Proteosome Inhibitor Research Articles

CTNI-44. NCT03643549 PHASE IB/II TRIAL: EFFICACY, SAFETY, AND BIOLOGICAL MECHANISMS OF OBJECTIVE RESPONSES IN RECURRENT GBM PATIENTS WITH UNMETHYLATED MGMT PROMOTER TREATED WITH SEQUENTIAL BORTEZOMIB AND TEMOZOLOMIDE

Abstract BACKGROUND Glioblastoma (GBM) is amongst the deadliest malignancies in adults, but especially for patients with unmethylated MGMT promoter (uMGMT) who gain limited benefit from the standard treatment. We previously demonstrated that proteosome inhibitor bortezomib (BTZ), inhibited NFkB activation,depleted MGMT protein and sensitized uMGMT GBM cells to Temozolomide (TMZ). Thus, a phase I/II trial testing sequential combination BTZ+TMZ was launched to investigate safety and clinical benefit. METHODS Recurrent GBM patients with uMGMT promoter, progressing ≥12 weeks after radiotherapy, KPS≥70 and radiologically measurable lesions were enrolled. The trial was powered for n=63 patients compared with n=102 historical controls. Patients received BTZ 1.3mg/m² IV on days 1, 4, and 7 of each 4-week cycle, starting on day 3 with oral 200mg/m² TMZ for 5 days/week. Whole exome sequencing (WES) of tumor DNA was conducted to identify genetic changes and LC-MS/MS used to asses proteomic changes in plasma collected during treatment. RESULTS As of January 2024, 54 patients (median 55y (25-70); 38 males, 16 females) were treated. The median KPS 90 (range 70-100) and NANO score was 1 (range 0-7). QoL was preserved, with mild /moderate adverse events. Adjusted analyses showed overall survival (OS) of 16.2 months compared to 8.4 months for uMGMT control patients, HR0.48, 95%CI[1.057-2.74],P=0.028. Objective radiological responses stable disease or better were observed in 22% (12/54) patients. Survival from recruitment was 10.5 months for responders vs. 4.8 months for rest of cohort, P=0.054 HR2.55, 95%CI[0.984-5.94]. Preliminary data indicate 78% (7/9) of responders harboured amplified EGFR vs. 38% in rest-of-the patients. The responders differentially expressed proteins critical for cellular processes, including ADAMTSL4, NCAM1, AZGP1, MMP2, CD163, and IL6ST. CONCLUSION Sequential BTZ+TMZ therapy is safe, effective and showed clinical benefit. EGFR amplification may be a predictive biomarker for response through NFκB activation, that is targeted by BTZ thereby depleting MGMT protein and enhancing treatment efficacy. Sequential BTZ+TMZ treamtment may represent additional treatment option at recurrence.

Pharmacological Interactions of Jadomycin B with Topoisomerase Poisons in MDA-MB-231 Human Breast Cancer Cells.

Jadomycin B, a natural product isolated from Streptomyces venezuelae, exerts an anti-cancer effect on human triple negative breast cancer cells in vitro and has anti-tumoral effects in vivo in animal models of breast cancer. One proposed mechanism for this anti-cancer effect is through interaction with topoisomerase 2 (TOP2). Based on the previously described interactions between jadomycin B and TOP2 we hypothesized that jadomycin B will act additively with TOP2 poisons and produce a similar functional outcome in eliciting cell cycle arrest. Combined treatments of jadomycin B and the TOP2 poisons doxorubicin or mitoxantrone produced moderately synergistic to additive cytotoxicity (combination index values ranging from 0.72-0.94) in MDA-MB-231 cells. In comparison, combined mitoxantrone and doxorubicin produced additive cytotoxicity (combination index values 0.96-1.11). Jadomycin B combined with the proteosome inhibitor MG132 had additive cytotoxicity (combination index values 0.76-1.18). In contrast, mitoxantrone or doxorubicin cytotoxicity was antagonized by MG132 (combination index values 1.21-2.31). Jadomycin B treatment arrested cells in S-phase (P = 0.0024) as opposed to mitoxantrone which caused G2/M-phase arrest (P < 0.0001). In conclusion, jadomycin B interacts differently than known TOP2 poisons in combination, supporting a novel pharmacological mechanism(s) of action for jadomycin B cytotoxicity.

Rac1 GTPase Regulates the βTrCP-Mediated Proteolysis of YAP Independently of the LATS1/2 Kinases.

Background: Oncogenic mutations in the KRAS gene are detected in >90% of pancreatic cancers (PC). In genetically engineered mouse models of PC, oncogenic KRAS drives the formation of precursor lesions and their progression to invasive PC. The Yes-associated Protein (YAP) is a transcriptional coactivator required for transformation by the RAS oncogenes and the development of PC. In Ras-driven tumors, YAP can also substitute for oncogenic KRAS to drive tumor survival after the repression of the oncogene. Ras oncoproteins exert their transforming properties through their downstream effectors, including the PI3K kinase, Rac1 GTPase, and MAPK pathways. Methods: To identify Ras effectors that regulate YAP, YAP levels were measured in PC cells exposed to inhibitors of oncogenic K-Ras and its effectors. Results: In PC cells, the inhibition of Rac1 leads to a time-dependent decline in YAP protein, which could be blocked by proteosome inhibitor MG132. This YAP degradation after Rac1 inhibition was observed in a range of cell lines using different Rac1 inhibitors, Rac1 siRNA, or expression of dominant negative Rac1T17N mutant. Several E3 ubiquitin ligases, including SCFβTrCP, regulate YAP protein stability. To be recognized by this ligase, the βTrCP degron of YAP (amino acid 383-388) requires its phosphorylation by casein kinase 1 at Ser384 and Ser387, but these events must first be primed by the phosphorylation of Ser381 by LATS1/2. Using Flag-tagged mutants of YAP, we show that YAP degradation after Rac1 inhibition requires the integrity of this degron and is blocked by the silencing of βTrCP1/2 and by the inhibition of casein kinase 1. Unexpectedly, YAP degradation after Rac1 inhibition was still observed after the silencing of LATS1/2 or in cells carrying a LATS1/2 double knockout. Conclusions: These results reveal Rac1 as an oncogenic KRAS effector that contributes to YAP stabilization in PC cells. They also show that this regulation of YAP by Rac1 requires the SCFβTrCP ligase but occurs independently of the LATS1/2 kinases.

