Project description:Whole exome sequencing of a cell line derived from an Rb1 and Trp53 genetically engineered mouse model (GEMM) to assess the baseline copy number landscape of the cells prior to experimental modification.
Project description:Myc expression cooperates with Rb1 and Trp53 loss in mouse lungs to generate rapid, aggressive, highly metastatic and neuroendocrine-low tumors that are similar to human variant subset of SCLC with high NEUROD1 expression. Targeted drug screening reveals that mouse and human MYC-driven SCLC are vulnerable to Aurora kinase inhibition in combination with chemotherapy in vivo.
Project description:In cells derived from a genetically engineered Rb1 and Trp53 loss mouse model of SCLC (RP) expression of one of the three MYC family members induced from the endogenous locus using CRISPR activation. Cells were first stably transfected with the lenti-MS2-p65-HSF1 activator plasmid. Respective sgRNAs targeting either Myc, Mycl or MYCN were then cloned into the lentiSAMv2 system and transfected separately into the MS2-p65-HSF1 cells using lentiviral delivery.
Project description:The canonical model of small cell lung cancer (SCLC) depicts tumors arising from dual inactivation of TP53 and RB1. However, many genomic studies have persistently identified tumors with no RB1 mutations. Here, we examined RB1 protein expression and function in SCLC. RB1 expression was examined by immunohistochemical analysis of 62 human SCLC tumors. These studies showed that ~14% of SCLC tumors expressed abundant RB1 protein, which is associated with neuroendocrine (NE) gene expression and is enriched in YAP1 expression, but no other lineage proteins that stratify SCLC. SCLC cells and xenograft tumors with RB1 protein expression were sensitive to growth inhibition by the CDK4/6 inhibitor palbociclib, and this inhibition was shown to be dependent on RB1 expression by CRISPR knockout. Furthermore, a patient with biopsy-validated wt RB1 SCLC who received the CDK4/6 inhibitor abemaciclib demonstrated a dramatic decrease in mutant TP53 ctDNA allelic fraction from 62.1% to 0.4% and decreased tumor mass on CT scans. Importantly, immunohistochemistry of the diagnostic biopsy specimen showed RB1 positivity. Finally, we identified a transcriptomics-based RB1 loss-of-function signature that discriminates between SCLC cells with or without RB1 protein expression and validated it in the patient who was responsive to abemaciclib, suggesting its potential use to predict CDK4/6 inhibitor response in SCLC patients. Our study demonstrates that RB1 protein is an actionable target in a subgroup of SCLC, a cancer that exhibits no currently targetable mutations.
Project description:In RP (Rb1fl/fl;Trp53fl/fl) mice, SCLC phenotype tumors were established eight months after intratracheal injection of an adenovirus carrying Cre recombinase, driven by the CMV promoter. Primary lung tumors and metastatic liver tumors from the same mouse were collected for sequencing, resulting in a dataset.A similarity analysis was conducted between this dataset and the subpopulations with high and low autophagic flux in our RPΔG (Rb1fl/fl;Trp53fl/fl;GFP-LC3-RFP-LC3△G) mice. The analysis revealed that the subpopulation with high autophagic flux exhibited greater similarity to the metastatic data.
Project description:ASCL1 is a neuroendocrine-lineage-specific oncogenic driver of small cell lung cancer (SCLC), highly expressed in a significant fraction of tumors. However, ~25% of human SCLC are ASCL1-low and associated with low-neuroendocrine fate and high MYC expression. Using genetically-engineered mouse models (GEMMs), we show that alterations in Rb1/Trp53/Myc in the mouse lung induce an ASCL1+ state of SCLC in multiple cells of origin. Genetic depletion of ASCL1 in MYC-driven SCLC dramatically inhibits tumor initiation and progression to the NEUROD1+ subtype of SCLC. Surprisingly, ASCL1 loss promotes a SOX9+ mesenchymal/neural-crest-stem-like state and the emergence of bone and more rarely, cartilaginous tumors. ASCL1 is critical for expression of key lineage-related transcription factors NKX2-1, FOXA2, and INSM1, and represses regulators of Hippo, Wnt and Notch developmental pathways in vivo. ASCL1 also represses SOX9 expression in human SCLC cells, suggesting a conserved function for ASCL1. Here, we utilize single-cell RNA sequencing to capture transcriptomic signatures of RPM (Rb1/Trp53/Myc), RPR2 (Rb1/Trp53/Rbl2), and RPMA (Rb1/Trp53/Myc/Ascl1) GEMM tumors to support our conclusion that in MYC-driven SCLC, ASCL1 promotes neuroendocrine fate and represses the emergence of SOX9+ non-endodermal stem-like or mesenchymal fates. These data were integrated with 4 additional invasive RPM tumors from NCBI GEO: GSE149180.
