All Publications

  • Single Cell Profiling of Circulating Tumor Cells: Transcriptional Heterogeneity and Diversity from Breast Cancer Cell Lines PLOS ONE Powell, A. A., Talasaz, A. H., Zhang, H., Coram, M. A., Reddy, A., Deng, G., Telli, M. L., Advani, R. H., Carlson, R. W., Mollick, J. A., Sheth, S., Kurian, A. W., Ford, J. M., Stockdale, F. E., Quake, S. R., Pease, R. F., Mindrinos, M. N., Bhanot, G., Dairkee, S. H., Davis, R. W., Jeffrey, S. S. 2012; 7 (5)


    To improve cancer therapy, it is critical to target metastasizing cells. Circulating tumor cells (CTCs) are rare cells found in the blood of patients with solid tumors and may play a key role in cancer dissemination. Uncovering CTC phenotypes offers a potential avenue to inform treatment. However, CTC transcriptional profiling is limited by leukocyte contamination; an approach to surmount this problem is single cell analysis. Here we demonstrate feasibility of performing high dimensional single CTC profiling, providing early insight into CTC heterogeneity and allowing comparisons to breast cancer cell lines widely used for drug discovery.We purified CTCs using the MagSweeper, an immunomagnetic enrichment device that isolates live tumor cells from unfractionated blood. CTCs that met stringent criteria for further analysis were obtained from 70% (14/20) of primary and 70% (21/30) of metastatic breast cancer patients; none were captured from patients with non-epithelial cancer (n = 20) or healthy subjects (n = 25). Microfluidic-based single cell transcriptional profiling of 87 cancer-associated and reference genes showed heterogeneity among individual CTCs, separating them into two major subgroups, based on 31 highly expressed genes. In contrast, single cells from seven breast cancer cell lines were tightly clustered together by sample ID and ER status. CTC profiles were distinct from those of cancer cell lines, questioning the suitability of such lines for drug discovery efforts for late stage cancer therapy.For the first time, we directly measured high dimensional gene expression in individual CTCs without the common practice of pooling such cells. Elevated transcript levels of genes associated with metastasis NPTN, S100A4, S100A9, and with epithelial mesenchymal transition: VIM, TGFß1, ZEB2, FOXC1, CXCR4, were striking compared to cell lines. Our findings demonstrate that profiling CTCs on a cell-by-cell basis is possible and may facilitate the application of 'liquid biopsies' to better model drug discovery.

    View details for DOI 10.1371/journal.pone.0033788

    View details for Web of Science ID 000305335000005

    View details for PubMedID 22586443

  • Isolating highly enriched populations of circulating epithelial cells and other rare cells from blood using a magnetic sweeper device PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Talasaz, A. H., Powell, A. A., Huber, D. E., Berbee, J. G., Roh, K., Yu, W., Xiao, W., Davis, M. M., Pease, R. F., Mindrinos, M. N., Jeffrey, S. S., Davis, R. W. 2009; 106 (10): 3970-3975


    The enumeration of rare circulating epithelial cells (CEpCs) in the peripheral blood of metastatic cancer patients has shown promise for improved cancer prognosis. Moving beyond enumeration, molecular analysis of CEpCs may provide candidate surrogate endpoints to diagnose, treat, and monitor malignancy directly from the blood samples. Thorough molecular analysis of CEpCs requires the development of new sample preparation methods that yield easily accessible and purified CEpCs for downstream biochemical assays. Here, we describe a new immunomagnetic cell separator, the MagSweeper, which gently enriches target cells and eliminates cells that are not bound to magnetic particles. The isolated cells are easily accessible and can be extracted individually based on their physical characteristics to deplete any cells nonspecifically bound to beads. We have shown that our device can process 9 mL of blood per hour and captures >50% of CEpCs as measured in spiking experiments. We have shown that the separation process does not perturb the gene expression of rare cells. To determine the efficiency of our platform in isolating CEpCs from patients, we have isolated CEpCs from all 47 tubes of 9-mL blood samples collected from 17 women with metastatic breast cancer. In contrast, we could not find any circulating epithelial cells in samples from 5 healthy donors. The isolated CEpCs are all stored individually for further molecular analysis.

