Phosphatidylinositol-3-kinase (PI3K)/Akt Signaling is Functionally Essential in Myxoid Liposarcoma

Abstract

Myxoid liposarcoma (MLS) is an aggressive soft-tissue tumor characterized by a specific reciprocal t(12;16) translocation resulting in expression of the chimeric FUS-DDIT3 fusion protein, an oncogenic transcription factor. Similar to other translocation-associated sarcomas, MLS is characterized by a low frequency of somatic mutations, albeit a subset of MLS has previously been shown to be associated with activating PIK3CA mutations. This study was performed to assess the prevalence of PI3K/Akt signaling alterations in MLS and the potential of PI3Kdirected therapeutic concepts. In a large cohort of MLS, key components of the PI3K/Akt signaling cascade were evaluated by next generation seqeuncing (NGS), fluorescence in situ hybridization (FISH), and immunohistochemistry (IHC). In three MLS cell lines, PI3K activity was inhibited by RNAi and the small-molecule PI3K inhibitor BKM120 (buparlisib) in vitro. An MLS cell line-based avian chorioallantoic membrane model was applied for in vivo confirmation. In total, 26.8% of MLS cases displayed activating alterations in PI3K/Akt signaling components, with PIK3CA gain-of-function mutations representing the most prevalent finding (14.2%). IHC suggested PI3K/Akt activation in a far larger subgroup of MLS, implying alternative mechanisms of pathway activation. PI3K-directed therapeutic interference showed that MLS cell proliferation and viability significantly depended on PI3K-mediated signals in vitro and in vivo. Our preclinical study underlines the elementary role of PI3K/Akt signals in MLS tumorigenesis and provides a molecularly based rationale for a PI3K-targeted therapeutic approach which may be particularly effective in the subgroup of tumors carrying activating genetic alterations in PI3K/Akt signaling components.

Requirement for YAP1 signaling in myxoid liposarcoma

“…Though FUS‐DDIT3 has been documented to be incorporated into transcription complexes and to be associated with chromatin remodeling (Goransson et al , ), its specific mode of action remains incompletely understood. As other translocation‐related sarcomas, e.g., Ewing sarcoma, synovial sarcoma, or alveolar rhabdomyosarcoma, MLS genomes harbor few somatic mutations, underscoring the dominant role of FUS‐DDIT3 in MLS pathogenesis (Barretina et al , ; Crompton et al , ; Shern et al , ; Tirode et al , ; Trautmann et al , ). Since therapeutic inhibition of the chimeric fusion protein itself represents a challenge, it appears most promising to intercept signaling pathways that are functionally dependent on FUS‐DDIT3 activity for selective targeting of MLS cells.…”

Prevalence of the Hippo Effectors YAP1/TAZ in Tumors of Soft Tissue and Bone

“…For in vivo confirmation, we used the chick embryo chorioallantoic membrane (CAM) in vivo model as previously reported and validated for anticancer agents 21,23–25 . Due to the presence of vascular supply and the absence of an immune response from the graft, the CAM enables the transplantation of human cancer cells and the subsequent development of solid tumor xenografts in a three-dimensional in vivo microenvironment.…”

Novel pathogenic alterations in pediatric and adult desmoid-type fibromatosis – A systematic analysis of 204 cases

“…that are commonly mutated in cancer. As described before [32][33][34] , Target enrichment was conducted by means of the GeneRead DNAseq Panel PCR V2 Kit (Qiagen). Purification and size selection steps were processed utilizing Agencourt AMPure XP magnetic beads (Beckman Coulter).…”

“…In silico tools to predict the potential deleterious impact of detected variants. The potential impact of NGS-detected variants in the coding regions was predicted using following in silico tools as reported [32][33][34] : PolyPhen-2 (v2.2.2r398) 35 , Protein Variation Effect Analyzer (PROVEAN; v1.1.3) 36 , Sorting Intolerant From Tolerant (SIFT; Ensembl 66) 37,38 , Mutation Assessor (release 3) 39 and Combined Annotation Dependent Depletion (CADD; v.1.3) 40 . The PolyPhen-2 method utilizes physical and evolutionary comparative considerations to predict amino acid changes on protein structure and function.…”