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The MST1R/RON receptor tyrosine kinase is a homologue of the more well-known MET receptor. Like MET, RON orchestrates cell signaling pathways that promote oncogenesis and enable cancer cell survival; however, it has a more unique role in the regulation of inflammation. RON was originally described as a transmembrane receptor expressed on tissue resident macrophages and various epithelial cells. RON is overexpressed in a variety of cancers and its activation modifies multiple signaling pathways with resultant changes in epithelial and immune cells which together modulate oncogenic phenotypes. While several RON isoforms have been identified with differences in structure, activation, and pathway regulation, increased RON expression and/or activation is consistently associated with worse outcomes. Tyrosine kinase inhibitors targeting RON have been developed, making RON an actionable therapeutic target.

The MST1R (RON) kinase is overexpressed in >80% of human pancreatic cancers, but its role in pancreatic carcinogenesis is unknown. In this study, we examined the relevance of Mst1r kinase to Kras driven pancreatic carcinogenesis using genetically engineered mouse models. In the setting of mutant Kras, Mst1r overexpression increased acinar-ductal metaplasia (ADM), accelerated the progression of pancreatic intraepithelial neoplasia (PanIN), and resulted in the accumulation of (mannose receptor C type 1) MRC1+, (arginase 1) Arg+ macrophages in the tumor microenvironment. Conversely, absence of a functional Mst1r kinase slowed PanIN initiation, resulted in smaller tumors, prolonged survival and a reduced tumor-associated macrophage content. Mst1r expression was associated with increased production of its ligand Mst1, and in orthotopic models, suppression of Mst1 expression resulted in reduced tumor size, changes in macrophage polarization and enhanced T cell infiltration. This study demonstrates the functional significance of Mst1r during pancreatic cancer initiation and progression. Further, it provides proof of concept that targeting Mst1r can modulate pancreatic cancer growth and the microenvironment. This study provides further rationale for targeting Mst1r as a therapeutic strategy.

Neuroblastoma is a pediatric cancer of the peripheral nervous system in which structural chromosome aberrations are emblematic of aggressive tumors. In this study, we performed an in-depth analysis of somatic rearrangements in two neuroblastoma cell lines and two primary tumors using paired-end sequencing of mate-pair libraries and RNA-seq. The cell lines presented with typical genetic alterations of neuroblastoma and the two tumors belong to the group of neuroblastoma exhibiting a profile of chromothripsis. Inter and intra-chromosomal rearrangements were identified in the four samples, allowing in particular characterization of unbalanced translocations at high resolution. Using complementary experiments, we further characterized 51 rearrangements at the base pair resolution that revealed 59 DNA junctions. In a subset of cases, complex rearrangements were observed with templated insertion of fragments of nearby sequences. Although we did not identify known particular motifs in the local environment of the breakpoints, we documented frequent microhomologies at the junctions in both chromothripsis and non-chromothripsis associated breakpoints. RNA-seq experiments confirmed expression of several predicted chimeric genes and genes with disrupted exon structure including ALK, NBAS, FHIT, PTPRD and ODZ4. Our study therefore indicates that both non-homologous end joining-mediated repair and replicative processes may account for genomic rearrangements in neuroblastoma. RNA-seq analysis allows the identification of the subset of abnormal transcripts expressed from genomic rearrangements that may be involved in neuroblastoma oncogenesis.

Recently, activating mutations of the full length ALK receptor, with two hot spots at positions F1174 and R1275, have been characterized in sporadic cases of neuroblastoma. Here, we report similar basal patterns of ALK phosphorylation between the neuroblastoma IMR-32 cell line, which expresses only the wild-type receptor (ALK(WT)), and the SH-SY5Y cell line, which exhibits a heterozygous ALK F1174L mutation and expresses both ALK(WT) and ALK(F1174L) receptors. We demonstrate that this lack of detectable increased phosphorylation in SH-SY5Y cells is a result of intracellular retention and proteasomal degradation of the mutated receptor. As a consequence, in SH-SY5Y cells, plasma membrane appears strongly enriched for ALK(WT) whereas both ALK(WT) and ALK(F1174L) were present in intracellular compartments. We further explored ALK receptor trafficking by investigating the effect of agonist and antagonist mAb (monoclonal antibodies) on ALK internalization and down-regulation, either in SH-SY5Y cells or in cells expressing only ALK(WT). We observe that treatment with agonist mAbs resulted in ALK internalization and lysosomal targeting for receptor degradation. In contrast, antagonist mAb induced ALK internalization and recycling to the plasma membrane. Importantly, we correlate this differential trafficking of ALK in response to mAb with the recruitment of the ubiquitin ligase Cbl and ALK ubiquitylation only after agonist stimulation. This study provides novel insights into the mechanisms regulating ALK trafficking and degradation, showing that various ALK receptor pools are regulated by proteasome or lysosome pathways according to their intracellular localization.

