Son DS, et al. Immune Netw. 2020 Jul;20(4):e29. https://doi.org/10.4110/in.2020.20.e29

Obesity is recognized as a low-grade chronic inflammatory state which involves a chemokine network contributing to a variety of diseases. As a first step toward understanding the roles of the obesity-driven chemokine network, we used a 3T3-L1 cell differentiation model to identify the chemokine profiles elicited during adipogenesis and how this profile is modified by epidermal growth factor (EGF) and tumor necrosis factor-α (TNF) as a growth and proinflammatory factor, respectively. The chemokine network was monitored using PCR arrays and qRT-PCR while main signaling pathways of EGF and TNF were measured using immunoblotting. The dominant chemokines in preadipocytes were CCL5, CCL8, CXCL1, and CXCL16, and in adipocytes CCL6 and CXCL13. The following chemokines were found in both preadipocytes and adipocytes: CCL2, CCL7, CCL25, CCL27, CXCL5, CXCL12, and CX3CL1. Among chemokine receptors, CXCR7 was specific for preadipocytes and CXCR2 for adipocytes. These findings indicate the development of a CXCL12-CXCR7 axis in preadipocytes and a CXCL5-CXCR2 axis in adipocytes. In addition to induction of CCL2 and CCL7 in both preadipocytes and adipocytes, EGF enhanced specifically CXCL1 and CXCL5 in adipocytes, indicating the potentiation of CXCR2-mediated pathway in adipocytes. TNF induced CCL2, CCL7, and CXCL1 in preadipocytes but had no response in adipocytes. EGFR downstream activation was dominant in adipocytes whereas NFκB activation was dominant in preadipocytes. Taken together, the adipocyte-driven chemokine network in the 3T3-L1 cell differentiation model involves CXCR2-mediated signaling which appears more potentiated to growth factors like EGF than proinflammatory factors like TNF.

Ovarian cancer is an inflammation-associated malignancy with a high mortality rate. CXCR2 expressing ovarian cancers are aggressive with poorer outcomes. We therefore investigated molecular mechanisms involved in CXCR2-driven cancer progression by comparing CXCR2 positive and negative ovarian cancer cell lines. Stably CXCR2 transfected SKOV-3 cells had a faster growth rate as compared to control cells transfected with empty vector. Particularly, tumor necrosis factor (TNF), abundantly expressed in ovarian cancer, enhanced cell proliferation by decreasing the G0-G1 phase in CXCR2 transfected cells. TNF increased nuclear factor-κB (NF-κB) activity to a greater degree in CXCR2 transfected cells than control cells as well as provided a greater activation of IκB. CXCR2 transfected cells expressed higher levels of its proinflammatory ligands, CXCL1/2 and enhanced more proliferation, migration, invasion and colony formation. CXCR2 positive cells also activated more EGFR, which led to higher Akt activation. Enhanced NF-κB activity in CXCR2 positive cells was reduced by a PI3K/Akt inhibitor rather than an Erk inhibitor. CXCL1 added to CXCR2 positive cells led to an increased activation of IκB. CXCL1 also led to a significantly greater number of invasive cells in CXCR2 transfected cells, which was blocked by the NF-κB inhibitor, Bay 11-7082. In addition, enhanced cell proliferation in CXCR2 positive cells was more sensitive to CXCL1 antibody or an NF-κB inhibitor. Finally, CXCR2 transfection of parental cells increased CXCL1 promoter activity via an NF-κB site. Thus augmentation of proinflammatory chemokines CXCL1/2, by potentiating NF-κB activation through EGFR-transactivated Akt, contributes to CXCR2-driven ovarian cancer progression.

Ovarian cancer, one of inflammation-associated cancers, is the fifth leading cause of cancer deaths among women. Inflammation in the tumor microenvironment is associated with peritoneal tumor dissemination and massive ascites, which contribute to high mortality in ovarian cancer. Tumor suppressor p53 is frequently deleted or mutated in aggressive and high-grade ovarian cancer, probably aggravating cancer progression and increasing mortality. We therefore investigated the influence of p53 on proinflammatory chemokines in ovarian cancer cells. A PCR array of the chemokine network revealed that ovarian cancer cells with low or mutated p53 expression expressed high levels of proinflammatory chemokines such as CXCL1, 2, 3 and 8. Transient transfection of p53 into p53-null ovarian cancer cells downregulated proinflammatory chemokines induced by tumor necrosis factor-α (TNF), a proinflammatory cytokine abundantly expressed in ovarian cancer. Furthermore, p53 restoration or stabilization blocked TNF-induced NF-κB promoter activity and reduced TNF-activated IκB. Restoration of p53 increased ubiquitination of IκB, resulting from concurrently reduced proteasome activity followed by stability of IκB. A ubiquitination PCR array on restoration of p53 did not reveal any significant change in expression except for Mdm2, indicating that the balance between p53 and Mdm2 is more important in regulating NF-κB signaling rather than the direct effect of p53 on ubiquitin-related genes or IκB kinases. In addition, nutlin-3, a specific inducer of p53 stabilization, inhibited proinflammatory chemokines by reducing TNF-activated IκB through p53 stabilization. Taken together, these results suggest that p53 inhibits proinflammatory chemokines in ovarian cancer cells by reducing proteasomal degradation of IκB. Thus, frequent loss or mutation of p53 may promote tumor progression by enhancing inflammation in the tumor microenvironment.

Serum amyloid A predisposes inflammatory tumor microenvironment in triple negative breast cancer Serum amyloid A predisposes inflammatory tumor microenvironment in triple negative breast cancer