Depsidones inhibit aromatase activity and tumor cell proliferation in a co-culture of human primary breast adipose fibroblasts and T47D breast tumor cells.

Naturally occurring depsidones from the marine fungus Aspergillus unguis are known to have substantial anti-cancer activity, but their mechanism of action remains elusive. The purpose of this study was to examine the anti-aromatase activity of two common depsidones, unguinol and aspergillusidone A, in a co-culture system of human primary breast adipose fibroblasts and hormonal responsive T47D breast tumor cells. Using this in vitro model it was shown that these depsidones inhibit the growth of T47D tumor cells most likely via inhibition of aromatase (CYP19) activity. The IC50 values of these depisidones were compared with the aromatase inhibitors letrozole and exemestane. Letrozole and exemestane had IC50 values of respectively, 0.19 and 0.14 µM, while those for Unguinol and Aspergillusidone A were respectively, 9.7 and 7.3 µM. Our results indicate that among the depsidones there maybe aromatase inhibitors with possible pharmacotherapeutical relevance.

Anti-aromatase effect of resveratrol and melatonin on hormonal positive breast cancer cells co-cultured with breast adipose fibroblasts.

Targeting the estrogen pathway has been proven effective in the treatment for estrogen receptor positive breast cancer. There are currently two common groups of anti-estrogenic compounds used in the clinic; Selective Estrogen Receptor Modulators (SERMs, e.g. tamoxifen) and Selective Estrogen Enzyme Modulators (SEEMs e.g. letrozole). Among various naturally occurring, biologically active compounds, resveratrol and melatonin have been suggested to act as aromatase inhibitors, which make them potential candidates in hormonal treatment of breast cancer. Here we used a co-culture model in which we previously demonstrated that primary human breast adipose fibroblasts (BAFs) can convert testosterone to estradiol, which subsequently results in estrogen receptor-mediated breast cancer T47D cell proliferation. In the presence of testosterone in this model, we examined the effect of letrozole, resveratrol and melatonin on cell proliferation, estradiol (E2) production and gene expression of CYP19A1, pS2 and Ki-67. Both melatonin and resveratrol were found to be aromatase inhibitors in this co-culture system, albeit at different concentrations. Our co-culture model did not provide any indications that melatonin is also a selective estrogen receptor modulator. In the T47D-BAF co-culture, a melatonin concentration of 20 nM and resveratrol concentration of 20 µM have an aromatase inhibitory effect as potent as 20 nM letrozole, which is a clinically used anti-aromatase drug in breast cancer treatment. The SEEM mechanism of action of especially melatonin clearly offers potential advantages for breast cancer treatment.

Effect of androgens on different breast cancer cells co-cultured with or without breast adipose fibroblasts.

About 70% of breast tumors express androgen receptors. In addition, there is clinical evidence suggesting that androgens can inhibit mammary epithelial proliferation. Vice versa, there is also significant evidence indicating that androgens can increase the risk of breast cancer via multiple mechanisms, e.g. direct conversion to estrogens that can bind to the estrogen receptor and thereby stimulate cell proliferation. We examined the effect of testosterone (T) and dihydroxytestosterone (DHT) on cell proliferation, pS2 and Ki-67 expression in three different breast cancer cell lines alone or in co-culture with primary human breast adipose fibroblasts (BAFs) obtained from breast cancer patients. In the co-cultures, T induced cell proliferation, pS2 and Ki-67 expression in the estrogen receptor positive (ER(+)) MCF-7 and T47D cells. This was not observed in the (ER(-)) MDA-MB-231 cells. The differences might be explained by the high expression of aromatase, which converts androgens to estrogens in BAFs followed by ER-mediated cell proliferation. In line with this absence of increased cell proliferation, pS2 and Ki-67 expression was observed in the presence of DHT, which is not a substrate for aromatase. In contrast, DHT caused a significant suppression of cell proliferation (68% and 38%), pS2 and Ki-67 expression in the (ER(+)) MCF-7 and T47D cells. More importantly, DHT decreased cell proliferation in (ER(-)) MDA-MB-231 cells by 38%. The results suggest that androgens that cannot be aromatized, like DHT, may provide a perspective for treatment of breast cancer patients, especially those with triple negative breast cancer.