Development of New Agents for Treating Endocrine-Resistant Breast Cancer
Abstract
Estrogen receptor alpha (ER) is expressed in approx. 70 percent of all human breast cancers and, therefore, is a major therapeutic target for endocrine therapy. The lack of response to anti-estrogens is a hallmark of resistance to endocrine therapies, yet the mechanisms are not completely understood. One emerging mechanism is the development of mutations in ESR1, the gene encoding ER(alpha). These mutant ER(alpha) proteins confer significantly higher ER(alpha) activity than the wild-type receptor and are resistant to degradation by selective estrogen receptor degraders (SERDs) such as faslodex. Our laboratory discovered a natural plant product, Diptoindonesin G (Dip G), that significantly decreases ER levels. We determined that Dip G functions via Hsp90(alpha)/CHIP, yet the mechanism is different from that of the Hsp90(alpha) ATPase inhibitor 17-AAG. Dip G is more effective than faslodex in inhibiting growth of ER(alpha) mutant cell lines, with the levels of degradation of ER(alpha), inhibition of ER(alpha) target genes and inhibition of cell proliferation all being concordant. Moreover, we have shown that Dip G can effectively inhibit the growth of human tumor organoids. This application will test the hypothesis that Dip G alone or Dip G in combination with SERDs are effective to treat hormone-resistant breast cancers, including those harboring the ESR1 mutations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2023
- Accession Number
- AD1201602
Entities
People
- Shunqiang Li
Organizations
- Washington University in St. Louis