Knockdown of DUSP1 and DUSP6, alone or in combination, reduced MPNST cell growth and led to ERK and JNK hyperactivation increasing downstream TP53 and p-ATM.
NGS on 2 tumors revealed (1) 2-copy deletion of NF1, CDKN2A, and SUZ12 and a TP53 mutation with arm-level loss of 17p; and (2) 2-copy deletion of CDKN2A and an NF1 mutation with loss of 17q11, findings characteristic of MPNST.
The frequency of the "TP53-mutated phenotype" warrants explorative studies of stratified treatment strategies in malignant peripheral nerve sheath tumor.
Loss of p16/CDKN2A expression, elevated Ki67 labeling, and extensive nuclear p53 positivity are also features of MPNST that can to some degree already occur in atypical neurofibromatous neoplasms of uncertain biologic potential.
The pathological diagnosis of malignant schwannoma indicated that the p53 expression was strongly positive and vascular endothelial growth factor and Bcl-2 were positive before treatment on protein immunohistochemical staining.
Transgenic mice heterozygous for a Trp53-null allele and overexpressing EGFR in Schwann cells had a significant increase in neurofibroma and grade 3 PNST (MPNST) formation compared with single transgenic controls.
LOH for tp53 occurred in the majority of malignant tumors from brca2 wildtype and heterozygous mutant zebrafish, and most of these were malignant peripheral nerve sheath tumors.
The expression of p53 was correlated with MDM2 amplification because early studies have indicated that MDM2 is rarely amplified in MPNSTs that express p53.
We show that patient-derived GBM and NF1 malignant peripheral nerve sheath tumor (MPNST) lines, as well as tumor lines derived from the Nf1-/+;Trp53-/+ (NPcis) mouse model of astrocytoma and MPNST are highly sensitive to inhibition by schweinfurthin A and its synthetic analogs.
Here we report that malignant peripheral nerve sheath tumors (MPNSTs) that arise in zebrafish as a result of mutations in either ribosomal protein (rp) genes or in p53 are highly aneuploid.
Additional genetic changes, including losses of TP53, RB1, CDKN2A, and of several oncogenes and cell-cycle genes, were found only in the malignant MPNST (region 3).
Cells within certain neurofibroma subtypes subsequently accumulate additional mutations affecting the p19(ARF)-MDM2-TP53 and p16INK4A-Rb signaling cascades, mutations of other as yet unidentified genes, and amplification of growth factor receptor genes, resulting in their transformation into MPNSTs.
Using monoclonal antibodies that we raised to zebrafish p53, we found that cells derived from rp(+/-) MPNSTs are significantly impaired in their ability to produce p53 protein even in the presence of a proteasome inhibitor and gamma-irradiation.
In a previous TP53 analysis carried out on sporadic and NF1-related malignant peripheral nerve sheath tumors, in two cases, we observed the occurrence of C238Y missense mutation, leading to p53 stabilization unexpectedly coupled with immunophenotypic MDM2 overexpression.
Cyclin D1 was absent in four tumors; all except one tumor showed expression of TP53 protein, and three of nine MPNSTs had expression of normal-sized MDM2.
The screening of seven MPNSTs for subtle mutations in the CDKN2A and TP53 genes proved negative, although the screening of 11 MPNSTs detected LOH involving either the TP53 or the CDKN2A gene in a total of four tumors.