Search

Purpose: Negative surgical margins (NSMs) have favorable prognostic implications in breast tumor resection surgery. Fluorescence image-guided surgery (FIGS) has the ability to delineate surgical margins in real time, potentially improving the completeness of tumor resection. We have recently developed indocyanine green (ICG)-loaded self-assembled hyaluronic acid (HA) nanoparticles (NanoICG) for solid tumor imaging, which were shown to enhance intraoperative contrast., Procedures: This study sought to assess the efficacy of NanoICG on completeness of breast tumor resection and post-surgical survival. BALB/c mice bearing iRFP + /luciferase + 4T1 syngeneic breast tumors were administered NanoICG or ICG, underwent FIGS, and were compared to bright light surgery (BLS) and sham controls., Results: NanoICG increased the number of complete resections and improved tumor-free survival. This was a product of improved intraoperative contrast enhancement and the identification of a greater number of small, occult lesions than ICG and BLS. Additionally, NanoICG identified chest wall invasion and predicted recurrence in a model of late-stage breast cancer., Conclusions: NanoICG is an efficacious intraoperative contrast agent and could potentially improve surgical outcomes in breast cancer.

Purpose: Tumor development and metastasis are dependent on tumor infiltrating immune cells which form a characteristic tumor microenvironment (TME). Activated monocytes secrete the protein heterodimer S100A8/A9 promoting TME formation. Monocyte-dependent proteases facilitate local tumor cell invasion by degradation of the extracellular matrix. We aimed for target specific in vivo imaging of S100A8 and proteases to provide differentiating biomarkers for local tumor growth and metastatic potential., Procedures: Murine breast cancer cells of the 4T1 model with graduated metastatic potential (4T1 and 4T07: both hematogenous metastasis > 168FAR: lymph-node metastasis > 67NR: no metastasis) were orthotopically implanted into female BALB/c mice. At 4 mm size, tumors were investigated by injecting the protease-specific probe ProSense 750EX (PerkinElmer, 4T1 n = 7, 4T07 n = 10, 168FAR n = 16, 67NR n = 15) and anti-S100A8-Cy5.5 (n = 6 each) and performing fluorescence reflectance imaging at 0 and 24 h after injection. In vivo imaging was validated with immunohistochemistry., Results: At 24 h, S100A8-specific signals in 4T1 and 4T07 were significantly higher (1714.05/1683.45 AU) as compared to 168FAR and 67NR (174.85/167.95 AU, p = 0.0012/p = 0.0003), reflecting the capability of hematogenous spread. Protease-specific signals were significantly higher in 4T1 and 4T07 (348.01/409.93 AU) as compared to 168FAR (214.91 AU) and 67NR (129.78 AU p < 0.0001 each), reflecting local vessel invasion and tumor cell shedding. Immunohistology supported the in vivo imaging results., Conclusions: Non-invasive in vivo imaging of S100A8 and monocytic proteases allows for differentiation of the tumors' local invasive and systemic metastatic potential in reflecting the TME formation. While proteases augment local tumor cell invasion, solid metastases seem to be dependent on a pro-tumoral microenvironment.

Purpose: In order to monitor the drug responses of three-dimensional mammary tumor spheroids and to elucidate the role of inter- and intra-spheroid heterogeneity in determining drug sensitivity in the spheroids, an integrated image analysis framework was developed for morphometric and metabolic characterization of the three-dimensional tumor spheroids., Procedure: Three-dimensional spheroid cultures of primary mammary tumor epithelial cells isolated from freshly excised tumors from a transgenic mouse model of adenocarcinoma (MMTV-PyMT) were imaged by using vital dyes and mitochondrial membrane potential markers. Custom-developed java and python program codes facilitated image processing, numerical computation, and graphical analysis of large datasets generated from the experiments. A panel of cancer drugs (rapamycin, BEZ235, MK2206, and flavopiridol) was tested to determine the degree of drug sensitivity as well as heterogeneity in drug response., Results: A new quantitative metric (growth/toxicity) was developed based on morphometric parameters that were found to track the growth and apoptotic cell populations. Further, this study identified two parameters, namely, skew and kurtosis-which report the spatial heterogeneity in mitochondrial metabolism within the spheroids. The results of this study show that three-dimensional tumor spheroids selectively respond to cancer drugs depending on the specific metabolic pathways (AKT inhibition pathway in the present study), and there exists significant heterogeneity in the untreated tumor spheroids. Drug sensitivity of the spheroids was found to be associated with significant alterations in mitochondrial heterogeneity within the spheroids., Conclusions: In conclusion, the quantitative imaging of morphometric and metabolic analysis in large image datasets can serve as an excellent tool box for characterizing tumor heterogeneity in three-dimensional tumor spheroids and potentially, in intact tumors as well.

