Kallikrein-related peptidases (KLKs) are serine proteases that have been considered as important biomarkers in cancer biology. It has been previously shown that KLK3, also known as a specific prostate antigen because it was initially found in the human prostate, is also expressed in human breast tissue. However, its role in breast cancer has not yet been clarified. Chronic low-grade inflammation (CLGI), defined as “the chronic production, but a low-grade state, of inflammatory factors” is a common route of several non-communicable diseases such as obesity and cancer. It is known that inflammation can increase the risk of some types of cancer, including breast cancer, which is the most commonly diagnosed cancer among women worldwide. CLGI is characterized by slightly elevated proinflammatory cytokines such as IL-1 beta and IL-8, among others, in systemic circulation, the levels of which are at 1000 times lower than those observed in acute inflammation.Our goal was to explore if the CLGI condition may modify the expression levels of KLK3 and KLK4. For that reason, we treated breast cancer cells with a low dose of cytokines, similar to those found in the sera of breast cancer patients, according to the initial and advanced stages of the disease. At date, our preliminary results show that a chronic proinflammatory state is associated to the release of high levels of KLK3 and KLK4 from estrogen-sensitive breast cancer cells.