ORIGINAL ARTICLE

Upregulation of tumour associated antigen RCAS1 is implicated in high stages of colorectal cancer

K Leelawat¹, T Watanabe², M Nakajima², S Tujinda³, C Suthipintawong³ and V Leardkamolkarn¹

¹ Department of Anatomy, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
² Department of Medicine and Bioregulatory Science, Kyushu University, Japan
³ Department of Pathology, Rajavithi Hospital, Thailand

Correspondence to:
Correspondence to:
Dr V Leardkamolkarn, Department of Anatomy, Faculty of Science, Mahidol University, Rama 6, Bangkok 10400, Thailand;
scvlk{at}mahidol.ac.th

Background: RCAS1 (receptor binding cancer antigen expressed on SiSo cells) is a tumour associated antigen. It is involved in immune evasion by tumour cells, by binding to receptors on cells involved in the immune response, such as T cells and natural killer cells, and inducing apoptosis. High expression of RCAS1 has been demonstrated immunohistochemically in tumours of the cervix, breast, lung, and stomach; however, the expression of RCAS1 has never been investigated in colorectal cancer.

Aims: To investigate the expression of RCAS1 in colorectal cancer and identify at which stages of colorectal carcinogenesis it is expressed.

Methods: Sixty surgically resected colorectal cancer specimens obtained from Rajavithi Hospital, Bangkok, Thailand were studied. RCAS1 expression was detected immunohistochemically using monoclonal anti–RCAS1 antibody. RCAS1 mRNA expression was also investigated by reverse transcription polymerase chain reaction in the freshly isolated tissues, and serum RCAS1 was measured by enzyme linked immunosorbent assay.

Results: Staining for the RCAS1 protein was intense in high stages of colorectal cancer, but weak in normal tissues. The RCAS1 mRNA results correlated with the immunohistochemistry results. Positive serum RCAS1 concentrations were found in 10 of 18 patients with stage II disease and 12 of 32 with stage III and IV, but not in patients with stage I disease. All lymph node and liver metastases showed high expression of RCAS1 protein.

Conclusions: RCAS1 appears to be upregulated in high stages of colorectal cancer, both in the serum and the tissue. RCAS1 expression might be a useful additional criterion for staging this cancer.

Keywords: RCAS1; colorectal cancer; immune evasion; liver metastases; lymph node metastases

Abbreviations: ELISA, enzyme linked immunosorbent assay; PBS, phosphate buffered saline; RCAS1, receptor binding cancer antigen expressed on SiSo cells; RT–PCR, reverse transcription polymerase chain reaction

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