The detection of disseminated tumor cells in bone marrow from colorectal‐cancer patients by a cytokeratin‐20‐specific nested reverse‐transcriptase‐polymerase‐chain reaction is related to the stage of disease

The dissemination of cancer cells is a prerequisite in the development of micrometastases and solid metastases. Our previous examinations of these cells were based on immunocytological staining of tumor‐associated antigens and cytokeratins. We have now developed a highly sensitive and specific detection method based on a nested reverse‐transcriptase‐polymerase‐chain reaction (RT‐PCR) of cytokeratin‐20 (CK‐20) mRNA. Using this method, we examined the bone marrow of 57 patients with colorectal cancer and detected increasing numbers of CK‐20‐positive samples, depending on the UICC stage. Some 35% of all bone‐marrow samples tested positive for CK‐20: none were found in colorectal cancer stage I, 24% were in stage II, 31% in stage III and 71% in stage IV. Investigation of bone‐marrow specimens of patients with pancreatic cancer showed that 4 out of 11 patients were positive for CK‐20 mRNA. To confirm that sample positivity for CK‐20 expression was due to disseminated tumor cells, we examined bone marrow from a control group (n = 16) without apparent carcinoma. In this group, 15 out of 16 donors were CK‐20‐negative, while one donor with familial adenomatous polyposis showed a CK‐20‐specific signal. © 1996 Wiley‐Liss, Inc.