Patient-derived Xenograft Mouse Research Articles

Epstein-Barr Virus-Encoded MicroRNA-BART18-3p Promotes Colorectal Cancer Progression by Targeting De Novo Lipogenesis.

The Epstein-Barr virus (EBV) genome encodes a cluster of 22 viral microRNAs, called miR-BamHI-A rightward transcripts (miR-BARTs), which are shown to promote the development of cancer. Here, this study reports that EBV-miR-BART18-3p is highly expressed in colorectal cancer (CRC) and is closely associated with the pathological and advanced clinical stages of CRC. Ectopic expression of EBV-miR-BART18-3p leads to increased migration and invasion capacities of CRC cells in vitro and causes tumor metastasis in vivo. Mechanistically, EBV-miR-BART18-3p activates the hypoxia inducible factor 1 subunit alpha/lactate dehydrogenase A axis by targeting Sirtuin, which promotes lactate accumulation and acetyl-CoA production in CRC cells under hypoxic condition. Increased acetyl-CoA utilization subsequently leads to histone acetylation of fatty acid synthase and fatty acid synthase-dependent fat synthesis, which in turn drives de novo lipogenesis. The oncogenic role of EBV-miR-BART18-3p is confirmed in the patient-derived tumor xenograft mouse model. Altogether, the findings define a novel mechanism of EBV-miR-BART18-3p in CRC development through the lipogenesis pathway and provide a potential clinical intervention target for CRC.

Treatment of HCC with claudin-1-specific antibodies suppresses carcinogenic signaling and reprograms the tumor microenvironment

Despite recent approvals, the response to treatment and prognosis of patients with advanced hepatocellular carcinoma (HCC) remain poor. Claudin-1 (CLDN1) is a membrane protein that is expressed at tight junctions, but it can also be exposed non-junctionally, such as on the basolateral membrane of the human hepatocyte. While CLDN1 within tight junctions is well characterized, the role of non-junctional CLDN1 and its role as a therapeutic target in HCC remains unexplored. Using humanized monoclonal antibodies (mAbs) specifically targeting the extracellular loop of human non-junctional CLDN1 and a large series of patient-derived cell-based and animal model systems we aimed to investigate the role of CLDN1 as a therapeutic target for HCC. Targeting non-junctional CLDN1 markedly suppressed tumor growth and invasion in cell line-based models of HCC and patient-derived 3D exvivo models. Moreover, the robust effect on tumor growth was confirmed invivo in a large series of cell line-derived xenograft and patient-derived xenograft mouse models. Mechanistic studies, including single-cell RNA sequencing of multicellular patient HCC tumorspheres, suggested that CLDN1 regulates tumor stemness, metabolism, oncogenic signaling and perturbs the tumor immune microenvironment. Our results provide the rationale for targeting CLDN1 in HCC and pave the way for the clinical development of CLDN1-specific mAbs for the treatment of advanced HCC. Hepatocellular carcinoma (HCC) is associated with high mortality and unsatisfactory treatment options. Herein, we identified the cell surface protein Claudin-1 as a treatment target for advanced HCC. Monoclonal antibodies targeting Claudin-1 inhibit tumor growth in patient-derived exvivo and invivo models by modulating signaling, cell stemness and the tumor immune microenvironment. Given the differentiated mechanism of action, the identification of Claudin-1 as a novel therapeutic target for HCC provides an opportunity to break the plateau of limited treatment response. The results of this preclinical study pave the way for the clinical development of Claudin-1-specific antibodies for the treatment of advanced HCC. It is therefore of key impact for physicians, scientists and drug developers in the field of liver cancer and gastrointestinal oncology.

