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Repurposing tofacitinib as an anti-myeloma therapeutic to reverse growth-promoting effects of the bone marrow microenvironment.

Repurposing tofacitinib as an anti-myeloma therapeutic to reverse growth-promoting effects of the bone marrow microenvironment.
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Lam C, Ferguson ID, Mariano MC, Lin YT, Murnane M, Liu H, Smith GA, Wong SW, Taunton J, Liu JO, Mitsiades CS, Hann BC, Aftab BT, Wiita AP,


Lam C, Ferguson ID, Mariano MC, Lin YT, Murnane M, Liu H, Smith GA, Wong SW, Taunton J, Liu JO, Mitsiades CS, Hann BC, Aftab BT, Wiita AP, (click to view)

Lam C, Ferguson ID, Mariano MC, Lin YT, Murnane M, Liu H, Smith GA, Wong SW, Taunton J, Liu JO, Mitsiades CS, Hann BC, Aftab BT, Wiita AP,

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Haematologica 2018 04 05() pii haematol.2017.174482
Abstract

The myeloma bone marrow microenvironment promotes proliferation of malignant plasma cells and resistance to therapy. Activation of JAK/STAT signaling is thought to be a central component of these microenvironment-induced phenotypes. In a prior drug repurposing screen, we identified tofacitinib, a pan-JAK inhibitor FDA-approved for rheumatoid arthritis, as an agent that may reverse the tumor-stimulating effects of bone marrow mesenchymal stromal cells. Here, we validated in vitro, in stromal-responsive human myeloma cell lines, and in vivo, in orthotopic disseminated xenograft models of myeloma, that tofacitinib showed efficacy in myeloma models. Furthermore, tofacitinib strongly synergized with venetoclax in co-culture with marrow stromal cells but not in monoculture. Surprisingly, we found that ruxolitinib, an FDA-approved agent targeting JAK1 and JAK2, did not lead to the same anti-myeloma effects. Combination with a novel irreversible JAK3-selective inhibitor also did not enhance ruxolitinib effects. RNA-seq and unbiased phosphoproteomics revealed that marrow stromal cells stimulate a JAK/STAT-mediated proliferative program in myeloma plasma cells, and tofacitinib reversed the large majority of these pro-growth signals. Taken together, our results suggest that tofacitinib reverses the growth-promoting effects of the tumor microenvironment. As tofacitinib is already FDA-approved, these results can be rapidly translated into potential clinical benefits for myeloma patients.

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