Specific Protein Seen to Suppress Start of Breast Cancer in Mice After Giving Birth

Specific Protein Seen to Suppress Start of Breast Cancer in Mice After Giving Birth
Researchers, working with mice, reported that a specific protein stopped the proliferation of mammary cells during pregnancy, a cause of the formation of breast tumors. This protein may be of interest in breast cancer in people, specifically those with luminal B breast cancer. The study, “Deficiency of X-Linked Protein Kinase Nrk during Pregnancy Triggers Breast Tumor in Mice,” was published in the American Journal of Pathology. An increase in estrogen production in breast adipose tissue has been linked to cancer development in postmenopausal women. Indeed, one of the most characteristic features of breast cancer is its estrogen dependency, and a growing body of clinical evidence indicates that estrogen plays a critical role in the development of this cancer. Likewise, estrogen-dependent proliferation of mammary epithelial cells takes place during pregnancy — which is required to enable lactation — although it is known to stop in a pregnancy's later stages. How this cell proliferation — from start to end — is regulated in the body, however,  is poorly understood. For this reason, researchers in Japan focused on a protein kinase that is encoded in the X chromosome, called  Nrk. Professor Masayuki Komada, from the Department of Biological Sciences at the Tokyo Institute of Technology, and colleagues studied the workings of the Nrk protein using mice with an Nrk gene altered so that they were incapable of producing the Nrk protein. Nrk-mutant mice who had repetitive
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