Lauroside B, a Megastigmane Glycoside from Laurus Nobilis(Bay Laurel) Leaves, Induces Apoptosis in Human MelanomaCell Lines by Inhibiting NF-kB Activation

Malignant melanoma is a highly aggressive tumor that frequently resists chemotherapy, so the search for new agents for its treatment is of great importance. In the present study, the antiproliferative propensity against human melanoma cell lines of lauroside B (1), a megastigmane glycoside isolated from Laurus nobilis (bay laurel) leaves, was investigated. This compound suppressed the proliferation of three human melanoma cell lines, namely, A375, WM115, and SK-Mel-28. The 1-induced inhibition of humanmelanoma cell proliferationwas due to the induction of apoptosis, as demonstrated by FACS analysiswith annexin V/PI staining and confirmed by activation of caspase-3 and by the cleavage of poly(ADP-ribose) polymerase (PARP). Growing evidence implicates NF-κB as an important contributor to metastasis and increased chemoresistance of melanoma. Thus, it was hypothesized that 1-induced apoptosis could be associatedwith suppressionofNF-κB activation. The results showed that exposure of human melanoma cells to 1 inhibited IκB-R degradation and constitutive NF-κB DNA-binding activity as well as the expression, regulated by NF-κB, of two antiapoptotic genes, XIAP and c-FLIP. Induction of apoptosis by 1 in human aggressive melanoma cell lines has a potential high biological value.