Activation of Signal Transducers and Activators of Transcription 3 and Overexpression of its Target Gene CyclinD1 in Laryngeal Carcinomas

Objectives/Hypothesis: Constitutive activation of signal transducers and activators of transcription (STAT) 3 has been observed in many solid tumors including head and neck squamous cell carcinoma. Expression and activation of STAT3 in laryngeal carcinoma have not been fully understood. The study aims to investigate the expression and activation of STAT3 in laryngeal carcinoma, the relationship between activated STAT3 and its downstream target gene CyclinD1 and the related clinicopathological factors of activated STAT3. Study Design: Prospective. Methods: Sixty-four samples of laryngeal squamous cell carcinoma and 12 samples of control mucosa obtained from total laryngectomy cases were analyzed using Western blot analysis and reverse transcriptase-polymerase chain reaction. Statistical analysis was performed using SPSS. Results: The overexpression of both STAT3 and CyclinD1 mRNA was observed in all samples of laryngeal squamous cell carcinoma. The mRNA levels of STAT3 and CyclinD1 in carcinoma tissue were 2.1- and 2.3-fold higher than those in control mucosa, respectively; the differences were statistically significant (P < .01). The overexpression of STAT3, p-STAT3, and CyclinD1 protein was also observed in all tumor samples. The protein levels of STAT3, p-STAT3, and CyclinD1 in carcinoma tissue were 1.6-, 4.5-, and 2.0-fold higher than those in control mucosa respectively; the differences were statistically significant (P < .01). There was a positive correlation between p-STAT3 protein and CyclinD1 mRNA (Pearson correlation coefficient = 0.827, P < .01). There were significant correlations between the overexpression of p-STAT3 protein and clinical T stage (P <.01), and tumor size (P < .05). The p-STAT3 protein level of patients in T1, T2 was higher than that of patients in T3, T4. The p-STAT3 protein level of patients with tumor size within 20 mm was higher than that of patients with tumor size more than 20 mm. Conclusions: High expression and activation of STAT3 exist in laryngeal carcinomas. Activated STAT3 may take effect on promoting transcription of its downstream target gene CyclinD1. The role of activation of STAT3 in laryngeal carcinogenesis needs further research.