A transmembrane glycoprotein labeled neuropilin-1 may be a diagnostic biomarker for hepatocellular carcinoma.
In a series of experiments using HCC tissues and cell lines, as well as serum samples from patients with other malignancies or hepatitis, Jiafei Lin, MD, from Shanghai Jiaotong University, Shanghai, China, and colleagues found that neuropilin-1 (NRP1) was up-regulated in hepatocellular carcinoma (HCC) and promotes tumor growth.
“Notably, the concentrations of serum NRP1 in the HCC patients were much higher than those of hepatitis B, hepatitis C, cirrhosis, breast cancer, colon cancer, gastric cancer, and lung cancer patients,” they wrote in the journal.
They also found that NRP1 has a high degree of sensitivity and specificity for HCC, and suggested that NRP1 could replace alpha fetoprotein (AFP) for early clinical diagnosis of HCC.
They first showed that NRP1 was directly regulated by TEAD, a family of transcription factors essential for developmental processes. The experiments in HCC cell lines showed that messenger RNA levels of NRP1 were increased when TEAD was overexpressed, and decreased when TEAD was knocked down. The experiments also suggested that TEAD binds directly to the promoter of NRP1 to stimulate its transcription in HCC cells.
The investigators then sought to demonstrate that NRP1 promotes tumor development and growth in HCC by testing expression of the protein in both normal liver and HCC tissue samples.
“NRP1 was found highly up-regulated in HCC tissues compared to normal tissues. Moreover, NRP1 was recruited to the membrane in HCC tissues, whereas this protein was not detected in normal tissues,” they wrote.
Furthermore, when they zeroed in on NRP1 using two different short hairpin RNAs to silence its expression, they found that knocking down NRP1 suppressed the viability of tumor cells and inhibited colony formation while also ramping up programmed cell death. Taken together, the data indicate that NRP1 is highly expressed in HCC and promotes tumorigenesis.
They then showed that NRP1 serum concentrations were significantly higher in samples from patients with HCC than in those from healthy individuals or patients with hepatitis B, hepatitis C, cirrhosis, breast cancer, colon cancer, gastric cancer, or lung cancer. In addition, higher NRP1 concentrations were significantly associated with higher HCC tumor stages.
The investigators then looked at the relationship between serum NRP1 and standard liver function markers in HCC, and found that NRP1 serum levels significantly correlated with gamma-glutamyltransferase, albumin, bile acid, ALT, AST, AFP, and prealbumin levels, but not total bilirubin or total protein levels.
Finally, they demonstrated that serum NRP1 is a better diagnostic marker than AFP, with an area under the receiver operating characteristic curve of 0.971, compared with 0.862 for AFP. At an NRP1 cutoff of 68 pg/mL, NRP1 had a sensitivity of 93.7%, and a specificity of 98.7%. Combining NRP1 with AFP only slightly improved the diagnostic accuracy.
“These results indicate that the single use of NRP1 is a promising choice for the diagnosis of HCC,” the investigators wrote.
They noted that the most of the study subjects were of Han Chinese origin, and that the results need to be validated in people of other ethnicities.
The study was supported by the National Natural Science Foundation of China. Potential conflicts of interest were not reported.
SOURCE: Lin J et al. Clin Chim Acta. 2018;485:158-65.