The transcription factor Foxp3 is involved in the differentiation, function and survival of CD4+CD25+ regulatory T (T(reg)) cells. Details of the mechanism underlying the induction of Foxp3 expression remain unknown, because studies of the transcriptional regulation of the Foxp3 gene are limited by the small number of T(reg) cells in mononuclear cell populations. Here we have generated a model system for analyzing Foxp3 induction and, by using this system with primary T cells, we have identified an enhancer element in this gene. The transcription factors Smad3 and NFAT are required for activity of this Foxp3 enhancer, and both factors are essential for histone acetylation in the enhancer region and induction of Foxp3. These biochemical properties that define Foxp3 expression explain many of the effects of transforming growth factor-beta on the function of Foxp3+ T(reg) cells.

APC gene mutations play an important role in the initiation step of colorectal carcinogenesis in both familial adenomatous polyposis (FAP) patients and non-FAP patients. Although the APC gene is expressed in most tissues, including the lung, liver, kidney, and mammary gland, its somatic mutations have rarely been found in primary tumors affecting these organs. We have developed a sensitive yeast-based assay for screening almost the entire coding region of the APC gene. By this method, we have been able to detect somatic mutations of the APC gene in 57% of colorectal cancers and none in non-small cell lung cancers. Interestingly, the assay detected somatic APC gene mutations in 18% of breast cancers, in which APC gene mutation was previously considered rare. In the breast cancers, most of the APC mutations were distributed outside the mutation cluster region that has been advocated for colorectal cancers. We also noted a difference in the mutation pattern of the APC between colorectal and breast cancers. In colorectal cancers, all base substitutions were observed at C residues (5 of 5), whereas in breast cancers the majority of them were found at G residues (4 of 5). Furthermore, APC mutations were observed at a significantly high frequency in advanced stages of primary breast cancers (TNM classification, P < 0.05; T category, P < 0.01). Our data suggest that the etiology of the APC mutations and their biological role in carcinogenesis may differ between colorectal and breast cancers.

Homeobox-containing genes are expressed in spatiotemporal fashion during embryogenesis and act as master transcription-regulating factors which control the expression of a variety of genes involved in morphogenesis. They are also expressed in a tissue-specific manner in normal adult tissues and appear to give cells spatial information in the maintenance of their architectural integrity. We transfected a HOXD3 class I homeobox-containing gene into human lung cancer A549 cells and investigated alterations in gene expressions and phenotypes related to the maintenance of tissue architecture in HOXD3-overexpressing A549 cells. In the HOXD3-overexpressing cell lines, expression of E-cadherin was lost and plakoglobin was strongly repressed, whereas integrin ␣3 and ␤3 were up-regulated and N-cadherin and integrin ␣4 were newly expressed. Compared with parental and control transfectant lines, the HOXD3-overexpressing cell lines showed highly motile and invasive activity. Blocking experiments using anti-integrin ␤1 and ␤3 suggested that the increased haptotaxis of the HOXD3-overexpressing cells to vitronectin resulted from increased expression and activation of integrin ␣v␤3, and that overexpression of the HOXD3 gene converted the integrin ␤1-dependent haptotaxis to fibronectin into both integrin ␤1-and ␤3-dependent one. HOXD3 overexpression increased production of matrix-degrative enzymes including matrix metalloproteinase-2 and urokinase-plasminogen activator. When the tumor cells were intravenously injected into the tail veins of nude mice, HOXD3 transfectants formed a significantly large number of metastatic foci in lungs compared with the control transfectants. These findings suggest that HOXD3 can act as a metastasis-promoting gene in human lung cancer A549 cells.

BACKGROUNDβ‐Catenin has been shown to function as a Wnt signaling molecule to stimulate cyclin D1 expression and cell growth in several kinds of tumors.METHODSThe authors immunohistochemically examined specimens of 217 surgically resected primary nonsmall cell lung carcinomas (NSCLCs) for β‐catenin expression and classified them semiquantitatively into three categories, including those with high, moderate, and low scores of expression.RESULTSHigh, moderate, and low scores of expression were found in 37 (17.1%), 145 (66.8%), and 35 (16.1%) tumors, respectively. β‐Catenin expression was not correlated with cyclin D1 expression, but was positively correlated with the Ki‐67 cell growth fraction (P = 0.04). The direct sequencing analysis for the β‐catenin gene mutation of 13 specimens of 217 tumors for the current study revealed no mutations. The relation between survival and β‐catenin expression was evaluated in 148 potentially curatively resected tumors with pathologic Stages I–IIIA. A trend toward better survival was found in patients with tumors having higher scores. In multivariate analysis, high β‐catenin expression was a significant and independent favorable prognostic factor (hazards ratio, 0.31; P = 0.007) as was pathologic stage. Analyzed by cell type, in nonsquamous cell carcinomas, patients with tumors having high scores survived a significantly longer time than those with tumors having moderate or low scores (5‐year survival rates, 84%, 55%, and 32%, respectively; P = 0.02), and high β‐catenin expression tended to be a favorable prognostic factor (hazards ratio, 0.32; P = 0.052).CONCLUSIONSThese results indicate that, in NSCLCs, increased expression of β‐catenin can predict favorable prognosis of patients with resected tumors, suggesting that accumulation of β‐catenin has no or little oncogenic effect via activation of the Wnt pathway, unlike in colon carcinomas or hepatomas. Cancer 2002;94:752–8. © 2002 American Cancer Society.DOI 10.1002/cncr.10213

Our recent studies have identified dynamic protein ensembles containing forkhead box protein 3 (FOXP3) that provide insight into the molecular complexity of suppressor T-cell activities, and it is our goal to determine how these ensembles regulate FOXP3's transcriptional activity in vivo. In this review, we summarize our current understanding of how FOXP3 expression is induced and how FOXP3 functions in vivo as a transcriptional regulator by assembling a multisubunit complex involved in histone modification as well as chromatin remodeling.