Expression of the extracellular matrix protein tenascin in malignant and benign ovarian tumours

The extracellular matrix protein tenascin (TN) is overexpressed in a number of solid tumours. This, however, is the first study to examine TN expression in ovarian tumours. TN protein was examined in frozen sections of 50 human ovarian tumours by immunohistochemistry. Malignant and borderline tumours showed a significantly greater incidence and intensity of stromal staining than benign tumours (P < 0.0001 and P = 0.038 respectively). Seven omental metastases were also examined and showed a strikingly similar protein distribution to their primary tumour counterparts. The expression pattern of different RNA isoforms, created by alternative splicing of the primary transcript, was identified using reverse transcription-polymerase chain reactions (RT-PCR). The smallest TN RNA splice variant (284 bp) was found in all tumours examined, while the appearance of larger molecular weight transcripts (similar to 490 and 556 bp), as major forms, was predominantly limited to malignant tumours, with 9/12 malignant tumours showing this pattern compared with 1/6 benign tumours. These data suggest that malignant ovarian tumours have increased expression of TN compared with benign tumours and this may be associated with induction of specific isoforms.