Explore the vast range of titles available.

Ovarian cancer (OC) is a heterogeneous disease usually diagnosed at a late stage. Experimental in vitro models that faithfully capture the hallmarks and tumor heterogeneity of OC are limited and hard to establish. We present a protocol that enables efficient derivation and long-term expansion of OC organoids. Utilizing this protocol, we have established 56 organoid lines from 32 patients, representing all main subtypes of OC. OC organoids recapitulate histological and genomic features of the pertinent lesion from which they were derived, illustrating intra- and interpatient heterogeneity, and can be genetically modified. We show that OC organoids can be used for drug-screening assays and capture different tumor subtype responses to the gold standard platinum-based chemotherapy, including acquisition of chemoresistance in recurrent disease. Finally, OC organoids can be xenografted, enabling in vivo drug-sensitivity assays. Taken together, this demonstrates their potential application for research and personalized medicine.A biobank of ovarian cancer organoids recapitulates the histopathological and molecular hallmarks of patient tumors and provides a resource for preclinical research.

Much controversy surrounds the cell-of-origin of mutant K-Ras (K-RasG12D)–induced lung adenocarcinoma. To shed light on this issue, we have used technology that enables us to conditionally target K-RasG12D expression in Surfactant Protein C (SPC) ⁺ alveolar type 2 cells and in Clara cell antigen 10 (CC10) ⁺ Clara cells by use of cell-type–restricted recombinant Adeno-Cre viruses. Experiments were performed both in the presence and absence of the tumor suppressor gene p53, enabling us to assess what effect the cell-of-origin and the introduced genetic lesions have on the phenotypic characteristics of the resulting adenocarcinomas. We conclude that both SPC-expressing alveolar type 2 cells and CC10-expressing Clara cells have the ability to initiate malignant transformation following the introduction of these genetic alterations. The lungs of K-Ras ˡᵒˣ–Sᵗᵒᵖ–ˡᵒˣ–ᴳ¹²ᴰ/⁺ and K-Ras ˡᵒˣ–Sᵗᵒᵖ–ˡᵒˣ–ᴳ¹²ᴰ/⁺;tumor suppressor gene Trp53 F/F mice infected with Adeno5–SPC–Cre and Adeno5–CC10–Cre viruses displayed differences in their tumor spectrum, indicating distinct cellular routes of tumor initiation. Moreover, using a multicolor Cre reporter line, we demonstrate that the resulting tumors arise from a clonal expansion of switched cells. Taken together, these results indicate that there are multiple cellular paths to K-RasG12D–induced adenocarcinoma and that the initiating cell influences the histopathological phenotype of the tumors that arise.

Background The majority of BRCA1 -mutant breast cancers are characterized by a triple-negative phenotype and a basal-like molecular subtype, associated with aggressive clinical behavior. Current treatment options are limited, highlighting the need for the development of novel targeted therapies for this tumor subtype. Methods Our group previously showed that EZH2 is functionally relevant in BRCA1-deficient breast tumors and blocking EZH2 enzymatic activity could be a potent treatment strategy. To validate the role of EZH2 as a therapeutic target and to identify new synergistic drug combinations, we performed a high-throughput drug combination screen in various cell lines derived from BRCA1-deficient and -proficient mouse mammary tumors. Results We identified the combined inhibition of EZH2 and the proximal DNA damage response kinase ATM as a novel synthetic lethality-based therapy for the treatment of BRCA1-deficient breast tumors. We show that the combined treatment with the EZH2 inhibitor GSK126 and the ATM inhibitor AZD1390 led to reduced colony formation, increased genotoxic stress, and apoptosis-mediated cell death in BRCA1-deficient mammary tumor cells in vitro. These findings were corroborated by in vivo experiments showing that simultaneous inhibition of EZH2 and ATM significantly increased anti-tumor activity in mice bearing BRCA1-deficient mammary tumors. Conclusion Taken together, we identified a synthetic lethal interaction between EZH2 and ATM and propose this synergistic interaction as a novel molecular combination for the treatment of BRCA1 -mutant breast cancer.

