tbuckley/cabot-search huggingface dataset:
Abstract 5778: Determining the structure and function relationship of the oxysterol-binding protein (OSBP) to guide drug development
Authors: Ruth Fiona Bayimenye, Jorge L. Berrios-Rivera, Susan Nimmo, Christina R. Bourne, Anthony W. Burgett
Journal: Cancer Research (2024)

Abstract The human Oxysterol Binding Protein Structure and function relationship remains elusive, yet the anti-cancer and antiviral molecules library targeting OSBP and OSBP-Related proteins (ORPs) continues to grow. OSBP is a ubiquitously expressed protein in most eukaryotes, functioning as a master lipid sensor and cholesterol regulator in cells. OSBP and its closely related protein ORP4 are also reported to be essential in several human diseases, including viral infection and cancer cell proliferation. Our lab has shown that the natural product OSW-1 has potential anti-viral and anti-cancer activity through targeting OSBP and ORP4, as confirmed with protein-ligand interactions that showed binding with high affinity. Moreover, several anti-cancer molecules targeting the ORPs provoke different protein conformation changes and, therefore, lead to varying OSBP functions. However, the structure of full-length OSBP is still unknown, which leaves a gap in knowledge regarding the compounds’ mechanism of action or how OSBP could be established as a molecular anti-cancer target. Our goal is to determine the structure and function relationship of OSBP with emphasis on the effect of small molecule ligands on cellular OSBP levels and function. In pursuit of this research goal, we aim to determine the in vitro activity of OSW-1 analogs (OA) isolated in our lab, as well as determine their interaction with OSBP and ORP4 proteins in multiple cancer cell lines. We mainly seek to determine the structure and ligand interaction with the OSBP-ligand binding domain (LBD) and full-length OSBP to shed light on the conformation changes that occur upon ligand binding. Preliminary data indicate that the tested OA compounds are active in multiple cancer cell lines with reduced OSBP levels effect, suggesting a similar mechanism of action to OSW-1. A transient expression of full-length OSBP and LBD showed that the truncated OSBP (LBD) was mostly found in the pellet, which could imply low solubility, while the full-length OSBP showed sufficient solubility. Our efforts are currently focused on purifying full-length OSBP. We are also working towards purifying full-length OSBP with a cleavage site that allows cutting out the LBD, thus solving the insolubility issue. Once obtained, the full-length OSBP and the ligand binding domain will be used for both binding and structure determination studies. Citation Format: Ruth Fiona Bayimenye, Jorge L. Berrios-Rivera, Susan Nimmo, Christina R. Bourne, Anthony W. Burgett. Determining the structure and function relationship of the oxysterol-binding protein (OSBP) to guide drug development [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 5778.
Abstract 3132: A novel dual drug antibody-drug conjugate targeting hTrop2 has synergetic anti-tumor activity in solid tumor models
Authors: Jie Zhu, Xiaobei Zhao, Eileen Li, Hong Xu, Lei Nie, Gang Chen, Haibing Wang
Journal: Cancer Research (2024)

Abstract Antibody-drug conjugates (ADCs) are emerging therapeutic agents for targeted cancer treatment with remarkable clinical success. However, tumor heterogeneity and microenvironment complexity are still the major factors contributing to drug resistance, recurrence, and metastasis, which cannot be resolved with a mono therapy strategy. We’ve developed a novel dual drug ADC (BiADC), BR113, by conjugating an anti-hTrop2 antibody with a drug linker of a Topoisomerase I inhibitor payload, and another drug linker of an immune stimulator. Our studies show that the homogeneous ADC containing two distinct payloads is a new promising drug class, with two different anti-tumor MOAs, synergistic antigen-specific cell killing potency, desirable pharmacokinetic profiles, and minimal toxicity at therapeutic doses. In the cancer cells and human PBMC co-culture assay, BR113 exerts significantly more potent killing on cancer cells than two individual single-drug ADCs and the combination of two single-drug ADCs, which suggested a synergy on anti-tumor effects of this dual-drug ADC. In the xenograft mouse model studies, BR113 exhibits greater treatment effect and survival benefit than the combo of two single-drug ADCs at various doses. This robust superior anti-tumor activity is further confirmed in a hTrop2-MC38 syngeneic model with a prolonged anti-tumor protection against the tumor re-challenge. Finally, the novel BiADC, BR113, is well tolerated in hTop2 humanized mice after repeated administration. Our findings highlight the therapeutic potential of the BiADC format for treating refractory advanced solid tumors. The outstanding anti-tumor activity across various CDX tumor models and its favorable safety profile in mice support further evaluation of the innovative BiADC, BR113. Citation Format: Jie Zhu, Xiaobei Zhao, Eileen Li, Hong Xu, Lei Nie, Gang Chen, Haibing Wang. A novel dual drug antibody-drug conjugate targeting hTrop2 has synergetic anti-tumor activity in solid tumor 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 3132.
