Efficacy of surgical staple line reinforcement in Glissonean stapling: A single-center pilot study.

Vascular staplers are routinely used in laparoscopic liver resection, which has become a standard procedure in advanced medical facilities. Although previous reports have outlined the benefits of staple line reinforcement (SLR), its application in Glissonean pedicle transection during hepatic resection remains poorly studied. This study investigated surgical SLR as a tool to enhance staple line strength and improve perioperative hemostasis. Here, 10 patients who underwent laparoscopic liver resection using the Tri-StapleTM2.0 Reinforced Reload were included. Patient characteristics, surgical details, and outcomes were assessed. The results demonstrated successful outcomes with no complications related to bile leakage or injuries during staple insertion. Overall, our findings suggest that SLR can be safely utilized in Glissonean pedicle transection during laparoscopic liver resections. Further studies are required to comprehensively evaluate its benefits compared with conventional surgical staplers.

The Impact of KRAS Status on the Required Surgical Margin Width for Colorectal Liver Metastasis Resection.

Local recurrence after colorectal liver metastasis (CRLM) resection severely affects survival; however, the required surgical margin width remains controversial. This study investigated the impact of KRAS status on surgical margin width and local recurrence rate (LRR) post-CRLM resection. Overall, 146 resected CRLMs with KRAS status (wild-type KRAS (wtKRAS): 98, KRAS mutant (mKRAS): 48) were included. The LRR for each group, R1 (margin positive) and R0 (margin negative), was analyzed by KRAS status. R0 was further stratified into Ra (margin ≥ 5 mm) and Rb (margin < 5 mm). Patients with local recurrence had significantly worse 5-year overall survival than those without local recurrence (p = 0.0036). The mKRAS LRR was significantly higher than wtKRAS LRR (p = 0.0145). R1 resection resulted in significantly higher LRRs than R0 resection for both wtKRAS and mKRAS (p = 0.0068 and p = 0.0204, respectively), and while no significant difference was observed in the Ra and Rb LRR with wtKRAS, the Rb LRR with mKRAS (33.3%) was significantly higher than Ra LRR (5.9%) (p = 0.0289). Thus, R0 resection is sufficient for CRLM with wtKRAS; however, CRLM with mKRAS requires resection with a margin of at least 5 mm to prevent local recurrence.

Timing of real-time indocyanine green fluorescence visualization for lymph node dissection during laparoscopic colon cancer surgery.

PURPOSE: Although numerous studies have highlighted the potential value of indocyanine green (ICG) imaging in lymph node dissection of cancer surgery, its efficacy and optimal method remain to be clarified. This study aimed to investigate how lymphatic flow observation via ICG fluorescence could contribute to colon cancer surgery. METHODS: From October 2018 to March 2021, a total of 56 patients with colon cancer who underwent laparoscopic complete mesocolic excision with intraoperative ICG imaging were analyzed. Lymphatic flow was examined at the following time points following ICG injection: within 5 min, 30-60 min, and over 60 min. We also evaluated the distribution of ICG fluorescence per each vascular pedicle. RESULTS: Lymphatic flow was observed within 5 min following ICG injection in 6 cases (10.7%), and at 30-60 min following ICG injection in 43 cases (76.8%). ICG-stained vascular pedicles were variable especially in hepatic flexural, transverse, and splenic flexural colon cancer. Lymph node metastases were observed in 14 cases. Although metastatic lymph nodes were present only in the area along the ICG-stained vascular pedicles in 12 of the 14 cases, two patients exhibited lymph node metastasis in areas along the ICG-unstained vascular pedicles. ICG fluorescence was observed outside the standard range of lymph node dissection in 9 cases (20.9%: 9/43). Although addition of the proposed resection areas was made in 8 of these 9 cases, there was no pathologically positive lymph node. CONCLUSION: Real-time ICG fluorescence imaging of lymph nodes may improve the performance of laparoscopic colon cancer surgery, although its oncological benefit is not yet clear.

Intracorporeal reinforcing sutures reduce anastomotic leakage in double-stapling anastomosis for laparoscopic rectal surgery.

Introduction: In rectal surgery, double-stapled anastomosis is one of the most common techniques. However, the crossing of the staple line is considered a weakness of this method and could lead to anastomotic leakage (AL), which is one of the major complications of rectal cancer surgery. Aim: To investigate the usefulness of laparoscopic intracorporeal reinforcement suturing for preventing AL in laparoscopic rectal surgery. Material and methods: A total of 153 patients with rectal cancer underwent laparoscopic rectal resection with anastomosis using the double-stapling technique between January 2015 and December 2018. Patient characteristics, surgical data, and outcomes were recorded and retrospectively analysed. Patients who received intracorporeal reinforcing sutures (n = 72) were compared with those who did not receive the reinforcing sutures (n = 81). Results: AL was observed in 11 (7.2%) cases overall and in only 1 case in the group with intracorporeal reinforcing sutures. There were no associations between clinicopathological factors and the use of reinforcing sutures. Multivariate analysis revealed that a distance from the anal verge of less than 6.5 cm, diabetes mellitus, and the non-use of reinforcing sutures were independent risk factors for AL. Conclusions: Laparoscopic intracorporeal reinforcing sutures reduced the incidence of AL. Therefore, laparoscopic reinforcing sutures for double-stapled anastomoses seem useful for the prevention of AL.

