In this study, how is Beclin-1 expression quantified in tumor samples?

• A. By H-score, which combines staining intensity and percentage
• B. By measuring mRNA levels
• C. By counting positive cells only
• D. By assessing tumor size

Answer: (A)

Beclin-1 expression in tumor tissue is typically assessed by immunohistochemistry and quantified with an H-score, which blends how strongly the protein stains (intensity) with how many cells show staining (proportion). This yields a single semi-quantitative value that reflects both the presence and abundance of Beclin-1 within the tissue. The H-score is calculated by weighting the percentage of cells at each staining intensity (for example, 0, 1+, 2+, 3+) by that intensity value and summing across all levels, often resulting in a range from 0 to 300. This method captures nuances in both how many cells express Beclin-1 and how robust the expression is, which simple counts of positive cells would miss, and it ties directly to protein localization in the tissue.

Measuring mRNA levels would reflect transcription rather than protein expression and spatial distribution, which may not correspond to actual protein abundance in the tumor cells. Counting positive cells alone ignores how intense the staining is, and tumor size has no direct bearing on Beclin-1 expression.