IL-32 is induced by activation of toll-like receptors in multiple myeloma cells

Abstract

Multiple myeloma (MM) is a hematological cancer characterized by accumulation of malignant plasma cells in the bone marrow. The patients are immune suppressed and suffer from recurrent and chronic infections. Interleukin-32 is a non-conventional, pro-inflammatory cytokine expressed in a subgroup of MM patients with a poor prognosis. IL-32 has also been shown to promote proliferation and survival of the cancer cells. Here we show that activation of toll-like receptors (TLRs) promotes expression of IL-32 in MM cells through NFκB activation. In patient-derived primary MM cells, IL-32 expression is positively associated with expression of TLRs. Furthermore, we found that several TLR genes are upregulated from diagnosis to relapse in individual patients, predominantly TLRs sensing bacterial components. Interestingly, upregulation of these TLRs coincides with an increase in IL-32. Taken together, these results support a role for IL-32 in microbial sensing in MM cells and suggest that infections can induce expression of this pro-tumorigenic cytokine in MM patients.

Toll-like receptor signaling in multiple myeloma cells promotes the expression of pro-survival genes B-cell lymphoma 2 and MYC and modulates the expression of B-cell maturation antigen

“…The MM cell line RPMI-8226 expresses a broad range of TLRs ( 23 ) including TLR4 and TLR9, which were also expressed in a high proportion of the primary MM cells. In line with previously published data ( 22 , 25 , 27 – 29 ), we found that both cell proliferation ( Figure 1C ) and cell viability ( Figures 1D, E ) were increased following LPS and CpG treatment.…”

“…The MM cell line RPMI-8226 was obtained from the American Type Culture Collection (ATCC; Rockville, MD, USA). RPMI-8226 cells depleted for TLR4 (TLR4 KO), TLR9 (TLR9 KO), and control/mock (WT) cells were generated by gene editing using CRISPR/Cas9 as previously described ( 23 ). The cells were cultured in RPMI-1640 medium with 20% heat-inactivated fetal calf serum (FCS) during expansion and 10% FCS for experiments.…”

“…We and others have shown that TLRs are expressed by primary myeloma cells and MM cell lines ( 21 – 28 ). Moreover, expression of several TLRs increases from diagnosis to relapse in individual patients ( 23 ). Several studies have demonstrated proliferative and pro-survival effects of TLR signaling on MM cells ( 22 , 25 – 29 ).…”

“…They recognize microbial patterns known as pathogen-associated molecular patterns (PAMPs) and can also recognize damageassociated molecular patterns (DAMPs), which are endogenous molecules derived from damaged cells (19,20). We and others have shown that TLRs are expressed by primary myeloma cells and MM cell lines (21)(22)(23)(24)(25)(26)(27)(28). Moreover, expression of several TLRs increases from diagnosis to relapse in individual patients (23).…”

The pro-tumorigenic cytokine IL-32 has a high turnover in multiple myeloma cells due to proteolysis regulated by oxygen-sensing cysteine dioxygenase and deubiquitinating enzymes

“…OH-2 and IH-1 were established in our laboratory ( 16 , 17 ). The cells were cultured in RPMI-1640 medium with fetal calf serum or human serum as previously described ( 18 ). For T-cell isolation and activation, human PBMCs were isolated from buffy coat using Lymphoprep (Stem Cell Technologies, Vancouver, Canada) according to the manufacturer’s protocol.…”