Human Rhabdomyosarcoma Cell Line Research Articles

Combinatorial cellular therapy in pediatric solid tumors with natural killer (NK) and genetically engineered myeloid cells (GEMys).

2561 Background: Early human studies with Natural Killer (NK) cells have shown promise, harnessing their ability to infiltrate into tumors and be tumoricidal. However, these effects can be limited by adenosine, reactive oxygen species, and TGF-β in the highly immune suppressive tumor microenvironment (TME). TGF-β and downstream SMAD3 signaling in Natural Killer (NK) cells have been shown to cause decreased cytokine production, downregulation of activating cell surface receptors, and attenuated cytotoxic function against solid tumors. Exposure to TGF-β during cell culture generates expanded NK cells with increased resistance to TGF-β signaling, dubbed TGF-β imprinted NK cells. In vitrostudies have shown that these cells have increased cytokine production and cytotoxic function in the presence of TGF-β. However, their in vivo trafficking, modulation of the TME, and therapeutic efficacy remain understudied. Our lab has previously shown that when given to tumor-bearing mice, myeloid cells modified to produce IL-12 (IL-12-Genetically Engineered Myeloid cells, aka IL-12 GEMys) are effective at homing to tumor and metastatic sites and, via IL-12 secretion and TME modulation, increase NK cell presence and activation in these sites. They hold great promise as combination therapy, enhancing the effectiveness of other cellular therapies such as NK cell therapy. A current clinical trial exploring TGF-β Imprinted, Ex Vivo Expanded, Universal Donor NK Cell Infusions in relapsed sarcomas is underway (NCT05634369). Methods: In vitro experiments were conducted with the xCELLigence real-time cell analysis system. The human osteosarcoma cell line 143B and human rhabdomyosarcoma cell line RH-30 were evaluated for cell death after co-culture with healthy donor NK cells or TGF-β imprinted NK cells (E:T ratio of 5:1) in isolation and in combination with IL-12 GEMys (E:T ratio of 2:1). Results: TGF-β imprinted NK cells are significantly more effective at tumor cell killing of both 143B and RH30 cell lines in-vitro compared to regular expanded NK cells (WT NK cells), with >90% decrease in cell index compared to 50-60%, respectively, after 48 hours of co-culture. IL-12 GEMys also significantly enhance the cytotoxic effects of WT NK cells, increasing cell killing to 70-80% compared to co-culture with untransduced GEMy controls. Conclusions: These initial in-vitro experiments provide insight into the promising effectiveness of NK-myeloid cell combination therapies in the treatment of pediatric sarcomas. Ongoing in vitroexperiments include cytokine quantification by ELISA and flow cytometric analysis of NK cell activation and proliferation markers. Our preliminary results provide rationale to continue studying the in vivo efficacy of TGF-β imprinted NK cell monotherapy and in combination with IL-12 GEMys in the treatment of tumor-bearing NSG mice.

Acetylated galactopyranosyl N-heterocyclic monocarbene complexes of Silver(I) as novel anti-proliferative agents in a rhabdomyosarcoma cell line

Herein, four silver(I) complexes bearing acetylated d-galactopyranoside-based N-heterocyclic carbene ligands were synthesized and fully characterized by elemental analysis, NMR, and X-ray photoelectron spectroscopy. All complexes were obtained with an anomeric β-configuration and as monocarbene species. In this study, we investigated the biological effects of the silver(I) complexes 2a-d on the human rhabdomyosarcoma cell line, RD. Our results show concentration-dependent effects on cell density, growth inhibition, and activation of key signaling pathways such as Akt 1/2, ERK 1/2, and p38-MAPK, indicating their potential as anticancer agents. Notably, at 35.5 µM, the complexes induced mitochondrial network disruption, as observed with 2b and 2c, whereas with 2a, this disruption was accompanied by nuclear content release. These results provide insight into the utility of carbohydrate incorporated NHC complexes of silver(I) as new agents in cancer therapy.

