Variant CD44 expression by human fibroblasts

Abstract

CD44 is a cell surface glycoprotein with roles in tumour invasion and metastasis. CD44 is variably spliced from ten variant exons and mis-splicing is a biomarker for detection of colon, urothelial and other carcinomas. Fibroblasts are normally considered to lack variant exons and thus should not generate false-positive signals. Transcription of variant exons by fibroblasts was investigated by exon-specific reverse transcription-polymerase chain reaction (RT-PCR) for variant exons v2-v10 using normal primary fibroblasts, immortalized and experimentally transformed fibroblasts. Flow cytometry, immunocytochemistry and Western blotting were used to determine expression. All types of fibroblasts, including normal primary culture fibroblasts, transcribed low levels of variant exon mRNA. Expression could not be detected by blotting or immunocytochemistry but flow cytometry revealed minor expression of some exons by all three types of cultured fibroblast. Fibroblasts do transcribe and express small amounts of variant exon CD44. This may need to be considered when using exon splicing as a biomarker for malignancy in clinical samples containing connective tissue.