Combined TP53 mutation/3p loss correlates with decreased radiosensitivity and increased matrix-metalloproteinase activity in head and neck carcinoma

OBJECTIVE

Patients with head and neck squamous cell carcinoma (HNSCC) containing TP53 mutation and 3p deletion ("double-hit") have poorer prognosis compared to patients with either event alone ("single-hit"). The etiology for worse clinical outcomes in patients with "double-hit" cancers is unclear. We compared radiosensitivity of cell lines containing both TP53 mutations and deletion of Fragile Histidine Triad (FHIT, the gene most commonly associated with 3p deletion) to "single-hit" lines with only TP53 mutation. We compared radiosensitivity in a "single-hit" cell line with TP53 mutation converted to "double-hit" using RNA interference targeting FHIT. Finally, we compared matrixmetalloproteinase-2/9 (MMP-2/9) activity, a previously-established biomarker for tumor aggressiveness, in xenograft tumors derived from these cell lines.

MATERIALS/METHODS

TP53 mutation and FHIT deletion profiles of HNSCC lines were established using Cancer Cell Line Encyclopedia (CCLE). We used RNA-interference to convert a "single-hit" cell line (SCC4) to "double-hit". Cultured cells were examined for radiosensitivity and cisplatin sensitivity. MMP-2/9 activity was evaluated in "double-hit" versus "single-hit" tumors using ratiometric activatable cell-penetrating peptide (RACPP) in tongue (n=17) and flank xenografts (n=4).

RESULTS

Radiotherapy caused greater double-stranded DNA breaks in "single-hit" vs naturally occurring and engineered "double-hit" cells. In-vivo, "double-hit" xenografts demonstrated higher MMP-2/9 activity compared to "single-hit" xenografts (p<0.01). There was no difference in cisplatin sensitivity between the cell lines.

CONCLUSIONS

TP53 mutation combined with FHIT deletion correlates with decreased radiosensitivity in HNC cell lines. Xenograft from "double-hit" cells exhibit increased MMP-2/9 activity. These findings may in part account for the worse clinical outcome seen in patients with HNSCC "double-hit" tumors.

Fluorescently labeled peptide increases identification of degenerated facial nerve branches during surgery and improves functional outcome

Nerve degeneration after transection injury decreases intraoperative visibility under white light (WL), complicating surgical repair. We show here that the use of fluorescently labeled nerve binding probe (F-NP41) can improve intraoperative visualization of chronically (up to 9 months) denervated nerves. In a mouse model for the repair of chronically denervated facial nerves, the intraoperative use of fluorescent labeling decreased time to nerve identification by 40% compared to surgeries performed under WL alone. Cumulative functional post-operative recovery was also significantly improved in the fluorescence guided group as determined by quantitatively tracking of the recovery of whisker movement at time intervals for 6 weeks post-repair. To our knowledge, this is the first description of an injectable probe that increases visibility of chronically denervated nerves during surgical repair in live animals. Future translation of this probe may improve functional outcome for patients with chronic denervation undergoing surgical repair.

Tumor radiosensitization by monomethyl auristatin E: mechanism of action and targeted delivery

Intrinsic tumor resistance to radiotherapy limits the efficacy of ionizing radiation (IR). Sensitizing cancer cells specifically to IR would improve tumor control and decrease normal tissue toxicity. The development of tumor-targeting technologies allows for developing potent radiosensitizing drugs. We hypothesized that the anti-tubulin agent monomethyl auristatin E (MMAE), a component of a clinically approved antibody-directed conjugate, could function as a potent radiosensitizer and be selectively delivered to tumors using an activatable cell-penetrating peptide targeting matrix metalloproteinases and RGD-binding integrins (ACPP-cRGD-MMAE). We evaluated the ability of MMAE to radiosensitize both established cancer cells and a low-passage cultured human pancreatic tumor cell line using clonogenic and DNA damage assays. MMAE sensitized colorectal and pancreatic cancer cells to IR in a schedule- and dose-dependent manner, correlating with mitotic arrest. Radiosensitization was evidenced by decreased clonogenic survival and increased DNA double-strand breaks in irradiated cells treated with MMAE. MMAE in combination with IR resulted in increased DNA damage signaling and activation of CHK1. To test a therapeutic strategy of MMAE and IR, PANC-1 or HCT-116 murine tumor xenografts were treated with nontargeted free MMAE or tumor-targeted MMAE (ACPP-cRGD-MMAE). While free MMAE in combination with IR resulted in tumor growth delay, tumor-targeted ACPP-cRGD-MMAE with IR produced a more robust and significantly prolonged tumor regression in xenograft models. Our studies identify MMAE as a potent radiosensitizer. Importantly, MMAE radiosensitization can be localized to tumors by targeted activatable cell-penetrating peptides.