Efficacy assessment of a novel pan-RAS inhibitor in KRAS-mutant and wild type colorectal 3D bioprinted organoid tumor tissue.

91 Background: Colorectal cancer (CRC) is the third leading type of cancer worldwide, with ~150,000 new cases in the US annually and a grim 14% 5-year survival for patients diagnosed at a late stage. A lack of treatment options leads to persistently poor prognosis for patients with advanced stage disease. KRAS mutations are well known drivers of CRC and other GI cancers. Multiple KRAS mutations occur in CRC, including G12D (34%), G12V (21%), G13D (20%), G12C (8%), and others (18%). Existing KRAS-targeted therapies have limited use in CRC, underscoring the need for pan-RAS inhibitors in treating CRC and other RAS driven cancers. Objective: Assess activity of ADT-007, our pan-RAS inhibitor, on wild-type (WT) and KRAS-mutant 3D bioprinted organoid tumor (BOT) tissue using our high-throughput ex vivo platform. Methods: Using previously established bioprinting protocols, WT and mutant BOTs were printed with HT29 and HCT116 cells, respectively. HT29 is an established human WT CRC cell line with known sensitivity to proteosome and survivin inhibitors. HCT116 is a KRASG13D mutant human CRC cell line. 3 sets of BOTs were generated and acclimated for 24h. One set was treated for 72h with proteosome inhibitor Bortezomib, another with survivin inhibitor YM155, and the third with our novel pan-RAS inhibitor ADT-007. Dose response curves were generated from both conventional ATP luminescence readouts and high-content imaging. Results: BOT tissue microarchitecture was validated and &gt;200 µm diffusion in BOTs was confirmed using high-content imaging. Differential response was quantified using Cell TiterGlo endpoint assay as well as advanced image processing of high-content live/dead nuclear stained images captured at multiple z-plains. ADT-007 IC50 was found to be substantially lower for mutant HCT116 compared to that for WT HT29 cell line BOTs, which was consistent with separately conducted in vitro and in vivo studies. Conclusions: A pan-RAS inhibitor, such as ADT-007 with high selectivity for cancer cells with activated RAS that is not limited to a specific KRAS mutant allele or RAS isozyme, could have broader use for CRC and other RAS-driven cancers. Further, due to their potential to replicate biophysical characteristics of a tumor and its microenvironment, BOT based precision and personalized medicine platforms can provide more accurate drug efficacy readout compared to in vitro cancer models.

TRLS-13. MULTI-OMICS AND FUNCTIONAL PRECISION MEDICINE FOR NEWLY DIAGNOSED AND RECURRENT PEDIATRIC CENTRAL NERVOUS SYSTEM TUMORS

Abstract BACKGROUND Comprehensive molecular characterization of pediatric brain tumors has led to a more refined diagnosis. However, the feasibility of performing multi-omic and functional precision medicine approaches using ex-vivo drug screening in the clinical setting is unknown. METHODS Patients with newly diagnosed or recurrent central nervous system tumors were enrolled in a feasibility study of multi-omic analysis including whole genome trio germline sequencing, tumor whole exome/RNA sequencing, RNA-based DiSCoVER analysis, methylation profiling, immunogenic potential analysis, and ex-vivo drug screening utilizing a customized panel of 175 FDA approved/investigational drugs. Findings were presented at a multidisciplinary molecular neuro-oncology tumor board. RESULTS Eighteen patients (9 female; average age 9.4 years; 12 newly diagnosed, 6 with recurrent disease; 5 high grade gliomas, 4 ependymomas, 4 embryonal tumors, 3 low grade gliomas, 2 others) were enrolled between 2020-2022. Whole genome germline testing (N=18) was normal in half of patients (pathogenic germline mutations in 3 patients, variants of unknown significance in 6 patients). Ex-vivo drug screening results (N=14) varied among patients, however sub-micromolar efficacy was commonly observed for proteosome inhibitors, HDAC inhibitors, and topoisomerase II inhibitors. Average time from surgery to receipt of finalized results varied across platforms (drug screening 5.7 days, whole exome/RNA sequencing 14.8 days, whole genome germline 10.6 days, methylation 21 days). Fifteen patients had a modification in diagnosis and 4 patients had a change in tumor classification. Multi-omic and functional precision medicine results alone or in combination led to changes in management in 50% of patients (Tumor Molecular Sequencing 6/18, Ex-Vivo Drug Screening 4/14, RNA DiSCoVER Analysis 2/15, Methylation 1/14). CONCLUSION Our studies demonstrate the feasibility of timely ex-vivo drug screening and multi-omic analysis and show that these data may lead to changes in patient diagnosis/management. These findings are the basis of an ongoing trial for recurrent medulloblastoma (NCT05057702).

Long-term outcomes after cardiac transplantation in AL amyloidosis.

