Burden In Mice Research Articles

Unraveling the metastasis-preventing effect of miR-200c in vitro and in vivo.

Advanced breast cancer, as well as ineffective treatments leading to surviving cancer cells, can result in the dissemination of these malignant cells from the primary tumor to distant organs. Recent research has shown that microRNA 200c (miR-200c) can hamper certain steps of the invasion-metastasis cascade. However, it is still unclear whether miR-200c expression alone is sufficient to prevent breast cancer cells from metastasis formation. Hence, we performed a xenograft mouse experiment with inducible miR-200c expression in MDA-MB 231 cells. The ex vivo analysis of metastatic sites in a multitude of organs, including lung, liver, brain, and spleen, revealed a dramatically reduced metastatic burden in mice with miR-200c-expressing tumors. A fundamental prerequisite for metastasis formation is the motility of cancer cells and, therefore, their migration. Consequently, we analyzed the effect of miR-200c on collective- and single-cell migration in vitro, utilizing MDA-MB 231 and MCF7 cell systems with genetically modified miR-200c expression. Analysis of collective-cell migration revealed confluence-dependent motility of cells with altered miR-200c expression. Additionally, scratch assays showed an enhanced predisposition of miR-200c-negative cells to leave cell clusters. The in-between stage of collective- and single-cell migration was validated using transwell assays, which showed reduced migration of miR-200c-positive cells. Finally, to measure migration at the single-cell level, a novel assay on dumbbell-shaped micropatterns was performed, which revealed that miR-200c critically determines confined cell motility. All of these results demonstrate that sole expression of miR-200c impedes metastasis formation in vivo and migration in vitro and highlights miR-200c as a metastasis suppressor in breast cancer.

Targeting NLRP3 inhibits AML progression by inducing PERK/eIF2-mediated apoptosis

BackgroundAcute myeloid leukemia (AML) is characterized by the abnormal proliferation of myeloid precursor cells and presents significant challenges in treatment due to its heterogeneity. Recently, the NLRP3 inflammasome has emerged as a potential contributor to AML pathogenesis, although its precise mechanisms remain poorly understood.MethodsPublic genome datasets were utilized to evaluate the expression of NLRP3 inflammasome-related genes (IL-1β, IL-18, ASC, and NLRP3) in AML patients compared to healthy individuals. CRISPR/Cas9 technology was employed to generate NLRP3-deficient MOLM-13 AML cells, followed by comprehensive characterization using real-time PCR, western blotting, FACS analysis, and transmission electron and immunofluorescence microscopy. Proteomic analyses were conducted to identify NLRP3-dependent alterations in protein levels, with a focus on the eIF2 kinase PERK-mediated signaling pathways. Additionally, in vivo studies were performed using a leukemic mouse model to elucidate the pathogenic role of NLRP3 in AML.ResultsElevated expression of NLRP3 was significantly associated with diminished overall survival in AML patients. Genetic deletion, pharmacological inhibition and silencing by RNA interference of NLRP3 led to decreased AML cell survival through the induction of apoptosis. Proteomic analyses uncovered NLRP3-dependent alterations in protein translation, characterized by enhanced eIF2α phosphorylation in NLRP3-deficient AML cells. Moreover, inhibition of PERK-mediated eIF2α phosphorylation reduced apoptosis by downregulating pro-apoptotic Bcl-2 family members. In vivo studies demonstrated reduced leukemic burden in mice engrafted with NLRP3 knockout AML cells, as evidenced by alleviated leukemic symptoms.ConclusionOur findings elucidate the involvement of the NLRP3/PERK/eIF2 axis as a novel driver of AML cell survival. Targeting NLRP3-induced signaling pathways, particularly through the PERK/eIF2 axis, presents a promising therapeutic strategy for AML intervention. These insights into the role of the NLRP3 inflammasome offer potential avenues for improving the prognosis and treatment outcomes of AML patients.

ICOS-expressing Regulatory T Cells Influence the Composition of Antitumor CTL Populations.

The role of ICOS in antitumor T cell responses and overall tumor progression has been controversial. In this study, we compared tumor progression in mice lacking ICOS selectively in regulatory T (Treg) cells or in all T cells. Using an experimental melanoma lung metastasis model, we found that Treg cell-specific ICOS knockout reduces the overall tumor burden compared with Cre control mice, with increased CD4+-to-Treg cell and CD8+-to-Treg cell ratios in the tumor. In contrast, there was no difference in the tumor burden in mice lacking ICOS in all of the T cell compartments. This suggests a dual role of ICOS costimulation in promoting protumor and antitumor T cell responses. Consistent with reduced tumor burden, we found that Treg cell-specific deletion of ICOS leads to an increase of CD8+ CTLs that express high levels of granzyme B and perforin. Moreover, single-cell transcriptome analysis revealed an increase of Ly108+Eomeshi CD8+ T cells at the cost of the Ly108+T-bethi subset in Treg cell-specific knockout mice. These results suggest that ICOS-expressing Treg cells suppress the CTL maturation process at the level of Eomes upregulation, a critical step known to drive perforin expression and cytotoxicity. Collectively, our data imply that cancer immunotherapies using ICOS agonist Abs may work better in Treg cell-low tumors or when they are combined with regimens that deplete tumor-infiltrating Treg cells.

