Faculty Profile

Dr. Susan Band Horwitz, Ph.D.

Susan Band Horwitz, Ph.D.

Distinguished Professor, Department of Molecular Pharmacology

Rose C. Falkenstein Chair in Cancer Research

Areas of Research: Research focuses on small molecules of natural product origin, such as Taxol®, which interact with the microtubule cytoskeleton. The goal is to understand, at a molecular level, the effects of drugs on tumor growth.

Professional Interests

The research program in this laboratory is focused on: 1) the development of drugs derived from natural products, such as Taxol® and 2) the problem of drug resistance. The mechanism of action of Taxol®, a molecule that enhances the polymerization of tubulin by forming stable microtubules, is being pursued. The novel structure of Taxol®, its unique mechanism of action that was first described in this laboratory, and the positive results that have been observed in ovarian, breast and lung carcinomas have generated extensive interest in this drug. Our laboratory has used photoaffinity analogues of Taxol® to define the binding cavity for the drug within β-tubulin. The goal is to understand at a molecular level the interaction of Taxol® with the microtubule and the mechanisms by which the drug induces growth arrest and cell death in human tumors. Evidence indicates that Taxol® alters specific intracellular signal transduction events essential for drug-induced apoptosis.

Newly discovered potentially important antitumor drugs, such as the epothilones and discodermolide that are currently in clinical trials and whose mechanism of action is similar to that of Taxol®, are being actively investigated. We have searched for differences between these agents that could be exploited in the clinic and have reported that discodermolide is the first microtubule stabilizing agent that includes a powerful induction of accelerated senescence in its repertoire of tumor cell growth inhibitory mechanisms. Quantitative mass spectrometric-based methods to analyze the expression of tubulin isotypes and their posttranslational modifications are being developed. This is crucially important since there is accumulating evidence in human cancer cell lines, tissues and tumors that different isotypes exhibit differential sensitivity to Taxol® and are related to Taxol® resistance. A recent study from our laboratory indicated that compared with other β-tubulin isotypes, βIII-tubulin binds the least amount of Taxol®.  Of particular interest is the fact that in several cancers, overexpression of βIII-tubulin is associated with drug resistance.   Our laboratory noted that one region of βIII-tubulin contains a unique residue compared with other isotypes. Molecular dynamic simulations indicated that the frequency of Taxol® accommodating conformations decreased in the βIII-tubulin isotype compared with other tubulin isotypes.

This laboratory is committed to using the knowledge gained in research for the development of therapies for the treatment of human cancer.

Selected Publications

From 260 publications

Rao, S., He, L., Chakravarty, S., Ojima, I., Orr, G.A. and Horwitz, S.B. (1999) Characterization of the Taxol Binding Site on the Microtubule. Identification of Arg282 in b-tubulin as the Site of Photoincorporation of a 7-Benzophenone Analogue of Taxol. J. Biol. Chem. 274, 38990- 37994.

He, L., Jagtap, P.G., Kingston, D.G.I., Shen, H.-H., Orr, G.A. and Horwitz, S.B. (2000) A Common Pharmacophore for Taxol and the Epothilones based on the Biological Activity of a Taxane Molecule Lacking a C-13 Side Chain. Biochemistry 39, 3972-3978.

He, L., Yang, C.-P.H. and Horwitz, S.B. (2001) Mutations in b-tubulin Map to Domains Involved in Regulation of Microtubule Stability in Epothilone-Resistant Cell Lines. Mol. Cancer Therap. 1, 3-10.

Rao, S., Aberg, F., Nieves, E., Horwitz, S.B. and Orr, G.A. (2001) Identification by Mass Spectrometry of a New b-Tubulin Isotype Expressed in Human Breast and Lung Carcinoma Cell lines. Biochemistry 40, 2096-2103.

McDaid, H.M. and Horwitz, S.B. (2001) Selective Potentiation of Taxol-induced Cell Death by MEK Inhibition in Human Cancer Cell Lines. Molecular Pharm. 60, 290-301.

McDaid, H.M., Mani, S., Shen, H.-J., Muggia, F. Sonnichsen, D. and Horwitz, S.B. (2002) Validation of the Pharmacodynamics of BMS-247550, an Analog of Epothilone B, During a Phase I Clinical Study. Clinical Cancer Res. 8, 2035- 2043.

Martello, L.A., Verdier-Pinard, P., Shen, H.-J., He, L., Torres, K., Orr, G.A. and Horwitz, S.B. (2003) Elevated Levels of Microtubule Destabilizing Factors in a Taxol-resistant/dependent A549 Cell Line with an a-Tubulin Mutation. Cancer Research 63, 1207-1213.

Verdier-Pinard, P., Wang, F., Martello, L.A., Orr, G.A. and Horwitz, S.B. (2003) Analysis of Tubulin Isotypes and Mutations from Taxol-resistant Cells by Combined Isoelectrofocusing and Mass Spectrometry. Biochemistry 42, 5349-5357.