Fate control engagement augments NK cell responses in LV/hu-IL-12 transduced sarcoma

IntroductionNK cells are an untapped resource for cancer therapy. Sarcomas transduced with lentiviruses to express human IL-12 are only cleared in mice bearing mature human NK cells. However, systemic inflammation limits IL-12 utilization. Fate control a.k.a. “suicide mechanisms” regulate unchecked systemic inflammation caused by cellular immunotherapies. Despite increasing utilization, there remains limited data on immune consequences or tumor-directed effects of fate control. ObjectivesWe sought to engage the mutant thymidylate kinase (mTMPK) metabolic fate control system to regulate systemic inflammation and assess the impact on NK cell effector functions. MethodsPrimary human sarcoma short-passage samples and cell lines were transduced with LV/hu-IL-12_mTMPK engineering expression of IL-12 and an AZT-associated fate control enzyme. We assessed transduced sarcoma responses to AZT engagement and subsequent modulation of NK cell functions as measured by inflammatory cytokine production and cytotoxicity. ResultsAZT administration to transduced (LV/hu-IL-12_mTMPK) short-passage primary human sarcomas and human Ewing sarcoma, osteosarcoma, and rhabdomyosarcoma cell lines, abrogated the robust expression of human IL-12. Fate control activation elicited a specific dose-dependent cytotoxic effect measured by metabolic activity (WST-1) and cell death (Incucyte). NK effector functions of IFN-γ and cytotoxic granule release were significantly augmented despite IL-12 abrogation. This correlated with preferentially induced expression of NK cell activation ligands. ConclusionsmTMPK fate control engagement terminates transduced sarcoma IL-12 production and triggers cell death, but also augments an NK cell-mediated response coinciding with metabolic stress activating surface ligand induction. Fate control engagement could offer a novel immune activation method for NK cell-mediated cancer clearance.

Novel Benzimidazol‐2‐Thione Derivatives: Synthesis, In Vitro Anticancer, Antimicrobial Activities, And In Silico Molecular Docking Study

AbstractA series of derivative benzimidazol‐2‐thione compounds (2 a–2 l) had been synthesized, screened for their antimicrobial activities by dish diffusion and dilution assays, anti‐tumor against breast, rhabdomyosarcoma, and liver human cancer cell lines via MTT assay, followed by carrying out in silico docking model. Entries 2 i–2 j, 2 l, and 2 g are novel compounds, among them, compound 2i manifested the highest antibacterial activity against both Methicillin‐resistant Staphylococcus aureus and Streptococcus faecalis; meanwhile, entries 2 i–2 j and 2 l showed significant antifungal activity toward Trichophyton mentagrophytes, Trichophyton rubrum, and Microsporum gypseum. Through in vitro approach, entry 2 i is the best derivative against human rhabdomyosarcoma cell line. Additionally, via in silico approach, entry 2 i reasonably explained drug delivery ligand against bacterium Streptococcus faecalis, moreover, entries 2 i–2 j and 2 l showed excellent antifungal activity, explained via enzyme inhibition mechanism against 2VF5. In silico, 2 i was proved to inhibit against sarcoma cancer cell line.

Inovo chorioallantoic membrane assay as a xenograft model for pediatric rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is the most common highly malignant pediatric soft tissue sarcoma. While recent multidisciplinary treatments have improved the 5‑year survival rate of low/intermediate‑risk patients to 70‑90%, there are various complications that arise due to treatment‑related toxicities. Immunodeficient mice‑derived xenograft models have been widely used in cancer drug research; however, these models have some limitations, including i)they are time‑consuming and expensive, ii)their use needs to be approved by animal experimental ethics committees, and iii)the inability to visualize where tumor cells or tissues were engrafted. The present study performed a chorioallantoic membrane (CAM) assay in fertilized chicken eggs, which is time‑saving, simple, and easy to standardize and handle because of the high vascularization and the immature immune system of the fertilized eggs. The present study aimed to examine the usability of the CAM assay as a novel therapeutic model for the development of precision medicine for pediatric cancer. A protocol was developed for constructing cell line‑derived xenograft (CDX) models using a CAM assay by transplanting RMS cells on the CAM. It was then examined as to whether these CDX models could be used as therapeutic drug evaluation models using vincristine (VCR) and human RMS cell lines. After grafting and culturing the RMS cell suspension on the CAM, three‑dimensional proliferation over time was observed visually and by comparing volumes. VCR reduced the size of the RMS tumor on the CAM in a dose‑dependent manner. Currently, treatment strategies based on patient‑specific oncogenic backgrounds have not been adequately developed in the field of pediatric cancer. The establishment of a CDX model with the CAM assay may lead to the advancement of precision medicine and help formulate novel therapeutic strategies for intractable pediatric cancer.

