Scientific Resources

Both the nonreceptor tyrosine kinase Src and the receptors for transforming growth factor (TGF)-β (TβRI,TβRII) play major roles during tumorigenesis by regulating cell growth,migration/invasion and metastasis. The common Src family kinase inhibitors PP2 and PP1 effectively block Src activity in vitro and in vivo,however,they may exert non-specific effects on other kinases. In this study,we have evaluated PP2 and PP1 for their ability to inhibit TGFβ1-mediated responses in the TGF-β-responsive pancreatic adenocarcinoma cell line Panc1. We show that PP2 and PP1 but not the more specific Src inhibitor SU6656 effectively relieved TGF-b1-induced growth arrest and p21(WAF1) induction,while basal growth was enhanced by PP2 and PP1,and suppressed by SU6656. PP2 and PP1 but not SU6656 also suppressed TGF-β1-induced epithelial-to-mesenchymal transition (EMT) as evidenced by their ability to inhibit downregulation of the epithelial marker E-cadherin,and upregulation of the EMT-associated transcription factor Slug. Likewise,PP2 and PP1 but not SU6656 effectively blocked TGF-β1-induced activation of Smad2 and p38 MAPK and partially suppressed Smad activation and transcriptional activity on TGF-β/Smad-responsive reporters of a kinase-active TβRI mutant ectopically expressed in Panc1 cells. Interestingly,PP2 and PP1 strongly inhibited recombinant TβRI in an in vitro kinase assay,with PP1 being more potent and PP2 being nearly as potent as the established TβRI inhibitor SB431542. PP2 but not PP1 also weakly inhibited the TβRII kinase. Together,these data provide evidence that PP2 and PP1 are powerful inhibitors of TβR function that can block TGF-β/Smad signaling in a Src-unrelated fashion. Both agents may be useful as dual TGF-β/Src inhibitors in experimental therapeutics of late stage metastatic disease. View Publication

PURPOSE: To explore the expression of stem cell genes in breast cancer and the relationship between stem cell gene expression and clinical and pathological characteristics and prognosis of breast cancer. BACKGROUND: By now,stem cell differentiation-related genes and the relationship between the genes and clinic-pathological characteristics and prognosis of breast cancer are still unclear. MATERIALS AND METHODS: CD44+/CD24- tumor cells were selected by Flow cytometry. The differential expression of genes between CD44+/CD24- tumor cells and non-CD44+/CD24- tumor cells were detected by RT(2) Profiler™ PCR Array. The expression of stem cell gene Octamer-4 (Oct-4) was analyzed by immunohistochemistry staining and the relationship between Oct-4 and clinicopathological parameters of breast cancer was determined. RESULTS: Seven different genes including stem cell differentiation-related factors (CD44,Oct-4,and nestin),cell cycle regulators (APC and CDC2),and growth factors (HGF and TGF) were detected as significantly differently expressed between CD44+/CD24- tumor cells and non-CD44+/CD24- tumor cells. Oct-4 protein expressed significantly higher in cancerous tissues than adjacent-tumor tissues (P = 0.001). Moreover,we observed that the expression of Oct-4 protein was related to histological type,lymph node status and molecular type of breast cancer (P = 0.001,0.006,and 0.001,respectively). After survival analysis,the cases with highly expressed Oct-4 protein attained a significantly poorer postoperative disease-specific survival than those with none/low expressed Oct-4 protein (P = 0.001). In the Cox regression test,tumor size,histological type,disease stage,lymph node metastasis,Her-2 and Oct-4 were detected as the independent prognostic factors (P = 0.031,0.012,0.001,0.002,0.030,and 0.003,respectively). CONCLUSIONS: Oct-4 was highly expressed in CD44+/CD24- tumor cells,and may be a potential biomarker for the initiation,progression,and differentiation of breast cancer. View Publication