Oral-recombinant Methioninase in Combination With Rapamycin Eradicates Osteosarcoma of the Breast in a Patient-derived Orthotopic Xenograft Mouse Model

Primary osteosarcoma of the breast is a very rare malignancy that shares histological features with osteosarcoma. It is also highly sensitive to methionine restriction due to methionine addiction. We previously established a patient-derived orthotopic xenograft (PDOX) nude-mouse model derived from tumor tissue of a patient with primary mammary osteosarcoma. In the present study, we investigated the efficacy of oral-recombinant methioninase (o-rMETase), combined with rapamycin, an inhibitor of mammalian target of rapamycin (mTOR) kinase, on a mammary osteosarcoma PDOX nude-mouse model. The PDOX mouse model was established by surgically transplanting a specimen of primary osteosarcoma of the breast into the mammary gland of nude mice. Mice implanted with tumors were randomly divided into four groups: Control group, N=5; rapamycin-treated group, N=5; o-rMETase-treated group, N=5; and a group treated with the combination of o-rMETase and rapamycin, N=5. Mice were treated for 2 weeks after transplantation, and tumor volume was measured during the treatment period. Treatment with the combination of rapamycin and o-rMETase eradicated the osteosarcoma of the breast compared to the untreated control (p=0.000008). o-rMETase alone did not significantly inhibit tumor growth, and rapamycin alone only partially inhibited the tumor (p=0.78 and p=0.018, respectively) compared to the untreated control. There was not a significant difference in mouse weight between the groups. The combination of rapamycin and o-rMETase was highly effective against primary osteosarcoma of the breast in a PDOX model, suggesting a future clinical strategy for this rare cancer type that currently has no first-line treatment.

Preclinical Evaluation of the Multiple Tyrosine Kinases Inhibitor Anlotinib in Leukemia Stem Cells.

Leukemia stem cells (LSCs) constitute the critical barrier to the cure of acute myeloid leukemia (AML) due to their chemoresistance and immune evasion property. Herein, the role of anlotinib, a multiple tyrosine kinase inhibitor, in killing LSCs and regulating chemoresistance and immune evasion was explored. Anlotinib treatment induced apoptosis of LSC-like cells as well as primary AML LSCs, while sparing the normal mononuclear cells in vitro. Moreover, anlotinib could impair the regeneration capacity of LSCs in the patient-derived leukemia xenograft mouse model. Mechanistically, anlotinib inhibited phosphorylation of c-kit, JAK2/STAT3, and STAT5, and downregulated STAT3 and STAT5 expression. In addition, anlotinib downregulated the anti-apoptotic proteins Bcl-2 and Bcl-xL, and upregulated Bax, thereby enhancing the sensitivity of LSCs to idarubicin in vitro. Intriguingly, anlotinib could also partially rescue the interferon-g production of T cells cocultured with LSCs by downregulating PD-L1 expression. In conclusion, anlotinib showed anti-LSC activity and the potential to enhance the sensitivity to idarubicin and inhibit the immunosuppressive feature of LSCs via JAK2/STAT signaling pathway downregulation in the preclinical study. Our results provided a rational basis for combinatory strategies involving anlotinib and chemotherapy or immunotherapy.

Dual inhibition of EZH1/2 induces cell cycle arrest of B cell acute lymphoblastic leukemia cells through upregulation of CDKN1C and TP53INP1.

Disease-risk stratification and development of intensified chemotherapy protocols have substantially improved the outcome of acute lymphoblastic leukemia (ALL). However, outcomes of relapsed or refractory cases remain poor. Previous studies have discussed the oncogenic role of enhancer of zeste homolog 1 and 2 (EZH1/2), and the efficacy of dual inhibition of EZH1/2 as a treatment for hematological malignancy. Here, we investigated whether an EZH1/2 dual inhibitor, DS-3201 (valemetostat), has antitumor effects on B cell ALL (B-ALL). DS-3201 inhibited growth of B-ALL cell lines more significantly and strongly than the EZH2-specific inhibitor EPZ-6438, and induced cell cycle arrest and apoptosis in vitro. RNA-seq analysis to determine the effect of DS-3201 on cell cycle arrest-related genes expressed by B-ALL cell lines showed that DS-3201 upregulated CDKN1C and TP53INP1. CRIPSR/Cas9 knockout confirmed that CDKN1C and TP53INP1 are direct targets of EZH1/2 and are responsible for the antitumor effects of DS-3201 against B-ALL. Furthermore, a patient-derived xenograft (PDX) mouse model showed that DS-3201 inhibited the growth of B-ALL harboring MLL-AF4 significantly. Thus, DS-3201 provides another option for treatment of B-ALL.