Abstract 586: Tumor cell-intrinsic PD-1 activation drives therapeutic resistance in colorectal cancer cells
Authors: Ho Kit Mok, Donald Yapp, Isabella Tai
Journal: Cancer Research (2024)

Abstract Background/Aim: Despite advancements in diagnosis and treatment, advanced CRC remains a formidable treatment challenge with limited therapeutic options because these tumors are resistant to chemo-, radio- and targeted-therapies. Emerging research shows that the presence of tumor cell-intrinsic PD-1 (ciPD-1) in various tumor types is involved in tumorigenicity and therapy-refractory disease. For example, ciPD-1 promotes tumor growth in melanoma and liver cancer, but in lung cancer, ciPD-1 exhibits tumor-suppressive behavior. These findings highlight the intriguing possibility that ciPD-1 may exert context specific functions within the tumor, beyond its well-known role in immune response suppression. Consequently, the present study addressed the pressing need to explore the effects of immune checkpoint inhibitors within broader tumor context and tumor microenvironment. We have established drug-resistant CRC cells and found that ciPD-1 was upregulated in these cells. This, together with an observation that ciPD-1-mediated survival signaling pathways was activated in CRC patient populations, prompted us to investigate the role of ciPD-1 in regulation of therapeutic resistance in CRC in the absence of immune cells. Methods: We evaluated the clinicopathological relevance of ciPD-1 and its correlation with disease progression in CRC samples from clinical cohorts. Monoclonal antibody inhibition and siRNA interference methods were used to characterize the functional roles of ciPD-1 in regulating therapeutic resistance in CRC. The gene expression profiles of PD-1-High and PD-1-Low patient groups retrieved from clinical cohorts were compared to identify ciPD-1-medatied survival pathways in CRC patients. Results: We found that ciPD-1 had a critical role in regulating CRC tumorigenicity and survival outcomes. Tumors with high expression levels of ciPD-1 also showed higher mutation rate and levels of microsatellite instability. Exposing CRC cells to chemotherapy, radiation, and nutrient deprivation increased ciPD-1 levels. In line with these observations, drug-resistant CRC cells also expressed higher levels of ciPD-1. The inhibition of ciPD-1 in CRC cells by monoclonal antibody or siRNA interference decreased cell proliferation and self-renewal rates, while enhancing treatment efficacy. Conclusion: Our studies reveal that CRC cells increase ciPD-1 expressions in response to drug treatment and targeting ciPD-1-mediated survival pathways can delay the onset of drug resistance and promote therapeutic sensitiveness in CRC cells. Citation Format: Ho Kit Mok, Donald Yapp, Isabella Tai. Tumor cell-intrinsic PD-1 activation drives therapeutic resistance in colorectal cancer cells [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 586.