Epigallocatechin Gallate Inhibits Cell Growth and Hedgehog Signalling in Human Rhabdomyosarcoma Cell Lines.

Epigallocatechin gallate (EGCG), a major polyphenol of green tea, has been shown to inhibit cancer cell proliferation. In this study the effect of EGCG on cell metabolism and the human hedgehog signalling pathway (HH) in human rhabdomyosarcoma (RMS) cells was investigated. Two human RMS cell lines (RD and RH30) were incubated with EGCG. To evaluate the effects of EGCG on RMS cells, cell viability, colony formation, cell migration, and alteration of genes related to the HH signalling pathway were investigated. EGCG showed cytostatic effects on RMS cells in a dose-dependent manner. Incubation with 25 μM EGCG resulted in a significant reduction of cell migration by 70% and downregulation of the HH pathway transcription factor GLI1. EGCG inhibits RMS cells in vitro by reducing cell proliferation and downregulating the HH signalling pathway. It may therefore be a promising agent in chemoresistant or advanced RMS in children.

Effects of calcitriol on the cell cycle of rhabdomyosarcoma cells

Rhabdomyosarcoma (RMS) is a type of cancer of skeletal muscle. Calcitriol is the active form of vitamin D3, also recognised as a steroid hormone called 1α, 25-dihydroxy vitamin D3 (1,25D). We previously reported that 1,25D promoted cell proliferation and differentiation in non-cancerous skeletal muscle cells C2C12. The aim of this work is to evaluate some of the events triggered by 1,25D in RD cells, a human RMS cell line. In this work we reported that RD cells expressed vitamin D receptor (VDR) and treatment with 1,25D reduced VDR expression at 72 h. At the same time an acute decrease in viable cells as well as in cells in S-phase of cell cycle was also observed. Furthermore, up-regulation of p15INK4b was accompanied in a timely manner by down-regulation of cyclin D3, p21Waf1/Cip1 and myogenin protein levels. Simultaneously, 1,25D induced early apoptosis markers such as cyclin D1 and CDK4, and the disruption of the mitochondrial network together with a redistribution of mitochondria around the nucleus. Finally, 1,25D induced changes in the plasma membrane of RD cells associated with early and late apoptosis at 72 h, as determined by flow cytometry. Taken together, these results determine that treatment with 1,25D for 72 h triggers apoptosis in RD cells.

Non-canonical endogenous expression of voltage-gated sodium channel NaV 1.7subtype by the TE671 rhabdomyosarcoma cell line.

The human TE671 cell line was originally used as a model of medulloblastoma but has since been reassigned as rhabdomyosarcoma. Despite the characterised endogenous expression of voltage‐sensitive sodium currents in these cells, the specific voltage‐gated sodium channel (VGSC) subtype underlying these currents remains unknown. To profile the VGSC subtype in undifferentiated TE671 cells, endpoint and quantitative reverse transcription–PCR (qRT‐PCR), western blot and whole‐cell patch clamp electrophysiology were performed. qRT‐PCR profiling revealed that expression of the SCN9A gene was ∼215‐fold greater than the SCN4A gene and over 400‐fold greater than any of the other VGSC genes, while western blot confirmed that the dominant SCN9A RNA was translated to a protein with a molecular mass of ∼250 kDa. Elicited sodium currents had a mean amplitude of 2.6 ± 0.7 nA with activation and fast inactivation V 50 values of −31.9 ± 1.1 and −69.6 ± 1.0 mV, respectively. The currents were completely and reversibly blocked by tetrodotoxin at concentrations greater than 100 nm (IC50 = 22.3 nm). They were also very susceptible to the NaV1.7 specific blockers Huwentoxin‐IV and Protoxin‐II with IC50 values of 14.6 nm and 0.8 nm, respectively, characteristic of those previously determined for NaV1.7. Combined, the results revealed the non‐canonical and highly dominant expression of NaV1.7 in the human TE671 rhabdomyosarcoma cell line. We show that the TE671 cell line is an easy to maintain and cost‐effective model for the study of NaV1.7, a major target for the development of analgesic drugs and more generally for the study of pain.Key points Undifferentiated TE671 cells produce a voltage‐sensitive sodium current when depolarised.The voltage‐gated sodium channel isoform expressed in undifferentiated TE671 cells was previously unknown. Through qRT‐PCR, western blot and toxin pharmacology, it is shown that undifferentiated TE671 cells dominantly (>99.5%) express the NaV1.7 isoform that is strongly associated with pain. The TE671 cell line is, therefore, a very easy to maintain and cost‐effective model to study NaV1.7‐targeting drugs.

