Promoter hypermethylation of CD133/PROM1 is an independent poor prognosis factor for head and neck squamous cell carcinoma

Abstract

PROM1 has played a pivotal role in the identification and isolation of tumor stem cells. This study aimed to assess the association between PROM1 promoter methylation and head and neck squamous cell carcinoma (HNSCC), and its diagnostic and prognostic value.Bioinformatic analysis was performed using data from the Cancer Genome Atlas-HNSC and Gene Expression Omnibus datasets.The results showed that PROM1 promoter was hypermethylated in HNSCCs compared with normal head and neck tissues (P = 4.58E-37). The area under the receiver-operating characteristic curve based on methylated PROM1 data was 0.799. In addition, PROM1 hypermethylation independently predicted poor overall survival (hazard ratio [HR]: 1.459, 95% confidence interval [CI]: 1.071-1.987, P = .016) and recurrence-free survival (HR: 1.729, 95% CI: 1.088-2.749, P = .021) in HNSCC patients. Moreover, PROM1 methylation was weakly negatively correlated with its mRNA expression (Pearson r = -0.148, P < .001).In summary, our study reveals that methylated PROM1 might serve as a valuable diagnostic biomarker and predictor of poor survival for HNSCC patients. PROM1 hypermethylation might partially contribute to its downregulation in HNSCC.

Figure 1

Genomic position of 3 available CpG probes (cg10630155, cg04203238, and cg26260038 in the Illumina Human Methylation 450K) in the PROM1 promoter is shown in the UCSC genome browser (human 2009 assembly; GRCh37/hg19).

Figure 2

HNSCC tissues have significantly elevated PROM1 promoter methylation levels compared with nontumor tissues. HNSCC = head and neck squamous cell carcinoma, N = sample number.

Figure 3

ROC curves to assess the diagnostic value of PROM1 promoter methylation in head and neck squamous cell carcinoma patients. The AUC was 0.799. The arrow indicates the cutoff point. ROC = receiver-operating characteristic, AUC = area under the curve.

Figure 4

Association between PROM1 promoter methylation and head and neck squamous cell carcinoma (HNSCC) prognosis. (A) PROM1 promoter hypermethylation is associated with poor overall survival in HNSCC patients. (B) PROM1 promoter hypermethylation is associated with poor recurrence-free survival in HNSCC patients.

Figure 5

PROM1 expression levels are significantly reduced in HNSCC tissues compared with normal tissues.

Figure 6

The correlation between PROM1 expression and its promoter methylation in HNSCC tissues and cell lines. (A) PROM1 expression was negatively correlated with its promoter methylation in HNSCC. (B) PROM1 expression increased in HNSCC cell lines after 5’-aza-2’-deoxycytidine treatment (5-AZA) treatment. ∗: fold change = with 5-AZA treatment/without 5-AZA treatment. HNSCC = head and neck squamous cell carcinoma, N = sample number.