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Siddharth Balachandran, PhD

About

Professor

Co-Leader, Blood Cell Development and Function

Research Program

Lab Overview

The Balachandran lab is interested in how cells die during host innate-immune responses to viruses and bacteria, and in exploiting these mechanisms for the treatment of human disease, whether infectious, inflammatory or malignant.  In particular, the lab is interested in a form of programmed cell death termed necroptosis, driven by the kinase RIPK3. Unlike apoptosis, which proceeds via a caspase cascade that results in the ordered disassembly of the cell, necroptosis is caspase independent and driven by the RIPK3 substrate MLKL. Once activated by RIPK3, MLKL translocates to cellular membranes and induces their disruption, resulting in a form of necrotic cell death. Necroptosis is activated by several classes of innate-immune receptor (e.g., TLRs and cytokines such as TNF-α and interferons) and pathogen (e.g., RNA viruses, DNA viruses, certain gram-negative bacteria). The Balachandran lab is interested in how viruses (particularly RNA viruses), gram-negative bacteria, cytokines, and cellular stresses activate the necroptosis machinery, how necroptosis functions during acute viral and microbial infections to control pathogen spread, and how this death modality can be leveraged for immunotherapy.

Education and Training

Educational Background

  • PhD, Immunology & Molecular Pathogenesis, Emory University, Atlanta, GA, 2001
  • BS, Chemistry, Angelo State University, San Angelo, TX, 1995

Honors & Awards

  • Milstein Young Investigator of the Year, International Society for Interferon and Cytokine Research, 2000
  • Early Research Investigator Award, Temple Translational Science Symposium, 2013
Research Profile

Research Program

Research Interests

  • Mechanisms of innate-immune and inflammatory cell death
  • Dissecting the molecular mechanisms of RIPK 3-kinase driven cell death activated by microbes, viruses, cytokines, and cellular stresses
  • Exploring the roles of RIPK 1/3-driven cell death in resolving and propagating acute RNA virus infection and pathology
  • Exploiting cytokine- and inflammatory cell death for treatment of human malignancies

Lab Description

The Balachandran lab is interested in how cells die during host innate-immune responses to viruses and bacteria, and in exploiting these mechanisms for the treatment of human disease, whether infectious, inflammatory or malignant.  In particular, the lab is interested in a  form of programmed cell death termed necroptosis, driven by the kinase RIPK3. Unlike apoptosis, which proceeds via a caspase cascade that results in the ordered disassembly of the cell, necroptosis is caspase independent and driven by the RIPK3 substrate MLKL. Once activated by RIPK3, MLKL translocates to cellular membranes and induces their disruption, resulting in a form of necrotic cell death. Necroptosis is activated by several classes of innate-immune receptor (e.g., TLRs and cytokines such as TNF-α and interferons) and pathogen (e.g., RNA viruses, DNA viruses, certain gram-negative bacteria). The Balachandran lab is interested in how viruses (particularly RNA viruses), gram-negative bacteria, cytokines, and cellular stresses activate the necroptosis machinery, how necroptosis functions during acute viral and microbial infections to control pathogen spread, and how this death modality can be leveraged for immunotherapy.

The lab has recently outlined a pathway by which interferons (IFNs), a family of cytokines with well-known antiviral and immunomodulatory properties, activate RIPK1/3 kinases and trigger necroptotic death. The laboratory continues to work on how IFNs activate RIPK1/3 kinases, and the regulatory mechanisms that normally restrain these kinases in unstimulated cells and only license necroptosis in susceptible cells. We have identified two such mechanisms that protect cells from IFNs: the adaptor protein FADD and the transcription factor NF-κB. Current projects in this area are centered on how FADD (and caspases) are disabled to allow IFNs to trigger necroptosis during an active infection. An allied area of interest is to test the feasibility of NF-κB blockade as a combinatorial approach for the treatment of IFN-responsive human cancers.

More recently, the laboratory has identified RIPK3-activated cell death as an important host defense mechanism that limits spread of RNA viruses, including influenza A.  Influenza A viruses produce Z-RNAs, which are novel left-handed RNA duplexes previously thought not to exist in nature; these Z-RNAs trigger the host sensor protein ZBP1, which, in turn, activates, RIPK3, and  drives the activation of both MLKL-dependent necroptosis as well as a parallel pathway of FADD/caspase 8-mediated apoptosis. Molecular- and animal model-based approaches are being used to identify additional determinants and regulators of virus-induced necroptosis, relevant cell types in vivo that die by RIPK3-dependent mechanisms, and the physiological contribution of discrete cell death pathways to the control of an acute RNA virus infection.

