mTOR Inhibitor Research Articles

Targeting the mTOR-Autophagy Axis: Unveiling Therapeutic Potentials in Osteoporosis

Osteoporosis (OP) is a widespread age-related disorder marked by decreased bone density and increased fracture risk, presenting a significant public health challenge. Central to the development and progression of OP is the dysregulation of the mechanistic target of the rapamycin (mTOR)-signaling pathway, which plays a critical role in cellular processes including autophagy, growth, and proliferation. The mTOR-autophagy axis is emerging as a promising therapeutic target due to its regulatory capacity in bone metabolism and homeostasis. This review aims to (1) elucidate the role of mTOR signaling in bone metabolism and its dysregulation in OP, (2) explore the interplay between mTOR and autophagy in the context of bone cell activity, and (3) assess the therapeutic potential of targeting the mTOR pathway with modulators as innovative strategies for OP treatment. By examining the interactions among autophagy, mTOR, and OP, including insights from various types of OP and the impact on different bone cells, this review underscores the complexity of mTOR’s role in bone health. Despite advances, significant gaps remain in understanding the detailed mechanisms of mTOR’s effects on autophagy and bone cell function, highlighting the need for comprehensive clinical trials to establish the efficacy and safety of mTOR inhibitors in OP management. Future research directions include clarifying mTOR’s molecular interactions with bone metabolism and investigating the combined benefits of mTOR modulation with other therapeutic approaches. Addressing these challenges is crucial for developing more effective treatments and improving outcomes for individuals with OP, thereby unveiling the therapeutic potentials of targeting the mTOR-autophagy axis in this prevalent disease.

Mediator kinase inhibitors suppress triple-negative breast cancer growth and extend tumor suppression by mTOR and AKT inhibitors

Triple-negative breast cancers (TNBC) are treated primarily by chemotherapy and lack clinically validated therapeutic targets. In particular, inhibitors of the PI3K/AKT/mTOR pathway, abnormally activated in many breast cancers, failed to achieve clinical efficacy in TNBC due to the development of adaptive drug resistance, which is largely driven by the transcriptomic plasticity of TNBC. Expression of CDK8/19 Mediator kinases that control transcriptional reprogramming correlates with relapse-free survival and treatment failure in breast cancer patients, including TNBC. We now investigated how CDK8/19 inhibitors affect the growth of TNBC tumors and their response to mTOR and AKT inhibitors. In contrast to the effects of most anticancer drugs, all the tested human TNBC models (including patient-derived xenografts) responded to CDK8/19 inhibitors in vivo even when they did not respond in vitro. Furthermore, CDK8/19 inhibition extended the host survival of established lung metastases in a murine TNBC model, where the primary tumors were not significantly affected. CDK8/19 inhibitors synergized with an mTORC1 inhibitor everolimus and a pan-AKT inhibitor capivasertib in vitro and strongly potentiated these drugs in long-term in vivo studies. Transcriptomic analysis of tumors that responded or became adapted to everolimus revealed that drug adaptation in vivo was associated with major transcriptional changes in both tumor and stromal cells. Combining everolimus with a CDK8/19 inhibitor counteracted many of these changes and induced combination-specific effects on the expression of multiple genes that affect tumor growth. These results warrant the exploration of CDK8/19 Mediator kinase inhibitors as a new type of drugs for TNBC therapy.

PLAC1 augments the malignant phenotype of cervical cancer through the mTOR/HIF-1α/snail signaling pathway.

This study investigated the molecular mechanisms of placenta-specific protein 1 (PLAC1) in cervical cancer (CCa), aiming to elucidate its role in tumorigenesis through in vitro and in vivo experiments. CCa cell lines with overexpressed or silenced PLAC1 were established to evaluate its impact on cell cycle, apoptosis and the expression of key proteins in the PLAC1/mTOR/HIF-1α/Snail signaling pathways. Functional assays were conducted to assess the influence of the PLAC1/mTOR/HIF-1α/Snail regulatory pathway on cell proliferation, migration and invasion. The role of the mTOR signaling pathway in PLAC1-mediated modulation of CCa characteristics was validated using a mTOR activator (MHY1485) and a mTOR inhibitor (Rapamycin) respectively. HIF1A siRNA was introduced to confirm the role of HIF1A. Furthermore, an in vivo nude mouse model was constructed to confirm PLAC1's influence on tumorigenesis and metastasis in CCa. PLAC1 upregulated hypoxia-inducible factor (HIF)-1α and Snail, promoting CCa cell proliferation, migration, and invasion via the mTOR/HIF-1α/Snail pathway. Enrichment analysis of PLAC1-associated differentially expressed genes implicated their involvement in CCa and tumor promotion. In a xenograft mouse model, PLAC1 exhibited a pro-tumorigenic effect, which can be reversed by siRNA targeting HIF1A. This study enhances our understanding of PLAC1's role and molecular mechanisms in CCa progression, highlighting its potential as a diagnostic, prognostic, and therapeutic marker for the management of CCa.

