Antiproliferative and Tubulin-Destabilising Effects of 3-(Prop-1-en-2-yl)azetidin-2-Ones and Related Compounds in MCF-7 and MDA-MB-231 Breast Cancer Cells

Abstract

A series of novel 3-(prop-1-en-2-yl)azetidin-2-one, 3-allylazetidin-2-one and 3-(buta-1,3-dien-1-yl)azetidin-2-one analogues of combretastatin A-4 (CA-4) were designed and synthesised as colchicine-binding site inhibitors (CBSI) in which the ethylene bridge of CA-4 was replaced with a β-lactam (2-azetidinone) scaffold. These compounds, together with related prodrugs, were evaluated for their antiproliferative activity, cell cycle effects and ability to inhibit tubulin assembly. The compounds demonstrated significant in vitro antiproliferative activities in MCF-7 breast cancer cells, particularly for compounds 9h, 9q, 9r, 10p, 10r and 11h, with IC50 values in the range 10–33 nM. These compounds were also potent in the triple-negative breast cancer (TBNC) cell line MDA-MB-231, with IC50 values in the range 23–33 nM, and were comparable with the activity of CA-4. The compounds inhibited the polymerisation of tubulin in vitro, with significant reduction in tubulin polymerization, and were shown to interact at the colchicine-binding site on tubulin. Flow cytometry demonstrated that compound 9q arrested MCF-7 cells in the G2/M phase and resulted in cellular apoptosis. The antimitotic properties of 9q in MCF-7 human breast cancer cells were also evaluated, and the effect on the organization of microtubules in the cells after treatment with compound 9q was observed using confocal microscopy. The immunofluorescence results confirm that β-lactam 9q is targeting tubulin and resulted in mitotic catastrophe in MCF-7 cells. In silico molecular docking supports the hypothesis that the compounds interact with the colchicine-binding domain of tubulin. Compound 9q is a novel potent microtubule-destabilising agent with potential as a promising lead compound for the development of new antitumour agents.

Butadienyl Ketene: An Unexplored Intermediate in Organic Synthesis

“…19 Wang et al designed and synthesized three series of 3dienyl--lactams as inhibitors targeting a binding site of colchicine. 20 The imines 16 were accessed via butadienyl ketene generated in situ by the action of sorbic acid and suitable base in dichloromethane to afford 3-(buta-1,3dien-1-yl)azetidin-2-ones 17 (Table 5). Derivatives 17 also exhibited in vitro antitumor activity against the MCF-7 breast cancer cell line, with IC 50 values of 23-33 nM.…”

“…Derivatives 17 also exhibited in vitro antitumor activity against the MCF-7 breast cancer cell line, with IC 50 values of 23-33 nM. 20 Scheme 3 [4+2] cycloaddition of butadienyl ketene 4 and 1,3-diazabuta-l,3-dienes 25…”