Synergistic Antiproliferative Effects Research Articles

Cholangiocyte ciliary defects induce sustained epidermal growth factor receptor signaling.

The primary cilium, an organelle that protrudes from cell surfaces, is essential for sensing extracellular signals. With disturbed cellular communication and chronic liver pathologies, this organelle's dysfunctions have been linked to disorders, including polycystic liver disease (PLD) and Cholangiocarcinoma (CCA). The goal of this study was to elucidate the relationship between primary cilia and the crucial regulator of cellular proliferation, the epidermal growth factor receptor (EGFR) signaling pathway, which has been associated with various clinical conditions. The study identified aberrant EGFR signaling pathways in cholangiocytes lacking functional primary cilia. Using liver-specific IFT88 knockout mice, a Pkhd1 mutant rat model, and human cell lines that didn't have functional cilia. Cilia-deficient cholangiocytes showed persistent EGFR activation because of impaired receptor degradation, in contrast to their normal counterparts, where EGFR localization to the cilia promotes appropriate signaling. Using HDAC6 inhibitors to restore primary cilia accelerates EGFR degradation, thereby reducing maladaptive signaling. Importantly, experimental intervention with the HDAC6 inhibitor tubastatin A in an orthotopic rat model moved EGFR to cilia and reduced ERK phosphorylation. Concurrent administration of EGFR and HDAC6 inhibitors in cholangiocarcinoma and polycystic liver disease cells demonstrated synergistic anti-proliferative effects, which were associated with the restoration of functioning primary cilia. This study's findings shed light on ciliary function and robust EGFR signaling with slower receptor turnover. We could use therapies that restore the function of primary cilia to treat EGFR-driven diseases in PLD and CCA.

Tretinoin synergistically enhances the antitumor effect of combined BRAF, MEK, and EGFR inhibition in BRAFV600E colorectal cancer.

Patients with BRAF-mutated colorectal cancer (BRAFV600E CRC) are currently treated with a combination of BRAF inhibitor and anti-EGFR antibody with or without MEK inhibitor. A fundamental problem in treating patients with BRAFV600E CRC is intrinsic and/or acquired resistance to this combination therapy. By screening 78 compounds, we identified tretinoin, a retinoid, as a compound that synergistically enhances the antiproliferative effect of a combination of BRAF inhibition and MEK inhibition with or without EGFR inhibition on BRAFV600E CRC cells. This synergistic effect was also exerted by other retinoids. Tretinoin, added to BRAF inhibitor and MEK inhibitor, upregulated PARP, BAK, and p-H2AX. When either RARα or RXRα was silenced, the increase in cleaved PARP expression by the addition of TRE to ENC/BIN or ENC/BIN/CET was canceled. Our results suggest that the mechanism of the synergistic antiproliferative effect involves modulation of the Bcl-2 family and the DNA damage response that affects apoptotic pathways, and this synergistic effect is induced by RARα- or RXRα-mediated apoptosis. Tretinoin also enhanced the antitumor effect of a combination of the BRAF inhibitor and anti-EGFR antibody with or without MEK inhibitor in a BRAFV600E CRC xenograft mouse model. Our data provide a rationale for developing retinoids as a new combination agent to overcome resistance to the combination therapy for patients with BRAFV600E CRC.

Discovery of PRMT3 Degrader for the Treatment of Acute Leukemia.

Protein arginine methyltransferase 3 (PRMT3) plays an important role in gene regulation and a variety of cellular functions, thus, being a long sought-after therapeutic target for human cancers. Although a few PRMT3 inhibitors are developed to prevent the catalytic activity of PRMT3, there is little success in removing the cellular levels of PRMT3-deposited ω-NG,NG-asymmetric dimethylarginine (ADMA) with small molecules. Moreover, the non-enzymatic functions of PRMT3 remain required to be clarified. Here, the development of a first-in-class MDM2-based PRMT3-targeted Proteolysis Targeting Chimeras (PROTACs) 11 that selectively reduced both PRMT3 protein and ADMA is reported. Importantly, 11 inhibited acute leukemia cell growth and is more effective than PRMT3 inhibitor SGC707. Mechanism study shows that 11 induced global gene expression changes, including the activation of intrinsic apoptosis and endoplasmic reticulum stress signaling pathways, and the downregulation of E2F, MYC, oxidative phosphorylation pathways. Significantly, the combination of 11 and glycolysis inhibitor 2-DG has a notable synergistic antiproliferative effect by further reducing ATP production and inducing intrinsic apoptosis, thus further highlighting the potential therapeutic value of targeted PRMT3 degradation. These data clearly demonstrated that degrader 11 is a powerful chemical tool for investigating PRMT3 protein functions.

