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Many agents are active in multiple myeloma,but the majority of patients relapse. This clinical pattern suggests most cancer cells are eliminated,but cells with the clonogenic potential to mediate tumor regrowth are relatively chemoresistant. Our previous data suggested that CD138(+) multiple myeloma plasma cells cannot undergo long-term proliferation but rather arise from clonogenic CD138(neg) B cells. We compared the relative sensitivity of these distinct cell types to clinical antimyeloma agents and found that dexamethasone,lenadilomide,bortezomib,and 4-hydroxycyclophosphamide inhibited CD138(+) multiple myeloma plasma cells but had little effect on CD138(neg) precursors in vitro. We further characterized clonogenic multiple myeloma cells and stained cell lines using the Hoechst side population and Aldefluor assays. Each assay identified CD138(neg) cells suggesting that they possess high drug efflux capacity and intracellular drug detoxification activity. We also found that multiple myeloma cells expressing the memory B-cell markers CD20 and CD27 could give rise to clonogenic multiple myeloma growth in vitro and engraft immunodeficient nonobese diabetes/severe combined immunodeficient mice during both primary and secondary transplantation. Furthermore,both the side population and Aldefluor assays were capable of identifying circulating clonotypic memory B-cell populations within the peripheral blood of multiple myeloma patients. Our results suggest that circulating clonotypic B-cell populations represent multiple myeloma stem cells,and the relative drug resistance of these cells is mediated by processes that protect normal stem cells from toxic injury. View Publication

The aim is to investigate the clinical implications of the Oct-4 and Nestin protein in human breast cancers. A total of 346 cases including 26 fresh and 320 paraffin-embedded tumor tissues were selected for characterizing the frequency of CD44(+)CD24(-) tumor cells by flow cytometry and the differential expression of the stem cell-related genes between CD44(+)CD24(-) and non-CD44(+)CD24(-) tumor cells was analyzed by PCR Array and immunofluorescence. In comparison with the non-CD44(+)CD24(-) tumor cells,the CD44(+)CD24(-),particularly for those with high percentage of Oct-4(+) and Nestin(+),tumor cells had higher tumorigenicity by forming mammospheres in vitro. More importantly,42 (13.125%) out of 320 tumor tissues were positive for Oct-4 and Nestin staining. Universal analysis and multivariate analysis revealed that the expression of Oct-4 and Nestin was associated significantly with younger age,pathogenic degrees,lymph node metastasis and triple-negative breast cancer independently (P textless 0.05) as well as shorter survival (P = 0.001). Oct-4 and Nestin were important regulators of the development of breast cancer,and Oct-4 and Nestin may be used as predictors for the prognosis of breast cancers. View Publication

First developed for hematologic disorders,the concept of cancer stem cells (CSCs) was expanded to solid tumors,including colorectal cancer (CRC). The traditional model of colon carcinogenesis includes several steps that occur via mutational activation of oncogenes and inactivation of tumor suppressor genes. Intestinal epithelial cells exist for a shorter amount of time than that required to accumulate tumor-inducing genetic changes,so researchers have investigated the concept that CRC arises from the long-lived stem cells,rather than from the differentiated epithelial cells. Colon CSCs were originally identified through the expression of the CD133 glycoprotein using an antibody directed to its epitope AC133. It is not clear if CD133 is a marker of colon CSCs-other cell surface markers,such as epithelial-specific antigen,CD44,CD166,Musashi-1,CD29,CD24,leucine-rich repeat-containing G-protein-coupled receptor 5,and aldehyde dehydrogenase 1,have been proposed. In addition to initiating and sustaining tumor growth,CSCs are believed to mediate cancer relapse after chemotherapy. How can we identify and analyze colon CSCs and what agents are being designed to kill this chemotherapy-refractory population? View Publication

