Abstract
Background
Obesity has been associated with better outcomes in localized and metastatic clear cell renal cell carcinoma (ccRCC), as well as improved survival on immunotherapy treatment. However, the mechanisms underlying this association remain unclear. Leptin is an adipokine secreted by adipocytes, and circulating levels of leptin are higher in individuals with obesity. Additionally, leptin promotes inflammation and angiogenesis and has been proposed as pro-tumorigenic in colorectal and breast cancer. In this study, we examined how circulating leptin levels relate to both tumor and perinephric fat transcriptomic patterns in a cohort of ccRCC patients by evaluating the associations with body mass index (BMI), sex, and immune-related gene expression patterns.
Methods
We conducted a retrospective cohort study of 92 treatment-naïve ccRCC patients undergoing nephrectomy at Memorial Sloan Kettering Cancer Center. Available data included circulating leptin from fasting blood samples, clinical characteristics from medical records, and, in a subset of patients, RNA sequencing from tumor and perinephric fat specimens. We analyzed differentially expressed genes (DEG) according to circulating leptin levels using Gene Set Enrichment Analysis (GSEA) to describe pathways that were enriched in patients with high levels of leptin. We performed analysis for the whole cohort and stratified by sex based on differences in leptin levels.
Results
From the 92 patients with available peripheral leptin measurements, 51 and 44 had available tumor and perinephric fat RNA sequencing data, respectively. Of these, 64 (70%) were male, the median age was 60 years old, and most tumors were low grade and stage. Leptin distribution was significantly different in males than females, with circulating leptin levels of 7 ng/ml (IQR 4-14) and 22 ng/ml (IQR 9-52), respectively. Higher BMI was associated with higher leptin levels, with a correlation coefficient of 0.63 (p<0.001) in males and 0.77 (p<0.001) in females. GSEA of tumor DEGs by circulating leptin, showed upregulation of pathways related to adaptive immune activity in patients with higher leptin levels across sexes, although this association was attenuated in females. Strikingly, in the perinephric fat there were stark differences in opposite directions in female and male specimens, with females showing significantly enriched transcription of genes associated with B cell signaling, humoral and adaptive immune responses.
Conclusions
Higher leptin levels were associated with a modest increase of immune-related gene expression in the tumors in both males and females, but significantly different directional changes were observed in the perinephric fat. Circulating leptin may be involved in peritumoral immune responses which may link host factors to sex related tumor outcomes. Further studies should aim to address the relationship between leptin activity and the tumor and fat microenvironment.
DOD CDMRP Funding: yes
Keywords: leptin, obesity paradox, clear cell RCC, perinephric fat, immune pathways