Mammalian Cells Seek CSF1 Sources Via Engineered Proteins

Inflammatory lesions, often seen in diseases such as rheumatoid arthritis, atherosclerosis and cancer, feature an acidic (i.e. low pH) microenvironment rampant with pro-inflammatory cytokines, such as CSF1. For targeted therapeutic intervention at these sites, engineered cells must be able to seek CSF1 sources. Here, we have assembled a system of four proteins in a cell to accomplish this feat; we introduced a CSF1 chimera receptor (named CSF1Rrec), the previously engineered CaRQ (a RhoA-based Ca2+ sensor), VSVG and thymidine kinase (TK) into cells with no natural ability to seek CSF1 sources. Binding of CSF1 to the CSF1Rrec initiates a Ca2+ signal. This Ca2+ signal is then used by CaRQ to form non-apoptotic blebs to migrate towards the CSF1 source. Next, the VSVG protein allows these engineered cells to fuse with the CSF1 source cells, upon low pH induction. Finally, these cells undergo death post-ganciclovir treatment, via the TK suicide mechanism. Hence, with the assembly of a group of proteins, we have established the basis of engineering a cell to target inflammatory lesions in diseases featuring a microenvironment with high levels of CSF1 and low pH.