Novel Molecular Platform Integrated Iron Chelation Therapy for ¹H‑MRI Detection of β‑Galactosidase Activity

Targeting the increased Fe³⁺ content in tumors, we propose a novel molecular platform integrated cancer iron chelation therapy for ¹H-magnetic resonance imaging (MRI) detection of β-galactosidase (β-gal) activity. Following this idea, we have designed, synthesized, and characterized a series of β-d-galactosides conjugated with various chelators and demonstrated the feasibility of this concept for assessing β-gal activity in solution by ¹H-MRI <i>T</i>₁ and <i>T</i>₂ relaxation mapping

Optical assessment of vascular disruption in U87-mCherry-luc tumors.

<p>Optical imaging was performed at various times before and after administration of ATO. On each occasion FLI was performed first and then <i>D</i>-luciferin was administered SC in the neck and BLI was performed over a period of 16 mins. <b>A</b>) Sequential FLI with respect to a dose of 8 mg/kg ATO administered IP, <b>B</b>) Corresponding time course of bioluminescent signal evolution in this mouse following luciferin injection at respective times, <b>C</b>) BLI signal intensity at the 10 minute time point following luciferin administration, <b>D</b>) Normalized BLI signal intensity at 10 minute time point after administration of luciferin indicating vascular shutdown following various doses of ATO.</p

Vascular disruption assessed by BLI and PD-US in MCF7-mCherry-luc tumors with respect to ATO (8 mg/kg).

<p>A) Variation in bioluminescent signal intensity from a representative tumor on sequential occasions over 24 hrs: blue ♦ baseline; red ▪ 4 hrs; green ▴ 24 hrs. B) BLI acquired 10 mins after administration of luciferin. C) PD US images are presented as single slice (left) and PD maximum intensity projection (right) before and 4 hrs after treatment with ATO. D) Comparison of PD US and BLI in MCF7-mCherry-luc tumors as fractional signal versus baseline.</p

Reproducibility of sequential images in MCF7-mCherry-luc tumors.

<p>A group of nine MCF7-mCherry-luc tumors was repeatedly observed by FLI, BLI, and PD US following injection of 100 µl saline IP. A) Sequential FLI for a representative mouse, B) BLI from the same mouse showing images acquired 10 mins after administration of fresh luciferin on each occasion, c) PD US showing MIP (maximum intensity projection) observed at 40 MHz, D) Variation in dynamic bioluminescent signal intensity from the same tumor as in A,B and C, on five sequential occasions over 24 hrs, E) Comparison of signal stability based on FLI (red <b>□</b>), BLI (blue ▴) and PD-US (black ▴) normalized values are presented mean ± SE for the whole group.</p

Comparative vascular shutdown following ATO (8 mg/kg) to mice bearing various tumors.

<p>Relative BLI signal intensity observed for tumors 10 mins after administration of luciferin with respect to drug treatment in three different types: blue ♦ MCF7-mCherry-luc; green ▴U87-mCherry-luc; red ▪ PC3-luc; mean values ± SE.</p

Histology showing vascular impairment and apoptosis in MCF7-mCherry-luc tumors.

<p>Sections were obtained from a series of mice sacrificed at various times after ATO (8 mg/kg). Hoechst stain shows reduced perfusion 2–6 hrs following ATO and H&E stain shows increased necrosis after 24 hrs. Left column: vascular extent (CD31; green) and perfusion (Hoechst 33342; blue). Middle column: Caspase-3 activity indicating apoptosis. Right column: H&E.</p

Optical detection of U87-mCherry-luc tumor growth.

<p>A) FLI (λ_Ex = 570 nm and λ_Em = 620 nm) showed tumor growth on the back of a nude mouse. B) Corresponding BLI acquired 10 mins after administration of sodium <i>D</i>-luciferin (80 µL, 40 mg/ml). C) Correlation between signal intensities and caliper measured tumor volume for a group of six U87-mCherry-Luc tumors; FLI (•; R²>0.82) and BLI (Δ; R²>0.86); D) Correlation between FLI and BLI photon signal intensities at each measurement time (R²>0.86).</p