Trim24 Promotes Mammary Tumor Development By Upregulating Metabolic Reducing Power

<p>Metabolic reprograming is an emerging hallmark of cancer cells. Changes in cellular metabolism can contribute to cancer cell survival and tumor progression. Tripartite motif-containing protein 24 (TRIM24) is an E3 ligase for p53, a nuclear receptor co-regulator, and a histone reader. Over expression of TRIM24 correlates with poor overall survival of breast cancer patients. Previously, our lab created a mouse model that conditionally over-expresses (COE) TRIM24 protein in mammary epithelia (<em>Trim24</em>^COE) and develops carcinosarcoma or metaplastic mammary tumors (70% of all <em>Trim24</em>^COE tumors), a rare and aggressive triple-negative subtype called metaplastic TNBC in humans (MpBC). RNA-sequencing revealed that <em>Trim24</em>^COE mouse mammary tumors have upregulated glycolysis and epithelial-to-mesenchymal transition (EMT). <em>Trim24</em>^COE carcinosarcoma cell-derived spheroids showed irregular, poorly differentiated structures that were more invasive compared to spontaneous, control MMTV-cre mammary tumor-derived spheroids. Using ¹³C₆-glucose/glutamine tracing, we found <em>Trim24</em>^COE spheroids recapitulated some of the metabolic features of <em>Trim24</em>^COE carcinosarcomas like upregulated glycolysis and exhibited aberrantly upregulated antioxidant defenses. We found <em>Trim24</em>^COE spheroids exhibited low intracellular and mitochondrial ROS, an increased NADP(H) pool, and were more resistant to oxidative stress. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) and immunoblotting validated that enzymes of one-carbon metabolism and <em>de novo </em>glutathione synthesis pathways were upregulated in <em>Trim24</em>^COE spheroids and that upregulation was depended on TRIM24 over expression. NRF2 is a key regulator of cellular antioxidant response and often found over expressed in many different types of cancers. <em>Nrf2</em> mRNA level and NRF2 protein expression were both upregulated in the <em>Trim24</em>^COE spheroids and knocking down TRIM24 significantly decreased <em>Nrf2</em> expression as well as NRF2-regulated gene expression. Metabolic inhibitors that target enzymes in one-carbon metabolism and <em>de novo </em>glutathione synthesis effectively decreased <em>Trim24</em>^COE spheroids viability. The effect of PHGDH inhibitor CBR5884, GLS inhibitors CB839, and GCLC inhibitor was enhanced with TRIM24 knock-down, indicating that TRIM24 plays a critical role in oxidation-reduction (REDOX)-related cell survival.</p> <p>Here, with metabolomic studies, we uncovered the potential metabolic vulnerabilities in <em>Trim24</em>^COE MpBC spheroids. TRIM24 over expression led to upregulated production of reducing equivalents which further reduce oxidative stress and increase antioxidant defense in <em>Trim24</em>^COE spheroids. Targeting TRIM24 and the corresponding metabolic enzymes in combination could shed light on potential strategies for inhibiting tumor progression of TRIM24-overexpressing MpBC. The work described here supports further investigations of these pathways in MpBC, for which no targeted therapies exist.</p>

Name thesis:degree_name

Masters of Science (MS)

Level thesis:degree_level

Thesis (MS)

Year dc:date.available

2021

Authors dc:creator

• Miao, Shucheng
• <p>https://orcid.org/0000-0002-7306-0966</p>

Contributors dc:contributor

• Michelle Barton and Guillermina Lozano
• Powel Brown
• Went Li

• metaplastic breast cancer
• metabolism
• ROS
• redox
• NADPH
• Medicine and Health Sciences

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/1131

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-2189