Integrative genomic analysis of drug resistance in MET exon 14 skipping lung cancer using patient-derived xenograft models.

Non-small cell lung cancer (NSCLC) driven by MET exon 14 skipping (METex14) occurs in 3-4% of NSCLC cases and defines a subset of patients with distinct characteristics. While MET targeted therapy has led to strong clinical results in METex14 patients, acquired drug resistance seemed to be unavoidable during treatment. Limited information is available regarding acquired resistance during MET targeted therapy, nor has there been any report on such patient-derived xenografts (PDXs) model facilitating the research. We describe a patient case harboring METex14 who exhibited drug resistance after treatment with crizotinib. Subcutaneous xenografts were generated from pretreatment and post-resistance patient specimens. PDX mice were then treated with MET inhibitors (crizotinib and tepotinib) and EGFR-MET bispecific antibodies (EMB-01 and amivantamab) to evaluate their drug response in vivo. DNA and RNA sequencing analysis was performed on patient tumor specimens and matching xenografts. PDXs preserved most of the histological and molecular profiles of the parental tumors. Drug resistance to MET targeted therapy was confirmed in PDX models through in vivo drug analysis. Newly acquired MET D1228H mutations and EGFR amplificated were detected in patient-resistant tumor specimens. Although the mutations were not detected in the PDX, EGFR overexpression was observed in RNA sequencing analysis indicating possible off-target resistance through the EGFR bypass signaling pathway. As expected, EGFR-MET bispecific antibodies overcome drug resistant in the PDX model. We detected a novel MET splice site deletion mutation that could lead to METex14. We also established and characterized a pair of METex14 NSCLC PDXs, including the first crizotinib resistant METex14 PDX. And dual inhibition of MET and EGFR might be a therapeutic strategy for EGFR-driven drug resistance METex14 lung cancer.

Targeting Asparagine Synthetase in Tumorgenicity Using Patient-Derived Tumor-Initiating Cells.

Reprogramming of energy metabolism is regarded as one of the hallmarks of cancer; in particular, oncogenic RAS has been shown to be a critical regulator of cancer metabolism. Recently, asparagine metabolism has been heavily investigated as a novel target for cancer treatment. For example, Knott et al. showed that asparagine bioavailability governs metastasis in a breast cancer model. Gwinn et al. reported the therapeutic vulnerability of asparagine biosynthesis in KRAS-driven non-small cell lung cancer. We previously reported that KRAS-mutated CRC cells can adapt to glutamine depletion through upregulation of asparagine synthetase (ASNS), an enzyme that synthesizes asparagine from aspartate. In our previous study, we assessed the efficacy of asparagine depletion using human cancer cell lines. In the present study, we evaluated the clinical relevance of asparagine depletion using a novel patient-derived spheroid xenograft (PDSX) mouse model. First, we examined ASNS expression in 38 spheroid lines and found that 12 lines (12/37, 32.4%) displayed high ASNS expression, whereas 26 lines (25/37, 67.6%) showed no ASNS expression. Next, to determine the role of asparagine metabolism in tumor growth, we established ASNS-knockdown spheroid lines using lentiviral short hairpin RNA constructs targeting ASNS. An in vitro cell proliferation assay demonstrated a significant decrease in cell proliferation upon asparagine depletion in the ASNS-knockdown spheroid lines, and this was not observed in the control spheroids lines. In addition, we examined asparagine inhibition with the anti-leukemia drug L-asparaginase (L-Asp) and observed a considerable reduction in cell proliferation at a low concentration (0.1 U/mL) in the ASNS-knockdown spheroid lines, whereas it exhibited limited inhibition of control spheroid lines at the same concentration. Finally, we used the PDSX model to assess the effects of asparagine depletion on tumor growth in vivo. The nude mice injected with ASNS-knockdown or control spheroid lines were administered with L-Asp once a day for 28 days. Surprisingly, in mice injected with ASNS-knockdown spheroids, the administration of L-Asp dramatically inhibited tumor engraftment. On the other hands, in mice injected with control spheroids, the administration of L-Asp had no effect on tumor growth inhibition at all. These results suggest that ASNS inhibition could be critical in targeting asparagine metabolism in cancers.