Berberine Protects against Hepatocellular Carcinoma Progression by Regulating Intrahepatic T Cell Heterogeneity.

Accumulating evidence suggests that berberine (BBR) exhibits anti-cancer effects in hepatocellular carcinoma (HCC). However, the mechanisms by which BBR regulates the immunological microenvironment in HCC has not been fully elucidated. In this study, a mouse model of orthotopic HCC is established and treated with varying doses of BBR. BBR showed effectiveness in reducing tumor burden in mice with HCC. Cytometry by time-of-flight depicted the alterations in the tumor immune landscape following BBR treatment, revealing the enhancement in the T lymphocytes effector function. In particular, BBR decreased the proportion of TCRbhiPD-1hiCD69+CD27+ effector CD8+ T lymphocytes and increased the proportion of Ly6ChiTCRb+CD69+CD27+CD62L+ central memory CD8+ T lymphocytes. Single-cell RNA sequencing further elucidates the effects of BBR on transcriptional profiles of liver immune cells and confirms the phenotypical heterogeneity of T lymphocytes in HCC immune microenvironment. Additionally, it is found that BBR potentially regulated the antitumor immunity in HCC by modulating the receptor-ligand interaction among immune cells mediated by cytokines. In summary, the findings improve the understanding of BBR's impact on protecting against HCC, emphasizing BBR's role in regulating intrahepatic T cell heterogeneity. BBR has the potential to be a promising therapeutic strategy to hinder the advancement of HCC.

RNA interactome of hypervirulent Klebsiella pneumoniae reveals a small RNA inhibitor of capsular mucoviscosity and virulence

Hypervirulent Klebsiella pneumoniae (HvKP) is an emerging bacterial pathogen causing invasive infection in immune-competent humans. The hypervirulence is strongly linked to the overproduction of hypermucoviscous capsule, but the underlying regulatory mechanisms of hypermucoviscosity (HMV) have been elusive, especially at the post-transcriptional level mediated by small noncoding RNAs (sRNAs). Using a recently developed RNA interactome profiling approach iRIL-seq, we interrogate the Hfq-associated sRNA regulatory network and establish an intracellular RNA-RNA interactome in HvKP. Our data reveal numerous interactions between sRNAs and HMV-related mRNAs, and identify a plethora of sRNAs that repress or promote HMV. One of the strongest HMV repressors is ArcZ, which is activated by the catabolite regulator CRP and targets many HMV-related genes including mlaA and fbp. We discover that MlaA and its function in phospholipid transport is crucial for capsule retention and HMV, inactivation of which abolishes Klebsiella virulence in mice. ArcZ overexpression drastically reduces bacterial burden in mice and reduces HMV in multiple hypervirulent and carbapenem-resistant clinical isolates, indicating ArcZ is a potent RNA inhibitor of bacterial pneumonia with therapeutic potential. Our work unravels a novel CRP-ArcZ-MlaA regulatory circuit of HMV and provides mechanistic insights into the posttranscriptional virulence control in a superbug of global concern.

Discovery of D8-03 as an Inhibitor of Intracellular Growth of Francisella tularensis.

Francisella tularensis is a Gram-negative facultative intracellular bacterial pathogen that is classified by the Centers for Disease Control and Prevention as a Tier 1 Select Agent. F. tularensis infection causes the disease tularemia, also known as rabbit fever. Treatment of tularemia is limited to few effective antibiotics which are associated with high relapse rates, toxicity, and potential emergence of antibiotic-resistant strains. Consequently, new therapeutic options for tularemia are needed. Through screening a focused chemical library and subsequent structure-activity relationship studies, we have discovered a new and potent inhibitor of intracellular growth of Francisella tularensis, D8-03. Importantly, D8-03 effectively reduces bacterial burden in mice infected with F. tularensis. Preliminary mechanistic investigations suggest that D8-03 works through a potentially novel host-dependent mechanism and serves as a promising lead compound for further development.

Abstract Tu141: Effect of Epicardial Application of Oxygenated Hydrogel on Scar Burden in a Rat Model of Myocardial Infarction

