Rhabdoid Tumors Are Sensitive to the Protein-Translation Inhibitor Homoharringtonine

Homoharringtonine promotes heart allograft acceptance by enhancing regulatory T cells induction in a mouse model

BACKGROUND

Homoharringtonine (HHT) is an effective anti-inflammatory, anti-viral, and anti-tumor protein synthesis inhibitor that has been applied clinically. Here, we explored the therapeutic effects of HHT in a mouse heart transplant model.

METHODS

Healthy C57BL/6 mice were used to observe the toxicity of HHT in the liver, kidney, and hematology. A mouse heart transplantation model was constructed, and the potential mechanism of HHT prolonging allograft survival was evaluated using Kaplan-Meier analysis, immunostaining, and bulk RNA sequencing analysis. The HHT-T cell crosstalk was modeled ex vivo to further verify the molecular mechanism of HHT-induced regulatory T cells (Tregs) differentiation.

RESULTS

HHT inhibited the activation and proliferation of T cells and promoted their apoptosis ex vivo . Treatment of 0.5 mg/kg HHT for 10 days significantly prolonged the mean graft survival time of the allografts from 7 days to 48 days ( P <0.001) without non-immune toxicity. The allografts had long-term survival after continuous HHT treatment for 28 days. HHT significantly reduced lymphocyte infiltration in the graft, and interferon-γ-secreting CD4 + and CD8 + T cells in the spleen ( P <0.01). HHT significantly increased the number of peripheral Tregs (about 20%, P <0.001) and serum interleukin (IL)-10 levels. HHT downregulated the expression of T cell receptor (TCR) signaling pathway-related genes ( CD4 , H2-Eb1 , TRAT1 , and CD74 ) and upregulated the expression of IL-10 and transforming growth factor (TGF)-β pathway-related genes and Treg signature genes ( CTLA4 , Foxp3 , CD74 , and ICOS ). HHT increased CD4 + Foxp3 + cells and Foxp3 expression ex vivo , and it enhanced the inhibitory function of inducible Tregs.

CONCLUSIONS

HHT promotes Treg cell differentiation and enhances Treg suppressive function by attenuating the TCR signaling pathway and upregulating the expression of Treg signature genes and IL-10 levels, thereby promoting mouse heart allograft acceptance. These findings may have therapeutic implications for organ transplant recipients, particularly those with viral infections and malignancies, which require a more suitable anti-rejection medication.

Auranofin and reactive oxygen species inhibit protein synthesis and regulate the level of the PLK1 protein in Ewing sarcoma cells

Novel therapeutic approaches are needed for the treatment of Ewing sarcoma tumors. We previously identified that Ewing sarcoma cell lines are sensitive to drugs that inhibit protein translation. However, translational and therapeutic approaches to inhibit protein synthesis in tumors are limited. In this work, we identified that reactive oxygen species, which are generated by a wide range of chemotherapy and other drugs, inhibit protein synthesis and reduce the level of critical proteins that support tumorigenesis in Ewing sarcoma cells. In particular, we identified that both hydrogen peroxide and auranofin, an inhibitor of thioredoxin reductase and regulator of oxidative stress and reactive oxygen species, activate the repressor of protein translation 4E-BP1 and reduce the levels of the oncogenic proteins RRM2 and PLK1 in Ewing and other sarcoma cell lines. These results provide novel insight into the mechanism of how ROS-inducing drugs target cancer cells via inhibition of protein translation and identify a mechanistic link between ROS and the DNA replication (RRM2) and cell cycle regulatory (PLK1) pathways.

Developmental origins shape the paediatric cancer genome

In the past two decades, technological advances have brought unprecedented insights into the paediatric cancer genome revealing characteristics distinct from those of adult cancer. Originating from developing tissues, paediatric cancers generally have low mutation burden and are driven by variants that disrupt the transcriptional activity, chromatin state, non-coding cis-regulatory regions and other biological functions. Within each tumour, there are multiple populations of cells with varying states, and the lineages of some can be tracked to their fetal origins. Genome-wide genetic screening has identified vulnerabilities associated with both the cell of origin and transcription deregulation in paediatric cancer, which have become a valuable resource for designing new therapeutic approaches including those for small molecules, immunotherapy and targeted protein degradation. In this Review, we present recent findings on these facets of paediatric cancer from a pan-cancer perspective and provide an outlook on future investigations.