Verdier-Pinard, P., Wang, F., Burd, B., Angeletti, R.H., Horwitz, S.B. and Orr, G.A. (2003) Direct Analysis of Tubulin Expression in Cancer Cell Lines by Electrospray Ionization Mass Spectrometry. Biochemistry 42, 12019-12027.

Orr, G.A., Verdier-Pinard, P., McDaid, H.M. and Horwitz, S.B. (2003) Mechanisms of Taxol Resistance Related to Microtubules. Oncogene 22, 7280-7295.

Chen, J.-G., Yang, C.-P. H, Cammer, M. and Horwitz, S.B. (2003) Gene Expression and Mitotic Exit Induced by Microtubule Stabilizing Drugs. Cancer Research 63, 7900-7906.

Mani, S., McDaid, H.M., Hamilton, A., Hochster, H., Cohen, M.B., Khabelle, D., Griffin, T., Lebwohl, D.E., Liebes, L., Muggia, F. and Horwitz, S.B. (2004) Phase I Clinical and Pharmacokinetic Study of BMS-247550, a novel derivative of Epothilone B, in Solid Tumors. Clinical Cancer Res. 10, 1289-1298.

Chen, J.-G., Yang, C.-P. H, Cammer, M. and Horwitz, S.B. (2003) Gene Expression and Mitotic Exit Induced by Microtubule Stabilizing Drugs. Cancer Research 63, 7900-7906.

Mani, S., McDaid, H.M., Hamilton, A., Hochster, H., Cohen, M.B., Khabelle, D., Griffin, T., Lebwohl, D.E., Liebes, L., Muggia, F. and Horwitz, S.B.  (2004)  Phase I Clinical and Pharmacokinetic Study of BMS-247550, a novel derivative of Epothilone B, in Solid Tumors. Clinical Cancer Res. 10, 1289-1298.

Honore, S., Kamath, K., Braguer, D., Horwitz, S.B., Wilson, L., Briand, C. and Jordan, M.A. (2004) Synergistic Suppression of Microtubule Dynamics by Discodermolide and Paclitaxel in Non-Small Cell Lung Carcinoma Cells. Cancer Research 64, 4957-4964.

Klein, L.E., Freeze, B.S., Smith III, A.B. and Horwitz, S.B. (2005) The Microtubule Stabilizing Agent Discodermolide is a Potent Inducer of Accelerated Senescence. Cell Cycle 4:3, 124-130.

McDaid, H.M., Lopez-Barcons, L., Grossman, A., Lia, M., Keller, S., Perez-Solar, R. and Horwitz, S.B. (2005) Enhancement of the Therapeutic Efficacy of Taxol by the MEK Inhibitor CI-1040 in Nude Mice Bearing Xenografts. Cancer Research 65, 2854-2860.

Yang, C.-P.H., Verdier-Pinard, P., Wang, F., Lippaine-Horvath, E., He, L., Orr, G.A. and Horwitz, S.B. (2005) A Highly Epothilone B-resistant A549 Cell Line with Mutations in Tubulin that Confer Drug Dependence. Mol. Cancer Ther. 4, 987-995.

Ikui, A.E., Yang, C.-P.H., Matsumoto, T. and Horwitz, S.B. (2005) Low Concentrations of Taxol Cause Mitotic Delay Followed by Premature Dissociation of p55CDC from
Mad2 and BubR1 and Abrogation of the Spindle Checkpoint, Leading to Aneuploidy. Cell Cycle 4:10, 1385-1388.

Mani, S., Huang, H., Sundarababu, S., Liu, W., Ganjam, K. Smith III, A.B., and Horwitz, S.B. (2005) Activation of the Steroid and Xenobiotic Receptor (hPXR or SXR) by Non-Taxane Microtubule Stabilizing Agents. Clinical Cancer Res. 11(17), 6359-6369. 

Verdier-Pinard, P., Shahabi, S., Wang, F., Burd, B., Goldberg, G.L., Orr, G.A. and Horwitz, S.B. (2005) Detection of Human bV-Tubulin Expression in Epithelial Cancer Cell Lines by Tubulin Proteomics. Biochemistry 44, 15858-15870.

Huang, G.S., Lopez-Barcons, L., Perez-Soler, R., Freeze, B.S., Smith III, A.B., Goldberg, G.L., Horwitz, S.B. and McDaid, H.M. (2006) Potentiation of Taxol Efficacy by Discodermolide in Ovarian Carcinoma Xenograft-bearing Mice. Clinical Cancer Res. 12, 298-304.

Xiao, H., Verdier-Pinard, P., Fernandez-Fuentes, N., Burd, B., Angeletti, R., Fiser, A., Horwitz, S.B. and Orr, G.A. (2006) Insights into the Mechanism of Microtubule Stabilization by Taxol.  Proc. Natl. Acad. Sci. 103, 10166-10173.