Improved PeT molecules for optically sensing voltage in neurons

VoltageFluor (VF) dyes have the potential to measure voltage optically in excitable membranes with a combination of high spatial and temporal resolution essential to better characterize the voltage dynamics of large groups of excitable cells. VF dyes sense voltage with high speed and sensitivity using photoinduced electron transfer (PeT) through a conjugated molecular wire. We show that tuning the driving force for PeT (ΔGPeT + w) through systematic chemical substitution modulates voltage sensitivity, estimate (ΔGPeT + w) values from experimentally measured redox potentials, and validate the voltage sensitivities in patch-clamped HEK cells for 10 new VF dyes. VF2.1(OMe).H, with a 48% ΔF/F per 100 mV, shows approximately 2-fold improvement over previous dyes in HEK cells, dissociated rat cortical neurons, and medicinal leech ganglia. Additionally, VF2.1(OMe).H faithfully reports pharmacological effects and circuit activity in mouse olfactory bulb slices, thus opening a wide range of previously inaccessible applications for voltage-sensitive dyes.

How FlAsH got its sparkle: historical recollections of the biarsenical-tetracysteine tag

The biarsenical-tetracysteine tagging system was the first of (and inspiration for) the now numerous methods for site-specifically labeling proteins in living cells with small molecules such as fluorophores. This historical recollection describes its conception and the trial-and-error chemical development required to become a versatile technique.

Monitoring Integrated Activity of Individual Neurons Using FRET-Based Voltage-Sensitive Dyes

Pairs of membrane-associated molecules exhibiting fluorescence resonance energy transfer (FRET) provide a sensitive technique to measure changes in a cell's membrane potential. One of the FRET pair binds to one surface of the membrane and the other is a mobile ion that dissolves in the lipid bilayer. The voltage-related signal can be measured as a change in the fluorescence of either the donor or acceptor molecules, but measuring their ratio provides the largest and most noise-free signal. This technology has been used in a variety of ways; three are documented in this chapter: (1) high throughput drug screening, (2) monitoring the activity of many neurons simultaneously during a behavior, and (3) finding synaptic targets of a stimulated neuron. In addition, we provide protocols for using the dyes on both cultured neurons and leech ganglia. We also give an updated description of the mathematical basis for measuring the coherence between electrical and optical signals. Future improvements of this technique include faster and more sensitive dyes that bleach more slowly, and the expression of one of the FRET pair genetically.

Ratiometric activatable cell-penetrating peptides label pancreatic cancer, enabling fluorescence-guided surgery, which reduces metastases and recurrence in orthotopic mouse models

BACKGROUND

The aim of this study was to evaluate the efficacy of using matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9)-cleavable ratiometric activatable cell-penetrating peptides (RACPPs) conjugated to Cy5 and Cy7 fluorophores to accurately label pancreatic cancer for fluorescence-guided surgery (FGS) in an orthotopic mouse model.

METHODS

Orthotopic mouse models were established using MiaPaCa-2-GFP human pancreatic cancer cells. Two weeks after implantation, tumor-bearing mice were randomized to conventional white light reflectance (WLR) surgery or FGS. FGS was performed at far-red and infrared wavelengths with a customized fluorescence-dissecting microscope 2 h after injection of MMP-2 and MMP-9-cleavable RACPPs. Green fluorescence imaging of the GFP-labeled cancer cells was used to assess the effectiveness of surgical resection and monitor recurrence. At 8 weeks, mice were sacrificed to evaluate tumor burden and metastases.