Auranofin and reactive oxygen species inhibit protein synthesis and regulate the level of the PLK1 protein in Ewing sarcoma cells

Novel therapeutic approaches are needed for the treatment of Ewing sarcoma tumors. We previously identified that Ewing sarcoma cell lines are sensitive to drugs that inhibit protein translation. However, translational and therapeutic approaches to inhibit protein synthesis in tumors are limited. In this work, we identified that reactive oxygen species, which are generated by a wide range of chemotherapy and other drugs, inhibit protein synthesis and reduce the level of critical proteins that support tumorigenesis in Ewing sarcoma cells. In particular, we identified that both hydrogen peroxide and auranofin, an inhibitor of thioredoxin reductase and regulator of oxidative stress and reactive oxygen species, activate the repressor of protein translation 4E-BP1 and reduce the levels of the oncogenic proteins RRM2 and PLK1 in Ewing and other sarcoma cell lines. These results provide novel insight into the mechanism of how ROS-inducing drugs target cancer cells via inhibition of protein translation and identify a mechanistic link between ROS and the DNA replication (RRM2) and cell cycle regulatory (PLK1) pathways.

Integration analysis using bioinformatics and experimental validation on the clinical and biological significance of TSLP in cancers

Thymic stromal lymphopoietin (TSLP) has significantly impacted the development and progression of various neoplastic disorders. To comprehensively evaluate the diverse significance of TSLP in malignant tumors, we first integrative analyze the TSLP expression level in paired and unpaired pan-cancer tissue and cell line, compared against the normal tissue. The correlation between TSLP expression, molecular subtypes, immune subtypes, diagnostic value, and prognostic value in pan-cancer was also investigated. We then explored the impact of TSLP expression on multifaced immune cell infiltration and subsequent clinical outcomes in lung adenocarcinoma (LUAD) patients. and conducted cellular experiments to functionally examine the effect of TSLP on cell proliferation, apoptosis, cell cycle, migration, and invasion in LUAD. The anti-neoplastic mechanism of TSLP was further investigated by qRT-PCR and western blotting. Our findings reveal that TSLP expression is abnormally low in various cancers compared to normal tissue and is associated with different molecular and immune subtypes of cancers. Moreover, ROC and survival analysis results suggest that TSLP expression is correlated with the diagnostic, prognostic, clinical features, and immune cells of LUAD patients. Cell experiments showed that overexpression of TSLP elicited a significant reduction in LUAD cell viability, promoted cell apoptosis, impeded cell cycle progression in the G2/M phase, and inhibited cell migration and invasion. In addition, TSLP inhibited LUAD progression through the JAK1/STAT3 signaling pathway. Therefore, targeting TSLP shows potential as a therapeutic strategy for pan-cancer, particularly for LUAD, and as a biomarker for predicting the prognosis of this malignancy.

Transcriptional-translational conflict is a barrier to cellular transformation and cancer progression

We uncover a tumor-suppressive process in urothelium called transcriptional-translational conflict caused by deregulation of the central chromatin remodeling component ARID1A. Loss of Arid1a triggers an increase in a nexus of pro-proliferation transcripts, but a simultaneous inhibition of the eukaryotic elongation factor 2 (eEF2), which results in tumor suppression. Resolution of this conflict through enhancing translation elongation speed enables the efficient and precise synthesis of a network of poised mRNAs resulting in uncontrolled proliferation, clonogenic growth, and bladder cancer progression. We observe a similar phenomenon in patients with ARID1A-low tumors, which also exhibit increased translation elongation activity through eEF2. These findings have important clinical implications because ARID1A-deficient, but not ARID1A-proficient, tumors are sensitive to pharmacologic inhibition of protein synthesis. These discoveries reveal an oncogenic stress created by transcriptional-translational conflict and provide a unified gene expression model that unveils the importance of the crosstalk between transcription and translation in promoting cancer.

Identification of Homoharringtonine as a potent inhibitor of glioblastoma cell proliferation and migration

We previously demonstrated that Annexin A2 (ANXA2) is a pivotal mediator of the pro-oncogenic features displayed by glioblastoma (GBM) tumors, the deadliest adult brain malignancies, being involved in cell stemness, proliferation and invasion, thus negatively impacting patient prognosis. Based on these results, we hypothesized that compounds able to revert ANXA2-dependent transcriptional features could be exploited as reliable treatments to inhibit GBM cell aggressiveness by hampering their proliferative and migratory potential. Transcriptional signatures obtained by the modulation of ANXA2 activity/levels were functionally mapped through the QUADrATiC bioinformatic tool for compound identification. Selected compounds were screened by cell proliferation and migration assays in primary GBM cells, and we identified Homoharringtonine (HHT) as a potent inhibitor of GBM cell motility and proliferation, without affecting their viability. A further molecular characterization of the effects displayed by HHT, confirmed its ability to inhibit a transcriptional program involved in cell migration and invasion. Moreover, we demonstrated that the multiple antitumoral effects displayed by HHT are correlated to the inhibition of a platelet derived growth factor receptor α (PDGFRα)-dependent intracellular signaling through the impairment of Signal transducer and activator of transcription 3 (STAT3) and Ras homolog family member A (RhoA) axes. Our results demonstrate that HHT may act as a potent inhibitor of cancer cell proliferation and invasion in GBM, by hampering multiple PDGFRα-dependent oncogenic signals transduced through the STAT3 and RhoA intracellular components, finally suggesting its potential transferability for achieving an effective impairment of peculiar GBM hallmarks.