Clinicopathologic feature and treatment progress of high-grade ovarian neuroendocrine tumors.

High-grade Ovarian neuroendocrine tumors represent a rare subset of ovarian neoplasms characterized by aggressive behavior, poor prognosis, and early metastasis. Despite their clinical significance, the management of these tumors lacks consensus due to their low incidence. This comprehensive review encompasses literature spanning from 1991 to 2024, focusing on the clinical presentation, diagnostic criteria, differential diagnosis, prognostic indicators, treatment modalities, and recent advancements in the understanding of this condition. Notably, a substantial proportion of affected individuals present during the perimenopausal period with unilateral lesions displaying mixed histological components. Biomarkers such as CA125, CA199, and NSE hold promise for aiding in the diagnosis and screening of ovarian neuroendocrine tumors. Unfortunately, patients exhibit a dismal prognosis even diagnosed at an early stage. Primary treatment strategies predominantly involve surgical intervention coupled with etoposide-cisplatin combination chemotherapy. In cases of recurrence, second-line chemotherapeutic agents including paclitaxel, irinotecan, and doxorubicin are commonly employed alongside localized radiotherapy. While specific genetic mutations remain elusive, emerging evidence suggests potential therapeutic effect involving mTOR inhibitors, PD-1 monoclonal antibodies, and antiangiogenic agents based on isolated case reports. The exploration of representative set of mutations will help for precise targeted therapies and remains a focal point of our ongoing research efforts.

MTOR inhibitors potentially preserve fertility in female patients with haematopoietic malignancies: a narrative review.

Haematologic malignancies are considered among the more common adolescent and young adult (AYA) cancers. Many female AYA patients with haematopoietic malignancies face impaired fertility. Haematologic malignancies patients tend to be treated with more aggressive systemic chemotherapy than that of solid tumours. In adult women, treatment-related contraception causes age-related fertility loss. Graft-versus-host disease (GVHD) after allogeneic haematopoietic stem cell transplantation is associated with decreased fertility. Ovarian cryopreservation is often indicated for haematopoietic malignancies; however, follicle loss associated with ovarian cryopreservation and ovarian minimal residual disease, which result in the withdrawal of the transplantation, are important issues. These problems may not be fully addressed by conventional methods of fertility preservation, such as oocyte, embryo, and ovarian cryopreservation, leaving room for research into new treatment approaches, such as fertility preservation drugs. In recent years, preclinical studies have shown that mTOR inhibitors may preserve chemotherapy-induced follicular loss, may have follicle-preserving effects on follicle loss associated with cryopreservation and transplantation of ovarian tissue, may have fertility-preserving effects on aging-related infertility. Clinical studies have shown that mTOR inhibitors may have the potential for indirect fertility preservation by controlling GVHD, have a limited anti-tumor effect against haematopoietic malignancies. The purpose of this article is to outline the various issues faced by female survivors of haematopoietic malignancies and discuss the potential of mTOR inhibitors as a safe treatment option. Based on current research, mTOR inhibitors seem promising and innovative fertility preservation agents regarding preclinical conditions, and further study, including clinical trials, should be expected.

Analysis of hsa_circ_0136256 as a biomarker for fibrosis in systemic sclerosis.

Exploration of whether circRNAs in the skin of systemic sclerosis (SSc) model mice interact with 4E-BP1 protein to mediate the mTOR signaling pathway to regulate SSc fibrosis is crucial to identify homologous human circRNAs as markers to guide the diagnosis and treatment of SSc. C57BL/6 mice aged 6-8 weeks and weighing approximately 20 g were subcutaneously injected with bleomycin (BLM) to establish an SSc model. High-throughput sequencing was used to screen the differentially expressed circRNA in the skin of SSc model mice and control mice. RNA immunoprecipitation and RNA pulldown confirmed the interaction between circRNA and 4E-BP1 protein. SSc model mice were treated with empty plasmid (OE-NC), overexpression plasmid of mmu_circ_0005372 (OE-circ_0005372), interference plasmid of mmu_circ_0005372 (sh-circ5372), mutant plasmid of mmu_circ_0005372 (circ5372-MT), mTOR activator (MHY1485), mTOR inhibitor (omipalisib), or JAK1/2 inhibitor (ruxolitinib). Sections of mouse skin tissue were stained with Hematoxylin and eosin and Masson's stain. The collagen volume fraction (CVF) was calculated as CVF = area of blue collagen/total area with ImageJ. The correlation between homologous human circRNAs and clinical data was analyzed. Compared to the control group, 21,839 circRNAs were upregulated and 27, 946 circRNAs were downregulated in the skin tissue of mice in the SSc model group. Among them was mmu_circ_0005372, which is derived from the FZD3 gene, is closely related to fibrosis, and is involved in the mTOR signaling pathway. Hsa_circ_0136256 was identified as the homologous human circRNA of mmu_circ_0005372. RT-qPCR confirmed that the expression of mmu_circ_0005372 was significantly reduced in the skin tissue of SSc mice, and the expression of hsa_circ_0136256 was significantly reduced in the peripheral blood mononuclear cells of patients with SSc. The interaction between mmu_circ_0005372 and 4E-BP1 protein was inhibited in the skin tissue of SSc model mice. The results showed that the CVF of OE-circ_0005372 group was significantly lower than that of the sh-circ5372, circ5372-MT, and MHY1485 groups, indicating that OE-circ5372 significantly improved skin fibrosis in the SSc mice. ROC curve analysis was performed on hsa_circ_0136256 (AUC = 0.719, P = 0.035). The expression of hsa_circ_0136256 was negatively correlated with COL IV, RDW-SD, and RDW-CV, and positively correlated with VC, PLT, and PCT. The results suggested that hsa_circ_0136256 may have important roles in the clinical diagnosis of SSc. Mmu_circ_0005372 and homologous human hsa_circ_0136256 may be biomarkers and therapeutic targets for SSc fibrosis.

