Endogenous transmembrane protein UT2 inhibits pSTAT3 and suppresses hematological malignancy
Dongjun Lee, … , Noopur Raje, David T. Scadden
Dongjun Lee, … , Noopur Raje, David T. Scadden
Published February 29, 2016
Citation Information: J Clin Invest. 2016;126(4):1300-1310. https://doi.org/10.1172/JCI84620.
View: Text | PDF
Research Article Oncology

Endogenous transmembrane protein UT2 inhibits pSTAT3 and suppresses hematological malignancy

Abstract

Regulation of STAT3 activation is critical for normal and malignant hematopoietic cell proliferation. Here, we have reported that the endogenous transmembrane protein upstream-of-mTORC2 (UT2) negatively regulates activation of STAT3. Specifically, we determined that UT2 interacts directly with GP130 and inhibits phosphorylation of STAT3 on tyrosine 705 (STAT3Y705). This reduces cytokine signaling including IL6 that is implicated in multiple myeloma and other hematopoietic malignancies. Modulation of UT2 resulted in inverse effects on animal survival in myeloma models. Samples from multiple myeloma patients also revealed a decreased copy number of UT2 and decreased expression of UT2 in genomic and transcriptomic analyses, respectively. Together, these studies identify a transmembrane protein that functions to negatively regulate cytokine signaling through GP130 and pSTAT3Y705 and is molecularly and mechanistically distinct from the suppressors of cytokine signaling (SOCS) family of genes. Moreover, this work provides evidence that perturbations of this activation-dampening molecule participate in hematologic malignancies and may serve as a key determinant of multiple myeloma pathophysiology. UT2 is a negative regulator shared across STAT3 and mTORC2 signaling cascades, functioning as a tumor suppressor in hematologic malignancies driven by those pathways.

Authors

Dongjun Lee, Ying-Hua Wang, Demetrios Kalaitzidis, Janani Ramachandran, Homare Eda, David B. Sykes, Noopur Raje, David T. Scadden

×

Figure 1

Negative regulation of STAT3 activation by UT2.

Options: View larger image (or click on image) Download as PowerPoint
Negative regulation of STAT3 activation by UT2. (A–C) Flow cytometry was...
(A–C) Flow cytometry was performed on sgRNA-mediated depletion of UT2 (left panel) or overexpressing (OE) UT2 (right panel) primary hematopoietic BM (A), HEK293T (B), and INA6 (C) cells. Quantification shown of the normalized fold-change in mean fluorescence intensity (MFI) for the indicated phospho-protein in these cells. Data are shown as mean ± SEM (n = 2–3 experiments; two-tailed, unpaired t test; **P < 0.01). See also Supplemental Figure 1D. (D and E) sgRNA-mediated depletion of UT2 (left panel) or OE UT2 (right panel) HEK293T (D) and INA6 (E) cells were starved for 24 hours and then restimulated with IL6 (20 ng/ml) for 30 minutes prior to being analyzed by flow cytometry. Quantification showed the normalized fold-change in MFI for the indicated pSTAT3Y705 levels in these cells. Data are shown as mean ± SEM (n = 2–4 experiments; two-tailed, unpaired t test; **P < 0.01). See also Supplemental Figure 1, E and F. (F) sgRNA-mediated depletion of UT2 (left panel) or OE UT2 INA6 cells (right panel) were placed into liquid culture with or without IL6, and cells were counted every day. Quantification showed the normalized fold-change in cell numbers in these cells. Days 1–3 of Ctrl + rhIL6 compared with corresponding days of UT2 OE + rhIL6. Data are shown as mean ± SEM (n = 2 experiments; two-tailed, unpaired t test; **P < 0.01). – rhIL6, rhIL6 withdrawal.