients with endometrial cancer.

Metformin Induces Apoptosis and Ferroptosis of Ovarian Cancer Cells Under Energy Stress Conditions

As ovarian cancer progresses, increased glucose use causes a glucose shortage in the tumor microenvironment. Therefore, it is crucial to find drugs that can effectively kill cancer cells in this energy stress setting. Here, we propose an effective therapeutic strategy that combines nutrient restriction with metformin to combat tumors. This study investigated the effects of metformin on ovarian cancer cells under energy stress conditions, mimicking the nutrient-deprived tumor microenvironment. We revealed that Metformin (10 mM) significantly reduced cell viability and proliferation under glucose deprivation conditions. Furthermore, it enhanced apoptosis and ferroptosis, as demonstrated by alterations in apoptotic protein expression and elevated levels of lipid reactive oxygen species (ROS), malondialdehyde (MDA), lipid peroxidation (LPO), and Fe2+. Transcriptional profiling revealed significant alterations in genes related to iron homeostasis and oxidative phosphorylation. Moreover, Metformin was found to induce mitochondrial dysfunction without affecting mitochondrial DNA or the expression of enzymes in the tricarboxylic acid (TCA) cycle, resulting in decreased ATP production and compromised activities of the respiratory chain complexes. The direct interaction between metformin and the NDUFB4 subunit in mitochondrial complex I was corroborated through the application of cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) assays. In vivo, the combination of metformin and fasting cycles significantly inhibited SKOV3 cell-derived xenograft tumors in immunodeficient mice. Altogether, we have demonstrated that Metformin potentiates apoptosis and ferroptosis in ovarian cancer cells under energy stress conditions by targeting the NDUFB4 subunit of mitochondrial complex I, thus laying the groundwork for clinical testing. This study, though limited to cellular and animal levels, provides valuable insights into the therapeutic potential of metformin in ovarian cancer treatment.

XPO1 inhibition as a clinically viable strategy to enhance durability of response to KRAS G12D inhibitor in pancreatic ductal adenocarcinoma.

736 Background: The OFF State (GDP bound) KRASG 12D inhibitor MRTX1133 is currently being evaluated in pancreatic ductal adenocarcinoma (PDAC) patients. Nevertheless, as with other OFF state KRAS G12C inhibitors sotorasib and adagrasib, the KRAS G12D inhibitor may yield only a modest increase in disease-free survival due to emergence of drug resistance. This underscores the need to identify strategies that can enhance the efficacy of KRAS inhibitors in PDAC. Nuclear protein transport plays an important role in several pro-tumorigenic pathways and has been shown to be a therapeutic vulnerability in KRAS mutant cancers. XPO1 is the major nuclear exporter and plays a pivotal role in shuttling various critical tumor suppressors, genome surveillance proteins, and transcription factors out of the nucleus and is frequently overexpressed in various cancers, including PDAC. In this study, we employed a KRAS G12D inhibitor resistant model and evaluated its sensitivity to nuclear exporter protein inhibitor. Methods: We examined the cytotoxic and molecular effects of KRAS G12D inhibitor MRTX1133 in combination with nuclear transport inhibitor eltanexor in KRAS G12D inhibitor resistant models. The preclinical antitumor efficacy of the combination was evaluated in KRAS G12D mutant PDAC cell derived xenograft (CDX) subcutaneous and orthotopic models. Results: Eltanexor treatment reversed MRTX1133 resistance in vitro yielding suppressed proliferation of KRAS G12D mutant 2D and 3D cultures of PDAC cell lines and patient derived primary tumors cells. High throughput P-kinome analysis showed suppression of a larger repertoire of MAPK substrates in combination treatment compared to single agent group. Eltanexor and MRTX1133 combination led to reduction in protein expression of KRAS downstream effectors and cell cycle markers. Furthermore, a combined administration of eltanexor and MRTX1133 at sub-optimal doses resulted in remarkable tumor growth inhibition in multiple subcutaneous and orthotopic KRAS G12D mutant mice models. Moreover, eltanexor as a maintenance therapy also prevented tumor relapse indicating durability of response in PDAC. Conclusions: This is the first study demonstrating that nuclear transport inhibitors can overcome KRAS G12D inhibitor MRTX1133 resistance in PDAC cells. This study provides a rationale for combining MRTX1133 with eltanexor for the treatment of PDAC patients with KRAS G12D mutant tumors.

Tegaserod maleate exerts anti-tumor effects on prostate cancer via repressing sonic hedgehog signaling pathway

Prostate cancer (PCa) is a highly common type of malignancy and affects millions of men in the world since it is easy to recur or emerge therapy resistance. Therefore, it is urgent to find novel treatments for PCa patients. In the current study, we found that tegaserod maleate (TM), an FDA-approved agent, inhibited proliferation, colony formation, migration as well as invasion, caused the arrest of the cell cycle, and promoted apoptosis of PCa cells in vitro. In addition, TM suppressed the tumor growth in the cell-derived xenograft (CDX) mouse model in vivo. Mechanistically, TM exerted anti-tumor effects via downregulating GLI2, and its downtream targets, thus inhibiting the sonic hedgehog (SHH) signaling pathway. In brief, our findings demonstrated that TM effectively inhibited the activities of PCa cells by suppressing the SHH signaling pathway and provided a potential new agent for the treatment of PCa.