Establishment and characterization of NCC-MRT1-C1: a novel cell line of malignant rhabdoid tumor

Malignant rhabdoid tumor (MRT) is a sarcoma histologically characterized by rhabdoid cells and genetically characterized by loss of function of the chromatin remodeling complex SWI/SNF induced by SMARCB1 gene deficiency. MRT mainly occurs in children, may arise in various locations, but is predominantly in the central nervous system (CNS) and kidney. Although MRT exhibits poor prognosis, standard treatment has not yet been established due to its extreme rarity. Patient-derived cancer cell lines are critical tools for basic and pre-clinical research in the development of chemotherapy. However, none of the MRT cell lines was derived from adult patients, and only one cell line was derived from the MRT of a soft tissue, despite the clinical behavior of MRT varying according to patient age and anatomic site. Herein, we reported the first cell line of MRT isolated from the soft tissue of an adult patient and named it NCC-MRT1-C1. NCC-MRT1-C1 cells showed a biallelic loss of the SMARCB1 gene. NCC-MRT1-C1 cells demonstrated rapid proliferation, spheroid formation, invasion capability in vitro, and tumorigenesis in nude mice. Screening of antitumor agents in NCC-MRT1-C1 cells resulted in the identification of six effective drugs. In conclusion, we report the first MRT cell line from the soft tissue of an adult patient. We believe that NCC-MRT1-C1 is a useful tool for developing novel chemotherapies for MRT.

Targeting the translational machinery in gastrointestinal stromal tumors (GIST): a new therapeutic vulnerability

Although KIT-mutant GISTs can be effectively treated with tyrosine kinase inhibitors (TKIs), many patients develop resistance to imatinib mesylate (IM) as well as the FDA-approved later-line agents sunitinib, regorafenib and ripretinib. Resistance mechanisms mainly involve secondary mutations in the KIT receptor tyrosine kinase gene indicating continued dependency on the KIT signaling pathway. The fact that the type of secondary mutation confers either sensitivity or resistance towards TKIs and the notion that secondary mutations exhibit intra- and intertumoral heterogeneity complicates the optimal choice of treatment in the imatinib-resistant setting. Therefore, new strategies that target KIT independently of its underlying mutations are urgently needed. Homoharringtonine (HHT) is a first-in-class inhibitor of protein biosynthesis and is FDA-approved for the treatment of chronic myeloid leukemia (CML) that is resistant to at least two TKIs. HHT has also shown activity in KIT-mutant mastocytosis models, which are intrinsically resistant to imatinib and most other TKIs. We hypothesized that HHT could be effective in GIST through downregulation of KIT expression and subsequent decrease of KIT activation and downstream signaling. Testing several GIST cell line models, HHT led to a significant reduction in nascent protein synthesis and was highly effective in the nanomolar range in IM-sensitive and IM-resistant GIST cell lines. HHT treatment resulted in a rapid and complete abolishment of KIT expression and activation, while KIT mRNA levels were minimally affected. The response to HHT involved induction of apoptosis as well as cell cycle arrest. The antitumor activity of HHT was confirmed in a GIST xenograft model. Taken together, inhibition of protein biosynthesis is a promising strategy to overcome TKI resistance in GIST.

Inhibitor of DNA binding 2 (ID2) regulates the expression of developmental genes and tumorigenesis in ewing sarcoma

Sarcomas are difficult to treat and the therapy, even when effective, is associated with long-term and life-threatening side effects. In addition, the treatment regimens for many sarcomas, including Ewing sarcoma, rhabdomyosarcoma, and osteosarcoma, are relatively unchanged over the past two decades, indicating a critical lack of progress. Although differentiation-based therapies are used for the treatment of some cancers, the application of this approach to sarcomas has proven challenging. Here, using a CRISPR-mediated gene knockout approach, we show that Inhibitor of DNA Binding 2 (ID2) is a critical regulator of developmental-related genes and tumor growth in vitro and in vivo in Ewing sarcoma tumors. We also identified that homoharringtonine, which is an inhibitor of protein translation and FDA-approved for the treatment of leukemia, decreases the level of the ID2 protein and significantly reduces tumor growth and prolongs mouse survival in an Ewing sarcoma xenograft model. Furthermore, in addition to targeting ID2, homoharringtonine also reduces the protein levels of ID1 and ID3, which are additional members of the ID family of proteins with well-described roles in tumorigenesis, in multiple types of cancer. Overall, these results provide insight into developmental regulation in Ewing sarcoma tumors and identify a novel, therapeutic approach to target the ID family of proteins using an FDA-approved drug.

