UBL4A and hepatocellular carcinoma: The enriched HepG2 EVs were then subjected to triplex RT-dPCR for the absolute quantification of each of the 12 HCC EV-specific gene candidates, including ALB, APOH, ATAD2, FABP1, FGB, FGG, H2AX, PUF60, SORT1, TF, TUBG1, and UBL4A. As shown in Fig. 4B, robust linear correlations (R2 > 0.90) were observed between the levels of spiked HepG2 EVs and the detected mRNA copy numbers across all 12 HCC EV-specific gene candidates over the concentration range of 0 – 6 × 109 HepG2 EVs per μL, with R-squared values ranging from 0.991 to 0.999.