SRC enhanced cisplatin resistance in bladder cancer by reprogramming glycolysis and pentose phosphate pathway

The development of cisplatin resistance often results in a grim prognosis in advanced or recurrent bladder cancer. However, effective treatment strategies for cisplatin resistance have not been well established. Herein, we found that overactivation of SRC is associated with cisplatin-resistance. SRC activates hexokinase2 which up-regulates glycolysis and especially the pentose phosphate pathway that leading to increased nucleotide synthesis and NADPH production which can neutralize reactive oxygen species (ROS) induced by cisplatin, thereby protecting bladder cancer cells from cisplatin-induced DNA damage. This phenomenon was effectively reversed by knockout of SRC and inhibition of SRC activity by the SRC inhibitor, eCF506. Moreover, we constructed Cell-derived xenograft (CDX) and Patient-derived xenograft (PDX) from cisplatin-resistant bladder cancer patient. eCF506 exhibited excellent anti-tumor effects and effectively enhanced cisplatin-sensitivity. Altogether, our findings demonstrate that targeting SRC is a promising approach to overcome cisplatin-resistance in bladder cancer, and providing new insights for combination therapy in bladder cancer.

Betaine inhibits the stem cell-like properties of hepatocellular carcinoma by activating autophagy via SAM/m6A/YTHDF1-mediated enhancement on ATG3 stability.

Background: Stem cell-like properties are known to promote the recurrence and metastasis of hepatocellular carcinoma (HCC), contributing to a poor prognosis for HCC patients. Betaine, an important phytochemical and a methyl-donor related substance, has shown protective effects against liver diseases. However, its effect on HCC stem cell-like properties and the underlying mechanisms remains uninvestigated. Methods: We measured the effects of betaine on the stem cell-like properties and malignant progression of HCC using patient-derived xenografts, cell-derived xenografts, tail vein-lung metastasis models, in vitro limiting dilution, tumor sphere formation, colony formation, and transwell assays. Mechanistic exploration was conducted using western blots, dot blots, methylated RNA immunoprecipitation-qPCR, RNA stability assays, RNA immunoprecipitation-qPCR, RNA pull-down, and gene mutation assays. Results: A cohort study of HCC found that a higher serum concentration of betaine was associated with decreased levels of stemness-related markers. Furthermore, in HCC cells and xenograft mice, betaine suppressed the stem cell-like properties of HCC by activating autophagy. Mechanistically, betaine increased the m6A modification in HCC by producing S-adenosylmethionine (SAM) via betaine-homocysteine S-methyltransferase (BHMT). This increase in SAM subsequently triggered autophagy by enhancing the stability of autophagy-related protein 3 (ATG3) via YTHDF1 in an m6A-dependent manner, thereby inhibiting the stem cell-like properties of HCC cells. Conclusions: These findings indicate that betaine inhibits the stem cell-like properties of HCC via the SAM/m6A/YTHDF1/ATG3 pathway. This study underscores the potential anti-tumor effects of betaine on HCC and offers novel therapeutic prospects for HCC patients.

RTN4IP1 Contributes to ESCC via Regulation of Amino Acid Transporters.

Esophageal squamous cell carcinoma (ESCC) accounts for about 90% of esophageal cancer cases. The lack of effective therapeutic targets makes it difficult to improve the overall survival of patients with ESCC. Reticulon 4 Interacting Protein 1 (RTN4IP1) is a novel mitochondrial oxidoreductase. Here, a notable upregulation of RTN4IP1 is demonstrated, which is associated with poor survival in patients with ESCC. RTN4IP1 depletion impairs cell proliferation and induces apoptosis of ESCC cells. Furthermore, c-Myc regulates RTN4IP1 expression via iron regulatory protein 2 (IRP2) at the post-transcriptional level. Mechanistically, RTN4IP1 mRNA harbors functional iron-responsive elements (IREs) in the 3' UTR, which can be targeted by IRP2, resulting in increased mRNA stability. Finally, RTN4IP1 depletion abrogates amino acid uptake and induces amino acid starvation via downregulation of the amino acid transporters SLC1A5, SLC3A2, and SLC7A5, indicating a possible pathway through which RTN4IP1 contributes to ESCC carcinogenesis and progression. In vivo studies using cell-derived xenograft and patient-derived xenograft mouse models as well as a 4-nitroquinoline 1-oxide-induced ESCC model in esophageal-specific Rtn4ip1 knockout mice demonstrate the essential role of RTN4IP1 in ESCC development. Thus, RTN4IP1 emerges as a key cancer-promoting protein in ESCC, suggesting therapeutic RTN4IP1 suppression as a promising strategy for ESCC treatment.

