Axl Expression Stratifies Patients with Poor Prognosis after Hepatectomy for Hepatocellular Carcinoma

Background
Axl is a receptor tyrosine kinase which plays an important role in multiple human malignancies.
Design
The Axl expression was examined in several hepatocellular carcinoma(HCC) cell lines, paired tumor and nontumorous samples. Then, we examined cell growth curve, cell apoptosis and cell migration in SMMC-7721 cells over-expressed with Axl or siRNA against Axl, respectively. Finally, the prognostic value of Axl was investigated in a prospective cohort of 246 consecutive HCC patients undergoing curative hepatoectomy.
Results
We found Axl was positive in 22% of examined tumor tissues and all four cell lines. Over-expressing Axl in SMMC-7721 cells accelerated cell growth, cell migration and inhibited cell apoptosis, while knock-down of Axl exerted opposite effect. Axl expression was closely associated with serum AFP, multiple tumors, absence of encapsulation, microvascular invasion, and advanced BCLC or TNM stage. Patients with positive Axl staining had a higher 5-year recurrence rate (92% vs. 71%, P<0.001) and a lower 5-year survival rate (9% vs. 48%, P<0.001) than those with negative staining. The multivariate analyses showed that Axl expression was an independent factor for both tumor recurrence (HR: 1.725; 95% CI: 1.219–2.441) and survival (1.847; 1.291–2.642).
Conclusion
Axl expression suggests more aggressive tumor invasiveness and predicts worse prognosis for HCC patients undergoing resection.