Methods for detecting host genetic modifiers of tumor vascular function using dynamic near-infrared fluorescence imaging

Abstract

Vascular supply is a critical component of the tumor microenvironment (TME) and is essential for tumor growth and metastasis, yet the endogenous genetic modifiers that impact vascular function in the TME are largely unknown. To identify the host TME modifiers of tumor vascular function, we combined a novel genetic mapping strategy [Consomic Xenograft Model] with near-infrared (NIR) fluorescence imaging and multiparametric analysis of pharmacokinetic modeling. To detect vascular flow, an intensified cooled camera based dynamic NIR imaging system with 785 nm laser diode based excitation was used to image the whole-body fluorescence emission of intravenously injected indocyanine green dye. Principal component analysis was used to extract the spatial segmentation information for the lungs, liver, and tumor regions-of-interest. Vascular function was then quantified by pK modeling of the imaging data, which revealed significantly altered tissue perfusion and vascular permeability that were caused by host genetic modifiers in the TME. Collectively, these data demonstrate that NIR fluorescent imaging can be used as a non-invasive means for characterizing host TME modifiers of vascular function that have been linked with tumor risk, progression, and response to therapy.

Differences in Expression of Mitochondrial Complexes Due to Genetic Variants May Alter Sensitivity to Radiation-Induced Cardiac Dysfunction

“…We previously reported that the inbred Dahl saltsensitive/Mcwi (SS) rat strain was more sensitive to localized image-guided cardiac radiation than the Brown Norway (BN) strain, and that substitution of chromosome 3 from the BN strain into the SS background (SS.BN3 consomic rats) confers dramatic resistance to radiation-induced cardiac dysfunction when compared to the SS strain (22). Consomic chromosome substitution studies can be used to map complex genetic modifiers of pathophysiologic phenotypes (23)(24)(25)(26). In our previous consomic rat study with the SS strain that was relatively sensitive to localized cardiac radiation when compared to the SS.BN3 consomic strain, the top genetic pathways differentially expressed between SS and SS.BN3 consomic rat ventricles 1 week after radiation included mitochondrial-related genes (22).…”

Localized and triggered release of oxaliplatin for the treatment of colorectal liver metastasis

“…Optical imaging in near-infrared (NIR) wavelength range is a non-invasive imaging that can sensitively track biochemical events using fluorescent dyes and nanomaterials. Cy5.5 dye loaded L-NIR-Fe 3 O 4 /OX phantoms or anesthetized rats were imaged by near-infrared (NIR) fluorescence imaging system (λ ex /λ em =663nm/longpass 700nm) at 100 ms exposure time using the method described elsewhere 26 . A 663 nm diode laser (90 mW) with deep cooled intensified charge-coupled device (ICCD) camera (PiMAX, Princeton Instruments, Trenton, NJ) was used for fluorescence imaging.…”

Genetic Modifiers of the Breast Tumor Microenvironment

“…A homologous mechanism has been replicated in human T lymphocytes [41] and associated with human breast cancer risk [42]. In another example, a newly developed genetic mapping strategy, Consomic/Congenic Xenograft Model (CXM), was used to identify a host TME modifier locus that is linked with DLL4 and impacts breast cancer growth and metastasis in the rat by inducing dysfunctional angiogenesis, which was independent of tumor cell changes [43–45]. Further evidence of host TME modifiers exist in mouse genetic mapping studies, including three modifier loci (Mmtg1-3) that were linked with mammary tumor angiogenesis [46] and PTPRJ, a mediator of angiogenesis [47] that was originally discovered for its role in susceptibility to colon cancer, and has since been linked with breast cancer risk [48].…”

“…The capacity of this approach could be expanded using high density tissue microarrays and quantitative immunofluorescent imaging, which offers highly sensitive and spatially resolved detection of protein expression at the cellular and subcellular levels [84–87]. Finally, we recently developed CXM as the first experimental strategy for genetic mapping of host TME modifiers [43–45]. In CXM, human breast cancer cells or patient-derived xenografts (PDX) are orthotopically implanted into genetically-engineered consomic or congenic xenograft host strains (mice or rats), which are derived from two parental strains with different susceptibilities to breast cancer.…”