Syntenin-1 is a promoter and prognostic marker of head and neck squamous cell carcinoma invasion and metastasis

Abstract

Metastasis represents a key factor associated with poor prognosis of head and neck squamous cell carcinoma (HNSC). However, the underlying molecular mechanisms remain largely unknown. In this study, our liquid chromatography with tandem mass spectrometry analysis revealed a number of significantly differentially expressed membrane/membrane-associated proteins between high invasive UM1 and low invasive UM2 cells. One of the identified membrane proteins, Syntenin-1, was remarkably up-regulated in HNSC tissues and cell lines when compared to the controls, and also over-expressed in recurrent HNSC and high invasive UM1 cells. Syntenin-1 over-expression was found to be significantly associated with lymph node metastasis and disease recurrence. HNSC patients with higher syntenin-1 expression had significantly poorer long term overall survival and similar results were found in many other types of cancers based on analysis of The Cancer Genome Atlas data. Finally, knockdown of syntenin-1 inhibited the proliferation, migration and invasion of HNSC cells, and opposite findings were observed when syntenin-1 was over-expressed. Collectively, our studies indicate that syntenin-1 promotes invasion and progression of HNSC. It may serve as a valuable biomarker for lymph node metastasis or a potential target for therapeutic intervention in HNSC.

Keywords: head and neck squamous cell carcinoma; membrane proteins; metastasis; syntenin-1.

Figure 1. LC-MS/MS analysis and identification of membrane/membrane-associated proteins in UM1 and UM2 cells

(A) The commonly and differentially expressed proteins between UM1 and UM2 cells; (B) Subcellular localization of the identified membrane and membrane-associated proteins in UM1 and UM2 cells.

Figure 2. The expression level and clinical significance of SDCBP in HNSC

(A) SDCBP was significantly up-regulated in HNSC tissues compared to the controls (P < 0.0001); (B) The HNSC patients in the high SDCBP expression group suffered poorer long term overall survival than those in the low SDCBP expression group (P = 0.0028).

Figure 3. Higher SDCBP expression was associated with poorer overall survival in other types of cancers

The cancer patients with higher SDCBP expression suffered remarkably shorter overall survival in a number of other cancers including BRCA (P = 0.0083), GBM (P = 0.0214), KIRP (P = 0.0104), LGG (P < 0.0001), LUAD (P = 0.0085), LUSC (P = 0.0004), SARC (P = 0.0223), PAAD (P = 0.0130), THCA (P = 0.0021) and UVM (P = 0.0003).

Figure 4. Syntenin-1 was overexpressed in HNSC cell lines and tissues

(A–B) Syntenin-1 mRNA and protein levels were overexpressed significantly in both UM1 and UM2 cells compared to NHOKs (**P < 0.01). In addition, the expression level of syntenin-1 was significantly over-expressed in high invasive UM1 cells compared to low invasive UM2 cells (**P < 0.01). (C) The expression level of syntenin-1 was significantly overexpressed in HNSC tissues in comparison with the adjacent normal tissues (**P < 0.01).

Figure 5. IHC analysis of syntenin-1 in HNSC

Syntenin-1 was upregulated in HNSC while barely detected in normal tissues. The staining intensity of syntenin-1 was also higher in recurrent HNSC compared with non-recurrent HNSC.

Figure 6. Inhibition of syntenin-1 suppressed the proliferation, migration and invasion capacity of UM1 cells

(A) Syntenin-1 was significantly inhibited following sisyntenin-1 transfection. (B) The OD values were lower in syntenin-1 knockdown cells compared to the controls (**P < 0.01). (C) The number of colonies was significantly lower for syntenin-1 knockdown cells versus the controls. (D) The percentage of EdU-positive cells was lower for syntenin-1 knockdown cells (**P < 0.01). (E) The migration capability of syntenin-1 knockdown cells was significantly inhibited (**P < 0.01). (F) The number of cancer cells that invaded through the membrane was remarkably reduced following syntenin-1 knockdown (**P < 0.01).

Figure 7. Syntenin-1 overexpression promoted the proliferation, migration and invasion capacity of UM1 cells

(A) Syntenin-1 was significantly overexpressed following lenti-syntenin-1 infection. (B) The OD values were higher for syntenin-1 overexpressed cells when compared to the controls (*P < 0.05, **P < 0.01). (C) The number of colonies was significantly higher for syntenin-1 overexpressed cells versus the controls. (D) The percentage of EdU positive cells was higher for lenti-syntenin-1 treated cells (**P < 0.01). (E) The UM1 cells with syntenin-1 overexpression were more proficient than empty vector-transduced cells at closing an artificial wound (**P < 0.01). (F) The number of cancer cells that invaded through the membrane was remarkably increased following sisyntenin-1 up-regulation (**P < 0.01).