Background: CA125 is a prevalently used serum biomarker for detecting ovarian cancer over the last three decades. However, it has a significant deficiency in screening for early-stage cancer. With the purpose of exploring an effective approach to improve its performance in early diagnosis, we investigated the postprandial fluctuation pattern of cancer-derived CA125 and the underlying mechanism.
Methods: In two medical centers, 551 patients sonographically diagnosed with ovarian (adnexal) cysts (< 5 cm in diameter) were enrolled and divided into five disease groups (pelvic inflammatory cysts, retention cysts, endometrioma, benign/borderline cystadenoma and malignant cysts). The subtle differences in 1-h postprandial serum CA125 increases were compared between disease groups. A support vector machine (SVM)-based algorithm was used for refining the performance of CA125 postprandial increment. Ovarian cancer xenograft animal and cancer cell models were used to recapitulate the clinical findings and reveal the molecular basis of postprandial blood glucose and insulin in invoking the synthesis/secretion/re-absorption of CA125.
Results: Patients with ovarian cancer presented the highest postprandial increment 13.3 ± 0.7% (mean ± standard deviation) among the five disease groups. Using a CA125 increment ≥ 10% criterion, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) reached 83.3, 96.3, 61.1 and 98.8%, respectively, for early-stage ovarian cancer. This performance was further improved by the SVM-based CA125-increment algorithm, which exhibited 91.7% sensitivity, 99.2% specificity, 89.2% PPV and 99.4% NPV. Both modalities manifested diagnostic advantages over the traditional CA125 test (75.0% sensitivity, 25.4% specificity, 6.6% PPV and 93.6% NPV at the cut-off of 35 U/mL). Regarding the molecular basis, the postprandial blood glucose and insulin-invoked overexpression of Mucin 16 (encoding CA125) were demonstrated in animal and cancer cell models, which were mediated by the PI3K-Akt pathway. Nevertheless, a Mesothelin-based CA125 re-absorption behavior was noted in the treated cancer cells, which contributed to the over-drop following the postprandial peak of serum CA125.
Conclusions: Cancer-derived serum CA125 possesses a unique and distinctive postprandial pattern, that distinguishes it from the common CA125 elevation in a benign disease condition. The dynamic measurement/assessment strategy can achieve a discriminatory power superior to that of a static test.
Keywords: Akt; CA125; Fasting; Glucose; Increment; Insulin; Mesothelin; Ovarian cancer; PI3K; Postprandial.