Abstract 5858: Systematic identification of pathways associated with antibody drug conjugate sensitivity in breast cancer
Authors: Bogang Wu, Sheng Sun, Nayana Thimmiah, Aiko Nagayama, James T. Coates, Ting Liu, Win Thant, Elena Bitman, David Li, John Doench, Aditya Bardia, Leif W. Ellisen
Journal: Cancer Research (2024)

Abstract Antibody drug conjugates (ADCs) are revolutionizing precision therapeutics in oncology. Sacituzumab Govitecan (SG), combining a Topoisomerase I (TOP1) inhibitor payload (SN38) and the tumor-selective antigen TROP2-targeting antibody hRS7, has demonstrated efficacy in challenging cancers including triple negative breast cancer (TNBC). Despite its promising clinical efficacy, the intricacies of sensitivity and resistance mechanisms to SG remain elusive. To systematically interrogate ADC sensitivity mechanisms, we employed genome-wide CRISPR-Cas9 knockout screening to discover novel regulators influencing SG sensitivity in human TNBC cells. Interactome analysis of top SG sensitizing hits showed clustered pathways of interest, including DNA repair/replication, mTORC1/metabolism, ubiquitin/proteolysis and endosome trafficking/sorting. A top druggable hit sensitizing to SG was PARP1, encoding the poly (ADP-ribose) polymerase 1 that is a key enzyme required for single-strand break repair pathways and for DNA replication fork stability. Furthermore, the synergistic lethality between SG and PARP1 was confirmed in experiments combining SG with PARP inhibitor treatment of TNBC cell lines. To selectively identify SG/ADC-specific genes and pathways, we performed a secondary round of CRISPR knockout and activation screens using a custom library comprising top hits discovered in the primary screen, treating cells in parallel with either SG or cytotoxic payload SN38 alone. Pathway analysis of genes selectively modulating sensitivity to SG but not SN38 revealed novel mediators involved in TROP2 turnover and recycling. We then performed validation and mechanistic studies to elucidate how specific genetic permutations regulate antibody delivery and sensitivity to SG. In summary, employing a systematic CRISPR screening method, we uncovered numerous novel pathways associated with both resistance and sensitization, playing a role in ADC delivery and target protein turnover. Our current focus involves prioritizing druggable genes and pathways, laying the foundation for proof-of-concept studies that will combine ADCs with specific targeted therapeutics, aiming to enhance tumor-killing efficacy. Citation Format: Bogang Wu, Sheng Sun, Nayana Thimmiah, Aiko Nagayama, James T. Coates, Ting Liu, Win Thant, Elena Bitman, David Li, John Doench, Aditya Bardia, Leif W. Ellisen. Systematic identification of pathways associated with antibody drug conjugate sensitivity in breast cancer [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 5858.
Abstract 5851: Dysregulated RNA splicing promotes AML quiescence and chemoresistance
Authors: Eric Wang, Cuijuan Han, Alexander Calderon, Abimbo Lawal, Nidhi Hariramani, Edie Crosse, Robert Bradley
Journal: Cancer Research (2024)

Abstract Chemotherapy is the first-line treatment for patients with acute myeloid leukemia (AML). Although most achieve initial remission, an estimated 50% of patients will relapse with poor clinical outcome. The paucity of genetic lesions in AML patients that relapse from chemotherapy implicate non-genetic alterations that mediate chemoresistance. In this study, we conducted a longitudinal analysis of alternative splicing changes in a cohort of 19 AML patients at diagnosis and relapse post-chemotherapy treatment. We found that the long isoform of the transcription factor-encoding gene RUNX1 (also known as RUNX1C) is upregulated in AML relapse cohorts and conferred chemotherapy resistance. Mechanistically, we show that B cell translocation gene 2 (BTG2) is an RUNX1C isoform-specific transcriptional target that promote transition into a quiescent and treatment-resistant state. Direct targeting of RUNX1C mRNA augments chemotherapy response in AML patient-derived xenograft (PDX) models in vivo. These findings uncover an isoform-specific functionality that influences chemotherapy responsiveness and offers a therapeutic strategy to sensitize leukemic cells to conventional chemotherapy treatments. Citation Format: Eric Wang, Cuijuan Han, Alexander Calderon, Abimbo Lawal, Nidhi Hariramani, Edie Crosse, Robert Bradley. Dysregulated RNA splicing promotes AML quiescence and chemoresistance [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 5851.
