Peptide vaccine as an adjuvant therapy for glypican-3-positive hepatocellular carcinoma induces peptide-specific CTLs and improves long prognosis

Abstract

There is no established postoperative adjuvant therapy for hepatocellular carcinoma (HCC), and improvement of patient prognosis has been limited. We conducted long-term monitoring of patients within a phase II trial that targeted a cancer antigen, glypican-3 (GPC3), specifically expressed in HCC. We sought to determine if the GPC3 peptide vaccine was an effective adjuvant therapy by monitoring disease-free survival and overall survival. We also tracked GPC3 immunohistochemical (IHC) staining, CTL induction, and postoperative plasma GPC3 for a patient group that was administered the vaccine (n = 35) and an unvaccinated patient group that underwent surgery only (n = 33). The 1-y recurrence rate after surgery was reduced by approximately 15%, and the 5-y and 8-y survival rates were improved by approximately 10% and 30%, respectively, in the vaccinated group compared with the unvaccinated group. Patients who were positive for GPC3 IHC staining were more likely to have induced CTLs, and 60% survived beyond 5 y. Vaccine efficacy had a positive relationship with plasma concentration of GPC3; high concentrations increased the 5-y survival rate to 75%. We thus expect GPC3 vaccination in patients with HCC, who are positive for GPC3 IHC staining and/or plasma GPC3 to induce CTL and have significantly improved long-term prognosis.

Keywords: cytotoxic T lymphocyte; glypican-3; hepatocellular carcinoma; immunohistochemical staining; peptide vaccine.

Figure 1

Kaplan‐Meier curves for disease‐free survival (DFS) and overall survival (OS). A, After surgery, DFS for patients who were vaccinated (n = 35) was not significantly different compared with that for unvaccinated patients (n = 33). B, The survival rate was significantly higher in the vaccinated group than in the unvaccinated group after 5 y (70.6% vs 57.6%) and 8 y (67.1% vs 38.9%)

Figure 2

Kaplan‐Meier curves for the time until second recurrence from the first recurrence and OS after the first recurrence. A, Vaccinated patients (n = 28) showed a longer time to the second recurrence from the first recurrence after surgery compared with unvaccinated patients (n = 26). B, The vaccinated group had better prognosis 5 y after the first recurrence compared with the unvaccinated group

Figure 3

Kaplan‐Meier curves for overall survival (OS). A, Patients who had recurrence after 1 y (n = 31) had significantly better OS than patients who had a recurrence within 1 y (n = 23). B, OS improved in the vaccinated group regardless of whether recurrence took place within 1 y or later; some patients survived long term (beyond 5 y)

Figure 4

Kaplan‐Meier curves for disease‐free survival (DFS) and overall survival (OS). A, Glypican‐3 (GPC3)‐positive patients who were unvaccinated had a higher recurrence rate after 1 y compared with other groups. B, Prognosis for vaccinated patients in the GPC3‐positive group was as good as that for the GPC3‐negative group and better than that for the unvaccinated group

Figure 5

Relationship between CTL number, overall survival (OS), glypican‐3 (GPC3) immunohistochemical (IHC) staining and plasma GPC3. A, In the GPC3‐positive group, 15/25 cases (60%) were long‐term (beyond 5 y) survivors. Of the long‐term survivors, 11/15 (73%) had CTL induction. B, Of the patients who were positive for both GPC3 IHC staining and plasma GPC3 (n = 12), 9/12 (75%) were long‐term (beyond 5 y) survivors. Of the long‐term survivors, 7/9 (77.8%) had CTL induction

Figure 6

Kaplan‐Meier curves for overall survival (OS). A, There were no drop‐outs due to death in patients who were positive for glypican‐3 (GPC3) immunohistochemical (IHC) staining, plasma GPC3, and CTL induction (n = 8). B, There were patients who were positive for GPC3 IHC staining and negative for postoperative plasma GPC3 (n = 13). Prognosis for patients with CTL induction (n = 7) was good, with a 5‐y survival rate of 57.1%

Figure 7

Changes in plasma glypican‐3 (GPC3) according to GPC3 IHC staining and the vaccination. Long‐term survivors are indicated by red lines, and dead patients are indicated by blue lines. A, Vaccinated patients who were GPC3 immunohistochemical (IHC) staining positive and maintained high plasma GPC3 levels tended to have increased long‐term survival. B, High plasma GPC3 levels were associated with death in the GPC3 IHC staining positive and unvaccinated group. C, Long‐term survivors who were GPC3 IHC staining negative often only had a slight increase in plasma GPC3 levels. D, High plasma GPC3 levels were associated with death in the GPC3 IHC staining negative and unvaccinated group

Figure 8

Kaplan‐Meier curves for overall survival (OS) in patients who were positive for GPC3 immunohistochemical (IHC) staining. A, In the unvaccinated group, OS was poor when plasma GPC3 was high. B, In the vaccinated group, OS was increased in patients with high levels of plasma GPC3

Figure 9

CTL induction and plasma glypican‐3 (GPC3) levels in individual patients. A representative CTL induction image obtained by ELISpot assay is shown. A, Long‐term survivors who were positive for GPC3 IHC staining (n = 16) had higher levels of plasma GPC3 and were more likely to have CTL induction. B, Of the dead patients (n = 9), a majority had an early relapse with low levels of plasma GPC3 and low CTL induction