Background: Epicardial application of a bioadhesive at the time of experimental myocardial infarction (MI) has been shown to reduce ventricular scar burden in mice. This study assessed the impact of an oxygenated hydrogel (O 2 -hydrogel) on post-infarct cardiac function and scar burden in rats. Method: Experimental MI was performed in Lewis rats (age 12-15 weeks) by permanent ligation of the anterior interventricular artery. There were 3 cohorts in this study: 1. MI followed by epicardial application of hydrogel, 2. MI followed by epicardial application of O 2 -hydrogel, and 3. MI with no treatment. Left ventricular (LV) function was evaluated by transthoracic echocardiography (TTE) at baseline, immediately post-MI, and 3 weeks post-MI. LV scar burden was evaluated with histopathology performed 3 weeks post-MI. Result: Twenty-four rats were analyzed (hydrogel, n= 8; O 2 -hydrogel, n= 9; untreated, n=7). LV fractional shortening (FS) measured by TTE 3 weeks post-MI was significantly reduced compared with baseline in untreated rats (44.6±12.4 to 22.3±4.9, P=0.043; Figure 1) and hydrogel treated rats (32.4±6.0 to 14.9±5.2, P=0.018). No significant change in FS was observed in the O 2 -hydrogel treatment cohort (39.0±13.9 to 38.1±12.6, P=0.859). LV scar burden in the O 2 -hydrogel cohort was significantly lower than in the hydrogel alone and untreated cohorts (11.9% vs 39.9% and 36.2%, respectively; Figure 2). Conclusion: In this rat model, epicardial application of O 2 -hydrogel at the time of experimental MI is associated with greater preservation of LV function and significantly lower scar burden than application of hydrogel alone or no treatment.

Human-specific elimination of epithelial Siglec-XII suppresses the risk of inflammation-driven colorectal cancers.

Carcinomas are common in humans but rare among closely related "great apes." Plausible explanations, including human-specific genomic alterations affecting the biology of sialic acids, are proposed, but causality remains unproven. Here, an integrated evolutionary genetics-phenome-transcriptome approach studied the role of SIGLEC12 gene (encoding Siglec-XII) in epithelial transformation and cancer. Exogenous expression of the protein in cell lines and genetically engineered mice recapitulated approximately 30% of the human population in whom the protein is expressed in a form that cannot bind ligand because of a fixed, homozygous, human-universal missense mutation. Siglec-XII-null cells/mice recapitulated the remaining approximately 70% of the human population in whom an additional polymorphic frameshift mutation eliminates the entire protein. Siglec-XII expression drove several pro-oncogenic phenotypes in cell lines and increased tumor burden in mice challenged with chemical carcinogen and inflammation. Transcriptomic studies yielded a 29-gene signature of Siglec-XII-positive disease and when used as a computational tool for navigating human data sets, pinpointed with surprising precision that SIGLEC12 expression (model) recapitulates a very specific type of colorectal carcinomas (disease) that is associated with mismatch-repair defects and inflammation, disproportionately affects European Americans, and carries a favorable prognosis. They revealed a hitherto-unknown evolutionary genetic mechanism for an ethnic/environmental predisposition of carcinogenesis.

Cytochrome oxidase requirements in Bordetella reveal insights into evolution towards life in the mammalian respiratory tract.

Little is known about oxygen utilization during infection by bacterial respiratory pathogens. The classical Bordetella species, including B. pertussis, the causal agent of human whooping cough, and B. bronchiseptica, which infects nearly all mammals, are obligate aerobes that use only oxygen as the terminal electron acceptor for electron transport-coupled oxidative phosphorylation. B. bronchiseptica, which occupies many niches, has eight distinct cytochrome oxidase-encoding loci, while B. pertussis, which evolved from a B. bronchiseptica-like ancestor but now survives exclusively in and between human respiratory tracts, has only three functional cytochrome oxidase-encoding loci: cydAB1, ctaCDFGE1, and cyoABCD1. To test the hypothesis that the three cytochrome oxidases encoded within the B. pertussis genome represent the minimum number and class of cytochrome oxidase required for respiratory infection, we compared B. bronchiseptica strains lacking one or more of the eight possible cytochrome oxidases in vitro and in vivo. No individual cytochrome oxidase was required for growth in ambient air, and all three of the cytochrome oxidases conserved in B. pertussis were sufficient for growth in ambient air and low oxygen. Using a high-dose, large-volume persistence model and a low-dose, small-volume establishment of infection model, we found that B. bronchiseptica producing only the three B. pertussis-conserved cytochrome oxidases was indistinguishable from the wild-type strain for infection. We also determined that CyoABCD1 is sufficient to cause the same level of bacterial burden in mice as the wild-type strain and is thus the primary cytochrome oxidase required for murine infection, and that CydAB1 and CtaCDFGE1 fulfill auxiliary roles or are important for aspects of infection we have not assessed, such as transmission. Our results shed light on the environment at the surface of the ciliated epithelium, respiration requirements for bacteria that colonize the respiratory tract, and the evolution of virulence in bacterial pathogens.

Amphotericin B resistance in Leishmania amazonensis: In vitro and in vivo characterization of a Brazilian clinical isolate.

