Abstract:

Objective To investigate the role of Notch1 gene in xenografted human cutaneous squamous cell （SCL-1） carcinoma. Methods Fifteen nude mice were divided into three groups, including untreated group （inoculated with SCL-1 cells treated with phosphate buffered saline）, empty vector group （inoculated with SCL-1 cells transfected with empty vector） and Notch1 group （inoculated with SCL-1 cells transfected with Notch1 expression vector）. All the mice were inoculated with SCL-1 cells （1 × 108/ml） of 0.2 ml. Then, the growth of xenografted tumor was observed every other day. Fifteen days later, the mice were sacrificed, tumor tissue was dissected and subjected to terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling （TUNEL） assay for the detection of cell apoptosis, reverse-transcription （RT）-PCR and Western blot for the examination of mRNA and protein expressions of Notch1, bcl-2 and bax, respectively. Results The proliferation of xenografted tumor in Notch1 group was obviously inhibited compared with the untreated group. The weight of xenografted tumor in Notch1 group was significantly lower than that in the untreated group and empty vector group （0.574 ± 0.219 g vs. 2.642 ± 0.404 g and 2.606 ± 0.512 g, F = 26.642, P < 0.01）. TUNEL assay demonstrated that the number of apoptotic cells per 500 cells in tumor tissue specimens was （87 ± 9） in Notch1 group, evidently higher than that in the untreated group （8 ± 2） and empty vector group （10 ± 3） （F = 194.266, P < 0.05）. Further, RT-PCR and Western blot revealed that the mRNA and protein expressions of Notch1 and bax were significantly upregulated, but those of bcl-2 were markedly downregulated in the Notch1 group, with significant difference among the three groups （all P < 0.05）. Conclusions Notch1 gene can inhibit the growth of xenografted human cutaneous squamous cell （SCL-1） carcinoma and induce SCL-1 cell apoptosis likely by upregulating bax expression and downregulating bcl-2 expression.

Key words: cell apoptosis