7572 Background: Systemic AL amyloidosis can lead to progressive multi-organ dysfunction including advanced heart failure which may require orthotopic heart transplantation (OHT). Hematologic outcomes of AL amyloidosis post-OHT are not well described. Methods: We report outcomes for patients with AL amyloidosis with cardiac involvement post-OHT from Nov 2008 - Jun 2023 at Vanderbilt University Medical Center. Hematologic response was graded per the ISA guidelines. Results: Fourteen pts underwent OHT of whom 13 had lambda light chain disease. Three (21%) pts had isolated AL amyloidosis (AL) without myeloma (MM), while 11 (79%) also had MM: 6 with bone marrow plasma cells (BMPCs) 10-19% (AL-PCMM-10) and 5 with BMPC ≥20% (AL-PCMM-20). One each with AL-PCMM-10 and AL-PCMM-20 had lytic lesions (AL-CRAB). Median age at OHT was 55.5 yrs (range 37-74). Median time from diagnosis to OHT was 18 mo (range 3-62). Five (35%) pts had biopsy-proven extracardiac amyloid involvement. Median difference in serum free light chains at first evaluation was 70 mg/dL (range 9-289). Three pts were Mayo 2012 stage II, 4 stage III, and 7 stage IV. Four pts had t(11;14) and 1 had 1q gain. Ten (71%) pts received triplet therapy (VCd or VRd) and 3 (21%) received quadruplet therapy (Dara-VCd or Isa-VCd) pre-OHT. Six (43%) pts had autologous stem cell transplantation (ASCT); 1 pre-OHT and 5 post-OHT. Of ASCT pts, 1 pt achieved CHR, 1 VGPR, 2 PR, and 1 had PD pre-ASCT. Pre-OHT, 4 pts achieved CHR, 6 VGPR, 3 PR, and 1 had PD. Eleven pts (79%) received maintenance therapy post-OHT (5 proteosome inhibitors, 6 anti-CD38). At last follow-up, 8 pts were in CHR, 3 in VGPR, 1 in PR, and 2 had PD. Four (29%) pts died post-OHT: 2 from AL recurrence (1 each with AL and AL-PCMM-10), 1 from cardiac allograft vasculopathy (AL-CRAB), and 1 from renal failure (AL-CRAB). Three (21%) pts had hematologic relapse 5, 21 and 48 mo post-OHT, and of those, 2 had recurrent cardiac amyloid in graft 37 and 71 mo post-OHT. Of those with hematologic relapse, 2 had AL-PCMM-10 and 1 had AL. One pt had post-transplant lymphoproliferative disorder 126 mo post-OHT, requiring treatment. Median follow-up and survival of the cohort post-OHT was 2.25 yrs (range 0.5-13.8). Conclusions: In this single-center analysis of pts undergoing OHT for cardiac AL amyloidosis, we demonstrate feasibility of excellent long-term outcomes, in predominantly high-risk AL pts where majority harbored high-risk disease with MM overlap, either by AL-CRAB or AL-BMPC. Induction alone led to ≥VGPR response in 10 (71%) pts pre-OHT and further therapy deepened this to 11 (79%) pts. Both AL-CRAB pts died during follow-up, highlighting the overall poor prognosis in this specific subgroup. In our cohort, non-relapse related mortality was seen in only 2 (14%) pts, demonstrating acceptable post-OHT risk and overall ability to achieve far improved outcomes in the high-risk cardiac AL amyloidosis patient population that otherwise suffers from rapid and universal mortality.

Efficacy of carfilzomib-based regimens as induction/consolidation therapy in newly diagnosed multiple myeloma: A meta-analysis.

e19535 Background: Carfilzomib (K) is a 2nd generation selective and irreversible proteosome inhibitor. It has shown encouraging results in newly diagnosed multiple myeloma (NDMM) patients. However, no direct comparisons were made among different regimens. This analysis aims to compare efficacy with different K-based regimens in NDMM. Methods: A literature search was done on PubMed and Embase with keywords for “Carfilzomib” and “multiple myeloma” till 1/1/2024. 25 articles (N = 3221) were included after screening 2800 articles. Data was collected for overall response rate (ORR), complete response (CR), minimal residual disease negativity (MRD-), 2-year progression free survival (PFS), and 2-year overall survival (OS). Survival data was extracted from visualization of Kaplan-Meier curve if not provided in text. R software was used for the meta-analysis. Results: In one trial (N = 72), ORR and CR were 90% and 7%, respectively in patients with K and dexamethasone (d). In one trial (N = 111), ORR, CR, PFS, and OS were 93%, 18%, 74%, and 96%, respectively with Kd and thalidomide (T). In six trials (N = 844), ORR, CR, MRD-, PFS, and OS were 92%, 43%, 38%, 78%, and 88%, respectively with Kd and lenalidomide (R). In one trial (N = 22), ORR, CR, and MRD-, were 100%, 64%, and 23%, respectively with Kd and Bendamustine (B). In three trials (N = 576), ORR, CR, MRD-, PFS, and OS were 82%, 23%, 16%, 48%, and 82%, respectively with Kd, and melphalan (M). In three trials (N = 189), ORR, CR, MRD-, PFS, and OS were 89%, 24%, 30%, 71%, and 89%, respectively with Kd and cyclophosphamide (Cy). In two trials (N = 63), ORR, CR, MRD-, PFS, and OS were 97%, 86%, 55%, 95%, and 100%, respectively with KRd and daratumumab (D). In one trial (N = 64), ORR, CR, PFS, and OS were 91%, 8%, 77%, and 95%, respectively with KCyTd. In one trial (N = 46), ORR, CR, MRD-, PFS, and OS were 96%, 70%, 65%, 80%, and 89%, respectively with KRd and elotuzumab (E). In one trial (N = 125), ORR, CR, MRD-, PFS, and OS were 94%, 70%, 79%, 70%, and 78%, respectively with KRd and isatuximab (I). In one trial (N = 526), ORR, CR, MRD-, and PFS were 90%, 18%, 17%, and 78%, respectively with KCyRd. In three trials (N = 280), ORR, CR, MRD-, PFS, and OS were 97%, 66%, 60%, 87%, and 94%, respectively with KRd and stem cell transplant (SCT). In two trials (N = 180), ORR, CR, MRD-, PFS, and OS were 91%, 55%, 43%, 70%, and 85%, respectively with KCyd-SCT. In one trial (N = 123), ORR, CR, MRD-, PFS, and OS were 98%, 86%, 80%, 87%, and 94%, respectively with KRDd-SCT. Conclusions: Among K based regimens, the highest response and 2-year-survival rates were achieved with KRDd, IKRd and were comparable to regimens with SCT. Highest MRD negativity was achieved with KRDd-SCT and IKRd. Hence, four drug regimens can be considered in NDMM to achieve high response and survival rates instead of SCT especially in patients who cannot tolerate or chose not to undergo SCT. Long-term results are needed to confirm these results.