Platinum drugs upregulate CXCR4 and PD-L1 expression via ROS-dependent pathways, with implications for novel combined treatment in gastric cancer.

CXC chemokine receptor 4 (CXCR4) and programmed cell death-ligand 1 (PD-L1) are two critical molecules involved in the tumor immune microenvironment. However, the impact of platinum drugs, such as cisplatin, on CXCR4 or PD-L1 expression and the underlying mechanisms in gastric cancer (GC) remain unknown. Moreover, the correlation between their expression levels in GC remains elusive. Immunohistochemistry, western blot, and RT-qPCR were performed to determine the expression pattern of CXCR4 and PD-L1 in GC. Clinical samples, patient-derived xenografts, and cell-derived xenografts were utilized to investigate the effects of platinum drugs on the expression levels of CXCR4 and PD-L1. Postchemotherapy resected GC tumor tissues showed higher CXCR4 and PD-L1 expression levels than pretreatment biopsies (p < 0.05). Similarly, GC xenografts treated with platinum-based chemotherapy exhibited increased CXCR4 and PD-L1 expression levels compared to saline-treated controls (p < 0.05). A positive correlation was detected between the expression levels of CXCR4 and PD-L1 in GC tumor tissues. Increased levels of CXCR4 and PD-L1 expression, in a dose- and time-dependent manner upon cisplatin treatment, were observed in GC cells (p < 0.05). Cisplatin-induced CXCR4 upregulation relies on ROS/HIF-1α and ROS/NF-κB pathways, while cisplatin-induced PD-L1 upregulation is cyclic GMP-AMP synthase/stimulator of IFN genes-dependent and associated with elevated ROS levels in GC cells. CXCR4 expression was found to be positively correlated with PD-L1 expression in GC. Platinum drugs upregulated the levels of CXCR4 and PD-L1 expression in GC. A combined strategy targeting CXCR-4 and PD-L1 might have clinical prospects for GC patients.

Discovery of a molecular glue for EGFR degradation.

Aberrant expression of epidermal growth factor receptor (EGFR) plays a critical role in the pathogenesis of various tumors, potentially representing a target for therapeutic intervention. Nonetheless, EGFR remains a challenging protein to target pharmacologically in triple-negative breast cancer (TNBC). An emerging approach to address the removal of such proteins is the application of molecular glue (MG) degraders. These compounds facilitate protein-protein interactions between a target protein and an E3-ubiquitin ligase, subsequently leading to protein degradation. Herein, we identified a new MG (CDDO-Me, C-28 methyl ester of 2-cyano-3, 12-dioxooleana-1, 9(11)-dien-28-oic acid), which orchestrated binding between EGFR and KEAP1 (an E3-ubiquitin ligase adapter), thereby initiating the ubiquitination and degradation of EGFR. CDDO-Me directly interacted with the tyrosine kinase (TK) domain of EGFR, resulting in its degradation via an autophagy-dependent lysosomal pathway. Knockdown of KEAP1 decreased the degradation of EGFR by reducing its K63-linked ubiquitination, leading to diminished EGFR colocalization in autophagosomes and lysosomes. Notably, CDDO-Me attenuates TNBC progression by accelerating EGFR degradation in cell-derived xenografts and patient-derived organoid models, highlighting its clinical application potential. Consequently, induction of EGFR degradation through MG degraders represents a viable therapeutic strategy for TNBC.

Loop33 × 123 CAR-T targeting CD33 and CD123 against immune escape in acute myeloid leukemia

BackgroundImmunotherapy, such as chimeric antigen receptor T (CAR-T) cells targeting CD33 or CD123, has been well developed over the past decade for the treatment of acute myeloid leukemia (AML). However, the inability to sustain tumor-free survival and the possibility of relapse due to antigen loss have raised concerns. A dual targeting of CD33 and CD123 is needed for better outcomes.MethodsBased on our previously constructed CD33 and CD123 monovalent CAR-T, Loop33 × 123 and Loop123 × 33 CAR-T were constructed with molecular cloning techniques. All CAR-T cells were generated by lentivirus transduction of T cells from healthy donors. Phenotype detection was evaluated on day 7 concerning activation, exhaustion, and subtype proportions. Coculture killing assays were conducted using various AML cell lines and primary AML cells. Degranulation and cytokine secretion levels were detected by flow cytometry. Cell-derived xenograft models were established using wild-type Molm 13 cell lines, or a mixture of Molm 13-KO33 and Molm 13-KO123 cells as an ideal model of immune escape. By monitoring body weight and survival of tumor-bearing mice, Loop33 × 123 and Loop123 × 33 CAR-T cells were further assessed for their efficacy in vivo.ResultsIn vitro study, our results demonstrated that Loop33 × 123 CAR-T cells could efficiently eliminate AML cell lines and primary AML cells with elevated degranulation and cytokine secretion levels. Compared with our previously constructed monovalent CD33 or CD123 CAR-T cells, Loop33 × 123 CAR-T cells showed superior advantages in an immune escape model. In vivo studies further confirmed that Loop33 × 123 CAR-T cells could effectively prolong the survival of mice without significant toxicity. However, Loop123 × 33 CAR-T cells failed to show the same effects. Furthermore, Loop33 × 123 CAR-T cells efficiently circumvented potential immune escape, a challenge where monovalent CAR-T cells failed.ConclusionsLoop33 × 123 CAR-T targeting CD33 and CD123 could efficiently eliminate AML cells and prolong survival of tumor-bearing mice, while addressing the issue of immune escape.

