Beta-catenin mutations are associated with a subset of low-stage hepatocellular carcinoma negative for hepatitis B virus and with favorable prognosis

Abstract

To better understand the role of beta-catenin mutation in hepatocellular carcinoma (HCC), we correlated the gene mutation with hepatitis virus B (HBV) and hepatitis virus C (HCV) status and the clinicopathological features in 366 patients with resected primary unifocal HCC. beta-Catenin mutations were also analyzed in 55 patients with multifocal HCC (68 tumors). Of the whole series, 57 (13.1%) of 434 tumors examined had beta-catenin mutations, 34 occurred at the serine/threonine residues of the GSK-3beta region of beta-catenin. Outside the GSK-3beta phosphorylation site, codons 32 and 34 were two mutational hot spots (17 tumors). The non-HBV-related HCC that was predominantly HCV related had a higher frequency of mutation (P: < 0.00001) and more frequent mutations at codon 45 than HBV-related HCC. HBV-related HCC had a younger mean age (P: < 0.00001), and higher male-to-female ratio (P: < 0.003) and positive familial history of HCC (P: < 0.014). Among 366 unifocal HCCs selected for clinicopathological analysis, beta-catenin mutations were associated with grade I (P: = 0.005) and stage I and II HCC (P: < 0.0001), and a better 5-year survival rate (P: = 0. 00003). These findings suggest mechanisms for beta-catenin mutations differ between HBV-related and non-HBV-related HCCs, and that beta-catenin mutation is a favorable prognostic factor related to low stage. beta-Catenin mutation was associated with nuclear expression of the protein (P: < 0.00001), but we failed to detect point or large fragment deletion mutation in 39 HCCs with nuclear beta-catenin expression, presumably wild-type protein. HCCs expressing mutant nuclear beta-catenin had a better 5-year survival rate (P: < 0.007), suggesting that mutant and wild-type nuclear beta-catenin proteins are not functionally equivalent and deserve more studies for further clarification.

Figure 1.

Mutations of the β-catenin gene in hepatocellular carcinoma. Representative mutations leading to amino acid substitutions are shown. A–F: Point mutations at codons 32, 34, 41, and 45: Asp → Tyr (A), Asp → Gly (B), Gly → Val (C), Gly → Glu (D), Thr → Ala (E), and Ser⁴⁵ → Pro (F). A small deletion of codons 45–48 (G) and a large segment deletion of codons 10–141 (H) are indicated.

Figure 2.

Illustration of the location of 57 mutations of the β-catenin gene in hepatitis B virus-positive HBV(+) and hepatitis B virus-negative HBV(−), primary unifocal and multifocal hepatocellular carcinoma. Of the HBV(−) HCC, 21 (87.5%) of 24 tumors were taken from patients positive for anti-HCV. The amino acid substitutions of 53 point mutations in exon 3 are indicted at the top, whereas four deletion mutations, designated as Δ, are indicated at the bottom. Bold type indicates potential phosphorylation sites on threonine and serine residues. *, designates HBV(+) patients who were also positive for anti-HCV in sera. Single-letter abbreviations for the amino acid residues are: A, Ala; C, Cys; D, Asp; E, Glu; F, Phe; G, Gly; H, His; I, Ile; K, Lys; L, Leu; M, Met; N, Asn; P, Pro; Q, Gln; R, Arg; S, Ser; T, Thr; V, Val; W, Trp; and Y, Tyr.

Figure 3.

Cumulative survival curves for 366 patients with unifocal hepatocellular carcinoma (HCC) according to tumor stage. The 5-year survival rates for stage I, II, IIIA, IIIB, and IV HCC are 63%, 43%, 22%, 17%, and 5%, respectively (log-rank test, P < 0.000001).

Figure 4.

Cumulative survival curve for 366 patients of primary unifocal hepatocellular carcinoma (HCC). HCC with β-catenin mutations had a significantly better 5-year survival rate (P = 0.00003).

Figure 5.

Expression of β-catenin protein. A: Diffuse staining of β-catenin along the tumor cell membranes of HCC is shown. B: Membranous staining of β-catenin of mixed positive (right) and negative areas (left) is shown. C: Abundant tumor cell nuclei are strongly positive for β-catenin. D: Scattered tumor cells are positive for nuclear β-catenin (arrows). Immunohistochemical stain for β-catenin; original magnification ×340 (A–D).

Figure 6.

Cumulative survival curve for primary unifocal hepatocellular carcinoma (HCC) that had nuclear β-catenin protein expression. HCC with nuclear β-catenin protein expression and β-catenin mutation (n = 31) had a better 5-year survival rate than HCC with nuclear β-catenin protein expression but without mutation of the gene (n = 39) (P < 0.007, log-rank test).