Human cancers modeled in Genetically Engineered Mouse Models (GEMMs) can provide important mechanistic insights into the molecular basis of tumor development and enable testing of new intervention strategies. The inherent complexity of these models, with often multiple modified tumor suppressor genes and oncogenes, has hampered their use as preclinical models for validating cancer genes and drug targets. In our newly developed approach for the fast generation of tumor cohorts we have overcome this obstacle, as exemplified for three GEMMs; two lung cancer models and one mesothelioma model. Three elements are central for this system; (i) The efficient derivation of authentic Embryonic Stem Cells (ESCs) from established GEMMs, (ii) the routine introduction of transgenes of choice in these GEMM‐ESCs by Flp recombinase‐mediated integration and (iii) the direct use of the chimeric animals in tumor cohorts. By applying stringent quality controls, the GEMM‐ESC approach proofs to be a reliable and effective method to speed up cancer gene assessment and target validation. As proof‐of‐principle, we demonstrate that MycL1 is a key driver gene in Small Cell Lung Cancer. Synopsis The GEMM‐ESC approach describes and validates an improved method for generating mouse cancer models directly from embryonic stem cells. This technology speeds up the generation/modification of mouse models, while minimizing cost and breeding efforts. ESCs cultured in 2i medium show improved pluripotency and display equal genomic stability as ESCs cultured under classic conditions. Chimeric mice generated from GEMM‐ESCs are equally susceptible to tumors as compared to the parental strain, provided the chimeras display coat color contribution upwards of 70%. Experimental cohorts are generated on‐demand in less than 4 months without the need for any breeding. Controlled single copy integration of a transgene in the Col1a1 locus allows for robust reporter and oncogene expression in a mouse model for small cell lung cancer. Archived ESCs with complex genetic traits can serve as an important resource for the generation of new mouse models of cancer or for the validation of candidate cancer genes. Graphical Abstract The GEMM‐ESC approach describes and validates an improved method for generating mouse cancer models directly from embryonic stem cells. This technology speeds up the generation/modification of mouse models, while minimizing cost and breeding efforts.

Somatic hotspot mutations and structural amplifications and fusions that affect fibroblast growth factor receptor 2 (encoded by FGFR2 ) occur in multiple types of cancer 1 . However, clinical responses to FGFR inhibitors have remained variable 1 – 9 , emphasizing the need to better understand which FGFR2 alterations are oncogenic and therapeutically targetable. Here we apply transposon-based screening 10 , 11 and tumour modelling in mice 12 , 13 , and find that the truncation of exon 18 (E18) of Fgfr2 is a potent driver mutation. Human oncogenomic datasets revealed a diverse set of FGFR2 alterations, including rearrangements, E1–E17 partial amplifications, and E18 nonsense and frameshift mutations, each causing the transcription of E18-truncated FGFR2 ( FGFR2 ΔE18 ). Functional in vitro and in vivo examination of a compendium of FGFR2 ΔE18 and full-length variants pinpointed FGFR2 -E18 truncation as single-driver alteration in cancer. By contrast, the oncogenic competence of FGFR2 full-length amplifications depended on a distinct landscape of cooperating driver genes. This suggests that genomic alterations that generate stable FGFR2 ΔE18 variants are actionable therapeutic targets, which we confirmed in preclinical mouse and human tumour models, and in a clinical trial. We propose that cancers containing any FGFR2 variant with a truncated E18 should be considered for FGFR-targeted therapies. Truncation of exon 18 of FGFR2 ( FGFR2 ΔE18 ) is a potent driver mutation in mice and humans, and FGFR-targeted therapy should be considered for patients with cancer expressing stable FGFR2 ΔE18 variants.

In a mouse model of mammary carcinoma, loss of deleted in colorectal cancer (DCC) promotes metastasis formation, and in cell cultures derived from p53-deficient mouse mammary tumours DCC expression controls netrin-1-dependent cell survival, supporting the function of DCC as a context-dependent tumour suppressor that limits survival of disseminated tumour cells. Tumour suppression by DCC protein DCC (deleted in colorectal carcinoma) protein has been identified as a tumour suppressor, absent in many colorectal cancers. But doubts about its function arose because a mouse strain lacking one copy of the gene was shown not to develop spontaneous intestinal tumours, and because many DCC deletions also remove the neighbouring tumour suppressor gene Smad4 . Two groups now confirm that DCC is a tumour suppressor, albeit conditionally, through its ability to induce apoptosis in tumour cells. Castets et al . show that mice in which DCC's apoptosis-inducing activity is genetically silenced develop intestinal neoplasia at low frequency; they develop it at high frequency when they also have a predisposing APC mutation. In a mouse mammary tumour model based on p53 inactivation, Krimpenfort et al . show that loss of DCC promotes metastases, suggesting that when present, it limits survival of disseminated tumour cells. Since its discovery in the early 1990s the deleted in colorectal cancer ( DCC ) gene, located on chromosome 18q21, has been proposed as a tumour suppressor gene as its loss is implicated in the majority of advanced colorectal and many other cancers 1 . DCC belongs to the family of netrin 1 receptors, which function as dependence receptors as they control survival or apoptosis depending on ligand binding. However, the role of DCC as a tumour suppressor remains controversial because of the rarity of DCC-specific mutations and the presence of other tumour suppressor genes in the same chromosomal region. Here we show that in a mouse model of mammary carcinoma based on somatic inactivation of p53, additional loss of DCC promotes metastasis formation without affecting the primary tumour phenotype. Furthermore, we demonstrate that in cell cultures derived from p53-deficient mouse mammary tumours DCC expression controls netrin-1-dependent cell survival, providing a mechanistic basis for the enhanced metastatic capacity of tumour cells lacking DCC. Consistent with this idea, in vivo tumour-cell survival is enhanced by DCC loss. Together, our data support the function of DCC as a context-dependent tumour suppressor that limits survival of disseminated tumour cells.

