CDKN2A or CDKN2B homozygous deletion with high-immune infiltration as a favorable prognostic factor for lung adenocarcinoma.
Authors: Tan Benxu , Chen Yonghong , Xia Lei , Yu Xian , Huang Yusheng , Zhang Ni , Peng Yuan , Song Mengmeng , Ji Liyan , Li Pansong , Xia Xuefeng , Yang Zhenzhou 
Published: June 2021

e20543

Background: CDKN2A and CDKN2B both acted as tumor suppressor genes by regulating the cell cycle, which in humans were located at chromosome 9, band p21.3. The frequencies of homozygous deletion (HomDel) in CDKN2A and CDKN2B in lung adenocarcinoma (LUAD) were 12.5% and 12.1%, respectively. However, the genomic, immunogenomic features and impact on the prognosis of LUAD patients with CDKN2A/B HomDel were still unclear. Methods: The cohort of this study was from The Cancer Genome Atlas (TCGA). A total of 508 LUAD patients, including 99 CDKN2A/B HomDel (homdel) and 509 CDKN2A/B wild (wild). This study explored the difference of genomic and immunogenomic landscape between homdel and wild by analysis of whole-exome sequencing (WES) and RNA sequencing data. Results: The most frequently mutated genes were TP53, TTN, MUC16, and CSMD3. Their frequencies in homdel and wild are 46% and 48%, 43% and 46%, 35% and 41%, 33% and 38%, respectively. There was no significant difference of tumor mutational burden (TMB) between homdel and wild (median TMB, 133 in homdel vs 177 in wild; Wilcoxon test, p = 0.11), and clinical characteristics including age, gender, smoking history, and tumor stage were not significantly different between homdel and wild. Homdel had a shorter overall survival (OS) than wild (Log-rank test, p = 0.04, Hazard Ratio: 0.7, 95% CI: 0.49-1.02), but there was no significant difference in progression-free survival (PFS) (Log-rank test, p = 0.05, Hazard Ratio: 0.73, 95% CI: 0.51-1.04). We used single sample gene set enrichment analysis (ssGSEA) to calculate the enrichment score (ES) of 25 immune-related pathways such as antigen presentation and T cell-mediated immunity, and then used the consensus clustering algorithm (ConsensusClusterPlus) to cluster homdel and wild respectively, and both clustered into low and high immune infiltration groups. For the high immune infiltration and low immune infiltration in homdel and wild, high immune infiltration had a longer OS (Log-rank test, p = 0.009, Hazard Ratio: 2.19, 95% CI: 1.22-3.94) and PFS (Log-rank test, p = 0.044, Hazard Ratio: 1.8, 95% CI: 1.01-3.2) than low immune infiltration in homdel. However, there was no significant heterogeneity between high and immune infiltration in terms of PFS (Log-rank test, p = 0.28, Hazard Ratio: 1.21, 95% CI: 0.87-1.68) and OS (Log-rank test, p = 0.96, Hazard Ratio: 1.01, 95% CI: 0.71-1.44) in the wild group, the wild group had longer OS than homdel group with low immune infiltration (Log-rank test, p = 0.003, Hazard Ratio: 0.5, 95% CI: 0.29-0.88), while had the same OS with homdel with high immune infiltration, irrespective of immune infiltration. And so was PFS (Log-rank test, p = 0.005, Hazard Ratio: 0.48, 95% CI: 0.27-0.82). Conclusions: CDKN2A/B homdel was an unfavorable prognostic factor for LUAD, but which with high immune infiltration might improve patient survival time.