In Brazil, Leishmania amazonensis is the etiological agent of cutaneous and diffuse cutaneous leishmaniasis. The state of Maranhão in the Northeast of Brazil is prevalent for these clinical forms of the disease and also has high rates of HIV infection. Here, we characterized the drug susceptibility of a L. amazonensis clinical isolate from a 46-year-old man with diffuse cutaneous leishmaniasis coinfected with HIV from this endemic area. This patient underwent several therapeutic regimens with meglumine antimoniate, liposomal amphotericin B, and pentamidine, without success. In vitro susceptibility assays against promastigotes and intracellular amastigotes demonstrated that this isolate had low susceptibility to amphotericin B, when compared with the reference strain of this species that is considered susceptible to antileishmanial drugs. Additionally, we investigated whether the low in vitro susceptibility would affect the in vivo response to amphotericin B treatment. The drug was effective in reducing the lesion size and parasite burden in mice infected with the reference strain, whereas those infected with the clinical isolate and a resistant line (generated experimentally by stepwise selection) were refractory to amphotericin B treatment. To evaluate whether the isolate was intrinsically resistant to amphotericin B in animals, infected mice were treated with other drugs that had not been used in the treatment of the patient (miltefosine, paromomycin, and a combination of both). Our findings demonstrated that all drug schemes were able to reduce lesion size and parasite burden in animals infected with the clinical isolate, confirming the amphotericin B-resistance phenotype. These findings indicate that the treatment failure observed in the patient may be associated with amphotericin B resistance, and demonstrate the potential emergence of amphotericin B-resistant L. amazonensis isolates in an area of Brazil endemic for cutaneous leishmaniasis.

Abstract PO2-25-06: A hybrid breast cancer/mesenchymal stem cell population increases distant metastasis and chemoresistance of metaplastic breast carcinomas

Abstract Background: Metaplastic breast carcinoma is a heterogenous, highly aggressive and chemoresistant subtype of triple negative breast cancer (TNBC) with histological evidence of deregulated differentiation towards non-glandular components including spindle, squamous, and sarcomatoid. The role of the tumor microenvironment in the metastatic behavior and chemotherapy response of metaplastic carcinomas needs investigation to improve patient outcomes. Our lab has generated a model of spindle metaplastic breast carcinomas based on mammary epithelial cell-specific CCN6 knockout (MMTV-Cre;Ccn6fl/fl or CCN6KO). We have recently shown that a subset of TNBC cells engulf mesenchymal stem/stromal cells (MSC) generating a hybrid cell population with metastatic ability, which is detected in breast cancer tissue samples. In this study, we tested the hypothesis that hybrid cells may promote chemoresistant distant metastasis in spindle metaplastic breast carcinomas and that the tumor immune microenvironment may play a role in this function. Methods: Luc-GFP-CCN6KO cells were cultured with DsRED-MSCs for 7 days, yielding >90% of hybrid cells detected by flow cytometry. Hybrids or CCN6KO single cultures (1x10(5) cells) were injected intracardially in FVB/NJ syngeneic immune competent mice (n=20 mice per group). Four days after injection, each group was treated with Paclitaxel (PTX, 10 mg/kg twice a week, i.p.) or PBS control. The metastatic burden was evaluated by bioluminescence imaging twice a week. Mice were euthanized 23 days after heart injections, followed by necropsy and histopathological evaluation of the harvested organs. Results: All mice injected with single cultures of CCN6KO cells or hybrid cells formed distant metastasis. CCN6KO cells were highly invasive and spread to the lungs and lymph nodes in the chest,. We noted that 5 of 20 (25%) mice injected with hybrid cells showed metastasis in the liver (n=3 mice), pancreas (n=1), and abdominal lymph nodes (n=1). PTX treatment significantly reduced metastatic burden in mice injected with CCN6KO single cultures compared to vehicle (p=0.035) but had no effect on the metastatic burden of hybrid cells. Histologically, while the metastasis from CCN6KO cells and hybrids showed similar pathological features, consisting of spindle cancer cells with high grade nuclei and >10 mitoses/10 high power fields, hybrid-derived tumors had abundant infiltration by immune cells, mainly neutrophils, compared to single culture tumors. Conclusion: Our data show that hybrid cancer cell/MSC derived from CCN6KO spindle metaplastic carcinomas have higher ability to disseminate to distant organs, especially in the abdomen, compared to cancer cells. Our data show that hybrid cell-derived metastases have increased immune cell infiltration. We provide evidence that hybrid cells enhance Paclitaxel resistance in a mouse model of metaplastic breast carcinoma. Ongoing studies are aimed at elucidating the role of hybrids in the immune microenvironment of metaplastic breast carcinoma and clinical significance. Citation Format: Ahmad Eido, Maria Gonzalez, Celina Kleer. A hybrid breast cancer/mesenchymal stem cell population increases distant metastasis and chemoresistance of metaplastic breast carcinomas [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-25-06.

Abstract PO3-18-07: Therapeutic Potential of Combining Eltanexor with Tamoxifen to Treat Primary and Metastatic Estrogen Receptor Positive (ER+) Breast Cancers

