Esophageal squamous cell carcinoma (ESCC) is the most important pathological type of esophageal cancer with high incidence and limited efficient therapies in China and worldwide. Understanding of ESCC genomic features is advantageous for exploring clinical therapeutic strategies.
Deep sequencing targeting 450 cancer genes was performed on FFPE and matched blood samples collected from 90 Chinese ESCC patients(pts) with a median age of 60 years old. Genomic alterations (GAs) including single nucleotide variations, short and long indel, gene rearrangements and copy number variations were analyzed. Tumor mutation burden (TMB) was assessed in all samples by standard NGS algorithms. The expression of PD-L1 in 44 samples was evaluated by IHC (28-8 Ab).
The most commonly found GAs were mutations in TP53 (94.4%), FGF3 (43.3%), CCND1 (43.3%), FGF4 (42.2%), FGF19 (42.2 %), CDKN2A (36.7%), NOTCH1 (25.6%), PIK3CA (22.2%), and ERBB2 amp(2.2%).Compared with TCGA data, the frequency of TP53 and ERBB2 amp mutations was similar, while the frequency of NOTCH1 mutations was significantly higher (25.6% vs 11%) and the frequency of EGFR amp was lower (5.6% vs 19%) in Chinese cohort. In addition, 4 of 90 samples harbored germline mutations (SDHA, RAD51C, PALB2 and BCL2L11). Among these GAs, 73.3% mutations were in cell cycle (62.2%) and PI3K/AKT (42.2%) pathway. In Chinese ESCC pts, the median TMB was 7.0 muts/Mb, and some pts showed high TMB (33.3%pts≥10 muts/Mb,11.1%pts≥20 muts/Mb). 15.6% pts (TMB≥10 muts/Mb) harbored chromosome 11q13 (FGF3/4/19 and CCND1) amp, which may be related to immunotherapy hyper-progression. Based on the IHC analysis, 10 of 44 Chinese pts showed positive (TPS≥1%) PD-L1 expression, and 7 of them also showed high TMB (≥10 muts /Mb). However, no correlation was found between high TMB and PD-L1 expression.
In this study, we found that the frequencies of GAs, such as EGFR and NOTCH1 alterations, were different between Chinese and western ESCC pts. Compared to Western ESCC pts, the positivity of PD-L1 expression was similar, while TMB was higher in Chinese ESCC pts. These findings suggested potential therapeutic targets for targeted and immunotherapies of Chinese ESCC pts.
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M. Yao, A. Liu, Y. Zhou: Employee: OrigiMed. All other authors have declared no conflicts of interest.