RESULTS

Mice in the WLR group had larger primary tumors than mice in the FGS group at termination [1.72 g ± standard error (SE) 0.58 vs. 0.25 g ± SE 0.14; respectively, p = 0.026). Mean disease-free survival was significantly lengthened from 5.33 weeks in the WLR group to 7.38 weeks in the FGS group (p = 0.02). Recurrence rates were lower in the FGS group than in the WLR group (38 vs. 73 %; p = 0.049). This translated into lower local and distant recurrence rates for FGS compared to WLR (31 vs. 67 for local recurrence, respectively, and 25 vs. 60 % for distant recurrence, respectively). Metastatic tumor burden was significantly greater in the WLR group than in the FGS group (96.92 mm(2) ± SE 52.03 vs. 2.20 mm(2) ± SE 1.43; respectively, χ (2) = 5.455; p = 0.02).

CONCLUSIONS

RACPPs can accurately and effectively label pancreatic cancer for effective FGS, resulting in better postresection outcomes than for WLR surgery.

Fluorescence Imaging of Head and Neck Squamous Cell Carcinoma

Objectives:

(1) Demonstrate that head and neck squamous cell carcinoma (HNSCC) can be fluorescently imaged using a matrix metalloproteinase (MMP)-cleavable, ratiometric activatable cell-penetrating peptide (RACPP). (2) Correlate extent of tumor involvement with fluorescent signal.

Methods:

Increased expression of MMP-2 and MMP-9 has been well documented in multiple cancers. We developed an injectable probe (RACPP) that exhibits ratiometric fluorescence (increased Cy5:Cy7 ratio) when cleaved by these proteinases. To examine the utility of MMP2,9-cleavable RACPPs in HNSCC, mice were injected with 5 human HNSCC cell lines to establish orthotopic tongue xenografts (n = 22). Tumor-bearing mice were imaged in-vivo after intravenous RACPP injection. Fluorescent signal was correlated with histology by a blinded pathologist. Gelatinase zymography confirmed MMP-2,9 activity in these xenografts. For ex-vivo analysis of human HNSCC specimens, RACPP was applied to homogenized samples (n = 5), and fluorescence was measured on a microplate reader.

Results:

Orthotopic tongue HNSCC xenografts showed excellent ratiometric fluorescent labeling with MMP2,9-cleavable RACPP (sensitivity = 95.4%, specificity = 95.0%). Signal intensity, as defined by ratiometric contrast, was greater in areas of higher tumor burden ( P < .03). Ex vivo human HNSCC specimens treated with MMP2,9-cleavable RACPP also had increased signal intensity when compared to normal human fat ( P = .005).

Conclusions:

Fluorescent labeling with MMP2,9-cleavable RACPP is an effective way to visualize HNSCC in-vivo in a murine model, and signal intensity correlates with tumor burden. RACPPs have the potential to improve occult tumor identification and margin clearance in HNSCC. Ex-vivo assays using biopsy specimens may help identify patients who will benefit from intraoperative RACPP use and may be useful in retrospective analyses.

Matrix-metalloproteinases in head and neck carcinoma-cancer genome atlas analysis and fluorescence imaging in mice

OBJECTIVE

(1) Obtain matrix-metalloproteinase (MMP) expression profiles for head and neck squamous cell carcinoma (HNSCC) specimens from the Cancer Genomic Atlas (TCGA). (2) Demonstrate HNSCC imaging using MMP-cleavable, fluorescently labeled ratiometric activatable cell-penetrating peptide (RACPP).

STUDY DESIGN

Retrospective human cohort study; prospective animal study.

SETTING

Translational research laboratory.

