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Conditional overexpression of histone reader Tripartite motif containing protein 24 (TRIM24) in mouse mammary epithelia (Trim24COE) drives spontaneous development of mammary carcinosarcoma tumors, lacking ER, PR and HER2. Human carcinosarcomas or metaplastic breast cancers (MpBC) are a rare, chemorefractory subclass of triple-negative breast cancers (TNBC). Comparison of Trim24COE metaplastic carcinosarcoma morphology, TRIM24 protein levels and a derived Trim24COE gene signature reveals strong correlation with human MpBC tumors and MpBC patient-derived xenograft (PDX) models. Global and single-cell tumor profiling reveal Met as a direct oncogenic target of TRIM24, leading to aberrant PI3K/mTOR activation. Here, we find that pharmacological inhibition of these pathways in primary Trim24COE tumor cells and TRIM24-PROTAC treatment of MpBC TNBC PDX tumorspheres decreased cellular viability, suggesting potential in therapeutically targeting TRIM24 and its regulated pathways in TRIM24-expressing TNBC. Human metaplastic breast cancers (MpBC) are a rare, aggressive subclass of triple-negative breast cancers. Here, the authors show over-expression of histone reader TRIM24 is sufficient to generate tumors with a molecular signature of metabolic dysfunction and EMT in a mouse model of human MpBC. [ABSTRACT FROM AUTHOR]

Background The envelope (env) protein of the human endogenous retrovirus type K (HERV-K) family is commonly expressed on the surface of breast cancer cells. We assessed whether HERV-K env is a potential target for antibody-based immunotherapy of breast cancer. Methods We examined the expression of HERV-K env protein in various malignant (MDA-MB-231, MCF-7, SKBR3, MDA-MB-453, T47D, and ZR-75-1) and nonmalignant (MCF-10A and MCF-10AT) human breast cell lines by immunoblot, enzyme-linked immunosorbent assay, immunofluorescence staining, and flow cytometry. Anti-HERV-K env monoclonal antibodies (mAbs; 6H5, 4D1, 4E11, 6E11, and 4E6) were used to target expression of HERV-K, and antitumor effects were assessed by quantifying growth and apoptosis of breast cancer cells in vitro, and tumor growth in vivo in mice (n = 5 per group) bearing xenograft tumors. The mechanisms responsible for 6H5 mAb–mediated effects were investigated by microarray assays, flow cytometry, immunoblot, and immunofluorescence staining. The expression of HERV-K env protein was assessed in primary breast tumors (n = 223) by immunohistochemistry. All statistical tests were two-sided. Results The expression of HERV-K env protein in malignant breast cancer cell lines was substantially higher than nonmalignant breast cells. Anti–HERV-K-specific mAbs inhibited growth and induced apoptosis of breast cancer cells in vitro. Mice treated with 6H5 mAb showed statistically significantly reduced growth of xenograft tumors compared with mice treated with control immunoglobulin (control [mIgG] vs 6H5 mAb, for tumors originating from MDA-MB-231 cells, mean size = 1448.33 vs 475.44 mm3; difference = 972.89 mm3, 95% CI = 470.17 to 1475.61 mm3; P < .001). Several proteins involved in the apoptotic signaling pathways were overexpressed in vitro in 6H5 mAb–treated malignant breast cells compared with mIgG-treated control. HERV-K expression was detected in 148 (66%) of 223 primary breast tumors, and a higher rate of lymph node metastasis was associated with HERV-K-positive compared with HERV-K-negative tumors (43% vs 23%, P = .003). Conclusion Monoclonal antibodies against HERV-K env protein show potential as novel immunotherapeutic agents for breast cancer therapy. [ABSTRACT FROM PUBLISHER]

