To provide the identification, isolation, and usage of a new marker for a tumor or a cancer, which is important for the diagnosis, treatment, and prevention of a cancer.

The present invention is related to an isolated nucleic acid molecule encoding an RELP protein. The molecule may be a nucleic acid having a specific sequence or a nucleic acid encoding a protein having a homology of at least 70% to a peptide containing a specific sequence of amino acids. Further, the present invention relates to a protein whose existence, concentration or expression level in a biological sample is useful for the prognosis or diagnosis of a tumor, a cancer or a related symptom. The method for detecting the symptom of the tumor or cancer comprises the detection of a polypeptide, a protein or a nucleic acid which has the specific sequence and correlates the existence of the tumor or cancer with the existence or the concentration of a RELP molecule in a biological sample.