SUBJECTS AND METHODS

Patient clinical data and mRNA expression levels of MMP genes were downloaded from TCGA data portal. RACPP provides complementary ratiometric fluorescent contrast (increased Cy5 and decreased Cy7 intensities) when cleaved by MMP2/9. HNSCC-tumor bearing mice were imaged in vivo after RACPP injection. Histology was evaluated by a pathologist blinded to experimental conditions. Zymography confirmed MMP-2/9 activity in xenografts. RACPP was applied to homogenized human HNSCC specimens, and ratiometric fluorescent signal was measured on a microplate reader for ex vivo analysis.

RESULTS

Expression of multiple MMPs including MMP2/9 is greater in patient HNSCC tumors than matched control tissue. In patients with human papilloma virus positive (HPV+) tumors, higher MMP2 and MMP14 expression correlates with worse 5-year survival. Orthotopic tongue HNSCC xenografts showed excellent ratiometric fluorescent labeling with MMP2/9-cleavable RACPP (sensitivity = 95.4%, specificity = 95.0%). Fluorescence ratios were greater in areas of higher tumor burden (P < .03), which is useful for intraoperative margin assessment. Ex vivo, human HNSCC specimens showed greater cleavage of RACPP when compared to control tissue (P = .009).

CONCLUSIONS

Human HNSCC tumors show increased mRNA expression of multiple MMPs including MMP2/9. We used RACPP, a ratiometric fluorescence assay of MMP2/9 activity, to show improved occult tumor identification and margin clearance. Ex vivo assays using RACPP in biopsy specimens may identify patients who will benefit from intraoperative RACPP use.

Dual-porosity hollow nanoparticles for the immunoprotection and delivery of nonhuman enzymes

Although enzymes of nonhuman origin have been studied for a variety of therapeutic and diagnostic applications, their use has been limited by the immune responses generated against them. The described dual-porosity hollow nanoparticle platform obviates immune attack on nonhuman enzymes paving the way to in vivo applications including enzyme-prodrug therapies and enzymatic depletion of tumor nutrients. This platform is manufactured with a versatile, scalable, and robust fabrication method. It efficiently encapsulates macromolecular cargos filled through mesopores into a hollow interior, shielding them from antibodies and proteases once the mesopores are sealed with nanoporous material. The nanoporous shell allows small molecule diffusion allowing interaction with the large macromolecular payload in the hollow center. The approach has been validated in vivo using l-asparaginase to achieve l-asparagine depletion in the presence of neutralizing antibodies.

An optimized triple modality reporter for quantitative in vivo tumor imaging and therapy evaluation

We present an optimized triple modality reporter construct combining a far-red fluorescent protein (E2-Crimson), enhanced firefly luciferase enzyme (Luc2), and truncated wild type herpes simplex virus I thymidine kinase (wttk) that allows for sensitive, long-term tracking of tumor growth in vivo by fluorescence, bioluminescence, and positron emission tomography. Two human cancer cell lines (MDA-MB-231 breast cancer and HT-1080 fibrosarcoma cancer) were successfully transduced to express this triple modality reporter. Fluorescence and bioluminescence imaging of the triple modality reporter were used to accurately quantify the therapeutic responses of MDA-MB-231 tumors to the chemotherapeutic agent monomethyl auristatin E in vivo in athymic nude mice. Positive correlation was observed between the fluorescence and bioluminescence signals, and these signals were also positively correlated with the ex vivo tumor weights. This is the first reported use of both fluorescence and bioluminescence signals from a multi-modality reporter construct to measure drug efficacy in vivo.

Abstract 272: Targeted Activatable Cell-Penetrating Peptides Identify Atherosclerotic Plaques in Mice with Noninvasive Magnetic Resonance Imaging