Purpose: Transgenic mice expressing the polyoma middle T oncoprotein (PyMT) in the mammary epithelium were explored by multimodal imaging to monitor longitudinally spontaneous tumor growth and response to chemotherapy., Procedures: Positron emission tomography (PET) with 2-deoxy-2-[(18)F]fluoro-D-glucose ([(18)F]FDG) and 3'-deoxy-3'-[(18)F]fluorothymidine ([(18)F]FLT), single photon emission tomography (SPECT) with [(99m)Tc]TcO4 ([(99m)Tc]TEC), X-ray computed tomography, and fluorescent confocal endomicroscopy (FCE) images were acquired during tumor progression in female PyMT mice. Imaging with [(18)F]FDG and [(99m)Tc]TEC was also performed in untreated, doxorubicin-treated, and docetaxel-treated PyMT mice. Total tumor volumes were quantified. Tumors were collected and macroscopic and histological examinations were performed., Results: All PyMT mice developed multifocal tumors of the mammary epithelium that became palpable at 8 weeks of age (W8). Computed tomography (CT) detected tumors at W14, while a clear tumoral uptake of [(99m)Tc]TEC and [(18)F]FDG was present as early as W6 and W8, respectively. No contrast between mammary tumors and surrounding tissue was observed at any stage with [(18)F]FLT. FCE detected an angiogenic switch at W10. Lung metastases were not clearly evidenced by imaging. Doxorubicin and docetaxel treatments delayed tumor growth, as shown by [(18)F]FDG and [(99m)Tc]TEC, but tumor growth resumed upon treatment discontinuation. Tumor growth fitted an exponential model with time constant rates of 0.315, 0.145, and 0.212 week(-1) in untreated, doxorubicin, and docetaxel groups, respectively., Conclusions: Molecular imaging of mammary tumors in PyMT is precocious, precise, and predictive. [(18)F]FDG-PET and [(99m)Tc]TEC SPECT monitor tumor response to chemotherapy.

Purpose: The aim of this study was to compare the in vivo stability, uptake, and positron emission tomography (PET) imaging performance of a novel estrogen receptor PET tracer, 4-fluoro-11β-methoxy-16α-[(18)F]fluoroestradiol (4FMFES), with 16α-[(18)F]fluoroestradiol (FES)., Procedures: MC7-L1 and MC4-L2 (ER+) cell lines and their ERα-knockdown variants (ERαKD) were implanted subcutaneously in Balb/c mice. After 21 days, mice were imaged using either FES or 4FMFES. One hour post-injection, static images were acquired for 30 min and the tumor %ID/g uptake values were derived. Biodistribution data were also obtained 1 h following the injection of either FES or 4FMFES. Blood samples were taken at different times and analyzed on thin-layer chromatography to quantify the presence of radiometabolites for each radiotracer. To assess specific targeting to the estrogen receptors, mice bearing only ER+ tumors were treated with the competitive ER inhibitor fulvestrant 48 h prior to imaging with 4FMFES., Results: Metabolic stability was found to be similar for both tracers in mice. Both FES and 4FMFES differentiated ER+ tumors from ERαKD tumors in biodistribution and PET imaging studies. 4FMFES achieved a significantly higher %ID/g uptake in ER+ tumors and MC4-L2 ERαKD tumors than FES in the PET imaging studies. Also, tumor-to-background ratio was higher in ER+ tumors using 4FMFES compared to FES. Dissection data showed a significantly higher %ID/g in all tested cell lines and ER-rich tissues using 4FMFES versus FES. Fulvestrant-treated mice had either low or undetectable tumor uptake., Conclusion: In a tumor-bearing mouse model, 4FMFES achieves better specific tumor uptake and better contrast than FES, making it a promising candidate for ER imaging.

Purpose: The authors present a protocol for the in vivo evaluation, using different imaging techniques, of lymph node (LN) homing of tumor-specific dendritic cells (DCs) in a murine breast cancer model., Procedures: Bone marrow DCs were labeled with paramagnetic nanoparticles (MNPs) or (111)In-oxine. Antigen loading was performed using tumor lysate. Mature DCs were injected into the footpads of transgenic tumor-bearing mice (MMTV-Ras) and DC migration was tracked by magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT). Ex vivo analyses were performed to validate the imaging data., Results: DC labeling, both with MNPs and with (111)In-oxine, did not affect DC phenotype or functionality. MRI and SPECT allowed the detection of iron and (111)In in both axillary and popliteal LNs. Immunohistochemistry and γ-counting revealed the presence of DCs in LNs., Conclusions: MRI and SPECT imaging, by allowing in vivo dynamic monitoring of DC migration, could further the development and optimization of efficient anti-cancer vaccines.

Purpose: A significant positive correlation has been observed between ketone body availability and their uptake by tumor cells. Our objective was to evaluate [11C]acetoacetate as a potential tracer of ketone body utilization by breast and prostate tumors and to compare it with [11C]acetate., Methods: Biodistribution studies were performed with [11C]acetoacetate and [11C]acetate in mice bearing breast or prostate tumors. The percentage of the injected dose accumulated per gram of tissue was determined. These results were complemented by dynamic positron emission tomography (PET) imaging of the radiotracer uptake and dosimetry calculations., Results: [11C]Acetoacetate uptake was optimal between 5 and 30 min, with maximal uptake of 2.72, 2.42, 2.54, and 2.19% injected dose (%ID)/g for MC7-L1, MC4-L2, PC3, and LN-CaP tumors respectively. Tumor retention for [11C]acetoacetate tended to be higher than [11C]acetate, but this did not reach statistical significance. [11C]Acetate uptake was reached within 15 min with optimal uptake of 1.25, 2.30, and 0.96%ID/g for MC7-L1, MC4-L2, and PC-3 tumors, respectively., Conclusions: We observed a moderate uptake of [11C]acetoacetate in breast and prostate tumors with low background activity due to rapid elimination of this tracer. Further studies are warranted to determine if this tracer can detect slow-growing breast and prostate cancers in the clinical setting.