Exploring side effects of corticosteroids in myasthenia gravis: Unveiling alternatives for safer treatment

Myasthenia Gravis (MG) is a chronic organ-specific autoimmune disease that weakens voluntary muscles by affecting neuromuscular junctions. The formation of antibodies against acetylcholine receptors is the most prevalent cause. The incidence and prevalence rates of (MG) are increasing exponentially (1). In addition to symptomatic medication, corticosteroids continue to be the first-line treatment for MG due to their affordability, ease of access, and efficacy (2). Although corticosteroids are frequently prescribed, they are not without drawbacks. Long-term corticosteroid use can result in various side effects, including osteoporosis, weight gain, acne, elevated blood pressure, mood fluctuations, and a cushingoid appearance. It has also been linked to rare complications such as gastric and esophageal irritation, compressive fractures, and aseptic femoral head fracture (3). Given the hazards associated with long-term corticosteroid use in treating MG, researchers and healthcare professionals should investigate alternative MG treatments. By doing so, new and safer treatment options can be identified, which could contribute to improved treatment and substantially enhance the quality of life for MG-affected populations. Numerous nonsteroidal medications, including mycophenolate mofetil, methotrexate, and azathioprine, have demonstrated success in clinical trials for kidney transplantation, rheumatoid arthritis, and myasthenia gravis, respectively. To confirm the efficacy of these pharmaceuticals in the treatment of MG, urgent research and trials based on in vitro and animal models are required. Based on well-designed clinical trials, these also require human testing (4). The tapering of prednisone is an alternative option. Prednisone tapering is still a problem in the therapeutic management of patients with generalized MG because, although it is a useful treatment, it has a number of adverse effects that make it necessary to find the lowest possible effective dose as quickly as feasible. Rituximab and azathioprine enable quick tapering. It is necessary to evaluate and contrast the corticosteroid-sparing effect of novel treatments with that of azathioprine and rituximab. Given their impact on MG status, it's possible that these novel therapies will make it possible to drastically cut back on corticosteroids or possibly stop taking them entirely(5) The abnormal immune responses in MG can be managed and resolved with the new drugs that specifically target them. These agents include chimeric antigen receptor T [CART-T] cell therapy, autologous stem cell transplantation, B cell depleting agents (anti-CD 19 and 20, and B cell activating factor [BAFF] inhibitors), proteosome inhibitors, terminal complement C5 inhibitors, Fc receptor inhibitors, T cells, and cytokine-based therapies (subcutaneous immunoglobulin [SCIG]). ---Continue

Adipocytes and metabolism: Contributions to multiple myeloma

Obesity contributes to many cancers, including breast cancer and multiple myeloma, two cancers that often colonize the bone marrow (BM). Obesity often causes metabolic disease, but at the cellular level, there is uncertainty regarding how these shifts affect cellular phenotypes. Evidence is building that different types of fuel affect tumor cell metabolism, mitochondrial function, and signaling pathways differently, but tumor cells are also flexible and adapt to less-than ideal metabolic conditions, suggesting that single-pronged attacks on tumor metabolism may not be efficacious enough to be effective clinically. In this review, we describe the newest research at the pre-clinical level on how tumor metabolic pathways and energy sources affect cancer cells, with a special focus on multiple myeloma (MM). We also describe the known forward-feedback loops between bone marrow adipocytes (BMAds) and local tumor cells that support tumor growth. We describe how metabolic targets and transcription factors related to fatty acid (FA) oxidation, FA biosynthesis, glycolysis, oxidative phosphorylation (OXPHOS), and other pathways hold great promise as new vulnerabilities in myeloma cells. Specifically, we describe the importance of the acetyl-CoA synthetase (ACSS) and the acyl-CoA synthetase long chain (ACSL) families, which are both involved in FA metabolism. We also describe new data on the importance of lactate metabolism and lactate transporters in supporting the growth of tumor cells in a hypoxic BM microenvironment. We highlight new data showing the dependency of myeloma cells on the mitochondrial pyruvate carrier (MPC), which transports pyruvate to the mitochondria to fuel the tricarboxylic acid (TCA) cycle and electron transport chain (ETC), boosting OXPHOS. Inhibiting the MPC affects myeloma cell mitochondrial metabolism and growth, and synergizes with proteosome inhibitors in killing myeloma cells. We also describe how metabolic signaling pathways intersect established survival and proliferation pathways; for example, the fatty acid binding proteins (FABPs) affect MYC signaling and support growth, survival, and metabolism of myeloma cells. Our goal is to review the current the field so that novel, metabolic-focused therapeutic interventions and treatments can be imagined, developed and tested to decrease the burden of MM and related cancers.

1q amplification and PHF19 expressing high-risk cells are associated with relapsed/refractory multiple myeloma

Multiple Myeloma is an incurable plasma cell malignancy with a poor survival rate that is usually treated with immunomodulatory drugs (iMiDs) and proteosome inhibitors (PIs). The malignant plasma cells quickly become resistant to these agents causing relapse and uncontrolled growth of resistant clones. From whole genome sequencing (WGS) and RNA sequencing (RNA-seq) studies, different high-risk translocation, copy number, mutational, and transcriptional markers can be identified. One of these markers, PHF19, epigenetically regulates cell cycle and other processes and is already studied using RNA-seq. In this study, we generate a large (325,025 cells and 49 patients) single cell multi-omic dataset and jointly quantify ATAC- and RNA-seq for each cell and matched genomic profiles for each patient. We identify an association between one plasma cell subtype with myeloma progression that we call relapsed/refractory plasma cells (RRPCs). These cells are associated with chromosome 1q alterations, TP53 mutations, and higher expression of PHF19. We also identify downstream regulation of cell cycle inhibitors in these cells, possible regulation by the transcription factor (TF) PBX1 on chromosome 1q, and determine that PHF19 may be acting primarily through this subset of cells.

Targeted therapy for multiple myeloma: an overview on CD138-based strategies.