Atherosclerotic plaque progression from stable lesions to advanced plaques that can spontaneously disrupt is promoted by numerous enzymes, including thrombin and extracellular matrix metalloproteases (MMPs). Assessing the activity of these enzymes in vivo by noninvasive MRI could be a valuable tool for the risk assessment of plaque disruption and a powerful method for monitoring the effectiveness of therapies. Novel thrombin- and MMP-targeted activatable cell-penetrating peptides (ACPPs) have a mechanism for activation and retention at sites of high enzymatic activity and show great promise for plaque detection due to incorporation of gadolinium (Gd), an MR active agent. In addition to the morphological information that is traditionally provided by MRI, both ACPPs also allow for a functional assessment of plaque. We hypothesized that these new targeted ACPPs would provide enhanced contrast at a smaller dosage and improve the sensitivity and specificity of plaque detection. The aorta of fat fed male ApoE knockout mice were imaged with a T1-weighted spin echo sequence before and after the administration of a substandard dose of non-targeted Gd-DTPA (2.5 μmol/kg, compared to the standard dose of 0.1-0.2 mol/kg). Administration of a comparable dose of thrombin- or MMP-targeted ACPP yielded a great increase in contrast around the aortic plaques (Figure 1). In conclusion, administration of the targeted ACPP achieved superior contrast and, therefore, demonstrates the potential to achieve high detection power of plaques with a much lower and safer dose of Gd.

Dual targeting of integrin αvβ3 and matrix metalloproteinase-2 for optical imaging of tumors and chemotherapeutic delivery

Activatable cell-penetrating peptides (ACPP) provide a general strategy for molecular targeting by exploiting the extracellular protease activities associated with disease. Previous work used a matrix metalloproteinase (MMP-2 and 9)-cleavable sequence in the ACPP to target contrast agents for tumor imaging and fluorescence-guided surgery. To improve specificity and sensitivity for MMP-2, an integrin α(v)β(3)-binding domain, cyclic-RGD, was covalently linked to the ACPP. This co-targeting strategy relies on the interaction of MMP-2 with integrin α(v)β(3), which are known to associate via the hemopexin domain of MMP-2. In U87MG glioblastoma cells in culture, dual targeting greatly improved ACPP uptake compared with either MMP or integrin α(v)β(3) targeting alone. In vivo, dual-targeted ACPP treatment resulted in tumor contrast of 7.8 ± 1.6, a 10-fold higher tumor fluorescence compared with the negative control peptide, and increased probe penetration into the core of MDA-MB-231 tumors. This platform also significantly improved efficacy of the chemotherapeutic monomethylauristatin E (MMAE) in both MDA-MB-231 orthotopic human and syngeneic Py230 murine breast tumors. Treatment with cyclic-RGD-PLGC(Me)AG-MMAE-ACPP resulted in complete tumor regression in one quarter of MDA-MB-231 tumor-bearing mice, compared with no survival in the control groups. This rational mechanism for amplified delivery of imaging and potent chemotherapeutic agents avoids the use of antibodies and may be of considerable generality.

Early detection of thrombin activity in neuroinflammatory disease

Although multiple sclerosis (MS) has been associated with the coagulation system, the temporal and spatial regulation of coagulation activity in neuroinflammatory lesions is unknown. Using a novel molecular probe, we characterized the activity pattern of thrombin, the central protease of the coagulation cascade, in experimental autoimmune encephalomyelitis. Thrombin activity preceded onset of neurological signs, increased at disease peak, and correlated with fibrin deposition, microglial activation, demyelination, axonal damage, and clinical severity. Mice with a genetic deficit in prothrombin confirmed the specificity of the thrombin probe. Thrombin activity might be exploited for developing sensitive probes for preclinical detection and monitoring of neuroinflammation and MS progression.

Detection and monitoring of localized matrix metalloproteinase upregulation in a murine model of asthma

