Targeting GD3 Synthase (ST8SIA1) in GD2+ Breast Cancer Stem-Like Cells to Prevent Tumor Growth and Metastases in Triple-Negative Breast Cancer
Abstract
Triple-negative breast cancer (TNBC) accounts for about 15% of all breast cancer cases and is the most aggressive and highly metastatic of all breast cancer subtypes. Metastasis is the primary cause of mortality in TNBC patients and is mainly caused by cells in primary tumors called breast cancer stem-like cells (BCSCs). BCSCs are highly tumorigenic, chemotherapy-resistant, and metastatic and cause tumor recurrence. Therefore, BCSC-targeted therapy can be used to complement standard chemotherapy for TNBC. To target BCSCs, molecular markers associated with BCSCs must be identified. We discovered that the ganglioside GD2 is a marker for BCSCs and that the enzyme ST8SIA1 regulates GD2 expression in BCSCs. Knockdown of ST8SIA1 expression reduces the number of GD2+ BCSCs and inhibits TNBC growth and metastasis. In this proposed study, we aim to target ST8SIA1 in TNBC using small-molecule inhibitors developed in our laboratory. We synthesized these compounds and tested them in TNBC cell lines. We found that these compounds inhibited GD2 expression in a concentration-dependent manner, confirming that they inhibit ST8SIA1 enzyme activity in BCSCs. In addition, treatment of TNBC cell lines with ST8SIA1 inhibitors inhibited BCSC function, including mammosphere formation and soft-agar colony formation, in vitro. We will test these compounds alone and in combination with chemotherapeutic agents, such as doxorubicin, to examine their effect on tumor growth and metastasis in patient-derived xenograft models available in our laboratory. Also, we will identify the TNBC subtypes with the best response to ST8SIA1-targeted therapy. TNBC has seven molecular subtypes: basal like-1, basal like-2, mesenchymal, mesenchymal stem-like, immunomodulatory, luminal androgen receptor positive, and uncharacterized. Our preliminary results of The Cancer Genome Atlas data analysis suggested that ST8SIA1 is highly expressed in mesenchymal TNBCs. We will validate these data by analyzing ST8SIA1 protein expression in a set of TNBC tissue microarrays at The University of Texas MD Anderson Cancer Center in collaboration with our industry partner, Insight Genetics. Next, we will investigate the mechanism of tumor initiation and metastasis regulation by ST8SIA1 in TNBC cells. Our preliminary data suggest that mutations of p53 induce ST8SIA1 expression in breast cancer cells. However, the specific mutations of p53 that causes this are not known. Therefore, we will identify the specific p53 mutations that induce ST8SIA1 expression by inducing overexpression of or inhibiting the expression of individual mutated p53 genes in TNBC cell lines. Our preliminary data also suggest that inhibition of ST8SIA1 expression inhibits mitochondrial respiration via upregulation of cytotoxic ceramide expression. Thus, we will also investigate the role of ceramide-induced mitochondrial dysfunction in ST8SIA1 inhibitor-treated TNBC cells. Together, these experiments will determine the role of ST8SIA1 in BCSCs that are drug-resistant and highly metastatic and establish the preclinical rationale for testing ST8SIA1 inhibitors in TNBC treatment. This project will move these inhibitors into the clinic via development of a simple diagnostic assay using immunohistochemical analysis of formalin-fixed, paraffin-embedded TNBC core biopsy samples. This will enable clinicians to identify TNBC patients with ST8SIA overexpression and develop therapeutic strategies to treat TNBC using the ST8SIA1 inhibitors that we will develop in this proposed study. We anticipate identifying novel compounds that can be used as single agents or in combination with chemotherapy to inhibit TNBC growth and metastasis and that can be quickly translated to Phase 1/2 clinical trials in TNBC patients. Finally, we will identify the mechanism of ST8SIA1-mediated regulation of growth and metastasis of TNBC cells using various genetic and molecular approaches with in vitro and in vivo models.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 19, 2019
- Source ID
- W81XWH1910453
Entities
People
- Venkata Battula
Organizations
- The University of Texas MD Anderson Cancer Center
- United States Army