ABSTRACT
Chemokine signal pathways are important for the regulation of tumour metastasis. Chemokine receptors CXCR4 (C-X-C chemokine receptor type 4) and XCR1 (chemokine XC receptor 1) are involved in the metastasis of breast cancer, while the interaction between them remains unclear. Here we first identified the interaction between CXCR4 and XCR1 based on membrane protein yeast two-hybrid assays. Bioluminescence resonance energy transfer (BRET) showed that XCR1 could competitively bind to CXCR4 to form a heterodimer (P < 0.01). Results of wound healing assays via transient transfection of XCR1 and CXCR4 into HEK293 cells showed that 41.55% of the migration area rate in the co-transformation group was lower than 58.75% in the CXCR4-alone group after adding 30 nmol/L S D F-β. The co-expression of XCR1 inhibited the cellular motility, possibly mediated by the SDF-1β (stromal cell-derived factor 1)/CXCR4 signal pathway (P < 0.05). Furthermore, CXCR4 on the cell surface after co-expression of XCR1 in CXCR4-EGFP transgenic HEK293 cells was detected by flow cytometry. And the result suggested that XCR1 could accelerate the internalization of CXCR4 into the heterodimer induced by 30 nmol/L SDF-1β (P<0.05), which increased the internalization rate from 14.38% to 64.10%. Finally, the phosphorylation of Akt and ERK, which were involved in cell proliferation and migration, respectively, were examined. After 10 minutes of SDF-1β stimulation, ERK phosphorylation in the CXCR4-alone group showed a 3.59-fold increase, whereas the increase of ERK phosphorylation in the co-transfected group was only 2.08-fold. Interestingly, heterodimer formation reduced the phosphorylation level of ERK and shortened the activation time, whereas the phosphorylation level of Akt remained unchanged. Collectively, our findings revealed the hetero-dimerization of CXCR4 and XCR1 and its effects on CXCR4-mediated cellular motility, receptor internalization, and ERK pathway phosphorylation. Therefore, XCR1-targeting drugs could be candidates for cross-desensitization of CXCR4 and might represent a possible option for inhibiting breast cancer metastasis.
ABSTRACT
<p><b>OBJECTIVE</b>To evaluate the effect of sodium tanshinone IIA sulfonate (STS) in preventing postoperative peritoneal adhesions in rats and explore the mechanisms.</p><p><b>METHODS</b>Sixty SD rats were randomized into 4 equal groups, including a blank control group, adhesion model group, and high-, moderate-, and low-dose STS-treated groups, and were subjected to injuries of the parietal peritoneum and cecum to induce peritoneal adhesions, followed by intraperitoneal administration of saline and STS at the doses of 20, 10, and 5 mg/kg for 7 consecutive days, respectively. Another 15 untreated rats served as the blank control group. The adhesion scores in each group were recorded after the treatments; the activity of tissue-type plasminogen activator (tPA) in peritoneal lavage fluid was measured, tPA/PAI-1 protein ratio in the peritoneal tissue was determined by ELISA, and the expressions of TGF-β1 and collagen I were detected by immunohistochemistry. The anastomotic healing model was used to assess the impact of STS on wound healing.</p><p><b>RESULTS</b>Intraperitoneal administration of STS effectively prevented peritoneal adhesion without affecting anastomotic healing in the rats. Compared with the adhesion model group, the STS-treated groups showed increased peritoneal lavage fluid tPA activity and tPA/PAI-1 ratio in the ischemic tissues with lowered TGF-β1 and collagen I expressions in the ischemic tissues.</p><p><b>CONCLUSIONS</b>Intraperitoneal administration of STS can prevent peritoneal adhesion and enhance local fibrinolysis in rats, and these effects may be mediated by TGF-β signaling pathway.</p>