Daidzein nanosuspension combined with 5-fluorouracil induces apoptosis and alleviate inflammation in Caco-2 colorectal adenocarcinoma cells

Colorectal cancer is the third most common malignancy worldwide and the second most common cause of cancer deaths. Alternative treatment strategies, including nano-based formulations, show remarkable promise to improve the efficacy of chemotherapy. The soy isoflavone daidzein has attracted attention for its anti-cancer activity. The aim of this study was to investigate the effects of daidzein nanosuspension with 5-fluorouracil on apoptosis and inflammation induced in human colorectal adenocarcinoma cells (Caco-2). Cytotoxicity, total antioxidant/oxidant status (TAS, TOS), and the expression of proteins associated with apoptosis and inflammation were analyzed by the MTT, ELISA and qRT-PCR, respectively. Daidzein nanosuspension showed a strong cytotoxicity (IC50 = 240.3 μM for daidzein, IC50 = 35.34 μM for daidzein nanosuspension) compared to daidzein. The combination of 5-fluorouracil and daidzein nanosuspension treatment showed a synergistic antiproliferative effect without increasing oxidative stress. The combination showed a significant increase in p53 levels and a significant decrease in Bcl-2, IL-6, TNF-α and MMP-9 levels. qRT-PCR results showed that the combinations of daidzein and DZ-NS with 5-FU regulated these parameters in Caco-2 cells. In conclusion, daidzein nanosuspension with 5-fluorouracil treatment reduced the proliferation and inflammation and increased apoptosis of Caco-2 cells without oxidative stress. The current study shows that this combination also elucidates several signaling pathways, including effects on oxidative stress, apoptosis, and inflammation. The integration of this nanotechnology approach into traditional chemotherapy will form the basis of an innovative strategy.

REST Promotes Autophagy in Gastric Cancer by Transcriptionally Activating FABP6 to Inhibit the Akt/mTOR Signaling Pathway.

Gastric cancer (GC) is a leading cause of cancer-associated death worldwide. Its molecular mechanisms, especially concerning autophagy and various signaling pathways, are not fully understood. Fatty Acid Binding Protein 6 (FABP6) and RE1 Silencing Transcription Factor (REST) emerge as potential key players in this context. This study sought to analyze the functional relationship of FABP6 and REST concerning autophagy and their implications on the Akt/mTOR signaling pathway within GC cells. A comprehensive bioinformatics approach was used to identify key prognostic markers in GC. The effects of FABP6 and REST on autophagy along with Akt/mTOR signaling pathways were analyzed by techniques including Western blotting (WB), flow cytometry, Transwell assay, dual luciferase reporter assay, and others. FABP6 was identified as overexpressed in GC, linked with poor prognosis. FABP6 silencing reduces GC cell proliferation, induces S- and G2-phase arrest, and downregulates cyclins CDK2 and CDK4. It also inhibited GC cell invasion/migration and autophagy, effects that were counteracted by MG132. When combined with PI3K inhibitor LY294002c, FABP6 knockdown showed synergistic anti-proliferative effects, modulating the Akt/mTOR pathway. Besides, the transcription factor REST has been shown to directly regulate FABP6 expression, affecting autophagy and the Akt/mTOR signaling pathway in a FABP6-dependent manner. REST positively regulates autophagy and negatively affects the Akt/mTOR signaling pathway in GC cells in a FABP6-dependent manner, providing valuable insights into regulatory networks involving FABP6 and REST.

WEE Family Kinase Inhibitors Combined with Sorafenib Can Selectively Inhibit HCC Cell Proliferation

Background: Sorafenib is currently the first choice for the treatment of patients with advanced hepatocellular carcinoma, but its therapeutic effect is still limited. Objectives: This study aims to examine whether WEE family kinase inhibitors can enhance the anticancer effect of sorafenib. Methods: We analyzed the expression levels of PKMYT1 kinase and WEE1 kinase in HCC, studied the inhibitory effect of PKMYT1 kinase inhibitor RP-6306, WEE1 kinase inhibitor adavosertib combined with sorafenib on the proliferation of HCC cells, and detected the effect of drug combination on CDK1 phosphorylation. Results: We found that PKMYT1 and WEE1 were upregulated in HCC and were detrimental to patient survival. Cell experiments showed that both RP-6306 and adavosertib (1-100 μM) inhibited the proliferation of HCC cell lines in a dose-dependent manner alone, and the combination of the two drugs had a synergistic effect. In HCC cell lines, sorafenib combined with RP-6306 or adavosertib showed a synergistic antiproliferation effect and less toxicity to normal cells. Sorafenib combined with RP-6306 and adavosertib further inhibited the proliferation of HCC cells and caused complete dephosphorylation of CDK1. Conclusion: Taken together, our findings provide experimental evidence for the future use of sorafenib in combination with RP-6306 or adavosertib for the treatment of HCC.

Abstract PR012: KAT6A/B and Menin-MLL complexes coordinately regulate estrogen receptor-driven gene expression programs in breast cancer