Neuronatin Promotes the Progression of Non-small Cell Lung Cancer by Activating the NF-κB Signaling.

Understanding the regulatory mechanisms involving neuronatin (NNAT) in non-small cell lung cancer (NSCLC) is an ongoing challenge. This study aimed to elucidate the impact of NNAT knockdown on NSCLC by employing both in vitro and in vivo approaches. To investigate the role of NNAT, its expression was silenced in NSCLC cell lines A549 and H226. Subsequently, various parameters, including cell proliferation, invasion, migration, and apoptosis, were assessed. Additionally, cell-derived xenograft models were established to evaluate the effect of NNAT knockdown on tumor growth. The expression of key molecules, including cyclin D1, B-cell leukemia/lymphoma 2 (Bcl-2), p65, matrix metalloproteinase (MMP) 2, and nerve growth factor (NGF) were examined both in vitro and in vivo. Nerve fiber density within tumor tissues was analyzed using silver staining. Upon NNAT knockdown, a remarkable reduction in NSCLC cell proliferation, invasion, and migration was observed, accompanied by elevated levels of apoptosis. Furthermore, the expression of cyclin D1, Bcl-2, MMP2, and phosphorylated p65 (p-p65) showed significant downregulation. In vivo, NNAT knockdown led to substantial inhibition of tumor growth and a concurrent decrease in cyclinD1, Bcl-2, MMP2, and p-p65 expression within tumor tissues. Importantly, NNAT knockdown also led to a decrease in nerve fiber density and downregulation of NGF expression within the xenograft tumor tissues. Collectively, these findings suggest that neuronatin plays a pivotal role in driving NSCLC progression, potentially through the activation of the nuclear factor-kappa B signaling cascade. Additionally, neuronatin may contribute to the modulation of tumor microenvironment innervation in NSCLC. Targeting neuronatin inhibition emerges as a promising strategy for potential anti-NSCLC therapeutic intervention.

Parental Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Predominates Over Coinfected SARS-CoV-2 Delta, Producing Less Lethal Variants in a Long-Term Replication Mouse Model.

The evolution of SARS-CoV-2, which limits public control and treatment, seems to have occurred through multiple mechanisms, including recombination of cocirculating strains in hosts. However, insufficient experimental data have been obtained after coinfection. Therefore, we investigated the emergence of variants after coinfection with parental SARS-CoV-2 and the SARS-CoV-2 Delta. We found that fewer (approximately 50%) mutations accumulated in Calu-3 cells than in other cells after serial passaging. Previously, we established a long-term replication mouse model by infecting Calu-3 cell-derived xenograft tumors with SARS-CoV-2. Here, we utilized our model to investigate the outcome after coinfection. More diverse viral mutations, along with multiple high-frequency simultaneous mutations, were discovered in the tumors than during cell passaging. Viral isolates from the tumors showed no cytopathic effects and formed much smaller plaques. Phylogenetic analysis suggested that the genetic makeup of the variants remained largely the same as that of parental SARS-CoV-2 rather than the SARS-CoV-2 Delta. Viral challenge revealed that the isolates were less lethal than the parental SARS-CoV-2 and SARS-CoV-2 Delta strains. These findings suggest that parental SARS-CoV-2 predominates over the SARS-CoV-2 Delta when coinfected, but the SARS-CoV-2 Delta contributes to the evolution of parental SARS-CoV-2 variants toward better host adaptation without recombination.

Overcoming multi-drug resistance in SCLC: a synergistic approach with venetoclax and hydroxychloroquine targeting the lncRNA LYPLAL1-DT/BCL2/BECN1 pathway

