Lycopene and β-carotene induce growth-inhibitory and proapoptotic effects on pituitary tumor cells: the mechanism could involve Connexin 43
N. Haddad, A. Teodoro, N. Soares, F. Oliveira, R. Mattos, F. Gomes, M. Gadelha, L. Nasciutti & L. Miranda-Alves
Pituitary adenomas account for ~1015% of intracranial tumors and result in morbidity due to both altered hormonal patterns as well as side effects of therapy. Currently, great attention has been given to natural coumpouds from functional foods. Among these substances, we highlight that the consumption of carotenoids is associated with reduced risk of chronic diseases including cancer and vascular diseases. In this study we evaluate the influence of β-carotene and lycopene on cell viability, colony formation, cell cycle, apoptosis, intercellular communication and expression levels of Connexin 43 on mouse ACTH-secreting pituitary adenoma cells, the AtT-20 cells. Cells were cultivated with DMEM supplemented with 10% fetal bovine serum under an atmosphere of 5% CO2 at 37 °C, and incubated with different concentrations of carotenoids (0.5,1.25, 2.5, 5,10,20 and 40 μM) for 48 and 96 h. Using MTT assay, it was showed an important decrease of cell viability after 48 and 96 h with both lycopene and β-carotene treatments. For colony formation assay in 21-day period there was a significant decrease in clonogenic capacity. By flow cytometry, the cell cycle analysis revealed that β-carotene induced an accumulation of cells in S and G2/M phases after 96 h; furthermore, lycopene increased the proportion of cells in G0/G1 phase and decreased in S and G2/M phases also after 96 h. Using the annexin V-fluorescein isothiocyanate apoptosis detection kit, it was demonstrated that lycopene and β-carotene 5 and 10 μM concentrations induced apoptosis after 96 h. To evaluate intercellular communication, microinjections were performed with Lucifer Yellow and it was observed that a few coupled cells in control cells but none lycopene and β-carotene treatment. By the other hand, the phospho-Connexin 43 expression was increased under cell treatment. These results show that lycopene and β-carotene reduced cell viability, induced apoptosis, blocked the clonogenic capacity and promoted cell cycle arrest in AtT-20 cell culture by a mechanism that probably involves phospho-Connexin 43. This data suggests that these compounds may be in the future a new pharmacological approach for the treatment of pituitary adenomas.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This work was supported, however funding details unavailable.