Xia, S., Kenesky, C.S., Rucker, P.V., Smith III, A.B., Orr, G.A. and Horwitz, S.B. (2006) A Photoaffinity Analog of Discodermolide Specifically Labels a Peptide in b-tubulin.  Biochemistry 45, 11762-11775.

Mani, S., McDaid, H.M., Grossman, A., Muggia, F., Goel, S., Griffin, T., Colevas, D., Horwitz, S.B. and Egorin, M.J. (2006) Peripheral Blood Mononuclear and Tumor Cell Pharmacodynamics of the Novel Epothilone B Analogue, Ixabepilone. Annals of Oncology Advance Access published on October 3, 2006.

Wiesen, K.M, Xia, S., Yang, C-P. and Horwitz, S.B. (2007) Wild-type class I β-tubulin sensitizes Taxol-resistant breast adenocarcinoma cells harboring a β-tubulin mutation. Cancer Letters 257, 227-235.

Legrier, M.E., Yang, C.P., Yan, H.G., LopezBarcons, L., Keller, S., Pérez-Soler, R., Horwitz, S.B., and McDaid, H.M. (2007) Targeting Protein Translation in Human Non-Small Cell Lung Cancer Via Combined MEK and mTOR Suppression.  Cancer Research, 67(23), 1300-8.

Ojima, I., Chen, J., Sun, L., Borella, C.P., Wang, T., Miller, M.L., Lin, S., Geng, X., Kuznetsova, L., Qu, C., Gallager, D., Zhao, X., Zanardi, I., Xia, S., Horwitz, S.B., Mallen-St Clair, J., Guerriero, J.L., Bar-Sagi, D., Veith, J.M., Pera, P., Bernacki, R.J. (2008) Design, synthesis, and biological evaluation of new- generation taxoids. J. Med Chem, 51(11), 3203-21.

Goel S, Comezuglu SN, Cohen M, Perrin L, Andre F, Jayabalan D, Iacono L, Comprelli A, Ly VT, Zhang D, Xu C, Humphreys WG, McDaid H, Goldberg G, Horwitz S.B., Mani S.(2008) The effect of ketoconazole on the pharmacokinetics and pharmacodynamics of ixabepilone, a first in class epothilone B analog in late phase clinical development.  Clinical Cancer Research, 14(9), 2701-9.

Miller, L., Menthena, A., Chatterjee, C., Verdier-Pinard, P., Novikoff, P.M., Horwitz, S.B., and Angeletti, R. (2008) Increased Levels of a Unique Post-Translationally Modified βIVb-Tubulin Isotype in Liver Cancer. Biochemistry 47, 7572-7582.

Devred, F., Tsvetko, P.O., Barbier, P., Allegro, D., Horwitz, S.B., Makarov, A.A., Peyrot, V. (2008) Stathmin/Op18 is a novel mediator of vinblastine activity. FEBS Letters 582 (2008) 2484-2488.

Verdier-Pinard, P., Pasquier, E., Xiao, H., Burd, B., Villard, C., Lafitte, D., Miller, L., Angeletti, R.H., Horwitz, S.B. and Braguer, D. (2009) Tubulin Proteomics: Towards breaking the code. Analytical Biochemistry 384, 197-206.

Huang GS, Arend RC, Li M, Gunter MJ, Chiu LG, Horwitz SB, Goldberg GL. (2009) Tissue microarray analysis of hormonal signaling pathways in uterine carcinosarcoma. Am. J. Obstet. Gynecol. 2009 Apr; (4):457.e1-5.

Khrapunovich-Baine, M., Menon, V., Verdier-Pinard, P., Smith, III, A.B., Angeletti, A., Fiser, A., Horwitz, S.B., Xiao, H. (2009) Distinct Pose of Discodermolide in Taxol Binding Pocket Drives a Complementary Mode of Microtubule Stabilization.  Biochemistry, 48, 11664-11677.

Yang, C.H., Liu, L., Ikui, A., and Horwitz, S.B. (2010) The Interaction Between Mitotic Checkpoint Proteins, CENP-E and BubR1, is diminished in Epothilone B-Resistant A549 Cells. Cell Cycle, 9, 1207 –1213. (Cell Cycle News and Views).

Huang, G.S., Brouwer-Visser, J., Ramirez, M., Kim, C.H., Hebert, T.M., Lin, J., Arias-Pulido, H., Qualls, C.R., Prossnitz, E.R., Goldberg, G.L., Smith, H.O., and Horwitz, S.B. (2010) Insulin-like Growth Factor 2

Expression Modulates Taxol Resistance and is a Candidate Biomarker for Reduced Disease-Free Survival in Ovarian Cancer. Clinical Cancer Research; 16 (11) 2999-3010.