BackgroundSmall cell lung cancer (SCLC) stands as one of the most lethal malignancies, characterized by a grim diagnosis and prognosis. The emergence of multi-drug resistance poses a significant hurdle to effective therapy. Although previous studies have implicated the long noncoding RNA LYPLAL1-DT in the tumorigenesis of SCLC, the precise role of the highly expressed LYPLAL1-DT in SCLC chemoresistance and the underlying mechanism remain inadequately understood.MethodscDDP-, VP-16- and PTX-resistant SCLC cells lines were established. The viabilities of SCLC cells were assessed by CCK-8 assay in vitro and xenograft tumor formation assay in vivo. Apoptosis was evaluated by FACS, Western blot and JC-1 fluorescence staining, while autophagy was explored via autophagic flux detection under confocal microscopy and autophagic vacuole investigation under transmission electron microscopy (TEM). The functional role and mechanism of LYPLAL1-DT were further investigated by gain- and loss-of-function assays in vitro. Furthermore, the therapeutic efficacy of the combination of venetoclax and HCQ with cDDP, VP-16 or PTX was evaluated by cell line, cell-derived xenograft (CDX) and patient-derived xenograft (PDX) mice model.ResultsOur findings revealed that LYPLAL1-DT is upregulated in chemoresistant SCLC cell lines. Gain- and loss-of-function assays demonstrated that LYPLAL1-DT impairs sensitivity to cDDP, VP-16, or PTX both in vitro and in vivo. Overexpression of LYPLAL1-DT significantly enhanced autophagy and inhibited apoptosis in SCLC cells. Further analyses, including RIP and RNA pull-down assays, revealed that LYPLAL1-DT promotes the expression of BCL2 by sponging miR-204-5p and is implicated in the assembly of the autophagy-specific complex (BECN1/PtdIns3K complex). Combining venetoclax and HCQ with cDDP, VP-16, or PTX effectively mitigated chemoresistance in SCLC cells and suppressed tumor growth in CDX and PDX models without inducing obvious toxic effects.ConclusionsOur findings demonstrate that upregulation of LYPLAL1-DT sequesters apoptosis through the LYPLAL1-DT/miR-204-5p/BCL2 axis and promotes autophagy by facilitating the assembly of the BECN1/PtdIns3K complex, thereby mediating multi-drug resistance of SCLC. The triple combination of venetoclax, HCQ, in conjunction with cDDP, VP-16 or PTX overcomes refractory SCLC, shedding light on a potential therapeutic target for combating SCLC chemoresistance.

Single-cell sequencing analysis revealed that NEAT1 was a potential biomarker and therapeutic target of prostate cancer.

Prostate cancer (PCa) usually manifests atypical symptoms in the early stage, and once symptoms appear, most PCa patients have developed to the advanced stage, failing to undergo radical surgery. In this study, PCa occurrence-related biomarkers were explored based on single-cell RNA sequencing (scRNA-seq) data. scRNA-seq data of prostate normal (Normal), benign prostatic hyperplasia (BPH), and PCa (Tumor) samples were acquired from the Gene Expression Omnibus (GEO). Cellular subsets associated with PCa occurrence were obtained using cell annotation. Additionally, the mRNA expression of nuclear enriched abundant transcript 1 (NEAT1) was detected by quantitative real-time PCR (qRT-PCR). The effects of NEAT1 on cell proliferation and apoptosis were analyzed by 5-ethynyl-2-deoxyuridine (EdU) and flow cytometry. Subsequently, cell-derived xenograft (CDX) models were constructed and divided into the LV-NC and LV-shNEAT1 groups. After the tumor tissues of CDX model mice in each group were extracted, the cell growth and Ki67 expression were observed separately using hematoxylin-eosin (H&E) staining and immunohistochemistry (IHC). Ten cellular subsets were obtained via cell annotation, and significantly differential changes were observed between Basal intermediate and Luminal during the course of BPH to PCa. NEAT1-Luminal was highly recruited in the Tumor group with low stemness and high malignancy scores. Matrix metallopeptidase 7 (MMP7)- keratin 17 (KRT17)-Basal intermediate had high ratios in the Tumor group with low stemness and high malignancy scores. The results of pseudotime analysis revealed that NEAT1-Luminal in the Tumor group were consistently distributed with tumor stage cells. In vitro assays showed that NEAT1 expression was elevated in PCa cells, and NEAT1 knockdown could inhibit cell proliferation and induce apoptosis. CDX assays indicated that silencing NEAT1 could reduce the growth rate of PCa tumor volume in CDX model mice. H&E staining results showed that nuclei of tumor cells were reduced and exhibited lighter color in the LV-shNEAT1 group compared with the LV-NC group. IHC results showed that Ki67 positivity was significantly lower in the LV-shNEAT1 group than in the LV-NC group. NEAT1 expression is increased in PCa, and NEAT1 can be a potential biomarker and therapeutic target for PCa.