BACKGROUND: Patients generally die of cancer after the failure of current therapies to eliminate residual disease. A subpopulation of tumor cells,termed cancer stem cells (CSC),appears uniquely able to fuel the growth of phenotypically and histologically diverse tumors. It has been proposed,therefore,that failure to effectively treat cancer may in part be due to preferential resistance of these CSC to chemotherapeutic agents. The subpopulation of human colorectal tumor cells with an ESA(+)CD44(+) phenotype are uniquely responsible for tumorigenesis and have the capacity to generate heterogeneous tumors in a xenograft setting (i.e. CoCSC). We hypothesized that if non-tumorigenic cells are more susceptible to chemotherapeutic agents,then residual tumors might be expected to contain a higher frequency of CoCSC. METHODS AND FINDINGS: Xenogeneic tumors initiated with CoCSC were allowed to reach approximately 400 mm(3),at which point mice were randomized and chemotherapeutic regimens involving cyclophosphamide or Irinotecan were initiated. Data from individual tumor phenotypic analysis and serial transplants performed in limiting dilution show that residual tumors are enriched for cells with the CoCSC phenotype and have increased tumorigenic cell frequency. Moreover,the inherent ability of residual CoCSC to generate tumors appears preserved. Aldehyde dehydrogenase 1 gene expression and enzymatic activity are elevated in CoCSC and using an in vitro culture system that maintains CoCSC as demonstrated by serial transplants and lentiviral marking of single cell-derived clones,we further show that ALDH1 enzymatic activity is a major mediator of resistance to cyclophosphamide: a classical chemotherapeutic agent. CONCLUSIONS: CoCSC are enriched in colon tumors following chemotherapy and remain capable of rapidly regenerating tumors from which they originated. By focusing on the biology of CoCSC,major resistance mechanisms to specific chemotherapeutic agents can be attributed to specific genes,thereby suggesting avenues for improving cancer therapy. View Publication

Histone deacetylase (HDAC) inhibitors (HDI) induce endoplasmic reticulum (ER) stress and apoptosis,while promoting autophagy,which promotes cancer cell survival when apoptosis is compromised. Here,we determined the in vitro and in vivo activity of the combination of the pan-HDI panobinostat and the autophagy inhibitor chloroquine against human estrogen/progesterone receptor and HER2 (triple)-negative breast cancer (TNBC) cells. Treatment of MB-231 and SUM159PT cells with panobinostat disrupted the hsp90/histone deacetylase 6/HSF1/p97 complex,resulting in the upregulation of hsp. This was accompanied by the induction of enhanced autophagic flux as evidenced by increased expression of LC3B-II and the degradation of the autophagic substrate p62. Treatment with panobinostat also induced the accumulation and colocalization of p62 with LC3B-II in cytosolic foci as evidenced by immunofluorescent confocal microscopy. Inhibition of panobinostat-induced autophagic flux by chloroquine markedly induced the accumulation of polyubiquitylated proteins and p62,caused synergistic cell death of MB-231 and SUM159PT cells,and inhibited mammosphere formation in MB-231 cells,compared with treatment with each agent alone. Finally,in mouse mammary fat pad xenografts of MB-231 cells,a tumor size-dependent induction of heat shock response,ER stress and autophagy were observed. Cotreatment with panobinostat and chloroquine resulted in reduced tumor burden and increased the survival of MB-231 breast cancer xenografts. Collectively,our findings show that cotreatment with an autophagy inhibitor and pan-HDI,for example,chloroquine and panobinostat results in accumulation of toxic polyubiquitylated proteins,exerts superior inhibitory effects on TNBC cell growth,and increases the survival of TNBC xenografts. View Publication

BACKGROUND: Resistance to imatinib monotherapy frequently emerges in advanced stages of chronic myelogenous leukemia (CML),supporting the rationale for combination drug therapy. In the present study,the activities of the farnesyltransferase inhibitors (FTIs) L744,832 and LB42918,as single agents and in combination with imatinib,were investigated in different imatinib-sensitive and -resistant BCR-ABL-positive CML cells. MATERIALS AND METHODS: Growth inhibition of the cell lines and primary patient cells was assessed by MTT assays and colony-forming cell assays,respectively. Drug interactions were analyzed according to the median-effect method of Chou and Talalay. The determination of apoptotic cell death was performed by annexin V/propidium iodide staining. RESULTS: Combinations of both FTIs with imatinib displayed synergism or sensitization (potentiation) in all the cell lines tested. In primary chronic phase CML cells,additive and synergistic effects were discernible for the combination of imatinib plus L744,832 and imatinib plus LB42918,respectively. Annexin V/propidium iodide staining showed enhancement of imatinib-induced apoptosis with either drug combination,both in imatinib-sensitive and -resistant cells. CONCLUSION: The results indicated the potential of L744,832 and LB42918 as combination agents for CML patients on imatinib treatment. View Publication

