XBP1 and neoplasm: Notably, the levels of p-STAT3 and total STAT3 were significantly reduced in KPC tumor-bearing Xbp1mKO mice compared to corresponding Xbp1fl/fl mice suggesting that the IRE1α/XBP1 signaling mediates the activation of the JAK-STAT signaling in skeletal muscle of KPC tumor-bearing mice (Fig. 5C,D).