Anti-breast cancer and anti-angiogenic potential of a lichen-derived small-molecule: barbatolic acid

Abstract

Natural products have been used for centuries as the most potent remedies to cure many diseases including cancer diseases. Angiogenesis is defined as the formation of new capillaries from existing vessels and plays a key role in the tumorigenesis process. Barbatolic acid is a little known lichen-derived small-molecule. In the present study, barbatolic acid was isolated from the acetone extract of Bryoria capillaris, and its anti-breast cancer and anti-angiogenic potential was investigated using human umbilical vein endothelial cells (HUVECs), human breast ductal carcinoma (T-47D) and cisplatin-resistant BRCA2-mutated human breast TNM stage IV adenocarcinoma (HCC1428) cells. AlamarBlue™ cell viability, lactate dehydrogenase cellular membrane degradation and PicoGreen™ dsDNA quantitation assays were performed to determine the cytotoxic potential of barbatolic acid. Anti-angiogenic and anti-migratory activities were investigated using endothelial tube formation assay and scratch wound healing assay, respectively. Half maximal inhibitory concentration of barbatolic acid was found to be higher than 100 µM for HUVEC, HCC1428 and T-47D cells. The sub-cytotoxic concentrations such as 25 µM, 50 µM and 100 µM were applied to determine anti-angiogenic and anti-migratory activities. Although the sub-cytotoxic concentrations inhibited endothelial tube formation and cellular migration in a concentration depended manner, barbatolic acid was more effective on the migration of HCC1428 and T-47D breast cancer cells than the migration of HUVECs. Consequently, the findings suggest that barbatolic acid is a promising anti-angiogenic and anti-migratory agent and the underlying activity mechanisms should be investigated by further in vitro and in vivo experiments.

Keywords: Angiogenesis; Barbatolic acid; Breast cancer; Lichen acid; Migration.

Fig. 1

Chemical structure of barbatolic acid. a 2D structure and b 3D structure

Fig. 2

Antiproliferative activity of barbatolic acid on HUVEC, HCC1428 and T-47D cell lines. a AlamarBlue™ cell viability assay, b lactate dehydrogenase (LDH) cellular membrane degradation assay and c PicoGreen™ dsDNA quantitation assay. Data are presented as mean ± standard deviation and asterisks indicate significant difference from the control group by the Tukey test (p < 0.05)

Fig. 3

Anti-angiogenic activity of sub-cytotoxic concentrations of barbatolic acid. a Histogram represents quantification of number of junctions, total meshes area, number of segments, total branching length and total segment length in the tube formation assay. Data are presented as mean ± standard deviation and asterisks indicate significant difference from the control group by the Tukey test (p < 0.05) and b representative images of HUVEC tube formation are shown for the 12 h time point (10 × magnification, scale bar 200 µm)

Fig. 4

Anti-migratory activity of sub-cytotoxic concentrations of barbatolic acid. a Histogram represents wound closure of HUVEC, HCC1428 and T-47D cells at indicated time points during the scratch wound assay. Data are presented as mean ± standard deviation and asterisks indicate significant difference from the control group by the Tukey test (p < 0.05). b Representative images of HUVEC, HCC1428 and T-47D scratch wound assays are shown for the 0 h and 48 h time points (10× magnification, scale bar 200 µm)