PTGS2 and cancer: While co-expression of COX-2 with tumor metastatic phenotype has been observed in certain types of cancer[8], evidence of a direct role for COX-2 in carcinogenesis and neurodegenerative processes remains controversial, and, in the absence of a viable COX-2 in vivo imaging agent, hypotheses either way cannot be confirmed without the availability for non-invasive longitudinal studies.