TLR4 and plasma cell myeloma: Activation of TLR4 signaling favors myeloma PC proliferation and decreases the pro-apoptotic efficacy of bortezomib through the suppression of ER-stress-induced apoptosis [12] but at the same time leads to activation of the nuclear factor erythroid 2–related factor 2 (Nrf2), which in turn controls the expression of several detoxifying and antioxidant enzymes including heme oxygenase-1 (HO-1) [13].