Fig. 1: Hypoxia and proteasomal inhibition independently cause mTORC1 suppression in MM.
From: An mTORC1 to HRI signaling axis promotes cytotoxicity of proteasome inhibitors in multiple myeloma
A A relative correlation between mRNA expression level of TSC2 and HIF1β in CD138 + bone marrow plasma cells from healthy subjects (n = 22) and newly diagnosed MM patients (n = 559). Axis units are arbitrary. Error bars represent S.E.M. B, C Shown are Kaplan–Meier plots for the overall survival (OS) and progression-free survival (PFS) of MM patients with differential expression of TSC2 (B) and HIF1β (C) from GMMG HD4 and MM5 trials. D Subcutaneous tumor growth of wt, NPRL2 KO, and TSC2 KO MM.1S cells into NCG mice (n = 4). Shown is the average relative tumor weight ± S.E.M. and the asterisk represents p < 0.05 of unpaired two-tailed student’s t-test between wt and KO. ns, not significant. E Cells were cultured in fresh media for 4 h in either normoxia or hypoxia. mTORC1 response was assessed by immunoblotting of its downstream phosphorylated and total effectors, S6K1, S6, and 4E-BP1. p97 was used to confirm equal protein loading in each lane. Shown are technical duplicates in each condition of a typical experiment of three repetitions. F, G Cells were cultured in fresh media for 16 h, then treated with IXZ [32 nM]. Following the treatment, cells were collected for immunoblotting in increasing time points as indicated. Shown are immunoblots for downstream effectors of mTORC1. Ubiquitin immunoblot was used to assess proteasomal inhibition. Shown are a typical immunoblots out of three independent experiments. nor, normoxia. hyp, hypoxia, IXZ, ixazomib.