Gene-centric multi-omics integration with convolutional encoders for cancer drug response prediction

Motivation: Tumor heterogeneity, including genetic and transcriptomic characteristics, can reduce the efficacy of anticancer pharmacological therapy, resulting in clinical variability in patient response to therapeutic medications. Multi-omics integration can allow in silico models to provide an additional perspective on a biological system. Methods:In this study, we propose a gene-centric multi-channel (GCMC) architecture to integrate multi-omics for predicting cancer drug response. GCMC transformed multi-omics profiles into a three-dimensional tensor with an additional dimension for omics types. GCMC’s convolutional encoders captures multi-omics profiles for each gene and yields gene-centric features to predict drug responses. Results:We evaluated GCMC on various datasets, including The Cancer Genome Atlas (TCGA) patients, patient-derived xenografts (PDX) mice models, and the Genomics of Drug Sensitivity in Cancer (GDSC) cell line datasets. GCMC achieved better performance than baseline models, including single-omics models, in more than 75% of 265 drugs from GDSC cell line datasets. Furthermore, as for the clinical applicability of GCMC, it achieved the best performance on TCGA and PDX datasets in terms of both AUPR and AUC. We also analyzed models’ capability of integrating multi-omics profiles by measuring the contribution ratio of omics types. GCMC can incorporate multi-omics profiles in various manners to enhance performance for each drug type. These results suggested that GCMC can improve performance and feature extraction capability by integrating multi-omics profiles in a gene-centric manner.

DMA, a Small Molecule, Increases Median Survival and Reduces Radiation-Induced Xerostomia via the Activation of the ERK1/2 Pathway in Oral Squamous Cell Carcinoma.

Simple SummaryRadiotherapy is commonly used to treat the majority of patients with head and neck cancers. Salivary glands in the radiation field are affected by this procedure. The purpose of this study was to investigate the role of DMA as a radiomodulator to evaluate the real possibilities of reducing the incidence and severity of xerostomia in head and neck squamous cell carcinoma (HNSCC) patients. The effect of DMA on the response of head and neck cell lines in the presence of radiation was analyzed using clonogenic survival and xenograft tumor assays for cell line-derived xenografts as well as patient-derived xenografts. The combinatorial treatment of DMA along with radiation influenced the migration of cells. The changes associated with migration were observed through a microscope and wound healing assay. In addition, the stimulated saliva was measured. Tissue sections were analyzed using immunohistochemistry to stain for molecular markers of cell proliferation and porin channels.Survival, recurrence, and xerostomia are considerable problems in the treatment of oral squamous carcinoma patients. In this study, we investigated the role of DMA (5-(4-methylpiperazin-1-yl)-2-[2′-(3,4-dimethoxyphenyl)5″benzimidazoyl]benzimidazole) as a salivary gland cytoprotectant in a patient-derived xenograft mouse model. A significant increase in saliva secretion was observed in the DMA-treated xenograft compared to radiation alone. Repeated doses of DMA with a high dose of radiation showed a synergistic effect on mice survival and reduced tumor growth. The mean survival rate of tumor-bearing mice was significantly enhanced. The increased number of Ki-67-stained cells in the spleen, intestine, and lungs compared to the tumor suggests DMA ablates the tumor but protects other organs. The expression of aquaporin-5 was restored in tumor-bearing mice injected with DMA before irradiation. The reduced expression of αvβ3 integrin and CD44 in DMA alone and DMA with radiation-treated mice suggests a reduced migration of cells and stemness of cancer cells. DMA along with radiation treatment results in the activation of the Ras/Raf/MEK/ERK pathway in the tumor, leading to apoptosis through caspase upregulation. In conclusion, DMA has strong potential for use as an adjuvant in radiotherapy in OSCC patients.

NOTCH Signaling Limits the Response of Low-Grade Serous Ovarian Cancers to MEK Inhibition.