Multiple myeloma (MM) is an incurable hematological disease characterized by the uncontrolled growth of plasma cells primarily in the bone marrow. Although its treatment consists of the administration of combined therapy regimens mainly based on immunomodulators and proteosome inhibitors, MM remains incurable, and most patients suffer from relapsed/refractory disease with poor prognosis and survival. The robust results achieved by immunotherapy targeting MM-associated antigens CD38 and CD319 (also known as SLAMF7) have drawn attention to the development of new immune-based strategies and different innovative compounds in the treatment of MM, including new monoclonal antibodies, antibody-drug conjugates, recombinant proteins, synthetic peptides, and adaptive cellular therapies. In this context, Syndecan1 (CD138 or SDC1), a transmembrane heparan sulfate proteoglycan that is upregulated in malignant plasma cells, has gained increasing attention in the panorama of MM target antigens, since its key role in MM tumorigenesis, progression and aggressiveness has been largely reported. Here, our aim is to provide an overview of the most important aspects of MM disease and to investigate the molecular functions of CD138 in physiologic and malignant cell states. In addition, we will shed light on the CD138-based therapeutic approaches currently being tested in preclinical and/or clinical phases in MM and discuss their properties, mechanisms of action and clinical applications.

Abstract CT120: Phase 1 trial of bortezomib and clofarabine combination in adults with refractory solid tumors

Abstract Background/Rationale: The combination of the proteosome inhibitor bortezomib (B) and purine analog clofarabine (C) induced synergy in the NCI-ALMANAC screen of FDA-approved cancer drug combinations; preclinical xenograft studies confirmed this activity and suggested a combination mechanism of action involving greater-than-additive effects on markers of DNA damage response (DDR) and pyroptotic cell death. We conducted a phase 1 clinical trial (NCT02211755) to assess the safety of the B and C combination in patients (pts) with solid tumors and myelodysplastic syndrome (MDS), and to determine the effect of the combination on biomarkers of cell death and DDR. Due to limited MDS pt accrual, this cohort was terminated early, and MDS pt data are not included here.Objectives: The primary objective was to assess safety and maximum tolerated dose (MTD) of B and C in pts with solid tumors and MDS. Secondary objectives were to assess pharmacodynamic (PD) effects using validated assays for cell death and DDR in tumor biopsy tissue and circulating tumor cells (CTCs).Design: The dose escalation followed a 3+3 design, enrolling at least 1 pt from each group (solid tumor and MDS) per dose level until hematologic dose-limiting toxicity (DLT) was observed. Adverse events (AEs) were graded using CTCAE v4.0. Ten planned dose levels (DL) included C ranging from 1 to 10 mg/m2 on D2-5 of cycle 1 and D1-5 from cycle 2 on and B from 0.8 to 1.5 mg/m2 on D1 and D4 of 21-day cycles. Response was assessed by RECIST 1.1 every 2 cycles. Biopsies were performed on the expansion cohort pre-dose, 2-4 hours after C on C1D1, and C2D4; CTCs were collected pre-dose, C1D2, day 1 of subsequent cycles, and at progression.Results: We enrolled 25 pts with advanced solid tumors (15 male, 10 female). Median age was 62 years (range 30-81). DLT occurred in 4 pts (at DL3 [1 pt], DL5 [2], and DL4 [1]) and included Grade 4 neutropenia (3), Grade 3-4 thrombocytopenia (3), and Grade 3 anemia (1). There were no Grade 5 AEs. DL4 (B 1.3 mg/m2 D1 and 4, C 1.5 mg/m2 D1-5, 21-day cycles) was the MTD. Twenty-one pts were evaluable for response; the best response was stable disease (SD) for 10 pts (47.6%). Median duration of response for pts achieving SD was 3.5 months (range 2-7). Of note, 3 out of the 10 colorectal cancer (CRC) pts had SD &amp;gt; 4 months. Four pts with CRC have been enrolled in an expansion cohort for biomarker evaluation; induction of pyroptosis has been measured in a limited number of paired biopsies collected to date. Conclusions: Despite preclinical evidence of synergy, the human equivalent of the efficacious preclinical combination dose could not be achieved clinically, which may account for the lack of antitumor response. Prolonged SD was observed in 3 pts with CRC. PD analyses, including of CTCs and additional cell death biomarkers, are ongoing. Funded by NCI Contract No. HHSN261201500003I. Citation Format: Andre L. De Souza, Naoko Takebe, Alice P. Chen, James H. Doroshow, Ralph E. Parchment, Apurva K. Srivastava, Lawrence Rubistein, Deborah Wilsker, Brandon L. Miller, Murielle Hogu, Geraldine O`Sullivan Coney, Shivaani Kummar, Jeevan Govindharajulu, Robert Meehan, William G. Herrick, Angie Dull, Donna Ketchum, Shaowei Li, Jiuping Ji, Richard Piekarz. Phase 1 trial of bortezomib and clofarabine combination in adults with refractory solid tumors [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 CT120.

Dapagliflozin ameliorates hepatic steatosis via suppressing LXRα-mediated synthesis of lipids and bile acids

Nonalcoholic fatty liver disease (NAFLD) prevalence is rising globally with no pharmacotherapies approved. Hepatic steatosis is closely associated with progression and prognosis of NAFLD. Dapagliflozin, kind of sodium-glucose cotransporter 2 (SGLT2) inhibitor, was found to improve NAFLD in clinical trials, while the underlying mechanism remains poorly elucidated. Here, we reported that dapagliflozin effectively mitigated liver injury and relieved lipid metabolism disorders in vivo. Further investigation showed that dapagliflozin markedly suppressed Liver X Receptor α (LXRα)-mediated synthesis of de novo lipids and bile acids (BAs). In AML12 cells, our results proved dapagliflozin decreased lipid contents via inhibiting the expression of LXRα and downstream liposynthesis genes. Proteosome inhibitor MG132 eliminated the effect of dapagliflozin on LXRα-mediated signaling pathway, which suggested that dapagliflozin downregulated LXRα expression through increasing LXRα degradation. Knockdown of LXRα with siRNA abolished the reduction of lipogenesis from dapagliflozin treatment, indicating that LXRα might be the pivotal target for dapagliflozin to exhibit the aforementioned benefits. Furthermore, the data showed that dapagliflozin reversed gut dysbiosis induced by BAs disruption and altered gut microbiota profile to reduce intestinal lipids absorption. Together, our study deciphered a novel mechanism by which dapagliflozin relieved hepatic steatosis and highlighted the potential benefit of dapagliflozin in treating NAFLD.