Abstract 3284: Transcription factor YBX1 elevating the sorafenib IC50 in hepatocellular carcinoma cell lines
Authors: Dennis Kwabiah, Ana AyalaPazzi, Kyle Doxtater, Sophia Leslie, Manish K. Tripathi
Journal: Cancer Research (2024)

Abstract Hepatocellular carcinoma (HCC) is the most common form of liver cancer which accounts for more than 90% of occurrences of liver cancer cases. Surgical therapies such as liver transplantation and hepatectomy may help cure hepatocellular carcinoma diagnosed in its early stages. Advanced stages of the disease have a poor prognosis and a high refractoriness because of drug resistance. Sorafenib is a tyrosine kinase inhibitor that has been approved for the systemic treatment of patients with advanced HCC. However, the efficacy of this medication has shown a limited prolongation of the overall survival in patients with advanced HCC. The mechanism of resistance to sorafenib in advanced HCC is poorly understood. The TCGA analysis of the HCC patient cohort shows an elevated expression of YBX1 in tumors as compared to normal. The expression is also correlated with progression, metastasis, and poor survival of HCC patients. Transcription factor YBX1 is involved in the regulation of drug resistance in different cancers, especially breast and colorectal cancers. Our lab is interested in understanding if YBX1 is involved in sorafenib resistance in HCC. Different HCC cell lines procured from ATCC SK-Hep1, Huh-7luc, and C3A, were analyzed for their IC50 values for sorafenib using MTT assays, at different time points. SK-Hep1 showed 8.780µM and 8.174µM, HepG2luc 4.659µM and 3.596µM at 48 and 72 hrs respectively. Overexpression of YBX1 in the SK-Hep1 cell line increased the cell survival and IC50 value of sorafenib at 48 and 72 hrs at 13.19µM and 10.64µM respectively. This supports the hypothesis which demonstrates the role of YBX1 in mediating resistance to sorafenib in advanced HCC. YBX1 could be a major therapeutic target and by inhibiting its action could improve the sensitivity of advanced HCC to sorafenib. We have developed YBX1 overexpressing and knockdown (GFP expressing) cell lines, FACS sorted and Puromycin selected for further mechanistic studies. We are also further developing the sorafenib-resistant HCC cell lines to understand the mechanism underlying sorafenib resistance in HCC. Protein and RNA analyses revealed a relative increase in YBX1 overexpression in sorafenib-resistant cell lines as compared to its parental cell lines. Understanding the mechanism of YBX1-induced drug resistance to sorafenib and its associated signaling pathways could help improve the sensitivity of advanced hepatocellular carcinoma to treatment by sorafenib and thus improve the livelihood of its patients. Citation Format: Dennis Kwabiah, Ana AyalaPazzi, Kyle Doxtater, Sophia Leslie, Manish K. Tripathi. Transcription factor YBX1 elevating the sorafenib IC50 in hepatocellular carcinoma cell lines [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 3284.
Abstract 5603: Defining the functions of the BRCA2 BRC repeats in modulating RAD51 binding and activity
Authors: Julia R. Jensen, Ryan B. Jensen
Journal: Cancer Research (2024)

Abstract The BRCA2 (Breast Cancer Susceptibility 2) gene is critical for preserving genome integrity by regulating homology-directed repair (HDR) of DNA double-strand breaks (DSBs). Germline mutations in BRCA2 predispose individuals to a high risk for ovarian, breast, prostate, and pancreatic cancer. BRCA2 contains eight BRC repeats that mediate binding to RAD51. It remains unclear how exactly the different BRC repeats regulate RAD51 functions. In our study, we explore the importance of each BRC repeat, their interconnections, and their impact on RAD51 binding and filament stability. We engineered amino acid substitutions into the BRC FxTAS motif required for specific contacts within a hydrophobic binding pocket of RAD51 to disrupt BRC binding to RAD51. We further created mutations in RAD51 (F86E/A89E) that either prevent self-association but retain binding to the BRC repeats or a mutation (K133R) that results in a hyper-stable RAD51 nucleoprotein filament. Using both cell-based models and biochemical analyses, we have begun studies to parse out the specific functions of each BRC repeat. Our ultimate goal is to incorporate single amino acid changes into each BRC repeat within the context of the full-length BRCA2 protein to comprehensively characterize the contribution of each BRC repeat to HDR and response to chemotherapeutics such as PARP inhibitors. Citation Format: Julia R. Jensen, Ryan B. Jensen. Defining the functions of the BRCA2 BRC repeats in modulating RAD51 binding and activity [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 5603.
