Blocking the Cleavage of Filamin A by Calpain Inhibitor Decreases Tumor Cell Growth.

BACKGROUND/AIM: Filamin A (FLNA) is the most abundant and widely expressed isoform of filamin in human tissues. It is cleaved by calpain at the hinge 1 and 2 domains, producing a 90-kDa carboxyl-terminal fragment (FLNACT). Recently, it has been shown that FLNACT mediates cell signaling and transports transcription factors into the cell nucleus. However, the significance of cleavage of FLNA by calpain has not been studied in cancer cell growth. Calpeptin is a chemical inhibitor of both calpain 1 and 2 that cleaves FLNA. In this study, we questioned if inhibiting calpain using calpeptin would decrease tumor cell proliferation, migration, invasion, and colony formation. MATERIALS AND METHODS: Human melanoma (A7), prostate cancer (PC3), mouse fibrosarcoma (T241) and endothelial (MS1) cells were assayed for proliferation, migration, invasion and colony formation after treatment with calpeptin. Cell lysates were immunoblotted for FLNA and FLNACT Results: Calpeptin treatment of these cells resulted in a decreased production of FLNACT Calpeptin-treated human and mouse tumor cells displayed impaired proliferation, migration, and colony formation. CONCLUSION: These data suggest that the cleavage of FLNA by calpain is an important cellular event in the regulation of tumor cell growth.

Sense-Antisense lncRNA Pair Encoded by Locus 6p22.3 Determines Neuroblastoma Susceptibility via the USP36-CHD7-SOX9 Regulatory Axis.

Trait-associated loci often map to genomic regions encoding long noncoding RNAs (lncRNAs), but the role of these lncRNAs in disease etiology is largely unexplored. We show that a pair of sense/antisense lncRNA (6p22lncRNAs) encoded by CASC15 and NBAT1 located at the neuroblastoma (NB) risk-associated 6p22.3 locus are tumor suppressors and show reduced expression in high-risk NBs. Loss of functional synergy between 6p22lncRNAs results in an undifferentiated state that is maintained by a gene-regulatory network, including SOX9 located on 17q, a region frequently gained in NB. 6p22lncRNAs regulate SOX9 expression by controlling CHD7 stability via modulating the cellular localization of USP36, encoded by another 17q gene. This regulatory nexus between 6p22.3 and 17q regions may lead to potential NB treatment strategies.

p110α Hot Spot Mutations E545K and H1047R Exert Metabolic Reprogramming Independently of p110α Kinase Activity.

The phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) catalytic subunit p110α is the most frequently mutated kinase in human cancer, and the hot spot mutations E542K, E545K, and H1047R are the most common mutations in p110α. Very little is known about the metabolic consequences of the hot spot mutations of p110α in vivo. In this study, we used adenoviral gene transfer in mice to investigate the effects of the E545K and H1047R mutations on hepatic and whole-body glucose metabolism. We show that hepatic expression of these hot spot mutations results in rapid hepatic steatosis, paradoxically accompanied by increased glucose tolerance, and marked glycogen accumulation. In contrast, wild-type p110α expression does not lead to hepatic accumulation of lipids or glycogen despite similar degrees of upregulated glycolysis and expression of lipogenic genes. The reprogrammed metabolism of the E545K and H1047R p110α mutants was surprisingly not dependent on altered p110α lipid kinase activity.

The risk-associated long noncoding RNA NBAT-1 controls neuroblastoma progression by regulating cell proliferation and neuronal differentiation.

Neuroblastoma is an embryonal tumor of the sympathetic nervous system and the most common extracranial tumor of childhood. By sequencing transcriptomes of low- and high-risk neuroblastomas, we detected differentially expressed annotated and nonannotated long noncoding RNAs (lncRNAs). We identified a lncRNA neuroblastoma associated transcript-1 (NBAT-1) as a biomarker significantly predicting clinical outcome of neuroblastoma. CpG methylation and a high-risk neuroblastoma associated SNP on chromosome 6p22 functionally contribute to NBAT-1 differential expression. Loss of NBAT-1 increases cellular proliferation and invasion. It controls these processes via epigenetic silencing of target genes. NBAT-1 loss affects neuronal differentiation through activation of the neuronal-specific transcription factor NRSF/REST. Thus, loss of NBAT-1 contributes to aggressive neuroblastoma by increasing proliferation and impairing differentiation of neuronal precursors.