Abstract:

Objective This study aims to clarify the expression of fatty acid amide hydrolase（FAAH）in different types of cancer and its relationship with survival prognosis and tumor immune microenvironment. Methods The relationship between the expression pattern and prognosis of FAAH in cancer was analyzed by using the cancer and paracancerous tissue data from 33 types of cancer in the TCGA database combined with the transcriptome of normal tissues and follow⁃up survival data in the GTEx database. The CIBERSORT algorithm and Pearson correla⁃ tion coefficient were used to study the correlation between FAAH expression and tumor immune infiltration. Results The expression map showed that FAAH was significantly highly expressed in 7 types of cancer including breast invasive carcinoma and prostate cancer（P < 0.001），whereas lower in 15 types of cancer including renal clear cell carcinoma and lung squamous cell carcinoma（P < 0.001）. Survival analysis showed that for clear cell renal cell carcinoma or gastric adenocarcinoma，the patients with higher expression of FAAH had better prognosis than those with lower expression（OS，DSS，DFI，and PFI）and longer survival period（P < 0.05）. Immune microenvironment analysis showed that CD4 + T memory cells and γδ T cells were markedly reduced in the lower FAAH expression group with clear cell renal cell carcinoma（P < 0.05），and there was less monocyte infiltration in the lower FAAH expression group with gastric adenocarcinoma（P < 0.05）. Conclusions Pan⁃cancer analysis shows that a lower expression of FAAH is common in multiple types of cancer，significantly associating with poor survival prognosis. The expression of FAAH is associated with immune infiltration，which can be used as a prognostic biomarker and a potential target for cancer immunotherapy.

Key words: FAAH, prognosis, immune infiltrate, pan?cancer analysis