Targeting Stearoyl-CoA Desaturase 1 Through PI3K-AKT-mTOR Signaling in Head and Neck Squamous Cell Carcinoma

Abstract

Objective: Stearoyl-coenzyme A desaturase 1 (SCD1) is a key enzyme in fatty acid metabolism and has been implicated in cancer progression, including head and neck squamous cell carcinoma (HNSCC). The phosphoinositide 3-kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) signaling pathway is a critical regulator of cellular metabolism and survival in cancer. This study investigates the crosstalk between SCD1 inhibition and the PI3K-AKT-mTOR pathway, highlighting the therapeutic potential of targeting SCD1 in HNSCC.

Study design: Basic science.

Setting: Laboratory.

Methods: Four HNSCC cell lines were utilized to evaluate the relationship between SCD1 and the mTOR signaling pathway. Cell viability was assessed following treatment with various mTOR inhibitors. The effect of AKT-mTOR signaling on SCD1 expression was examined through pharmacological inhibition and gene silencing approaches. Additionally, the impact of SCD1 knockdown on cell proliferation and survival was analyzed.

Results: mTOR inhibitors significantly reduced HNSCC cell viability and downregulated SCD1 expression in a dose-dependent manner. Inhibition of AKT, a key upstream effector of mTOR, also suppressed SCD1 expression, suggesting that SCD1 is regulated through the PI3K-AKT-mTOR axis. Silencing SCD1 independently impaired cancer cell growth and enhanced the cytotoxic effects of mTOR inhibitors, indicating a synergistic anticancer effect.

Conclusion: SCD1 is a downstream target of the PI3K-AKT-mTOR pathway and contributes to HNSCC cell survival. Dual targeting of SCD1 and the mTOR signaling pathway represents a promising therapeutic strategy for HNSCC treatment. Further investigation is warranted to explore the clinical potential of SCD1 inhibitors in combination with mTOR-targeted therapies.

Keywords: PI3K‐AKT‐mTOR signaling; head and neck squamous cell carcinoma (HNSCC); lipid metabolism; stearoyl‐CoA desaturase 1 (SCD1); therapeutic target.

Figure 1

Stearoyl‐coenzyme A desaturase 1 (SCD1) expression in head and neck squamous cell carcinoma (HNSCC). SCD1 expression was significantly upregulated in tumor tissues of HNSCC (n = 9, P = .003). The y‐axis represents the fold change in SCD1 expression levels.

Figure 2

Inhibitory effects of (A) NVP‐BEZ235, (B) rapamycin, and (C) LY294002 on head and neck squamous cell carcinoma cell viability in a dose‐dependent manner, measured by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. *P < .05, **P < .01, and ***P < .001 compared to untreated control cells.

Figure 3

Stearoyl‐coenzyme A desaturase 1 (SCD1) expression following treatment with three mammalian target of rapamycin (mTOR) inhibitors. Treatment with (A) NVP‐BEZ235, (B) rapamycin, and (C) LY294002 for 24 hours exhibited varying inhibitory effects on SCD1 expression across four head and neck squamous cell carcinoma cell lines.

Figure 4

Regulation of stearoyl‐coenzyme A desaturase 1 (SCD1) by AKT signaling. (A) SC79 activates AKT, increasing SCD1 and p‐mammalian target of rapamycin (mTOR) in SCC‐4 and Detroit 562 cells. (B) AZD5363 inhibits AKT, reducing SCD1 and p‐mTOR in HNSCC cells.

Figure 5

Stearoyl‐coenzyme A desaturase 1 (SCD1) silencing inhibits head and neck squamous cell carcinoma (HNSCC) progression. (A) Reduced proliferation in FaDu and Detroit 562 by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. (B) Decreased migration and invasion in HNSCC cells. *P < .05 compared to control cells. siRNA, small interfering RNA.

Figure 6

Graphical summary of the mechanism of cancer apoptosis by inhibiting the phosphoinositide 3‐kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR)/stearoyl‐coenzyme A desaturase 1 (SCD1) axis.