In Vitro Cytotoxicity Evaluation of Plastoquinone Analogues against Colorectal and Breast Cancers along with In Silico Insights

Abstract

Colorectal cancer (CRC) and breast cancer are leading causes of death globally, due to significant challenges in detection and management. The late-stage diagnosis and treatment failures require the discovery of potential anticancer agents to achieve a satisfactory therapeutic effect. We have previously reported a series of plastoquinone analogues to understand their cytotoxic profile. Among these derivatives, three of them (AQ-11, AQ-12, and AQ-15) were selected by the National Cancer Institute (NCI) to evaluate their in vitro antiproliferative activity against a panel of 60 human tumor cell lines. AQ-12 exhibited significant antiproliferative activity against HCT-116 CRC and MCF-7 breast cancer cells at a single dose and further five doses. MTT assay was also performed for AQ-12 at different concentrations against these two cells, implying that AQ-12 exerted notable cytotoxicity toward HCT-116 (IC₅₀ = 5.11 ± 2.14 μM) and MCF-7 (IC₅₀ = 6.06 ± 3.09 μM) cells in comparison with cisplatin (IC₅₀ = 23.68 ± 6.81 μM and 19.67 ± 5.94 μM, respectively). This compound also augmented apoptosis in HCT-116 (62.30%) and MCF-7 (64.60%) cells comparable to cisplatin (67.30% and 78.80%, respectively). Molecular docking studies showed that AQ-12 bound to DNA, forming hydrogen bonding through the quinone scaffold. In silico pharmacokinetic determinants indicated that AQ-12 demonstrated drug-likeness with a remarkable pharmacokinetic profile for future mechanistic anti-CRC and anti-breast cancer activity studies.

Keywords: DNA binding; NCI-60; apoptosis; breast cancer; colorectal cancer; cytotoxicity; growth inhibition; pharmacokinetic determinants; plastoquinone.

Figure 1

Line of thought. Structures of target molecules (AQ-11, AQ-12, and AQ-15).

Figure 2

Graphical presentation of growth inhibition of the PQ analogue AQ-12 at five dose concentrations (0.01, 0.1, 1, 10, and 100 µM) after 48 h based on SRB assay at NCI.

Figure 2

Graphical presentation of growth inhibition of the PQ analogue AQ-12 at five dose concentrations (0.01, 0.1, 1, 10, and 100 µM) after 48 h based on SRB assay at NCI.

Figure 3

The cytotoxic effects of AQ-12 and cisplatin at varying concentrations (1, 3, 10, 30, and 100 μM) on MCF-7 and HCT-116 cells based on MTT assay. All descriptive data are expressed as the mean ± standard deviation (SD). All experiments were repeated three times.

Figure 4

(A) Alteration of HCT-116 and MCF-7 cells after treatment with IC₅₀ concentration of the control (DMSO), AQ-12, and cisplatin (B) for 12 h. The percentage of apoptosis, late apoptosis/necrosis, and necrosis (green, yellow, and red, respectively) cells (C) was determined by analyzing 100 randomly selected stained cells in each experiment (ns: not statistically significant). Data from three independent experiments were expressed as means ± standard deviation and p values were determined using Student’s test.

Figure 4

(A) Alteration of HCT-116 and MCF-7 cells after treatment with IC₅₀ concentration of the control (DMSO), AQ-12, and cisplatin (B) for 12 h. The percentage of apoptosis, late apoptosis/necrosis, and necrosis (green, yellow, and red, respectively) cells (C) was determined by analyzing 100 randomly selected stained cells in each experiment (ns: not statistically significant). Data from three independent experiments were expressed as means ± standard deviation and p values were determined using Student’s test.

Figure 5

Docking poses (A) and docking interactions (B) of AQ-11, AQ-12, and AQ-15 in the minor groove of the DNA double helix (AQ-11, AQ-12, and AQ-15 are shown in dark green, maroon, and turquoise, respectively) (PDB ID: 2GWA).

Figure 5

Docking poses (A) and docking interactions (B) of AQ-11, AQ-12, and AQ-15 in the minor groove of the DNA double helix (AQ-11, AQ-12, and AQ-15 are shown in dark green, maroon, and turquoise, respectively) (PDB ID: 2GWA).

Figure 6

Bioavailability radar for AQ-12 from the SwissADME web tool.

Figure 7

Boiled-egg graph of AQ-12 from the SwissADME web tool.

Figure 8

PQ analogues that were previously determined by our research group as potential anticancer agents against CRC and breast cancer.