Low-grade serous ovarian cancer (LGSOC) is a rare subtype of epithelial ovarian cancer with high fatality rates in advanced stages due to its chemoresistant properties. LGSOC is characterized by activation of MAPK signaling, and recent clinical trials indicate that the MEK inhibitor (MEKi) trametinib may be a good treatment option for a subset of patients. Understanding MEKi-resistance mechanisms and subsequent identification of rational drug combinations to suppress resistance may greatly improve LGSOC treatment strategies. Both gain-of-function and loss-of-function CRISPR-Cas9 genome-wide libraries were used to screen LGSOC cell lines to identify genes that modulate the response to MEKi. Overexpression of MAML2 and loss of MAP3K1 were identified, both leading to overexpression of the NOTCH target HES1, which has a causal role in this process as its knockdown reversed MEKi resistance. Interestingly, increased HES1 expression was also observed in selected spontaneous trametinib-resistant clones, next to activating MAP2K1 (MEK1) mutations. Subsequent trametinib synthetic lethality screens identified SHOC2 downregulation as being synthetic lethal with MEKis. Targeting SHOC2 with pan-RAF inhibitors (pan-RAFis) in combination with MEKi was effective in parental LGSOC cell lines, in MEKi-resistant derivatives, in primary ascites cultures from patients with LGSOC, and in LGSOC (cell line-derived and patient-derived) xenograft mouse models. We found that the combination of pan-RAFi with MEKi downregulated HES1 levels in trametinib-resistant cells, providing an explanation for the synergy that was observed. Combining MEKis with pan-RAFis may provide a promising treatment strategy for patients with LGSOC, which warrants further clinical validation.

Selected Articles from This Issue

Highlights| October 03 2022 Selected Articles from This Issue Author & Article Information Online ISSN: 1557-3265 Print ISSN: 1078-0432 ©2022 American Association for Cancer Research2022American Association for Cancer Research Clin Cancer Res (2022) 28 (19): 4159. https://doi.org/10.1158/1078-0432.CCR-28-19-HI Related Content A commentary has been published: Clinical, Pathologic, and Molecular Prognostic Factors in Patients with Early-Stage EGFR-Mutant NSCLC A commentary has been published: Detection of Occult Recurrence Using Circulating Tumor Tissue Modified Viral HPV DNA among Patients Treated for HPV-Driven Oropharyngeal Carcinoma A commentary has been published: Microsatellite Instability–High Endometrial Cancers with MLH1 Promoter Hypermethylation Have Distinct Molecular and Clinical Profiles View more A commentary has been published: OLIG2 Is a Determinant for the Relapse of MYC-Amplified Medulloblastoma View less Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Article Versions Icon Versions Version of Record October 3 2022 Citation Selected Articles from This Issue. Clin Cancer Res 1 October 2022; 28 (19): 4159. https://doi.org/10.1158/1078-0432.CCR-28-19-HI Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest Search Advanced Search Patients with MYC-amplified medulloblastoma (MB) have poor prognosis and frequently develop recurrence; thus new therapeutic approaches to prevent recurrence are needed. Here, Xu and colleagues demonstrate that OLIG2-expressing tumor cells are highly enriched in therapy resistant and recurrent MYC-amplified MB and high levels of OLIG2 correlated with poor prognosis. Genetic or pharmacological inhibition of OLIG2 in combination with radiotherapy significantly suppressed the progression of OLIG2-high tumors in patient-derived xenograft mouse models, indicating that OLIG2 represents a novel therapeutic target in high-risk MB. CT-179 is a highly potent and selective small molecule OLIG2 inhibitor. The study provides evidence for CT-179 to potentially act as an adjunctive therapy for patients with high-risk MB as well as other types of pediatric brain tumors where OLIG2 is highly expressed. Thus patients with these cancers may also benefit from CT-179 treatment. Cell-free tumor tissue modified viral (TTMV)-HPV DNA is a unique biomarker, present... You do not currently have access to this content.

TRANSCRIPTOME ANALYSIS REVEALS THAT VITAMIN D LOW-DOSE TARGETS EXTRACELLULAR MATRIX AND WNT/Β-CATENIN PATHWAY IN A XENOGRAFT MOUSE MODEL HARBORING UTERINE FIBROIDS FROM AFRICAN AMERICAN PATIENTS

To determine the effect of Vitamin D (Vit D) low-dose treatment on uterine fibroids (UF) gene expression in a patient-derived xenograft (PDX) mouse model.

