Project description:To investigate the effect of RB1 biallelic inactivation on drug response, RNA-seq analysis was conducted on xenograft mouse models and HCC cell lines following drug treatment.
Project description:In order to study the mechanism of co-inactivation of RB1 and TP53 in the transformation of lung adenocarcinoma to small cell lung cancer, we established the NCI-H1975 cell line with RB1 knockdown.NCI-H1975 cells were cultured and infected with lentivirus expressing RB1-shRNA (n=3) or pLKO.1-shRNA (n=3), We then performed transcriptome sequencing (RNA-seq) on the above cells.
Project description:Retinoblastoma is a rare childhood cancer of the developing retina. Most retinoblastomas initiate with biallelic inactivation of the RB1 gene through diverse mechanisms including point mutations, nucleotide insertions, deletions, loss of heterozygosity and promoter hypermethylation. Recently, a novel mechanism of retinoblastoma initiation was proposed. Gallie and colleagues discovered that a small proportion of retinoblastomas lack RB1 mutations and had MYCN amplification [1]. In this study, we identified recurrent chromosomal, regional and focal genomic lesions in 94 primary retinoblastomas with their matched normal DNA using SNP 6.0 chips. We also analyzed the RB1 gene mutations and compared the mechanism of RB1 inactivation to the recurrent copy number variations in the retinoblastoma genome. In addition to the previously described focal amplification of MYCN and deletions in RB1 and BCOR, we also identified recurrent focal amplification of OTX2, a transcription factor required for retinal photoreceptor development. We identified 10 retinoblastomas in our cohort that lacked RB1 point mutations or indels. We performed whole genome sequencing on those 10 tumors and their corresponding germline DNA. In one of the tumors, the RB1 gene was unaltered, the MYCN gene was amplified and RB1 protein was expressed in the nuclei of the tumor cells. In addition, several tumors had complex patterns of structural variations and we identified 3 tumors with chromothripsis at the RB1 locus. This is the first report of chromothripsis as a mechanism for RB1 gene inactivation in cancer.
Project description:Inactivation of Pten occurs by multiple mechanisms including epigenetic silencing, point mutations, insertion, and deletion, which are tissue dependent. Although frequent loss of heterozygosity around Pten locus and plausible involvement of epigenetic silencing have been reported in radiation-induced thymic lymphomas, the frequency of Pten inactivation and the spectrum of causal aberrations have not yet been extensively characterized. Here, we assessed the principal mode of inactivation by comprehensively analyzing expression and alterations of Pten gene in 23 radiation-induced thymic lymphomas developed in B6C3F1 mice. We found no evidence for methylation-associated silencing of Pten gene. Instead, we found complex structural abnormalities in 8 lymphomas (35%) that included missense and nonsense mutations, 1- and 3-bp insertions, and focal deletions. Sequencing of deletion breakpoints suggested that illegitimate V(D)J recombination and microhomology-mediated rearrangement were responsible for the focal deletions. Seven out of these 8 lymphomas had biallelic alterations, and 4 of them did not express any Pten protein. These aberrations of Pten were well coincided with downstream Akt phosphorylation on Ser473. In conclusion, Pten inactivation, which is frequently biallelic and is caused by a variety of structural abnormalities but not by epigenetic silencing, is involved in radiation-induced lymphomagenesis. Three thymic lymphomas were analyzed by array-CGH method.
Project description:In order to study the mechanism of co-inactivation of RB1 and TP53 in the transformation of lung adenocarcinoma to small cell lung cancer, we established the NCI-H1975 cell line with RB1 knockdown.NCI-H1975 cells were cultured and infected with lentivirus expressing RB1-shRNA (n=3) or pLKO.1-shRNA (n=3), We then performed transcriptome sequencing (RNA-seq) on the above cells.
