Novel Bis-Thiazole Derivatives: Synthesis and Potential Cytotoxic Activity Through Apoptosis With Molecular Docking Approaches

Abstract

A series of bis-thiazoles 5a-g were synthesized from bis-thiosemicarbazone 3 with hydrazonoyl chlorides 4a-g. Reaction of 3 with two equivalents of α-halocarbonyl compounds 6-8, 10, and 12a-d afforded the corresponding bis-thiazolidines 9, 11, and 13a-d, respectively. Condensation of bis-thiazolidin-4-one 9 with different aromatic aldehydes furnished bis-thiazolidin-4-ones 14a-d. Compounds 5a-g, 9, and 13a,c,d were screened in vitro for their cytotoxic activities in a panel of cancer cell lines. Compounds 5a-c, 5f-g, and 9 exhibited remarkable cytotoxic activities, especially compound 5c with potent IC₅₀ value 0.6 nM (against cervical cancer, Hela cell line) and compound 5f with high IC₅₀ value 6 nM (against ovarian cancer, KF-28 cell line). Compound 5f-induced appreciated apoptotic cell death was measured as 82.76% associated with cell cycle arrest at the G1 phase. The apoptotic pathways activated in KF-28 cells treated with 5a, 5b, and 5f were further investigated. The upregulation of some pro-apoptotic genes, bax and puma, and the downregulation of some anti-apoptotic genes including the Bcl-2 gene were observed, indicating activation of the mitochondrial-dependent apoptosis. Together with the molecular docking studies of compounds 5a and 5b, our data revealed potential Pim-1 kinase inhibition through their high binding affinities indicated by inhibition of phosphorylated C-myc as a downstream target for Pim-1 kinase. Our study introduces a set of bis-thiazoles with potent anti-cancer activities, in vitro.

Keywords: Pim-1 kinase; apoptosis; bis-thiazoles; cytotoxic; docking; hydrazonoyl chlorides.

Chart 1

Some thiazole-based synthetic commercial drugs in the market.

Chart 2

Some 4-thiazolidinone–based synthetic commercial drugs.

Scheme 1

Synthesis of 1,4-bis((5-(arylazo)thiazol-2-ylidene)hydrazono)cyclohexane 5.

Scheme 2

Synthesis of cyclohexane-1,4-diylidene-bis-thiazolidine derivatives 9 and 11.

Scheme 3

Synthesis of 1,4-bis((4-arylthiazol-2-ylidene)hydrazono)cyclohexanes 13a–d.

Scheme 4

Synthesis of 1,4-bis((5-arylidene-thiazolidin-2-ylidene)hydrazono)cyclohexanes 14a–d.

FIGURE 1

Effect of selected compounds on cell cycle phases in KF-28 cell lines. (A) Representative cytographs show the effect of vehicle and compounds 5a–c, 5f, 5g, and 9 on the different cell cycle phases of KF-28 cells when treated with each compound for two days. (B) Collected results show the effect of each compound on different populations at each cell cycle phase.

FIGURE 2

Some compounds induce apoptosis in KF-28 and A2780 cells. Average percentage of annexin-positive cells from KF-28 (A) and A2780 (B) cells treated with DMSO and different compounds, 5a, 5b, 5c, 5f, and 9, in parallel with the standard drug, cisplatin (10 μM), treatment for 48 h. Values are presented as mean ± SE.

FIGURE 3

Quantitative RT-PCR result analysis of the apoptosis-related genes: p53, bax, puma, caspases 3, 8, and 9, Bcl-2, and Pim-1 kinase, respectively, in KF-28 cells treated with some selected compounds 5a, 5b, and 5f for 48 h of incubation.

FIGURE 4

Binding disposition and interaction analysis of the docked compounds 5a (A) and 5b (B), inside the Pim-1 kinase protein.

FIGURE 5

Highlighted pharmacophoric regions for the active compounds 5a, 5b, and 5f, respectively (top to down).

FIGURE 6

Western blot of C-myc expression in KF-28 cells treated either with DMSO or compounds 5a–c, 5f, and 9 for two days. The cell lysates were developed and fractionated by 15% SDS-PAGE, blotted, and probed with anti-C-myc Ab to show its relative expression. Appreciated downregulation of C-myc expression under treatment with 5f, 5b, and 5c is shown. The lower band is GAPDH which was used as a loading control.