Purpose: We reported that the expression of integrin-linked kinase (ILK) is up-regulated in ovarian carcinomas and that ovarian cancer cells have high expression of ILK. In this study, we have examined the expression of cell-free 59 kDa immunoreactive (ir)ILK in the serum and peritoneal fluid (PTF) of patients with ovarian cancer and evaluated its potential as a serum biomarker for early-stage screening and for monitoring clinical status of patients after chemotherapy treatment.
Experimental design: Thirty-six serum specimens, including normal (n = 6), benign (n = 6), borderline (n = 4), grade 1 (n = 5), grade 2 (n = 5), and grade 3 (n = 10), were evaluated for the expression of irILK by Western blotting. The expression of irILK was evaluated in PTF (n = 10) and peritoneal washings from women with benign ovarian cysts (n = 4). In addition, tissue-conditioned medium obtained from the cultures of primary ovarian tumors (n = 9) was examined for the presence of irILK. Finally, the potential of serum irILK as a biomarker for ovarian cancer screening was evaluated by comparison with cancer antigen 125 (CA 125) concentrations in cancer patients before and after chemotherapy.
Results: irILK expression was present in normal serum and in serum of patients with benign ovarian tumors. irILK expression was 6-9-fold higher in the serum of patients with grade 1, grade 2, and grade 3 ovarian cancer than in the serum of healthy volunteers and patients with benign ovarian tumors (P < 0.01). Enhanced expression of irILK in the serum of ovarian cancer patients correlated with the concentration of CA 125. High expression of irILK was present in all 10 PTF tested. Tissue-conditioned medium prepared from malignant ovarian tumors had 4-fold more irILK expression than conditioned medium obtained from borderline and benign tumors (P < 0.01). irILK expression in serum of cancer patients was reduced to basal normal levels after six cycles of Taxol/carboplatin and was consistent with the change of CA 125 levels before and after chemotherapy.
Conclusions: These data suggest that irILK is an ovarian tumor-associated antigen and implicates its potential not only as a biomarker for early-stage screening but also as a marker for monitoring the clinical condition of patients after treatment.