LGR5 and colorectal carcinoma: Despite these limitations, studies have turned to combining CTCs with other circulating biomarkers such as CA19-9 [50,58], or by expanding protein marker phenotypic profiling, including the expression of cyclooxygenase-2 (COX2), leucine rich repeat containing G-protein coupled receptor 5 (LGR5), or caudal-type homeobox 2 (CDX2); in CTCs in CRC [59,60,61]; or mesenchymal markers, Vimentin, or Twist in PDAC [51,53,62,63].