Project description:Small Cell Lung Cancer (SCLC) is the most aggressive type of lung cancer with early metastatic dissemination and invariable development of resistant disease for which no effective treatment is available to date. Mouse models of SCLC based on inactivation of Rb1 and Trp53 developed earlier showed frequent amplifications of two transcription factor genes: Nfib and Mycl. Overexpression of Nfib but not Mycl in SCLC mouse results in an enhanced and altered metastatic profile, and appears to be associated with genomic instability. NFIB promotes tumor heterogeneity with the concomitant expansive growth of poorly differentiated, highly proliferative, and invasive tumor cell populations. Consistent with the mouse data, NFIB expression in high-grade human neuroendocrine carcinomas correlates with advanced stage III/IV disease warranting its further assessment as a potentially valuable progression marker in a clinical setting. Genomic DNA from mouse small cell lung tumor samples was analyzed by mate pair sequencing and low coverage sequencing. And RNA from Nfib overexpressing mouse small cell lung cancer cell lines was further analyzed for high quality RNA profiles using Illumina Hiseq2500. This series contains only RNA-seq data.
Project description:Targeting cell cycle checkpoints has emerged as a promising strategy in cancer therapy, yet single-agent inhibitors often fail due to compensatory mechanisms. Here, we demonstrate that co-inhibition of ATR (RP-3500) and PKMYT1 (RP-6306) induces synthetic lethality in Rb1-deficient breast cancers by disrupting both S/G2 and G2/M checkpoints, resulting in replication stress, premature mitotic entry, and DNA damage accumulation. In vitro, Rb1-deficient breast cancer cell lines exhibited marked apoptosis and loss of clonogenic potential, whereas Rb1-proficient models remained largely resistant to combination treatment. Genetic manipulation of Rb1 confirmed this dependency: Rb1 knockdown sensitized resistant models, and overexpression conferred protection. In vivo, patient-derived xenograft (PDX) models recapitulated these findings. Rb1-deficient tumors underwent complete regression, while Rb1-proficient tumors showed limited response with RP-3500/RP-6306 treatment. Combination therapy was well tolerated in vivo, without significant toxicity or weight loss. Biomarker analysis revealed increased γH2AX and reduced Ki67 staining exclusively in Rb1-deficient PDX models, underscoring the specificity of this response. Mechanistically, Rb1 loss impaired double-strand DNA repair by attenuating homologous recombination and non-homologous end joining, leading to replication fork collapse, chromosomal instability, and mitotic catastrophe. Proteogenomic analysis identified JNK/p38 stress response pathway activation as a key driver of apoptosis following ATR/PKMYT1 inhibition in Rb1-deficient cells. Clinically, analysis of stage IV breast cancer patient datasets revealed that Rb1-low tumors display reduced DNA repair pathway activity and are enriched in triple-negative and CDK4/6 inhibitor-resistant luminal breast cancers. These findings establish Rb1 loss as a functional biomarker for ATR/PKMYT1-targeted therapy, offering a precision treatment strategy for advanced breast cancers.
Project description:Small Cell Lung Cancer (SCLC) is the most aggressive type of lung cancer with early metastatic dissemination and invariable development of resistant disease for which no effective treatment is available to date. Mouse models of SCLC based on inactivation of Rb1 and Trp53 developed earlier showed frequent amplifications of two transcription factor genes: Nfib and Mycl. Overexpression of Nfib but not Mycl in SCLC mouse results in an enhanced and altered metastatic profile, and appears to be associated with genomic instability. NFIB promotes tumor heterogeneity with the concomitant expansive growth of poorly differentiated, highly proliferative, and invasive tumor cell populations. Consistent with the mouse data, NFIB expression in high-grade human neuroendocrine carcinomas correlates with advanced stage III/IV disease warranting its further assessment as a potentially valuable progression marker in a clinical setting.