Investigation of the Mechanisms of Cytotoxic Activity of 1,3-Disubstituted Thiourea Derivatives

Abstract

Substituted thiourea derivatives possess confirmed cytotoxic activity towards cancer but also normal cells. To develop new selective antitumor agents, a series of 3-(trifluoromethyl)phenylthiourea analogs were synthesized, and their cytotoxicity was evaluated in vitro against the cell line panel. Compounds 1–5, 8, and 9 were highly cytotoxic against human colon (SW480, SW620) and prostate (PC3) cancer cells, and leukemia K-562 cell lines (IC50 ≤ 10 µM), with favorable selectivity over normal HaCaT cells. The derivatives exerted better growth inhibitory profiles towards selected tumor cells than the reference cisplatin. Compounds incorporating 3,4-dichloro- (2) and 4-CF3-phenyl (8) substituents displayed the highest activity (IC50 from 1.5 to 8.9 µM). The mechanisms of cytotoxic action of the most effective thioureas 1–3, 8, and 9 were studied, including the trypan blue exclusion test of cell viability, interleukin-6, and apoptosis assessments. Compounds reduced all cancerous cell numbers (especially SW480 and SW620) by 20–93%. Derivatives 2 and 8 diminished the viability of SW620 cells by 45–58%. Thioureas 1, 2, and 8 exerted strong pro-apoptotic activity. Compound 2 induced late apoptosis in both colon cancer cell lines (95–99%) and in K-562 cells (73%). All derivatives acted as inhibitors of IL-6 levels in both SW480 and SW620 cells, decreasing its secretion by 23–63%.

Proapoptotic effects of halogenated bis‐phenylthiourea derivatives in cancer cells

“…A group of 16 new diphenylthiourea derivatives were synthesized by condensation of aromatic amines with substituted phenylisothiocyanates, according to the one‐step reaction procedure indicated in our previous paper (Scheme 1). [ 43 ] Our earlier investigations [ 5,43,44 ] and conclusions of other authors [ 15,16,22,23,26,30,31,35,37 ] pointed out that the biological activity of thiourea compounds is affected by the presence of strong (‐NO 2 , ‐CF 3 , ‐CN) or weak (‐F, ‐Cl, ‐Br, ‐I) electron‐withdrawing functionalities ( R 2 ) on terminal aromatic rings, as well as an electron‐donating ‐OCH 3 group here. [ 32–34,40 ] The choice of the size of amine rings (R 1 )—mainly phenyl, but also bulky carbazolyl—was dictated by the high probability of finding potent derivatives among them.…”

“…They were added to 96‐well plates with seeded normal and cancer cells (1 × 10 4 cells per well) and incubated for 72 h. MTT analysis was performed according to a previous study. [ 43 ] Cell absorbance results were inserted into the formula for the relative MTT level (%). It allows us to calculate the viability of cells under the influence of the tested compounds.…”

“…They were added to 96-well plates with seeded normal and cancer cells (1 × 10 4 cells per well) and incubated for 72 h. MTT analysis was performed according to a previous study. [43] Cell absorbance results…”

“…Encouraged by our previous studies [ 43 ] and prompted by findings of other researchers, in this work we designed and synthesized a structurally differential series of halogenated 1,3‐bisphenylthioureas, to select small molecules with apoptosis‐inducing properties, able to induce caspases activity, increase the level of ROS and disturb the cell cycle in tumor cells.…”

“…[39] A variety of carbazole conjugates have been developed as potential anticancer agents, [40][41][42] and among them urea-derived compounds possessed potent broad-spectrum activity against a variety of solid tumors, acting as human DNA topoisomerase II inhibitors and apoptosisinducing agents. [40] Encouraged by our previous studies [43] and prompted by findings of other researchers, in this work we designed and synthesized a structurally differential series of halogenated 1,3-bisphenylthioureas, to select small molecules with apoptosis-inducing properties, able to induce caspases activity, increase the level of ROS and disturb the cell cycle in tumor cells.…”