DEPTOR attenuates asthma progression by suppressing endoplasmic reticulum stress through SOD1.

Endoplasmic reticulum (ER) stress has been shown to play a pivotal role in the pathogenesis of asthma. DEPTOR (DEP Domain Containing MTOR Interacting Protein) is an endogenous mTOR inhibitor that participates in various physiological processes such as cell growth, apoptosis, autophagy, and ER homeostasis. However, the role of DEPTOR in the pathogenesis of asthma is still unknown. In this study, an ovalbumin (OVA)-induced mice model and IL-13 induced 16HBE cells were used to evaluate the effect of DEPTOR on asthma. A decreased DEPTOR expression was shown in the lung tissues of OVA-mice and IL-13 induced 16HBE cells. Upregulation of DEPTOR attenuated airway goblet cell hyperplasia, inhibited mucus hypersecretion, decreased the expression of mucin MUC5AC, and suppressed the level of inflammatory factors IL-4 and IL-5, which were all induced by OVA treatment. The increased protein expression of ER stress markers GRP78, CHOP, unfolded protein response (UPR) related proteins, and apoptosis markers in OVA mice were also inhibited by DEPTOR overexpression. In IL-13 induced 16HBE cells, overexpression of DEPTOR decreased IL-4, IL-5, and MUC5AC levels, preventing ER stress response and UPR process. Furthermore, from the proteomics results, we identified that SOD1 (Cu/Zn Superoxide Dismutase 1) may be the downstream factor of DEPTOR. Similar to DEPTOR, upregulation of SOD1 alleviated asthma progression. Rescue experiments showed that SOD1 inhibition abrogates the remission effect of DEPTOR on ER stress in vitro. In conclusion, these data suggested that DEPTOR attenuates asthma progression by suppressing endoplasmic reticulum stress through SOD1.

NCOG-33. MTOR INHIBITORS AS ADJUVANT TARGETED THERAPY IN PEDIATRIC PATIENTS WITH PROGRESSIVE OR REFRACTORY LOW-GRADE GLIOMA: A SINGLE-CENTER RETROSPECTIVE STUDY

Abstract Low grade gliomas (LGG) represent about one-third of all pediatric central nervous system tumors, with about half having disease progression despite upfront surgery and adjuvant therapies. Current treatments for LGG progression either produce toxic side effects (i.e., radiation therapy) or do not generate durable responses. Targeted agents are an effective way of attacking tumors with identified genetic mutations, but in some cases, a complete response can be subverted by the heterogeneity of tumors. Additionally, most tumors do not carry any targetable mutations. Temsirolimus and everolimus are mTOR inhibitors that have previously been shown to be well-tolerated in early clinical studies in pediatric solid tumors. We performed a retrospective study to look at the toxicity profile of mTOR inhibitors when given in combination therapy and treatment response in patients with progressive or refractory LGG. We examined 20 patients with a diagnosis of LGG including mixed glioma and glioneuronal tumors who received treatment at our institution from 2016-2024 with targeted therapy, of which 8 patients also received temsirolimus or everolimus. Of these 8 patients, 2 had partial response, 2 had minor response, 3 had stable disease, and 1 had progressive disease. The average number of cycles received was 13.6 (range 3-24). Most observed side effects were grade 2 or less, including nausea, transaminitis, myelosuppression, diarrhea, and hyperlipidemia while grade 3/4 toxicities that required dose modification included mucositis, hyperglycemia, and hyperlipidemia. Overall, the addition of temsirolimus to treatment regimens of pediatric patients with heavily pretreated refractory LGG prolonged progression free survival by an average of 478 days with only one patient progressing while on therapy. These results demonstrate feasibility and preliminary efficacy of adding mTOR inhibitors as adjuvant therapy in this patient population. There is dire need of large prospective collaborative studies in the future.

