HE4: Revolutionary biomarker for early diagnosis and prognostic evaluation of ovarian cancer

Introduction
Ovarian cancer, the most lethal gynecological malignancy, presents significant challenges in early diagnosis. Approximately 75% of patients are diagnosed at advanced stages, with a 5-year survival rate below 30%. In this clinical dilemma, the discovery of human epididymis protein 4 (HE4) has brought new hope for early screening and precision treatment of ovarian cancer. This article systematically elaborates on the biological characteristics of HE4, advancements in detection technologies, and its clinical application value in the comprehensive management of ovarian cancer.

1. Molecular Characteristics and Expression Profile of HE4
The HE4 (WFDC2) gene is located on chromosome 20q12-13.1 and encodes a secreted glycoprotein containing two WAP-type four-disulfide core domains. Its unique cysteine residue arrangement (Cys1-X7-12-Cys2-X3-Cys3-X9-14-Cys4) confers a special spatial conformation, potentially involved in extracellular matrix remodeling and signal transduction regulation.

Expression profile analysis reveals:

• Normal tissues: Primarily expressed in reproductive tract epithelium and respiratory epithelium

• Malignant tumors: Overexpressed in 90% of serous ovarian cancers and 70% of endometrioid ovarian cancers

• Comparison with other biomarkers: Compared to the high false-positive rate of CA125 (35-50%) in benign conditions like endometriosis, HE4 shows a positivity rate of only 8-15% in benign gynecological diseases

2. Evolution and Standardization of Detection Technologies

1. Milestones in Antibody Development

   • The Hellstrom team constructed HE4-Fc fusion proteins via genetic engineering and screened highly affinity monoclonal antibodies (2H5 and 3D8)

   • Modern detection systems employ a double-antibody sandwich method with a sensitivity of 0.1 pmol/L

2. Comparison of Detection Methods

   Methodology	Sensitivity	Specificity	Linear Range
   ELISA	92%	86%	15-900 pM
   ECLIA	95%	91%	20-1500 pM
   CMIA	94%	89%	10-1200 pM

3. Evidence-Based Medical Data on Diagnostic Efficacy

1. Comparison of Single Biomarkers

   • Moore's study (n=233) showed: At 95% specificity

     • HE4 sensitivity: 72.9% (95%CI 68.3-77.1)

     • CA125 sensitivity: 43.3% (95%CI 38.5-48.1)

   • Greater advantages in early-stage cases (FIGO I):

     • HE4 detection rate: 82.7% vs CA125: 45.9%

2. Combined Detection Strategies

   • Optimal combination: HE4 + CA125

     • Sensitivity increased to 92.9%

     • Negative predictive value reached 96.3%

   • Clinical value:

     • Elevated HE4 alone: Suggests high-grade serous carcinoma (OR=4.2)

     • Elevated CA125 alone: Commonly seen in mucinous tumors (OR=3.8)

4. Optimization and Application of ROMA Index

1. Algorithm Evolution

   • Original model (2008):

     • Premenopausal: PI=-12+2.38×LN(HE4)+0.0626×LN(CA125)

     • Postmenopausal: PI=-8.09+1.04×LN(HE4)+0.732×LN(CA125)

   • 2020 improved version:
     Incorporated BMI correction factor, reducing false positives in premenopausal group by 12%

2. Clinical Application Recommendations

   • Postmenopausal women: ROMA threshold 27.7% (sensitivity 89%, specificity 81%)

   • Premenopausal women: Recommend combining ultrasound results (perform TVS when ROMA>11.4%)

5. Prognostic Assessment and Treatment Monitoring

1. Survival Prediction

   • Patients with preoperative HE4>140 pM:

     • 40% shorter PFS (HR=1.89, 95%CI 1.45-2.46)

     • 35% lower OS (HR=2.12, 95%CI 1.67-2.69)

2. Recurrence Monitoring

   • Havrilesky's study showed:

     • HE4 sensitivity for predicting recurrence reached 96%

     • Detected recurrence 3-5 months earlier than CA125 (median time)

3. Treatment Response Evaluation

   • Chemosensitive group: HE4 half-life 7.2 days

   • Resistant group: Persistently high or slowly declining HE4 levels (HR=3.21)

6. Challenges and Future Directions

1. Current Issues

   • Standardization of cutoff values: Need to establish region-specific reference ranges

   • Histological subtype differences: Detection rate for clear cell carcinoma only 65%

2. Future Directions

   • Multi-omics integration: Combine HE4 glycosylation profiling with mutation load analysis

   • Liquid biopsy: Development of exosomal HE4 detection technologies

   • Therapeutic targets: Research on anti-HE4 antibody-drug conjugates (ADCs)

Conclusion
As a crucial biomarker in ovarian cancer diagnosis and treatment, HE4's value has expanded from auxiliary diagnosis to comprehensive management, including prognostic assessment and efficacy monitoring. With advancements in detection technologies and deeper clinical applications, HE4 will undoubtedly contribute more to improving ovarian cancer patient outcomes. We recommend adopting an HE4 + CA125 combined detection strategy in clinical practice and interpreting results based on individual patient characteristics.