Extracellular proteases including matrix metalloproteinases (MMPs) are speculated to play a significant role in chronic lung diseases, such as asthma. Although increased protease expression has been correlated with lung pathogenesis, the relationship between localized enzyme activity and disease progression remains poorly understood. We report the application of MMP-2/9 activatable cell-penetrating peptides (ACPPs) and their ratiometric analogs (RACPPs) for in vivo measurement of protease activity and distribution in the lungs of mice that were challenged with the allergen ovalbumin. MMP-2/9 activity was increased greater than twofold in whole, dissected lungs from acutely challenged mice compared with control mice (P=1.8×10(-4)). This upregulation of MMP-2/9 activity was localized around inflamed airways with 1.6-fold higher protease-dependent ACPP uptake surrounding diseased airways compared with adjacent, pathologically normal lung parenchyma (P=0.03). MMP-2/9 activity detected by ACPP cleavage colocalized with gelatinase activity measured with in situ dye-quenched gelatin. For comparison, neutrophil elastase activity and thrombin activity, detected with elastase- and thrombin-cleavable RACPPs, respectively, were not significantly elevated in acutely allergen-challenged mouse lungs. The results demonstrate that ACPPs, like the MMP-2/9-activated and related ACPPs, allow for real-time detection of protease activity in a murine asthma model, which should improve our understanding of protease activation in asthma disease progression and help elucidate new therapy targets or act as a mechanism for therapeutic drug delivery.

In vivo targeting of hydrogen peroxide by activatable cell-penetrating peptides

A hydrogen peroxide (H2O2)-activated cell-penetrating peptide was developed through incorporation of a boronic acid-containing cleavable linker between polycationic cell-penetrating peptide and polyanionic fragments. Fluorescence labeling of the two ends of the molecule enabled monitoring its reaction with H2O2 through release of the highly adhesive cell-penetrating peptide and disruption of fluorescence resonance energy transfer. The H2O2 sensor selectively reacts with endogenous H2O2 in cell culture to monitor the oxidative burst of promyelocytes and in vivo to image lung inflammation. Targeting H2O2 has potential applications in imaging and therapy of diseases related to oxidative stress.

Optogenetic control of Drosophila using a red-shifted channelrhodopsin reveals experience-dependent influences on courtship

Optogenetics allows the manipulation of neural activity in freely moving animals with millisecond precision, but its application in Drosophila has been limited. Here we show that a recently described Red activatable Channelrhodopsin (ReaChR) permits control of complex behavior in freely moving adult flies, at wavelengths that are not thought to interfere with normal visual function. This tool affords the opportunity to control neural activity over a broad dynamic range of stimulation intensities. Using time-resolved activation, we show that the neural control of male courtship song can be separated into probabilistic, persistent and deterministic, command-like components. The former, but not the latter, neurons are subject to functional modulation by social experience, supporting the idea that they constitute a locus of state-dependent influence. This separation is not evident using thermogenetic tools, underscoring the importance of temporally precise control of neuronal activation in the functional dissection of neural circuits in Drosophila.

Optogenetic inhibition of synaptic release with chromophore-assisted light inactivation (CALI)

Optogenetic techniques provide effective ways of manipulating the functions of selected neurons with light. In the current study, we engineered an optogenetic technique that directly inhibits neurotransmitter release. We used a genetically encoded singlet oxygen generator, miniSOG, to conduct chromophore assisted light inactivation (CALI) of synaptic proteins. Fusions of miniSOG to VAMP2 and synaptophysin enabled disruption of presynaptic vesicular release upon illumination with blue light. In cultured neurons and hippocampal organotypic slices, synaptic release was reduced up to 100%. Such inhibition lasted >1 hr and had minimal effects on membrane electrical properties. When miniSOG-VAMP2 was expressed panneuronally in Caenorhabditis elegans, movement of the worms was reduced after illumination, and paralysis was often observed. The movement of the worms recovered overnight. We name this technique Inhibition of Synapses with CALI (InSynC). InSynC is a powerful way to silence genetically specified synapses with light in a spatially and temporally precise manner.