Synthesis, molecular docking, ADMET evaluation and in vitro cytotoxic activity evaluation on RD and L20B cell lines of 3-substituted 5,5-diphenylimidazolidine-2,4-dione derivatives

Hydantoins comprise an important class of compounds which have long attracted attention due to their remarkable biological and pharmacological properties including antitumor and antiviral activities. As a continuation of our studies on hydantoins derivatives we report the successful synthesis of hydantoins derivatives. These synthesized compounds were evaluated for their cytotoxic activity against Vero cells L20B (African green monkey kidney cell line) and Human Rhabdomyosarcoma RD cell lines using methotrexate drug (MTX) as a reference drug in cytotoxic activity studies. The percentage of the cell line viability was carried out by using Trypan blue dye exclusion method. The tested compounds showed equipotent cytotoxicity effect against Vero cells (L20B) and a moderate effect against Human Rhabdomyosarcoma (RD) cell lines. These results exhibited better activity for 4a-b compounds than the reference drug methotrexate (MTX). Molecular docking studies indicated that the synthesized compounds are suitable inhibitors of humain dihydrofolate reductase (DHFR) enzyme, which may explain the high antiproliferative activity. Communicated by Ramaswamy H. Sarma

Down-Regulated miR-130a/b Attenuates Rhabdomyosarcoma Proliferation via PPARG.

Background: Rhabdomyosarcoma (RMS) is one of the most common types of soft-tissue sarcomas in children, and it exhibits a low 5-years survival rate. The survival outcome has shown no significant improvements in the past 30 years miRNA profiling of RMS might therefore provide a novel insight into uncovering new molecular targets for therapy. Methods: We analyzed miRNA and RNA sequencing data from patients and the TARGET database to reveal the potential miRNA-mRNA axes and validated them in patients’ samples. After the miRNA antagomirs were used to silence the target miRNAs in the cell model, qRT-PCR, western immunoblotting analysis, and proliferation assays were performed to explore the interaction between miR-130a/b and peroxisome proliferator-activated receptor gamma (PPARG) and their effects. Results: In RMS patients, the expression of miR-130a/b was augmented, and its related PPARG gene was suppressed. Bioinformatics analysis showed that miR-130a/b targeted the PPARG gene and inhibited the proliferation of human RMS cell lines. In addition, rosiglitazone maleate activated the expression of PPARG in human RMS cell lines to suppress proliferation. Conclusion: miR-130a/b regulates the malignant process in RMS by targeting PPARG. Furthermore, the PPARG agonist rosiglitazone maleate attenuated the proliferation of RD cells and might therefore be of benefit to RMS patients.

Chemical profiling and cytotoxic activity of aqueous extract of Veronica peduncularis M.Bieb.: A chemotaxonomical approach

Background and Aims: Genus Veronica (Plantaginaceae) is represented by 79 species in Turkish flora, 26 of which are endemic. Veronica species have a variety of uses including diuretic, anticancer, and rheumatic pains, wounds, and respiratory problems. According to phytochemical studies, Veronica species contain predominantly iridoid glucosides with some phenylethanoid and flavonoid glycosides. Methods: The aqueous extract of Veronica peduncularis M.Bieb. was tested for its cytotoxic activity on human rhabdomyosarcoma (RD) and human epidermoid carcinoma (HEp-2) cell lines using the MTT method. Chemical profile of the extract was determined by HPLC-DAD, and isolation studies were conducted. Results: The extract was found to show concentration-dependent cytotoxicity against tested cell lines. In addition, a comparison of the iridoid fraction of Veronica peduncularis with previously isolated iridoid glucosides on the HPLC-DAD system, showed the presence of aucubin, amphicoside, veratroyl catalpol, and veronicoside in this fraction. On the other hand, isolation and structure elucidation of plantamajoside and 4'-O-methylisoscutellarein-7-O-2''-O-(6'''-O-acetyl-ß-D-allopyranosyl)- ß-D-glucopyranoside from the phenolic fractions were performed by serial chromatographic and spectroscopic methods. Conclusion: To the best of our knowledge, this is the first cytotoxic activity and phytochemical study on the titled plant. The presence of iridoid glucosides and 8-hydroxyflavone glycosides is important for the chemotaxonomy of the genus Veronica.