The anti-proliferative activities of all twenty-five targeted kinase inhibitor drugs that are in clinical use were measured in two large assay panels: (1) a panel of proliferation assays of forty-four human cancer cell lines from diverse tumour tissue origins; and (2) a panel of more than 300 kinase enzyme activity assays. This study provides a head-on comparison of all kinase inhibitor drugs in use (status Nov. 2013),and for six of these drugs,the first kinome profiling data in the public domain. Correlation of drug activities with cancer gene mutations revealed novel drug sensitivity markers,suggesting that cancers dependent on mutant CTNNB1 will respond to trametinib and other MEK inhibitors,and cancers dependent on SMAD4 to small molecule EGFR inhibitor drugs. Comparison of cellular targeting efficacies reveals the most targeted inhibitors for EGFR,ABL1 and BRAF(V600E)-driven cell growth,and demonstrates that the best targeted agents combine high biochemical potency with good selectivity. For ABL1 inhibitors,we computationally deduce optimized kinase profiles for use in a next generation of drugs. Our study shows the power of combining biochemical and cellular profiling data in the evaluation of kinase inhibitor drug action. View Publication

Mammary cancer stem cells (MaCSCs) have been identified as a rare population of cells capable of self-renewal to drive mammary tumorigenesis and metastasis. Nevertheless,relatively little is known about the intracellular signaling pathways regulating self-renewal and metastatic activities of MaCSCs in vivo. Using a recently developed breast cancer mouse model with focal adhesion kinase (FAK) deletion in mammary tumor cells (MFCKO-MT mice),here we present evidence suggesting a compensatory function of Pyk2,a FAK-related kinase,in the regulation of MaCSCs and metastasis in these mice. Increased expression of Pyk2 was found selectively in pulmonary metastatic nodules of MFCKO-MT mice,and its inhibition significantly reduced mammary tumor development and metastasis in these mice. Consistent with the idea of metastasis driven by MaCSCs,we detected selective up-regulation of Pyk2 in MaCSCs,but not bulk mammary tumor cells,of primary tumors developed in MFCKO-MT mice. We further showed that inhibition of Pyk2 in FAK-null MaCSCs significantly decreased their tumorsphere formation and migration in vitro as well as self-renewal,tumorigenicity,and metastatic activity in vivo. Last,we identified PI3K/Akt signaling as a major mediator of FAK regulation of MaCSCs as well as a target for the compensatory function of Pyk2 in FAK-null MaCSCs. Together,these results further advance our understanding of FAK and its related tyrosine kinase Pyk2 in regulation of MaCSCs in breast cancer and suggest that pharmaceutically targeting these kinases may hold promise as a novel treatment for the disease by targeting and eradicating MaCSCs. View Publication

The MEK1 and MEK2 inhibitor GSK1120212 is currently in phase II/III clinical development. To identify predictive biomarkers,sensitivity to GSK1120212 was profiled for 218 solid tumor cell lines and 81 hematologic malignancy cell lines. For solid tumors,RAF/RAS mutation was a strong predictor of sensitivity. Among RAF/RAS mutant lines,co-occurring PIK3CA/PTEN mutations conferred a cytostatic response instead of a cytotoxic response for colon cancer cells that have the biggest representation of the comutations. Among KRAS mutant cell lines,transcriptomics analysis showed that cell lines with an expression pattern suggestive of epithelial-to-mesenchymal transition were less sensitive to GSK1120212. In addition,a proportion of cell lines from certain tissue types not known to carry frequent RAF/RAS mutations also seemed to be sensitive to GSK1120212. Among these were breast cancer cell lines,with triple negative breast cancer cell lines being more sensitive than cell lines from other breast cancer subtypes. We identified a single gene DUSP6,whose expression was associated with sensitivity to GSK1120212 and lack of expression associated with resistance irrelevant of RAF/RAS status. Among hematologic cell lines,acute myeloid leukemia and chronic myeloid leukemia cell lines were particularly sensitive. Overall,this comprehensive predictive biomarker analysis identified additional efficacy biomarkers for GSK1120212 in RAF/RAS mutant solid tumors and expanded the indication for GSK1120212 to patients who could benefit from this therapy despite the RAF/RAS wild-type status of their tumors. View Publication