12347 Cholesterol Biosynthesis Inhibitor Ro 48-8071 Suppresses Growth Of Triple-negative Breast Cancer Cells By Inducing Apoptosis And Suppressing Angiogenesis

Abstract Disclosure: Y. Liang: None. S.M. Hyder: None. Triple-negative breast cancers (TNBC) lack ER, PR and Her2neu, proteins that are commonly targeted in breast cancer therapies. Women who suffer from TNBC have limited treatment options and are administered toxic chemotherapeutic agents. They have poor prognosis due to the emergence of drug-resistant cells that lead to tumor metastasis. New non-toxic therapeutic strategies to control TNBC progression, and prevent metastasis are urgently needed. Cholesterol is an essential structural and functional component of cell membranes necessary for tumor growth and progression. Therefore, inhibiting cholesterol production is an attractive therapeutic strategy since tumor cells grow rapidly, and need a greater supply of cholesterol. We targeted oxidosqualene cyclase (OSC), an enzyme that occurs downstream of HMGCoA-reductase in the cholesterol biosynthetic pathway, to disrupt tumor growth. RO 48-8071 (4′-[6-(allylmethylamino)hexyloxy]-4-bromo-2′-fluorobenzophenone fumarate) (RO), has emerged as a useful chemotherapeutic agent for treating several forms of primary tumors but its effect on TNBC is not known. Pharmacological doses of RO potently reduced the viability of both MDA-MB-231 and BT20 TNBC cells in a dose dependent manner (1-50 μM). IC50 values for loss of cell viability was approximately 10 μM for both cell lines following 48 h exposure to RO. Doses close to the IC50 for OSC (1-10 nM) also reduced cell viability following exposure of TNBC cells to RO for a week. Importantly, RO had no effect on the viability of normal human mammary cells. FACS analysis revealed that RO dose-dependently induced apoptosis of TNBC cell lines in vitro. In vivo, administration of 5-10 mg/kg RO to mice with BT-20 TNBC cell-derived xenografts (100 mm3) inhibited tumor growth with no apparent toxicity. Immunohistochemical analysis of tumor tissues at the end of treatment showed that RO increased TUNEL expression, suggesting that the in vivo effects of RO were also exerted through mechanisms affecting apoptosis. Furthermore, IHC of tumor sections showed that RO also reduced levels of the angiogenic markers VEGF and CD-31 (blood vessels) in vivo, indicating that suppression of angiogenesis is also part of the mechanism through which RO exerts its anti-tumor effects. We conclude that RO is a potent inhibitor of TNBC and that its anti-tumor effects involve mechanisms that induce apoptosis and suppress angiogenesis. Presentation: 6/2/2024

7559 TRIM21 Regulates Activation of ERK1/2 to Promote Growth and Drug Resistance in Pituitary Neuroendocrine Tumors

Abstract Disclosure: Y. Liu: None. F. Liu: None. C. Li: None. T. Zhang: None. L. Xue: None. Z. Wu: None. Objective: To investigate the role of the TRIM family genes in pituitary neuroendocrine tumors (PitNETs) and provide new targets and strategies for the clinical treatment of these tumors. Methods: A CRISPR screening system targeting the TRIM family was constructed and validated using next-generation sequencing. Stable cell lines overexpressing or knocking out TRIM21 were generated, and functional validation was performed using assays such as CCK-8, colony formation, and xenograft tumor growth in nude mice. RNA-seq, mass spectrometry, immunohistochemistry, and immunoblotting were employed to explore the signaling pathways and mechanisms underlying TRIM21's actions. Immunoprecipitation, immunofluorescence, GST-pulldown, NanoBiT assays, and ubiquitination experiments were conducted to investigate the effects of TRIM21 on ERK1/2. Immunohistochemistry and immunoblotting were used to explore the role of TRIM21 in drug- resistant prolactinomas and the correlation between TRIM21 and p-ERK. Results: Through screening the proliferative and drug-resistant effects of the TRIM family in MMQ and GH3 cells, we found that knocking out TRIM21 may inhibit cell growth and enhance drug sensitivity. Subsequently, stable cell lines overexpressing or knocking out TRIM21 were generated in MMQ and GH3 cells, revealing that TRIM21 overexpression promotes pituitary tumor cell growth and resistance to drug treatment, while TRIM21 knockout inhibits cell growth and enhances drug sensitivity. Cell-derived xenograft models showed that TRIM21 overexpression promoted growth of GH3 cells in vivo and resistance to cabergoline (CAB), while TRIM21 knockout suppressed growth of MMQ cells in vivo. Further exploration of the signaling pathways influenced by TRIM21 revealed that TRIM21 knockout downregulates the MAPK signaling pathway, while TRIM21 overexpression upregulates it. TRIM21 overexpression upregulates p-ERK1/2 in the MAPK pathway, while TRIM21 knockout decreases p-ERK. However, there is no significant influence on ERK1/2, JNK, p-JNK, p38, or p-p38. Mechanically, TRIM21 interacted with ERK1/2, enhancing the K27-linked ubiquitination of ERK1/2 and promoting their interaction with MEK1/2. In addition, the TRIM21 with D-docking mutant or ERK1/2 with CD-domain mutant resulted in the loss of their interaction. Furthermore, TRIM21 and p-ERK levels were significantly elevated in drug-resistant prolactinomas and immunohistochemical semi-quantitative analysis demonstrated a positive correlation between TRIM21 and p-ERK. Conclusion: The ubiquitin ligase TRIM21 catalyzes K27-linked ubiquitination of ERK1/2, enhancing its interaction with MEK1/2 and activation, thereby promoting growth and drug resistance in pituitary neuroendocrine tumors. TRIM21 may serve as a potential target for the treatment of pituitary neuroendocrine tumors. Presentation: 6/3/2024

