In Silico Discovery of Stapled Peptide Inhibitor Targeting the Nur77-PPARγ Interaction and Its Anti-Breast-Cancer Efficacy

The binding of peroxisome proliferator-activated receptor gamma (PPAR gamma) to the orphan nuclear receptor Nur77 facilitates the ubiquitination and degradation of Nur77, and leads to aberrant fatty acid uptake for breast cancer progression. Because of its crucial role in clinical prognosis, the interaction between Nur77 and PPAR gamma is an attractive target for anti-breast-cancer therapy. However, developing an inhibitor of the Nur77-PPAR gamma interaction poses a technical challenge due to the absence of the crystal structure of PPAR gamma and its corresponding interactive model with Nur77. Here, ST-CY14, a stapled peptide, is identified as a potent modulator of Nur77 with a KD value of 3.247 x 10-8 M by in silico analysis, rational design, and structural modification. ST-CY14 effectively increases Nur77 protein levels by blocking the Nur77-PPAR gamma interaction, thereby inhibiting lipid metabolism in breast tumor cells. Notably, ST-CY14 significantly suppresses breast cancer growth and bone metastasis in mice. The findings demonstrate the feasibility of exploiting directly Nur77-PPAR gamma interaction in breast cancer, and generate what to the best knowledge is the first direct inhibitor of the Nur77-PPAR gamma interaction available for impeding fatty acid uptake and therapeutic development. In silico approaches and chemical modifications are utilized to discover the first peptide inhibitor targeting the Nur77-PPAR gamma interaction in the absence of cocrystal structures for breast cancer therapy. image