Abstract Estrogen receptors are key pathway initiators in the aggressive development of more than two-thirds of all breast cancers. Tamoxifen (TAM) is a selective estrogen receptor modulator that disables the ER pathway and inhibits the progression of ER+ breast cancer. Unfortunately, 10-40% of patients with ER+ breast cancer who were treated with TAM experience recurrence and metastasis within 10 years. We have previously identified exportin 1 (XPO1) to be more highly expressed in breast cancers with acquired TAM resistance compared to TAM-sensitive counterparts and showed that a combination treatment of TAM with an XPO1 inhibitor, selinexor, is an effective method of tumor suppression in preclinical models. In this study we investigated the activity of eltanexor, an investigational second generation XPO1 inhibitor with minimal penetration of the blood-brain barrier, to inhibit cancer growth without leading to weight loss. Our results show that mice harboring MCF7-ESR1Y537Sxenograft tumors had significantly less (P < .05) flank tumor growth when administered a treatment regimen of TAM and eltanexor compared to control mice. In metastatic tumor models, we observed decreased metastatic burden in mice harboring MCF7-ESR1 D538G and MCF7-ESR1Y537S tumors when co-administered TAM and eltanexor. We did not observe weight changes in either model. Our findings suggest that eltanexor may be a relevant treatment for further exploration in the context of a TAM combination therapy for treatment of ER+ breast cancer. Citation Format: Vedant Jain, Myra Kamdar, Hannah McGee, Qianying Zuo, Jin Young Yoo, Yosef Landesman, Christopher Walker, Zeynep Madak-Erdogan. Therapeutic Potential of Combining Eltanexor with Tamoxifen to Treat Primary and Metastatic Estrogen Receptor Positive (ER+) Breast Cancers [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-18-07.

Efficacy of an oral lipid nanocrystal formulation of amphotericin B (MAT2203) in the neutropenic mouse model of pulmonary mucormycosis.

Invasive mucormycosis (IM) is associated with high mortality and morbidity. MAT2203 is an orally administered lipid nanocrystal formulation of amphotericin B, which has been shown to be safe and effective against other fungal infections. We sought to compare the efficacy of MAT2203 to liposomal amphotericin B (LAMB) treatment in a neutropenic mouse model of IM due to Rhizopus arrhizus var. delemar or Mucor circinelloides f. jenssenii DI15-131. In R. arrhizus var. delemar-infected mice, 15 mg/kg of MAT2203 qd was as effective as 10 mg/kg of LAMB in prolonging median survival time vs placebo (13.5 and 16.5 days for MAT2203 and LAMB, respectively, vs 9 days for placebo) and enhancing overall survival vs placebo-treated mice (40% and 45% for MAT2203 and LAMB, respectively, vs 0% for placebo). A higher dose of 45 mg/kg of MAT2203 was not well tolerated by mice and showed no benefit over placebo. Similar results were obtained with mice infected with M. circinelloides. Furthermore, while both MAT2203 and LAMB treatment resulted in a significant reduction of ~1.0-2.0log and ~2.0-2.5log in Rhizopus delemar or M. circinelloides lung and brain burden vs placebo mice, respectively, LAMB significantly reduced tissue fungal burden in mice infected with R. delemar vs tissues of mice treated with MAT2203. These results support continued investigation and development of MAT2203 as a novel and oral formulation of amphotericin for the treatment of mucormycosis.

The feasibility of K XRF bone lead measurements in mice assessed using 3D-printed phantoms

This article describes the development of a system for in vivo measurements of lead body burden in mice using 109Cd K x-ray fluorescence (XRF). This K XRF system could facilitate early-stage studies on interventions that ameliorate or reverse organ tissue damage from lead poisoning by reducing animal numbers through a cross-sectional study approach. A novel mouse phantom was developed based on a mouse atlas and 3D-printed using PLA plastic with plaster of Paris ’bone’ inserts. PLA plastic was found to be a good surrogate for soft tissue in XRF measurements and the phantoms were found to be good models of mice. As expected, lead detection limits varied with mouse size, mouse orientation, and mouse position with respect to the source and detector. The work suggests that detection limits of 10 to 20 μg Pb per g bone mineral may be possible for a 2 to 3 hour XRF measurement in a single animal, an adequate limit for some pre-clinical studies. The 109Cd K XRF mouse measurement system was also modeled using the Monte Carlo code MCNP. The combination of experiment and modeling found that contrary to expectation, accurate measurements of lead levels in mice required calibration using mouse-specific calibration standards due to the coherent scatter peak normalization failing when small animals are measured. MCNP modeling determined that this was because the coherent scatter signal from soft tissue, which until now has been assumed negligible, becomes significant when compared to the coherent scatter signal in bone in small animals. This may have implications for some human measurements. This work suggests that 109Cd K x-ray fluorescence measurements of lead body burden are precise enough to make the system feasible for small animals if appropriately calibrated. Further work to validate the technology’s measurement accuracy and performance in vivo will be required.

