ALK gene copy number gain and its clinical significance in hepatocellular carcinoma

To examine the status and clinical significance of anaplastic lymphoma kinase (ALK) gene alterations in hepatocellular carcinoma (HCC) patients.

A total of 213 cases of HCC were examined by fluorescent in situ hybridization using dual color break-apart ALK probes for the detection of chromosomal translocation and gene copy number gain. HCC tissue microarrays were constructed, and the correlation between the ALK status and clinicopathological variables was assessed by χ(2) test or Fisher's exact test. Survival analysis was estimated using the Kaplan-Meier approach with a Log-rank test. Univariate and multivariate analyses of clinical variables were performed using the Cox proportional hazards regression model.

ALK gene translocation was not observed in any of the HCC cases included in the present study. ALK gene copy number gain (ALK/CNG) (≥ 4 copies/cell) was detected in 28 (13.15%) of the 213 HCC patients. The 3-year progression-free-survival (PFS) rate for ALK/CNG-positive HCC patients was significantly poorer than ALK/CNG-negative patients (27.3% vs 42.5%, P = 0.048), especially for patients with advanced stage III/IV (0% vs 33.5%, P = 0.007), and patients with grade III disease (24.8% vs 49.9%, P = 0.023). ALK/CNG-positive HCC patients had a significantly poorer prognosis than ALK/CNG-negative patients in the subgroup that was negative for serum hepatitis B virus DNA, with significantly different 3-year overall survival rates (18.2% vs 63.6%, P = 0.021) and PFS rates (18.2% vs 46.9%, P = 0.019). Multivariate Cox proportional hazards regression analysis suggested that ALK/CNG prevalence can predict death in HCC (HR = 1.596; 95%CI: 1.008-2.526, P = 0.046).

ALK/CNG, but not translocation of ALK, is present in HCC and may be an unfavorable prognostic predictor.