Quantitative proteomics discloses monacolin K-induced alterations in triple-negative breast cancer cell proteomes and phosphoproteomes.

A positive prognosis of triple-negative breast cancer can be considered as one of the major challenges in clinical studies; accordingly, scientific research has the mission to find out novel chemotherapeutics to make it curable. In recent times, a good potential of dietary bioactive natural substances, called nutraceuticals, in suppressing cancer cell proliferation via gene expression regulation has been discovered: this effect and the lack of toxicity make nutraceuticals potentially effective agents against cancers. Monacolin K from red rice, a FDA-approved and well-tolerated compound generally employed to treat hypercholesterolemia, has been proved to have anti-proliferative and apoptotic effects in a wide panel of triple-negative breast cancers. Thus, an unbiased analysis of monacolin K-induced MDA-MB-231 cellular pathway alterations has been carried out by quantitative proteomics exploiting isobaric tags. Despite the positive modulation of some proteins already reported in the literature, an increased concentration of the tissue-type plasminogen activator PLAT has interestingly been found. This is a marker of good prognosis in mammary cancer, suggesting the anti-metastatic properties of this molecule as strongly associated with the alterations in the cytoskeleton organization and the consequent modulation of adhesion, motility and proteolysis. In accordance, some of the found monacolin K-induced phosphoproteome alterations have a tight connection to cell migration mechanisms. In this setting, the over-phosphorylation of Lamin A and of melanophilin induced by monacolin K has been very attractive. Moreover, monacolin K exerts its effect on the over-expression of the tissue inhibitor metalloproteinase-2 (TIMP-2), an endogenous metalloproteinase inhibitor. This protein modulates growth, migration and invasion of tumor cells and inhibits tumor angiogenesis.