Landscape of somatic mutations in EAC
We defined 30 FMGs in American EAC patients from TCGA cohort, and the top five FMGs were TP53 (78%), TTN (49%), MUC16 (29%), SYNE1 (28%), and HMCN1 (23%) (Figure 1A). Meanwhile, we also defined 30 FMGs in British EAC patients from ICGC cohort, and the top five FMGs were TP53 (72%), TTN (55%), MUC16 (33%), CSMD3 (22%), and LRP1B (22%) (Figure 1B). Intriguingly, some FMGs were shared in both American and British patients, including ARID1A, CSMD1, CSMD3, EYS, FAT3, FLG, HMCN1, LAMA1, LRP1B, MUC16, PCLO, RYR2, RYR3, SMAD4, SPTA1, SYNE1, TP53, and TTN (Figure 1C). Then, we focused on these common FMGs in subsequent analysis.
RYR2 mutation was associated with TMB and prognosis
The TMB in TCGA cohort ranged from 0.04 to 31.70/MB with a median of 2.1/MB; the TMB in ICGC cohort ranged from 0.02 to 36.94/MB with a median of 2.3/MB. Among common FMGs, patients with mutations in ARID1A, CSMD3, EYS, HMCN1, LAMA1, MUC16, PCLO, RYR2, RYR3, SPTA1, SYNE1, and TTN possessed dramatically higher TMB in both TCGA and ICGC cohorts (Figure 2A). Previous research has demonstrated that higher TMB suggested a favorable prognosis[19]. Thus, survival analysis was further performed to identify whether these FMGs associated with increased TMB were also related to the OS of patients with EAC. As shown in Additional file 1: Figure S1, patients with RYR2 mutation had a significantly longer OS (P <0.05). Univariate Cox analysis revealed the HRs of RYR2 mutation was 0.645 [95% confidence interval (CI): 0.433-0.962] (P <0.05) (Figure 2B). After taking into account age, gender, and mutation of other FMGs, RYR2 mutation still remained statistically significance (P <0.05), suggesting that RYR2 mutation was an independent protective factor of prognosis in EAC (Figure 2B).
RYR2 mutation promotedantitumor immunity in EAC
According to GSEA analysis, we found plenty of immune-related GO terms were enriched in RYR2 mutation phenotype, such as “Response to chemokine” (NES =2.192, FDR <0.001), “Chemokine-mediated signaling pathway” (NES =2.180, FDR <0.001), “Interleukin-2 production” (NES =2.177, FDR <0.001), “Lymphocyte mediated immunity” (NES =2.152, FDR <0.001), and “Granulocyte chemotaxis” (NES =2.180, FDR <0.001) (Figure 3A). RYR2 mutation was also significantly associated with abundant immune-related KEGG pathways, such as “Th1 and Th2 cell differentiation” (NES =2.194, FDR <0.001), “Cytokine-cytokine receptor interaction” (NES =2.185, FDR <0.001), “Natural killer cell mediated cytotoxicity” (NES =2.157, FDR <0.001), “T cell receptor signaling pathway” (NES =2.140, FDR <0.001), and “IL-17 signaling pathway” (NES =2.121, FDR <0.001) (Figure 3B). In addition, we further applied the ssGSEA algorithm to evaluate the relative infiltration abundance of 28 immune cell types. Consistent with the above results, the abundance of most immune cells infiltration in patients with RYR2 mutation was significantly higher than patients without RYR2 mutation (P <0.05) (Figure 3C and Additional file 2: Figure S2). Overall, these results indicated RYR2 mutation might promoted antitumor immunity in EAC, which had important implications for immunotherapy.
RYR2 mutation suggested better immunotherapy response
Patients with RYR2 mutation had higher expression level of PD-L1, PD-L2, PD-1, and CTLA-4 than patients without RYR2 mutation (Figure 4A). The T cell-inflamed GEP algorithm was utilized and found a superior inflamed score in RYR2 mutation phenotype (Figure 4B). We further applied the TIDE algorithm to assess the TIDE prediction score of each patient and whether a patient would respond to immunotherapy. The TIDE prediction score was lower in RYR2 mutation phenotype (Figure 4C). In addition, the proportion of responders to immunotherapy in patients with RYR2 mutation was higher relative to patients without RYR2 mutation (mutant type vs. wild type: 43% vs. 16%) (Figure 4D). SubMap analysis also revealed the dramatical expression similarity between the RYR2 mutation phenotype and patients with anti-PD-L1 therapy (FDR <0.05) (Figure 4E). These results indicated that RYR2 mutation suggested better immunotherapy response.
Identify potential antitumor drugs associated with RYR2 status
We retrieved the imputed response to 138 antitumor drugs in EAC patients from a previous study to identify potential antitumor drugs with specific sensitivity to each phenotype[17]. As shown in Figure 5A, the estimated IC50 of nine drugs were significantly differed between two groups. Patients without RYR2 mutation were more sensitive to Lenalidomide, MG-132, and SB216763, while patients with RYR2 mutation were more sensitive to A-770041, A-443654, CMK, Erlotinib, JW-7-52-1, and Rapamycin. Drugs were associated with RYR2 wild type mainly targeted protein stability and degradation and WNT signaling, while drugs were associated with RYR2 mutation mainly targeted EGFR signaling, Kinases, and PI3K/MTOR signaling (Figure 5B). These results provided additional reference for antitumor therapies of different RYR2 status.