Finally, the Balachandran laboratory is interested in leveraging necroptosis for immunotherapy, by targeting RIPK1/3 kinases in human cancers that respond to IFN therapy, or by activating ZBP1 in the tumor microenvironment by small-molecule approaches. The latter approach is of particular interest because ZBP1 can activate a form of ‘nuclear necroptosis’ that is even more immunogenic that conventional (i.e., cytoplasm-induced) necroptosis. Indeed, a major reason for the non-responsiveness of these so-called ‘cold’ tumors is that they lack an immunogenic tumor microenvironment (TME) and thus escape T-cell killing despite expressing ICB targets. How to selectively intensify the immunogenicity of the TME has been an unmet challenge. Two broad strategies are commonly pursued: the first is to increase the visibility of tumor cells to the immune system, for example, by inducing tumor cells to die by necrotic lysis, which is highly immunogenic. The second is to induce an immunogenic state in cells of the TME.  We have developed small molecule approaches that straddle both strategies to directly activate ZBP1 to trigger ‘on-demand’ nuclear necroptosis in tumor cells, as well as in cells of the TME. We are currently evaluating the potential clinical benefit of these approaches in mouse models of melanoma and other solid cancers.  

Lab Staff

Carly DeAntoneo, BS

Graduate Student

Room: R224
215-214-1528

Avishekh Gautam, PhD

Postdoctoral Associate

Room: R224
215-214-1528

Chaoran Yin, PhD

Postdoctoral Associate

Room: R224
215-214-1528

Ting Zhang, PhD

Postdoctoral Associate

Room: R224
215-214-1528
Publications

Selected Publications

Zhang T, Yin C, Boyd DF, Quarato G, Ingram JP, Shubina M, Ragan KB, Ishizuka T, Crawford JC, Tummers B, Rodriguez DA, Xue J, Peri S, Kaiser WJ, López CB, Xu Y, Upton JW, Thomas PG, Green DR, Balachandran S. Influenza Virus Z-RNAs Induce ZBP1-Mediated Necroptosis. Cell. 2020 Mar 19;180(6):1115-1129.e13. doi: 10.1016/j.cell.2020.02.050. PubMed PMID: 32200799; PubMed Central PMCID: PMC7153753. PubMed

Shubina, M., Tummers, B., Boyd, D.F., Zhang, T., Guo, X.Z., Yin, C., Kaiser, W.J., Vogel, P., Green, D.R., Thomas, P.G., Balachandran, S. Necroptosis restricts influenza A virus as a standalone cell death mechanism. J. Exp. Med. 217 (11): e20191259, 2020. PubMed PMID: 32797196; PubMed Central PMCID: PMC7596817 PubMed

Tan, Y., Sementino, S., Cheung, S., Peri, S., Menges, C.W., Kukuyan, A.M., Ross, E., Fox, L.A., Zhang, T., Khazak, V., Ramanathan, S., Jhanwar, S.C., Flores, R.M., Balachandran, S., Testa, J.R. Somatic Epigenetic Silencing of RIPK3 Inactivates Necroptosis and Contributes to Chemoresistance in Malignant Mesothelioma. Clin. Cancer Res 2020 Nov 17: clincanres.3683.2018. doi: 10.1158/1078-0432.CCR-18-3683. Online ahead of print. PMID: 33203643 PMCID in process.

