Abstract
Introduction: Calcium-binding tyrosine phosphorylation-regulated protein (CABYR) is expressed in the human germ line but not in adult human tissues, thus, it is considered a cancer testis protein. The aim of this study is to evaluate the CABYR isoforms: a/b and c mRNA expression in colorectal cancer (CRC) and to determine if these proteins hold promise as vaccine targets.Materials and Methods: CABYR mRNA expression in a set of normal human tissues, including the testis, were determined and compared using semi-quantitative PCR. As regards the tumor and normal mucosal samples from study patients, RNA was extracted and cDNA generated after which quantitative PCR was carried out. Analysis of CABYR protein expressions by immunohistochemistry in tumor and normal colon tissues was also performed.Results: A total of 47 paired CRC and normal tissue specimens were studied. The percent of patients with a relative expression ratio of malignant to normal (M/N) tissues over 1 was 70% for CABYR a/b and 72% for CABYR c. The percent with both a M/N ratio over 1 and expression levels over 0.1% of testis was 23.4% for CABYR-a/b and 25.5% for CABYR c. CABYR expression in tumors was further confirmed by immunohistochemistry.Conclusions: CABYR a/b and c hold promise as specific immunotherapy targets, however, a larger and more diverse group of tumors (Stage 1-4) needs to be assessed and evaluation of blood for anti-CABYR antibodies is needed to pursue this concept.
Highlights
Calcium-binding tyrosine phosphorylation-regulated protein (CABYR) is expressed in the human germ line but not in adult human tissues, it is considered a cancer testis protein
A total of 47 patients who underwent elective colorectal cancer resection were included in this study
RT-Polymerase chain reaction (PCR) analysis demonstrated prominent expression of CABYR a/b and c in most colorectal cancer (CRC) tumors when compared to adjacent normal colon tissue
Summary
Calcium-binding tyrosine phosphorylation-regulated protein (CABYR) is expressed in the human germ line but not in adult human tissues, it is considered a cancer testis protein. The last 15 years has seen the development of immunotherapies for colorectal cancer These advances include FDA approval of a number of monoclonal antibodies, which target epidermal growth factor receptor, vascular endothelial growth factor, and, most recently Programmed cell Death 1 protein (PD-1) or PD-1 ligand [5, 6]. Despite these advances as well as much research and effort, an effective tumor vaccine has not yet been developed. Regardless, investigators continue to search for new tumor cell target antigens that hold promise as vaccine targets
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