Abstract 3847: Dual targeting of EGFL6 and VEGF-A to overcome immune suppression in ovarian cancer
Authors: Sujanitha Umamaheswaran, Lingegowda S. Mangala, Robiya Joseph, Nicholas B. Jennings, Mark S. Kim, Yunfei Wen, Emine Bayraktar, Ningyan Zhang, Zhiqiang An, Anil K. Sood
Journal: Cancer Research (2024)

Abstract Background: Ovarian carcinomas are known to have a high degree of immune suppression, which may be related, in part, to high levels of vascular endothelial growth factor-A (VEGF-A). Bevacizumab (anti-VEGF antibody) has been shown to increase infiltration of T-cells in the tumor microenvironment (TME). We have also identified EGFL6 as an important angiogenic protein. Here, we examined the biological effects of blocking EGFL6 and VEGF-A in ovarian cancer models. Methods: We studied the in vitro (endothelial tube formation and migration assays) and in vivo (ID8KO-Trp53;Brca2 and SKOV3-ip1 models) biological effects of EGFL6 and VEGF-A blockade. Tumor-infiltrating immune cells were studied by flow cytometry and immunohistochemistry staining. Results: Blocking EGFL6 and VEGF-A simultaneously with monoclonal antibodies in RF24 endothelial cells decreased tube formation and migration significantly, in comparison to VEGF-A blockade alone (p&amp;lt;0.001). EGFL6 monotherapy in ID8KO-Trp53;Brca2 tumor bearing syngeneic mice decreased tumor burden (~2.5 fold, p&amp;lt;0.0001) and increased the infiltration of IFNγ+ (~2.75 fold, p&amp;lt;0.0001) and GzmB+ (~1.75 fold, p&amp;lt;0.01) CD8+ T-cells and IFNγ+ (~2 fold, p&amp;lt;0.0001) and GzmB+ (~2 fold, p&amp;lt;0.01) CD4+ T-cells while decreasing PD-L1+ cells (~1.8 fold, p=0.01). Dual blockade of EGFL6 and VEGF-A in SKOV3-ip1 tumor bearing nude mice significantly decreased tumor burden (~3.72 fold, p&amp;lt;0.01) and angiogenesis (~2.36 fold, p&amp;lt;0.05) compared to controls and single-agent blockade. Similar blockade in ID8KO-Trp53;Brca2 tumor bearing mice significantly decreased tumor burden (~4.2 fold, p=0.0004), improved CD8+ (~3.32 fold, p=0.0004) and CD4+ (~2.81 fold, p&amp;lt;0.0001) T-cell infiltration, NK cell infiltration (~2.3 fold, p=0.0005) and decreased myeloid-derived suppressor cells (MDSCs) (~1.92 fold, p=0.0278) compared to EGFL6 and VEGF-A blockade alone. Conclusions: Our results demonstrate that simultaneously targeting the angiogenesis drivers EGFL6 and VEGF-A in ovarian cancer significantly decreased tumor burden in vivo and increased the infiltration of T lymphocytes compared to single-agent blockade. AACR Category: Tumor Microenvironment and Immune Oncology Key words: ovarian cancer, immune suppression, angiogenesis, VEGF-A, EGFL6 Citation Format: Sujanitha Umamaheswaran, Lingegowda S. Mangala, Robiya Joseph, Nicholas B. Jennings, Mark S. Kim, Yunfei Wen, Emine Bayraktar, Ningyan Zhang, Zhiqiang An, Anil K. Sood. Dual targeting of EGFL6 and VEGF-A to overcome immune suppression in ovarian cancer [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 3847.