Cytokeratin 17 mRNA expression has potential for diagnostic marker of oral squamous cell carcinoma

Abstract

Purpose: Determination of marker for identification of oral squamous cell carcinoma (OSCC) is important for early diagnosis and individual therapy. Cytokeratins (CKs) like CK 19 and CK 20 are known to be useful diagnostic and prognostic markers for solid tumors. The aim of this study was to evaluate the relevance of further CKs for diagnosis of OSCC.

Materials: In 10 OSCC and 5 normal mucosal samples, the expression patterns of 31 CK genes were examined by cDNA microarray in order to identify CKs with most pronounced over-expression. The results were verified for CK 17, CK 19, and CK 20 in addition to 46 OSCC samples by relative quantification (RQ) using SYBR green real-time reverse transcriptase polymerase chain reaction (RT qPCR). A correlation of the CK expressions with the tumor classification was carried out.

Results: cDNA microarray analyses showed that out of all CKs, CK 17 was up-regulated strongest in OSCC compared to normal samples, and over-expression was most significantly associated with diagnosis (P = 0.002). Expression rates of CK 19 and CK 20 were not significantly different between OSCC samples and normal samples. In 56 samples analyzed by real-time RT qPCR, CK 17 was over-expressed in 53 (94.6%), CK 19 in 18 (32.1%), and CK 20 in 7 (12.5%). The over-expression of CK 17 was significantly associated with metastases of neck lymph nodes (P < 0.05). CK 19 was significantly over-expressed in T3 and T4 OSCC, in stage III and IV patients (P < 0.05), and in poorly differentiated OSCC (P < 0.03). The over-expression of CK 20 was significantly associated with metastases of neck lymph nodes (P < 0.03). Determined by RQ, the mean value of CK 17 over-expression was significantly higher than that of the other CKs (P < 0.01), and was significantly associated with T1 and T2 OSCC (P < 0.03) and with stage I and II patients (P < 0.01).

Conclusion: CK 19 might be linked to the clinical progression and differentiation of OSCC, and CK 20 could be associated with metastases of neck lymph nodes in OSCC. Due to the significant up-regulation and the strong over-expression, CK 17 might be the most suitable marker for diagnosis of OSCC out of the CK-family.

Fig. 1

Raw data of relative quantification (RQ) of CK mRNA from five patients with OSCC compared to normal oral mucosa (calibrator). Mean values of duplicate CK mRNA RQ are shown. Similar results were obtained from an additional 51 patients. All quantities were analyzed in duplicate. 1 Patient number is shown; 2 mRNA from squamous cell carcinoma cell line of the head and neck, SCC 15 was analyzed as a positive control

Fig. 2

Mean values of CK mRNA RQ in all patients with OSCC. *The difference of the mean value was significant between three CKs by the Kruskall–Wallis test (P < 0.01)

Fig. 3

Mean values of CK mRNA RQ in patients with OSCC compared to the tumor size. *The difference of the mean value was significant between three CKs by the Kruskall–Wallis test (P < 0.03). 1 The cases of patients with T1 and T2 OSCC are shown; 2 the cases of patients with T3 and T4 OSCC are shown

Fig. 4

Mean values of CK mRNA RQ in patients with OSCC compared to state of lymph node. *The difference of the mean value was significant between three CKs by the Kruskall–Wallis test (P < 0.0001). 1 The cases are shown of patients in which had metastases of neck lymph nodes; 2 the cases are shown of patients in which had no metastases of neck lymph nodes

Fig. 5

Mean values of CK mRNA RQ in patients with OSCC compared to the clinical stages. *The difference of the mean value was significant between three CKs by the Kruskall–Wallis test (P < 0.01). 1 The cases are shown of patients at stages I and II; 2 the cases are shown of patients at stages III and IV