Sporadic activation of an oxidative stress–dependent NRF2-p53 signaling network in breast epithelial spheroids and premalignancies

Abstract

Breast and mammary epithelial cells experience different local environments during tissue development and tumorigenesis. Microenvironmental heterogeneity gives rise to distinct cell regulatory states whose identity and importance are just beginning to be appreciated. Cellular states diversify when clonal three-dimensional (3D) spheroids are cultured in basement membrane, and one such state is associated with stress tolerance and poor response to anticancer therapeutics. Here, we found that this state was jointly coordinated by the NRF2 and p53 pathways, which were costabilized by spontaneous oxidative stress within 3D cultures. Inhibition of NRF2 or p53 individually disrupted some of the transcripts defining the regulatory state but did not yield a notable phenotype in nontransformed breast epithelial cells. In contrast, combined perturbation prevented 3D growth in an oxidative stress–dependent manner. By integrating systems models of NRF2 and p53 signaling in a single oxidative stress network, we recapitulated these observations and made predictions about oxidative stress profiles during 3D growth. NRF2 and p53 signaling were similarly coordinated in normal breast epithelial tissue and hormone-negative ductal carcinoma in situ lesions but were uncoupled in triple-negative breast cancer (TNBC), a subtype in which p53 is usually mutated. Using the integrated model, we correlated the extent of this uncoupling in TNBC cell lines with the importance of NRF2 in the 3D growth of these cell lines and their predicted handling of oxidative stress. Our results point to an oxidative stress tolerance network that is important for single cells during glandular development and the early stages of breast cancer.

Novel Interplay between p53 and HO-1 in Embryonic Stem Cells

“…The main TF that promotes Hmox1 expression is the nuclear factor erythroid 2-related factor 2 (NRF2), that coordinates the basal and stress-induced activation of several cytoprotective genes, controlling key components of the cellular antioxidant system [ 30 ]. Both NRF2 and p53 regulate the expression of proteins involved in the protection against oxidative stress, and it has been suggested that there is a crosstalk between them [ 31 , 32 ], even though this interplay is not completely understood. Moreover, a link between p53 and NRF2 was described in multiple tumorigenic scenarios like lung and breast cancer [ 33 , 34 ].…”

“…Moreover, a link between p53 and NRF2 was described in multiple tumorigenic scenarios like lung and breast cancer [ 33 , 34 ]. Furthermore, NRF2 deficits are buffered by compensatory increases in p53 signaling, and striking ROS-dependent phenotypes arise when both pathways are perturbed in breast-mammary epithelia [ 32 ]. In the context of stem cells, NRF2 overexpression protects mesenchymal stem cells against cell death caused by oxidative stress and preserves multi-differentiation potential [ 35 ].…”

Insight into the Web of Stress Responses Triggered at Gene Expression Level by Porphyrin-PDT in HT29 Human Colon Carcinoma Cells

“…Moreover, NRF2 links oxidative conditions with DDR through the p21 protein which is encoded by CDKN1A and is mainly involved in cell cycle arrest [ 34 ]. NRF2 can induce the transcription of the CDKN1A gene which is also under the transcriptional control of TP53 [ 77 ]. Through a feed forward loop, enhanced levels of p21 compete with NRF2 for binding to its KEAP1 repressor, hence inducing the activation of the NRF2 pathway [ 78 ].…”

Metabolic Stress Adaptations Underlie Mammary Gland Morphogenesis and Breast Cancer Progression

“…The spatially heterogeneous trigger of JUND cluster genes in MCF10A spheroids is coordinated by two stress-responsive transcription factors NRF2 (nuclear factor erythroid 2 like 2, NFE2L2) and p53 (TP53) [49]. NRF2 and p53 play important roles in oxidative stress handling in normal mammary epithelia.…”

“…In normal breast epithelial tissue and basal-like premalignancy, NRF2-p53 coordination provides an oxidative stress-handling network [49]. NRF2-mediated tolerance in premalignancy may permit the emergency of missense p53 mutations that drive the progression of TNBC.…”