We detected KPT-185-induced downregulation of PIM1 and c-Myc, whose mRNAs are known XPO1 cargos. XPO1 binds to c- Myc and PIM1 mRNAs as well as cyclin D1 mRNA via an adapter protein eukaryotic translation initiation factor 4E. Interestingly, we found that KPT-185 decreased phosphorylated 4E-BP1, which RRx-001 allows 4E-BP1 binding to eIF4e and inhibition of eIF4e effects. On the other hand, PIM1 kinase is known to interact with the ribosomal protein RPS19, one of the KPT-185 targeted ribosomal proteins in MCL cells , and depletion of RPS19 causes proteasomal degradation of PIM1 and p27KIP stabilization, thus causing a block in cell-cycle progression regardless of p53 status. iTRAQ proteomics showed that KPT-185 downregulated PIM2 irrespective of p53 status. PIM2 is known to be associated with an aggressive clinical course in B-cell lymphomas , and is involved in the regulation of mTOR complex 1. Our immunoblot data showed that KPT-185 downregulated mTORC1 downstream targets, phospho-S6K and/or phospho-4E-BP1. Gene expression profiling further showed p53-independent downregulation by KPT-185 of several factors closely associated with PIM, c-Myc, and mTOR signaling, such as cell division cycle25C , the global transcription factor pituitary tumor-transforming gene-1 , and the mTORC1 substrate serum/glucocorticoid-regulated kinase 1. The p53 status-independent 537034-17-6 transcriptional induction of PUMA by KPT-185 indicates the role of additional transcriptional factors, such as an XPO1 cargo FOXO3a that is responsible for the upregulation of PUMA , or NF-��B, whose blockade by KPT-SINEs induced p53-independent depletion of MCL cells. Of note, KPT-185 strikingly targeted cyclin D1 and its downstream signaling in MCL cells, and the blastoid-variant Z138 with high baseline expression of cyclin D1 was the most sensitive to KTP-185 among the testedMCL cell lines, suggesting that cyclin D1 is a critical target of KPT-185 for its anti-tumor activity. KPT-185 decreased XPO1 in all tested MCL cells, which is concordant with the previous reports of MCL and lung cancer cells , in which KPT-185 induced proteasomal degradation of XPO1 protein despite its normally long half-life. In our system,
