FOXA1: a transcription factor with parallel functions in development and cancer

When aberrant, factors critical for organ morphogenesis are also commonly involved in disease progression. FOXA1 (forkhead box A1), also known as HNF3α (hepatocyte nuclear factor 3α), is required for postnatal survival due to its essential role in controlling pancreatic and renal function. In addition to regulating a variety of tissues during embryogenesis and early life, rescue experiments have revealed a specific role for FOXA1 in the postnatal development of the mammary gland and prostate. Activity of the nuclear hormone receptors ERα (oestrogen receptor α) and AR (androgen receptor) is also required for proper development of the mammary gland and prostate respectively. FOXA1 modulates ER and AR function in breast and prostate cancer cells, supporting the postulate that FOXA1 is involved in ER and AR signalling under normal conditions, and that some carcinogenic processes in these tissues stem from hormonally regulated developmental pathways gone awry. In addition to broadly reviewing the function of FOXA1 in various aspects of development and cancer, this review focuses on the interplay of FOXA1/ER and FOXA1/AR, in normal and cancerous mammary and prostate epithelial cells. Given the hormone dependency of both breast and prostate cancer, a thorough understanding of FOXA1's role in both cancer types is critical for battling hormone receptor-positive disease and acquired anti-hormone resistance.     

Phosphorylation by p38 mitogen-activated protein kinase promotes estrogen receptor α turnover and functional activity via the SCF(Skp2) proteasomal complex

The nuclear hormone receptor estrogen receptor α (ERα) mediates the actions of estrogens in target cells and is a master regulator of the gene expression and proliferative programs of breast cancer cells. The presence of ERα in breast cancer cells is crucial for the effectiveness of endocrine therapies, and its loss is a hallmark of endocrine-insensitive breast tumors. However, the molecular mechanisms underlying the regulation of the cellular levels of ERα are not fully understood. Our findings reveal a unique cellular pathway involving the p38 mitogen-activated protein kinase (p38MAPK)-mediated phosphorylation of ERα at Ser-294 that specifies its turnover by the SCF(Skp2) proteasome complex. Consistently, we observed an inverse relationship between ERα and Skp2 or active p38MAPK in breast cancer cell lines and human tumors. ERα regulation by Skp2 was cell cycle stage dependent and critical for promoting the mitogenic effects of estradiol via ERα. Interestingly, by the knockdown of Skp2 or the inhibition of p38MAPK, we restored functional ERα protein levels and the control of gene expression and proliferation by estrogen and antiestrogen in ERα-negative breast cancer cells. Our findings highlight a novel pathway with therapeutic potential for restoring ERα and the responsiveness to endocrine therapy in some endocrine-insensitive ERα-negative breast cancers.     

Estradiol-dependent regulation of angiopoietin expression in breast cancer cells

Angiopoietin-1 (Ang-1) is a ligand for Tie-2 receptors and a promoter of angiogenesis. Angiogenesis plays an important role in breast cancer, as it is one of the critical events required for tumors to grow and metastasize. In this study, we investigated the influence of estradiol (E2) on the expression of angiopoietins in breast cancer cell lines. Ang-1 mRNA and protein expressions were significantly higher in estrogen receptor-negative (ERα-) breast cancer cells than in estrogen receptor-positive (ERα+) cells. Exposure of ERα+ cells to E2 resulted in further reductions of Ang-1 levels. In mouse mammary pads inoculated with breast cancer cells, both tumor size and Ang-1 production were significantly lower in ERα+ cell-derived xenografts, as compared to those derived from ERα- cells. Reduction of circulating levels of E2 by ovariectomy eliminated this response. Overall, these results indicate that Ang-1 mRNA and protein expressions: (1) negatively correlate with the level of ERα in breast cancer cell lines; (2) are downregulated by E2 in an ERα dependent manner; and (3) positively correlate with the degree of angiogenesis in vivo. We conclude that Ang-1 is an important modulator of growth and progression of ERα- breast cancers.     

CHAF1A和ERα在宫颈鳞状细胞癌中的表达和临床意义

该研究探讨染色质组装因子1亚基(CHAF1A)和雌激素受体1(ERα)在宫颈鳞状细胞癌(CSCC)组织中的表达,探究CHAF1A和ERα的关系及其对CSCC潜在的临床意义,采用了免疫组织化学染色法检测CHAF1A和ERα在CSCC组织及对应的癌旁组织中的表达情况;从CSCC组织及对应癌旁组织中提取总RNA,RT-PCR检测其mRNA水平,分析其相关性;免疫印迹实验检测CHAF1A和ERα在HeLa、C33a、CaSki、Siha和HaCat细胞中的表达差异;慢病毒介导的ShRNA敲低CHAF1A mRNA的表达,RT-PCR检测CHAF1A基因敲低后对ERα表达的影响。结果显示,CHAF1A的表达随着CSCC病变的进展升高,在宫颈癌组织中的表达显著高于其对应的癌旁组织,在宫颈癌细胞株中的表达亦高于人正常表皮细胞系;ERα的表达随着CSCC病变的进展降低,在宫颈癌组织及细胞系中的表达趋势则与CHAF1A相反。CHAF1A基因敲低后ERαmRNA表达升高;另外,统计分析利用χ2检验、Spearman检验及Student’s t检验,探索CHAF1A和ERα表达与CSCC临床病理特征的关系。得出结论,CHAF1A在宫颈癌中高表达并与CSCC恶性程度呈正相关性;ERα在宫颈癌中低表达且与CSCC恶性程度呈负相关性;CHAF1A的表达与ERα的表达呈负相关性;CHAF1A可能对ERα的表达具有调控作用。