modeling-osteosarcoma-using-li-fraumeni-syndrome-patient-derived

Modeling Osteosarcoma Using Li-Fraumeni Syndrome Patient-derived Induced Pluripotent Stem Cells

Li-Fraumeni syndrome (LFS) is an autosomal dominant hereditary cancer disorder. Patients with LFS are predisposed to a various type of tumors, including ...

The University of Texas Health Science Center at Houston

The University of Texas MD Anderson Cancer Center UTHealth

MAX dimerization protein 1 (MAD1) is a transcription suppressor that antagonizes MYC-mediated transcription activation, and the inhibition mechanism occurs mainly through the competition of target genes' promoter MYC binding sites by MAD1. The promoter binding proteins switch between MYC and MAD1 affects cell proliferation and differentiation. However, little is known about MAD1's regulation process in cancer cells. Here, we present evidence that AKT inhibits MAD1-mediated transcription repression by physical interaction with and phosphorylation of MAD1. Phosphorylation reduces the binding affinity between MAD1 and its target genes' promoter and thereby abolishes its transcription suppression function. Mutation of the phosphorylation site from serine to alanine rescues the DNA-binding ability in the presence of activated AKT. In addition, AKT inhibits MAD1-mediated target genes (hTERT and ODC) transcription repression and promotes cell cycle and cell growth. However, mutated S145A MAD1 abrogates the inhibition by AKT. Thus, our results suggest that phosphorylation of MAD1 by AKT inhibits MAD1-mediated transcription suppression and subsequently activates the transcription of MAD1 target genes.

The suppression of MAD1 by AKT-mediated phosphorylation activates MAD1 target genes transcription.

The Kruppel-like transcription factor zinc finger protein (ZNF)217 (mouse homolog ZFP217) contributes to tumorigenesis by dysregulating gene expression programs. The newly discovered molecular function of ZFP217 in controlling N6-methyladenosine (mA) deposition in embryonic stem cells (ESCs) sheds new light on the role of this transcription factor in tumor development.

ZNF217/ZFP217 Meets Chromatin and RNA.

The elucidation of cancer pathogenesis has been hindered by limited access to patient samples, tumor heterogeneity and the lack of reliable model organisms. Characterized by their ability to self-renew indefinitely and differentiate into all cell lineages of an organism, pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), provide a powerful and unlimited source to generate differentiated cells that can be used to study disease biology, facilitate drug discovery and development, and provide key insights for developing personalized therapies. This article reviews the recent developments and technologies converting PSCs into clinically relevant model systems for cancer research.

Modeling Cancer with Pluripotent Stem Cells.

The Histogenesis of Ewing Sarcoma.

Notch signaling plays a role in specifying a cardiac fate but the downstream effectors remain unknown. In this study we implicate the Notch downstream effector HES5 in cardiogenesis. We show transient Hes5 expression in early mesoderm of gastrulating embryos and demonstrate, by loss and gain-of-function experiments in mouse embryonic stem cells, that HES5 favors cardiac over primitive erythroid fate. Hes5 overexpression promotes upregulation of the cardiac gene Isl1, while the hematopoietic regulator Scl is downregulated. Moreover, whereas a pulse of Hes5 instructs cardiac commitment, sustained expression after lineage specification impairs progression of differentiation to contracting cardiomyocytes. These findings establish a role for HES5 in cardiogenesis and provide insights into the early cardiac molecular network.

Transient HES5 Activity Instructs Mesodermal Cells toward a Cardiac Fate.

Rare hereditary disorders provide unequivocal evidence of the importance of genes in human disease pathogenesis. Familial syndromes that predispose to osteosarcomagenesis are invaluable in understanding the underlying genetics of this malignancy. Recently, patient-derived induced pluripotent stem cells (iPSCs) have been successfully utilized to model Li-Fraumeni syndrome (LFS)-associated bone malignancy, demonstrating that iPSCs can serve as an in vitro disease model to elucidate osteosarcoma etiology. We provide here an overview of osteosarcoma predisposition syndromes and review recently established iPSC disease models for these familial syndromes. Merging molecular information gathered from these models with the current knowledge of osteosarcoma biology will help us to gain a deeper understanding of the pathological mechanisms underlying osteosarcomagenesis and will potentially aid in the development of future patient therapies.