Abstract The estrogen receptor (ER) is expressed in ∼70% of breast cancers where it functions as a critical transcription factor that regulates cell growth and tumor progression. ER inhibition is a mainstay treatment for ER-positive (ER+) breast cancer, but despite the clinical benefit of targeting ER signaling, breast cancer remains the second leading cause of cancer-related death in women, with ∼50% of deaths resulting from ER+ tumors. While recurrent and metastatic ER+ tumors are typically resistant to endocrine therapies they continue to rely on ER signaling suggesting that disruption of other chromatin associated complexes that mediate ER-driven gene expression may present an alternative therapeutic strategy. One chromatin modifier important in regulating ER function is the histone acetyltransferase KAT6A. KAT6A is amplified and/or overexpressed in ∼15% of ER+ tumors and a novel KAT6A/B inhibitor has entered clinical trials for advanced breast cancer. However, as with most single agent therapies, compensatory mechanisms may attenuate the effects of KAT6A/B inhibition on ER-driven gene expression. We hypothesized that the dual targeting of distinct chromatin complexes would enhance the effects of KAT6A/B inhibition, by altering chromatin state and transcriptional output. To that end we performed an epigenetic focused CRISPR-Cas9-based functional genetic screen to identify chromatin-associated proteins that enhance KAT6A/B inhibition. CRISPR guides targeting MEN1 (encoding Menin) were among our top hits as sensitizers to treatment with the KAT6A/B inhibitor PF-9363. We confirmed that co-treatment of PF-9363, and the Menin inhibitor, SNDX-5613, had strong synergistic anti-proliferative effects in a panel of ER+ breast cancer cell lines. Mechanistically, our data revealed that KAT6A/B and Menin cooperatively regulate ER-driven gene expression and chromatin accessibility, both through direct effects on ESR1 expression as well as through effects at ER target genes. Specifically, we found that KAT6A and Menin-KMT2A complexes co-localized at promoters of ER target genes and treatment with KAT6A/B or Menin inhibitors displaced KAT6A and Menin/KMT2A from ER target genes, respectively. Yet only the combination effectively displaced both complexes from chromatin, which produced more dramatic changes in ER-directed gene expression than either small molecule alone. Combined displacement of KAT6A and Menin/KMT2A at ER-regulated genes induced loss of an active chromatin landscape characterized by reduction of activating histone modifications and loss of RNA Polymerase II binding to ER target loci. Importantly, the combination of KAT6A/B and Menin inhibition was effective in a panel of ER+ patient-derived organoid models as well as in various models of endocrine resistance, including models with ESR1 mutations, NF1 loss, and FOXA1 mutations. Both KAT6A/B and Menin inhibitors are in Phase I/II clinical trials and have shown manageable toxicity profiles to date. This combination represents a novel potential therapeutic combination for ER+ breast cancer. Citation Format: Sarah Naomi Olsen, Bryn Anderson, Charles Hatton, Rinath Jeselsohn, Myles Brown, Eneda Toska, Scott Armstrong. KAT6A/B and Menin-MLL complexes coordinately regulate estrogen receptor-driven gene expression programs in breast cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr PR012.

Co-Delivery of an Innovative Organoselenium Compound and Paclitaxel by pH-Responsive PCL Nanoparticles to Synergistically Overcome Multidrug Resistance in Cancer.

In this study, we designed the association of the organoselenium compound 5'-Seleno-(phenyl)-3'-(ferulic-amido)-thymidine (AFAT-Se), a promising innovative nucleoside analogue, with the antitumor drug paclitaxel, in poly(ε-caprolactone) (PCL)-based nanoparticles (NPs). The nanoprecipitation method was used, adding the lysine-based surfactant, 77KS, as a pH-responsive adjuvant. The physicochemical properties presented by the proposed NPs were consistent with expectations. The co-nanoencapsulation of the bioactive compounds maintained the antioxidant activity of the association and evidenced greater antiproliferative activity in the resistant/MDR tumor cell line NCI/ADR-RES, both in the monolayer/two-dimensional (2D) and in the spheroid/three-dimensional (3D) assays. Hemocompatibility studies indicated the safety of the nanoformulation, corroborating the ability to spare non-tumor 3T3 cells and human mononuclear cells of peripheral blood (PBMCs) from cytotoxic effects, indicating its selectivity for the cancerous cells. Furthermore, the synergistic antiproliferative effect was found for both the association of free compounds and the co-encapsulated formulation. These findings highlight the antitumor potential of combining these bioactives, and the proposed nanoformulation as a potentially safe and effective strategy to overcome multidrug resistance in cancer therapy.

Dual targeting of glutamine and serine metabolism in acute myeloid leukemia.

Acute myeloid leukemia (AML) is a heterogeneous hematological malignancy characterized by disrupted blood cell production and function. Recent investigations have highlighted the potential of targeting glutamine metabolism as a promising therapeutic approach for AML. Asparaginases, enzymes that deplete circulating glutamine and asparagine, are approved for the treatment of acute lymphoblastic leukemia, but are also under investigation in AML, with promising results. We previously reported an elevation in plasma serine levels following treatment with Erwinia-derived asparaginase (also called crisantaspase). This led us to hypothesize that AML cells initiate the de novo serine biosynthesis pathway in response to crisantaspase treatment and that inhibiting this pathway in combination with crisantaspase would enhance AML cell death. Here we report that in AML cell lines, treatment with the clinically available crisantaspase, Rylaze, upregulates the serine biosynthesis enzymes phosphoglycerate dehydrogenase (PHGDH) and phosphoserine aminotransferase (PSAT1) through activation of the Amino Acid Response (AAR) pathway, a cellular stress response mechanism that regulates amino acid metabolism and protein synthesis under conditions of nutrient limitation. Inhibition of serine biosynthesis through CRISPR-Cas9-mediated knockout of PHGDH resulted in a ~250-fold reduction in the half-maximal inhibitory concentration (IC50) for Rylaze, indicating heightened sensitivity to crisantaspase therapy. Treatment of AML cells with a combination of Rylaze and a small molecule inhibitor of PHGDH (BI4916) revealed synergistic anti-proliferative effects in both cell lines and primary AML patient samples. Rylaze-BI4916 treatment in AML cell lines led to the inhibition of cap-dependent mRNA translation and protein synthesis, as well as a marked decrease in intracellular glutathione levels, a critical cellular antioxidant. Collectively, our results highlight the clinical potential of targeting serine biosynthesis in combination with crisantaspase as a novel therapeutic strategy for AML.

