Inhibition of aqueous extracts of Solanum nigrum (AESN) on oral cancer through regulation of mitochondrial fission

Abstract

The present study is designed to investigate the anti-oral cancer properties of Solanum nigrum on oral squamous cell carcinoma. S. nigrum is a Chinese herb used for suppression of various cancers. However, the inhibition of S. nigrum on oral cancer is unclear. Therefore, human oral squamous cancer cells (SCC)-4 were used to evaluate the effect of aqueous extracts of S. nigrum (AESN) on cancer cell proliferation, cell cycle, mitochondrial function and apoptosis. The SCC-4 cells were treated by AESN to evaluate the inhibition of cell proliferation and mitochondrial function in vitro. Our results suggested that AESN markedly increased reactive oxygen species production. AESN also promoted caspase-9 and caspase-3 activation and subsequent triggering of the mitochondrial apoptotic pathway. The inhibition of glucose uptake was alleviated mediated by a dose-dependent manner in SCC-4 cells with AESN treatment for 24 h, resulting in mitochondrial fission. These results suggested that AESN has potential to be used as a functional food in adjuvant chemotherapy for treating human oral cancer by suppression of mitochondrial function.

Keywords: Apoptosis; Mitochondrial fission; Mitochondrial function; Oral squamous cell carcinoma; Solanum nigrum.

Graphical abstract

Fig. 1

(A) Inhibitory effect of AESN on cell viability of SCC-4 after 24 h and 48 h treatment. Data were shown as mean ± SD (n = 3). Significantly difference was shown as various letters (between a, b, bc, c in 24 h or 48 h) (P < 0.05). (B) Induction of cell apoptosis and necrosis by AESN in SCC-4 cells. After 24 h treatment of AESN, the apoptotic event was detected by co-staining with Annexin V and PI using flow cytometry. Untreated cells were used as the control for double staining. ^a,b,cValues with one different letter superscript are significantly different from each other (P < 0.05).

Fig. 2

Induction of oxidative stress by AESN in SCC-4 cells. ROS level of SCC-4 cells treated with AESN for 24 h was measured by flow cytometry. Data were shown as mean ± SD (n = 3). ^a,bValues with one different letter superscript are significantly different from each other (P < 0.05).

Fig. 3

Inhibition of glucose uptake in SCC-4 cells treated by AESN induction for 24 h. The glucose uptake was assayed by flow cytometry. ^a,b,cValues with one different letter superscript are significantly different from each other (P < 0.05).

Fig. 4

The mitochondrial morphology of SCC-4 cells treated by AESN was observed by MitoTracker-Deep Red stain with confocal microscopy.

Fig. 5

Suppressions of CDK1 and cyclin B1 by AESN. CDK1 and cyclin B1 protein levels were detected by Western blot after treating with AESN in SCC-4 cells. Data were shown as mean ± SD (n = 3). ^a,b,cValues with one different letter superscript are significantly different from each other (P < 0.05).

Fig. 6

The potential mechanism of AESN on oral cancer.