Reprogramming SREBP1-dependent lipogenesis and inflammation in high-risk breast with licochalcone A: a novel path to cancer prevention

Abstract

Several anti-estrogen drugs are proven to reduce breast cancer risk, but have had minimal acceptance and impact, due to their side effects. Additionally, these do not reduce the risk of estrogen receptor negative breast cancer. Candidate drugs that are under investigation for this purpose have unfavorable tolerability and safety profiles. Licochalcone A (LicA) from licorice is a prenylated chalcone which has antioxidant and anti-inflammatory effects, suppresses aromatase expression and activity, and reduces estrogen genotoxic metabolism in vivo. We evaluated its breast cancer preventive potential using microstructures obtained from mastectomy specimens of high-risk postmenopausal women. We treated these ex-vivo with LicA, followed by total RNA sequencing, differential gene expression and pathway analysis, followed by metabolic flux modeling. We observed profound downregulation of SREBF-dependent cholesterol biosynthesis, lipid metabolism, and PI3K-Akt pathways, along with significant upregulation of NRF2-dependent antioxidant and anti NF-kB-dependent inflammatory pathways. Additionally, NAD(P)H regenerating pentose phosphate shunt which supports these defense mechanisms was upregulated, in a direction unfavorable to nucleotide biosynthesis and proliferation. Drug matrix analysis of LicA-treated samples revealed significant transcriptomic similarities with statins. NanoString metabolism panel evaluations in microstructures from additional subjects confirmed these findings. Live cell imaging on 2 pre-malignant and 5 malignant breast cell lines treated with single and repeated doses of LicA showed antiproliferation, consistent with the downregulation of proliferative markers (SP1 and KLF4). Western blot analysis demonstrated suppression of SREBP1 in ER+ and ER- malignant breast cells and suppression of p-PI3K and p-AKT in cancer cells suggesting associations with antiproliferative efficacy of LicA. In vivo studies with subcutaneous LicA showed significant suppression of both luminal and triple negative xenografts in mice. Our data suggest that LicA reprograms metabolism and antioxidant responses, and is a promising candidate for further studies as a breast cancer risk reducing agent. Future studies with oral LicA in models of breast cancer prevention are warranted.