Cytotoxic Synergism between a Proprietary Commiphora mukul Gum Extract GU-MCT810, 2-deoxy-D-glucose, and Metformin in Human Alveolar Rhabdomyosarcoma and Hepatoma Cell Lines In vitro

In this investigation we have analyzed the synergism for the cytotoxic effect of a proprietary guggul gum extract (GU), 2-deoxy-D-glucose (2-DG) and metformin (Met) in SJRH30 human alveolar rhabdomyosarcoma and HepG2 hepatoma cell lines in vitro. 2-DG and Met as single agents have weak cytotoxic effects in both cell lines. However, the combination of GU+2-DG, GU+Met and 2-DG+Met showed synergism for cytotoxic effect by CompuSyn analysis. Therefore, GU can be included in the combination of drugs involving 2-DG and Met to have synergistic effect. GU also showed a dose-dependent increase in cellular glucose uptake in HepG2 cells like the antidiabetic drug 2,4-thiozolidine dione (TZ). The demonstration of synergism of anticancer effects between GU, metformin and 2-DG, suggest that their mechanisms are in general complementary, though further studies are required to delineate the mechanism of GU, 2-DG and metformin combinations.

Mechanistic Insight into Apoptotic Induction in Human Rhabdomyosarcoma and Breast Adenocarcinoma Cells by Chnoospora minima: A Sri Lankan Brown Seaweed.

The current study determined the cytotoxic and apoptotic potential of the polyphenol-rich methanol extract of Chnoospora minima (C. minima) and its fractions against human breast adenocarcinoma (MCF-7) and rhabdomyosarcoma (RMS) cells. MTT and neutral red assays were used to determine cytotoxicity. The clonogenic assay evaluated the antineoplastic activity, while the apoptotic activity was determined by cellular morphological changes, caspase 3/7 activity, and DNA fragmentation. Morphological alterations in apoptosis were observed by an inverted phase-contrast microscope and Hoechst 33342 staining methods. The total phenolic, flavonoids, alkaloids, and antioxidant activity in the hexane and chloroform fractions were determined, based on their cytotoxic activity. The hexane fraction of C. minima effectively reduced the cell growth that is concentration-dependent in human RMS and MCF-7 cell lines. It also exhibited low cytotoxicity on Vero cells. The characteristic cellular and nuclear apoptotic morphological features were observed. A noticeable caspase 3/7 activation and the fragmented DNA were detected only in the hexane fraction treated RMS cells, whereas MCF-7 cells showed low caspase 3/7 activation due to a lack of caspase 3 and no evidence of having a typical ladder pattern of apoptosis. Further analysis revealed that the hexane fraction-treated RMS cells upregulated the p53 gene twofold (2.72) compared to the p21 (0.77) gene, whereas in the MCF-7 cells, a 2.21-fold upregulation of p53 was observed compared to the p21 (0.64) gene. The hexane fraction exhibited moderate total phenolics, flavonoids, alkaloids content, and antioxidant activity. According to the different antioxidant mechanisms, hexane and chloroform fractions showed the highest antioxidant activities by FRAP and ORAC assays, respectively. GC-MS analysis of hexane fraction revealed the presence of methyl tetradecanoate (38.314%) as the most abundant compound. The study’s findings highlighted that the non-polar compounds present in the hexane fraction of C. minima suppressed cell proliferation and induced apoptosis-mediated cell death in RMS and MCF-7 cells, mainly via the activation of the p53 gene. Hence, the isolation of compounds is warranted. However, more studies are required to understand the mechanistic insights of these observations.