Proteomics reveals that the antifungal activity of fenbendazole against Cryptococcus neoformans requires protein kinases

Cryptococcus neoformans is responsible for over 100 000 deaths annually, and the treatment of this fungal disease is expensive and not consistently effective. Unveiling new therapeutic avenues is crucial. Previous studies have suggested that the anthelmintic drug fenbendazole is an affordable and nontoxic candidate to combat cryptococcosis. However, its mechanism of anticryptococcal activity has been only superficially investigated. In this study, we examined the global cellular response of C. neoformans to fenbendazole using a proteomic approach (data are available via ProteomeXchange with identifier PXD047041). Fenbendazole treatment mostly impacted the abundance of proteins related to metabolic pathways, RNA processing, and intracellular traffic. Protein kinases, in particular, were significantly affected by fenbendazole treatment. Experimental validation of the proteomics data using a collection of C. neoformans mutants led to the identification of critical roles of five protein kinases in fenbendazole's antifungal activity. In fact, mutants lacking the expression of genes encoding Chk1, Tco2, Tco3, Bub1, and Sch9 kinases demonstrated greater resistance to fenbendazole compared to wild-type cells. In combination with the standard antifungal drug amphotericin B, fenbendazole reduced the cryptococcal burden in mice. These findings not only contribute to the elucidation of fenbendazole's mode of action but also support its use in combination therapy with amphotericin B. In conclusion, our data suggest that fenbendazole holds promise for further development as an anticryptococcal agent.

Abstract 6739: Efficacy and toxicity of microbial mimetic mesoporous silica nanoparticles in a mouse model of ovarian cancer

Abstract Ovarian cancer is predominately left undetected and untreated until the later stages of the disease where it becomes incredibly difficult to treat. Preclinical studies demonstrate that immunotherapy can be highly effective. Our lab has been working on an immunotherapy approach to treat women with ovarian cancer that utilizes mesoporous silica nanoparticles(MSN). MSN that present pathogen-associated molecular patterns (PAMPS) are able to significantly reduce tumor burden in mouse models of serous epithelial ovarian cancer when administered by intraperitoneal injection. These microbial mimetic particles are decorated with polyethyleneimine (PEI), CpG oligonucleotide, and monophosphoryl lipid A (MPLA). When in the presence of antigen presenting cells, they bind to Toll-like receptors (TLR) present on the cell surface and within the endosome. To better understand mechanisms underlying their efficacy, we injected fluorescent MSN-PEI-CpG-MPLA (100 or 500 nm) or unmodified MSN into mice with advanced ovarian cancer. The particles, regardless of the presence of TLR-agonists, were rapidly internalized by myeloid cells, with trafficking almost exclusively to immune clusters located in tumor-burdened adipose tissues when administered by intraperitoneal injection. Conversely, intravenous injection of MSN-PEI-CpG-MPLA led to predominate accumulation in liver, with no particles found in tertiary lymphoid clusters 24 hours post injection. Furthermore, unlike intraperitoneal injection, intravenous injection of MSN-PEI-CpG-MPLA was without therapeutic effect. Currently we are studying MSN safety and the impact of administration route and dose on efficacy and cytotoxicity. In summary, MSN, with and without TLR agonists, are trafficked by myeloid cells to tumor-burdened fat-associated lymphoid clusters when administered by intraperitoneal injection. Intraperitoneal injection of TLR-agonist modified MSN effectively reduces tumor burden in mice with ovarian cancer. Citation Format: Lorel Y. Medina, Rita E. Serda, Benjamin Marwedel, Melanie S. Jun, Josh Adogola. Efficacy and toxicity of microbial mimetic mesoporous silica nanoparticles in a mouse model of 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 6739.

Abstract 6320: CAR-T cells targeting LGR5: An effective treatment for chemotherapy resistant ovarian cancer

Abstract Ovarian cancer is the second leading cause of cancer-related mortality among gynaecological cancers in the Western world. CAR-T cell therapy is an adoptive immunotherapy used to treat some blood cancers. This study has investigated whether leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5) is a suitable target for CAR-T cell therapy for ovarian cancer. We assessed the cytotoxic effects of LGR5-targeting CAR-T cells on a range of ovarian cancer cell lines and primary serous ovarian cancer cells derived from patient ascites (at diagnosis and following relapse with chemotherapy resistant disease) in monolayer culture, 3D spheroid assays and patient-derived explant assays. OVCAR3 and a chemoresistant patient-derived xenograft (PDX) models have been used to assess whether LGR5-targeting CAR-T cells can inhibit growth and metastasis in vivo. We found that LGR5 is highly expressed in high-grade serous ovarian carcinoma (HGSOC) cancer cell lines and LGR5 expression was increased in chemotherapy resistant primary ovarian cancer cells. We demonstrated that LGR5-targeting CAR-T cells were cytotoxic and significantly inhibited the survival of ovarian cancer cell lines and chemotherapy-resistant primary ovarian cancer cells with high LGR5 expression levels in both monolayer culture and 3D spheroids compared to un-transduced CD3+ T cells. In patient-derived explant assays, we observed increased apoptosis in HGSOC tissues expressing high LGR5 following treatment with LGR5-targeting CAR-T cells. In vivo, LGR5-targeting CAR-T cell treatment decreased the tumour burden in mice with OVCAR3 xenografts and a chemotherapy-resistant PDX model with high LGR5 expression, compared to CD3+ T cells. In summary, LGR5-targeting CAR-T cells have great potential to be developed as a novel immunotherapy for ovarian cancer. Citation Format: Wanqi (Jady) Wang, Veronika Bandara, Noor A. Lokman, Zoe K K. Price, Tannith M. Noye, Silvana Napoli, Batjargal Gundsambuu, Martin K. Oehler, Simon C. Barry, Carmela Ricciardelli. CAR-T cells targeting LGR5: An effective treatment for chemotherapy resistant 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 6320.

