Fig. 3.

Regulation of the cell cycle, apoptosis, and associated proteins by CXCR2. Silencing CXCR2 expression (CXCR2i) blocked cell cycle progression as indicated by an increased G₀-G₁ cell population and decreased G₂-M cell transition in all cell lines (A). Analysis of the cell cycle was done by flow cytometry with cells stained with propidium iodide. Assays were independently repeated three times in duplicate. Error bars, 95% confidence intervals. Further testing suggested that CXCR2 regulates the cell cycle by suppressing p21 (waf1/cip1) and promoting cyclin D1, CDK6, CDK2, cyclin A, and cyclin B1 (B). Abolishment of CXCR2 expression (CXCR2i) increased cell apoptosis by at least 2-fold (C), which possibly resulted from the increased phosphorylation of p53 (Ser15), increased expression of Puma and Bcl-xS, increased cleavage of PARP, and reduced expression of Bcl-xL and Bcl-2 (D). Error bars, 95% confidence intervals.