Bioassay-guided isolation of cytotoxic constituents of Aframomum melegueta K.Schum. seeds

The seeds of Aframomum melegueta are used extensively in the Nigerian ethnomedicine for the management of cancer. This study therefore aimed at isolating and characterizing its cytotoxic constituents. Methanol extract of the seed was obtained through cold maceration, and it was further partitioned into n – hexane, dichloromethane and ethylacetate. The most active fraction was purified on repeated chromatographic techniques, using vacuum liquid chromatography (VLC), column (CC), and high-performance liquid chromatography (HPLC). The extract, purified fractions and isolated compounds were tested for their cytotoxic activities against the human Rhabdomyosarcoma (RD) and breast (MCF-7) cancer cell lines, using MTT assay. The crude extract and n-hexane fraction were found to be selectively cytotoxic to the cancer cell lines. Bioassay-guided fractionation of the n-hexane fraction led to the isolation of three compounds, which were identified as 6-shogaoal, 6-paradol, and 1-dehydro-6-gingerdione. 6-shogaoal demonstrated the highest cytotoxicity with CC50 values of 0.11 ± 0.02 and 0.25 ± 0.05ìg/mL against RD and MCF-7 cell lines respectively, and these were higher in activity when compared with cyclophosphamide (CC50 = 1.98 ± 0.15 and 0.71 ± 0.7ìg/mL). The presented data validates the ethnomedicinal use of A. melegueta in the treatment of cancer and is also indicative of the potential of 6-shogaol as an anticancer agent.

Sarcoma IL-12 overexpression facilitates NK cell immunomodulation

Interleukin-12 (IL-12) is an inflammatory cytokine that has demonstrated efficacy for cancer immunotherapy, but systemic administration has detrimental toxicities. Lentiviral transduction eliciting IL-12-producing human sarcoma for autologous reintroduction provides localized delivery for both innate and adaptive immune response augmentation. Sarcoma cell lines and primary human sarcoma samples were transduced with recombinant lentivirus engineering expression of human IL-12 (hu-IL-12). IL-12 expressing sarcomas were assessed in vitro and in vivo following implantation into humanized NSG and transgenic human IL-15 expressing (NSG.Tg(Hu-IL-15)) murine models. Lentiviral transduction (LV/hu-IL-12) of human osteosarcoma, Ewing sarcoma and rhabdomyosarcoma cell lines, as well as low-passage primary human sarcomas, engendered high-level expression of hu-IL-12. Hu-IL-12 demonstrated functional viability, eliciting specific NK cell-mediated interferon-γ (IFN-γ) release and cytotoxic growth restriction of spheroids in vitro. In orthotopic xenograft murine models, the LV/hu-IL-12 transduced human sarcoma produced detectable IL-12 and elicited an IFN-γ inflammatory immune response specific to mature human NK reconstitution in the NSG.Tg(Hu-IL-15) model while restricting tumor growth. We conclude that LV/hu-IL-12 transduction of sarcoma elicits a specific immune reaction and the humanized NSG.Tg(Hu-IL-15) xenograft, with mature human NK cells, can define in vivo anti-tumor effects and systemic toxicities. IL-12 immunomodulation through autologous tumor transduction and reintroduction merits exploration for sarcoma treatment.

Enhanced photoluminescence of boron nitride quantum dots by encapsulation within polymeric nanoparticles

Boron nitride quantum dots (BNQDs) have been proposed as probes for bioimaging owing their to outstanding photoluminescent properties, although their hydrophobic nature and strong aggregation tendency in aqueous media limit their application in the biomedical field. In this work, we synthesize BNQDs by a liquid exfoliation–solvothermal process under pressure from boron nitride nanoparticles in N,N-dimethylformamide. The BNQDs display an average size of 3.3 ± 0.6 nm, as measured by transmission electron microscopy, and a (100) crystalline structure. In addition, a quantum yield of 21.75 ± 0.20% was achieved. To ensure complete dispersibility in water and prevent possible elimination by renal filtration upon injection, the BNQDs (20% w/w) are encapsulated within poly(ethylene glycol)-b-poly(epsilon-caprolactone) nanoparticles by a simple and scalable nanoprecipitation method, and hybrid nanocomposite particles with significantly stronger photoluminescence than their free counterparts are produced. Finally, their optimal cell compatibility and bioimaging features are demonstrated in vitro in murine macrophage and human rhabdomyosarcoma cell lines.