    View details for DOI 10.1073/pnas.0813188106

    View details for Web of Science ID 000264036900059

    View details for PubMedID 19234122

  • Circulating tumour cells demonstrate an altered response to hypoxia and an aggressive phenotype BRITISH JOURNAL OF CANCER Ameri, K., Luong, R., Zhang, H., Powell, A. A., Montgomery, K. D., Espinosa, I., Bouley, D. M., Harris, A. L., Jeffrey, S. S. 2010; 102 (3): 561-569


    Tumours contain hypoxic regions that select for an aggressive cell phenotype; tumour hypoxia induces metastasis-associated genes. Treatment refractory patients with metastatic cancer show increased numbers of circulating tumour cells (CTCs), which are also associated with disease progression. The aim of this study was to examine the as yet unknown relationship between hypoxia and CTCs.We generated human MDA-MB-231 orthotopic xenografts and, using a new technology, isolated viable human CTCs from murine blood. The CTCs and parental MDA-MB-231 cells were incubated at 21 and 0.2% (hypoxia) oxygen, respectively. Colony formation was assayed and levels of hypoxia- and anoxia-inducible factors were measured. Xenografts generated from CTCs and parental cells were compared.MDA-MB-231 xenografts used to generate CTCs were hypoxic, expressing hypoxia factors: hypoxia-inducible factor1 alpha (HIF1alpha) and glucose transporter protein type 1 (GLUT1), and anoxia-induced factors: activating transcription factor 3 and 4 (ATF3 and ATF4). Parental MDA-MB-231 cells induced ATF3 in hypoxia, whereas CTCs expressed it constitutively. Asparagine synthetase (ASNS) expression was also higher in CTCs. Hypoxia induced ATF4 and the HIF1alpha target gene apelin in CTCs, but not in parental cells. Hypoxia induced lower levels of carbonic anhydrase IX (CAIX), GLUT1 and BCL2/adenovirus E1B 19-KD protein-interacting protein 3 (BNIP3) proteins in CTCs than in parental cells, supporting an altered hypoxia response. In chronic hypoxia, CTCs demonstrated greater colony formation than parental cells. Xenografts generated from CTCs were larger and heavier, and metastasised faster than MDA-MB-231 xenografts.CTCs show an altered hypoxia response and an enhanced aggressive phenotype in vitro and in vivo.

    View details for DOI 10.1038/sj.bjc.6605491

    View details for Web of Science ID 000274194700015

    View details for PubMedID 20051957

  • Ursodeoxycholic acid modulates histone acetylation and induces differentiation and senescence INTERNATIONAL JOURNAL OF CANCER Akare, S., Jean-Louis, S., Chen, W., Wood, D. J., Powell, A. A., Martinez, J. D. 2006; 119 (12): 2958-2969


    Agents that can modulate colonic environment and control dysregulated signaling are being evaluated for their chemopreventive potential in colon cancer. Ursodeoxycholate (UDCA) has shown chemopreventive potential in preclinical and animal models of colon cancer, but the mechanism behind it remains unknown. Here biological effects of UDCA were examined to understand mechanism behind its chemoprevention in colon cancer. Our data suggests that UDCA can suppress growth in a wide variety of cancer cell lines and can induce low level of apoptosis in colon cancer cells. We also found that UDCA treatment induces alteration in morphology, increased cell size, upregulation of cytokeratin 8, 18 and 19 and E-cadherin, cytokeratin remodeling and accumulation of lipid droplets, suggesting that UDCA induces differentiation in colon carcinoma cells. Our results also suggest significant differences in UDCA and sodium butyrate induced functional differentiation. We also report for the first time that UDCA can induce senescence in colon cancer cells as assessed by flattened, spread out and vacuolated morphology as well as by senescence marker beta-galactosidase staining. We also found that UDCA inhibits the telomerase activity. Surprisingly, we found that UDCA is not a histone deacytylase inhibitor but instead induces hypoacetylation of histones unlike hyperacetylation induced by sodium butyrate. Our results also suggest that, although UDCA induced senescence is p53, p21 and Rb independent, HDAC6 appears to be important in UDCA induced senescence. In summary, our data shows that UDCA modulates chromatin by inducing histone hypoacetylation and induces differentiation and senescence in colon cancer cells.

    View details for DOI 10.1002/ijc.22231

    View details for Web of Science ID 000242307800031

    View details for PubMedID 17019713

  • Resistance to ursodeoxycholic acid-induced growth arrest can also result in resistance to deoxycholic acid-induced apoptosis and increased tumorgenicity BMC CANCER Powell, A. A., Akare, S., Qi, W., Herzer, P., Jean-Louis, S., Feldman, R. A., Martinez, J. D. 2006; 6


    There is a large body of evidence which suggests that bile acids increase the risk of colon cancer and act as tumor promoters, however, the mechanism(s) of bile acids mediated tumorigenesis is not clear. Previously we showed that deoxycholic acid (DCA), a tumorogenic bile acid, and ursodeoxycholic acid (UDCA), a putative chemopreventive agent, exhibited distinct biological effects, yet appeared to act on some of the same signaling molecules. The present study was carried out to determine whether there is overlap in signaling pathways activated by tumorogenic bile acid DCA and chemopreventive bile acid UDCA.To determine whether there was an overlap in activation of signaling pathways by DCA and UDCA, we mutagenized HCT116 cells and then isolated cell lines resistant to UDCA induced growth arrest. These lines were then tested for their response to DCA induced apoptosis.We found that a majority of the cell lines resistant to UDCA-induced growth arrest were also resistant to DCA-induced apoptosis, implying an overlap in DCA and UDCA mediated signaling. Moreover, the cell lines which were the most resistant to DCA-induced apoptosis also exhibited a greater capacity for anchorage independent growth.We conclude that UDCA and DCA have overlapping signaling activities and that disregulation of these pathways can lead to a more advanced neoplastic phenotype.

