Leptin and insulin synergize with PIK3CA mutation to enhance PD-L1 mediated immunosuppression in thyroid cancer

The incidence of thyroid cancer keeps rising and obesity emerges as an important risk factor for thyroid cancer, but the underlying mechanism is far from clear. Here, we hypothesize that leptin and insulin, two hormones closely related to obesity, may contribute to the pathogenesis of thyroid cancer. By using a combination of assays like CRISPR KO, cancer cell-T cell co-culture, ApoLive-Glo™ multiplex assay and syngeneic mouse model, we show that PD-L1 protein levels are increased dose-dependently by leptin or insulin in multiple thyroid cancer cell lines. Leptin and insulin converge to activate the PI3K-AKT pathway to enhance PD-L1 expression and activity. In addition, we use CRISPR KO to generate human thyroid cancer cells expressing WT PIK3CA or PIK3CA-E545K mutant. PIK3CA- E545K mutation makes the thyroid cancer cells to produce more PD-L1 protein upon leptin or insulin treatment. Thus, leptin and insulin synergize with PIK3CA mutation to enhance PD-L1 expression. Dual blockade of leptin and insulin signaling pathways reduces tumor size in a syngeneic mouse model. Our study suggests that understanding the interaction between genetic mutation and obesity is crucial for comprehensively assessing thyroid cancer risk and developing effective treatment strategies.