Analysis of clinicopathological parameters, immunological status

RNA‐Seq data and related clinical data were collected from the TCGA portal. Data were then grouped according to different clinicopathological parameters, and the expression of CYP2A6 was evaluated. Survival analysis was investigated with a Kaplan–Meier (KM) plot (KM plotter, https://www.kmplot.com/) [14]. To evaluate the relationship between CYP2A6 expression and immune cell abundance, we performed a deconvolution of 22 immune cell types using the CIBERSORT algorithm [15]. The LM22 signature was used as a reference and absolute tumor purity scores were used to assess the abundance of 22 immune cell types in each sample. In addition, the TIMER database (https://cistrome.shinyapps.io/timer/) was also used to identify the correlation between immune cells and CYP2A6.