A fundamental cause of cancer is changed properties of genetic material, which may deregulate normal development of the tissue or provide selective growth advantage to the tumor cell. This deregulation of cell proliferation results from altered production of a handful of proteins that play key roles in progression through the eukaryotic cell cycle. Some of these proteins include tumor suppressor genes or oncogenes.

However, no one general change or alteration of a critical gene has yet been found in all cancers. Using surgical material obtained from patients with various malignancies, we show that breast cancers and other solid tumors, as well as malignant lymphocytes from patients with lymphatic leukemia, show severe quantitative and qualitative alterations in cyclin E protein production independent of the S-phase fraction of the samples. Hence, these alterations represent a true difference between normal versus tumor tissue. In addition, in breast cancer, the alterations in cyclin E expression become progressively worse with increasing stage and grade of the tumor, suggesting its potential use as a new prognostic marker.

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This work was supported in part by a National Research Service Award CA08949-02 (to K. K.) from the NIH, a Breast Cancer Research Initiative Grant SC-DPH-3407-311-7051 from the Massachusetts Department of Health (to K. K.), a fellowship from the Science and Engineering Research Council (to E. L.) and a Public Health Service Grant GM 24571 (to A. B. R).