Abstract A005: MMP FRET ACPP imaging of mammary tumors in a mouse model of postmenopausal obesity

Obesity in postmenopausal women is a risk factor for breast cancer. Since 25-30% of women in the USA are obese, the public health implications of obesity and breast cancer are immense. Activation of inflammatory pathways is one plausible mechanism underlying the association between obesity and increased breast cancer risk. We have used a novel immunocompetent mouse model of luminal breast cancer to demonstrate that luminal tumor progression is enhanced in ovariectomized mice fed a high fat diet (HFD). The obese mammary fat pads are proinflammatory as measured by an increase in M1 polarized macrophages, increased TNF-α production and increased matrix metalloproteinase (MMP)-2 and -9 expression. To evaluate activatable cell penetrating peptide (ACPP) targeting of mammary tumors in the obese fat pad we utilized a version of the MMP cleavable ACPP that has a Cy5 fluorophore attached to the polycationic domain of the peptide and a Cy7 conjugated to the polyanionic domain. Upon cleavage of the peptide by MMPs, the fluorescence resonance energy transfer (FRET) between the two dyes is disrupted and the Cy5 emission increases while the Cy7 re-emission diminishes. This change in emission spectra is measured and the ratio of Cy5 to Cy7 fluorescence is used as a measure of peptide cleavage. The ACPP was administered at a dose of 0.4nmol/g and allowed to circulate for 2 hours prior to harvesting of the fat pads and imaging. The Cy5/Cy7 ratio was 24% higher in the obese fat pads, with a 45% increase in fluorescence when examining just the Cy5 emission. To determine if tumors could be identified in the obese fat pads with the higher background resulting from increased macrophage recruitment and MMP activity, normal chow (NC) and HFD fed C57Bl/6 mice were injected with syngeneic luminal Py230 and claudin low EMT Py8119 cell lines derived from spontaneous polyomavirus middle T (PyVmT) tumor homogenates. Mice harboring both Py230 and Py8119 tumors in their thoracic mammary fat pads were dosed with either the MMP cleavable FRET ACPP or an uncleavable control ACPP. Two hours after peptide injection, mice were sacrificed and the skin was removed to image the tumors in the context of the fat pad. In concordance with our previous results, tumor growth of the Py230 cells was significantly greater in the HFD mice. Interestingly, growth of the more aggressive Py8119 tumors was not enhanced in the HFD microenvironment. For both cell lines, the tumors were clearly delineated using the Cy5/Cy7 ratio. The Py8119 tumors had a ratio of 6.1±0.7 in NC mice and 5.4±0.3 in the HFD mice, and a similar trend was observed in the less aggressive luminal Py230 tumors, with ratios of 4.9±0.8 for NC and 3.8±0.4 for HFD fed mice. This was consistent with analysis showing increased macrophage recruitment in the Py8119 tumors compared with the Py230 tumors, but no difference in recruitment between tumors of either type in mice fed NC or HFD. Our results indicate that although inflammation associated with obesity results in higher background fluorescence in the mammary fat pad, this is not a barrier to visualizing the tumor tissue in the fat pad. Since a large amount of adipose tissue can be problematic during surgery, MMP FRET ACPPs may be useful for identifying and resecting breast cancers in obese patients leading to improved survival.

Citation Format: Jessica L. Crisp, Elamprakash N. Savariar, Jonathan P. Hasselmann, Heekyung Chung, Roger Y. Tsien, Lesley G. Ellies. MMP FRET ACPP imaging of mammary tumors in a mouse model of postmenopausal obesity. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr A005.

ReaChR: a red-shifted variant of channelrhodopsin enables deep transcranial optogenetic excitation

Channelrhodopsins (ChRs) are used to optogenetically depolarize neurons. We engineered a variant of ChR, denoted red-activatable ChR (ReaChR), that is optimally excited with orange to red light (λ ∼590-630 nm) and offers improved membrane trafficking, higher photocurrents and faster kinetics compared to existing red-shifted ChRs. Red light is less scattered by tissue and is absorbed less by blood than the blue to green wavelengths that are required by other ChR variants. We used ReaChR expressed in the vibrissa motor cortex to drive spiking and vibrissa motion in awake mice when excited with red light through intact skull. Precise vibrissa movements were evoked by expressing ReaChR in the facial motor nucleus in the brainstem and illumination with red light through the external auditory canal. Thus, ReaChR enables transcranial optical activation of neurons in deep brain structures without the need to surgically thin the skull, form a transcranial window or implant optical fibers.

