Fig 2: INPP4B inhibits MM cells growth via regulating the PI3K/Akt pathway. (A) Western blot analyzes the relative protein levels of Akt, p-Akt (thr308), p-Akt (ser473), rictor-mTOR complex (mTORC2) in LP-1, RPMI 8226, and MM.1S cells after lentiviral-carrying INPP4B overexpression for 48 h and (B) detections in LP-1, RPMI 8226, and MM.1S cells after lentiviral-carrying INPP4B knockdown for 48 h.

Fig 3: Expression of INPP4B in MM patient samples. (A) The expression level of INPP4B in newly diagnosed MM patient samples. (B) Correlation of INPP4B expression with progression-free survival (PFS) and (C) overall survival (OS) in patients with newly diagnoses MM patients.

Fig 4: Expression of INPP4B in EMP samples and cell lines. (A) Immunohistochemical images of EMP tissue (focal positive: a, b, c; negative: d, e, f). Scar = 50 μm. (B) Patients stratified according to their INPP4B expression level (positive and negative) and correlation of INPP4B expression with progression-free survival (PFS). (C) Overall survival (OS) rate of patients with these extramedullary involvements. (D) Correlation of INPP4B expression and overall survival rate of MM patients in GSE7982 cohort. (E) INPP4B protein expression in various multiple myeloma cell lines. (F) INPP4B mRNA expression in various multiple myeloma cell lines. Data are plotted as mean ± SD from three independent experiments (**p < 0.01, vs. the control).

Fig 5: Lysosome volume and numbers are altered upon PIKfyve inhibition in Inpp4b-deficient cells.A, lysosomes of Inpp4b+/+ or Inpp4b−/− MEFs prelabeled with Lucifer Yellow and exposed to vehicle or apilimod at indicated concentrations for 1 h. Fluorescence micrographs represent Z-projections of 25 to 30 Z-planes acquired through spinning disc confocal microscopy. Image analysis performed for individual lysosome volume (B), lysosome number per cell (C), and total lysosome volume per cell (D). The scale bar represents 25 μm. Data represent mean ± SD from three independent experiments, with 25 to 30 cells assessed per treatment condition per experiment. Statistical significance was measured by ANOVA and multiple Student’s t test and represented as ∗ (p < 0.05). INPP4B, inositol polyphosphate 4-phosphatase type II; MEF, mouse embryonic fibroblast; PIKfyve, Phosphoinositide Kinase, FYVE-Type Zinc Finger Containing.