Quadruple-Negative GIST Is a Sentinel for Unrecognized Neurofibromatosis Type 1 Syndrome.

PURPOSE: The majority of gastrointestinal stromal tumors (GIST) are driven by KIT, PDGFRA, or, less commonly, BRAF mutations, and SDH gene inactivation is involved in a limited fraction of gastric lesions. However, about 10% of GISTs are devoid of any of such alterations and are poorly responsive to standard treatments. This study aims to shed light on the molecular drivers of quadruple-negative GISTs. EXPERIMENTAL DESIGN: Twenty-two sporadic quadruple-negative GISTs with no prior association with Neurofibromatosis Type 1 syndrome were molecularly profiled for a panel of genes belonging to tyrosine kinase pathways or previously implicated in GISTs. For comparison purposes, 24 GISTs carrying KIT, PDGFRA, or SDH gene mutations were also analyzed. Molecular findings were correlated to clinicopathologic features. RESULTS: Most quadruple-negative GISTs featured intestinal localization, with a female predilection. About 60% (13/22) of quadruple-negative tumors carried NF1 pathogenic mutations, often associated with biallelic inactivation. The analysis of normal tissues, available in 11 cases, indicated the constitutional nature of the NF1 mutation in 7 of 11 cases, unveiling an unrecognized Neurofibromatosis Type 1 syndromic condition. Multifocality and a multinodular pattern of growth were common findings in NF1-mutated quadruple-negative GISTs. CONCLUSIONS: NF1 gene mutations are frequent in quadruple-negative GISTs and are often constitutional, indicating that a significant fraction of patients with apparently sporadic quadruple-negative GISTs are affected by unrecognized Neurofibromatosis Type 1 syndrome. Hence, a diagnosis of quadruple-negative GIST, especially if multifocal or with a multinodular growth pattern and a nongastric location, should alert the clinician to a possible Neurofibromatosis Type 1 syndromic condition. Clin Cancer Res; 23(1); 273-82. ©2016 AACR.

YAP1 acts as oncogenic target of 11q22 amplification in multiple cancer subtypes.

The transcriptional coactivator YAP1 is a critical effector of the human Salvador-Warts-Hippo pathway. Literature data report apparently discrepant results on the carcinogenic role of YAP1, which acts either as oncogene or as tumor suppressor in different in vitro and in vivo models. Furthermore, genomic amplification events of 11q22 locus encompassing YAP1 gene have been detected in multiple tumor types but there is limited direct evidence about the oncogenic role of endogenous YAP1 within in the amplicon. We screened a panel of human tumor samples and cancer cell lines and identified that the YAP1 amplification event is actually present in up to 23% of the cases. We exploited EKVX (lung cancer), CaSki (cervical cancer) and RO82 (thyroid cancer) cell lines harboring both genomic YAP1 amplification and YAP1 protein overexpression, in order to study the effects of downregulation of endogenous YAP1 by RNA-interference strategies. Class comparison analysis of gene expression profiling data identified 707 statistically significantly modulated genes (multivariable global test p-value = 0.002) that were functionally annotated for cell proliferation and cellular movement ontologies. Mechanistic studies of the identified perturbed pathways revealed that YAP1 silencing significantly decreased cell proliferation and cell cycle perturbation associated with upregulation of p21 and p27 cell-cycle inhibitors, reduced cell migration (p<0.048) and anchorage-independent growth (p<0.02). In CaSki cell line, YAP1 silencing induced significantly increased sensitivity and cell-death response to cisplatin treatment (p=0.011) as well as reduction of in-vivo tumorigenic potential (p=0.027). Overall, these results establish that YAP1 is a direct oncogenic target of the 11q22 amplicon in previously unreported cancer types and support the relevance of such genetic aberration in carcinogenesis in a fraction of multiple tumor types.

SMARCB1/INI1 genetic inactivation is responsible for tumorigenic properties of epithelioid sarcoma cell line VAESBJ.

Epithelioid sarcoma is a rare soft tissue neoplasm that usually arises in the distal extremities of young adults. Epithelioid sarcoma presents a high rate of recurrences and metastases and frequently poses diagnostic dilemmas. We previously reported loss of tumor suppressor SMARCB1 protein expression and SMARCB1 gene deletion in the majority of epithelioid sarcoma cases. Unfortunately, no appropriate preclinical models of such genetic alteration in epithelioid sarcoma are available. In the present report, we identified lack of SMARCB1 protein due to a homozygous deletion of exon 1 and upstream regulatory region in epithelioid sarcoma cell line VAESBJ. Restoration of SMARCB1 expression significantly affected VAESBJ cell proliferation, anchorage-independent growth, and cell migration properties, thus supporting the causative role of SMARCB1 loss in epithelioid sarcoma pathogenesis. We investigated the translational relevance of this genetic background in epithelioid sarcoma and showed that SMARCB1 ectopic expression significantly augmented VAESBJ sensitivity to gamma irradiation and acted synergistically with flavopiridol treatment. In VAESBJ, both activated ERBB1/EGFR and HGFR/MET impinged on AKT and ERK phosphorylation. We showed a synergistic effect of combined inhibition of these 2 receptor tyrosine kinases using selective small-molecule inhibitors on cell proliferation. These observations provide definitive support to the role of SMARCB1 inactivation in the pathogenesis of epithelioid sarcoma and disclose novel clues to therapeutic approaches tailored to SMARCB1-negative epithelioid sarcoma.

Prognostic determinants in epithelioid sarcoma.

BACKGROUND: Epithelioid sarcoma (ES) is a rare soft tissue neoplasm that usually arises in the distal extremities of young adults, presents a high rate of recurrences and metastases and frequently poses diagnostic dilemmas. In order to identify markers useful for patient stratification purposes, we investigated the prognostic impact of clinical and molecular patient characteristics, including the status of SMARCB1 tumour suppressor gene, in a consecutive series of ES cases. METHODS: Kaplan-Meier survival curves were compared by the log-rank test. Immunophenotyping and SMARCB1 protein expression were analysed by immunohistochemistry or western blotting in 40 ES patients for which tumour material was available. Cases lacking SMARCB1 protein expression were investigated for the presence of gene mutations and gene deletions by exon sequencing, fluorescent in situ hybridization and quantitative PCR. RESULTS: FNCLCC tumour grade 3 and proximal-type histology significantly correlated with shorter overall survival (log-rank p=0.0046 and p=0.0001, respectively). We identified loss of SMARCB1 protein expression in the majority of ES cases (25/40, 62.5%), including 24/34 (71%) adult cases but only 1/6 (17%) paediatric/adolescent cases (p=0.02, two-tailed Fisher's exact test). The absence of protein is strongly correlated with SMARCB1 gene deletion (p=0.003, two-tailed Fisher's exact test). We observed a trend towards the correlation between SMARCB1 inactivation and both higher tumour grading and a clinical course of the disease characterised by the occurrence of multiple relapses/metastasis. CONCLUSION: These data show that both tumour grading and subtype are prognostic factors in ES. Loss of SMARCB1 protein expression in ES is a frequent occurrence mediated by gene deletion events, thus pointing to a crucial role of SMARCB1 in ES genesis. Analysis of SMARCB1 status in ES warrants prospective investigation as a prognostic marker and therapeutic target.