DISP-19. ETHNIC DISPARITIES IN METASTASIS PATTERNS AND TREATMENT UTILIZATION AMONG METASTATIC BREAST CANCER PATIENTS WITH BRAIN METASTASIS: A RETROSPECTIVE ANALYSIS OF US HEALTH SYSTEMS DATA (2019-2023)

Abstract INTRODUCTION The treatment landscape for metastatic breast cancer (MBC) with brain metastasis (BM) has evolved due to novel therapies. However, outcomes remain poor and vary among groups. This study investigated ethnic disparities in metastasis (mets) patterns and treatment use among MBCBM patients (pts). METHODS We analyzed deidentified data from seven US health systems in the Guardian Research Network from December 2019 to December 2023. Pts with MBC were categorized by IHC scores: hormone receptor+/HER2-, HER2-low (IHC 1+ or 2+ with negative FISH), HER2 positive, and Triple Negative (TNBC). We used descriptive and comparative statistical analysis. RESULTS Of 421 MBC pts, 200 (47.5%) had HER2+, 167 (39.7%) had HR+/HER2-, and 54 (12.8%) had TNBC. 159 (37.7%) were reclassified as HER2-low, primarily from HR+/HER2- (127; 76.0%) and TNBC (32; 59.3%). Bone mets developed in 29.6% of pts, more prevalent in HER2+ (39.5%), TNBC (25.9%), and HR+/HER2- (19.1%) groups. Non-Hispanics showed higher BM prevalence (74.4% vs. 25.6%). HR+/HER2- BM pts had higher bone mets (71.88%) than HER2+ BM (65.82%). TNBC BM pts had the highest rate of liver mets (57.1%). HER2-low BM pts showed mets across liver (40%), lung (34.29%), and bone (68.57%). In the HER2+ BM group, non-Hispanics had higher liver (40.13% vs. 32.35%) and bone mets (69.08% vs. 52.94%) than Hispanics. In TNBC BM group, Hispanics had higher liver mets (66.67% vs. 35%), while non-Hispanics had higher lung mets (32.5% vs. 11.11%). Both ethnic groups in HR+/HER2- category had high bone mets (78.95% vs. 73.33%). There were disparities in the use of CDK4/6 inhibitors, ICIs, and mTOR inhibitors, with Hispanics frequently using them. CONCLUSION HR+/HER2- BM pts were most affected by bone mets, followed by HER2+ BM. TNBC BM pts predominantly had liver mets. Non-Hispanics had higher BM prevalence. Hispanics frequently used ICIs, CDK4/6 and mTOR inhibitors, which were more frequently used by Hispanics. Further research should explore these disparities in mets patterns, treatment choices, and responses.

CNSC-52. OLIGODENDROGLIOMA SPATIAL TRANSCRIPTOMIC SEQUENCING REVEALS THERAPY-DEPENDENT EVOLUTION OVER TIME

Abstract Oligodendroglioma evolution is incompletely understood. Here we analyze serial oligodendroglioma samples to define genomic and cellular mechanisms underlying treatment resistance. RNA sequencing was performed on 53,406 spatial transcriptomes from 31 oligodendrogliomas (IDH mutant, 1p/19q-codeleted) that were resected from 16 patients. There were 15 CNS WHO grade 2 and 16 grade 3 oligodendrogliomas, which were stratified for temporal progression across grades (n=5 grade 2 to 2, n=5 grade 2 to 3, n=6 grade 3 to 3) and treatments between serial resections (n=2 TMZ/RT, n=2 TMZ, n=1 mTOR inhibition, n=1 IDH inhibition, n=10 surgical monotherapy). Spatial transcriptomic clusters were defined using cell signature gene sets, cell cycle analysis, differentially expressed marker genes, immunohistochemistry, spatial copy number alterations (CNAs), and deconvolution of 18,628 oligodendroglioma single-cell transcriptomes from 16 independent patients. Specificity was tested using immunofluorescence on independent oligodendrogliomas that did not recur after surgical monotherapy (n=8 samples, median follow-up 8.4 years) and spatial transcriptomic sequencing on 8 matched-paired astrocytomas from 4 patients. Integrated uniform manifold approximation and projection revealed a proneural/NPC-like cluster that was enriched in grade 3 oligodendroglioma samples and represented the starting point in oligodendroglioma lineage differentiation using RNA velocity, Monocle, and subclonal spatiotemporal CNA evolution. Comparison across treatment regimens showed (1) enrichment of the proneural/NPC-like cluster in recurrent versus primary tumors that were treated with surgical monotherapy, (2) enrichment of a proneural/OPC-like cluster and depletion of an oligodendrocyte-like cluster after TMZ/RT, (3) enrichment of proneural/NPC-like and immediate-early response clusters after TMZ/RT, (4) enrichment of the oligodendrocyte-like cluster following mTOR inhibition, and (5) enrichment of cancer associated fibroblasts (CAFs) following IDH inhibition. These data show the spatiotemporal landscape of oligodendroglioma is associated with branched lineage differentiation that is modified by postoperative therapy, and suggest that therapy-dependent druggable dependencies may exist to treat oligodendrogliomas that are resistant to standard interventions.