PURPOSE: The combination of erlotinib and gemcitabine has shown a small but statistically significant survival advantage when compared with gemcitabine alone in patients with advanced pancreatic cancer. However,the overall survival rate with the erlotinib and gemcitabine combination is still low. In this study,we sought to identify gene targets that,when inhibited,would enhance the activity of epidermal growth factor receptor (EGFR)-targeted therapies in pancreatic cancer cells. EXPERIMENTAL DESIGN: A high-throughput RNA interference (RNAi) screen was carried out to identify candidate genes. Selected gene hits were further confirmed and mechanisms of action were further investigated using various assays. RESULTS: Six gene hits from siRNA screening were confirmed to significantly sensitize BxPC-3 pancreatic cancer cells to erlotinib. One of the hits,mitogen-activated protein kinase (MAPK) 1,was selected for further mechanistic studies. Combination treatments of erlotinib and two MAP kinase kinase (MEK) inhibitors,RDEA119 and AZD6244,showed significant synergistic effect for both combinations (RDEA119-erlotinib and AZD6244-erlotinib) compared with the corresponding single drug treatments in pancreatic cancer cell lines with wild-type KRAS (BxPC-3 and Hs 700T) but not in cell lines with mutant KRAS (MIA PaCa-2 and PANC-1). The enhanced antitumor activity of the combination treatment was further verified in the BxPC-3 and MIA PaCa-2 mouse xenograft model. Examination of the MAPK signaling pathway by Western blotting indicated effective inhibition of the EGFR signaling by the drug combination in KRAS wild-type cells but not in KRAS mutant cells. CONCLUSIONS: Overall,our results suggest that combination therapy of an EGFR and MEK inhibitors may have enhanced efficacy in patients with pancreatic cancer. View Publication

Imatinib mesylate has shown remarkable efficacy in the treatment of patients in the chronic phase of chronic myeloid leukemia. However,despite an overall significant hematological and cytogenetic response,imatinib therapy may favor the emergence of drug-resistant clones,ultimately leading to relapse. Some imatinib resistance mechanisms had not been fully elucidated yet. In this study we used sensitive and resistant sublines from a Bcr-Abl positive cell line to investigate the putative involvement of telomerase in the promotion of imatinib resistance. We showed that sensitivity to imatinib can be partly restored in imatinib-resistant cells by targeting telomerase expression,either by the introduction of a dominant-negative form of the catalytic protein subunit of the telomerase (hTERT) or by the treatment with all-trans-retinoic acid,a clinically used drug. Furthermore,we showed that hTERT overexpression favors the development of imatinib resistance through both its antiapoptotic and telomere maintenance functions. Therefore,combining antitelomerase strategies to imatinib treatment at the beginning of the treatment should be promoted to reduce the risk of imatinib resistance development and increase the probability of eradicating the disease. View Publication

Little is known about the origin of basal-like breast cancers,an aggressive disease that is highly similar to BRCA1-mutant breast cancers. p63 family proteins that are structurally related to the p53 suppressor protein are known to function in stem cell regulation and stratified epithelia development in multiple tissues,and p63 expression may be a marker of basal-like breast cancers. Here we report that ΔNp63 isoforms of p63 are transcriptional targets for positive regulation by BRCA1. Our analyses of breast cancer tissue microarrays and BRCA1-modulated breast cancer cell lines do not support earlier reports that p63 is a marker of basal-like or BRCA1 mutant cancers. Nevertheless,we found that BRCA1 interacts with the specific p63 isoform ΔNp63γ along with transcription factor isoforms AP-2α and AP-2γ. BRCA1 required ΔNp63γ and AP-2γ to localize to an intronic enhancer region within the p63 gene to upregulate transcription of the ΔNp63 isoforms. In mammary stem/progenitor cells,siRNA-mediated knockdown of ΔNp63 expression resulted in genomic instability,increased cell proliferation,loss of DNA damage checkpoint control,and impaired growth control. Together,our findings establish that transcriptional upregulation of ΔNp63 proteins is critical for BRCA1 suppressor function and that defects in BRCA1-ΔNp63 signaling are key events in the pathogenesis of basal-like breast cancer. View Publication