    View details for DOI 10.1186/1471-2407-6-219

    View details for Web of Science ID 000240687000001

    View details for PubMedID 16948850

  • Cell trapping in activated micropores for functional analysis. Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference Talasaz, A. H., Powell, A. A., Stahl, P., Ronaghi, M., Jeffrey, S. S., Mindrinos, M., Davis, R. W. 2006; 1: 1838-1841


    This paper presents a novel device which provides the opportunity to perform high-throughput biochemical assays on different individual cells. In particular, the proposed device is suited to screen the rare cells in biological samples for early stage cancer diagnosis and explore their biochemical functionality. In the process, single cells are precisely positioned and captured in activated micropores. To show the performance of the proposed device, cultured yeast cells and human epithelial circulating tumor cells are successfully captured.

    View details for PubMedID 17945673

  • Cell trapping in activated micropores for functional analysis 2006 28TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-15 Talasaz, A. H., Powell, A. A., Stahl, P., Ronaghi, M., Jeffrey, S. S., Mindrinos, M., Davis, R. W. 2006: 1397-1400
  • Bile acid hydrophobicity is correlated with induction of apoptosis and/or growth arrest in HCT116 cells BIOCHEMICAL JOURNAL Powell, A. A., LaRue, J. M., Batta, A. K., Martinez, J. D. 2001; 356: 481-486


    Faecal bile acids have long been associated with colon cancer; highly hydrophobic bile acids, which induce apoptosis, have been implicated in the promotion of colon tumours. The moderately hydrophobic chemopreventive agent ursodeoxycholic acid (UDCA) does not induce apoptosis; rather, it causes colon-derived tumour cells to arrest their growth. To investigate the relationship between bile acid hydrophobicity and biological activity we examined 26 bile acids for their capacity to induce apoptosis or alter cell growth. We found that the rapidity with which, and the degree to which, bile acids could induce apoptosis or growth arrest was correlated with their relative hydrophobicities. Of the bile acids tested, only deoxycholic acid (DCA) and chenodeoxycholic acid, the most hydrophobic bile acids tested, could induce apoptosis in less than 12 h in the human colon cancer cell line HCT116. The moderately hydrophobic bile acids hyoDCA, lagoDCA, norDCA, homoUDCA and isoUDCA induced growth arrest at 12 h but longer incubations resulted in apoptosis. Conjugation of glycine or taurine to the bile acids decreased relative hydrophobicity and eliminated biological activity in our assays. In addition, we tested a subset of these bile acids for their ability to translocate across cell membranes. When (14)C-labelled and (3)H-labelled DCA, UDCA and lagoDCA were added to cell cultures, we found only minimal uptake by colon cells, whereas hepatocytes had considerably higher absorption. These experiments suggest that hydrophobicity is an important determinant of the biological activity exhibited by bile acids but that under our conditions these activities are not correlated with cellular uptake.

    View details for Web of Science ID 000169295800021

    View details for PubMedID 11368775

  • Different bile acids exhibit distinct biological effects: The tumor promoter deoxycholic acid induces apoptosis and the chemopreventive agent ursodeoxycholic acid inhibits cell proliferation NUTRITION AND CANCER-AN INTERNATIONAL JOURNAL Martinez, J. D., Stratagoules, E. D., LaRue, J. M., Powell, A. A., Gause, P. R., Craven, M. T., Payne, C. M., Powell, M. B., Gerner, E. W., Earnest, D. L. 1998; 31 (2): 111-118


    Epidemiological studies have suggested that the concentration and composition of fecal bile acids are important determining factors in the etiology of colon cancer. However, the mechanism by which these compounds influence tumor development is not understood. To begin to elucidate their mechanism of action, four bile acids, cholic acid, chenodeoxycholic acid, deoxycholic acid (DCA), and ursodeoxycholic acid, were examined for their effects on the growth of several different tumor cell lines. We found that incubating cells with chenodeoxycholic acid or DCA caused morphological changes, seen by electron and light microscopy, that were characteristic of apoptosis, whereas incubating cells with ursodeoxycholic acid inhibited cell proliferation but did not induce apoptosis. Cholic acid had no discernible effect on cells. Notably, the apoptosis induced by DCA could be suppressed by inhibiting protein kinase C activity with calphostin C. These results indicate that different bile acids exhibit distinct biological activities and suggest that the cytotoxicity reported for DCA may be due to its capacity to induce apoptosis via a protein kinase C-dependent signaling pathway.

    View details for Web of Science ID 000075853500005

    View details for PubMedID 9770722

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