Potential Clinical Value of 5-Hydroxytryptamine Receptor 3C as a Prognostic Biomarker for Lung Cancer

Ion channels and pumps not only regulate membrane potential, ion homeostasis, and electric signaling in excitable cells but also contribute to cell proliferation, migration, apoptosis, and differentiation. Channel proteins and ion pumps can form macromolecular complexes with signaling molecules, including growth factors and cell adhesion molecules. Serotonin (5-hydroxytryptamine (5-HT)) promotes the proliferation of various cancer cell types mediated through the activation of the 5-HT receptor (HTR). Only HTR3 is a ligand-gated ion channel. However, the role of the HTR3 family of HTRs in lung cancer has not been adequately evaluated. We evaluated the relationship between the HTR3 family of HTRs and lung cancer patients' survival using Kaplan–Meier analyses and examined the expression levels of target proteins using immunohistochemistry. In this study, we found that HTR3C was amplified with high frequency in lung cancer patients, and HTR3C protein expression levels were significantly associated with lymph node metastasis and distant metastasis in lung cancer tissues. Survival analysis using the log-rank test demonstrated a decrease in disease-free survival (DFS) and overall survival (OS) rates among the high-level HTR3C expression group compared with the low-level HTR3C expression group. We also evaluated the risk factors associated with lung cancer. The univariate and multivariate analyses of DFS and OS showed that HTR3C expression was a significant predictor of patient outcomes. Taken together, these data demonstrated that HTR3C expression levels were associated with poor DFS and OS in lung cancer patients, indicating that HTR3C can serve as a useful predictive biomarker for lung cancer.