Epithelial-to-mesenchymal transition (EMT) is strongly associated with cancer progression,but its potential role during premalignant development has not been studied. Here,we show that a 4-week exposure of immortalized human bronchial epithelial cells (HBEC) to tobacco carcinogens can induce a persistent,irreversible,and multifaceted dedifferentiation program marked by EMT and the emergence of stem cell-like properties. EMT induction was epigenetically driven,initially by chromatin remodeling through H3K27me3 enrichment and later by ensuing DNA methylation to sustain silencing of tumor-suppressive microRNAs (miRNA),miR-200b,miR-200c,and miR-205,which were implicated in the dedifferentiation program in HBECs and also in primary lung tumors. Carcinogen-treated HBECs acquired stem cell-like features characterized by their ability to form spheroids with branching tubules and enrichment of the CD44(high)/CD24(low),CD133,and ALDH1 stem cell-like markers. miRNA overexpression studies indicated that regulation of the EMT,stem-like,and transformed phenotypes in HBECs were distinct events. Our findings extend present concepts of how EMT participates in cancer pathophysiology by showing that EMT induction can participate in cancer initiation to promote the clonal expansion of premalignant lung epithelial cells. View Publication

Purpose: The bone marrow microenvironment is considered a critical component in the dissemination and fate of cancer cells in the metastatic process. We explored the possible correlation between bone marrow mesenchymal stem cells (BM-MSC) and disseminated breast cancer-initiating cells (BCIC) in primary breast cancer patients. Experimental design: Bone marrow mononuclear cells (BM-MNC) were collected at the time of primary surgery in 12 breast cancer patients. BM-MNC was immunophenotyped and BCIC was defined as epithelial cells (CD326+CD45-) with a stem-like" phenotype (CD44+CD24low/-� View Publication

PURPOSE: Although most patients with estrogen receptor α (ER)-positive breast cancer initially respond to endocrine therapy,many ultimately develop resistance to antiestrogens. However,mechanisms of antiestrogen resistance and biomarkers predictive of such resistance are underdeveloped. EXPERIMENTAL DESIGN: We adapted four ER(+) human breast cancer cell lines to grow in an estrogen-depleted medium. A gene signature of estrogen independence was developed by comparing expression profiles of long-term estrogen-deprived (LTED) cells to their parental counterparts. We evaluated the ability of the LTED signature to predict tumor response to neoadjuvant therapy with an aromatase inhibitor and disease outcome following adjuvant tamoxifen. We utilized Gene Set Analysis (GSA) of LTED cell gene expression profiles and a loss-of-function approach to identify pathways causally associated with resistance to endocrine therapy. RESULTS: The LTED gene expression signature was predictive of high tumor cell proliferation following neoadjuvant therapy with anastrozole and letrozole,each in different patient cohorts. This signature was also predictive of poor recurrence-free survival in two studies of patients treated with adjuvant tamoxifen. Bioinformatic interrogation of expression profiles in LTED cells revealed a signature of MYC activation. The MYC activation signature and high MYC protein levels were both predictive of poor outcome following tamoxifen therapy. Finally,knockdown of MYC inhibited LTED cell growth. CONCLUSIONS: A gene expression signature derived from ER(+) breast cancer cells with acquired hormone independence predicted tumor response to aromatase inhibitors and associated with clinical markers of resistance to tamoxifen. Activation of the MYC pathway was associated with this resistance. View Publication

The role of autophagy,a lysosomal degradation pathway which prevents cellular damage,in the maintenance of adult mouse hematopoietic stem cells (HSCs) remains unknown. Although normal HSCs sustain life-long hematopoiesis,malignant transformation of HSCs leads to leukemia. Therefore,mechanisms protecting HSCs from cellular damage are essential to prevent hematopoietic malignancies. In this study,we crippled autophagy in HSCs by conditionally deleting the essential autophagy gene Atg7 in the hematopoietic system. This resulted in the loss of normal HSC functions,a severe myeloproliferation,and death of the mice within weeks. The hematopoietic stem and progenitor cell compartment displayed an accumulation of mitochondria and reactive oxygen species,as well as increased proliferation and DNA damage. HSCs within the Lin(-)Sca-1(+)c-Kit(+) (LSK) compartment were significantly reduced. Although the overall LSK compartment was expanded,Atg7-deficient LSK cells failed to reconstitute the hematopoietic system of lethally irradiated mice. Consistent with loss of HSC functions,the production of both lymphoid and myeloid progenitors was impaired in the absence of Atg7. Collectively,these data show that Atg7 is an essential regulator of adult HSC maintenance. View Publication

