Notch signaling plays a key role in a wide variety of human tumors; it can be an oncogene or a tumor-suppressor gene depending on the tissue context. The functions of Notch1 in laryngeal squamous cell carcinoma (LSCC) are largely unknown. We investigated the role of Notch1 in LSCC cell growth, apoptosis and metastasis. We analyzed Notch1 expression in clinical LSCC samples using quantum dot immunohistochemistry (QD-IHC) and conventional IHC. Human laryngeal carcinoma HEp-2 cells were transfected with Notch1-specific short hairpin RNA (shRNA), and cell proliferation, apoptosis, and migration and invasion were evaluated using the cell counting assay, flow cytometry and wound healing and Transwell assays, respectively; western blotting was used to validate the expression of Notch1 target genes. Compared with normal tissues, Notch1 was upregulated in LSCC tissues; compared with LSCC tissues without metastasis, Notch1 upregulation was enhanced in LSCC tissues with metastasis (P<0.05). Transfection downregulated Notch1 mRNA and protein expression levels in the Notch1 shRNA group. There was a significantly greater decrease in cell proliferation in the Notch1 shRNA group than cell proliferation in the non-transfected (P<0.05) and negative shRNA groups (P<0.05). Furthermore, Notch1 knockdown induced apoptosis in the HEp-2 cells. Additionally, the number of migrated and invasive cells in the Notch1 shRNA group was decreased (P<0.05). Notch1 knockdown in the HEp-2 cells greatly inhibited phosphorylated extracellular signal-related kinase (p-ERK), phosphorylated protein kinase B (p-AKT), c-Myc, Bcl-2, p21, cyclin D1, cyclin-dependent kinase 4 (CDK4) and cyclin E expression levels and increased Bax expression. Altogether, our findings indicate that Notch1 expression is increased in human LSCC and correlates with tumorigenesis and metastasis, while in HEp-2 cells, Notch1 knockdown inhibited cell growth, induced apoptosis and inhibited migration and invasion by regulating Notch1 target genes, suggesting it may be a potential therapeutic target for treating LSCC.

Notch signaling is important during the development of a variety of human tumors. Depending on the context, Notch signaling can be either oncogenic or anti-proliferative, and therefore, its effects in cancer are unpredictable. The aim of the present study was to identify the importance of Notch 2 in the cell growth and metastasis of laryngeal squamous cell carcinoma (LSCC). The current study performed quantum dots-based immunofluorescence histochemistry to determine expression of Notch 2 in 72 LSCC samples without lymph node metastasis, 23 LSCC samples with lymph node metastasis and 31 samples from vocal cord polyps. It was observed that Notch 2 was upregulated in LSCC tissue compared with normal vocal cord polyps. This upregulation was further enhanced in LSCC tissues with lymph node metastasis compared with LSCC tissues without lymph node metastasis. Following knockdown of NOTCH2 expression in LSCC cells, the in vitro tumorigenicity of Hep-2 cells was inhibited, with growth, migration, invasion and proliferation reduced, and apoptosis induced. Additionally, following downregulation of Notch 2 protein expression, the protein expression levels of phosphor-mitogen-activated protein kinase 1 (p-ERK), v-myc avian myelocytomatosis viral oncogene homolog and B-cell CLL/lymphoma 2 (Bcl2) were also downregulated, whereas, Bcl2-associated X protein expression was upregulated. There were no changes detected in the protein expression levels of total-ERK, phospho-v-akt murine thymoma viral oncogene homolog 1 (p-Akt) and total-Akt. The results of the present study suggest that Notch 2 is important for the cell growth, anti-apoptosis and metastasis of LSCC. Therefore, Notch 2 inhibitors may have therapeutic potential for the treatment of patients with LSCC via the inhibition of cancer cell growth and metastasis.

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