Prostate tumor overexpressed-1, in conjunction with human papillomavirus status, predicts outcome in early-stage human laryngeal squamous cell carcinoma

Abstract

In human cancer, molecular markers combined with clinical characteristics are used increasingly to predict prognosis. Prostate tumor overexpressed-1 (PTOV1), first identified in prostate cancer, is a key factor in tumor progression and correlates with unfavorable clinical outcomes. HPV infection status was tested by HPV E6-targeted multiplex real-time PCR and p16 immunohistochemistry (IHC). Real-time PCR and western blotting analyses were used to examine the mRNA and protein expression levels of PTOV1 in eight paired LSCC samples. IHC was performed to assess PTOV1 protein expression in 196 paraffin-embedded, archived LSCC samples. PTOV1 protein and mRNA expression was increased in LSCC tissues compared with adjacent non-cancerous tissue samples. High expression of PTOV1was significantly associated with advanced TNM stage by the χ2 test. Multivariate analysis revealed that PTOV1 and HPV status were independent prognostic indicators of overall survival (OS) and progression-free survival (PFS) (P = 0.001, P = 0.009 for OS, P = 0.005, P = 0.012 for PFS, respectively). Our study provides the first evidence that the combination of PTOV1 expression level and HPV status provides more prognostic information compared with HPV status alone with the significance still exists in the HPV negative subgroup.

Keywords: HPV; biomarker; laryngeal squamous cell carcinoma; prognosis; prostate tumor overexpressed-1.

Figure 1. Overexpression of PTOV1 mRNA and protein in human laryngeal squamous cell carcinoma (LSCC) tissues

A. PTOV1 mRNA expression in eight matched pairs of LSCC tissues (T) and adjacent non-cancerous tissues (ANT), as quantified by PCR and normalized to the expression of GAPDH. Error bars are the standard deviation of the mean (SD) for three experiments performed in parallel. B. Representative western blotting analyses of PTOV1 protein expression in eight pairs of matched LSCC tissues; α-tubulin was used as the loading control. C. Immunohistochemical analysis of PTOV1 protein expression in the eight pairs of matched LSCC tissues, *P < 0.05.

Figure 2. Expression of PTOV1 in different clinical stages of laryngeal squamous cell carcinoma (LSCC)

A. Representative images of immunohistochemical staining for PTOV1 in normal (control sections) LSCC tissues and different clinical stages of LSCC. B. Average fold-change in the mean optical density (MOD) for PTOV1 in different clinical stages of LSCC compared with normal laryngeal tissues. C. The statistical analyses of the average MOD of PTOV1 staining in the lymph node metastasis group and the lymph node metastasis-free group, *P < 0.05.

Figure 3. Same region of same tumor staining positive for PTOV1 (A, C; 200×, 400×) and p16 (B, D; 200×, 400×)

Figure 4. PTOV1 protein expression is associated with overall survival (OS) in the whole cohort

A. and the HPV-negative subgroup B. in LSCC. PTOV1+HPV status is associated with OS in the T2 subgroup, the N negative subgroup and the stage II subgroup C., D. and E., respectively). P-values were calculated using the log-rank test.

Figure 5. PTOV1 protein expression is associated with progression-free survival (PFS) in the whole cohort

A. and the HPV-negative subgroup B. in LSCC. PTOV1+HPV status is associated with PFS in the T2 subgroup, the N negative subgroup and the stage II subgroup C., D. and E., respectively). P-values were calculated using the log-rank test.