Circulating Cytokeratin 18 Fragment M65-A Potential Marker of Malignancy in Colorectal Cancer Patients

Soluble cytokeratin 18 fragments (M30, M65) are released from human cancer cells during cell death and hold potential as biomarkers in colorectal cancer characterized by frequent metastatic spread. A total of 62 colorectal cancer and 27 control patients were included in the study. M65 (necrosis and apoptosis) and M30 (apoptosis) were quantified preoperatively (n = 62) and postoperatively (n = 31) using specific enzyme-linked immunosorbent assays. Presence of disseminated tumor cells (DTC) in the bone marrow was assessed by staining of A45-B/B3-positive cells in aspirates. M65 was significantly elevated in patients with International Union against Cancer stage I and IIA tumors compared to controls. A subgroup (19/31) exhibited a significant (p < 0.05) decrease of M65 after tumor surgery (503.9 +/- 230.7 to 342.6 + 94.8 U/l; -32.0 +/- 16.5%), in contrast to 12 patients who revealed higher M65 levels postoperatively (386.5 +/- 128.5 to 519.1 +/- 151 U/l; +37.4 +/- 32.3%). DTC in bone marrow were found in 10% (2/19) of patients with decreasing and 50% (6/12) of the patients with increasing M65 serum concentrations after surgery (p = 0.028). In conclusion, M65 as marker is likely to be valuable to identify patients with a high incidence of systemic disease.