Shahabi, S., Yang, C.H., Goldberg,G.L, and Horwitz, S.B. (2010) Epothilone B enhances surface EpCAM expression in ovarian Hey cells. Gynecology Oncology; 119, 345-350.

Chao, S.K., Lin, J., Brouwer-Vissera, J., Smith, III, A.B., Horwitz, S.B., and McDaid, H.M. (2011) Resistance to discodermolide, a microtubule stabilizing agent and senescence inducer, is 4E-BP1 dependent. Proc. Natl. Acad. Sci.; 108, 391-396.

Chao, S.K., Horwitz, S.B., and McDaid, H.M. (2011) Insights into 4E-BP1 and p53 mediated regulation of accelerated cell senescence.  Oncotarget, 2, No. 1-2, 89-98.

Khrapunovich-Baine, M., Menon, V., Yang, C.H., Northcote, P., Miller, J.H., Angeletti, R.A., Fiser, A., Horwitz, S.B., and Xiao, H. (2011) Hallmarks of Molecular Action of Microtubule Stabilizing Agents (MSAs): Effects of Epothilone B, Ixabepilone, Peloruside A, and Laulimalide on Microtubule Conformation. J. Biol. Chem., 286, 13, 11765-11778.

Smith, III, A.B., Sugasawa, K., Atasoylu, O, Yang, C.H., Horwitz, S.B. (2011) Design and Synthesis of (+)- Discodermolide-Paclitaxel Hybrids Leading to Enhanced Biological Activity. J. Med. Chem. 2011 Sep 22;54(18):6319-27.

Kuznetsova, L, Sun, L, Chen, J, Zhao, X, Seitz, J, Das, M, Li, Y, Veith, JM, Pera, P, Bernacki,R.J, Xia, S, Horwitz, S.B, Ojima, I. Synthesis and Biological Evaluation of Novel 3'-Difluorovinyl Taxoids. J. Fluorine Chem. 2012 Apr 15;143:177-188.

Xiao H, Wang H, Zhang X, Tu Z, Bulinski C, Khrapunovich-Baine M, Hogue Angeletti R, Horwitz S.B. (2012) Structural Evidence for Cooperative Microtubule Stabilization by Taxol and the Endogenous Dynamics Regulator MAP4. ACS Chem. Biol. 2012 Apr 20;7(4):744-52.

Chao, S.K., Wang, Y., Verdier-Pinard, P., Yang, C-P, H., Liu, L., Rodriguez-Gabina, A., McDaid, H.M., and Horwitz, S.B. (2012) Characterization of a human βV-tubulin antibody and expression of this isotype in normal and malignant human tissue. Cytoskeleton, August 2012; (69):566–576.

Miller, L.M., Yang,C-P, H., Xiao, H., Isaac, S., Seve, P., Dumontet, C., Horwitz, S.B., and Angeletti, R.A. (2012) A Label-Free Mass Spectrometry Method for Relative Quantitation of β-Tubulin Isotype Expression in Human Tumor Tissue. Proteomics Clin. Appl. 2012 Oct; 6 (9-10):502-6.

Hou JY, Rodriguez-Gabin A, Samaweera L, Hazan R, Goldberg GL, Horwitz SB and McDaid HM. (2013) Exploiting MEK Inhibitor- Mediated Activation of ERα for Therapeutic Intervention in ER-Positive Ovarian Carcinoma. PLoS ONE. Feb. 2013, 8(2): e54103.

Wang, Y., Sparano, J.A., Fineberg, S., Stead, L., Sunkara, J., Horwitz, S.B., and McDaid, H.M. (2013) High Expression of Class III β-Tubulin Predicts Good Response to Neoadjuvant Taxane and Doxorubicin/Cyclophosphamide-Based Chemotherapy in Estrogen Receptor- Negative Breast Cancer. Clin. Breast Cancer, April, 2013;13(2):103-8.

Albrethsen, J., Angeletti, R.A., Horwitz, S.B. and Yang, C-P, H. (2013) Proteomics of cancer cell lines resistant to microtubule stabilizing agents. Mol. Cancer Ther. 2014; 13:260-269

Wani, M.C. and Horwitz, S.B. Nature as a Remarkable Chemist: A Personal Story of the Discovery and Development of Taxol®. Anti-Cancer Drugs. 2014, 25(4):482-7.

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Research Information

In the News

Medscape Medical News profiles Dr. Susan Band Horwitz, who will receive the Eighth American Association for Cancer Research (AACR) Award for Lifetime Achievement in Cancer Research on April 3. (Free subscription required.)

CR magazine (a publication of the American Association for Cancer Research) profiles Dr. Susan Band Horwitz on her role in evaluating and championing the use of Taxol, the revolutionary cancer drug now widely used to treat breast and ovarian cancers.

More media coverage