Objectives Ovarian cancer (OC) is the eighth most commonly occurring cancer worldwide. One of the most effective ways to improve patient survival would be an earlier diagnosis when survival rates are highest. However, diagnosis tends to be in the later stages of disease when patients present with pelvic or abdominal pain, urinary frequency or urgency, increased abdominal size or bloating. A diagnosis of OC is usually confirmed by a pelvic examination, transvaginal ultrasonography and detection of carbohydrate antigen 125 (CA125). However, the value of CA125 in early stage disease is limited due to a lack of sensitivity.

Methods Using immunohistochemistry we examined the expression of a panel of tumour antigens including ovarian cancer protein (OCP), as well as the standard biomarkers for OC, CA125, HE4 and WT1, in paraffin-embedded OC microarrays containing 208 samples. Scoring was performed in a single blinded fashion.

Results We found OC to be expressed at an intensity and frequency that exceeded that of CA125, HE4, WT1 or PASD1 in stage I and II OC. To confirm this expression we used two additional commercially-available antibodies that recognised OCP and demonstrated that this expression was reproducible and restricted to OC with little or no expression in adjacent, healthy ovarian or endometrial tissues, or indeed disease or inflamed endometrial tissue.

Conclusions We have identified a cancer-testis antigen that is more frequently expressed in presentation OC Stage I and II OC than CA125, HE4 and WT1. We are now examining the impact of siRNA treatment targetting OCP on OC cell survival in vitro.