Genomic and clinical characterization of a familial GIST kindred intolerant to imatinib.

Familial gastrointestinal stromal tumors (GIST) are rare. We present a kindred with multiple family members affected with multifocal GIST who underwent whole genome sequencing of the germline and tumor. Affected individuals with GIST harbored a germline variant found within exon 13 of the KIT gene (c.1965T>G; p.Asn655Lys, p.N655K) and a variant in the MSR1 gene (c.877 C > T; p.Arg293*, pR293X). Multifocal GISTs in the proband and her mother were treated with preoperative imatinib, which resulted in severe intolerance. The clinical features of multifocal GIST, cutaneous mastocytosis, allergies, and gut motility disorders seen in the affected individuals may represent manifestations of the multifunctional roles of KIT in interstitial cells of Cajal or mast cells and/or may be suggestive of additional molecular pathways which can contribute to tumorigenesis.

PERP, an apoptosis-associated target of p53, is a novel member of the PMP-22/gas3 family.

The p53 tumor suppressor activates either cell cycle arrest or apoptosis in response to cellular stress. Mouse embryo fibroblasts (MEFs) provide a powerful primary cell system to study both p53-dependent pathways. Specifically, in response to DNA damage, MEFs undergo p53-dependent G(1) arrest, whereas MEFs expressing the adenovirus E1A oncoprotein undergo p53-dependent apoptosis. As the p53-dependent apoptosis pathway is not well understood, we sought to identify apoptosis-specific p53 target genes using a subtractive cloning strategy. Here, we describe the characterization of a gene identified in this screen, PERP, which is expressed in a p53-dependent manner and at high levels in apoptotic cells compared with G(1)-arrested cells. PERP induction is linked to p53-dependent apoptosis, including in response to E2F-1-driven hyperproliferation. Furthermore, analysis of the PERP promoter suggests that PERP is directly activated by p53. PERP shows sequence similarity to the PMP-22/gas3 tetraspan membrane protein implicated in hereditary human neuropathies such as Charcot-Marie-Tooth. Like PMP-22/gas3, PERP is a plasma membrane protein, and importantly, its expression causes cell death in fibroblasts. Taken together, these data suggest that PERP is a novel effector of p53-dependent apoptosis.