A Novel Somatic Frameshift Mutation in PIK3CA Causes CLOVES Syndrome by Provoking PI3K/AKT/mTOR Pathway

Background: CLOVES syndrome(OMIM#612918) is a rare overgrowth disorder resulted from mosaic gain-of-function mutations in the PIK3CA gene. All the reported CLOVES-associated PIK3CA mutations are missense mutations affecting certain residues. To investigate underlying mutation and its pathogenicity in a patient with CLOVES syndrome and to evaluate the inhibitory effect of ARQ092, one of the PI3K/AKT/mTOR pathway inhibitors. Results: We performed whole-exome sequencing (WES) and Sanger sequencing to detect underlying somatic mutations in the skin lesion of the patient. Quantitative real-time PCR (qRT-PCR) was employed to evaluate the mRNA abundance of PIK3CA in the patient’s skin lesion. AKT phosphorylation level assessed by Western blot was performed to evaluate the PIK3CA mutations and inhibitory effects of ARQ092. A novel somatic frameshift mutation c.3206_3207insG (p.X1069Trpfs*4) in PIK3CA was identified in the genomic DNA extracted from the vascular malformation sample of the patient. This mutation affects the canonical stop codon of PIK3CA (NM_006218.4 ) and is predicted to produce a prolonged protein with four additional residues. qRT-PCR demonstrated that the mRNA expression levels of the patient’s affected skin tissue were comparable compared to the normal control. In vitro studies revealed that p.X1069Trpfs*4 mutant exhibited increased AKT phosphorylation significantly compared to that of the wildtype, which could be inhibited by ARQ092. Conclusions: We have identified the first frameshift mutation in PIK3CA , which overactivated PI3K/AKT/mTOR pathway to cause CLOVES syndrome. We also provided evidence of ARQ092 to be a potential therapeutic option for PROS in vitro .