CIRCULATING LEPTIN AND IMMUNE-RELATED TRANSCRIPTOMIC SIGNATURES IN TUMOR AND PERINEPHRIC OF CLEAR CELL RENAL CELL CARCINOMA PATIENTS

Introduction

Although obesity has been associated with improved outcomes in localized and metastatic clear cell renal cell carcinoma (ccRCC), the exact underlying mechanisms remain unknown. Obese individuals have higher circulating leptin, a metabolically and immunologically active adipokine. Leptin has been shown to promote inflammation, angiogenesis and modulate tumor growth and invasiveness in breast and colorectal cancers. Although previous attempts to understand the relationship between leptin and cancer have been made, only a few studies have focused on perinephric fat (PNF), where leptin exerts most of its effect. Furthermore, obese patients with ccRCC have been shown to have increased peritumoral adipose tissue inflammation. In this study, we examined how circulating leptin levels, and a transcriptomic signature of leptin activation, relate to both tumor and PNF immune-related transcriptomic patterns in a cohort of localized ccRCC patients.

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 data from tumor and PNF specimens. We performed differentially expressed genes (DEG) analysis according to circulating leptin levels and followed by Gene Set Enrichment Analysis (GSEA) with GO Biological Process gene set collection to describe pathways that were enriched by the changes of blood leptin level. Additionally, we used the Molecular Signatures Database (MSigDB) to identify a leptin downstream signature, which we validated in our cohort. This signature was then correlated to immune cell scores in the tumor and PNF. We performed the analysis both in the cohort as a whole and stratified by sex.

Results

From the 92 patients, 51 and 54 had available tumor and PNF RNA sequencing data, respectively. In total, 64 (70%) were male and most tumors were low grade and stage. Leptin distribution was significantly different in males (median 7 ng/ml, IQR 4-14) than females (median 22 ng/ml, IQR 9-52). 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. Tumor GSEA results showed upregulation of pathways related to adaptive immunity in patients with higher leptin levels across sexes. Strikingly, in the PNF there were differences in opposite directions in female and male specimens, with females showing up-regulated genes significantly enriched in adaptive and humoral immune response gene sets. Similarly, the leptin downstream activation signature in the PNF showed a significant correlation with myeloid associated signatures in both sexes, while humoral responses were only associated to leptin in females.

Conclusions

Higher leptin levels were associated with a modest increase of adaptive immune-related gene expression in the tumors in both males and females. These associations were more robust in the perinephric fat, where both males and females had increased associated myeloid inflammatory signals, but leptin had an association with adaptive and humoral responses only in females. Circulating leptin may be involved in peritumoral immune responses which may link host factors to sex and adiposity-related tumor outcomes. Further studies should aim to address the relationship between leptin activity and specific compartments of the tumor and PNF microenvironment.