Abstract 5846: Inhibiting elements of the proteasome recovery pathway sensitizes glioblastoma to proteasome inhibitors

Abstract Bacground: Glioblastoma (GBM) is the most common primary brain tumor, accounting for 15% of all central nervous system related tumors. Despite the aggressive standard of care treatment including chemotherapy, radiotherapy, and maximally safe surgical resection, patient outcomes are abysmal: with 95% of patients relapsing and a median overall survival of 15 months. Thus, this necessitates the rapid query for personalized therapeutics and agents that can potentiate the clinical effects of currently approved treatments. One such pathway that demonstrates aberrant functioning in cancer and is a targetable mechanism is the ubiquitin-proteosome pathway (UPP). Studies have shown that UPP related proteolysis remains constitutively active in cancer cells leading to the rapid degradation of proteins that regulate tumor suppressor genes and oncogenes. Despite robust preclinical evaluations for the usage of proteosome inhibitors against GBM, most tested proteosome inhibitors failed in phase II and III trials, indicating resistance. Methods: We conducted an unbiased genome wide CRISPR-Cas9 screen in human HAP1 cells treated with the proteosome inhibitor, Bortezomib (BTZ), to identify genes that may lead to a BTZ-resistant phenotype. We identified several genes that when perturbed, sensitized cells to BTZ including N-glycanase-1 (NGLY-1), Nuclear factor Erythroid 2-Like-1 (NFE2L1), and DNA damage inducible 1 homolog 2 (DDI2). Herein we sought to evaluate the effects of perturbing components of the proteosome rescue pathway in our Singh lab patient derived GBM cell lines by utilizing CRISPR/Cas9 knockout technology in vitro and in vivo. Results: The generation of NGLY-1, DDI2, and NFE2L1 KO cell lines demonstrated functional sensitivity to the proteosome inhibitor Marizomib (MZB) as observed through a significant reduction of the IC50 in the KO cell lines compared to a control. Functional evaluation also revealed a reduction in proliferation capacity as well as sphere formation in these genetically modified GBM lines. Ongoing in vivo work will aim to evaluate the mitigation of this resistant pathway in our NSG mouse models orthotopically transplanted with these patient derived KO cell lines. In an ongoing collaborative effort, we are working to identify and functionally assess a novel small molecule NGLY-1 inhibitor to evaluate preclinical sensitivity to MZB in our in vitro and in vivo models. Citation Format: Alisha Anand, Muhammad Vaseem Shaikh, Chirayu Chokshi, Benjamin Brakel, William Maich, Shan Grewal, Chitra Venugopal, Sheila Singh. Inhibiting elements of the proteasome recovery pathway sensitizes glioblastoma to proteasome inhibitors [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 5846.

Abstract 2034: The NAE1 inhibitor MLN4924 sensitizes both BRCA1 wild type and mutant triple negative breast cancers to cisplatin by reducing the nucleotide excision repair protein XPC level

Abstract Background: Triple-negative breast cancer (TNBC) shows poor survival and prognosis, high recurrence, and poor response to conventional therapeutics. To develop novel therapeutics for TNBC, we explored the efficacy of the neddylation inhibitor, MLN4924. We showed that MLN4924 displayed increased sensitivity against TNBC compared to non-TNBC subtypes. Mechanistically, MLN4924 induced extensive re-replication and DNA damage leading to cell death. Furthermore, MLN4924 improved cisplatin efficacy by elevating the DNA damage levels. To demonstrate the mechanisms of MLN4924+cisplatin-mediated enhanced cell death, we examined the XPC level, a key factor in the nucleotide excision repair (NER) pathway, playing a central role in cisplatin damage repair. Neddylation of CUL4A promotes XPC ubiquitination which influences XPC binding to the DNA damage sites for NER. Methods: We examined the XPC protein level by Western blot assay and RNA level by Real Time PCR using both BRCA1-wild type (MDA-MB-231) and BRCA1-mutated (MDA-MB-436) cell lines and mouse xenograft tumor samples. We evaluated if the proteosome inhibitor MG132 stabilizes XPC ubiquitination and protein levels by treating these cells with MG132 for various times. We also overexpressed XPC in these cell lines and examined the effect on survival upon MLN4924 and MLN4924+cisplatin treatments. Results: Our results demonstrate that MLN4924 reduces XPC ubiquitination upon shorter drug treatment but reduces the protein level upon longer drug treatment in both BRCA1-wild type and BRCA1-mutated cell lines. MG132 treatment did not stabilize the XPC ubiquitination level upon shorter drug treatment but stabilized the protein level upon longer drug treatment. We also observed a reduction in the XPC protein level in tumor samples which correlated with the increase in the DNA damage level. Surprisingly, XPC overexpression improved the cell survival in both MLN4924- and MLN4924+cisplatin-treated BRCA1-wild type and mutated TNBC cells. Conclusion: We hypothesize that a reduction in the XPC ubiquitination and protein levels plays a role in cisplatin-induced DNA damage repair reducing NER efficiency and consequently increasing the DNA damage upon MLN4924+cisplatin treatment. Since overexpression of XPC results in improved survival of both MLN4924-and MLN4924+cisplatin-treated cells, we anticipate that XPC not only regulates cisplatin damage repair through NER but may have a broader role in MLN4924 sensitization beyond the NER pathway. Importantly, MLN4924 treatment does not affect the XPC mRNA level emphasizing that neddylation influences the XPC protein level. In summary, our research uncovers novel insights into the role of XPC in both MLN4924 and MLN4924+cisplatin sensitization, shedding light on potential avenues for innovative therapeutic strategies for TNBC patients. Citation Format: Shrilekha Misra, Mateusz Opyrchal, Alo Ray. The NAE1 inhibitor MLN4924 sensitizes both BRCA1 wild type and mutant triple negative breast cancers to cisplatin by reducing the nucleotide excision repair protein XPC level [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 2034.