Synergistic action of WDR5 and HDM2 inhibitors in SMARCB1-deficient cancer cells

Rhabdoid tumors (RT) are rare and deadly pediatric cancers driven by loss of SMARCB1, which encodes the SNF5 component of the SWI/SNF chromatin remodeler. Loss of SMARCB1 is associated with a complex set of phenotypic changes including vulnerability to inhibitors of protein synthesis and of the p53 ubiquitin-ligase HDM2. Recently, we discovered small molecule inhibitors of the 'WIN' site of WDR5, which in MLL-rearranged leukemia cells decrease the expression of a set of genes linked to protein synthesis, inducing a translational choke and causing p53-dependent inhibition of proliferation. Here, we characterize how WIN site inhibitors act in RT cells. As in leukemia cells, WIN site inhibition in RT cells causes the comprehensive displacement of WDR5 from chromatin, resulting in a decrease in protein synthesis gene expression. Unlike leukemia cells, however, the growth response of RT cells to WIN site blockade is independent of p53. Exploiting this observation, we demonstrate that WIN site inhibitor synergizes with an HDM2 antagonist to induce p53 and block RT cell proliferation in vitro. These data reveal a p53-independent action of WIN site inhibitors and forecast that future strategies to treat RT could be based on dual WDR5/HDM2 inhibition.

Current and Emerging Therapeutic Approaches for Extracranial Malignant Rhabdoid Tumors

Extracranial malignant rhabdoid tumors (extracranial MRT) are rare, highly aggressive malignancies affecting mainly infants and children younger than 3 years. Common anatomic sites comprise the kidneys (RTK – rhabdoid tumor of kidney) and other soft tissues (eMRT – extracranial, extrarenal malignant rhabdoid tumor). The genetic origin of these diseases is linked to biallelic pathogenic variants in the genes SMARCB1, or rarely SMARCA4, encoding subunits of the SWI/SNF chromatin-remodeling complex. Even if extracranial MRT seem to be quite homogeneous, recent epigenome analyses reveal a certain degree of epigenetic heterogeneity. Use of intensified therapies has modestly improved survival for extracranial MRT. Patients at standard risk profit from conventional therapies; most high-risk patients still experience a dismal course and often therapy resistance. Discoveries of clinical and molecular hallmarks and the exploration of experimental therapeutic approaches open exciting perspectives for clinical and molecularly stratified experimental treatment approaches. To ultimately improve the outcome of patients with extracranial MRTs, they need to be characterized and stratified clinically and molecularly. High-risk patients need novel therapeutic approaches including selective experimental agents in phase I/II clinical trials.

Update and New Insights on Future Cancer Drug Candidates From Plant-Based Alkaloids

Cancer is a complex multifactorial disease that results from alterations in many physiological and biochemical functions. Over the last few decades, it has become clear that cancer cells can acquire multidrug resistance to conventional anticancer drugs, resulting in tumor relapse. Thus, there is a continuous need to discover new and effective anticancer drugs. Natural products from plants have served as a primary source of cancer drugs and continue to provide new plant-derived anticancer drugs. The present review describes plant-based alkaloids, which have been reported as active or potentially active in cancer treatment within the past 4 years (2017-2020), both in preclinical research and/or in clinical trials. In addition, recent insights into the possible molecular mechanism of action of alkaloid prodrugs naturally present in plants are also highlighted.

Progress Update in Pediatric Renal Tumors

PURPOSE OF REVIEW

Pediatric renal tumors account for 7% of new cancer diagnoses in children. Here, we will review results from recently completed clinical trials informing the current standard of care and discuss targeted and immune therapies being explored for the treatment of high risk or relapsed/refractory pediatric renal malignancies.

RECENT FINDINGS

Cooperative group trials have continued to make improvements in the care of children with pediatric tumors. In particular, trials that standardize treatment of rare cancers (e.g., bilateral Wilms tumor) have improved outcomes significantly. We have seen improvements in event free and overall survival in recently completed clinical trials for many pediatric renal tumors. Still, there are subsets of rarer cancers where outcomes remain poor and new therapeutic strategies are needed. Future trials aim to balance treatment toxicity with treatment efficacy for those with excellent outcomes while identifying novel therapeutics for those with poor outcomes.