Selective impact of ALK and MELK inhibition on ERα stability and cell proliferation in cell lines representing distinct molecular phenotypes of breast cancer

Breast cancer (BC) is a leading cause of global cancer-related mortality in women, necessitating accurate tumor classification for timely intervention. Molecular and histological factors, including PAM50 classification, estrogen receptor α (ERα), breast cancer type 1 susceptibility protein (BRCA1), progesterone receptor (PR), and HER2 expression, contribute to intricate BC subtyping. In this work, through a combination of bioinformatic and wet lab screenings, followed by classical signal transduction and cell proliferation methods, and employing multiple BC cell lines, we identified enhanced sensitivity of ERα-positive BC cell lines to ALK and MELK inhibitors, inducing ERα degradation and diminishing proliferation in specific BC subtypes. MELK inhibition attenuated ERα transcriptional activity, impeding E2-induced gene expression, and hampering proliferation in MCF-7 cells. Synergies between MELK inhibition with 4OH-tamoxifen (Tam) and ALK inhibition with HER2 inhibitors revealed potential therapeutic avenues for ERα-positive/PR-positive/HER2-negative and ERα-positive/PR-negative/HER2-positive tumors, respectively. Our findings propose MELK as a promising target for ERα-positive/PR-positive/HER2-negative BC and highlight ALK as a potential focus for ERα-positive/PR-negative/HER2-positive BC. The synergistic anti-proliferative effects of MELK with Tam and ALK with HER2 inhibitors underscore kinase inhibitors’ potential for selective treatment in diverse BC subtypes, paving the way for personalized and effective therapeutic strategies in BC management.

Abstract LB159: Discovery of HP560, a novel BET inhibitor for the treatment of myelofibrosis

Abstract Myelofibrosis (MF) is a myeloproliferative neoplasm characterized by defective clonal hematopoiesis, bone marrow fibrosis, splenomegaly, severe anemia, and the propensity for transformation to acute myeloid leukemia (AML). Inhibitors targeting JAKs (Janus kinases) have revolutionized the treatment of MF, but are limited by modest efficacy or acquired resistance after prolonged treatment. Here, we report a novel inhibitor, HP560 that targets BET (bromodomain and extra-terminal) proteins and shows promising therapeutic activities against MF and AML. Through engaging the bromodomain pocket of BET proteins in a competitive manner with acetylated histones, HP560 causes the disruption of BET proteins from chromatin. HP560 has high binding affinities for all BET proteins and strong anti-proliferative activity as well as synergistic anti-proliferative effect in combination with ruxolitinib, a JAK1/2 inhibitor. In an MF cell line derived tumor xenograft (CDX) mouse model, HP560 prolongs survival and improves splenomegaly and anemia, and these effects are enhanced when combined with ruxolitinib. HP560 also significantly and dose-dependently inhibits tumor growth in an AML CDX mouse model. Together, HP560 is a potent pan-BET inhibitor and can be developed as a monotherapy or in combination with a JAK inhibitor for the treatment of MF. HP560 structure will not be disclosed. Citation Format: Jing Li, Lei Fan, Hongwei Yuan, Yongxu Huo, Hua Yu, Fei Wang, Xinghai Li. Discovery of HP560, a novel BET inhibitor for the treatment of myelofibrosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB159.

Abstract LB294: Targeting fatty acid oxidation to boost the anti-tumor effects of nutrient starvation in solid malignancies

Abstract Introduction Reducing glucose and growth factor provision to cancer cells through in vitro starvation (STV) or in vivo fasting/fasting-mimicking diets (FMDs) delays tumor progression and prolongs survival in tumor-bearing mice. More recently, cyclic FMD has been shown to be safe and associated with promising metabolic and immunomodulatory effects in cancer patients. However, cyclic fasting and FMD only retard tumor progression, but they do not result in tumor cure when used alone. Here, we hypothesized that tumor cells exposed to STV activate Fatty Acid Oxidation (FAO) as an alternative metabolic pathway that could be responsible for primary or acquired tumor cell resistance to STV. Methods We investigated the effects of FAO inhibition (FAOi) in combination with STV on the proliferation and survival of human or murine cell lines of Triple Negative Breast Cancer (TNBC) (n=16), HR+HER2- breast cancer (n=3), colorectal (n=1), pancreatic (n=1) and lung cancer (n=1), as well as of non-transformed human epithelial cells (n=3). STV consisted of a 50% reduction of extracellular glucose and serum in cell growth media. To inhibit FAO, we used the Carnitine Palmitoyl transferase 1 inhibitor Etomoxir or ST1326. Results STV+FAOi resulted in cooperative or highly synergistic antiproliferative effects in all cancer models tested, but not in normal cells. At longer time points, STV+FAOi enhanced tumor cell death through the activation of apoptosis. Depending on the specific tumor type, the cooperative effects of STV and FAOi were mostly mediated by glucose or fatty acid restriction in the STV medium. On the other hand, the reduction of extracellular growth factors did not affect cell proliferation upon STV+FAOi combination. Intracellular ATP levels were reduced upon cell exposure to the combined treatment at later time points. However, the supplementation of several sources of ATP, such as glutamine or TCA cycle intermediates, to tumor cells did not rescue the antitumor effects of STV+FAOi, thus excluding the strong impact of this combination on tumor cell bioenergetics. On the other hand, STV+FAOi caused an excessive intracellular antioxidant response, which in part mediated the synergistic effects of STV+FAOi. Indeed, Etomoxir alone mildly increased the NADPH/NADP+ ratio, whereas its combination with STV resulted in a remarkable increase of this ratio. In parallel, combining the antioxidant molecules n-acetylcysteine (NAC) and reduced glutathione (GSH) with FAOi caused antitumor effects that recapitulate those produced by STV+FAOi treatment. Conclusions FAO is a potential resistance mechanism to nutrient starvation, with broad antitumor activity in different models of murine and human malignancies, but not in normal cells. In cancer cells, FAOi synergizes with STV by strongly affecting intracellular redox balance. FAOi is a new strategy that should be explored in future preclinical in vivo experiments and in clinical studies to potentiate the antitumor effects of nutrient starvation in solid malignancies. Citation Format: Marzia Santamaria, Beatrice Cantarelli, Arta Ajazi, Chiara Milanese, Giulia Salvadori, Pier Giorgio Mastroberardino, Paola Antonia Corsetto, Giancarlo Pruneri, Filippo De Braud, Claudio Vernieri. Targeting fatty acid oxidation to boost the anti-tumor effects of nutrient starvation in solid malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB294.

