Expression of ABC transporters is an unfavorable prognostic factor in laryngeal squamous cell carcinoma.

OBJECTIVES: Two prominent and well-characterized representatives of adenosine triphosphate-binding cassette (ABC) transporter - breast cancer resistance protein (BCRP or ABCG2) and P-glycoprotein (P-gp or ABCB1) - are known to be membrane transporters associated with multidrug resistance. The aim of this study was to explore the correlation between ABC transporter expression and the clinicopathologic characteristics, proliferative index, and apoptotic index and their prognostic value in laryngeal squamous cell carcinoma (LSCC).

METHODS: Paraffin sections of 98 human LSCC specimens were investigated with immunohistochemical techniques. The relationship between ABCG2 and ABCB1 expression and clinicopathologic parameters, proliferative activities, and apoptotic activities and their prognostic value in patients' overall survival rate were subsequently analyzed.

RESULTS: Immunohistochemical analysis revealed positive expression of ABCG2 and ABCB1 in 52.0% and 41.8% of patients, respectively. There was a positive correlation between ABCG2 expression and ABCB1 expression. The presence of these two proteins was significantly related to clinical stage, lymph node metastasis, and overall survival in LSCC. Interestingly, up-regulation of ABCG2 expression was found to be associated with increased proliferation, but that of ABCB1 was not. Up-regulation of both ABCG2 expression and ABCB1 expression was associated with decreased apoptosis.

CONCLUSIONS: The results of this study revealed that the presence of ABCG2 and/or ABCB1 is predictive for malignant progression and is an independent prognostic factor in LSCC. The mechanism of ABC transporters may contribute to chemotherapy resistance by promoting proliferation and/or suppressing apoptosis.