127 (PB117) - Using patient-derived xenografts as sources of 3D tumor sphere cultures to study autologous tumor-infiltrating lymphocytes in metastatic uveal melanoma

Introduction: Uveal melanoma (UM) is a rare form of melanoma, but the most common primary malignancy of the eye. 50% of patients with UM develop metastasis, mainly to the liver, with a median survival of less than a year. Immune checkpoint inhibitors are markedly less effective in patients with the uveal form as compared to the cutaneous form of melanoma. Adoptive cell therapy (ACT) has not been extensively studied clinically or preclinically in UM. There has been a lack of robust ex vivo screening models and very few patient-derived xenograft (PDX) mouse models.

ChemoSeed®: A Novel Implantable Device for the Treatment of High Grade Gliomas

Abstract AIMS The treatment of high grade gliomas (HGGs) is extremely toxic, while offering a dismal prognosis of 15 months survival. Irinotecan (IRN) is a second-line therapy due to its dose-limiting toxicities when delivered systemically. The aim of this research is to formulate IRN into ChemoSeed for local administration to the resection margin of HGGs and evaluate it for toxicity and efficacy in a Patient-Derived Xenograft mouse resection model. METHOD 30 and 40% w/w IRN-loaded ChemoSeeds were manufactured using hot melt extrusion and were subsequently implanted into the resection cavity of HGG tumour bearing mice. RESULTS The 30% w/w IRN-loaded ChemoSeeds showed moderate local toxicity two days after implantation, which diminished by day 4. The 40% w/w IRN-loaded ChemoSeeds showed signs of moderate local toxicity up to six days post implantation, diminishing by day 8 with mild toxicity returning at day 14. Histopathology of the implantation site showed signs of the onset of necrosis at day 45 and 14 for the 30% and 40% w/w IRN-loaded ChemoSeeds. Hematological analysis and clinical chemistry showed no signs of serious systemic toxicity for either the 30 or 40% w/w IRN-loaded ChemoSeeds. The 30% w/w IRN-loaded ChemoSeeds had an 80% survival at day 148, with no sign of tumour recurrence, while the 40% w/w group showed signs of tumour recurrence at day 21, with all mice dead by day 70. CONCLUSION This study demonstrates that the 30% w/w IRN-loaded ChemoSeeds are a promising novel treatment for HGGs that could be quickly translated into the clinic.

106 (PB096) - Omomyc mini-protein can be directly and continuously delivered to the brain to prevent glioblastoma in patient-derived xenograft mouse models

Background: Myc is a ‘hot target’ in oncology and implicated in the development of glioblastoma multiforme (GBM), a cancer with a dire prognosis and limited treatment options. Standard of care involves surgery, radiotherapy and treatment of residual tumour with temozolomide. Very few other treatment options exist and they do not significantly affect overall survival, which stands at around 15 months.

Precision medicine-guided co-delivery of ASPN siRNA and oxaliplatin by nanoparticles to overcome chemoresistance of colorectal cancer

The development of chemoresistance is a major hurdle for the treatment of colorectal cancer (CRC), which contributes remarkably to the poor clinical prognosis. Nanodrug delivery systems show great potential in overcoming chemoresistance, but limited by the lack of identification of chemoresistance targets from cancer patients. In the present study, we enrolled chemotherapy-resistant or sensitive CRC patients and used the next-generation RNA sequencing to reveal that Asporin (ASPN) is highly expressed in tumor tissues from oxaliplatin (OXA)-resistant patients and closely correlated with a poor prognosis of CRC. Downregulation of ASPN reversed OXA resistance and promoted cell apoptosis both in vitro and in vivo. To overcome ASPN-mediated OXA resistance, we constructed a nanoparticle-based co-delivery system (denoted as PPO-siASPN) for simultaneous delivery of OXA and siRNA targeting ASPN (siASPN). PPO-siASPN not only facilitated the intracellular delivery of OXA through the enhanced cellular uptake, but effectively suppressed ASPN expression for synergistic antitumor activity in vitro and in vivo. In the more clinically relevant patient-derived xenograft (PDX) mouse model, systemic administration of PPO-siASPN achieved a remarkable therapeutic effect. This study uncovered the critical role of ASPN in causing OXA resistance in CRC patients and suggests a promising nanoformulation that may be more effective than current standard-of-care medications.