Abstract 2104: Targeting stem cell proteostasis pathways sensitizes acute myeloid leukemia to proteasome inhibitors

Abstract Proteasome inhibitors are highly effective for treating multiple myeloma, but exhibit little efficacy in other blood cancers. In this study, we set out to determine why acute myeloid leukemia (AML) is largely refractory to proteasome inhibition and if we could sensitize human AML to this class of drugs. Efficacy of proteasome inhibitors in myeloma partly depends on disruption of protein homeostasis (proteostasis). This is driven by an accumulation of misfolded proteins that activate the unfolded protein response (UPR) and integrated stress response (ISR). Due to their highly secretory nature, myeloma cells exhibit relatively elevated baseline endoplasmic reticulum stress, and are thus sensitive to proteasome inhibition as they readily activate a terminal UPR. However, we found that proteasome inhibition fails to significantly disrupt proteostasis in human AML cells. We recently discovered that hematopoietic stem cells utilize distinct pathways to regulate proteostasis, and we hypothesized that AML cells co-opt stem cell proteostasis pathways to cope with proteasome inhibition and preserve proteostasis. To test this, we first performed RNA-sequencing which revealed that AML cells respond to proteasome inhibition by activating two distinct proteostasis pathways normally utilized by hematopoietic stem cells: autophagy and the heat shock response. Concurrent proteasome and autophagy inhibition significantly increased unfolded protein content in multiple human AML cell lines. This proteostasis disruption was sufficient to induce a terminal ISR marked by activation of the eIF2α-ATF4-CHOP signaling axis that severely attenuated protein synthesis, reduced proliferation, and induced widespread apoptosis in human AML cell lines and primary AML patient samples. In contrast to AML cells, dual proteasome and autophagy inhibition was well tolerated by healthy human CD34+ hematopoietic stem and progenitor cells, suggesting a tractable therapeutic window for treating AML. Indeed, dual proteasome and autophagy inhibition was tolerated in vivo, and decreased leukemia burden in mice xenografted with human AML cell lines. Similar to autophagy inhibition, disabling the heat shock response by deleting Heat shock factor 1 (HSF1) sensitized human AML cell lines to proteasome inhibitors. Treatment of HSF1-deficient AML cells with a proteasome inhibitior induced a significant increase in unfolded protein, activated the ISR, reduced growth and protein synthesis, and led to severe apoptosis. Concurrent HSF1 deletion and proteasome inhibition dramatically reduced AML disease burden in vivo and extended median survival from 40 to 140 days. Overall, this study revealed that AML cells hijack stem cell proteostasis pathways to promote growth, survival, and therapeutic resistance. Targeting the unique configuration of the proteostasis network is uncovering new therapeutic strategies to eliminate AML. Citation Format: Kentson Lam, Yoon Joon Kim, Carlo M. Ong, Fanny J. Zhou, Andrea Z. Liu, Bernadette A. Chua, Jie-Hua Zhou, Edward D. Ball, Robert A. Signer. Targeting stem cell proteostasis pathways sensitizes acute myeloid leukemia 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 2104.

Abstract 1227: Novel combination therapies to overcome non-genetic/adaptive menin inhibitor resistance in AML with MLL1r or mtNPM1