Abstract 688: Radium-223 in combination with darolutamide exhibits synergistic antitumor efficacy in LNCaP prostate cancer models

Abstract Radium-223 dichloride (radium-223) is a targeted alpha therapy that binds to newly formed abnormal bone in bone metastases and induces DNA double-strand breaks (DSBs) in cancer cells, osteoblasts and osteoclasts. Radium-223 is used for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC). Darolutamide is an androgen receptor inhibitor indicated for patients with metastatic hormone-sensitive prostate cancer or non-metastatic CRPC. We studied the antitumor effects of radium-223 in combination with darolutamide using LNCaP human prostate cancer cells in vitro and an intratibial LNCaP model mimicking prostate cancer metastasized to bone. The in vitro antiproliferative effects of radium-223 and darolutamide were determined using LNCaP cells. Gene set enrichment analysis (GSEA) was conducted on RNA sequencing data from LNCaP cells treated with the synthetic androgen R1881 alone or in combination with darolutamide. LNCaP cells were inoculated into the right tibia of male NOD.scid mice. The mice (n=7-9/group) were randomized based on serum prostate-specific antigen (PSA) and treated with vehicle, radium-223 (330 kBq/kg, Q4Wx2, i.v.), darolutamide (100 mg/kg, BID, p.o.), or with a combination of radium-223 and darolutamide, for 41 days. PSA and the bone turnover markers PINP and CTX-I were measured every second week in serum. Tumor-induced abnormal bone area, bone formation rate and radium-223 uptake in tumor-bearing tibiae were determined by X-ray, histomorphometry and gamma counter, respectively. The combination of radium-223 and darolutamide showed synergistic antiproliferative effects with combination indexes between 0.69-0.75 in vitro. GSEA demonstrated a prominent darolutamide-induced downregulation of DNA damage response (DDR) signaling pathways. In vivo, the combination treatment showed synergistic antitumor efficacy (p=0.04) as demonstrated by lower PSA concentrations when compared with the vehicle, radium-223 or darolutamide monotherapies (p=0.004, p=0.011 and p=0.002, respectively). In the vehicle and combination treatment groups, the mean serum PSA was 541% and 95.9% of the pre-treatment level, respectively. Furthermore, radium-223 alone or in combination with darolutamide inhibited increased bone turnover, tumor-induced abnormal bone growth and trabecular bone formation when compared to vehicle. Concurrent administration of darolutamide did not affect radium-223 uptake in tibiae. Radium-223 in combination with darolutamide exhibited synergistic antitumor efficacy both in vitro and in vivo. The synergistic effects could be due to the radiosensitization of cancer cells by darolutamide-induced downregulation of DDR pathways. Our results suggest that the combination of targeted alpha therapy with an androgen receptor inhibitor is a promising treatment strategy for mCRPC. Citation Format: Christoph A. Schatz, Mari I. Suominen, Andreas Schlicker, Matias Knuuttila, Esa Alhoniemi, Sanna-Maria Käkönen, Bernard Haendler, Urs B. Hagemann, Arne Scholz. Radium-223 in combination with darolutamide exhibits synergistic antitumor efficacy in LNCaP prostate cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 688.

Abstract 3324: Discovery of a novel SOS1 inhibitor, AIG01012, targeting pan-KRAS mutant cancers