Dominant-negative transforming growth factor-β receptor-armoured mesothelin-targeted chimeric antigen receptor T cells slow tumour growth in a mouse model of ovarian cancer

Ovarian cancer is a major cause of death among all gynaecological cancers. Although surgery, chemotherapy and targeted therapy have yielded successful outcomes, the 5-year survival rate remains < 30%. Adoptive immunotherapy, particularly chimeric antigen receptor (CAR) T-cell therapy, has demonstrated improved survival in acute lymphoblastic leukaemia with manageable toxicity. We explored CAR T-cell therapy in a preclinical mouse model of ovarian cancer. Second-generation CAR T cells were developed targeting mesothelin (MSLN), which is abundantly expressed in ovarian cancer. Cytotoxicity experiments were performed to verify the lethality of CAR T cells on target cells via flow cytometry. The in vivo antitumour activity of MSLN CAR T cells was also verified using a patient-derived xenograft (PDX) mouse model with human tumour-derived cells. We also evaluated the potency of CAR T cells directed to MSLN following co-expression of a dominant-negative transforming growth factor-β receptor type II (dnTGFβRII). Our data demonstrate that anti-MSLN CAR T cells specifically eliminate MSLN-expressing target cells in an MSLN density-dependent manner. This preclinical research promises an effective treatment strategy to improve outcomes for ovarian cancer, with the potential for prolonging survival while minimizing risk of on-target off-tumour toxicity.

Richter Syndrome: From Molecular Pathogenesis to Druggable Targets.

Simple SummaryChronic lymphocytic leukemia represents the most frequent leukemia in adults and evolves from an indolent phase to an aggressive lymphoma in 5–10% of the cases. Such clinico-pathologic transformation is known as Richter syndrome and represents a major unmet medical need because of treatment refractoriness, lack of targeted therapeutic strategies and unsatisfactory survival rates. Molecular investigations by innovative approaches have clarified in detail the pathogenesis of Richter syndrome and have led to the identification of the genetic and biologic changes associated with its evolution from indolent to aggressive disease. Knowledge of the molecular profile of Richter syndrome has revealed several molecular targets that may be exploited for devising novel therapeutic strategies, both with small molecules acting as pathway inhibitors and with monoclonal antibodies, that also include drug immunoconjugates. Clinical trials with these novel medicines are ongoing and may pave the way to a precision medicine approach to Richter syndrome.Richter syndrome (RS) represents the occurrence of an aggressive lymphoma, most commonly diffuse large B-cell lymphoma (DLBCL), in patients with chronic lymphocytic leukemia (CLL). Most cases of RS originate from the direct transformation of CLL, whereas 20% are de novo DLBCL arising as secondary malignancies. Multiple molecular mechanisms contribute to RS pathogenesis. B-cell receptor (BCR) overreactivity to multiple autoantigens is due to frequent stereotyped BCR configuration. Genetic lesions of TP53, CDKN2A, NOTCH1 and c-MYC deregulate DNA damage response, tumor suppression, apoptosis, cell cycle and proliferation. Hyperactivation of Akt and NOTCH1 signaling also plays a role. Altered expression of PD-1/PD-L1 and of other immune checkpoints leads to RS resistance to cytotoxicity exerted by T-cells. The molecular features of RS provide vulnerabilities for therapy. Targeting BCR signaling with noncovalent BTK inhibitors shows encouraging results, as does the combination of BCL2 inhibitors with chemoimmunotherapy. The association of immune checkpoint inhibitors with BCL2 inhibitors and anti-CD20 monoclonal antibodies is explored in early phase clinical trials with promising results. The development of patient-derived xenograft mice models reveals new molecular targets for RS, exemplified by ROR1. Although RS still represents an unmet medical need, understanding its biology is opening new avenues for precision medicine therapy.

