title: Synchronized cycles of bacterial lysis for in vivo delivery.
abstract: The widespread view of bacteria as strictly pathogenic has given way to an appreciation of the prevalence of some beneficial microbes within the human body. It is perhaps inevitable that some bacteria would evolve to preferentially grow in environments that harbor disease and thus provide a natural platform for the development of engineered therapies. Such therapies could benefit from bacteria that are programmed to limit bacterial growth while continually producing and releasing cytotoxic agents in situ. Here we engineer a clinically relevant bacterium to lyse synchronously ata threshold population density and to release genetically encoded cargo. Following quorum lysis, a small number of surviving bacteria reseed the growing population, thus leading to pulsatile delivery cycles. We used microfluidic devices to characterize the engineered lysis strain and we demonstrate its potential as a drug delivery platform via co-culture with human cancer cells in vitro. Asa proof of principle, we tracked the bacterial population dynamics in ectopic syngeneic colorectal tumours in mice via a luminescent reporter. The lysis strain exhibits pulsatile population dynamics in vivo, with mean bacterial luminescence that remained two orders of magnitude lower than an unmodified strain. Finally, guided by previous findings that certain bacteria can enhance the efficacy of standard therapies, we orally administered the lysis strain alone or in combination with a clinical chemotherapeutic to a syngeneic mouse transplantation model of hepatic colorectal metastases. We found that the combination of both circuit-engineered bacteria and chemotherapy leads to a notable reduction of tumour activity along with a marked survival benefit over either therapy alone.Our approach establishes a methodology for leveraging the tools of synthetic biology to exploit the natural propensity for certain bacteria to colonize disease sites.
authors.affiliation: Department of Bioengineering, University of California, San Diego, La Jolla, California, USA.
authors.forename: M Omar
authors.initials: MO
authors.lastname: Din
authors.affiliation: Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA.
authors.forename: Tal
authors.initials: T
authors.lastname: Danino
authors.affiliation: Department of Bioengineering, University of California, San Diego, La Jolla, California, USA.
authors.forename: Arthur
authors.initials: A
authors.lastname: Prindle
authors.affiliation: Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA.
authors.forename: Matt
authors.initials: M
authors.lastname: Skalak
authors.affiliation: Department of Bioengineering, University of California, San Diego, La Jolla, California, USA.
authors.forename: Jangir
authors.initials: J
authors.lastname: Selimkhanov
authors.affiliation: Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA.
authors.forename: Kaitlin
authors.initials: K
authors.lastname: Allen
authors.affiliation: Department of Bioengineering, University of California, San Diego, La Jolla, California, USA.
authors.forename: Ellixis
authors.initials: E
authors.lastname: Julio
authors.affiliation: Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA.
authors.forename: Eta
authors.initials: E
authors.lastname: Atolia
authors.affiliation: BioCircuits Institute, University of California, San Diego, La Jolla, California, USA.
authors.forename: Lev S
authors.initials: LS
authors.lastname: Tsimring
authors.affiliation: Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA.|Broad Institute of Harvard and MIT, Cambridge, MA.|Department of Medicine, Brigham and Women's Hospital, Boston, MA.|Electrical Engineering and Computer Science and David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA.|Howard Hughes Medical Institute, Chevy Chase, MD.
authors.forename: Sangeeta N
authors.initials: SN
authors.lastname: Bhatia
authors.affiliation: Department of Bioengineering, University of California, San Diego, La Jolla, California, USA.|BioCircuits Institute, University of California, San Diego, La Jolla, California, USA.|Molecular Biology Section, Division of Biological Science, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Jeff
authors.initials: J
authors.lastname: Hasty
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001433:Bacteriolysis; D018920:Coculture Techniques; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology; D003198:Computer Simulation; D016503:Drug Delivery Systems / Q000379:methods*; D005260:Female; D008113:Liver Neoplasms / Q000556:secondary; D049449:Luminescence; D051379:Mice; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D053038:Quorum Sensing; D012475:Salmonella / Q000235:genetics / Q000378:metabolism*; D058615:Synthetic Biology / Q000379:methods; D014185:Transplantation, Isogeneic