Fluorescence-Guided Thyroidectomy in a Transgenic Murine Model of Papillary Thyroid Carcinoma

Objectives:

A transgenic murine model for thyroid cancer was used to evaluate the effectiveness of molecularly targeted ratiometric activatable cell-penetrating peptides (RACPPs) for surgical navigation. We will analyze the implementation of fluorescence guided surgery in this model and discuss future applications.

Methods:

Thirteen transgenic BRAFV600E mice were studied prospectively. Seven were injected with RACPP, and 4 were injected with saline (controls). Pre- and postoperative laryngoscopy was used to assess vocal cord function. Total thyroidectomy was performed with microscopic white-light visualization. Fluorescence imaging of the post-thyroidectomy field was performed, and fluorescent tissue was removed for pathology. One surgeon carried out all procedures. Data underwent blinded review by a board certified pathologist and a laryngologist.

Results:

There were 7 successful fluorescence guided surgical procedures and four successful controls. Average operative times were 15.8 (RACPP) and 14 minutes (controls). RACPPs improved thyroid tumor visualization with an average intensity ratio of 9.1, versus 1.5 with white-light alone. Intact function was present in 12 of 12 vocal cords in the study group and 1 of 2 vocal cords of the controls. Postoperatively, 5 RACPP animals showed fluorescent signal, but on histology there was no tumor. Thyroid tumor was present in the final surgical beds of 3 animals, 2 RACPP animals, and 1 control.

Conclusions:

In this transgenic murine model of papillary thyroid cancer, RACPPs improved surgical visualization without compromising post-resection vocal cord function. There was no proven benefit for completeness of resection. Surgical molecular guidance with RACPPs warrants further study.

Fluorescence-guided surgery with live molecular navigation--a new cutting edge

A glowing new era in cancer surgery may be dawning. Using fluorescently labelled markers, surgical molecular navigation means that tumours and nerves can be displayed in real time intra-operatively in contrasting pseudocolours, which allows more complete tumour resection while preserving important structures. These advances can potentially cause a paradigm shift in cancer surgery, improving patient outcome and decreasing overall health-care costs.

Fluorescent ligand for human progesterone receptor imaging in live cells

We employed molecular modeling to design and then synthesize fluorescent ligands for the human progesterone receptor. Boron dipyrromethene (BODIPY) or tetramethylrhodamine were conjugated to the progesterone receptor antagonist RU486 (Mifepristone) through an extended hydrophilic linker. The fluorescent ligands demonstrated comparable bioactivity to the parent antagonist in live cells and triggered nuclear translocation of the receptor in a specific manner. The BODIPY labeled ligand was applied to investigate the dependency of progesterone receptor nuclear translocation on partner proteins and to show that functional heat shock protein 90 but not immunophilin FKBP52 activity is essential. A tissue distribution study indicated that the fluorescent ligand preferentially accumulates in tissues that express high levels of the receptor in vivo. The design and properties of the BODIPY-labeled RU486 make it a potential candidate for in vivo imaging of PR by positron emission tomography through incorporation of (18)F into the BODIPY core.

Fluorescence imaging in surgery

Although the modern surgical era is highlighted by multiple technological advances and innovations, one area that has remained constant is the dependence of the surgeon's vision on white-light reflectance. This renders different body tissues in a limited palette of various shades of pink and red, thereby limiting the visual contrast available to the operating surgeon. Healthy tissue, anatomic variations, and diseased states are seen as slight discolorations relative to each other and differences are inherently limited in dynamic range. In the upcoming years, surgery will undergo a paradigm shift with the use of targeted fluorescence imaging probes aimed at augmenting the surgical armamentarium by expanding the "visible" spectrum available to surgeons. Such fluorescent "smart probes" will provide real-time, intraoperative, pseudo-color, high-contrast delineation of both normal and pathologic tissues. Fluorescent surgical molecular guidance promises another major leap forward to improve patient safety and clinical outcomes, and to reduce overall healthcare costs. This review provides an overview of current and future surgical applications of fluorescence imaging in diseased and nondiseased tissues and focus on the innovative fields of image processing and instrumentation.