A polo-like kinase 1 inhibitor enhances erastin sensitivity in head and neck squamous cell carcinoma cells in vitro

Abstract

Background: Polo-like kinase 1 (PLK1) is a critical therapeutic target in the treatment of head and neck squamous cell carcinoma (HNSCC). The objective of this study was to investigate the therapeutic effect of the combination of BI 2536, a PLK1 inhibitor, and erastin, a ferroptosis inducer, in HNSCC.

Methods: The proliferation, invasion, and migration abilities of Tu177 and FaDu cells upon exposure to BI 2536 and erastin, used in combination or alone, were tested. Fe²⁺, glutathione (GSH), and malondialdehyde (MDA) detection kits were used to determine whether the addition of BI 2536 enhanced the accumulation of Fe²⁺ and MDA, along with the depletion of GSH. Quantitative real-time PCR, western blot analyses were performed to investigate whether BI 2536 further altered the mRNA and expression level of ferroptosis genes. Furthermore, si PLK1 was used to investigate whether targeting PLK1 gene promoted erastin-induced ferroptosis.

Results: The combination of BI 2536 and erastin exerted a stronger cytotoxicity than treatment with a single agent. Compared with erastin treatment alone, the combination of BI 2536 and erastin lowered the ability of tumor cells to self-clone, invade, and migrate. BI 2536 enhanced the accumulation of Fe²⁺ and MDA, and the depletion of GSH. BI 2536 increased erastin-induced changes in ferroptosis-related gene mRNA and expression. Importantly, targeting PKL1 enhanced the anti-cancer effect of erastin.

Conclusion: BI 2536 enhanced the sensitivity of HNSCC cells to erastin, which provides a new perspective for cancer treatment.

Keywords: BI 2536; Erastin; HNSCC; PLK1.

Fig. 1

BI 2536 in combination with erastin inhibits Tu177 and FaDu cell viability. a The heatmaps of the changes in cell viability after co-treatment with BI2536 and erastin at different concentrations. b Cell viability at different time points after co-treatment with BI 2536 (5 nM) and erastin (10 μM) at the indicated concentrations. c Detection of cytotoxicity after the BI2536 (5 nM) and erastin (10 μM) combination for 48 h. **P < 0.01, ***P < 0.001

Fig. 2

BI 2536 combined with erastin inhibits Tu177 and FaDu cell clone formation. Cells were treated with BI 2536 (5 nM) and erastin (10 μM) for 48 h. The control group was treated with DMSO. a Cell growth status under different conditions. b The state of cell clone formation. ****P < 0.0001

Fig. 3

BI 2536 combined with erastin inhibits Tu177 and FaDu cell invasion and migration. Cells were treated with BI 2536 (5 nM) and erastin (10 μM) for 48 h. The control group was treated with DMSO. a Change in cell invasiveness (scale bar = 50 μm). b Change in cell migration ability (scale bar = 50 μm). c Comparison of cell migration rates (scale bar = 50 μm). ***P < 0.001

Fig. 4

Combining BI 2536 and erastin enhances the degree of ferroptosis. Tu177 and FaDu cells were treated with BI 2536 (5 nM) and erastin (10 μM) for 48 h. The control group was treated with DMSO. a Change in Fe²⁺ content. b Change in MDA content. c Change in GSH content. **P < 0.01,***P < 0.001

Fig. 5

Combining BI 2536 and erastin enhances changes in the mRNA level of ferroptosis genes. Detection of SLC7A11 (a), GPX4 (b), ACSL4 (c) mRNA with BI 2536 (5 nM) and erastin (10 μM) for 48 h. The control group was treated with DMSO. *P < 0.05, **P < 0.01

Fig. 6

Combining BI 2536 and erastin enhances changes in the expression of ferroptosis genes. Expression of ferroptosis genes after treatment of Tu177 and FaDu cells with BI 2536 (5 nM) and erastin (10 μM) for 48 h

Fig. 7

Targeting PLK1 in combination with erastin inhibits cell proliferation. Tu177 and FaDu cells were treated with si PLK1 (5 nM) and erastin (10 μM) for 48 h. The control group was treated with DMSO. a Changes in cell viability. b Detection of cytotoxicity. c Changes in the ability of cells to form clones. *P < 0.05, **P < 0.01

Fig. 8

Targeting PLK1 promotes erastin induced ferroptosis. Detection of SLC7A11 (a), GPX4 (b), ACSL4 (c) mRNA with si PLK1 (5 nM) and erastin (10 μM) for 48 h. The control group was treated with DMSO. *P < 0.05, **P < 0.01