MSCs-derived EVs protect against chemotherapy-induced ovarian toxicity: role of PI3K/AKT/mTOR axis.

Chemotherapy detrimentally impacts fertility via depletion of follicular reserves in the ovaries leading to ovarian failure (OF) and development of estrogen deficiency-related complications. The currently proposed options to preserve fertility such as Oocyte or ovarian cortex cryopreservation are faced with many technical obstacles that limit their effective implementation. Therefore, developing new modalities to protect ovarian function remains a pending target. Exosomes are nano-sized cell-derived extracellular vesicles (EVs) with documented efficacy in the field of regenerative medicine. The current study sought to determine the potential beneficial effects of mesenchymal stem cells (MSCs)-derived EVs in experimentally induced OF. Female albino rats were randomly allocated to four groups: control, OF group, OF + MSCs-EVs group, OF + Rapamycin (mTOR inhibitor) group, and OF + Quercetin (PI3K/AKT inhibitor) group. Follicular development was assessed via histopathological and immunohistochemical examination, and ovarian function was evaluated by hormonal assay. PI3K/Akt/mTOR signaling pathway as a key modulator of ovarian follicular activation was also assessed. MSCs-EVs administration to OF rats resulted in restored serum hormonal levels, preserved primordial follicles and oocytes, suppressed ovarian PI3K/AKT axis and downstream effectors (mTOR and FOXO3), modulated miRNA that target this axis, decreased expression of ovarian apoptotic markers (BAX, BCl2) and increased expression of proliferation marker Ki67. The present study validated the effectiveness of MSCs-EVs therapy in preventing ovarian insufficiency induced by chemotherapy. Concomitant MSCs-EVs treatment during chemotherapy could significantly preserve ovarian function and fertility by suppressing the PI3K/Akt axis, preventing follicular overactivation, maintaining normal ovarian cellular proliferation, and inhibiting granulosa cell apoptosis.

Systemic therapy for non-clear cell renal cell carcinomas: A systematic review.

Renal cell carcinoma (RCC) is the most common kidney cancer, with clear cell RCC being the predominant subtype. However, non-clear cell RCC constitutes a significant proportion of cases, presenting distinct challenges in treatment due to its varied histological subtypes. Despite recent advancements, the optimal therapeutic approach for non-clear cell RCC remains uncertain due to limited high-quality evidence. This systematic review aims to evaluate the efficacy of systemic therapies in nccRCC subgroups. A comprehensive literature search identified studies from 2010 to 2024, using PubMed and Clinicaltrials.gov databases focusing on clinical trials and treatment outcomes. Results highlight the evolving therapeutic landscape, with targeted agents and immunotherapy demonstrating promising anti-tumor effects. Notably, tyrosine kinase inhibitors (TKIs) such as sunitinib and mTOR inhibitors like temsirolimus have shown efficacy across different subtypes. Combination therapies, including immunotherapy-based regimens, have also shown favorable outcomes. immune checkpoint inhibitors such as nivolumab and pembrolizumab demonstrated encouraging antitumor activity. Furthermore, specific targeting of signaling pathways, such as the c-MET pathway, has demonstrated efficacy in certain PapillaryRCC. While combination therapies, including immunotherapies, have shown positive outcomes, immune checkpoint inhibitors like nivolumab and pembrolizumab have demonstrated encouraging antitumor activity. Additionally, targeting the c-MET pathway has proven effective in certain papillary RCC. Further research is warranted to establish optimal treatment strategies and improve outcomes for patients with non-clear cell RCC. Systemic therapy for non-clear cell RCC is complex and evolving. Further research is needed to delineate optimal treatment strategies for different histological subtypes and improve patient outcomes.

