ORIGINAL ARTICLE

Discordant quantitative detection of putative biomarkers in nodal micrometastases of colorectal cancer: biological and clinical implications

S L Kong¹, M Salto-Tellez², A P K Leong³, Y H Chan⁴ and E S C Koay¹

¹ Department of Pathology, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260
² Molecular Diagnosis Centre, Department of Laboratory Medicine, National University Hospital, Singapore 119074
³ Department of Surgery, National University Hospital, Singapore
⁴ Clinical Trials and Epidemiology Research Unit, 226 Outram Road, Singapore 169039

Correspondence to:
Correspondence to:
Dr E S C Koay
Department of Pathology, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260; patkoaye{at}nus.edu.sg

Aims: Nodal expression of the carcinoembryonic antigen (CEA), cytokeratin 20 (CK20), and guanylyl cyclase C (GCC) genes was measured in tandem in patients with colorectal cancer (CRC) to assess whether there would be sufficient agreement between these markers in their ability to detect micrometastasis to qualify one of them as a universal marker, and whether frozen and paraffin wax embedded tissues would yield similar results.

Methods: One hundred and seventy five frozen lymph nodes (FT) and 158 formalin fixed, paraffin wax embedded lymph nodes (PET) from 28 CRC cases were analysed using gene specific quantitative real time polymerase chain reaction, carried out on the LightCycler® system with SYBR Green chemistry.

Results: There was significant disparity in positive detection of the three biomarkers in FT versus PET, with notable agreement achieved only for CEA (66.6%) in FT versus PET in Dukes’ B disease, and between CK20 and GCC (44.6%) in FT, also in Dukes’ B disease. One patient with full concordance in all three tumour markers with both tissue types suffered a relapse and died within two years of follow up.

Conclusions: There was considerable discordance in the positive detection of the three tumour markers in both tissue types (FT versus PET). This brings into question whether using a single tumour marker to detect micrometastasis in one tissue type (FT or PET) is adequately representative, and challenges the concept of universal markers for molecular CRC metastatic detection. Multiple tumour markers would predict more accurately the metastatic potential of Dukes’ B CRCs.

Abbreviations: CEA, carcinoembryonic antigen; CK20, cytokeratin 20; CRC, colorectal cancer; Ct, crossing point; FT, frozen tissue; GCC, guanylyl cyclase C; LN, lymph node; PBMN, peripheral blood mononuclear; PCR, polymerase chain reaction; PET, paraffin wax embedded tissue; R-PCR, quantitative real time polymerase chain reaction; RT, reverse transcriptase

Keywords: metastasis; real time polymerase chain reaction; tumour marker; mRNA; lymph nodes

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