A Fusion Transcription Factor-Driven Cancer Progresses to a Fusion-Independent Relapse via Constitutive Activation of a Downstream Transcriptional Target.

Targeted monotherapies usually fail due to development of resistance by a subgroup of cells that evolve into recurrent tumors. Alveolar rhabdomyosarcoma is an aggressive myogenic soft-tissue cancer that is associated with a characteristic PAX3-FOXO1 gene fusion encoding a novel fusion transcription factor. In our myoblast model of PAX3-FOXO1-induced rhabdomyosarcoma, deinduction of PAX3-FOXO1 simulates a targeted therapy that antagonizes the fusion oncoprotein. This simulated therapy results initially in regression of the primary tumors, but PAX3-FOXO1-independent recurrent tumors eventually form after a delay. We report here that upregulation of FGF8, a direct transcriptional target of PAX3-FOXO1, is a mechanism responsible for PAX3-FOXO1-independent tumor recurrence. As a transcriptional target of PAX3-FOXO1, FGF8 promoted oncogenic activity in PAX3-FOXO1-expressing primary tumors that developed in the myoblast system. In the recurrent tumors forming after PAX3-FOXO1 deinduction, FGF8 expression was necessary and sufficient to induce PAX3-FOXO1-independent tumor growth through an autocrine mechanism. FGF8 was also expressed in human PAX3-FOXO1-expressing rhabdomyosarcoma cell lines and contributed to proliferation and transformation. In a human rhabdomyosarcoma cell line with reduced PAX3-FOXO1 expression, FGF8 upregulation rescued oncogenicity and simulated recurrence after PAX3-FOXO1-targeted therapy. We propose that deregulated expression of a PAX3-FOXO1 transcriptional target can generate resistance to therapy directed against this oncogenic transcription factor and postulate that this resistance mechanism may ultimately be countered by therapeutic approaches that antagonize the corresponding downstream pathways. SIGNIFICANCE: In a model of cancer initiated by a fusion transcription factor, constitutive activation of a downstream transcriptional target leads to fusion oncoprotein-independent recurrences, thereby highlighting a novel progression mechanism and therapeutic target.

Synthetic cannabinoid CP-55,940 induces apoptosis in a human skeletal muscle model via regulation of CB1 receptors and L-type Ca2+ channels.

Rhabdomyolysis has been reported in patients who abuse synthetic cannabinoids. However, no studies have yet assessed whether these cases reflect the direct cytotoxicity of synthetic cannabinoids on skeletal muscle, a possibility that the present study sought to address. Specifically, this study investigated the cytotoxicity of the synthetic cannabinoid CP-55,940, a compound that acts equally on both types of cannabinoid receptors (CB1 and CB2), in a human embryonic rhabdomyosarcoma (RD) cell line. Exposure of these cells to CP-55,940 resulted in concentration-dependent decreases in cell viability. These effects were attenuated by pre-incubation with AM251 (30µM), a selective CB1 receptor antagonist, but not by pre-incubation with AM630 (30µM), a selective CB2 receptor antagonist. Following treatment with CP-55,940, RD cells exhibited apoptosis, as indicated by the accumulation of annexin-V, activation of caspase-3, and a loss of the mitochondrial membrane potential. Additionally, CP-55,940 treatment of RD cells led to increases in intracellular Ca2+ levels. CP-55,940-induced cell death was significantly attenuated in the absence of extracellular Ca2+, and was partially decreased by pre-incubation with verapamil (5µM) or diltiazem (5µM), compounds that block the L-type Ca2+ channel. Our results indicate that the cytotoxicity of CP-55,940 towards RD cells (skeletal muscle cells) is mediated by the CB1 receptor, but not by the CB2 receptor. Our results further suggest that calcium influx through the L-type channel may play an important role in the apoptosis induced by these compounds.

Growth inhibition associated with disruption of the actin cytoskeleton by Latrunculin A in rhabdomyosarcoma cells.