CTNI-85. FINAL RESULTS FROM N2M2/NOA-20

Abstract BACKGROUND MGMT promoter methylation determines benefit from temozolomide (TMZ). Trials aiming at replacing TMZ with targeted agents in not molecularly selected patient populations have failed. Solid evaluation of the MGMT promotor methylation status is critical. METHODS The phase I/IIa umbrella trial NCT Neuro Master Match (N2M2) in patients with newly diagnosed glioblastoma aimed at showing safety, feasibility, and preliminary efficacy of targeted compounds in addition to radiotherapy. In five subtrials (alectinib, idasanutlin, palbociclib, vismogedib and temsirolimus) patients were included according to the best matching molecular alteration. Patients without matching alterations were randomized between atezolizumab, asunercept or TMZ as standard of care. Primary objective of the phase I parts of the trial was dose finding or dose validation. In the phase IIa trials, centrally determined progression-free survival at six months (PFS-6) is used as endpoint for efficacy with interim analyses for futility (H0: p=0.231). RESULTS From May 2018 through July 2022, 301 patients were enrolled and 228 treated in 13 German NOA sites. MGMT was determined locally and confirmed centrally by pyrosequencing as well as methylation arrays. The TMZ subtrial showed a PFS-6 of 18.52% (10/54 patients) (p=0.8311) and a median overall survival (mOS) of 12.1 months. Asunercept: PFS-6 of 15.4% (4/26) (p=0.8825) and mOS of 13.0 months. Atezolizumab: PFS-6 of 21.4% (9/42) (p=0.660) and mOS of 11.7 months. Palbociclib with patients demonstrating CDK4 amplification or CDKN2A/B codeletion: PFS-6 of 24.4% (10/41) (p=0.4823) and mOS of 12.6 months. Temsirolimus with patients demonstrating mTOR activation: PFS-6 of 39.1% (18/46) (p=0.0109) and mOS of 15.4 months. For the other arms, phase IIa has not been reached. CONCLUSIONS There is clinical activity of temsirolimus in patients with tumors harboring an activated mTOR pathway although this is not positively prognostic without mTOR inhibition; there is no clinical activity for asunercept and atezolizumab in not molecularly selected patients nor palbociclib in molecularly selected patients. Potential biomarkers will be discussed.

CSIG-03. MT-125 INHIBITS NON-MUSCLE MYOSIN IIA AND IIB, SYNERGIZES WITH ONCOGENIC KINASE INHIBITORS, AND PROLONGS SURVIVAL IN GLIOBLASTOMA

Abstract We have shown that members of the non-muscle myosin II (NMII) family of molecular motors are non-redundant drivers of both invasion and proliferation in glioblastoma (GBM), consistent with the canonical roles NMII isoforms play in cell motility and cytokinesis. However, we have also found that NMII also has a non-canonical role by regulating oncogenic signaling pathways relevant to GBM pathogenesis. This unexpected finding has led us to identify and characterize MT-125, a highly specific small molecule inhibitor of the two predominant NMII isoforms in GBM (NMIIA and NMIIB), and we have studied its effects in pre-clinical GBM models. MT-125 has high brain penetrance and retention; an excellent safety profile in rodents and canines with no changes in metabolic or hematologic indices after prolonged administration; is well-tolerated with daily dosing for at least 85 consecutive days; blocks GBM invasion and cytokinesis, consistent with the canonical roles of NMII; and prolongs median survival by 35% as a single agent in murine GBM models. MT-125 increases signaling along both the PDGFR- and MAPK-driven pathways through a mechanism that involves the upregulation of reactive oxygen species, leading to oncogene addiction to these pathways. As a consequence, MT-125 is synthetically lethal when combined with FDA-approved, CNS-permeant inhibitors of PDGFR and mTOR in vitro. Combining MT-125 with sunitinib, a PDGFR inhibitor, or paxalisib, a combined PI3 Kinase/mTOR inhibitor, in vivo doubles median survival in a highly aggressive murine orthotopic GBM model. Furthermore, combining MT-125 with sunitinib produces tumor free remissions of >100 days--2.5-fold greater than median survival of either drug alone—in approximately 40% of mice. Our results provide a powerful rationale for developing NMII targeting strategies to treat cancer and demonstrate that MT-125 has strong clinical potential for the treatment of GBM.

The Antipsychotic Drug Aripiprazole Suppresses Colorectal Cancer by Targeting LAMP2a to Induce RNH1/miR-99a/mTOR-Mediated Autophagy and Apoptosis.

The mammalian target of rapamycin (mTOR) is a critical signaling hub for sustaining cancer survival. Targeting mTOR and inducing autophagic cell death downstream of it represent promising therapeutic strategies for cancer prevention. A US Food and Drug Administration-approved drug library containing 616 small molecules is used to screen anticancer drugs against colorectal cancer (CRC) cells that rely on mTOR. This led to the identification of an antipsychotic drug aripiprazole, which significantly induced mTOR inhibition and autophagic apoptosis in CRC, in vitro and in vivo. The use of drug affinity response target stability identified lysosome-associated membrane protein 2A (LAMP2a) as a direct target of aripiprazole. LAMP2a-deficient CRC cells are refractory to aripiprazole. High LAMP2a expression is associated with poor survival of patients with CRC and negatively correlated with expression of ribonuclease inhibitor 1 (RNH1), which is later confirmed as a novel substrate of LAMP2a. Mechanistically, aripiprazole bound to the Lys401-His404 of LAMP2a and repressed its activity, subsequently inactivating RNH1/miR-99a/mTOR signaling and inducing autophagy-mediated apoptosis, thereby suppressing tumorigenesis. Liposome-mediated delivery of aripiprazole in combination with fluorouracil elicited superior therapeutic benefits in CRC, as compared to single treatments, thereby highlighting that aripiprazole may be repurposed as a novel therapeutic agent for CRC treatment.

