The soluble p51 protein in cancer detection

The soluble p51 antigen alone, or in combination with the soluble p66 (as a preparation of the soluble tumourassociated antigens, sTAA) was shown to be useful in both cancer detection, prevention and therapy. Cancer detection: In colon cancer patients with recurrent cancer, the blood level of p51 increased whereas the blood level of p66 did not change. The correlation and regression coefficients between the serum level of p51 protein and the progress in colon cancer were 0.48 and 0.88, respectively. In patients with melanoma, development of metastases significantly increased the blood levels of p51. The method was shown to be highly sensitive (92 to 96%) and moderately specific (42 to 65%) for the detection of different types of cancer, such as of the colon, uterus, ovary and breast, as well as melanoma. Cancer prevention and therapy: This was performed using a preparation of both p66 and p51 antigens. sTAA have both tumour-preventive and tumour-suppressive effects on chemically-induced cancers of the colon, skin and mammary glands in rats and mice. sTAA promote suppression of rat mammary tumours by different anticancer drugs, such as cyclophosphamide, tamoxifen and 5-fluorouracil. This effect was shown to be connected with activation of the host’s immune system, especially that which is responsible for the activity of T and B lymphocytes. Conclusion: We propose the follow-up of cancer patients in order to verify, as early as possible, recurrent cancer and perform preventive therapy of suspect cancer patients with their own sTAA as a kind of autoimmunotherapy. Moreover, in combination with anticancer drugs, sTAA may serve as a new tool in prevention of the toxic side-effects of chemotherapy. Cancer remains one of the most fatal illnesses known. In industrial countries, cancer together with heart disease are the leading causes of death (1). After a prolonged "war on cancer" involving ever stronger anticancer drugs, radical treatment strategies and advances in our understanding of the molecular mechanisms of oncogenesis, the mortality rates from cancer continue to rise. In the USA, for example, about one million people died of cancer in 1991 (2). In Europe, 1.4 million cancers were diagnosed in 1990 resulting in close to 900,000 registered deaths (3). The number of primary cancer patients worldwide reaches several millions. By the year 2010, approximately 1.1 million Europeans are predicted to succumb to cancer (4). During recent years, cancer prevalence has not changed, despite enormous efforts to improve the diagnostic and therapeutic measures (5). Detecting cancer when a tumour already exists is not complicated; moreover, in most cases, detection cannot increase patient survival. The most challenging task is to recognize the disease in its earliest, precancerous stages, thereby providing an opportunity for prevention strategies. Detecting cancer in its earliest stages and preventing progression of the disease are the two main aims of the new approach to monitoring cancer patients. We found that soluble cell surface tumour-associated antigens (sTAA) can successfully serve both these aims. The soluble p51 protein in cancer detection Vast efforts have been made to find a cancer-specific factor that can be used as a highly specific and reliable cancer marker. Unfortunately, despite the wide use of serological determinations of TAA or their antibodies for cancer detection (6, 7), almost none of the commercially utilized markers can satisfy the physicians' requirements. An ideal tumour marker should be found only in the blood of cancer patients. In reality, cancer is indicated by the high expression of sTAA, which are also found in healthy people. 591 Correspondence to: Professor I. Zusman, The Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel. e-mail: [email protected]