CCN6 Knockdown Disrupts Acinar Organization of Breast Cells in Three-dimensional Cultures through Up-regulation of Type III TGF-β Receptor

AbstractWhile normal cells in the human breast are organized into acinar structures, disruption of the acinar architecture is a hallmark of cancer. In a three-dimensional model of morphogenesis, we show that down-regulation of the matrix-associated tumor suppressor protein CCN6 (WNT1-inducible-signaling pathway protein 3) disrupts breast epithelial cell polarity and organization into acini through up-regulation of the type III transforming growth factor-β receptor (TβRIII or betaglycan). Down-regulation of CCN6 in benign breast cells led to loss of tissue polarity and resulted in cellular disorganization with loss of α6 integrin-rich basement membrane and the basolateral polarity protein E-cadherin. Silencing of TβRIII with shRNA and siRNA rescued the ability of breast epithelial cells to form polarized acinar structures with reduced matrix invasion and restored the correct expression of α6 integrin and E-cadherin. Conversely, CCN6 overexpression in aggressive breast cancer cells reduced TβRIII in vitro and in a xenograft model of CCN6 overexpression. The relevance of our studies to human breast cancer is highlighted by the finding that CCN6 protein levels are inversely associated with TβRIII protein in 64%of invasive breast carcinomas. These results reveal a novel function of the matricellular protein CCN6 and establish a mechanistic link between CCN6 and TβRIII in maintaining acinar organization in the breast

Histone Methyltransferase EZH2 Induces Akt-Dependent Genomic Instability and BRCA1 Inhibition in Breast Cancer

Increased levels of EZH2, a critical regulator of cellular memory, signal the presence of metastasis and poor outcome in breast cancer patients. High levels of EZH2 are associated with nuclear pleomorphism, lack of estrogen receptor expression, and decreased nuclear levels of BRCA1 tumor suppressor protein in invasive breast carcinomas. The mechanism by which EZH2 overexpression promotes the growth of poorly differentiated invasive carcinomas remains to be defined. Here, we show that EZH2 controls the intracellular localization of BRCA1 protein. Conditional doxycycline-induced upregulation of EZH2 in benign mammary epithelial cells results in nuclear export of BRCA1 protein, aberrant mitoses with extra centrosomes, and genomic instability. EZH2 inhibition in CAL51 breast cancer cells induces BRCA1 nuclear localization and rescues defects in ploidy and mitosis. Mechanistically, EZH2 overexpression is sufficient for activation of the phosphoinositide 3-kinase/Akt (PI3K/Akt) pathway specifically through activation of Akt isoform 1. EZH2-induced BRCA1 nuclear export, aneuploidy, and mitotic defects were prevented by treatment with the PI3K inhibitors LY294002 or wortmannin. Targeted inhibition of Akt-1, Akt-2, and Akt-3 isoforms revealed that the EZH2-induced phenotype requires specific activation of Akt-1. The relevance of our studies to human breast cancer is highlighted by the finding that high EZH2 protein levels are associated with upregulated expression of phospho-Akt-1 (Ser473) and decreased nuclear expression of phospho-BRCA1 (Ser1423) in 39% of invasive breast carcinomas. These results enable us to pinpoint one mechanism by which EZH2 regulates BRCA1 expression and genomic stability mediated by the PI3K/Akt-1 pathway.Fil: Gonzalez, Maria E.. University of Michigan; Estados UnidosFil: DuPrie, Matthew L.. University of Michigan; Estados UnidosFil: Krueger, Heather. University of Michigan; Estados UnidosFil: Merajver, Sofia D.. University of Michigan; Estados UnidosFil: Ventura, Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Toy, Kathy A.. University of Michigan; Estados UnidosFil: Kleer, Celina G.. University of Michigan; Estados Unido

Expression of aldehyde dehydrogenase 1 as a marker of mammary stem cells in benign and malignant breast lesions of Ghanaian women

BACKGROUND: Breast cancers that are negative for the estrogen receptor (ER), the progesterone receptor (PR), and the HER2 (human epidermal growth factor receptor 2) marker are more prevalent among African women, and the biologically aggressive nature of these triple‐negative breast cancers (TNBCs) may be attributed to their mammary stem cell features. Little is known about expression of the mammary stem cell marker aldehyde dehydrogenase 1 (ALDH1) in African women. Novel data are reported regarding ALDH1 expression in benign and cancerous breast tissue of Ghanaian women. METHODS: Formalin‐fixed, paraffin‐embedded specimens were transported from the Komfo Anoyke Teaching Hospital in Kumasi, Ghana to the University of Michigan for centralized histopathology study. Expression of ER, PR, HER2, and ALDH1 was assessed by immunohistochemistry. ALDH1 staining was further characterized by its presence in stromal versus epithelial and/or tumor components of tissue. RESULTS: A total of 173 women contributed to this study: 69 with benign breast conditions, mean age 24 years, and 104 with breast cancer, mean age 49 years. The proportion of benign breast conditions expressing stromal ALDH1 (n = 40, 58%) was significantly higher than those with cancer (n = 44, 42.3%) ( P = .043). Among the cancers, TNBC had the highest prevalence of ALDH1 expression, either in stroma or in epithelial cells. More than 2‐fold higher likelihood of ALDH1 expression was observed in TNBC cases compared with other breast cancer subtypes (odds ratio = 2.38, 95% confidence interval 1.03‐5.52, P = .042). CONCLUSIONS: ALDH1 expression was higher in stromal components of benign compared with cancerous lesions. Of the ER‐, PR‐, and HER2‐defined subtypes of breast cancer, expression of ALDH1 was highest in TNBC. Cancer 2013. © 2012 American Cancer Society. Mammary stem cells, as identified by cells expressing the marker aldehyde dehydrogenase 1 (ALDH1), appear to be correlated with malignant transformation and progression of breast tissue into biologically aggressive phenotypes. This study reveals increased expression of ALDH1 in benign and malignant tissue of women from the western sub‐Saharan African nation of Ghana, a population known to have higher frequency of triple‐negative breast cancer, and ALDH1 expression in the malignant specimens was found to be associated with risk of triple‐negative breast cancer.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96403/1/27737_ftp.pd