Estrogen-receptor-alpha-positive breast and ovarian cancer: Therapy and mechanisms

Wang, Lawrence

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https://hdl.handle.net/2142/127278 Copy

Description

Title

Estrogen-receptor-alpha-positive breast and ovarian cancer: Therapy and mechanisms

Author(s)

Wang, Lawrence

Issue Date

2024-12-06

Director of Research (if dissertation) or Advisor (if thesis)

Shapiro, David J

Doctoral Committee Chair(s)

Shapiro, David J

Committee Member(s)

• Katzenellenbogen, Benita S
• Nelson, Erik R
• Procko, Erik

Department of Study

Biochemistry

Discipline

Biochemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Estrogen Receptor
• Breast Cancer
• Ovarian Cancer
• Unfolded Protein Response
• Myc
• Src
• ErSO

Abstract

Metastatic estrogen receptor α (ERα)-positive breast and ovarian cancer are presently incurable. The objective of these studies was to explore the mechanism of action and evaluate the effectiveness of a new therapy for these challenging cancers. An important mechanism associated with metastatic breast cancer seen in approximately 30% of patients is ERα mutations. The presence of these mutations is associated with endocrine therapy resistance and reduced survival. We therefore explored both the pathways associated with proliferation and metastases of these mutant cells and their sensitivity to therapy. Consistent with their constitutive proliferation, T47D and MCF7 mutant cells with wild-type ERα replaced by the most common mutations, ERαY537S and ERαD538G, exhibit partially estrogen-independent gene expression. A novel invasion/dissociation/rebinding assay demonstrated that the mutant cells have a higher tendency to dissociate from invasion sites and rebind to a second site. In vivo work confirmed these findings: All mice harboring primary breast tumors expressing ERαY537S and ERαD538G developed lung metastases, whereas mice whose tumors expressed with wild-type ERα (T47D) did not show lung metastases. Gene set enrichment analysis showed Myc target pathways are highly induced in the mutant cells. Knockdown and virus transduction showed Myc is necessary and sufficient for ligand-independent proliferation of the mutant cells but had no effect on metastasis-related phenotypes. We then explored the pathway that our preclinical small molecule biomodulator BHPI uses to induce death of these cancer cells. In the recently characterized anticipatory unfolded protein response (a-UPR), receptor-bound estrogen, progesterone, and other mitogenic hormones rapidly elicit phosphorylation of phospholipase C γ (PLCγ), thereby activating the anticipatory UPR. However, how estrogen and progesterone activating their receptors couples to PLCγ phosphorylation and anticipatory UPR activation was unknown. The proto-oncogene c-Src is a non-receptor tyrosine kinase with critical roles in signaling pathways involved in cancer cell proliferation, survival, angiogenesis, and metastasis. To probe Src's role, we used BHPI, which kills cancer cells by inducing the lethal hyperactivation of the a-UPR. Src knockdown or inhibition partially blocked BHPI-mediated anticipatory UPR activation. After unbiased long-term selection for BHPI-resistant human breast cancer cells, 4/11 BHPI-resistant T47D clones, and nearly all MCF-7 clones, exhibited reduced levels of normally growth-stimulating Src. Notably, Src overexpression via viral transduction restored BHPI sensitivity in these cells. Furthermore, knockdown of Src, strongly blocked BHPI-mediated UPR activation and subsequent necrotic cell death in wild type cells. Next, we evaluated the effectiveness of a second-generation BHPI relative, ErSO, in cell culture and in mouse xenograft models. ErSO activated the a-UPR and killed ErαY537S and ERαD538G in cell culture. In multiple orthotopic models, ErSO treatment administered orally or intraperitoneally for 14 or 21 days induced tumor regression without recurrence of lung, bone and liver metastasis and near-complete regression of normally highly lethal brain metastases. Tumors that did recur remained sensitive to retreatment with ErSO. ErSO was well tolerated in mice, rats, and dogs at doses above those needed for therapeutic responses and had little or no effect on normal ERα-expressing murine tissues. ErSO mediated its robust anticancer effects through activation of the anticipatory UPR, suggesting that general activation of a normally tumor protective pathway can induce tumor regression. We then evaluated ErSO in ovarian cancer, which has few targeted therapies and a five-year survival rate below 50%. Most ovarian tumors are ERα-positive. In mouse xenografts, injected ErSO induced rapid and complete, or near-complete, regression of orthotopic metastatic PEO4 tumors and of Caov-3 ovarian tumors. Ovarian cancer patients with metastatic disease often develop malignant ascites. The ascites contains clumps, or organoids, of ovarian cancer cells that drive metastasis. ErSO showed activity against 7/7 fresh patient derived ascites organoids (PDAOs). Low nanomolar ErSO destroyed 2/7 PDAOs. Taken together, these studies suggest ErSO has unusual potential for treatment of advanced ERα-positive breast and ovarian cancers. These studies advance our mechanistic understanding of the aggressive nature of breast cancers containing ERα mutations and of the pathway that the biomodulators first-generation BHPI, and second-generation ErSO, use to induce death of breast and ovarian cancer cells cells. In xenograft models of primary and metastatic breast and ovarian cancer, and in fresh ovarian cancer patient derived ascites organoids, ErSO demonstrated remarkable effectiveness. Thus, ErSO has impressive potential for treatment of therapeutically challenging breast and ovarian cancers.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127278

Copyright and License Information

Copyright 2024 Lawrence Wang

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