Overview of molecular characteristics between the two groups
37 pairs of tumor samples and control blood samples were comprehensively characterized via WES. There were 9,724 mutated genes, and the top three mutation types were missense mutation, splice site and nonsense mutation, respectively. The mutation landscape is shown in Fig. 1B, and top five mutated genes were BCLAF1, MUC4, TP53, FMN2 and TTC7A with mutation prevalence rates of 73%, 57%, 49%, 49% and 46% in our cohort, respectively. The results are basically consistent with previous research reports[16, 17]. Moreover, we identified 32 differential genes (p < 0.05, Supplementary table 1) between two groups, of which 25 genes were only detected in the recurrence group (Fig. 1C). TP53 (recurrence group vs. non-recurrence group: 75% VS. 36%) and TTN (recurrence group vs. non-recurrence group: 67% VS. 28%) had the highest mutation frequencies in 32 differential genes. Then, we compared TMB and tumor neoantigen burden (TNB) between the two groups and found that both of two did not differ significantly between the two groups (Fig. 1D, E). Further, patients were divided into two groups according to the median TMB (mTMB = 3.01), namely TMB-High group (TMB ≥ 3.01) and TMB-Low group (TMB < 3.01). The analysis results showed that TMB was not associated with RFS and OS (Fig. 1F, G).
Univariate and multivariate cox regression analysis on relapse-free survival of clinical factors and molecular mutation characteristics
Firstly, in order to understand the impact of clinical factors on patients' RFS, we conducted univariate and multivariate cox regression analysis. The clinical factors including gender, age, alpha-fetoprotein (AFP) categories, tuomr size, tumordifferentiation, tumor number, microvascular invasion (MVI) and treatment before LT. The results of univariate cox regression analysis showed that both high AFP and positive MVI were significantly associated with poor RFS (p < 0.05, Table 2, Fig. 2A, B). However, multivariate cox regression analysis results showed that none of the 8 clinical factors was an independent prognostic factor for RFS.
Table 2
Univariate regression analysis and multivariate regression analysis of 8 clinical factors on RFS.
Variables | Univariable analysis | Mutivariable analysis |
HR | CI95% | P.value | HR | CI95% | P.value |
Gender (female vs male) | 0 | 0-Inf | 0.132 | | | |
Age (year) (< 65 vs ≥ 65) | 0.62 | 0.18–2.21 | 0.46 | | | |
AFP categories (< 25 ng/ml vs ≥ 25 ng/ml) | 0.30 | 0.1–0.94 | 0.029 | 0.42 | 0.12–1.44 | 0.17 |
Tumor size (cm) (< 8 cm vs ≥ 8 cm) | 2.54 | 0.71–9.06 | 0.137 | | | |
Tumor differentiation (low vs high) | 0 | 0-Inf | 0.077 | | | |
Tumor number (single vs multiple) | 0.58 | 0.2–1.7 | 0.314 | | | |
Microvascular invasion (negative vs positive) | 3.57 | 1.26–10.13 | 0.011 | 2.64 | 0.86–8.03 | 0.08 |
Treatment.BeforeLT(Yes vs No) | 0.92 | 0.31–2.69 | 0.877 | | | |
Table 3
Univariate regression analysis and multivariate regression analysis of 8 clinical factors on OS.
Variables | Univariable analysis | Mutivariable analysis |
HR | CI95% | P.value | HR | CI95% | P.value |
Gender (female vs male) | 0 | 0-Inf | 0.247 | | | |
Age (year) (< 65 vs ≥ 65) | 0.53 | 0.12–2.44 | 0.407 | | | |
AFP categories (< 25 ng/ml vs ≥ 25 ng/ml) | 0.77 | 0.25–2.45 | 0.663 | 1.19 | 0.34–4.13 | 0.78 |
Tumor size (cm) (< 8 cm vs ≥ 8 cm) | 1.34 | 0.29–6.23 | 0.711 | | | |
Tumor differentiation (low vs high) | 0 | 0-Inf | 0.117 | | | |
Tumor number (single vs multiple) | 1.43 | 0.31–6.61 | 0.649 | | | |
Microvascular invasion (negative vs positive) | 3.09 | 0.98–9.75 | 0.043 | 3.29 | 0.95–11.38 | 0.06 |
Treatment.BeforeLT(Yes vs No) | 1.32 | 0.42–4.17 | 0.637 | | | |
In terms of molecular mutation characteristics, the results of univariate cox regression analysis showed that 304 genes were significantly associated with RFS (p < 0.05), and among them, 301 gene mutants including TTN, NDUFS7, FOXO3, etc (Fig. 2C-E) were significantly associated with poor RFS (Supplementary Table 2). In order to eliminate multiple confounding factors and find indicators that can independently predict recurrence, we separately included age, gender, AFP, MVI and 304 genes significantly associated with RFS into multivariable cox regression analysis and found that 205 gene mutants were significantly associated with poorer RFS (p < 0.05, Supplementary Table 3). Examples listing three genes (TTN, NDUFS7, FOXO3) are shown in Fig. 2G, H.
Univariate and multivariate cox regression analysis on overall survival of clinical factors and molecular mutation characteristics
Similarly, we used the same analysis method to explore the indicators related to OS. In terms of 8 clinical factors, results of univariate cox regression analysis showed that only MVI were significantly associated with poor OS (p < 0.05, Table 4, Fig. 3A). However, multivariate cox regression analysis results showed that none of the 8 clinical factors was an independent prognostic factor for OS. The results of gene mutation showed that 811 genes were detected significantly associated with OS (p < 0.05), and among them, 810 gene mutants including TTN, NDUFS7, FOXO3, etc. (Fig. 3B-D) were significantly associated with poor OS (p < 0.05, Supplementary Table 4). Then multivariate cox regression models were performed and there were still 482 gene mutations were independent risk factors for OS (p < 0.05, Supplementary Table 5). Examples listing the above three genes (TTN, NDUFS7, FOXO3) are shown in Fig. 3E-G.