Abstract 4234: Personalized therapeutic screening in patient derived organoids for gastroenteropancreatic neuroendocrine tumors

Abstract Introduction Gastroenteropancreatic Neuroendocrine Neoplasms (GEP-NENs) are a rare subset of cancers which nevertheless are a rising health burden. Development of new therapies suffers from several bottlenecks, including low patient accrual and poor understanding of tumor characteristics. Patient tumor organoids (PTOs) are a novel model capable of improving screening of patient tissue in an accurate, standardized, and high-throughput capacity. In this study, we utilized patient tumors for creation of high-fidelity PTOs from a variety of GEP-NEN primary origins to evaluate therapy responses. Methods Tumors from patients undergoing clinically guided surgeries were processed within two hours of resection and dissociated into single-cell suspension. Cells were encapsulated into Matrigel and cultured into two groups. The first group was grown for 10 days to assess viability then treated with a panel of clinically approved therapies and novel treatments recommended by high throughput NEN cell line screening for treatment sensitivity using the MIPE 5.0 library. The second group was grown for long-term expansion and biobanking, followed by characterization using immunohistochemistry and genetic profiling to ensure tumor cell maintenance. Results From March 2023-November 2023, 14 patients provided 30 tumors for PTO development. These included small intestine (n=5), pancreatic (n=8), and gastric (n=1) neuroendocrine tumors. Long-term culture (&amp;gt;3 passages) was successful for 23/30 (77%) specimens, with passage timing related to tumor grade. PTOs maintained immunohistochemical characteristics of the parent tumor types and demonstrated similar genetic profiles, including neuroendocrine tumor cell markers synaptophysin, chromogranin A, and matched grade-based Ki67 proliferative index. The early-stage therapeutic screening was performed for 12/14 (86%) patients, demonstrating tumor grade dependent treatment efficacy and showing clinically dose relevant sensitivity towards approved small molecule inhibitor therapies including cabozantinib and sunitinib in a patient and tumor origin-dependent manner. Testing of effective therapy classes recommended by cell line treatment panels suggested high level treatment efficacy for proteosome inhibitors, MEK inhibitors, and topoisomerase inhibitors. Conclusion Development of GEP-NEN PTOs is feasible for long term culture and standard of care therapy testing. Further study demonstrated the successful application of novel therapeutic options in PTOs for patients with GEP-NENs. Citation Format: Steven D. Forsythe, Srujana V. Yellapragada, Stephen G. Andrews, Jaydira del Rivero, Jonathan M. Hernandez, Naris Nilubol, James P. Madigan, Samira M. Sadowski. Personalized therapeutic screening in patient derived organoids for gastroenteropancreatic neuroendocrine 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 4234.

Abstract 5624: Dec2, a circadian rhythm gene facilitates pancreatic cancer dormancy through evasion of antitumor immunity

Abstract Metastatic recurrence following curative intent oncologic surgery is a major clinical problem in patients with pancreatic ductal adenocarcinoma (PDAC). These recurrences are from disseminated tumor cells (DTCs) and can sometimes occur years after surgery indicating that DTCs undergo a period of dormancy. The mechanisms that drive cancer dormancy and its awakening are poorly understood in part due to a lack of animal models that recapitulate dormant tumor cell biology. We created a novel model of PDAC dormancy where mice undergo surgery to remove the primary tumor and are followed for evidence of metastatic recurrence. Dormant DTCs can be isolated from mice without clinical evidence of recurrence for molecular studies. Single cell RNAseq of dormant DTCs detected that the circadian rhythm gene, Dec2 is upregulated. We knocked out (KO) Dec2 from murine pancreatic cancer cells and when implanted into the model we found almost no mice developed metastatic recurrence. When immunodeficient or immunocompetent mice depleted of CD4 and CD8 T cells were used as hosts, we observed no difference in survival in mice engrafted with Dec WT vs. KO cells indicating the survival benefit in the Dec KO group was due to an immune mediated mechanism. We performed a differential expression analysis on bulk RNAseq data comparing the Dec2 WT vs. KO cells and found antigen presentation a top upregulated pathway. We then observed that surface MHC-I was significantly upregulated in Dec2 KO cells as compared to wild type cells. Further mechanistic studies revealed that proteosome activity was significantly higher in Dec2 KO cells and treatment with proteosome inhibitors decreased surface MHCI levels in Dec2 KO cells. Cut and tag experiments revealed that Dec2 binds the promoter of a number of genes that regulate the proteosome. In conclusion, Dec2 promotes cancer dormancy by down regulating cell surface MHCI which facilitates immune evasion. Citation Format: Lan Wang, Chris Harris, Orjola Prela, Wade C. Narrow, Darren R. Carpizo. Dec2, a circadian rhythm gene facilitates pancreatic cancer dormancy through evasion of antitumor immunity [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 5624.

Abstract 6890: 2D Tumor cell culture based Ex vivo drug sensitivity screening platform for South African patient samples (leukemia, multiple myeloma, ovarian and uterine cancer) demonstrate potential for targeted cancer therapies

