INTRODUCTION: Cathepsin L (CTSL) is a kind of the SARS-entry-associated CoV-2's 
proteases, which plays a key role in the virus's entry into the cell and 
subsequent infection. We investigated the association between the expression 
level of CTSL and overall survival in Glioblastoma multiforme (GBM) patients, to 
better understand the possible route and risks of new coronavirus infection for 
patients with GBM.
METHODS: The expression level of CTSL in GBM was analyzed using TCGA and CGGA 
databases. The relationship between CTSL and immune infiltration levels was 
analyzed by means of the TIMER database. The impact of CTSL inhibitors on GBM 
biological activity was tested.
RESULTS: The findings revealed that GBM tissues had higher CTSL expression 
levels than that of normal brain tissues, which was associated with a 
significantly lower survival rate in GBM patients. Meanwhile, the expression 
level of CTSL negatively correlated with purity, B cell and CD8+ T cell in GBM. 
CTSL inhibitor significantly reduced growth and induced mitochondrial apoptosis.
CONCLUSION: According to the findings, CTSL acts as an independent prognostic 
factor and can be considered as promising therapeutic target for GBM.