Table 4
gene list of 13-gene-based model
Gene | Mutation situation | Univariate analysis of RFS | Univariate analysis of OS | Multivariate analysis of RFS | Multivariate analysis of OS |
N1 | N2 | P.value | HR | CI95. | P.value | HR | CI95. | P.value | HR | CI95. | P.value | HR | CI95. | P.value |
BOD1L1 | 3 | 0 | 0.03 | 7.12 | 1.95–26.01 | 0.00 | 3.58 | 0.95–13.55 | 0.05 | 6.18 | 1.559–24.53 | 0.01 | 5.66 | 1.303–24.599 | 0.02 |
C14orf159 | 3 | 0 | 0.03 | 8.11 | 2.25–29.18 | 0.00 | 3.67 | 0.95–14.21 | 0.04 | 33.64 | 5.163–219.24 | 0.00 | 11.12 | 1.724–71.669 | 0.01 |
CSPG4 | 3 | 0 | 0.03 | 9.92 | 2.68–36.62 | 0.00 | 6.80 | 1.88–24.61 | 0.00 | 17.26 | 3.435–86.697 | 0.00 | 7.05 | 1.702–29.233 | 0.01 |
EML6 | 3 | 0 | 0.03 | 8.48 | 2.35–30.53 | 0.00 | 4.58 | 1.18–17.83 | 0.02 | 19.95 | 4.158–95.719 | 0.00 | 9.66 | 1.767–52.806 | 0.01 |
KCNB2 | 3 | 0 | 0.03 | 5.98 | 1.51–23.68 | 0.00 | 6.58 | 1.68–25.77 | 0.00 | 6.62 | 1.21-36.154 | 0.03 | 5.01 | 1.005–24.935 | 0.05 |
OR4D10 | 3 | 0 | 0.03 | 7.92 | 1.99–31.47 | 0.00 | 6.75 | 1.74–26.25 | 0.00 | 23.46 | 4.071-135.201 | 0.00 | 13.26 | 2.332–75.356 | 0.00 |
PACS2 | 3 | 0 | 0.03 | 6.28 | 1.59–24.81 | 0.00 | 6.16 | 1.58–24.02 | 0.00 | 7.87 | 1.657–37.381 | 0.01 | 9.70 | 1.932–48.649 | 0.01 |
SPRED3 | 3 | 0 | 0.03 | 7.39 | 1.87–29.24 | 0.00 | 7.23 | 1.85–28.19 | 0.00 | 12.44 | 2.178–71.041 | 0.01 | 5.45 | 1.086–27.322 | 0.04 |
TAF1 | 3 | 0 | 0.03 | 7.53 | 1.89–30.04 | 0.00 | 6.45 | 1.66–25.12 | 0.00 | 18.23 | 3.397–97.846 | 0.00 | 13.34 | 2.513–70.78 | 0.00 |
VRK3 | 3 | 0 | 0.03 | 3.57 | 1.11–11.47 | 0.02 | 9.10 | 2.59–31.94 | 0.00 | 5.49 | 1.139–26.45 | 0.03 | 11.56 | 1.914–69.764 | 0.01 |
FOXO3 | 4 | 1 | 0.03 | 3.59 | 1.08–11.9 | 0.03 | 3.64 | 0.93–14.21 | 0.05 | 3.81 | 1.128–12.86 | 0.03 | 4.36 | 1.049–18.081 | 0.04 |
NDUFS7 | 4 | 1 | 0.03 | 3.75 | 1.17–12.03 | 0.02 | 7.67 | 2.12–27.71 | 0.00 | 4.51 | 1.075–18.878 | 0.04 | 7.11 | 1.53-32.996 | 0.01 |
TTN | 8 | 7 | 0.04 | 4.84 | 1.36–17.21 | 0.01 | 11.82 | 1.52–91.81 | 0.00 | 6.21 | 1.455–26.505 | 0.01 | 25.34 | 2.257-284.425 | 0.01 |
N1: recurrence group, n = 12; N2 :non-recurrence group,n = 25. |
Establish of the 13-gene-based relapse predicting and prognostic model
To search for molecular signatures that predict recurrence in liver transplanted HCC patients, we performed a genetic analysis. Among the 32 differential genes between the recurrence group and the non-recurrence group, the genes with high mutation frequency in the recurrence group were intersected with the RFS and OS independent predictive factors after multivariate cox regression analysis, and 13 genes were obtained (Table 4). Among them, 11 gene mutations were detected only in the relapse group. The samples with at least one mutation in these 13 genes were defined as high-risk group, and all 13 wild-type genes were defined as low-risk group[18]. The results showed that compared with the low-risk group, the RFS (p = 0.0042) and OS (p = 0.0074) of the high-risk group were significantly poor (Fig. 4A, B).
Taking into account the covariates that may affect RFS or OS, we performed multivariate analysis, and the results showed that the13-gene-based model had a significant impact on both RFS and OS, and the high-risk group tended to have worse RFS (p = 0.014) and OS (p = 0.01) than the low-risk group (Fig. 4C, D). The ROC curve of the performed 13-gene-based model to illustrate the accuracy (area under the curve, AUC: 0.73) in Fig. 4E. The above results indicate that the 13-gene-based model can not only predict the recurrence of HCC patients who undergo LT, but also serve as a prognostic indicator for the OS of such patients. It is worth noting that this result needs to be verified in future prospective trials with larger sample sizes.