The Ubiquitin–CXCR4 Axis Plays an Important Role in Acute Lung Infection–Enhanced Lung Tumor Metastasis

Abstract

Purpose Our goals are to test the effect of acute lung infection on tumor metastasis and to investigate the underlying mechanisms. Experimental Design We combined bacteria- and lipopolysaccharide (LPS)-induced acute lung injury/inflammation (ALI) mouse models with mouse metastatic models to study the effect of acute inflammation on lung metastasis in mice. The mechanisms were invested in ex vivo, in vitro, and in vivo studies. Results Both bacteria- and LPS-induced acute lung injury/inflammation significantly enhanced lung metastasis of four tail vein-injected mouse tumor cell lines. Bacteria also enhanced lung metastasis when 4T1 cells orthotopically injected. The broncheoalveolar lavage fluid (BALF) from LPS- or bacteria- injected mice stimulated migration of tumor cells. In vivo tracking of metastatic RM-9 cells showed that bacterial injection enhanced early dissemination of tumor cells to the lung. The majority of the BALF migratory activity could be blocked by AMD3100, a CXCR4 inhibitor. All tested cell lines expressed CXCR4. The levels of extracellular ubiquitin (Ub), but not SDF-1, in BALF were significantly increased by LPS. Ub was able to induce AMD3100-sensitive migration of tumor cells. Finally, the anti-bacterial amoxicillin and AMD3100 blocked the enhancement effect of bacterial infection on tumor metastasis. Conclusions Acute lung infection dramatically increased cancer cell homing to the lung and lung metastasis. This may be due to an alteration of the lung microenvironment and preparation of a favorable metastatic “niche”. This effect was seen in multiple cancer types and thus may have broad applications for cancer patients in prevention and/or treatment of metastasis.

Heteromerization of chemokine (C-X-C motif) receptor 4 with α1A/B-adrenergic receptors controls α1-adrenergic receptor function

“…This implies that CXCR4 and also ACKR3 function as modulators of α 1 -AR. Whereas the molecular mechanisms through which ACKR3 influences α 1 -AR function remain to be determined, the observed effects of ubiquitin in the present study are in agreement with the findings that ubiquitin functions as a noncognate CXCR4 agonist that does not bind to ACKR3 (51,52,(59)(60)(61)(62)(63). The observation that CXCL12, which has a much higher affinity for ACKR3 than for CXCR4 (64), also enhanced the potency of PE in normal animals in vivo in the present study, whereas CXCL12 previously desensitized PE-mediated vasoconstriction of isolated arteries and reduced blood pressure during hemorrhagic shock (9), suggests that effects of CXCL12 depend on the relative functional contribution of CXCR4 and ACKR3 within the specific experimental or (patho)physiological environment (65).…”

An ubiquitin-binding molecule can work as an inhibitor of ubiquitin processing enzymes and ubiquitin receptors

“…This inhibitory activity is almost comparable to that of the approved CXCR4 inhibitor, AMD3100, which is a known specific inhibitor that binds to CXCR4. Thereby AMD3100 disrupts the binding of ligands, such as ubiquitin and SDF1α, to CXCR4 and subsequently blocks the CXCR4-mediated cancer cell migration [15]. Thus, the comparable activities of CSB6B and AMD3100 in the inhibition of the PI3K/AKT pathway, cell migration, and wound healing (Fig.…”

“…Then, we investigated the inhibitory activity of CSB6B on the ubiquitin-protein interaction by examining the binding affinity of ubiquitin to CXCR4, a cell surface receptor that recognizes ubiquitin as a ligand [13][14][15]. Since ubiquitin binding to the cell surface would be mediated by CXCR4, the interaction of FITC-labeled ubiquitin with CXCR4 was assessed by measuring the fluorescence associated with human monocyte cells (THP-1) after treating CSB6B at various concentrations (Figs.…”

“…2), it was expected that CSB6B can effectively block the binding of ubiquitin to CXCR4 and inhibit the ubiquitin-CXCR4 signaling. Accordingly, the effects of CSB6B on the level of AKT phosphorylation and migration of H1299, a human non-small cell lung carcinoma cell line, triggered by extracellular ubiquitin, were examined and compared to those of AMD3100 [15,32].…”

“…Recent progress in ubiquitin biology revealed that various forms of unanchored ubiquitin are also involved in cellular signaling [10][11][12]. For example, unanchored extracellular ubiquitin is responsible for apoptosis, cell growth, immune modulation, and cancer progression through its binding to CXC chemokine receptor type 4 (CXCR4) [13][14][15].…”