Abstract Targeting the SOS1-KRAS interaction represents a pivotal strategy in mitigating aberrant KRAS signaling, which is implicated in numerous malignancies. At AIGEN Sciences, Inc., we have harnessed an advanced human-in-the-loop (HITL) AI-based drug discovery platform (AIGEN ChemTailor). This innovative platform allows online learning through expert feedback, optimizing our drug development endeavors. We designed a potent SOS1 inhibitor, AIG01012 using AIGEN ChemTailor in combination with fragment-based drug discovery (FBDD) and molecular modeling techniques. We conceived numerous compounds and shortlisted the leading candidates for extensive testing after meticulous computer simulations. AIG01012 manifested substantial inhibitory effects against several KRAS mutant interactions with SOS1, specifically SOS1-KRAS WT, SOS1-KRAS G12C, SOS1-KRAS G12D, SOS1-KRAS G12V, and SOS1-KRAS G13D. However, its inhibitory capacity did not extend to the SOS2-KRAS G12C interaction. AIG01012 demonstrated remarkable inhibitory effects in 3D cell proliferation assays across various cell lines, including H358, MIA-PaCa2, SW837, AsPC-1, A427, SW620, Capan-2, A549, DLD-1, MKN-1, and H1666. Moreover, AIG01012 showed synergistic antiproliferative effects when combined with approved drugs such as sotorasib (for lung cancer with KRAS mutations), trametinib (a MEK inhibitor), and Osimertinib (targets specific EGFR mutations) in either H358 or PC-9 cell lines. Mouse studies further confirmed its favorable pharmacological properties, and its efficacy was evaluated in subsequent mouse tumor model. In summary, utilizing our human-in-the-loop (HITL) AI platform, AIGEN ChemTailor, we have efficiently derived AIG01012 as a potent SOS1 inhibitor that targets a wide range of KRAS interactions. With its notable in vitro and in vivo outcomes, AIG01012 is set for further exploration and prospective clinical trials as a significant contender in KRAS-targeted cancer treatments. Citation Format: Jihye Kim, Sejeong Park, Sunkyu Kim, Sanghoon Lee, Kiwoong Yoo, Ho-Jeong Lee, Jaewoo Kang, Kwang-Ok Lee. Discovery of a novel SOS1 inhibitor, AIG01012, targeting pan-KRAS mutant cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3324.

Abstract 4569: APG-2449, a novel focal adhesion kinase (FAK) inhibitor, inhibits metastasis and enhances the antitumor efficacy of PEGylated liposome doxorubicin (PLD) in epithelial ovarian cancer (EOC)

Abstract Ovarian cancer is the leading cause of cancer-related death in women and most cases are diagnosed at later stages, with distant metastasis. Standard-of-care therapy is surgery followed by platinum and paclitaxel; however, most patients who initially respond to therapy eventually relapse after developing metastatic disease and chemoresistance. FAK overexpression or activation occurs in a substantial proportion of EOCs and is predictive of poor clinical outcomes. Recent studies have reported that FAK plays an important role in cell migration and chemoresistance, rendering FAK inhibition a promising treatment approach to reduce metastasis of tumor cells and sensitize them to chemotherapy. The aim of this study was to evaluate the antitumor efficacy of investigational APG-2449, a novel FAK inhibitor, combined with PLD, a commonly used chemotherapy, in relapsed or refractory ovarian cancer. Four EOC cell lines (OVCAR-3, SK-OV-3, A2780, and Kuramochi) were used for in vitro experiments. Cell proliferation was measured by CellTiter-Glo assays. Cell migration ability was assessed by wound healing assays. OVCAR-3 xenograft and luciferase-tagged ID8 (ID8-Luc) peritoneal syngeneic models were established to evaluate the synergistic antitumor efficacy of combined APG-2449 and PLD in vivo. APG-2449 combined with doxorubicin showed synergistic antiproliferative effects in both platinum-resistant (OVCAR-3 and SK-OV-3) and platinum-sensitive (A2780 and Kuramochi) cell lines. In wound healing assays, FAK inhibition via APG-2449 alone attenuated migration of ovarian cancer cells (SK-OV-3, OVCAR-3, and ID8-Luc) in a dose-dependent manner. In the OVCAR-3 xenograft model, combined APG-2449 and PLD demonstrated enhanced antitumor effects compared with either APG-2449 or PLD monotherapy (synergistic index, 1.33). In the ID8-Luc peritoneal syngeneic model, the combination regimen outperformed PLD or APG-2449 monotherapy in tumor growth inhibition. This inhibitory effect persisted more than 1 month after stopping combination treatment, whereas the monotherapy groups experienced rapid disease relapse. The combination group also exhibited the longest ascites-free and survival times compared with PLD or APG-2449 monotherapy groups. Overall, our data suggest that inhibition of FAK by APG-2449 enhances the antitumor effect of PLD in EOC cell lines and the OVCAR-3 xenograft mouse model. The combination regimen can also prolong ascites-free and survival times, as shown in the ID8-Luc peritoneal syngeneic model. These promising results support future clinical development of this combination treatment for ovarian cancer. Citation Format: Zhou Yu, Eric Liang, Daojie Liu, Bingxing Wu, Xinyi Yao, Yanqiu Ji, Dajun Yang, Yifan Zhai. APG-2449, a novel focal adhesion kinase (FAK) inhibitor, inhibits metastasis and enhances the antitumor efficacy of PEGylated liposome doxorubicin (PLD) in epithelial ovarian cancer (EOC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4569.

Abstract 4532: Discovery of DAT-1000A, a potent Polθ inhibitor that significantly enhances anti-tumor efficacy in combination with PARP inhibitor in homologous-recombination-deficient tumors

