Spatiotemporal control of gene expression in bone-marrow derived cells of the tumor microenvironment induced by MRI guided focused ultrasound

Abstract

The tumor microenvironment is an interesting target for anticancer therapies but modifying this compartment is challenging. Here, we demonstrate the feasibility of a gene therapy strategy that combined targeting to bone marrow-derived tumor microenvironment using genetically modified bone-marrow derived cells and control of transgene expression by local hyperthermia through a thermo-inducible promoter. Chimera were obtained by engraftment of bone marrow from transgenic mice expressing reporter genes under transcriptional control of heat shock promoter and inoculated sub-cutaneously with tumors cells. Heat shocks were applied at the tumor site using a water bath or magnetic resonance guided high intensity focused ultrasound device. Reporter gene expression was followed by bioluminescence and fluorescence imaging and immunohistochemistry. Bone marrow-derived cells expressing reporter genes were identified to be mainly tumor-associated macrophages. We thus provide the proof of concept for a gene therapy strategy that allows for spatiotemporal control of transgenes expression by macrophages targeted to the tumor microenvironment.

In Vivo Imaging of Local Gene Expression Induced by Magnetic Hyperthermia

“…Hyperthermia in combination with the temperature-sensitive 70 kDa heat-shock protein ( HSP70 ) promoter presents a unique approach, allowing noninvasive spatiotemporal control of transgene expression. We already demonstrated in vivo, by using transgenic mice and genetically modified cells, that focused-ultrasound (FUS) combined with real-time monitoring of the local temperature distribution by phase magnetic resonance imaging allows for a fine control of temperature increase and thus a good spatiotemporal control of local transgene expression by using thermosensitive promoters [ 5 , 6 , 7 ].…”

Imaging of conditional gene silencing in vivo using a bioluminescence-based method with thermo-inducible microRNAs

“…Finally, for this method, the activation of the Hsp70B promoter in vivo was accomplished using a water-bath which conferred the advantage of being a simple and low-cost system to induce hyperthermia on the entire tumor. More clinically relevant heating sources such as focal magnetic resonance-guided high-intensity focused ultrasound 10 , 16 could be adapted to the Hsp-controlled RNAi system to reach deep tissues and to have a more precise spatial control.…”

“…However, the Hsp70B promoter has many advantages including its low basal activity and the heat-induced expression 8 – 11 which could create new approaches for Hsp-controlled RNAi systems in vivo . Moreover, the efficient control of gene expression in vivo using a HSP-related promoter has been reported using encoding genes such as HSV thymidine kinase , FAS ligand and cytokine genes 9 , 12 – 14 or reporter genes for in vivo monitoring 10 , 15 , 16 .…”

Potential Applications of the Escherichia coli Heat Shock Response in Synthetic Biology

“…Hyperthermia (a procedure that increases the body or local temperature above 37 C) [73] can be applied in a well-defined volume of tissue using appropriate heating techniques. Several studies have demonstrated the feasibility a delivering a therapeutic gene product controlled in space and time and activated by a minimally invasive heating method using a HS promoter [71,74]. The development of a novel gene therapy to treat cancer cells in which therapeutic genes are activated by heat seems a logical approach because hyperthermia is currently often used in combination with chemotherapy and radiotherapy [73].…”