The mRNA level of stromal cell-derived factor-1 (SDF-1) in the lung and the number of accumulated SDF-1-expressing CD11b<sup>+</sup>Gr1<sup>+</sup> MDSCs were elevated at an early stage in lung metastasis of C-X-C chemokine receptor type 4 (CXCR4)-expressing RM9 in an mPGES-1-dependent manner.
Consistent with this, PTGES knockdown also reduced the expression of CSC markers, tumor sphere formation, colony forming activity, tumorigenicity, and lung metastasis in vivo.
However, mPGES-1 overexpression seemed to be associated with the likelihood of subsequent pulmonary metastases and a lower tendency for developing bony metastases (P = .001 and P = .006, respectively).