Pyrotinib and trastuzumab combination treatment synergistically overcomes HER2 dependency in HER2-positive breast cancer: insights from the PHILA trial

The PHILA study suggests that pyrotinib, trastuzumab, and docetaxel significantly improved progression-free survival (PFS) compared with placebo, trastuzumab, and docetaxel in patients with untreated HER2-positive metastatic breast cancer. In this study, we aimed to investigate the synergistic mechanisms of pyrotinib plus trastuzumab and provide further insights for the PHILA trial. The invitro activity of combination treatments was assessed through cell biological and biochemical experiments. The invivo efficacy was evaluated in cell-derived xenografts, a TUBO tumour model, and one clinical case. Next-generation sequencing was performed on circulating tumour DNA (ctDNA) from patients in the PHILA trial. The combination of pyrotinib and trastuzumab more effectively inhibited cell growth than pyrotinib or trastuzumab alone in models of HER2-dependent breast cancer. It potentiated membrane HER2 ubiquitination and downregulation, which resulted in a comprehensive blockade of the HER2 signalling pathway. The pyrotinib-altered membrane HER2 levels had no significant effect on trastuzumab-mediated antibody-dependent cell-mediated cytotoxicity (ADCC). We further validated the synergistic mechanisms in TUBO tumours and one clinical case, rather than models of HCC1954cells harbouring the PIK3CA H1047R mutation. Similarly, in our centre cohort of the PHILA study, patients with genetic alterations in the HER2 signalling cascade had significantly shorter median PFS than individuals with the wild-type pathway. Our findings underscore the robust synergy between pyrotinib and trastuzumab in overcoming HER2 dependency and provide a rationale for pyrotinib, trastuzumab, and docetaxel as one of the optimal choices for patients with untreated HER2-positive metastatic breast cancer, who are dependent on the HER2 signalling cascade. This work was supported by the National Key Research and Development Program of China (2021YFF1201300), the National Natural Science Foundation of China (82172875), the CAMS Innovation Fund for Medical Sciences (CIFMS) (2022-I2M-2-001), and the Joint Innovative Fund of Beijing Natural Science Foundation and Changping District (L234004).

NL101 synergizes with the BCL-2 inhibitor venetoclax through PI3K-dependent suppression of c-Myc in acute myeloid leukaemia

BackgroundAcute myeloid leukaemia (AML) comprises a group of heterogeneous and aggressive haematological malignancies with unsatisfactory prognoses and limited treatment options. Treatments targeting B-cell lymphoma-2 (BCL-2) with venetoclax have been approved for patients with AML, and venetoclax-based drug combinations are becoming the standard of care for older patients unfit for intensive chemotherapy. However, the therapeutic duration of either single or combination strategies is limited, and the development of resistance seems inevitable. Therefore, more effective combination regimens are urgently needed.MethodsThe efficacy of combination therapy with NL101, a SAHA-bendamustine hybrid, and venetoclax was evaluated in preclinical models of AML including established cell lines, primary blasts from patients, and animal models. RNA-sequencing and immunoblotting were used to explore the underlying mechanism.ResultsNL101 significantly potentiated the activity of venetoclax in AML cell lines, as evidenced by the enhanced decrease in viability and induction of apoptosis. Mechanistically, the addition of NL101 to venetoclax decreased the stability of the antiapoptotic protein myeloid cell leukaemia-1 (MCL-1) by inhibiting ERK, thereby facilitating the release of BIM and triggering mitochondrial apoptosis. Moreover, the strong synergy between NL101 and venetoclax also relied on the downregulation of c-Myc via PI3K/Akt/GSK3β signalling. The combination of NL101 and venetoclax synergistically eliminated primary blasts from 10 AML patients and reduced the leukaemia burden in an MV4-11 cell-derived xenograft model.ConclusionsOur results encourage the pursuit of clinical trials of combined treatment with NL101 and venetoclax and provide a novel venetoclax-incorporating therapeutic strategy for AML.

Abstract B045: Sensitizing the PDAC tumor microenvironment to immune checkpoint therapies: characterization of a PDAC 3D model to decipher immune infiltration

