The constitutive activation of the Notch pathway has been demonstrated in various types of malignancies. However, it remains unclear how the Notch pathway is involved in the pathogenesis of oral squamous cell carcinoma (OSCC). We investigated the expression of Notch pathway molecules in OSCC cell lines and biopsy specimens and examined the effect of Notch pathway inhibition. Reverse transcription-polymerase chain reaction revealed upregulation of Notch1, Notch2, Jagged1, HES1 and HEY1 in both OSCC cell lines and biopsy specimens. Immunohistochemical examination showed that the Notch intracellular domain accumulates in the nucleus of cells in OSCC cell lines and biopsy specimens. In addition, Jagged1 is expressed in the cytoplasm of cells in OSCC cell lines and biopsy specimens. Furthermore, Notch pathway inhibition using a γ-secretase inhibitor prevented the growth of OSCC in vitro. These findings suggest that inhibition of the Notch pathway suppresses OSCC growth and may be a useful approach for the treatment of patients with OSCC.

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