Ponente
Descripción
Aminopeptidase N (APN, EC 3.4.11.2) is a metallopeptidase whose overexpression is correlated with inflammation, uncontrolled proliferation, invasion, metastasis, and angiogenesis of various cancers and solid tumors, thus constituting a well-established therapeutic target for the treatment of the disease [1]. Bufadienolides are polyhydroxysteroids that inhibit the Na+/K+ATPase pump, exhibit remarkable antitumor activity [2], and have a favorable chemical structure for use as potent and selective APN drugs [3]. Dose-response studies were performed to assess the potency of porcine APN inhibition by the bufadienolides cinobufagin and bufogenin, and both inhibited APN activity in a dose-dependent manner in the range of 10-7-10-6 M. The inhibition mechanism was classical reversible noncompetitive for cinobufagin (α=1) and tightly binding noncompetitive (TBI) for bufogenin. The enzyme:inhibitor bioinformatic models corroborated the experimental results of non-competitive inhibition mechanism. In selectivity studies of bufadienolides against other members of the M1 and M17 family of metallopeptidases, only porcine Acid Aminopeptidase (APAp) was inhibited with a classical reversible competitive inhibition mechanism. Given the high incidence and mortality rates of lung cancer in Cuba and worldwide, the effect of bufadienolides on the cell viability/metabolism of A549, H292 and LL2 tumor cells (APN+) was determined. Bufadienolides showed elevated cytotoxic effects in these lines in a dose-dependent manner, with the most drastic effects being observed in A549 (line with the highest APN activity).
