Abnormal ATPase H+ Transporting Accessory Protein 1 (
ATP6AP1
) expression may promote carcinogenesis. We investigated the association of
ATP6AP1
with breast cancer (BC) and COVID-19. The Oncomine, Gene Expression Profiling Interactive Analysis, Human Protein Atlas and Kaplan-Meier plotter databases were used to evaluate the expression and prognostic value of
ATP6AP1
in BC.
ATP6AP1
was upregulated in BC tissues, and higher
ATP6AP1
expression was associated with poorer outcomes. Data from the Tumor Immune Estimation Resource, Tumor-Immune System Interaction Database and Kaplan-Meier plotter indicated that
ATP6AP1
expression correlated with immune infiltration, and that its prognostic effects in BC depended on tumor-infiltrating immune cell subtype levels. Multiple databases were used to evaluate the association of
ATP6AP1
with clinicopathological factors, assess the mutation and methylation of
ATP6AP1
, and analyze gene co-expression and enrichment. The
ATP6AP1
promoter was hypomethylated in BC tissues and differentially methylated between different disease stages and subtypes. Data from the Gene Expression Omnibus indicated that
ATP6AP1
levels in certain cell types were reduced after SARS-CoV-2 infections. Ultimately, higher
ATP6AP1
expression was associated with a poorer prognosis and with higher or lower infiltration of particular immune cells in BC. BC patients may be particularly susceptible to SARS-CoV-2 infections, which may alter their prognoses.