BackgroundMultiple clinical trials investigating the combination of immunotherapy (IO) with antibody drug conjugates (ADC), with or without concurrent chemotherapy, are underway and showing promising results. Mechanism-based triple combination therapies utilizing ADC, IO and a third agent offer an opportunity for additional patient benefit. We investigated the antitumor efficacy of the B7-H4 targeting topoisomerase ADC puxitatug samrotecan (Puxi-sam), the PD1/TIGIT targeting, Fc-reduced monovalent bispecific antibody rilvegostomig and the PARP1-selective inhibitor (PARP1i) saruparib in combination in experimental cancer models.MethodsA 3D tumor spheroid model was generated using RL95-2 endometrial cancer cells and tumor reactive T cells primed on HLA-A24 restricted survivin/BIRC5 tumor antigen peptides or RL95-2 whole cell lysates. Syngeneic MC38 tumor cell lines were engineered to stably express human B7-H4. Tumor cells were implanted in wild-type C57BL6 mice and when tumors reached between 100-200 mm3, mice were randomized to receive either monotherapy doublet or triple combination therapy. Puxi-sam was administered as a single i.v. dose at 7 mg/kg, saruparib was administered orally daily for 21 days at 0.1 mg/kg and the murine surrogate of rilvegostomig was administered twice weekly i.p. at 10 mg/kg. A subset of mice had tumors harvested at 11 days post onset of dosing for pharmacodynamic evaluation by flow cytometry.ResultsIn vitro treatment of endometrial spheroid-T cell co-cultures with ADC-IO, ADC-PARPi and triplet combination induced additive tumor spheroid growth inhibition. In the fully immunocompetent syngeneic mouse model, the combination of Puxi-sam and rilvegostomig induced significant tumor growth inhibition (p<0.0001) and improved survival compared to monotherapies. The addition of saruparib further enhanced the anti-tumor activity and resulted in a majority of animals having complete and durable tumor regression. A follow up pharmacodynamic study assessed a cohort of tumors collected 11 days post treatment initiation. Flow cytometry of the dissociated tumors revealed a greater than 2-fold increase in intratumoral CD3 positive T cells, including a greater than 3-fold increase in cytotoxic effector CD8 positive T cells after triplet therapy compared to untreated mouse tumors. Further, there were decreased intratumoral myeloid derived suppressor cells (MDSCs) and increased macrophages expressing the co-stimulatory molecule CD86 in the triplet therapy group compared to the untreated group.ConclusionsRobust anti-tumor activity and tumor immune microenvironment modulation can be achieved with the combination of patuxitug-samrotecan, saruparib and rilvegostomig.Ethics ApprovalThe studies described were approved by the Institutional Animal Care and Use Committee of Astrazeneca under protocol AUP22-25.

Neuroblastoma is a pediatric cancer of the peripheral nervous system in which structural chromosome aberrations are emblematic of aggressive tumors. In this study, we performed an in-depth analysis of somatic rearrangements in two neuroblastoma cell lines and two primary tumors using paired-end sequencing of mate-pair libraries and RNA-seq. The cell lines presented with typical genetic alterations of neuroblastoma and the two tumors belong to the group of neuroblastoma exhibiting a profile of chromothripsis. Inter and intra-chromosomal rearrangements were identified in the four samples, allowing in particular characterization of unbalanced translocations at high resolution. Using complementary experiments, we further characterized 51 rearrangements at the base pair resolution that revealed 59 DNA junctions. In a subset of cases, complex rearrangements were observed with templated insertion of fragments of nearby sequences. Although we did not identify known particular motifs in the local environment of the breakpoints, we documented frequent microhomologies at the junctions in both chromothripsis and non-chromothripsis associated breakpoints. RNA-seq experiments confirmed expression of several predicted chimeric genes and genes with disrupted exon structure including ALK, NBAS, FHIT, PTPRD and ODZ4. Our study therefore indicates that both non-homologous end joining-mediated repair and replicative processes may account for genomic rearrangements in neuroblastoma. RNA-seq analysis allows the identification of the subset of abnormal transcripts expressed from genomic rearrangements that may be involved in neuroblastoma oncogenesis.