Project description:Inactivation of Pten occurs by multiple mechanisms including epigenetic silencing, point mutations, insertion, and deletion, which are tissue dependent. Although frequent loss of heterozygosity around Pten locus and plausible involvement of epigenetic silencing have been reported in radiation-induced thymic lymphomas, the frequency of Pten inactivation and the spectrum of causal aberrations have not yet been extensively characterized. Here, we assessed the principal mode of inactivation by comprehensively analyzing expression and alterations of Pten gene in 23 radiation-induced thymic lymphomas developed in B6C3F1 mice. We found no evidence for methylation-associated silencing of Pten gene. Instead, we found complex structural abnormalities in 8 lymphomas (35%) that included missense and nonsense mutations, 1- and 3-bp insertions, and focal deletions. Sequencing of deletion breakpoints suggested that illegitimate V(D)J recombination and microhomology-mediated rearrangement were responsible for the focal deletions. Seven out of these 8 lymphomas had biallelic alterations, and 4 of them did not express any Pten protein. These aberrations of Pten were well coincided with downstream Akt phosphorylation on Ser473. In conclusion, Pten inactivation, which is frequently biallelic and is caused by a variety of structural abnormalities but not by epigenetic silencing, is involved in radiation-induced lymphomagenesis.
Project description:Recent in vitro studies using RB1+/- fibroblasts and MSCs have shown molecular and functional disruptions without the need for biallelic loss of RB1. However, this was not reflected in the recent in vitro studies employing RB1+/- retinal organoids. To gain further insights into the molecular disruptions in the RB1+/- retinal organoids we performed a high throughput RNA-sequencing analysis.iPSCs were generated from RB1+/+ and RB1+/- Orbital adipose mesenchymal stem cells (OAMSCs) derived from retinoblastoma patients. RB1+/+ and RB1+/- iPSCs were subjected to step-wise retinal differentiation protocol and high throughput RNA-sequencing followed by differential gene expression analysis and Gene set enrichment analysis (GSEA) was performed.The analysis revealed that even though there are no gross observable differences, subtle molecular changes in RB1+/- retinal organoids were observed. We report that there is mild shift from the regular metabolic process of glycolysis to oxidative phosphorylation in the RB1+/- retinal organoids which could be setting a premise for tumorigenesis.
Project description:Retinoblastoma (Rb) is a childhood cancer of the developing retina that begins in utero in response to bi-allelic inactivation of RB1 or MYCN amplification, accounting for up to 1% of all tumours in infancy. To gain insights into the transcriptional events of each state cell transition during Rb development, we developed two Rb models via retinal organoid differentiation of RB1 depleted human embryonic stem cell line (RB1-null hESCs) and RB1patient-specific induced pluripotent (iPSC) line harbouring RB1 biallelic mutation (c.2082delC). Both models were characterised by RB1 depletion and a significant increase in the fraction of proliferating cone precursors (RXRγ+Ki67+), which were defined as cell of origin for Rb by the single cell RNA-Seq analysis. The RB1 depleted retinal organoids displayed similar features to Rb tumours including mitochondrial cristae aberration and rosette-like structures and were able to undergo cell growth in an anchorage-independent manner, indicative of cell transformation in vitro. The patient-specific iPSC model displayed an enhanced reduction of amacrine, horizontal and retinal ganglion cells and an accelerated loss of cone photoreceptor markers during transition towards retinoma and Rb, compared to RB1-null hESC. In both models, the Rb cells of origin, intermediate retinoma and/or Rb cells expressed retinal ganglion and horizontal cell in addition to cone markers, a novel finding, which should help to better identify and eradicate these cells within the tumour mass. Application of Melphalan, Topotecan and TW-37 led to a significant reduction in the fraction of proliferating cone precursors, validating the suitability of these in vitro models for testing novel therapeutics for Rb.
Project description:Acute intermittent porphyria (AIP), caused by heterozygous germline mutations of the heme synthesis pathway enzyme HMBS (hydroxymethylbilane synthase), confers high risk of hepatocellular carcinoma (HCC) development. Yet, the role of HMBS in liver tumorigenesis remains unclear. Here we explore HMBS alterations in a large series of 758 HCC. We identify recurrent bi-allelic HMBS inactivation, both in AIP patients acquiring a second somatic HMBS mutation and in sporadic HCC with two somatic hits. HMBS alterations are enriched in truncative mutations, in particular in splice regions, leading to abnormal transcript structures. Bi-allelic HMBS inactivation results in a massive accumulation of its toxic substrate porphobilinogen and synergizes with CTNNB1 activating mutations, leading to the development of well differentiated tumors with a transcriptomic signature of Wnt/ß-catenin pathway activation and a DNA methylation signature related to ageing. HMBS-inactivated HCC mostly affect females, in absence of fibrosis and classical HCC risk factors. These data identify HMBS as a tumor suppressor gene whose bi-allelic inactivation defines a homogenous clinical and molecular HCC subtype.