Abstract In AML with MLL1 rearrangement or MLL1 fusion proteins (FP), the N-terminus of MLL1 becomes fused to over 80 partner proteins resulting in an aberrant leukemic transcriptional program including dysregulated expression of HOXA9, MEIS1, PBX3, FLT3, MEF2C and CDK6. On the other hand, in mutant NPM1 AML cells, wild type MLL1 is the main regulator of HOXA9, MEIS1 and FLT3, promoting self-renewal of myeloid progenitor cells. Menin inhibitors have been developed that disrupt the binding of Menin to MLL1 leading to reduced activity of HOXA9 and MEIS1 and repression of MLL1 or MLL1-FP target genes. Clinical trials have demonstrated that Menin inhibitors (MI) are well-tolerated and clinical remissions have been observed in patients with relapsed/refractory AML harboring MLLr. Unfortunately, most patients either fail to respond or eventually relapse. MI-resistance in AML with MLL1r or mtNPM1 is either due to recently described mutations in the MI-binding domain of Menin or is non-genetic/adaptive, due to dysregulated epigenome/transcriptome/proteome. In the present studies, through repeated shocks with LD90 dosing of MI, followed by drug washout and recovery, we have generated MLL1r (MV4-11-MITR) and mtNPM1 (OCI-AML3-MITR) AML cell lines that are tolerant/resistant (TR) to MI with LD50 values greater than 1 μM. Whole exome sequencing confirmed that these cells were lacking in new driver mutations. We determined that resistance in the MITR cells was not due to presence of hotspot mutations in Menin. ChIP-Seq analysis of H3K27Ac showed that the activities of super enhancers and core transcriptional regulatory circuitry was altered in both MITR cell types. Non-genetic/adaptive resistance to MI also concordantly reduced genome wide ATAC-Seq and RNA-Seq peaks in the OCI-AML3-MITR cells with significant depletion of MEIS1, IGF2BP2, BCL2, and PBX3, with concomitant induction of leukemia stem cell associated CLEC12A and CD244 expressions. A domain-specific CRISPR screen in MV4-11-MITR cells identified several druggable co-dependencies (e.g. EP300 and MOZ) and co-enrichments (SMARCA4, CREBBP and BRD4) with MI, suggesting them as potential mechanisms of non-genetic/adaptive MI resistance. Consistent with these findings, co-treatment with SMARCA2/SMARCA4 (chromatin remodeler ATPases) inhibitor FHD-286 and the BETi OTX015 or the MI SNDX-50469 exerted synergistic lethality in MV4-11-MITR and OCI-AML3-MITR cells as well as in PD MITR AML cells with MLL1r or mtNPM1. Co-treatment with CBP/p300 inhibitor GNE049 or GNE781 was also synergistic with MI in these cells. In vivo treatment with FHD-286 and OTX015 or SNDX-5613 significantly reduced the AML burden in mice bearing OCI-AML3-MITR xenografts. These findings underscore preclinical activity of epigenetically-targeted agent-based combinations and highlight their promise in overcoming MI resistance in AML with MLL1r or mtNPM1. Citation Format: Warren C. Fiskus, Christopher P. Mill, Jessica Piel, Murphy Hentemann, Christine E. Birdwell, Kaberi Das, John A. Davis, Hanxi Hou, Tapan M. Kadia, Naval Daver, Sanam Loghavi, Branko Cuglievan, Courtney D. DiNArdo, Kapil N. Bhalla. Novel combination therapies to overcome non-genetic/adaptive menin inhibitor resistance in AML with MLL1r or mtNPM1 [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 1227.

Abstract 2008: The N6-methyladenine-long noncoding RNA axis promotes drug resistance through PI3k signaling in leukemia

Abstract Disease recurrence characterized by drug resistance remains a major hurdle to the successful cancer treatment. Long noncoding RNAs (lncRNAs) and RNA N⁶-methyladenosine (m6A) have been linked to cancer recurrence. However, if and how lncRNAs and m6A coordinately determine drug resistance in tyrosine kinase (TK)-driven cancers are still unclear. We hypothesize that upon exposure to TK inhibitors (TKI), the dynamic m6A methylation epitransciptomically allows a set of proliferation/anti-apoptosis-relevant lncRNAs bearing m6A motifs to be rapidly upregulated, thus facilitating a subpopulation of cancer cells to evade TKI killing. By performing transcriptomic and epitransciptomic profiling in long-term TKI (nilotinib)-deprived leukemia resistant cells, we show that many differentially expressed lncRNAs enrich m6A, and more lncRNAs tend to have higher m6A content in resistant cells. We further demonstrate a broad clinical relevance of our findings, showing that upregulation of specific top-ranked lncRNAs (e.g., SENCR, PROX1-AS1, LN892) in TKI-resistant cell lines also occurs in leukemia patients at the diagnostic stage, blast crisis phase or in those not-responding to TKI treatment compared to chronic phase or TKI responders, respectively. Some of the upregulated lncRNAs in leukemia patients pre- and post-TKI treatment predict unfavorable outcomes and are associated with shorter survival duration. Through proliferative and clonogenic assays, we demonstrate that knockdown of SENCR, PROX1-AS1 or LN892 impairs resistant cell growth and renders resistant cells sensitive to nilotinib-induced cell death. We further found that this lncRNA upregulation is attributed to FTO-dependent m6A hypomethylation that stabilizes lncRNA transcripts. Using ectopic expression or genetic/pharmacological inhibition, we demonstrate that lncRNA upregulation empowers resistant cell growth through an activated PI3K signaling as supported by overexpression of PI3K signaling mediators (e.g., ITGA2, F2R, COL6A1). Treatment with PI3K inhibitor alpelisib sensitizes TKI-resistant cells to TKI-induced cell death and reduces leukemia burden in mice via downregulation of F2R, ITGA2, and COL6A1. In conclusion, our findings add a new layer to the complexity of mechanisms regulating leukemia cell fate under TKI selection and raise the possibility that the m6A-regulated lncRNAs represents a new non-genetic factor to affect the development and maintenance of TKI resistance; our discoveries identify a promising therapeutic target, the m6A-lncRNAs axis, for specifically the most challenging patient subpopulations who are TKI non-responders/relapsed but do not carry the acquired mutations on top of BCR/ABL; our results also uncover a strong predictor, m6A-regulated lncRNA-PI3K axis, for poorer prognosis and failure in drug response which might be a pan-cancer mechanism. Citation Format: Yanhong Tan, Changli Zhou, Sicheng Bian, Wencke Walter, Jiuxia Pang, Tao Cheng, Gang Huang, Gregor Hoermann, William Tse, Shujun Liu. The N6-methyladenine-long noncoding RNA axis promotes drug resistance through PI3k signaling in leukemia [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 2008.