EGFR protein overexpression and gene copy number increases in oral tongue squamous cell carcinoma

https://doi.org/10.1016/j.ejca.2009.02.027Get rights and content

Abstract

New promising therapeutic agents targeting epidermal growth factor receptor (EGFR) have been developed although clinical information concerning EGFR status in oral tongue squamous cell carcinoma (OTSCC) is limited. We investigated EGFR protein expression and gene copy numbers in 78 pretreatment OTSCC paraffin samples. EGFR protein expression was found in all 78 tumours, of which 72% showed an intense staining. Fifty-four percent of the tumours had high (⩾four gene copies) EGFR gene copy numbers. EGFR gene copy number was significantly associated with EGFR protein expression (P = 0.002). Pretreatment EGFR staining intensity tended to be associated with non-pathological complete remission after preoperative radiotherapy for Stage II OTSCC. No correlation was found between EGFR status and survival. EGFR FISH results were significantly (P = 0.003) higher in more advanced tumours (Stages II, III and IV) than in the tumours in Stage I. Non-smokers exhibited a significantly higher EGFR gene copy number and protein overexpression in Stages I and II OTSCC than smokers (P = 0.001, P = 0.009). In conclusion, EGFR was found to be overexpressed in all OTSCCs making this cancer type interesting for exploring new therapeutic agents targeting the EGFR receptor.

Introduction

Oral tongue squamous cell carcinomas (OTSCCs) are associated with increasing incidence and poor prognosis.1 Deeper understanding of the molecular behaviour of the tumour may improve patient outcome. New promising therapeutic agents targeting epidermal growth factor receptor (EGFR) have been developed but clinical information concerning EGFR status in OTSCC is limited.

Epidermal growth factor receptor (EGFR) is a tyrosine kinase (TK) receptor known to be associated with radiation resistance and prognosis in head and neck squamous cell carcinoma (HNSCC).2, 3 Overexpression of EGFR is seen in approximately 90% of head and neck cancers making it an interesting target for therapy.4, 5 EGFR inhibitors, one being C225 (cetuximab), have shown promising radiosensitivity enhancement with amplification of radiation-induced apoptosis in tumour specimens.6 These studies are highly supportive that EGFR might provide a radiosensitising route for OTSCC patients.

This study aimed to investigate EGFR status using immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH) in patients with OTSCC. We investigated the association between EGFR IHC and FISH. In addition, we evaluated whether EGFR protein expression and/or high gene copy numbers, ⩾four gene copies, were associated with tumour progression, treatment prediction of preoperative radiotherapy and prognosis in OTSCC.

Section snippets

Materials and methods

We obtained 78 formalin-fixed, paraffin-embedded biopsy specimens with histopathologically confirmed OTSCC (UICC Stages I–IV) treated at the Department of Oto-Rhino-Laryngology, Head and Neck Surgery, Karolinska University Hospital (Stockholm, Sweden) from January 2000 to December 2004. Clinical information, including age, tumour grade, treatment modality, treatment response and follow-up, was retrieved from medical records (Table 1). Each patient had a minimum follow-up time of at least 36 

Results

EGFR protein expression determined by IHC showed that all tumours were positively stained for EGFR (Table 1). EGFR protein expression was categorised as intense in 72% and weak in 5% of patients, which is illustrated in Fig. 1A and B.

FISH analyses were performed on interphase cells from 65 OTSCC patients. Fifty-four percent (35 out of 65) of OTSCCs were FISH positive and had high gene copy numbers, i.e. ⩾four gene copy numbers (Table 1). In the positive group, there were 20 tumours with

Discussion

We investigated EGFR protein expression and gene copy number variation and its association with tumour progression, treatment prediction of preoperative radiotherapy and prognosis in OTSCC. We found that EGFR gene copy number significantly correlated with EGFR protein expression levels. Tumours that responded to radiotherapy showed less EGFR protein expression and the same trend was seen for EGFR gene copy number. Finally non-smokers had significantly higher EGFR protein expression and higher

Conflict of interest statement

None declared.

Acknowledgements

This work was supported by the Swedish Cancer Society (Cancerfonden), the Cancer Society of Stockholm (Cancerföreningen), Laryngfonden, Karolinska Institutet and the Intramural Research Programme of the NIH, National Cancer Institute. We gratefully thank Ann Olsson and Margaretha Waern for excellent technical assistance.

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