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Development of in vitro Diagnostics for Cancers

MBL has made substantial achievements as a manufacturer of in vitro diagnostics for the detection of autoimmune diseases. Hereafter, cancer will be targeted as our priority areas in the development of diagnostics. Commonly used cancer markers such as CEA (carcinoembryonic antigen), AFP (alpha-fetoprotein), and CA19-9 (carbohydrate antigen 19-9) have been developed in the 1960s and 1970s. Although other cancer markers have been developed since then, none are comparable to these three. The field of molecular biology has made dramatic progress in the 50 years that followed the development of these markers. However, the development of cancer markers did not advance with the progress of molecular biology, which is the foundation of modern medicine. Conversely, opportunities for the development of the next generation of cancer diagnostics, which depend on researches pertaining to the molecular biology of cancer, seem to have matured. Taking this into consideration, MBL has focused its efforts on the development of cancer diagnostics.

Development of Anti-p53 Autoantibody Detection Kit

We took advantage of our strength in the field of autoimmune diseases and developed an assay kit for the diagnosis of cancers by measuring the serum levels of autoantibodies against cancer-specific antigens. Considerably high levels of autoantibodies against the well-known tumor suppressor protein p53 can be detected in the serum of patients with certain cancers. On the basis of clinical trials performed at many medical facilities all over Japan, including Chiba University Hospital, we developed an ELISA assay kit (MESACUP® Anti-p53 Test) for the detection of autoantibodies in esophageal cancer, breast cancer, and colorectal cancer and received the approval for its production for use in in vitro diagnostics from Ministry of Health, Labour and Welfare, Japan. This kit has been marketed since 2006 and is useful in the early diagnosis of these cancers.

Development of a Complementary Cancer-related Autoantibodies Detection Kit

Previous studies have demonstrated that nearly half of many types of cancers have mutations in p53. Mutant p53 proteins lost the ability of tumor suppression and accumulated inside the cells, as opposed to normal p53 proteins, which have a rapid metabolic turnover. Leakage of the accumulated p53 outside the cells as a result of cell death leads recognition by the immune system as a foreign substance and subsequent production of anti-p53 antibodies. Thus, there is a strong causality between p53 mutations and the incidence of cancers. Anti-p53 autoantibodies are believed to be the diagnosis marker of cancers at their early stages. Results of clinical trials have revealed that while other cancer markers increase as cancers advance in stage, anti-p53 autoantibodies are present at a certain level at the early stages of the cancer and remain at approximately 30% even during progression of the cancer. This is because approximately half of certain cancers are associated to mutations in other tumor suppressor proteins such as Rb. Therefore, to overcome the limitation of the anti-p53 autoantibody detection kit, we are developing a new kit for the detection of complementary cancer-related autoantibodies. MBL employs SEREX (SErological analysis of Recombinant cDNA EXpression libraries) to select cancer-specific autoantibodies. Among the cancer-related autoantibodies, we identified promising and complementary autoantibodies useful in cancer diagnosis. Their antigens are probably associated with carcinogenic mechanisms other than p53 mutations. These autoantibodies additively detect cancers and can increase the positive rate in combination with anti-p53 autoantibodies. We are developing a new diagnosis kit with a higher detection rate in cancer patients than our anti-p53 autoantibody detection kit. The detection rate of our current combined assay system is over 60% for esophageal cancer. In the future, we aim to conduct clinical trials to confirm the usefulness of our new kit for the early detection of cancers in comparison to those with existing cancer markers.

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