Engineered bacteria detect spatial profiles in glucose concentration within solid tumor cell masses

Abstract

Tumor heterogeneity makes cancer difficult to treat. Many small molecule cancer drugs target rapidly dividing cells on the periphery of tumors but have difficulty in penetrating deep into tumors and are ineffective at treating entire tumors. Targeting both rapidly dividing and slower growing regions of tumors is essential to effectively treat cancer. A cancer drug carrier that penetrates deep into tumors and identifies metabolically activity could supply treatment to those areas based on the local microenvironment. We hypothesized that glucose sensing bacteria could identify sugar gradients in solid tumors. To test this hypothesis, a genetic circuit was designed to trigger expression of a green fluorescent protein (GFP) reporter through the chemotaxis-osmoporin fusion protein, Trz1, a receptor for sensing glucose and ribose sugars. E. coli equipped with the Trz1-GFP expression system, were administered to an in vitro model of a continuously perfused tumor tissue that mimics systemic delivery and clearance of bacteria through a blood vessel adjacent to a solid tumor. The level of GFP expressed, per bacterium, was time independent and indicated the glucose concentration as a function of penetration depth within the microfluidic tumors. The measured glucose concentration, correlated (P-value = 2.6×10−5) with tumor cell viability as a function of depth. Mathematical analysis predicted drug delivery by glucose-sensing bacteria would eliminate a higher percentage of the viable tumor cell population than a systemically administered drug. Glucose-sensing bacteria could deliver cancer therapies with increased drug penetration and nutrient-dependent dosing to continuously treat viable regions of cancer tissue that have a higher prevalence for metastatic dissemination.

Prediction of Necrotic Core and Hypoxic Zone of Multicellular Spheroids in a Microbioreactor with a U-Shaped Barrier

“…To demonstrate the validity of the results even under dynamic conditions, a comparison is performed between numerical and experimental data derived from a perfusion-based system. Panteli and Forbes [ 31 ] cultured cancerous LS174T colon adenocarcinoma cells as a tumor aggregate in a microfluidic T-shaped system. The authors presented glucose concentration profile inside the aggregate.…”

“… The comparison between the glucose concentration distribution inside tumor aggregate as a function of tissue depth obtained from present numerical results (case 1: and , case 2: and , case 3: and and case 4: and ) and experimental data conducted by Panteli and Forbes [ 31 ]. For both experiment and simulation, the flow rate and initial glucose concentration are Q = 3 μL/min and 5.5 mM, respectively.…”

Plasmid‐encoded protein attenuates Escherichiacoli swimming velocity and cell growth, not reprogrammed regulatory functions

“…Specifically, motility regulator, CheZ, was induced using hydrogen peroxide to guide swimming in cheZ null mutants. These studies were motivated by the desire to create “smart” probiotics, including those that swim to specific biomarkers, providing spatial control of the delivery of their therapeutic payload. Here, in the presence of elevated H 2 O 2 levels, transcriptional regulator, OxyR, undergoes a structural conformation change which results in subsequent activation of transcription of many promoters involved in oxidative stress, including oxyS .…”

Advances in bacterial cancer therapies using synthetic biology

“…The programmed bacteria sensed glucose concentration gradients over tumor cell masses within a microfluidic chamber. Their approach can be used to characterize the glucose profiles and metabolic activity over different tumor types [22]. To sense hypoxia, researchers have utilized known oxygen sensitive promoters, such as the synthetic FF20 or the endogenous promoter pepT, which are activated by oxygen binding Fumarate and Nitrate Reduction (FNR) regulatory proteins [23].…”