Correlation between cyclooxygenase and CXCL9 expression in human breast cancer tissue samples. Homogenates were prepared from deep-frozen breast cancer tissue samples and analyzed for COX-1 and COX-2 expression by western blot analysis. Panel a shows representative immunoblots with high (first lane) and low (second lane) expression of both enzymes. For both cyclooxygenase isoenzymes samples were divided into a low and a high expressing group (see text for further details), and CXCL9 concentration was determined in all samples by ELISA. There was a trend towards lower CXCL9 expression in the high COX-1 expressing group (b; n
= 22, n
= 21), but a significantly reduced CXCL9 concentration in highly COX-2 expressing breast cancers (c; n
= 12, n
= 17). COX-2 overexpressing breast cancers display only half of the average CXCL9 concentration found in low-expressing cancers (56.5% ± 13.9%). (b and c) CXCL9/total protein ratio is presented as arbitrary units with 1.0 set as the arithmetic mean of the low expressing group. Horizontal lines in b and c represent the arithmetic mean.