Novel Thiazolidinone/Thiazolo[3,2- a]Benzimidazolone-Isatin Conjugates as Apoptotic Anti-proliferative Agents Towards Breast Cancer: One-Pot Synthesis and In Vitro Biological Evaluation

Abstract

In connection with our research program on the development of new isatin-based anticancer candidates, herein we report the synthesis of two novel series of thiazolidinone-isatin conjugates (4a⁻n) and thiazolo[3,2-a]benzimidazolone-isatin conjugates (7a⁻d), and in vitro evaluation of their antiproliferative activity towards two breast cancer cell lines; triple negative MDA-MB-231, and MCF-7. Compounds 4m and 7b emerged as the most active congeners against MDA-MB-231 cells (IC₅₀ = 7.6 ± 0.5 and 13.2 ± 1.1 µM, respectively). Compounds 4m and 7b were able to provoke apoptosis in MDA-MB-231 cells, evidenced by the up-regulation of Bax and down-regulation of Bcl-2, besides boosting caspase-3 levels. Hybrid 4m induced a fourfold increase in the percentage of cells at Sub-G₁, with concurrent arrest in G₂-M phase by 2.5-folds. Furthermore, hybrid 4m resulted in a sixfold increase in the percentage of annexin V-FITC positive apoptotic MDA-MB-231 cells as compared with the control. Moreover, the cytotoxic activities of the active conjugates were assessed towards two nontumorigenic cell lines (breast MCF-10A and lung WI-38) where both conjugates 4m and 7b displayed mean tumor selectivity index: 9.6 and 13.9, respectively. Finally, several ADME descriptors were predicted for the active conjugates via a theoretical kinetic study.

Keywords: QSAR; anticancer; apoptosis; isatin-thiazolidinone hybrids; triple-negative breast cancer.

Figure 1

Structures of isatin-based approved anticancer drugs (II and III), some reported isatin-based hybrids with potent antiproliferative activity against breast cancer (VII–IX), and the target conjugates (4a–n and 7a–d).

Scheme 1

Synthesis of target hybrids 4a–n; reagents and conditions: (i) glacial acetic acid/sodium acetate/reflux 3–4 h.

Scheme 2

Synthesis of target hybrids 7a–d; Reagents and conditions: (i) glacial acetic acid/sodium acetate/reflux 2 h; (ii) ethanol/ KOH/reflux 1 h; (iii) acetic anhydride/pyridine 100 °C 1 h.

Figure 2

Effect of compounds 4m and 7b on the protein levels of (A) Bax; (B) Bcl-2; (C) Bax/Bcl2 ratio in MDA-MB-231 cells treated with the compounds at their IC₅₀ concentrations against control (1% DMSO). Data are mean ±S.D. (n = 3). The experiment was done in triplicates. * Significantly different from control at p < 0.05.

Figure 3

Effect of compounds 4m and 7b on the protein levels of caspase-3 in MDA-MB-231 cells treated with the compounds at their IC₅₀ concentrations against control (1% DMSO). Data are mean ±S.D. (n = 3). The experiments were done in triplicate. * Significantly different from control at p < 0.05.

Figure 4

Effect of compound 4m on the phases of cell cycle of MDA-MB-231 cells. * Significantly different from control at p < 0.05. (Two-way ANOVA test).

Figure 5

Effect of compound 4m on the percentage of annexin V-FITC-positive staining in MDA-MB-231 cells. The experiments were done in triplicates. The four quadrants identified as: LL, viable; LR, early apoptotic; UR, late apoptotic; UL, necrotic. * Significantly different from control at p < 0.05. (One-way ANOVA test).