Female transgenic mice that constitutively overexpress the transcription factor ATF3 in the basal epithelium of the mammary gland develop mammary carcinomas with high frequency, but only if allowed to mate and raise pups early in life. This transgenic mouse model system reproduces some features of human breast cancer in that about 20% of human breast tumor specimens exhibit overexpression of ATF3 in the tumor cells. The ATF3-induced mouse tumors are phenotypically similar to mammary tumors induced by overexpression of activating Wnt/γ-catenin pathway genes. We now show that the Wnt/γ-catenin pathway is indeed activated in ATF3-induced tumors. γ-catenin is transcriptionally up-regulated in the tumors, and high levels of nuclear γ-catenin are seen in tumor cells. A reporter gene for Wnt/γ-catenin pathway activity, TOPGAL, is up-regulated in the tumors and several downstream targets of Wnt signaling, including Ccnd1, Jun, Axin2 and Dkk4, are also expressed at higher levels in ATF3-induced tumors compared to mammary glands of transgenic females. Several positive-acting ligands for this pathway, including Wnt3, Wnt3a, Wnt7b, and Wnt5a, are significantly overexpressed in tumor tissue, and mRNA for Wnt3 is about 5-fold more abundant in transgenic mammary tissue than in non-transgenic mammary tissue. Two known transcriptional targets of ATF3, Snai1 and Snai2, are also overexpressed in the tumors, and Snail and Slug proteins are found to be located primarily in the nuclei of tumor cells. In vitro knockdown of Atf3 expression results in significant decreases in expression of Wnt7b, Tcf7, Snai2 and Jun, suggesting that these genes may be direct transcriptional targets of ATF3 protein. By chromatin immunoprecipitation analysis, both ATF3 and JUN proteins appear to bind to a particular subclass of AP-1 sites upstream of the transcriptional start sites of each of these genes [ABSTRACT FROM AUTHOR]

Egypt shows a parallel increase in premenopausal breast cancer and environmental pollution. The purpose of this study is to explore a possible relationship between oxidative DNA damage, urinary estrogen metabolites and breast cancer in Egyptian premenopausal women. We conducted a pilot study of Egyptian breast cancer involving 29 cases and 32 controls and analysed lymphocyte DNA levels of 7,8-dihydro-8-oxo-2′-deoxyguanine (8-oxo-dG), a measure of oxidative DNA damage using high performance liquid chromatography with electro-chemical detection (HPLC-ECD) method. We analysed levels of urinary estrogen metabolites, 2-hydroxyestrone (2-OHE) and 16α-hydroxyestrone (16α-OHE) by an enzyme immuno assay. We also collected residential, occupational, and reproductive histories of all study subjects. We detected, in all subjects, exceptionally high levels of 8-oxo-dG and thus oxidative DNA damage, the levels (mean 8-oxo-dG/10 5 dG ± SD) were significantly ( P  < 0.01) higher in breast cancer cases (139.4 ± 78.4) than in controls (60.9 ± 51.5). Urinary 2-OHE and 16α-OHE or their ratio was not significantly different between cases and controls. However, 8-oxo-dG levels were positively correlated ( P  < 0.05) with 2-OHE and 16α-OHE from cases while controls showed a negative correlation ( P  < 0.05). Urban residence (Odds Ratio [OR] 3.1; Confidence interval [CI], 1.1 - 9.3), infertility (OR [9.8]; CI [1.1 - 89.7]), age (OR [2.6]; CI [1.4 - 4.6]) and 8-oxo-dG (OR 5.8; CI 1.9 - 17.5) levels were found to be significant predictors of breast cancer. Our finding of exceptionally high levels of 8-oxo-dG, a common result of oxidative DNA damage, warrant future studies on a larger population of premenopausal women in Egypt with consideration of other susceptibility markers and dietary characteristics. [ABSTRACT FROM AUTHOR]

Basal-like breast cancer (BLBC) is an aggressive and deadly subtype of human breast cancer that is highly metastatic, displays stem-cell like features, and has limited treatment options. Therefore, developing and characterizing preclinical mouse models with tumors that resemble BLBC is important for human therapeutic development. ATF3 is a potent oncogene that is aberrantly expressed in most human breast cancers. In the BK5.ATF3 mouse model, overexpression of ATF3 in the basal epithelial cells of the mammary gland produces tumors that are characterized by activation of the Wnt/β-catenin signaling pathway. Here, we used RNA-Seq and microRNA (miRNA) microarrays to better define the molecular features of BK5.ATF3-derived mammary tumors. These analyses showed that these tumors share many characteristics of human BLBC including reduced expression of Rb1, Esr1, and Pgr and increased expression of Erbb2, Egfr, and the genes encoding keratins 5, 6, and 17. An analysis of miRNA expression revealed reduced levels of Mir145 and Mir143, leading to the upregulation of their target genes including both the pluripotency factors Klf4 and Sox2 as well as the cancer stem-cell-related gene Kras. Finally, we show through knock-down experiments that ATF3 may directly modulate MIR145/143 expression. Taken together, our results indicate that the ATF3 mouse mammary tumor model could provide a powerful model to define the molecular mechanisms leading to BLBC, identify the factors that contribute to its aggressiveness, and, ultimately, discover specific genes and gene networks for therapeutic targeting. [ABSTRACT FROM AUTHOR]