Identification of a specific head and neck carcinoma binding peptide

Abstract

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Objectives: Although quality of life has been improved in head and neck (HN) tumor patients, a significant increase of live expectancy is still pending. Therefore, new targeted therapies which provide a specific accumulation of the drug in tumors are necessary. Via phage display a head and neck carcinoma binding peptide (HBP-1) was identified and its in vitro and in vivo features were investigated.

Methods: The method of phage display was applied for identification of specific binding peptides. One phage library comprises 109 different displayed peptides. After 5 in vitro selection rounds with HNO 210 tumor cells and previous negative selection with immortalized oral mucosa keratinocytes (HPV-16-GM) tumor binding phages were enriched. The peptides expressed on the surfaces of the isolated phages were identified by sequencing their DNA. Subsequently, one of these peptides was produced by Fmoc solid phase synthesis. Human HNO 97 cells and the peptide labeled with I-125 were used for in vitro binding studies, kinetics and determination of the IC50-value. Peptide stability was ascertained in human serum at 37°C. In vivo biodistribution of I-131 labeled peptide was determined using HNO 97 tumor bearing nude mice.

Results: A specific binding peptide was identified by applying phage display screening on HN tumor cells. This peptide, HBP-1, was found to be enriched in 13 out of 21 sequenced phages. Labeled with I-125, HBP-1 showed a binding of up to 14% of the applied dose per 1 million cells for 5 different HN tumor cell lines. The binding is considered to be specific as it is nearly competed with unlabeled HBP-1. In addition an average binding of 8% to MCF-7 mamma carcinoma cells was asserted. Further in vitro experiments with HBP-1 showed an IC50-value of 34 nM and a T1/2 = 55 min in human serum. In the organ distribution study of HN tumor bearing nude mice, an accumulation of the I-131 labeled peptide could be observed in the tumor up to 45 min after application.

Conclusions: The determined features of the HN tumor specific peptide HBP-1, represent a promising base for further research. Future investigations of HBP-1 binding to tumor tissue slices could reveal universal application for HN tumors and their metastasis in respect of tumor therapy and tumor imaging.