TLR4 signaling drives mesenchymal stromal cells commitment to promote tumor microenvironment transformation in multiple myeloma

Abstract

Inflammation represents a key feature and hallmark of tumor microenvironment playing a major role in the interaction with mesenchymal stromal cells (MSC) in cancer progression. The aim of the present study was to investigate the crosstalk between MSCs and myeloma cells (MM) in the pro-inflammatory microenvironment promoting immune evasion and tumor growth. MSC were collected from patients with diagnosis of MGUS (n = 10), smoldering myeloma (n = 7), multiple myeloma at diagnosis (n = 16), relapse (n = 5) or refractory (n = 3), and from age-matched healthy controls (HC, n = 10) and cultured with peripheral blood mononucleated cells (PBMC) from healthy volunteer donors. Similarly to MM, we showed that MSC from smoldering multiple myeloma (SMM) patients activated neutrophils and conferred an immunosuppressive and pro-angiogenic phenotype. Furthermore, co-cultures of plasma cells (PC) and HC-MSC suggested that such activation is driven by MM cells through the switching into a pro-inflammatory phenotype mediated by toll-like receptor 4 (TLR4). These results were further confirmed using a zebrafish as an immunocompetent in vivo model, showing the role of MM–MSC in supporting PCs engraftment and Th2 response. Such effect was abolished following inhibition of TLR4 signaling in MM–MSC before co-injection with PC. Moreover, the addition of a TLR4 inhibitor in the co-culture of HC-MSC with MM cells prevented the activation of the pro-tumor activity in PC-educated MSC. In conclusion, our study provides evidence that TLR4 signaling plays a key role in MSC transformation by inducing a pro-tumor phenotype associated with a permissive microenvironment allowing immune escape and tumor growth.

High-density neutrophils in MGUS and multiple myeloma are dysfunctional and immune-suppressive due to increased STAT3 downstream signaling

“…In human and mouse models, MM-derived exosomes can hamper myeloid maturation, conferring immature myeloid cells potent immune suppressive activity, through activation of STAT3, leading to increased immunosuppression which favors MM progression 65,66 . Our previous work showed that immune-modulatory factors released by MM-mesenchymal stem cells are able to induce G-MDSC in vitro from healthy peripheral blood mononuclear cells, supporting an evolving concept regarding the contribution of MM microenvironment to tumor www.nature.com/scientificreports www.nature.com/scientificreports/ development and progression through immune-editing 52,67 . While in solid tumors HDN could reflect the composition of immune infiltrate in tumor microenvironment without exerting immune-suppressive activity, HDN in MGUS and MM patients are immune-suppressive and share immune-suppressive features with G-MDSC, associated to increased CD64 and Arg-1, reduced phagocytosis and CD16 25,34,60 .…”

“…We found ARG1 gene upregulation among the up-regulated genes in MM-HDNs compared to healthy HDNs. Since our previous work showed that ARG1, a transcriptional target of STAT-3 47,48 , STAT-5 49 and STAT-6 50,51 , is increased in granulocytic-like myeloid derived suppressor cells in MM 28,38,52 , associated to inferior outcome after bortezomib treatment 28 , we explored its expression in both MGUS-and MM-HDNs.…”

Challenges for Immunotherapy in Multiple Myeloma: Bone Marrow Microenvironment-Mediated Immune Suppression and Immune Resistance

“…It has been shown that the crosstalk between MM-cells and MSCs mediated by toll-like receptor 4 (TRL4) signaling transforms MSCs into a "malignant" phenotype, which promotes tumor growth and immune escape [27]. The MM-conditioned MSCs have been shown to suppress T-cell activation and proliferation, impair DC maturation and induce Tregs via the secretion of several factors, including IL-6, TGF-β, IL-10, PGE2, and upregulated expression of several surface molecules such as VCAM-1, intracellular adhesion molecule-1 (ICAM-1) and CD40 [27][28][29][30][31][32]. Additionally, MSCs can exert their immunomodulatory activities by the secretion of extracellular vesicles [33,34].…”

Pyrocatechol, a component of coffee, suppresses LPS-induced inflammatory responses by inhibiting NF-κB and activating Nrf2

“…Previous studies reported the requirement of a number of procedures, such as the roasting of coffee beans, to obtain their medicinal effects 24 . To clarify whether the roasting procedure is required for the anti-inflammatory effects of coffee extract, we roasted green coffee beans at 220 degrees for different periods (5,10,15, and 20 min) and prepared their extracts (Fig. 7A).…”

“…In the process of inflammation, macrophage play a central role in through its ability to produce pro-inflammatory mediators, such as nitric oxide (NO), cytokines, and chemokines 1,2 . A number of accumulated researches have evidenced that chronic inflammation is commonly involved in onsets of age-associated diseases, such as cardiovascular disease, diabetes, and cancer [3][4][5] . Therefore, the regulation of inflammatory responses is crucial for preventing malignancy of these inflammation-related diseases.…”