Identification of robust diagnostic and therapeutic target molecules for human malignancy is still an important issue. If we identify novel proteins which play a stem-line role for cellular transformation or aggravation of malignancy, it could give us a clue to diagnose a tumor in an earlier stage and to develop more reliable therapeutic tools. For this purpose, we have screened abnormally expressed genes in various human cancers by differential display RT-PCR. One of the overexpressed genes was a human cervical cancer oncogene (HCCR). HCCR was not only identified in cervical cancer tissues, but also found to be overexpressed in various human malignancies such as leukemia/lymphoma, breast, kidney, stomach, colon, liver and ovarian cancer. This molecule appeared to be a negative regulator of p53. In this paper, we discuss the biological functions of HCCR molecules and its implications for early diagnosis and future development of therapeutic devices of cancer.