Abstract A035: An analysis of the contribution of the glutathione and thioredoxin antioxidant pathways to triple negative breast cancer development
Authors: Girnius Nomeda , Henstridge Aylin Z , Silvestri Francesca , Li Carman Man Chung , Brugge Joan S 
Published: February 2024

Abstract
The accumulation of reactive oxygen species (ROS), also known as oxidative stress, occurs during tumorigenesis, for example because of changes in cell metabolism or in a cell’s microenvironment. Since elevated ROS can cause senescence or cell death, cells with increased ROS-buffering capacity are selected for during tumor initiation and progression. It is unknown, however, at which stage during carcinogenesis oxidative stress develops, which oxidative response programs are engaged, and whether there is a spatial distribution of oxidative stress within the tissue. Our lab developed a murineTrp53loxp/loxp Brca1loxp/loxp model of triple negative breast cancer (TNBC) that histologically recapitulates the disease progression of human, progressing from normal epithelium, to abnormal proliferation, before advancing to adenocarcinoma. We are applying cyclic immunofluorescence and spatial transcriptomics to study relevant antioxidant pathways in situ. These studies are complemented by analyses of previously published scRNAseq datasets from similar models. Our initial observations have shown that antioxidant expression peaks at a stage of tumorigenesis prior to frank tumor formation, suggesting that nascent tumor cells must overcome oxidative stress to progress. Inhibition of a key antioxidant pathway, the glutathione pathway, did not significantly decrease the Trp53-/- Brca1-/- cell population, and preliminary spatial transcriptomics data do not support an induction of the major players of this pathway during tumorigenesis. A closer examination of the expression patterns of these genes within the mammary gland demonstrates that they are not expressed in the cell of origin of TNBC. In contrast, members of the thioredoxin (TXN) pathway are expressed in the precursor cells of TNBC. One member of the TXN pathway, Txnrd1, is upregulated in Trp53-/- Brca1-/- glands, but not contralateral control glands. This upregulation occurs around the time of epithelial cell expansion post tumor suppressor loss. Furthermore, glutathione pathway inhibition drives Txnrd1 protein expression up in the mutant, but not wildtype glands. Together, our data support an important role for the thioredoxin pathway in reducing oxidative stress during tumorigenesis. Ongoing work aims to assess whether the thioredoxin pathway may represent a viable treatment option to prevent or slow the development of breast cancer in the Trp53/Brca1-deficient background. Insights into vulnerabilities of Brca1-deficient cells may provide BRCA1 germline mutation carriers new approaches for cancer prevention that have otherwise been limited to mastectomy and oophorectomy.
Citation Format: Nomeda Girnius, Aylin Z Henstridge, Francesca Silvestri, Carman Man Chung Li, Joan S Brugge. An analysis of the contribution of the glutathione and thioredoxin antioxidant pathways to triple negative breast cancer development [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A035.