Abstract Cancers exhibiting homologous recombination (HR) repair deficiencies due to mutations in genes like BRCA1 or BRCA2 rely on alternative DNA damage response (DDR) pathways to uphold genomic integrity. This vulnerability allows for the targeted disruption of these pathways through synthetic lethality approaches. DNA polymerase theta (Polθ, encoded by POLQ) assumes a crucial role in mending DNA double-strand breaks (DSB) via microhomology-mediated end-joining (MMEJ), one of the principal pathways for repairing DNA DSB. Notably, Polθ expression is minimal in normal tissues but becomes upregulated in HR-deficient cancer cells, positioning Polθ as a prime target for synthetic lethality in HRD cancers. Reversion mutations in HR-related genes frequently employ micro-homology deletion mechanisms. Consequently, the inhibition of Polθ holds the potential to thwart the emergence of PARPi resistance, primarily driven by BRCA reversion mutations. In this context, we introduce DAT-1000A, a novel small-molecule Polθ inhibitor exhibiting potent activity with a single-digital nanomolar IC50 value. Its efficacy in MMEJ functional assays validates its on-target cellular activity. Assessments of cell viability in HR-deficient BRCA2-KO DLD-1 cells, compared to their parental counterparts, reveal a striking synthetic lethality window exceeding 500-fold. Additionally, DAT-1000A displays synergistic anti-proliferative effects when combined with PARP inhibitors in BRCA1/2-mutated cells. In BRCA1/2-mutated xenograft models, DAT-1000A demonstrates robust and sustained tumor regression, as evidenced by the level of γH2AX, a common marker for double-strand breaks, which closely correlates with anti-tumor efficacy. Importantly, high-dose DAT-1000A treatment in mice elicits no significant abnormalities, underscoring its excellent tolerability. Collectively, DAT-1000A emerges as a novel Polθ inhibitor, offering both potent activity and a favorable safety profile, and holds promise for advancing therapeutic options in the realm of HRD cancer treatment. Citation Format: Dan Yan, Yao Zhang, Yan Zhang, Jingxi Zhang, Bin Wang, Huixian Chen, Jingxue Shi, Xiaoling Lin, Jincong Zhuo, Kevin Zhou. Discovery of DAT-1000A, a potent Polθ inhibitor that significantly enhances anti-tumor efficacy in combination with PARP inhibitor in homologous-recombination-deficient tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4532.

Abstract 5714: Synergistic effect of the CDC7 inhibitor, monzosertib (AS-0141) with current therapies in AML models

Abstract Introduction: Cell division cycle 7 (CDC7) is a highly conserved serine-threonine kinase that plays an important role in the initiation of DNA replication and cell cycle progression. Aberrant expression of CDC7 have been reported to cause uncontrolled proliferation of many cancer types, suggesting that CDC7 inhibitors may provide a great potential for the development of novel therapy for cancers. Monzosertib (AS-0141) is a potent, selective, orally bioavailable small molecule inhibitor of CDC7, and is currently being evaluated in Phase I study for the treatment of solid tumors. In a preclinical cancer cell panel study, monzosertib showed strong antiproliferative activities against a variety of cancer types, and acute myeloid lymphoma (AML) cell lines were found to be the most sensitive to monzosertib. As a single agent, treatment with monzosertib accumulates DNA damage in cancer cells and induces cell death. In this study, we aimed to investigate the antitumor effects of monzosertib alone and in combination with other anticancer drugs in AML models. Method: Antiproliferative activity of monzosertib was examined against a panel of 35 human cancer cell lines of various cancer types. DNA metyltransferase (DNMT) inhibitors (azacitidine or decitabine) and BCL2 inhibitor (venetoclax) were evaluated for their synergistic/antagonistic effects in combination with monzosertib against human AML cell lines (THP-1, HL-60, MV4-11, MOLM-14, TF-1, U-937 and NOMO-1). The combination index (CI) was calculated using the Chou-Talalay method. Flow cytometry assay was used to analyze apoptosis. To evaluate the in vivo efficacy, tumor-bearing mice were treated with monzosertib alone or in combination with venetoclax. Results: The combination of monzosertib with azacitidine, decitabine, or venetoclax resulted in a significant synergistic antiproliferative effects against AML cell lines in vitro. The flow cytometry assay indicated that azacitidine combination induced apoptosis and increased cell death in THP-1 cells. In vivo, oral administration of monzosertib demonstrated robust in vivo antitumor efficacy in a MV4-11 tumor bearing xenograft mouse model, both as a single agent and in combination with venetoclax. Conclusions: Monzosertib, a selective CDC7 inhibitor, demonstrated strong antiproliferative activity against human AML cell lines, both as a single agent and in combination with standard therapies. Monzosertib exerts synergistic antitumor effect with venetoclax in a human AML xenograft mouse model. These results suggest that monzosertib has a potential to enhance the antitumor efficacy of standard of care agents for AML patients. Citation Format: Hiroko Endo, Hatsuo Furuichi, Akinori Arimura, Yu Nishioka, Masaaki Sawa. Synergistic effect of the CDC7 inhibitor, monzosertib (AS-0141) with current therapies in AML models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5714.

Abstract 4564: Therapeutic potential of SOS1 and KRAS inhibitors in malignant peripheral nerve sheath tumors

