Name: Video: Cytometer Assays of MPNST Cells Challenged with Therapeutic Agents
Uploaded: 2023-08-25T13:30:00
Description: 96 Views. Cytometer Assays of MPNST Cells Challenged with Therapeutic Agents

cytometer assays of mpnst cells challenged with therapeutic agents

Genome-Scale Screening to Identify and Compare Therapeutic Targets in Tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are highly aggressive spindle cell neoplasms that arise in association with the tumor susceptibility syndrome neurofibromatosis type 1 (NF1), sporadically in the general population and at sites of previous radiotherapy1,2,3. NF1 patients are born with a wild-type copy of the NF1 tumor suppressor gene and a second NF1 allele with a loss-of-function mutation. This state of haploinsufficiency renders NF1 patients susceptible to a second loss-of-function mutation in their wild-type NF1 gene, which triggers tumorigenesis. When this &#34;second hit&#34; NF1 mutation occurs in a cell in the Schwann cell lineage, the resulting tumor is either a dermal neurofibroma arising in the skin or a plexiform neurofibroma that develops in large nerves or nerve plexuses. Although the pathology of dermal and plexiform neurofibromas is identical, their biologic behavior is quite different-although both dermal and plexiform neurofibromas are benign, only plexiform neurofibromas can undergo transformation and give rise to MPNSTs. In addition to the loss of neurofibromin, the Ras GTPase-activating protein encoded by the NF1 gene, MPNSTs carry mutations of multiple other tumor suppressor genes, including TP534,5,6,7, CDKN2A8,9, and PTEN10, mutations of genes encoding components of&#160;polycomb repressive complex 211,12 (PRC2; the SUZ12 and EED genes) and aberrant expression of receptor tyrosine kinases1,2. Mutations of NF1 and the other genes noted above are also present in sporadic and radiation-induced MPNSTs11,12.
While these advances in our understanding of the genomic abnormalities in MPNSTs have been invaluable for understanding their pathogenesis, they have not yet resulted in the development of effective new therapies for MPNSTs. A major barrier impeding the development of new treatments is the fact that MPNSTs are rare cancers. Because of this, it is difficult to obtain the large number of patient samples that are required for global analyses defining key driver mutations such as those undertaken by The Cancer Genome Atlas (TCGA). In our experience, accumulating even a modest number of human MPNST specimens can take years. To overcome such limitations, many investigators studying other rare cancer types have turned to the use of cross-species comparative oncogenomics to identify essential driver gene mutations, define the essential cytoplasmic signaling pathways in their tumor of interest, and identify new therapeutic targets. Since the signaling pathways that are essential for tumorigenesis are highly conserved between humans and other vertebrate species, applying functional genomics approaches such as genome-scale shRNA screens can be an effective means of identifying these new driver mutations, signaling pathways, and therapeutic targets13,14,15,16,17,18,19, particularly when studying rare human tumor types that are available in limiting numbers20.
In the methodologies presented here, we describe this approach to performing genomic profiling in human MPNST cell lines and early passage MPNST cultures derived from P0-GGF&#946;3 mice, a genetically engineered mouse model (GEM) in which Schwann cell-specific overexpression of the growth factor neuregulin-1 (NRG1) promotes the pathogenesis of plexiform neurofibromas and their subsequent progression to MPNSTs21,22,23. The first step in this approach is to identify candidate driver genes in P0-GGF&#946;3 MPNSTs, human MPNST cell lines, and surgically resected human MPNSTs. To functionally validate the signaling pathways affected by these mutations, we then use genome-scale shRNA screens to identify the genes required for proliferation and survival in human and mouse MPNST cell lines. After identifying the genes required for proliferation and survival, we then identify the druggable gene products within the collection of &#34;hits&#34; using the Drug Gene Interaction Database. We also compare the &#34;hits&#34; in human and mouse MPNST cells, to determine whether the GEM model and human MPNSTs demonstrate similar dependence on the same genes and signaling pathways. Identifying overlaps in the genes required for proliferation and survival and the affected signaling pathways serves as a means of validating the P0-GGF&#946;3 mouse model at a molecular level. This approach also emphasizes the effectiveness of combining human and mouse screens to identify novel therapeutic targets, where the mouse model can serve as a complement to the human screens. The value of this cross-species approach is particularly apparent when looking for therapeutic targets in rare tumors, where human tumors and cell lines are difficult to obtain.

Author Spotlight: Finding New Therapeutic Targets for Malignant Peripheral Nerve Sheath Tumor Through Genome-Scale shRNA Screens 

Genetic Profiling and Genome-Scale Dropout Screening to Identify Therapeutic Targets in Mouse Models of Malignant Peripheral Nerve Sheath Tumor

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Cytometer Assays of MPNST Cells Challenged with Therapeutic Agents

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Research

JoVE Journal

Cancer Research

96 Views. Cytometer Assays of MPNST Cells Challenged with Therapeutic Agents

Video: Cytometer Assays of MPNST Cells Challenged with Therapeutic Agents

Malignant Peripheral Nerve Sheath Tumors (MPNSTs) are derived from Schwann cells or their precursors. In patients with the tumor susceptibility syndrome neurofibromatosis type 1 (NF1), MPNSTs are the most common malignancy and the leading cause of death. These rare and aggressive soft-tissue sarcomas offer a stark future, with 5-year disease-free survival rates of 34-60%. Treatment options for individuals with MPNSTs are disappointingly limited, with disfiguring surgery being the foremost treatment option. Many once-promising therapies such as tipifarnib, an inhibitor of Ras signaling, have failed clinically. Likewise, phase II clinical trials with erlotinib, which targets the epidermal growth factor (EFGR), and sorafenib, which targets the vascular endothelial growth factor receptor (VEGF), platelet-derived growth factor receptor (PDGF), and Raf, in combination with standard chemotherapy, have also failed to produce a response in patients. 
In recent years, functional genomic screening methods combined with genetic profiling of cancer cell lines have proven useful for identifying essential cytoplasmic signaling pathways and the development of target-specific therapies. In the case of rare tumor types, a variation of this approach known as cross-species comparative oncogenomics is increasingly being used to identify novel therapeutic targets. In cross-species comparative oncogenomics, genetic profiling and functional genomics are performed in genetically engineered mouse (GEM) models and the results are then validated in the rare human specimens and cell lines that are available. 
This paper describes how to identify candidate driver gene mutations in human and mouse MPNST cells using whole exome sequencing (WES). We then describe how to perform genome-scale shRNA screens to identify and compare critical signaling pathways in mouse and human MPNST cells and identify druggable targets in these pathways. These methodologies provide an effective approach to identifying new therapeutic targets in a variety of human cancer types.

We have developed a cross-species comparative oncogenomics approach utilizing genomic analyses and functional genomic screens to identify and compare therapeutic targets in tumors arising in genetically engineered mouse models and the corresponding human tumor type.

Malignant Peripheral Nerve Sheath Tumors (MPNSTs) are derived from Schwann cells or their precursors. In patients with the tumor susceptibility syndrome ...