Functional genomic screening of KRAS-driven mouse sarcomas was previously employed to identify proliferation-relevant genes. Genes identified included Ubiquitin-conjugating enzyme E2 (Ube2c), Centromere Protein E (Cenpe), Hyaluronan Synthase 2 (Has2), and CAMP Responsive Element Binding Protein 3 Like 2 (Creb3l2). This study examines the expression and chemical inhibition of these candidate genes, identifying variable levels of protein expression and significant contributions to rhabdomyosarcoma (RMS) cell proliferation. Chemical treatment of human and murine RMS cell lines with bortezomib, UA62784, latrunculin A and sorafenib inhibited growth with approximate EC50 concentrations of 15-30nM for bortezomib, 25-80nM for UA62784 and 80-220nM for latrunculin A. The multi-kinase inhibitor sorafenib increased in vitro proliferation of 4 of 6 sarcoma cell lines tested. Latrunculin A was further associated with disruption of the actin cytoskeleton and reduced ERK1/2 phosphorylation. Together, this work advances opportunities for developing therapies to block progression of soft-tissue sarcomas and demonstrates that disruption of the actin cytoskeleton in sarcoma cells by latrunculin A is associated with a reduction in RMS cell growth. (167 words).

Abstract 5001: Barriers to adoptive immunotherapy of pediatric cancer

Abstract As the adoptive immunotherapy with chimeric antigen modified T cells (CAR-T) has not proven effective in pediatric solid tumors, we established a model to define which tumor- and stromal-derived factors must be surmounted to obtain effective treatment. The human alveolar rhabdomyosarcoma cell line RH30 (fusion gene positive) was administered both i.v. and i.m. to NSG mice, and subsequently treated with a FGFR4-specifc CAR-T cells (expressing the M410 binder). Although some response was noted in the i.v. model, the i.m. tumor was entirely resistant. We observed that in both primary tumors and liver metastases RH30 was surrounded with a rich stromal element when CAR-T or control activated T cells were administered. Trichrome and H&E histochemical analysis of i.m. tumors confirmed the presence of a rich collagen-containing stromal element in T cell treated mice. This was not present in untreated tumors. We therefore analyzed cell surface and soluble factors produced by RH30 by RNA array analysis, flow cytometry and ELISA in cultured RH30 alone, or treated with interferon-gamma (IFNG) to model the presence of activated T cells. RH30 expressed transcripts for both canonical and non-canonical chemokines: CCL24, GPI, MIF, CCL26, CCL20, CCL2; as well as the cytokines: IL-15, IL-32, LIF, TGFB1, and CSF1. ELISA confirmed high expression of MIF, TGFB1, CCL24 and LIF. Transcripts for the chemokines CCL8, 9, 10, and 11 were expressed at low or undetectable levels, but were strongly induced by IFNG. And although class I MHC was present, and upregulated in the presence of IFNG, so was PDL1. Surface marker analysis by flow cytometry demonstrated that CD80, CD86 and CXCR2 are absent while the CAR-T targets CD276, EGFR, FGFR4 as well as CXCR4 are present. Flow cytometry also demonstrated consistent expression of PDL2, GAL-9, and CTLA4, and strong induction of HLA class I and PDL1 by IFNG treatment of RH30. We are currently evaluating CRISPR knock-out lines of each soluble factor for effects on gene expression, IFNG-induced marker expression, and tumor stroma in vivo. Our results indicate that in this model of rhabdomyosarcoma, tumor surface expression of glycoproteins that give an immune inhibitory signal, PDL1, PDL2, CTLA4, GAL-9, as well as soluble modulators known to be associated with tumor escape from immune control, MIF, TGFB, and LIF, all must be considered in armoring CAR-T for effective immune destruction of tumor. Moreover, the numerous chemokines produced by tumor alone, as well as induced by IFNG, indicate a complex network for recruitment of local and bone marrow-derived stromal cells that create a physical as well as cellular barrier to adoptive immunotherapy. Citation Format: Rajesh Kumar, Nityashree Shivaprasad, Virginia Hoglund, Cosette LeCeil, Lingyan Wang, Yue Zhang, Dimiter S. Dimitrov, Javed Khan, Rimas J. Orentas. Barriers to adoptive immunotherapy of pediatric cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5001.