We have ruled out PGE2 itself as the potential factor (Figure 6) as exogenous PGE2 alone did not induce COX-2 mRNA expression by control monocytes to the same extent as the conditioned medium, and PGE2 itself was not in high enough concentrations in tumor-conditioned media to be responsible for the levels of enhanced monocyte COX-2 expression we observed. Here, PTGS2 is linked to neoplasm.