Biallelic loss of FAM46C triggers tumor growth with concomitant activation of Akt signaling in multiple myeloma cells

Abstract

Loss of heterozygosity or mutation of the family with sequence similarity 46, member C (FAM46C) gene on chromosome band 1p12 is associated with shorter overall survival of patients with multiple myeloma (MM). In this study, using human MM cell lines (KMS-11, OCI-My5, and ANBL-6), we generated FAM46C −/− cell clones and examined the effect of disruption of FAM46C on cell survival and cellular signaling.Cell proliferation assays showed increased clonogenicity of FAM46C −/− KMS-11 cells compared to WT cells. Xenograft experiments showed significantly shorter overall survival of mice harboring the FAM46C −/− cell-derived tumors than mice with the FAM46C WT cell-derived tumors. Notably, levels of phosphorylated Akt and its substrates increased both in vitro and in vivo in the FAM46C −/− cells compared to WT cells. In addition, caspase activities decreased in the FAM46C −/− cells. Results of gene set enrichment analysis showed that loss of FAM46C significantly activated serumresponsive genes while inactivating phosphatase and tensin homolog (PTEN)-related genes. Mechanistically, loss of FAM46C decreased the PTEN activity, number of apoptotic cells, and caspase activities. PF-04691502, a selective PI3K inhibitor, suppressed the augmented phosphorylation of Akt and its substrate FoxO3a. Treatment with afuresertib (a specific Akt inhibitor) in combination with bortezomib additively decreased FAM46C −/− MM cell survival. Collectively, this study is the first to report that loss of FAM46C triggers the concomitant activation of the PI3K-Akt signaling pathway, which might be a therapeutic target for MM with abnormalities in theFAM46C gene. K E Y W O R D S FAM46C, multiple myeloma, PI3K-Akt, tumor suppressor, tumorigenesis

Structural and functional characterization of multiple myeloma associated cytoplasmic poly(A) polymerase FAM46C

“…It was reported recently that loss of FAM46C reduced the activity of phosphatase and tensin homolog (PTEN), thereby activating the PI3K‐protein kinase B (Akt) signaling pathway and promoting the malignancy of MM cells [ 57 ]. A similar mechanism of FAM46C in regulating the PTEN/Akt axis was also observed in prostate cancer [ 32 ].…”

JMJD2C triggers the growth of multiple myeloma cells via activation of β‑catenin

“…Cell viability was assessed with an MTT assay as described in previous studies ( 26 , 27 ). Briefly, cells were seeded in 96-well culture plates (1×10 4 cells/well) following pre-transfection with vector control or pcDNA/JMJD2C for 48 h. Following incubation with MTT for 4 h, the optical density of viable cells was measured at 450 nm using a SpectraMAX M5 spectrophotometer (Molecular Devices LLC).…”

“…U266 cells were pre-transfected with vector control or JMJD2C construct for 12 h as described above, and further treated with inhibitors of NF-κB [10 µM BAY 11-7082 (BAY)], GSK3β/β-catenin (10 µM LiCl), PI3K/Akt [10 µM LY294002 (LY)], ERK1/2 [10 µM PD98059 (PD)] and EGFR [10 µM AG1478 (AG)] for 48 h, and subsequently cell viability was determined Cell viability assay. Cell viability was assessed with an MTT assay as described in previous studies (26,27). Briefly, cells were seeded in 96-well culture plates (1x10 4 cells/well) following pre-transfection with vector control or pcDNA/JMJD2C for 48 h. Following incubation with MTT for 4 h, the optical density of viable cells was measured at 450 nm using a SpectraMAX M5 spectrophotometer (Molecular Devices LLC).…”

The Immunity‐malignancy equilibrium in multiple myeloma: lessons from oncogenic events in plasma cells

“…This article is protected by copyright. All rights reserved with concomitant activation of the PI3K/Akt survival pathway and decreased caspase activity [130]. These observations suggest that MM might have an advantage in losing the potent stabilizing action of FAM46C on secretory transcripts, in order to curb Ig oxidative folding and the related proteosynthetic and metabolic stress to prioritize survival and proliferation.…”