技术资料

Prostate cancer (PCa) contains a small population of cancer stem cells (CSCs) that contribute to its initiation and progression. The development of specific markers for identification of the CSCs may lead to new diagnostic strategies of PCa. Increased aldehyde dehydrogenase 1A1 (ALDH1A1) activity has been found in the stem cell populations of leukemia and some solid tumors. The aim of the study was to investigate the stem-cell-related function and clinical significance of the ALDH1A1 in human PCa. ALDEFLUOR assay was used to isolate ALDH1A1(+) cells from PCa cell lines. Stem cell characteristics of the ALDH1A1(+) cells were then investigated by in vitro and in vivo approaches. The ALDH1A1 expression was also analyzed by immunohistochemistry in 18 normal prostate and 163 PCa tissues. The ALDH1A1(+) PCa cells showed high clonogenic and tumorigenic capacities,and serially reinitiated transplantable tumors that resembled histopathologic characteristics and heterogeneity of the parental PCa cells in mice. Immunohistochemical analysis of human prostate tissues showed that ALDH1A1(+) cells were sparse and limited to the basal component in normal prostates. However,in tumor specimens,increased ALDH1A1 immunopositivity was found not only in secretory type cancer epithelial cells but also in neuroendocrine tumor populations. Furthermore,the high ALDH1A1 expression in PCa was positively correlated with Gleason score (P=0.01) and pathologic stage (P=0.01),and inversely associated with overall survival and cancer-specific survival of the patients (P=0.00093 and 0.00017,respectively). ALDH1A1 could be a prostate CSC-related marker. Measuring its expression might provide a potential approach to study tumorigenesis of PCa and predict outcome of the disease. View Publication

NOTCH signaling is critical for specifying the intestinal epithelial cell lineage and for initiating colorectal adenomas and colorectal cancers (CRC). Based on evidence that NOTCH is important for the maintenance and self-renewal of cancer-initiating cells in other malignancies,we studied the role of NOTCH signaling in colon cancer-initiating cells (CCIC). Tumors formed by CCICs maintain many properties of the primary CRCs from which they were derived,such as glandular organization,cell polarity,gap junctions,and expression of characteristic CRC molecular markers. Furthermore,CCICs have the property of self-renewal. In this study,we show that NOTCH signaling is 10- to 30-fold higher in CCIC compared with widely used colon cancer cell lines. Using small-molecule inhibition and short hairpin RNA knockdown,we show that NOTCH prevents CCIC apoptosis through repression of cell cycle kinase inhibitor p27 and transcription factor ATOH1. NOTCH is also critical to intrinsic maintenance of CCIC self-renewal and the repression of secretory cell lineage differentiation genes such as MUC2. Our findings describe a novel human cell system to study NOTCH signaling in CRC tumor initiation and suggest that inhibition of NOTCH signaling may improve CRC chemoprevention and chemotherapy. View Publication

Pilocytic astrocytoma is commonly viewed as a benign lesion. However,disease onset is most prevalent in the first two decades of life,and children are often left with residual or recurrent disease and significant morbidity. The Hedgehog (Hh) pathway regulates the growth of higher WHO grade gliomas,and in this study,we have evaluated the activation and operational status of this regulatory pathway in pilocytic astrocytomas. Expression levels of the Hh pathway transcriptional target PTCH were elevated in 45% of tumor specimens analyzed (ages 1-22 years) and correlated inversely with patient age. Evaluation of a tissue array revealed oligodendroglioma-like features,pilomyxoid features,infiltration,and necrosis more commonly in specimens from younger patients (below the median patient age of 10 years). Immunohistochemical staining for the Hh pathway components PTCH and GLI1 and the proliferation marker Ki67 demonstrated that patients diagnosed before the age of 10 had higher staining indices than those diagnosed after the age of 10. A significant correlation between Ki67 and PTCH and GLI1 staining indices was measured,and 86% of Ki67-positive cells also expressed PTCH. The operational status of the Hh pathway was confirmed in primary cell culture and could be modulated in a manner consistent with a ligand-dependent mechanism. Taken together,these findings suggest that Hh pathway activation is common in pediatric pilocytic astrocytomas and may be associated with younger age at diagnosis and tumor growth. View Publication

There is increasing evidence that many cancers,including breast cancer,contain populations of cells that display stem-cell properties. These breast cancer stem cells,by virtue of their relative resistance to radiation and cytotoxic chemotherapy,may contribute to treatment resistance and relapse. The elucidation of pathways that regulate these cells has led to the identification of potential therapeutic targets. A number of agents capable of targeting breast cancer stem cells in preclinical models are currently entering clinical trials. Assessment of the efficacy of the agents will require development of innovative clinical trial designs with appropriate biologic and clinical end points. The effective targeting of breast cancer stem cells has the potential to significantly improve outcome for women with both early-stage and advanced breast cancer. View Publication

Despite many years of intensive effort,there is surprisingly little consensus on the most suitable markers with which to locate and isolate stem cells from adult tissues. By comparison,the study of cancer stem cells is still in its infancy; so,unsurprisingly,there is great uncertainty as to the identity of these cells. Stem cell markers can be broadly categorized into molecular determinants of self-renewal,clonogenicity,multipotentiality,adherence to the niche,and longevity. This review assesses the utility of recognizing cancer stem cells by virtue of high expression of aldehyde dehydrogenases (ALDHs),probably significant determinants of cell survival through their ability to detoxify many potentially cytotoxic molecules,and contributing to drug resistance. Antibodies are available against the ALDH enzyme family,but the vast majority of studies have used cell sorting techniques to enrich for cells expressing these enzymes. Live cells expressing high ALDH activity are usually identified by the ALDEFLUOR kit and sorted by fluorescence activated cell sorting (FACS). For many human tumours,but notably breast cancer,cell selection based upon ALDH activity appears to be a useful marker for enriching for cells with tumour-initiating activity (presumed cancer stem cells) in immunodeficient mice,and indeed the frequency of so-called ALDH(bri) cells in many tumours can be an independent prognostic indicator. View Publication

The classification of breast cancer into multiple molecular subtypes has necessitated the need for biomarkers that can assess tumor progression and the effects of chemopreventive agents on specific breast cancer subtypes. The goal of this study was to identify biomarkers whose expression are altered along with estrogen receptor α (ERα) in the polyoma middle-T antigen (PyMT) transgenic model of breast cancer and to investigate the chemopreventive activity of phenethyl isothiocyanate (PEITC). The diet of PyMT female mice was fortified with PEITC (8 mmol/kg) and the mammary streak and/or gross tumors and metastases in lungs were subjected to immunohistochemical analyses for ERα,FOXA1,and GATA-3. FOXA1 is associated with luminal type A cancers,while GATA-3 is a marker of luminal progenitor cell differentiation. In both control and PEITC-treated groups,there was a progressive loss of ERα and FOXA1 but persistence of GATA-3 expression indicating that the tumors retain luminal phenotype. Overall,the PyMT induced tumors exhibited the entire gamut of phenotypes from ERα+/FOXA1+/GATA-3+ tumors in the early stage to ERα±/FOXA1-/GATA-3+ in the late stage. Thus,PyMT model serves as an excellent model for studying progression of luminal subtype tumors. PEITC treated animals had multiple small tumors,indicating delay in tumor progression. Although these tumors were histologically similar to those in controls,there was a lower expression of these biomarkers in normal luminal cells indicating delay in tumor initiation. In in vitro studies,PEITC depleted AldeFluor-positive putative stem/progenitor cells,which may partly be responsible for the delay in tumor initiation. View Publication