Osteosarcoma: Molecular Pathogenesis and iPSC Modeling.

Li-Fraumeni syndrome (LFS) is a rare hereditary autosomal dominant cancer disorder. Germline mutations in TP53, the gene encoding p53, are responsible for most cases of LFS. TP53 is also the most commonly mutated gene in human cancers. Because inhibition of mutant p53 is considered to be a promising therapeutic strategy to treat these diseases, LFS provides a perfect genetic model to study p53 mutation-associated malignancies as well as to screen potential compounds targeting oncogenic p53. In this review we briefly summarize the biology of LFS and current understanding of the oncogenic functions of mutant p53 in cancer development. We discuss the strengths and limitations of current LFS disease models, and touch on existing compounds targeting oncogenic p53 and in vitro clinical trials to develop new ones. Finally, we discuss how recently developed methodologies can be integrated into the LFS induced pluripotent stem cell (iPSC) platform to develop precision cancer therapy.

Li-Fraumeni Syndrome Disease Model: A Platform to Develop Precision Cancer Therapy Targeting Oncogenic p53.

The Retinoblastoma 1 (RB1) tumor suppressor, a member of the Retinoblastoma gene family, functions as a pocket protein for the functional binding of E2F transcription factors. About 1/3 of retinoblastoma patients harbor a germline RB1 mutation or deletion, leading to the development of retinoblastoma. Here, we demonstrate generation of a heterozygous deletion of the RB1 gene in the H1 human embryonic stem cell line using CRISPR/Cas9 nickase genome editing. The RB1 heterozygous knockout H1 cell line shows a normal karyotype, maintains a pluripotent state, and is capable of differentiation to the three germline layers.

Generation of human embryonic stem cell line with heterozygous RB1 deletion by CRIPSR/Cas9 nickase.

The tumor suppressor gene TP53 is the most frequently mutated gene in human cancers. Many hot-spot mutations of TP53 confer novel functions not found in wild-type p53 and contribute to tumor development and progression. We report on the generation of a H1 human embryonic stem cell line carrying a homozygous TP53 R282W mutation using TALEN-mediated genome editing. The generated cell line demonstrates normal karyotype, maintains a pluripotent state, and is capable of generating a teratoma in vivo containing tissues from all three germ layers.

A homozygous p53 R282W mutant human embryonic stem cell line generated using TALEN-mediated precise gene editing.

Genetic mutations in TP53 contribute to multiple human cancers. Here we report the generation of a H1-p53(R248W/R248W) human embryonic stem cell line harboring a homozygous TP53 R248W mutation created by TALEN-mediated precise gene editing. The H1-p53(R248W/R248W) cell line maintains a normal karyotype, robust pluripotency gene expression, and the potential to differentiate to the three germ layers.

Article	Year
The suppression of MAD1 by AKT-mediated phosphorylation activates MAD1 target genes transcription. Molecular carcinogenesis\| PubMed ID: 19526459	2009
ZNF217/ZFP217 Meets Chromatin and RNA. Trends in biochemical sciences\| PubMed ID: 27519282	2016
Modeling Cancer with Pluripotent Stem Cells. Trends in cancer\| PubMed ID: 27722205	2016
The Histogenesis of Ewing Sarcoma. Cancer reports and reviews\| PubMed ID: 28626837	2017
Transient HES5 Activity Instructs Mesodermal Cells toward a Cardiac Fate. Stem cell reports\| PubMed ID: 28648899	2017
Osteosarcoma: Molecular Pathogenesis and iPSC Modeling. Trends in molecular medicine\| PubMed ID: 28735817	2017
Li-Fraumeni Syndrome Disease Model: A Platform to Develop Precision Cancer Therapy Targeting Oncogenic p53. Trends in pharmacological sciences\| PubMed ID: 28818333	2017
Generation of human embryonic stem cell line with heterozygous RB1 deletion by CRIPSR/Cas9 nickase. Stem cell research\| PubMed ID: 29414415	2018
A homozygous p53 R282W mutant human embryonic stem cell line generated using TALEN-mediated precise gene editing. Stem cell research\| PubMed ID: 29414603	2018
Establishment of a human embryonic stem cell line with homozygous TP53 R248W mutant by TALEN mediated gene editing. Stem cell research\| PubMed ID: 29730572	2018

Dung-Fang Lee

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