Michael G. Goggins

Personalizing CA125 Levels Using Tumor Marker Variants: A Case–Control Analysis of Diagnostic Performance for Pancreatic Cancer

Abstract Background: Cancer antigen 125 (CA125) is widely recognized as a useful biomarker for the surveillance of patients with ovarian and other cancers. Prior genome-wide association studies have identified variants that influence CA125 levels. We evaluated the utility of stratifying CA125 levels by such variants and evaluated diagnostic performance in control subjects and patients with pancreatic ductal adenocarcinoma (PDAC). Methods: We measured CA125 levels in 807 control subjects and 450 patients with PDAC and genotyped 10 variants involving four genes (GAL3ST2, MSLN, D2HGDH, and MUC16). We compared CA125 levels in controls by variant and generated variant-defined CA125 cutoffs and then classified cases and controls into functional groups based on their variant profile. We used this variant classification to evaluate the diagnostic performance of CA125 in patients with PDAC. Results: Six variants associated with CA125 levels were used to group controls into one of four groups. Mean CA125 levels in the highest variant group were approximately fourfold higher than in the lowest group. African Americans were more likely to have a variant group associated with low CA125 levels. After setting diagnostic cutoffs by variant group, the diagnostic sensitivity of CA125 for PDAC was 20.2% at 98% specificity (areas under the ROC curve, 0.702), not significantly different from a uniform CA125 diagnostic cutoff (areas under the ROC curve, 0.700). Conclusions: Gene variants can be used to generate personalized CA125 reference ranges. This approach did not significantly improve CA125’s diagnostic performance for pancreatic cancer, but it merits evaluation in other diagnostic settings, such as detecting ovarian cancer. Impact: Gene variants can be used to personalize CA125 levels.

Ultrasensitive Detection of Circulating LINE-1 ORF1p as a Specific Multicancer Biomarker

Abstract Improved biomarkers are needed for early cancer detection, risk stratification, treatment selection, and monitoring treatment response. Although proteins can be useful blood-based biomarkers, many have limited sensitivity or specificity for these applications. Long INterspersed Element-1 (LINE-1) open reading frame 1 protein (ORF1p) is a transposable element protein overexpressed in carcinomas and high-risk precursors during carcinogenesis with negligible expression in normal tissues, suggesting ORF1p could be a highly specific cancer biomarker. To explore ORF1p as a blood-based biomarker, we engineered ultrasensitive digital immunoassays that detect mid-attomolar (10−17 mol/L) ORF1p concentrations in plasma across multiple cancers with high specificity. Plasma ORF1p shows promise for early detection of ovarian cancer, improves diagnostic performance in a multianalyte panel, provides early therapeutic response monitoring in gastroesophageal cancers, and is prognostic for overall survival in gastroesophageal and colorectal cancers. Together, these observations nominate ORF1p as a multicancer biomarker with potential utility for disease detection and monitoring. Significance: The LINE-1 ORF1p transposon protein is pervasively expressed in many cancers and is a highly specific biomarker of multiple common, lethal carcinomas and their high-risk precursors in tissue and blood. Ultrasensitive ORF1p assays from as little as 25 μL plasma are novel, rapid, cost-effective tools in cancer detection and monitoring. See related commentary by Doucet and Cristofari, p. 2502. This article is featured in Selected Articles from This Issue, p. 2489