Inhibitors of the mTOR signaling pathway can play an important role in breast cancer immunopathogenesis.

This study explores the critical role of inhibitors targeting the mammalian target of rapamycin (mTOR) signaling pathway in breast cancer research and treatment. The mTOR pathway, a central regulator of cellular processes, has been identified as a crucial factor in the development and progression of breast cancer. The essay explains the complex molecular mechanisms through which mTOR inhibitors, such as rapamycin and its analogs, exert their anticancer effects. These inhibitors can stop cell growth, proliferation, and survival in breast cancer cells by blocking critical signaling pathways within the mTOR pathway. Furthermore, the essay discusses the implications of using mTOR inhibitors as a comprehensive therapeutic strategy. It emphasizes the potential benefits of combining mTOR inhibitors with other treatment approaches to enhance the effectiveness of breast cancer treatment. The evolving landscape of breast cancer research underscores the significance of mTOR as a therapeutic target and highlights ongoing efforts to improve and optimize mTOR inhibitors for clinical use. In conclusion, the essay asserts that inhibitors of the mTOR signaling pathway offer a promising approach in the fight against breast cancer. These inhibitors provide a focused and effective intervention targeting specific dysregulations within the mTOR pathway. As research advances, the integration of mTOR inhibitors into customized combination therapies holds excellent potential for shaping a more effective and personalized approach to breast cancer treatment, ultimately leading to improved outcomes for individuals affected by this complex and diverse disease.

In-Human Clinical Experience with Direct Stick Embolization of Low-Flow Vascular Malformations Using an mTOR Inhibitor

BackgroundWhile direct stick embolization (DSE) of low-flow vascular malformations (LFVMs) with off-label embolotherapeutic compounds is the current mainstay of therapy, systemic oral mTOR inhibition has evolved into an important adjunctive therapy that is associated with frequent blood draws, systemic toxicity, and rebound signs/symptoms upon cessation. We, herein, report our experience with in-human DSE of LFVMs with an mTOR inhibitor for direct, intralesional targeting of the culprit mutated pathway without repeated systemic exposure. MethodsSince 2020, 33 procedures involving DSE were performed in 25 patients with LFVMs using a patented formulation and technique involving the intravenously compatible mTOR inhibitor Yale-OCR7737, used as a liquid compound in a collagen matrix emulsion for added viscosity and intralesional residence. Data was prospectively maintained and retrospectively reviewed for technical success (successful catheterization of the lesion and intralesional delivery of compound); clinical success (improvement in signs/symptoms with radiologically documented reduction in flow and/or volume of treated lesion); complications; side effects; and re-interventions. ResultsFrom 2020 to 2023, 33 procedures involving DSE were performed using Yale-OCR7737 in 25 patients (10[40%] men; 15[60%] women; mean age: 28 years [range 1 -70 years]) with LFMVs involving the head/neck (48%) and limbs (40%); 88% were non-syndromic while 12% had Klippel-Trenaunay Syndrome; 68% exhibited venous malformations, while 32% had lymphatic malformations. Technical and clinical success were 100%. Mean DSE sessions per patient was 1.4 (range 1 to 5). Localized intravascular coagulopathy was present after 16 (49%) DSE procedures; D-dimer improved post-DSE in 7 cases. No perioperative or delayed complications occurred. Side-effects were 7 (21%) cases of self-limited, transient oral aphthous ulcers. ConclusionsOur findings suggest that DSE of LFVMs with mTOR inhibitors (Yale-OCR7737) may be safe and effective. This may represent the new embolotherapeutic frontier in the endovascular treatment of LFMVs.