Thomas P.G., Shubina M., Balachandran S. ZBP1/DAI-Dependent Cell Death Pathways in Influenza A Virus Immunity and Pathogenesis. Curr Top Microbiol Immunol, 2020. 3.153. PubMed

Ingram J.P., Thapa R.J., Fisher A., Tummers B., Zhang T., Yin C., Rodriguez D.A., Guo H., Lane R., Williams R., Slifker M.J., Basagoudanavar S.H., Rall G.F., Dillon C.P., Green D.R., Kaiser W.J., Balachandran S. ZBP1/DAI Drives RIPK3-Mediated Cell Death Induced by IFNs in the Absence of RIPK1. J Immunol. 203(5): 1348-1355, 2019.PMC6702065. 4.718. PubMed

Zhang T., Balachandran S. Bayonets over bombs: RIPK3 and MLKL restrict Listeria without triggering necroptosis. J Cell Biol. 218(6): 1773-1775, 2019.Commentary. 8.891. PubMed

Ingram JP, Tursi S, Zhang T, Guo W, Yin C, M AW-D, van der Heijden J, Cai KQ, Yamamoto M, Finlay BB, Brodsky IE, Grivennikov SI, Tukel C, Balachandran S. A Nonpyroptotic IFN-gamma-Triggered Cell Death Mechanism in Nonphagocytic Cells Promotes Salmonella Clearance In Vivo. Journal of immunology (Baltimore, Md : 1950), 200(10):3626-34, 2018. PubMed

Thapa, R.J., Ingram, J.P., Ragan, K., Nogusa, S., Sridharan, H., Boyd, D., Kosoff, R., Shubina, M., Andrake, M., Sigal, L.J., tenOever, B.R., Thomas, P.G., Upton, J. W., Balachandran, S. DAI senses influenza A virus genomic RNA and activates RIPK3-dependent cell death. Cell Host & Microbe20(5):674-681, 2016. PubMed

Najjar M, Saleh D, Zelic M, Nogusa S, Shah S, Tai A, Finger JN, Polykratis A, Gough PJ, Bertin J, Whalen M, Pasparakis M, Balachandran S, Kelliher M, Poltorak A, Degterev A. RIPK1 and RIPK3 kinases promote cell-death independent inflammation by toll-like receptor 4. Immunity. 2016;45:46-59. PubMed

Nogusa S, Slifker MJ, Ingram JP, Thapa RJ, Balachandran S. RIPK3 is largely dispensable for RIG-I-like receptor- and type I interferon-driven transcriptional responses to influenza A virus in murine fibroblasts.  PLoS One. 2016;11:e0158774. PubMed

Nogusa S, Thapa RJ, Dillon CP, Liedmann S, Oguin TH III, Ingram JP, Rodrigues DA, Kosoff R, Sharma S, Sturm O, Verbist K, Gough PJ, Bertin J, Hartmann BM, Sealfon SC, Kaiser WJ, Mocarski ES, Lopez C, Thomas PG, Oberst A, Green DR, Balachandran S. RIPK3 activates parallel pathways of MLKL-driven necroptosis and FADD-mediated apoptosis to protect against influenza A virus. Cell Host Microbe. 2016;20:13-24. PubMed

Najjar M, Suebsuwong C, Ray SR, Thapa R J, Maki JL, Nogusa S, Shah S, Saleh D, Gough PJ, Bertin J, Yuan J, Balachandran S, Cuny GD, Degterev A. Structure guided design of potent and selective ponatinib-based inhibitors for RIPK1. Cell Rep. 2015;10:1850-60. PubMed

Wang X, Wang J, Zheng H, Xie M, Hopewell EL, Albrecht RA, Nogusa S, Garcia-Sastre A, Balachandran S, Beg AA. Differential requirement for the IKKb/NF-kB signaling module in regulating TLR-versus RLR-induced type 1 IFN expression in dendritic cells. J Immunol. 2014;193:2538-45. PubMed

Haugh KA, Shalginskikh N, Nogusa S, Skalka AM, Katz RA, Balachandran S. The interferon-inducible antiviral protein Daxx is not essential for interferon-mediated protection against avian sarcoma virus. Virology J. 2014;11:100. PubMed

Kaiser WJ, Daley-Bauer LP, Thapa RJ, Mandal P, Berger SB, Huang C, Sundararajan A, Guo H, Roback L, Speck SH, Bertin J, Gough PJ, Balachandran S, Mocarski ES. RIP1 suppresses innate immune necrotic as well as apoptotic cell death during mammalian parturition. Proc Natl Acad Sci USA. 2014;111:7753-8. PubMed

Peri S, Devarajan K, Wang DH, Knudson AG, Balachandran S. Meta-analysis identifies NF-κB as a therapeutic target in renal cancer. PLoS One. 2013;8:e76746. PubMed... Expand

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