APOA1 mRNA and protein in kidney renal clear cell carcinoma correlate with the disease outcome

Renal cancer is one of the most common malignant tumors with high mortality, and kidney renal clear cell carcinoma (KIRC) is the most common type of renal cancer. We attempted to evaluate the clinical and prognostic significance of Apolipoprotein A1 (APOA1) mRNA and protein in KIRC patients. Clinical data along with RNA-sequencing data were downloaded from UCSC Xena. The Human Protein Atlas database was searched to reveal APOA1 protein expression profiles in KIRC and normal renal tissues. The TIMER database was applied to determine the correlations of APOA1 with immune cells and PD-1 and PD-L1 in KIRC. Ninety-one cases of KIRC patients and 93 healthy controls from our hospital were enrolled for clinical validation. Levels of APOA1 mRNA in KIRC tissues (N = 535) are not only lower than the levels in normal renal tissues (N = 117), but also in paired normal renal tissues (N = 72). High expression of APOA1 mRNA at the time of surgery was correlated with worse overall survival (OS) (HR 1.66; p = 0.037) and disease-free survival (DFS) (HR 1.65; p = 0.047), and APOA1 DNA methylation was linked to worse OS (HR 2.1; p = 0.001) rather than DFS (HR 1.12; p = 0.624) in KIRC patients. Concentrations of preoperative serum APOA1 protein were markedly decreased in KIRC patients compared to healthy controls (p < 0.01), and low levels of APOA1 protein predicted less favorable OS than those with high levels (HR = 2.84, p = 0.0407). APOA1 negatively correlated with various immune cell infiltrates and PD-L1 expression (r = − 0.283, p = 2.74e−11) according to the TIMER database. Low levels of APOA1 mRNA at the time of surgery predict favorable survival in KIRC patients. Our results provide insights to identify a novel prognostic index with great clinical utility.