FBXO22 inhibits colitis and colorectal carcinogenesis by regulating the degradation of the S2448-phosphorylated form of mTOR

Inflammatory bowel disease (IBD) is a considerable threat to human health with a significant risk for colorectal cancer (CRC). However, currently, both the molecular pathogenesis and therapeutic treatment of IBD remain limited. In this report, using both systemic and intestinal epithelium-specific gene knockout mouse models, we demonstrate that FBXO22, a substrate receptor within the SKP1-Cullin 1-F-box family of E3 ubiquitin ligases, plays an inhibitory role in the Azoxymethane/Dextran Sodium Sulfate-induced colorectal inflammatory responses and CRC. FBXO22 targets the serine 2448-phosphorylated form of mammalian mechanistic target of rapamycin (pS2448-mTOR) for ubiquitin-dependent degradation. This proteolytic targeting effect is established based on multiple lines of evidence including the results of colon tissue immunoblots, analysis of cultured cells with altered abundance of FBXO22 by depletion or overexpression, comparison of protein decay rate, effects on mTOR substrates S6K1 and 4E-BP1, analysis of protein-protein interactions, phosphor-peptide binding and competition, as well as reconstituted and cellular ubiquitination. Finally, we have shown that mTOR inhibitor rapamycin (RAPA) was able to alleviate the effects of fbxo22 deletion on colorectal inflammatory response and CRC. These RAPA effects are correlated with the ability of RAPA to inhibit pS2448-mTOR, pS6K1, and p4E-BP1. Collectively, our data support a suppressive role for FBXO22 in colorectal inflammation signaling and CRC initiation by targeting pS2448-mTOR for degradation.

The Combined Inhibition of SREBP and mTORC1 Signaling Synergistically Inhibits B-Cell Lymphoma.

The sterol regulatory element-binding protein (SREBP) pathway is essential for maintaining sterol homeostasis during B cell activation and germinal center B cell proliferation. However, its potential as a therapeutic target to treat B-cell lymphoma remains unclear. We examined SREBP protein expression in human B-cell lymphoma samples using immunohistochemistry. Additionally, we conducted invitro studies using SREBP signaling inhibitors in combination with rapamycin to assess their effects on cell proliferation and lipid metabolism in B-cell lymphoma cells. Our analysis revealed high levels of SREBP2 protein expression in human B-cell lymphoma samples. Inhibiting SREBP signaling or its downstream target HMG-CoA reductase (HMGCR) with Fatostatin or Simvastatin effectively suppressed B-cell lymphoma cell proliferation. However, B-cell lymphoma cells responded to statin treatment by activating the mTORC1-pS6 pathway, suggesting a compensatory mechanism to overcome statin-induced cell cycle arrest. Combining low-dose statin treatment with the mTOR inhibitor rapamycin produced a synergistic effect, significantly inhibiting B-cell lymphoma proliferation, cell cycle progression, and lipid raft formation. These results highlight the potential of a combined therapeutic approach targeting both SREBP and mTORC1 as a novel strategy for treating B-cell lymphoma.

A Phase 1 Study of ABI-009 (Nab-sirolimus) in Combination With Temozolomide and Irinotecan in Pediatric Patients With Recurrent or Refractory Solid Tumors, Including CNS Tumors-A Children's Oncology Group Pediatric Early Phase Clinical Trial Network Study ADVL1514.

Nab-sirolimus (ABI-009, nab-rapamycin; Aadi Bioscience Inc. [Aadi]) is a human albumin-bound form of sirolimus nanoparticles, a potent mTOR inhibitor. This phase I trial was conducted to define dose-limiting toxicities (DLT), maximum tolerated or recommended phase II dose (MTD/RP2D), and pharmacokinetics of Nab-sirolimus in combination with temozolomide and irinotecan. Using a rolling 6 design, Nab-sirolimus was administered intravenously (IV) on days (D) 1 and 8 of cycle (C) 1. In subsequent cycles, Nab-sirolimus was administered D1 and D8 in combination with temozolomide (125 mg/m2/dose, maximum 250 mg/dose) and irinotecan (90 mg/m2/dose) orally, daily on D1-5. Cycle duration was 21 days. Three dose levels (DL) of Nab-sirolimus were investigated (DL1: 35 mg/m2/dose, DL-1: 20 mg/m2/dose, and DL-2: 15 mg/m2/dose). The observation period for estimating the MTD/RP2D was defined by cycles 1 and 2. Thirty-three patients were enrolled, 32 were eligible. Dose determination included 17 evaluable patients, median (range) age 12 (2-20) years and six additional patients were enrolled (four evaluable for toxicity) on a pharmacokinetic cohort. C1 or C2 DLTs were primarily thrombocytopenia including 2/5 patients at DL1, 2/6 patients at DL-1, and 1/6 patients at DL-2. One patient (DL1) with Ewing Sarcoma had a partial response and remained on study for 35 cycles. Rapamycin clearance was dose dependent. Irinotecan clearance and its active metabolite SN-38 exposure were not affected by coadministration with Nab-sirolimus. The MTD for Nab-sirolimus was 15 mg/m2/dose IV on D1 and D8 in combination with temozolomide 125 mg/m2/dose and oral irinotecan 90 mg/m2/dose daily for 5 days during 21D cycles. ClinicalTrials.gov identifier NCT02975882.