Abstract: Objective To investigate the expression characteristics of G protein-coupled receptor family C, member 5, group A (GPRC5A) in laryngeal carcinoma tissues, and to explore its role and mechanism in the development of laryngeal carcinoma. 
Methods The expression of GPRC5A in laryngeal carcinoma and para-carcinoma tissues of 32 patients with laryngeal squamous cell carcinoma confirmed in the Second Hospital of Hebei Medical University by pathological examination was detected by immunohistochemistry, and the correlation between its expression characteristics and clinical data was analyzed. Quantitative polymerase chain reaction (qPCR) was used to detect the expression of laryngeal carcinoma tissues and para-carcinoma tissues for validation at the tissue level, and to detect human bronchial epithelial cell BEAS-2B, laryngeal carcinoma cellline TU686 and hypopharyngeal cancer cell Fadu for validation at the cellular level. GPRC5A overexpression plasmid p-GPRC5A was constructed and transfected into TU686 cells. The effects of GPRC5A overexpression on the proliferation, invasion and migration of TU686 cells were detected by Cell counting kit 8 (CCK8)and Transwell methods. Western blot was applied to detect the effect of GPRC5A gene overexpression on the expression of apoptosis-related proteins in cells, and validate the effect of GPRC5A gene overexpression on epidermal growth factor receptor/signal transducer and activator of transcription 3 (EGFR/STAT3) pathway. 

Results Immunohistochemical results showed that the positive expression rate of GPRC5A in laryngeal carcinoma tissues was significantly lower than that in para-carcinoma tissues (χ2=14.190, P＜0.001). The differences in the expression of GPRC5A in laryngeal carcinoma was not significant with respect to different tumor stage, lymph node metastasis and differentiation degree (P＞0.05). The expression of GPRC5A mRNA in laryngeal carcinoma group was significantly lower than that in para-carcinoma group (t=3.175, P=0.003). The expression of GPRC5A in TU686 cells and Fadu cells was (0.73±0.08) and (0.78±0.04) times that of BEAS-2B respectively, with a significant difference (F=9.060, P=0.015). The CCK8 results indicated that after 48 h, the OD of the p-GPRC5A group was (0.76±0.03), which was significantly lower than that of the NC group (1.20±0.01) and the control group (1.30±0.08) (F=69.970, P＜0.001). Transwell experiment showed that the number of cells migrated in p-GPRC5A group was (138.70±10.97), which was significantly lower than that in control group (251.3±16.9) and NC group (247.7±17.5) (F=5 731.100, P＜0.001). The number of cells invaded in p-GPRC5A group was (113.00±10.21), which was significantly lower than that in control group (193.30±10.02) and NC group (190.00±7.90) (F=8 894.100, P＜0.001). Western blot results showed that the protein expression of Caspase 3 in p-GPRC5A group was significantly higher than that in control group (F=78.880， P＜0.001), and the expression of Bcl-2 protein in p-GPRC5A group was significantly decreased (F=125.820， P＜0.001). The expression of EGFR and p-STAT3 in p-GPRC5A group was significantly lower (F=25.573, P=0.001; F=60.614, P＜0.001). 
Conclusion GPRC5A has a low expression level in laryngeal carcinoma tissues and cell lines. Overexpression of GPRC5A can inhibit the proliferation, migration and invasion of laryngeal carcinoma cells, promote cell apoptosis, and inhibit the activation of EGFR/STAT3 pathway. 

Key words: laryngeal neoplasms, G protein-coupled receptor family C, member 5, group A, tumor progression