Systemic Delivery of mPEG-Masked Trispecific T-Cell Nanoengagers in Synergy with STING Agonists Overcomes Immunotherapy Resistance in TNBC and Generates a Vaccination Effect.

T-cell engagers (TCEs) represent a breakthrough in hematological malignancy treatment but are vulnerable to antigen escape and lack a vaccination effect. The "immunologically cold" solid tumor presents substantial challenges due to intratumor heterogeneity and an immunosuppressive tumor microenvironment (TME). Here, a methoxy poly(ethylene glycol)(mPEG)-masked CD44×PD-L1/CD3 trispecific T-cell nanoengager loaded with the STING agonist c-di-AMP (CDA) (PmTriTNE@CDA) for the treatment of triple-negative breast cancer (TNBC) is rationally designed. PmTriTNE@CDA shows tumor-specific accumulation and is preferentially unmasked in response to a weakly acidic TME to prevent on-target off-tumor toxicity. The unmasked CD44×PD-L1/CD3 trispecific T-cell nanoengager (TriTNE) targets dual tumor-associated antigens (TAAs) to redirect CD8+ T cells for heterogeneous TNBC lysis while achieving PD-L1 blockade. PmTriTNE synergized with CDA to transform the cold tumor into a hot tumor, eradicate the large established TNBC tumor, and induce protective immune memory in a 4T1 orthotopic tumor model without causing obvious toxicity. PmTriTNE@CDA shows potent efficacy in cell line-derived xenograft (CDX) and patient-derived xenograft (PDX) mouse models. This study serves as a proof-of-concept demonstration of a nanobased TCEs strategy to expand therapeutic combinations that previously could not be achieved due to systemic toxicity with the aim of overcoming TNBC heterogeneity and immunotherapy resistance.

OS10.5.A Modeling immunocompetent tumor microenvironment in glioblastoma patient-derived orthotopic xenografts

Abstract Background To date, glioblastoma (GBM) remains a fatal disease, with a median overall survival of roughly over a year. There is a crucial need of new treatment options, yet most clinical trials have failed partly due to the lack of predictive preclinical model systems. Currently, most patient-derived preclinical models suffer from the reduction or absence of immune system components, which represents a bottleneck for adequate immunotherapy testing. Humanized mice offer new opportunities here, since they rebuild an adaptive human immune system in a NSG mouse. Derivation of glioblastoma patient-derived orthotopic xenografts (PDOXs) in humanized mice appears thus as a promising tool for testing new treatment strategies targeting the tumor microenvironment (TME). Material and Methods We derived PDOXs through intracranial implantation of GBM primary organoids in different immunocompromised mouse strains (Nude, NOD/SCID, NSG). To introduce back the adaptive human immune system, GBM PDOXs were further derived in human CD34+ hematopoietic stem cell-engrafted NSG (HU-CD34+) mice. We applied single-cell RNA-sequencing, multicolor flow cytometry, immunohistochemical analyses and functional studies to examine the heterogeneous TME in a cohort of GBM PDOX models. We further interrogated the contribution and crosstalk between the human and mouse components constituting the brain TME in HU-CD34+ PDOXs. Results We show that glioma PDOXs can be derived in mice of different background including Nude, NOD-SCID, NSG and HU-CD34+ mice. Mouse-derived TME created in PDOX models contains tumor-associated macrophages (TAMs) known as major immuno-suppressive components of human GBM tumors. We further show that PDOXs derived in HU-CD34+ NSG mice present human CD45+ immune cells in the bone marrow and blood. Interestingly, we detect an influx of human immune cells in tumors developed in the mouse brain, which interact with the brain-derived immunosuppressive TME of mouse origin. Conclusion We here provide a thorough characterization of the heterogeneous brain TME created in GBM PDOX models. We show that human GBM can instruct mouse-derived brain cells towards immune-suppressive TME. The missing adaptive immune component can be introduced by derivation of GBM PDOXs in humanized mice. Such immunocompetent in vivo models will be important for testing novel therapies targeting different immune components in GBM.