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1.
Theranostics ; 11(12): 6044-6057, 2021.
Article in English | MEDLINE | ID: mdl-33897898

ABSTRACT

Nitroreductases (NTR) are a family of bacterial enzymes used in gene directed enzyme prodrug therapy (GDEPT) that selectively activate prodrugs containing aromatic nitro groups to exert cytotoxic effects following gene transduction in tumours. The clinical development of NTR-based GDEPT has, in part, been hampered by the lack of translational imaging modalities to assess gene transduction and drug cytotoxicity, non-invasively. This study presents translational preclinical PET imaging to validate and report NTR activity using the clinically approved radiotracer, 18F-FMISO, as substrate for the NTR enzyme. Methods: The efficacy with which 18F-FMISO could be used to report NfsB NTR activity in vivo was investigated using the MDA-MB-231 mammary carcinoma xenograft model. For validation, subcutaneous xenografts of cells constitutively expressing NTR were imaged using 18F-FMISO PET/CT and fluorescence imaging with CytoCy5S, a validated fluorescent NTR substrate. Further, examination of the non-invasive functionality of 18F-FMISO PET/CT in reporting NfsB NTR activity in vivo was assessed in metastatic orthotopic NfsB NTR expressing xenografts and metastasis confirmed by bioluminescence imaging. 18F-FMISO biodistribution was acquired ex vivo by an automatic gamma counter measuring radiotracer retention to confirm in vivo results. To assess the functional imaging of NTR-based GDEPT with 18F-FMISO, PET/CT was performed to assess both gene transduction and cytotoxicity effects of prodrug therapy (CB1954) in subcutaneous models. Results:18F-FMISO retention was detected in NTR+ subcutaneous xenografts, displaying significantly higher PET contrast than NTR- xenografts (p < 0.0001). Substantial 18F-FMISO retention was evident in metastases of orthotopic xenografts (p < 0.05). Accordingly, higher 18F-FMISO biodistribution was prevalent ex vivo in NTR+ xenografts. 18F-FMISO NfsB NTR PET/CT imaging proved useful for monitoring in vivo NTR transduction and the cytotoxic effect of prodrug therapy. Conclusions:18F-FMISO NfsB NTR PET/CT imaging offered significant contrast between NTR+ and NTR- tumours and effective resolution of metastatic progression. Furthermore, 18F-FMISO NfsB NTR PET/CT imaging proved efficient in monitoring the two steps of GDEPT, in vivo NfsB NTR transduction and response to CB1954 prodrug therapy. These results support the repurposing of 18F-FMISO as a readily implementable PET imaging probe to be employed as companion diagnostic test for NTR-based GDEPT systems.


Subject(s)
Misonidazole/analogs & derivatives , Nitroreductases/metabolism , Positron Emission Tomography Computed Tomography/methods , Prodrugs/pharmacology , Animals , Cell Line, Tumor , Diagnostic Imaging/methods , Diagnostic Tests, Routine/methods , Drug Repositioning/methods , HEK293 Cells , Humans , Mice , Mice, Inbred NOD , Mice, SCID , Misonidazole/metabolism , Tissue Distribution/physiology
2.
J Control Release ; 245: 70-80, 2017 01 10.
Article in English | MEDLINE | ID: mdl-27871988

ABSTRACT

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest cancers with survival averaging only 3months if untreated following diagnosis. A major limitation in effectively treating PDAC using conventional and targeted chemotherapeutic agents, is inadequate drug delivery to the target location, predominantly due to a poorly vascularised, desmoplastic tumour microenvironment. Ultrasound in combination with ultrasound contrast agents, i.e., microbubbles, that flow through the vasculature and capillaries can be used to disrupt such mechanical barriers, potentially allowing for a greater therapeutic efficacy. This phenomenon is commonly referred to as sonoporation. In an attempt to improve the efficacy of sonoporation, novel microbubble formulations are being developed to address the limitation of commercially produced clinical diagnostic ultrasound contrast agents. In our work here we evaluate the ability of a novel formulation; namely Acoustic Cluster Therapy (ACT®) to improve the therapeutic efficacy of the chemotherapeutic agent paclitaxel, longitudinally in a xenograft model of PDAC. Results indicated that ACT® bubbles alone demonstrated no observable toxic effects, whilst ACT® in combination with paclitaxel can transiently reduce tumour volumes significantly, three days posttreatment (p=0.0347-0.0458). Quantitative 3D ultrasound validated the calliper measurements. Power Doppler ultrasound imaging indicated that ACT® in combination with paclitaxel was able to transiently sustain peak vasculature percentages as observed in the initial stages of tumour development. Nevertheless, there was no significant difference in tumour vasculature percentage at the end of treatment. The high vascular percentage correlated to the transient decrease and overall inhibition of the tumour volumes. In conclusion, ACT® improves the therapeutic efficacy of paclitaxel in a PDAC xenograft model allowing for transient tumour volume reduction and sustained tumour vasculature percentage.


Subject(s)
Antineoplastic Agents, Phytogenic/administration & dosage , Carcinoma, Pancreatic Ductal/therapy , Microbubbles , Paclitaxel/administration & dosage , Pancreatic Neoplasms/therapy , Ultrasonic Waves , Animals , Antineoplastic Agents, Phytogenic/therapeutic use , Carcinoma, Pancreatic Ductal/diagnostic imaging , Carcinoma, Pancreatic Ductal/pathology , Cell Line, Tumor , Humans , Male , Mice, Inbred NOD , Mice, SCID , Optical Imaging , Paclitaxel/therapeutic use , Pancreatic Neoplasms/diagnostic imaging , Pancreatic Neoplasms/pathology , Tumor Burden , Ultrasonography , Xenograft Model Antitumor Assays
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