Abstract Resistance to standard chemotherapy is a major challenge with Leukemia (Leuk), Multiple Myeloma (MM), Ovarian Cancer (OvCa) and Uterine Cancer (UtCa) treatments, which ultimately leads to relapse. Our study objective is to establish a robust drug sensitivity screening platform that can identify drugs and drug combinations that are effective in precision medicine for individual South African patient samples (Leuk, MM, OvCa and UtCa). Given that resistance to chemotherapy treatment accounts for high mortality and morbidity, we focus on the hypothesis that several drug combinations will be required for patients to achieve better response for drug regimens beyond first line of chemotherapy. Therefore, our defined objectives were to 1) establish 2D ex vivo tumour cell culturing using South African patient samples; 2) develop a drug sensitivity screening platform through which selected single and drug combinations will be identified; 3) to provide South African cancer (OvCa, Ut Ca, CLL, MM) patients with individualized treatment options with effective drug combinations for targeted therapies. Through collaboration with, Steve Biko Hospital Pretoria, Chris Hani Baragwanath Hospital and Wits Donald Gordon Medical Centre, Johannesburg, South Africa, we performed 100 patient sample collections including Acute myeloid leukaemia (AML) (n=7), Chronic lymphocytic leukaemia (CLL) (n=4), Chronic myeloid leukaemia (CML) (n= 30), MM (n=40), OvCa (n=10), UtCa (n=4) and healthy donors (n=5). Culture setting for all patient-derived tumor cells were established through the 2D cancer cell culturing in 96 well plates. This was followed by functional drug sensitivity testing using a panel of FDA approved chemotherapy drugs. The average turnaround time from biopsy to drug sensitivity test results is currently at 14 days. We have completed ex vivo drug sensitivity screening to perform analysis on patient samples (n=80) using 30 drugs with a concentration range of 1-1000 nm. Our preliminary drug sensitivity screening studies show good response to proteosome inhibitors, melphalan, doxorubicin and kinase inhibitors. We have established a wound healing assay for OvCa and UtCa samples and demonstrated sustained cell growth for the period of 2 weeks with tumor cells growing faster than twin normal tissue. We are now at stage of performing drug sensitivity screening for OvCa and UtCa patient samples for both twin normal and tumor tissues. We have established a drug sensitivity screening platform and wound healing assay with primary patient derived cells that utilizes South African Patient samples to select effective drugs for monotherapy and also drug combinations. Citation Format: Mutsa Takundwa, Vanelle Kenmogne, Thudzelani Malise, Bernice Monchusi, Phumuzile Dube, Ekene Nweke, June Fabian, Heather Maher, Justin du Toit, Vinitha Philip-Cherian, Pascaline Fru, Adekunle Sajo, Arnold (Arrie) Mouton, Matthys C. van Aardt, Cathy Visser, Greta Dreyer, Deepak Govindaraj. 2D Tumor cell culture based Ex vivo drug sensitivity screening platform for South African patient samples (leukemia, multiple myeloma, ovarian and uterine cancer) demonstrate potential for targeted cancer therapies [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 6890.

Combined green analytical principles and quality by design for ultraperformance liquid chromatography analytical method development, the characterization and in-silico toxicity prediction of Ixazomib degradation products using mass spectrometry

Ixazomib citrate (IC) is the first oral selective proteosome inhibitor for treating multiple myeloma. IC is prone to degradation due to its oxidative deboronation and the amide bond, affecting patient health, drug quality, and efficacy. The stability of IC is crucial during drug development as it guides the inherent stability of the molecule, its degradation pathways, packing materials, and formulation development. Following the International Conference on Harmonization (ICH) Q1A (R2) and Q1B, a stability study were performed for both solution and solid-state stress studies. Under oxidative and alkaline conditions, 3 degradation products (DPs) were identified, separated, and method-validated according to ICH Q2 (R1) guidelines. From the Design Expert statistical tool, the Central Composite Design was used to optimize the final analytical method conditions, where the p-values for the model are < 0.05%. Green analytical chemistry has significantly reduced the use of hazardous organic solvents without losing chromatographic performance. The green separation and quantification of DPs and IC on Ultra Performance Liquid Chromatography (UPLC) using an Inert-Sustain C8 (50×3.0) mm 2.0 µm column with gradient elution using 10 mM ammonium acetate buffer (pH 5.0) and ethanol at a flow rate of 0.5 mL/min and detection at 230 nm. The results of green assessment tools like GAPI, AGREE, and Analytical eco-scale found that the method is excellent for the greenness of utilizing ethanol as a solvent, shorter runtime, and lesser waste. The method was validated as per ICH Q2 guidelines, and the results found it is sensitive, precise, accurate, robust, and linear for its intended use. The method is suitable for quantifying IC and its DPs from 2.0 to 150 µg/mL with R2 values of 0.9996 with a detection limit of 1.0 µg/mL. The plausible degradation structures and pathways of DPs were outlined using tandem mass spectra employed on LC-QTOF-MS/MS in both ESI positive and negative modes. The mechanistic explanation for establishing DPs was explained in detail. The ADMET Predictor™ software predicted the physicochemical and ADMET properties. The toxicity profile reveals that DP2 and DP3 are teratogenic, while D1 and D3 show phospholipidosis.

PHOTOTROPIN1 lysine 526 functions to enhance phototropism in Arabidopsis.

After blue-light exposure, ubiquitination of PHOTOTROPIN1 lysine 526 enhances phototropic responses. Arabidopsis blue-light photoreceptor, PHOTOTROPIN1 (PHOT1) mediates a series of blue-light responses that function to optimize photosynthesis efficiency. Blue-light sensing through the N-terminal sensory domain activates the C-terminal kinase activity of PHOT1, resulting in autophosphorylation. In addition to phosphorylation, PHOT1 lysine residue 526 (Lys526), after blue-light exposure, was found to carry a double glycine attachment, indicative of a possible ubiquitination modification. The functionality of PHOT1 Lys526 was investigated by reverse genetic approaches. Arginine replacements of PHOT1 Lys526, together with Lys527, complemented phot1-5 phot2-1 double mutant with attenuated phototropic bending, while blue-light responses: leaf expansion and stomatal opening, were restored to wild type levels. Transgenic seedlings were not different in protein levels of phot1 Lys526 527Arg than the wild type control, suggesting the reduced phototropic responses was not caused by reduction in protein levels. Treating the transformants with proteosome inhibitor, MG132, did not restore phototropic sensitivity. Both transgenic protein and wild type PHOT1 also had similar dark recovery of kinase activity, suggesting that phot1 Lys526 527Arg replacement did not affect the protein stability to cause the phenotype. Together, our results indicate that blocking Lys526 ubiquitination by arginine substitution may have caused the reduced phototropic phenotype. Therefore, the putative ubiquitination on Lys526 functions to enhance PHOT1-mediated phototropism, rather than targeting PHOT1 for proteolysis.