The response of breast cancer to neoadjuvant chemotherapy (NAC) varies substantially, even when tumours belong to the same molecular or histological subtype 1 . Here we identify the oestrous cycle as an important contributor to this heterogeneity. In three mouse models of breast cancer, we show reduced responses to NAC when treatment is initiated during the dioestrus stage, when compared with initiation during the oestrus stage. Similar findings were observed in retrospective premenopausal cohorts of human patients. Mechanistically, the dioestrus stage exhibits systemic and localized changes, including (1) an increased number of cells undergoing epithelial-to-mesenchymal transition linked to chemoresistance 2 , 3 – 4 and (2) decreased tumour vessel diameter, suggesting potential constraints to drug sensitivity and delivery. In addition, an elevated presence of macrophages, previously associated with chemoresistance induction 5 , characterizes the dioestrus phase. Whereas NAC disrupts the oestrous cycle, this elevated macrophage prevalence persists and depletion of macrophages mitigates the reduced therapy response observed when initiating treatment during dioestrus. Our data collectively demonstrate the oestrous cycle as a crucial infradian rhythm determining chemosensitivity, warranting future clinical studies to exploit optimal treatment initiation timing for enhanced chemotherapy outcomes. In three mouse models of breast cancer, we show reduced responses to neoadjuvant chemotherapy when treatment is initiated during the dioestrus stage, when compared with initiation during the oestrus stage.

Glucocorticoids, such as dexamethasone, are essential for treating severe childhood conditions, including cancer, organ transplantation, and inflammatory disorders. However, their long-term use can impair bone development, posing risks to pediatric bone health, which is vital for lifelong skeletal integrity. A mechanistic insight into how glucocorticoids negatively impact bone could improve decision-making in patient care, thereby improving the quality of life for pediatric cancer patients and survivors. In this study, we aimed to elucidate the molecular mechanisms underlying dexamethasone-induced bone toxicity in developing bones using single-cell transcriptomics. We treated skeletally immature C57BL/6JRj male mice with dexamethasone for 28 days, and assessed the bone architecture with micro-computed tomography, and characterized bone and bone marrow cells from the femurs using single-cell RNA sequencing. Our findings revealed a marked reduction in osteoblast and chondrocyte cell populations and impaired function of pre-osteoblasts. Additionally, dexamethasone adversely affected B cell subsets, significantly depleting early B cell progenitors while allowing some further developed immature B cells to persist. These cellular changes were accompanied by reduced longitudinal bone growth, compromised bone architecture, and increased bone fragility at the highest doses of dexamethasone. Interestingly, unlike observations in adults, dexamethasone did not enhance osteoclast activity in our model. Overall, our study suggests that the adverse effects of dexamethasone on bone development are primarily due to its impact on osteoblastic, chondroblastic, and B cell lineages. This disruption affects the critical signaling crosstalk between the cells necessary for both bone development and hematopoiesis.

The histone methyltransferase DOT1L is emerging as a central epigenetic regulator in immune cells. Loss of DOT1L during development of CD8 T cells in vivo leads to gain of memory-features but has also been reported to compromise CD8 T cell viability and activity. Here, we determined the cell-intrinsic role of DOT1L in mature mouse CD8 T cells. After conditional deletion of Dot1L in vitro, CD8 T cells retained in vivo proliferative capacity and anti-tumor reactivity. Moreover, Dot1L knock-out CD8 T cells showed increased antigen-specific cytotoxicity towards tumor cells in vitro. Mechanistically, loss of DOT1L resulted in an altered cell-identity program with loss of T-cell and gain of NK-cell features. These transcriptional changes were mediated by loss of DOT1L methyltransferase activity in a dose-dependent manner. Our findings show that ablation of DOT1L activity in mature CD8 T cells is well-tolerated and rewires their cell identity towards the NK-cell lineage, concomitantly enhancing intrinsic cytotoxic capacity. biorxiv;2025.01.20.633937v1/UFIG1F1ufig1 Differentiation and identity of cytotoxic T cells depend on the methyltransferase DOT1L DOT1L intrinsically limits the cytotoxic activity of mature CD8 T cells DOT1L prohibits the acquisition of NK cell features in CD8 T cells DOT1L maintains CD8 T cell identity through its catalytic activity in a dose-dependent manner