Prostaglandin-endoperoxide synthase 2 (PTGS2), jagged canonical notch ligand 1 (JAG1), and guanylate cyclase 2C (GUCY2C) mRNA levels in serum and peripheral blood were found to be upregulated in metastatic CRC by ddPCR, while a correlation was found between the serum expression of GUCY2C and GUCY2C/PTGS2 and the therapeutic response [86]. The gene discussed is PTGS2; the disease is colorectal carcinoma.