BACKGROUND: Cancer stem cells (CSCs) are purported to be epithelial tumour cells expressing CD44(+)CD24(lo) that exhibit aldehyde dehydrogenase activity (Aldefluor(+)). We hypothesised that if CSCs are responsible for tumour dissemination,disseminated cells in the bone marrow (BM) would be positive for putative breast CSC markers. Therefore,we assessed the presence of Aldefluor(+) epithelial (CD326(+)CD45(dim)) cells for the presence of the CD44(+)CD24(lo) phenotype in BM of patients with primary breast cancer (PBC). METHODS: BM aspirates were collected at the time of surgery from 66 patients with PBC. Thirty patients received neoadjuvant chemotherapy (NACT) prior to aspiration. BM was analysed for Aldefluor(+) epithelial cells with or without CD44(+)CD24(lo) expression by flow cytometry. BM aspirates from three healthy donors (HD) were subjected to identical processing and analyses and served as controls. RESULTS: Patients with triple-receptor-negative (TN) tumours had a significantly higher median percentage of CD44(+)CD24(lo) CSC within Aldefluor(+) epithelial cell population than patients with other immunohistochemical subtypes (P=0.018). Patients with TN tumours or with pN2 or higher pathologic nodal status were more likely to have a proportion of CD44(+)CD24(lo) CSC within Aldefluor(+) epithelial cell population above the highest level of HD. Furthermore,patients who received NACT were more likely to have percentages of Aldefluor(+) epithelial cells than the highest level of HD (P=0.004). CONCLUSION: The percentage of CD44(+)CD24(lo) CSC in the BM is higher in PBC patients with high risk tumour features. The selection or enrichment of Aldefluor(+) epithelial cells by NACT may represent an opportunity to target these cells with novel therapies. View Publication

Patients with Fanconi anemia (FA) have a high risk of developing acute myeloid leukemia (AML). In this study,we attempted to identify cell-surface markers for leukemia-initiating cells in FA-AML patients. We found that the IL-3 receptor-α (IL-3Rα) is a promising candidate as an leukemia-initiating cell-specific antigen for FA-AML. Whereas IL-3Rα expression is undetectable on normal CD34(+)CD38(-) HSCs,it is overexpressed on CD34(+)CD38(-) cells from FA patients with AML. We examined the leukemia-initiating cell activity of IL-3Rα-positive FA-AML cells in a humanized" FA xenotransplant model in which we separated AML cells into IL-3Rα-positive and IL-3Rα-negative CD34 fractions and transplanted them into irradiated recipient mice. In all 3 FA-AML samples� View Publication

BACKGROUND: Primitive brain tumors are the leading cause of cancer-related death in children. Tumor cells with stem-like properties (TSCs),thought to account for tumorigenesis and therapeutic resistance,have been isolated from high-grade gliomas in adults. Whether TSCs are a common component of pediatric brain tumors and are of clinical relevance remains to be determined. METHODOLOGY/PRINCIPAL FINDINGS: Tumor cells with self-renewal properties were isolated with cell biology techniques from a majority of 55 pediatric brain tumors samples,regardless of their histopathologies and grades of malignancy (57% of embryonal tumors,57% of low-grade gliomas and neuro-glial tumors,70% of ependymomas,91% of high-grade gliomas). Most high-grade glioma-derived oncospheres (10/12) sustained long-term self-renewal akin to neural stem cells (textgreater7 self-renewals),whereas cells with limited renewing abilities akin to neural progenitors dominated in all other tumors. Regardless of tumor entities,the young age group was associated with self-renewal properties akin to neural stem cells (P = 0.05,chi-square test). Survival analysis of the cohort showed an association between isolation of cells with long-term self-renewal abilities and a higher patient mortality rate (P = 0.013,log-rank test). Sampling of low- and high-grade glioma cultures showed that self-renewing cells forming oncospheres shared a molecular profile comprising embryonic and neural stem cell markers. Further characterization performed on subsets of high-grade gliomas and one low-grade glioma culture showed combination of this profile with mesenchymal markers,the radio-chemoresistance of the cells and the formation of aggressive tumors after intracerebral grafting. CONCLUSIONS/SIGNIFICANCE: In brain tumors affecting adult patients,TSCs have been isolated only from high-grade gliomas. In contrast,our data show that tumor cells with stem cell-like or progenitor-like properties can be isolated from a wide range of histological sub-types and grades of pediatric brain tumors. They suggest that cellular mechanisms fueling tumor development differ between adult and pediatric brain tumors. View Publication