Abstract Neurofibromatosis type 1 (NF1) is a genetic disorder that affects the nervous system. It is caused by mutations in the NF1 gene. NF1 loss of function leads to elevated RAS signaling, which plays a crucial role in cell growth and proliferation. Due to the dysregulated RAS signaling, individuals with NF1 are prone to the development of neurofibromas. These neurofibromas are typically benign and called Plexiform Neurofibromas (PNFs), in some cases, they can transform into malignant peripheral nerve sheath tumors (MPNSTs). MPNSTs are highly aggressive and invasive cancers that contribute to a significant proportion of soft tissue sarcomas. The exact mechanisms behind this transformation are not fully understood, however it involves additional genetic mutations and alterations in cellular signaling pathways. With limited effective targeted therapies available, surgical removal remains the primary treatment option. However, due to tumor size and location, surgery may not always be feasible. The MEK inihibitor, selumetinib, has received approval for the treatment of PNFs, however some patients who were treated with selumetinib continued to develop MPNSTs suggesting that MEK inhibitors may have limitations in addressing MPNSTs. To target the RAS pathway and mitigate the effects of NF1 gene alterations, we aim to explore the therapeutic potential of two novel, potent and orally bioavailable small molecule inhibitors targeting SOS1 (BI 1701963) or KRAS (KRASmulti inhibitor BI 3706674), as alternative treatment options for MPNSTs. The KRASmulti inhibitor BI 3706674 binds non-covalently to the KRAS wild type allele as well as multiple KRAS mutant alleles in the GDP-bound state and thereby disrupts KRAS signaling. Therefore, we hypothesize that both inhibitors will work in NF1 models by reducing activated KRAS levels. In this study, a series of in vitro and in vivo experiments were conducted to evaluate the efficacy of BI 1701963 and BI 3706674 inhibitors, both individually and in combination. The studies were done in comparison to the MEK inhibitor selumetinib. In vitro analysis revealed a synergistic anti-proliferative effect when combining BI 1701963 and BI 3706674 inhibitors both in 2D and 3D growth conditions, which led to the downregulation of the RAS pathway, specifically the MAPK and PI3K signaling cascade, and an increase in apoptosis. The in vivo efficacy of either BI 1701963 or BI 3706674 inhibitor alone or in combination was tested in four different in vivo MPNST models. We observed significant tumor growth stabilization as well as tumor regression in all tested models in vivo. In-depth pathway modulation and pharmaco-dynamic studies are ongoing. In conclusion, this study highlights the combined effects of SOS1 (BI 1701963) and KRAS (BI 3706674) inhibition in MPNSTs. The combination therapy of these novel therapeutics may hold promise as a potential treatment strategy for patients with MPNSTs. Citation Format: Özlem Yüce Petronczki, Laura Pisarsky, Petra Lujza Szabó, Julia Brunmair, Antonia Geyer, Norbert Kraut, Darryl McConnell, Irene Waizenegger. Therapeutic potential of SOS1 and KRAS inhibitors in malignant peripheral nerve sheath tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4564.

Ellagic acid nanoliposomes potentiate therapeutic effects of PEGylated liposomal doxorubicin in melanoma: An in vitro and in vivo study

Combination therapy is a promising strategy to enhance the efficacy of cancer treatment. Polyphenolic compounds including Ellagic acid (EA) have shown significant efficacy against several types of cancers. Despite considerable anti-tumor activity, the low aqueous solubility of EA hinders its application in cancer therapy. In the current study, we report on the preparation and characterization of EA liposome (EA Lip) and its combination with doxorubicin liposomes (Doxil) against B16F0 melanoma tumor in vitro, and in vivo in C57/BL6 mice model. In vitro study showed synergistic effects of EA Lip/Doxil combination at both 7:1 and 30:1 M ratios following 48 and 72 h incubation with B16F0 cells. For in vivo therapeutic efficacy, mice received a single intravenous injection of Doxil (5 mg/kg), EA Lip (3 mg/kg) and EA Lip/Doxil combination at 3 and 5 mg/kg, respectively, through the tail vein. In vivo results indicated a significant tumor shrinkage in mice received EA Lip in combination with Doxil compared to EA Lip or Doxil alone. Based on the survival data, combination therapy prolonged the survival of animals and the tumor growth delay percentage was reported to be 37.3% for the combination versus 24 and 14.6% for Doxil and EA Lip, respectively. These results laid emphasis on the benefits of combination strategy to improve the therapeutic outcome. Further studies however are warranted to elucidate the mechanism involved in the synergistic anti-proliferative effects of EA in combination with Doxil.

Enhanced Chemoprevention of Prostate Cancer by Combining Arctigenin with Green Tea and Quercetin in Prostate-Specific Phosphatase and Tensin Homolog Knockout Mice.

The low bioavailability of most phytochemicals limits their anticancer effects in humans. The present study was designed to test whether combining arctigenin (Arc), a lignan mainly from the seed of Arctium lappa, with green tea (GT) and quercetin (Q) enhances the chemopreventive effect on prostate cancer. We performed in vitro proliferation studies on different cell lines. We observed a strong synergistic anti-proliferative effect of GT+Q+Arc in exposing androgen-sensitive human prostate cancer LNCaP cells. The pre-malignant WPE1-NA22 cell line was more sensitive to this combination. No cytotoxicity was observed in normal prostate epithelial PrEC cells. For an in vivo study, 3-week-old, prostate-specific PTEN (phosphatase and tensin homolog) knockout mice were treated with GT+Q, Arc, GT+Q+Arc, or the control daily until 16 weeks of age. In vivo imaging using prostate-specific membrane antigen (PSMA) probes demonstrated that the prostate tumorigenesis was significantly inhibited by 40% (GT+Q), 60% (Arc at 30 mg/kg bw), and 90% (GT+Q+Arc) compared to the control. A pathological examination showed that all control mice developed invasive prostate adenocarcinoma. In contrast, the primary lesion in the GT+Q and Arc alone groups was high-grade prostatic intraepithelial neoplasia (PIN), with low-grade PIN in the GT+Q+Arc group. The combined effect of GT+Q+Arc was associated with an increased inhibition of the androgen receptor, the PI3K/Akt pathway, Ki67 expression, and angiogenesis. This study demonstrates that combining Arc with GT and Q was highly effective in prostate cancer chemoprevention. These results warrant clinical trials to confirm the efficacy of this combination in humans.