Identification Of Orthotopic Pancreatic Adenocarcinoma Using Multispectral Optoacoustic Tomography

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Purpose: Current imaging methods cannot provide needed visualization of pancreatic tumors due to coarse resolution (>2mm), 2D presentation of data, requirements of ionizing radiation, or deflective light scattering and sensitivity at depth. Multispectral Optoacoustic Tomography (MSOT) detects small sound vibrations, optoacoustics, resulting from selective absorption of light at multiple wavelengths, enabling 3D volumetric spectrally enriched (color) imaging from deep living tissues in real time and at high spatial resolution. In this study, we examined the use of MSOT imaging technology in the identification of orthotopic pancreatic tumors using a near-infrared fluorescent-labeled EGF probe. Methods: Pancreatic cell lines, S2VP10, MiaPaCa2, and Panc-1, were evaluated for EGFR expression using western blot. EGF probe was constructed through bio-conjugation of functionalized EGF ligand with CF750-ester NIR dye. Specificity and activity of the EGF probe were evaluated using flow-cytometry and immunocytochemistry. SCID mice (5 mice/group) were orthotopically implanted with S2VP10 (1.5 x 105) or MiaPaCa2 (2.0 x 106) pancreatic tumor cells. Once tumors were implanted, mice were imaged using bioluminescence imaging to identify possible injection leakage. After tumors reached 3mm, 200µL of 100 nM EGF probe or dye alone were systemically injected into mice. Mice were imaged at 6-hour intervals for 24 hours using Multispectral Optoacoustic Tomography (MSOT). EGF-probe accumulation was verified ex vivo using fluorescent imaging and histology. Results: S2VP10, Panc-1, and MiaPaCa2 cells expressed EGFR at 1.2X, 1.0X, and 0.6X relative abundance, respectively. The positive control exhibited the highest EGFR expression at 1.8X, while EGFR negative NIH:3T3 cells demonstrated a value of <0.2X. Flow-cytometry showed cellular uptake of EGF probe in S2VP10 and MiaPaCa2 cell lines, while NIH3T3 (negative control) cell line exhibited minimum uptake. Blocking of S2VP10, MiaPaCa2, and SKOV3ip1 (positive control) cell lines with EGFR blocking antibody inhibited cellular binding of EGF probe. In vivo, peak accumulation of EGF probe within the tumor site was at 6 hours as observed using MSOT. EGF signal was observed within the pancreas tumor in slices from 38mm 42mm. Ex vivo evaluation of EGF probe accumulation also verified MSOT images demonstrating within the pancreas tumor, but not the liver or kidney. Conclusions: This is the first study which demonstrates the feasibility of detecting orthotopic pancreatic cancer at depths of greater than 7mm in vivo using MSOT. This benefit the field of cancer research as disease progression can be monitored at various time points during tumor growth without unnecessary euthanizing and ex vivo imaging. Citation Format: Justin Huang, Charles W. Kimbrough, Shanice V. Hudson, Wenyuan Yin, Jamie Rush, Brian P. Ceresa, Hermann B. Frieboes, Lacey R. Mcnally. Identification of orthotopic pancreatic adenocarcinoma using multispectral optoacoustic tomography. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2049. doi:10.1158/1538-7445.AM2014-2049