Downregulation of IRF8 in Alveolar Macrophages by G-CSF Promotes Metastatic Tumor Progression

Tissue-resident macrophages (TRMs) are abundant immune cells within pre-metastatic sites, yet their functional contributions to metastasis remain incompletely understood. Here, we show that alveolar macrophages (AMs), the main TRMs of the lung, are susceptible to downregulation of the immune stimulatory transcription factor IRF8, impairing anti-metastatic activity in models of metastatic breast cancer. G-CSF is a key tumor-associated factor (TAF) that acts upon AMs to reduce IRF8 levels and facilitate metastasis. Translational relevance of IRF8 downregulation was observed among macrophage precursors in breast cancer and

Estrogen Receptor-Beta2 (ERβ2)–Mutant p53–FOXM1 Axis: A Novel Driver of Proliferation, Chemoresistance, and Disease Progression in High Grade Serous Ovarian Cancer (HGSOC)

High grade serous ovarian cancer (HGSOC) is the most common and lethal subtype of epithelial ovarian cancer. Prevalence (~96%) of mutant p53 is a hallmark of HGSOC. Estrogen receptor-beta (ERβ) has been reported to be another important player in HGSOC, although the pro-versus anti-tumorigenic role of its different isoforms remains unsettled. However, whether there is functional interaction between ERβ and mutant p53 in HGSOC is unknown. ERβ1 and ERβ2 mRNA and protein analysis in HGSOC cell lines demonstrated that ERβ2 is the predominant isoform in HGSOC. Specificity of ERβ2 antibody was ascertained using cells depleted of ERβ2 and ERβ1 separately with isoform-specific siRNAs. ERβ2-mutant p53 interaction in cell lines was confirmed by co-immunoprecipitation and in situ proximity ligation assay (PLA). Expression levels of ERβ2, ERα, p53, and FOXM1 proteins and ERβ2-mutant p53 interaction in patient tumors were determined by immunohistochemistry (IHC) and PLA, respectively. ERβ2 levels correlate positively with FOXM1 levels and negatively with progression-free survival (PFS) and overall survival (OS). Quantitative chromatin immunoprecipitation (qChIP) and mRNA expression analysis revealed that ERβ2 and mutant p53 co-dependently regulated FOXM1 gene transcription. The combination of ERβ2-specific siRNA and PRIMA-1MET that converts mutant p53 to wild type conformation increased apoptosis. Our work provides the first evidence for a novel ERβ2-mutant p53-FOXM1 axis that can be exploited for new therapeutic strategies against HGSOC

TP53 status as a determinant of pro- versus anti-tumorigenic effects of estrogen receptor-beta in breast cancer

BACKGROUND: Anti-tumorigenic versus pro-tumorigenic roles of estrogen receptor-beta (ESR2) in breast cancer (BC) remain unsettled. We investigated the potential of TP53 status to be a determinant of the bi-faceted role of ESR2 and associated therapeutic implications for triple negative BC (TNBC). METHODS: ESR2-TP53 interaction was analyzed with multiple assays including in situ proximity ligation assay (PLA). Transcriptional effects on TP53-target genes and cell proliferation in response to knocking down or overexpressing ESR2 were determined. Patient survival according to ESR2 expression levels and TP53 mutation status was analyzed in the Basal-like/ TNBC subgroup in METABRIC (n = 308) and Roswell (n = 46) patient cohorts by univariate Cox regression and log-rank test. All statistical tests are two-sided. RESULTS: ESR2 interaction with WT and mutant TP53 caused pro-proliferative and anti-proliferative effects, respectively. Depleting ESR2 in cells expressing WT TP53 resulted in increased expression of TP53-target genes CDKN1A (control group mean = 1 [SD = 0.13] vs ESR2 depletion group mean =2.08 [SD = 0.24]; p=.003) and BBC3 (control group mean = 1 [SD = 0.06] vs ESR2 depleted group mean =1.92 [SD = 0.25]; p=.003); however expression of CDKN1A (control group mean = 1 [SD = 0.21] vs ESR2 depleted group mean =0.56 [SD = 0.12];p=.02) and BBC3 (control group mean = 1 [SD = 0.03] vs ESR2 depleted group mean =0.55 [SD = 0.09]; p = .008) was decreased in cells expressing mutant TP53. Overexpressing ESR2 had opposite effects. Tamoxifen increased ESR2-mutant TP53 interaction leading to reactivation of TP73 and apoptosis. High levels of ESR2 expression in mutant TP53- expressing Basal-like tumors is associated with better prognosis (METABRIC cohort: log-rank p = 0.001; HR = 0.26, 95% Confidence interval= 0.08 to 0.84, univariate Cox p = 0.02). CONCLUSIONS: TP53 status is a determinant of the functional duality of ESR2. Our study suggests that ESR2-mutant TP53 combination prognosticates survival in TNBC revealing a novel strategy to stratify TNBC for therapeutic intervention potentially by repurposing tamoxifen

ESR1 and p53 interactome alteration defines mechanisms of tamoxifen response in luminal breast cancer

Summary: The canonical mechanism behind tamoxifen’s therapeutic effect on estrogen receptor α/ESR1+ breast cancers is inhibition of ESR1-dependent estrogen signaling. Although ESR1+ tumors expressing wild-type p53 were reported to be more responsive to tamoxifen (Tam) therapy, p53 has not been factored into choice of this therapy and the mechanism underlying the role of p53 in Tam response remains unclear. In a window-of-opportunity trial on patients with newly diagnosed stage I–III ESR1+/HER2/wild-type p53 breast cancer who were randomized to arms with or without Tam prior to surgery, we reveal that the ESR1-p53 interaction in tumors was inhibited by Tam. This resulted in functional reactivation of p53 leading to transcriptional reprogramming that favors tumor-suppressive signaling, as well as downregulation of oncogenic pathways. These findings illustrating the convergence of ESR1 and p53 signaling during Tam therapy enrich mechanistic understanding of the impact of p53 on the response to Tam therapy

Downregulation of IRF8 in alveolar macrophages by G-CSF promotes metastatic tumor progression

Summary: Tissue-resident macrophages (TRMs) are abundant immune cells within pre-metastatic sites, yet their functional contributions to metastasis remain incompletely understood. Here, we show that alveolar macrophages (AMs), the main TRMs of the lung, are susceptible to downregulation of the immune stimulatory transcription factor IRF8, impairing anti-metastatic activity in models of metastatic breast cancer. G-CSF is a key tumor-associated factor (TAF) that acts upon AMs to reduce IRF8 levels and facilitate metastasis. Translational relevance of IRF8 downregulation was observed among macrophage precursors in breast cancer and a CD68hiIRF8loG-CSFhi gene signature suggests poorer prognosis in triple-negative breast cancer (TNBC), a G-CSF-expressing subtype. Our data highlight the underappreciated, pro-metastatic roles of AMs in response to G-CSF and identify the contribution of IRF8-deficient AMs to metastatic burden. AMs are an attractive target of local neoadjuvant G-CSF blockade to recover anti-metastatic activity