We have previously developed an antibody fusion protein composed of a mouse/human chimeric IgG3 specific for the human transferrin receptor genetically fused to avidin (anti-hTfR IgG3-Av) as a universal delivery system for cancer therapy. This fusion protein efficiently delivers biotinylated FITC into cancer cells via TfR-mediated endocytosis. In addition,anti-hTfR IgG3-Av alone exhibits intrinsic cytotoxic activity and interferes with hTfR recycling,leading to the rapid degradation of the TfR and lethal iron deprivation in certain malignant B-cell lines. We now report on the cytotoxic effects of a conjugate composed of anti-hTfR IgG3-Av and biotinylated saporin 6 (b-SO6),a toxin derived from the plant Saponaria officinalis that inhibits protein synthesis. Conjugation of anti-hTfR IgG3-Av with b-SO6 enhances the cytotoxic effect of the fusion protein in sensitive cells and also overcomes the resistance of malignant cells that show low sensitivity to the fusion protein alone. Our results show for the first time that loading anti-hTfR IgG3-Av with a biotinylated toxin enhances the cytotoxicity of the fusion protein alone. These results suggest that anti-hTfR IgG3-Av has great potential as a therapeutic agent for a wide range of applications due to its intrinsic cytotoxic activity plus its ability to deliver biotinylated molecules into cancer cells. View Publication

The notion that gliomas could originate from mutated glial precursor cells highlights the possibility of modulating the proliferative and migratory behaviour of glioma cells by acting on the molecular mechanisms operative during the development of the Central Nervous System (CNS),but absent in the normal adult brain. We show that the GL15 glioblastoma derived human cell line displays a high expression of nestin which,combined with the previously demonstrated high expression of vimentin,constitutes a characteristic of astrocyte restricted precursors. We also show that,in analogy with some leukaemia cells,GL15 cells display the constitutively phosphorylated form of Janus kinase 2 (JAK2),a tyrosine kinase expressed during CNS development but undetectable in the normal adult brain. The constitutive activation of JAK2 does not result from chromosomal aberrations involving the JAK2 gene,but most probably from abnormally activated transduction systems operative in glioblastoma cells. We then investigated the effects of tyrphostin AG490,an inhibitor of JAK2 autophosphorylation,on GL15 cell growth. In the absence of exogenous growth factors and cytokines,10 microM tyrphostin AG490 induces an S phase arrest,combined with a partial impairment of the G2 phase of the cell cycle. The abnormally activated JAK2 could then potentially represent a target for a selective pharmacological approach in glioblastoma cells in which a combination of glial precursor characteristics and genetic alterations occurs. View Publication

Hereditary hemochromatosis (HH),an iron overload disease associated with mutations in the HFE gene,is characterized by increased intestinal iron absorption and consequent deposition of excess iron,primarily in the liver. Patients with HH and Hfe-deficient (Hfe-/-) mice manifest inappropriate expression of the iron absorption regulator hepcidin,a peptide hormone produced by the liver in response to iron loading. In this study,we investigated the contribution of Hfe expression in macrophages to the regulation of liver hepcidin levels and iron loading. We used bone marrow transplantation to generate wild-type (wt) and Hfe-/- mice chimeric for macrophage Hfe gene expression. Reconstitution of Hfe-deficient mice with wt bone marrow resulted in augmented capacity of the spleen to store iron and in significantly decreased liver iron loading,accompanied by a significant increase of hepatic hepcidin mRNA levels. Conversely,wt mice reconstituted with Hfe-deficient bone marrow had a diminished capacity to store iron in the spleen but no significant alterations of liver iron stores or hepcidin mRNA levels. Our results suggest that macrophage Hfe participates in the regulation of splenic and liver iron concentrations and liver hepcidin expression. View Publication