Abstract Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal solid tumor with an unfavorable prognosis, often resistant to conventional treatments due to its dense stroma rich in Cancer- Associated Fibroblasts (CAFs). Limited T cell infiltration and prevalence of immunosuppressive cells within the tumor hinder the efficacy of immune checkpoint inhibitors (ICIs). The objective of our project is to modify immune landscape of PDAC tumor microenvironment (TME) to induce ICIs sensitization. We thus develop novel therapeutic strategies combining an immunomodulatory cytokine Interleukine-15 (IL15), with conventional chemotherapies (Gemcitabine or Folfirinox). To accurately replicate the complex cancer-stroma interactions within the pancreatic tumor microenvironment, we constructed a three-dimensional in vitro heterospheroid model composed of xenograft-derived tumor cells from PDAC patients, both primary or immortalized CAFs, and peripheral blood mononuclear cells (PBMCs) from healthy donors. Human 3D models were first set up and characterized by cytometry, imaging mass spectrometry and immunohistochemistry. We showed that, CAFs produce components of the extracellular matrix, promote tumor cell growth, improve resistance to chemotherapy and are able to down-regulate immune cell infiltration and modulate the nature of infiltrated immune cells. Spatial analysis of spheroids using imaging mass cytometry show that CAF influences the distribution of immune cells in our models. Interestingly, Interleukine 15 treatment prompted robust infiltration of PBMCs into heterospheroids. Immunophenotyping experiments revealed a substantial shift in the nature of immune infiltration, marked by a pronounced increase in CD4+ and CD8+ T lymphocytes, gDelta T cell and NK cell populations. When combined with Gemcitabine and IL15, immune effector cell infiltration is remarkably increased, resulting in antitumoral effects and control of tumor cell growth. Moreover, therapeutic combinations induce activation of infiltrated immune effector cells with an increase of activation, degranulation and cytotoxic markers, such as IFNγ, CD107a, and Granzyme B respectively. Thus, the heterotypic spheroids described in our study are a suitable in vitro model to both characterize the influence of CAF on therapeutic effects and the mechanisms that drives immune suppressive microenvironment. Moving forward, the next steps will consist to conduct in vivo experiments using a syngeneic PDAC orthotopic model to assess whether this combined therapeutic approach sensitize the PDAC microenvironment to anti-PD1 therapies. Citation Format: Thomas Bessede, Clara Freixinos, Jennifer Barrat, Véronique Garambois, Nadia Vie, Henri-Alexandre Michaud, Julien Faget, Nathalie Bonnefoy, Céline Gongora, Bruno Robert, Laurent Gros, Christel Larbouret. Sensitizing the PDAC tumor microenvironment to immune checkpoint therapies: characterization of a PDAC 3D model to decipher immune infiltration [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B045.

Abstract B046: Sensitizing the PDAC tumor microenvironment to immune checkpoint therapies: characterization of a PDAC 3D model to decipher immune infiltration

Abstract Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal solid tumor with an unfavorable prognosis, often resistant to conventional treatments due to its dense stroma rich in Cancer- Associated Fibroblasts (CAFs). Limited T cell infiltration and prevalence of immunosuppressive cells within the tumor hinder the efficacy of immune checkpoint inhibitors (ICIs). The objective of our project is to modify immune landscape of PDAC tumor microenvironment (TME) to induce ICIs sensitization. We thus develop novel therapeutic strategies combining an immunomodulatory cytokine Interleukine-15 (IL15), with conventional chemotherapies (Gemcitabine or Folfirinox). To accurately replicate the complex cancer-stroma interactions within the pancreatic tumor microenvironment, we constructed a three-dimensional in vitro heterospheroid model composed of xenograft-derived tumor cells from PDAC patients, both primary or immortalized CAFs, and peripheral blood mononuclear cells (PBMCs) from healthy donors. Human 3D models were first set up and characterized by cytometry, imaging mass spectrometry and immunohistochemistry. We showed that, CAFs produce components of the extracellular matrix, promote tumor cell growth, improve resistance to chemotherapy and are able to down-regulate immune cell infiltration and modulate the nature of infiltrated immune cells. Spatial analysis of spheroids using imaging mass cytometry show that CAF influences the distribution of immune cells in our models. Interestingly, Interleukine 15 treatment prompted robust infiltration of PBMCs into heterospheroids. Immunophenotyping experiments revealed a substantial shift in the nature of immune infiltration, marked by a pronounced increase in CD4+ and CD8+ T lymphocytes, gDelta T cell and NK cell populations. When combined with Gemcitabine and IL15, immune effector cell infiltration is remarkably increased, resulting in antitumoral effects and control of tumor cell growth. Moreover, therapeutic combinations induce activation of infiltrated immune effector cells with an increase of activation, degranulation and cytotoxic markers, such as IFNγ, CD107a, and Granzyme B respectively. Thus, the heterotypic spheroids described in our study are a suitable in vitro model to both characterize the influence of CAF on therapeutic effects and the mechanisms that drives immune suppressive microenvironment. Moving forward, the next steps will consist to conduct in vivo experiments using a syngeneic PDAC orthotopic model to assess whether this combined therapeutic approach sensitize the PDAC microenvironment to anti-PD1 therapies. Citation Format: Thomas Bessede, Clara Freixinos, Jennifer Barrat, Véronique Garambois, Nadia Vie, Henri-Alexandre Michaud, Julien Faget, Nathalie Bonnefoy, Céline Gongora, Bruno Robert, Laurent Gros, Christel Larbouret. Sensitizing the PDAC tumor microenvironment to immune checkpoint therapies: characterization of a PDAC 3D model to decipher immune infiltration [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B046.