Structure-guided design enables development of a hyperpolarized molecular probe for the detection of aminopeptidase N activity in vivo.

Dynamic nuclear polarization (DNP) is a cutting-edge technique that markedly enhances the detection sensitivity of molecules using nuclear magnetic resonance (NMR)/magnetic resonance imaging (MRI). This methodology enables real-time imaging of dynamic metabolic status in vivo using MRI. To expand the targetable metabolic reactions, there is a demand for developing exogenous, i.e., artificially designed, DNP-NMR molecular probes; however, complying with the requirements of practical DNP-NMR molecular probes is challenging because of the lack of established design guidelines. Here, we report Ala-[1-13C]Gly-d2-NMe2 as a DNP-NMR molecular probe for in vivo detection of aminopeptidase N activity. We developed this probe rationally through precise structural investigation, calculation, biochemical assessment, and advanced molecular design to achieve rapid and detectable responses to enzyme activity in vivo. With the fabricated probe, we successfully detected enzymatic activity in vivo. This report presents a comprehensive approach for the development of artificially derived, practical DNP-NMR molecular probes through structure-guided molecular design.

Laparoscopic posterior pelvic exenteration for clear cell adenocarcinoma arising in an episiotomy scar.

Malignant degeneration of endometriosis is a very rare event, especially when it develops in an episiotomy scar. A 53-year-old woman with an enlarged perineal mass presented to the hospital. She had undergone vaginal delivery with episiotomy twice. Imaging analyses showed a mass involving the levator ani muscle apart from the rectum, with lymph node metastases to the right inguinal and internal iliac regions. A biopsy specimen of the right inguinal lymph node revealed poorly differentiated adenocarcinoma. She underwent neoadjuvant chemotherapy according to the treatment strategy of anal fistula cancer. Laparoscopic posterior pelvic exenteration and pelvic lymph node dissection with anterior inguinal node dissection was performed, along with perineal reconstruction. Pathological examination revealed clear cell adenocarcinoma with lymph node metastases, derived from extrapelvic endometriosis in the episiotomy scar. She was treated with adjuvant chemotherapy according to the treatment strategy of vulvar cancer, and showed no evidence of recurrence after 15 months of surgery.

Real-Time insight into in vivo redox status utilizing hyperpolarized [1-13C] N-acetyl cysteine.

Drastic sensitivity enhancement of dynamic nuclear polarization is becoming an increasingly critical methodology to monitor real-time metabolic and physiological information in chemistry, biochemistry, and biomedicine. However, the limited number of available hyperpolarized 13C probes, which can effectively interrogate crucial metabolic activities, remains one of the major bottlenecks in this growing field. Here, we demonstrate [1-13C] N-acetyl cysteine (NAC) as a novel probe for hyperpolarized 13C MRI to monitor glutathione redox chemistry, which plays a central part of metabolic chemistry and strongly influences various therapies. NAC forms a disulfide bond in the presence of reduced glutathione, which generates a spectroscopically detectable product that is separated from the main peak by a 1.5 ppm shift. In vivo hyperpolarized MRI in mice revealed that NAC was broadly distributed throughout the body including the brain. Its biochemical transformation in two human pancreatic tumor cells in vitro and as xenografts differed depending on the individual cellular biochemical profile and microenvironment in vivo. Hyperpolarized NAC can be a promising non-invasive biomarker to monitor in vivo redox status and can be potentially translatable to clinical diagnosis.

Pyrazole-Based Lactate Dehydrogenase Inhibitors with Optimized Cell Activity and Pharmacokinetic Properties.

Lactate dehydrogenase (LDH) catalyzes the conversion of pyruvate to lactate, with concomitant oxidation of reduced nicotinamide adenine dinucleotide as the final step in the glycolytic pathway. Glycolysis plays an important role in the metabolic plasticity of cancer cells and has long been recognized as a potential therapeutic target. Thus, potent, selective inhibitors of LDH represent an attractive therapeutic approach. However, to date, pharmacological agents have failed to achieve significant target engagement in vivo, possibly because the protein is present in cells at very high concentrations. We report herein a lead optimization campaign focused on a pyrazole-based series of compounds, using structure-based design concepts, coupled with optimization of cellular potency, in vitro drug-target residence times, and in vivo PK properties, to identify first-in-class inhibitors that demonstrate LDH inhibition in vivo. The lead compounds, named NCATS-SM1440 (43) and NCATS-SM1441 (52), possess desirable attributes for further studying the effect of in vivo LDH inhibition.

Laparoscopic left hemicolectomy with regional lymph node navigation and intracorporeal anastomosis for splenic flexure colon cancer.

Laparoscopic approaches have become a standard strategy for colon cancer patients who undergo surgical treatment. Complete mesocolic excision (CME) with central vascular ligation (CVL) is the fundamental principle of radical resection of colon cancers. Splenic flexure colon cancer (SFCC) is rare, accounting for less than 4% of all colorectal cancer cases. Moreover, a laparoscopic approach for SFCC following the CME/CVL concept can be challenging because the blood supply of the splenic flexure is derived from either the middle colic artery (MCA) branching from the superior mesenteric artery, the left colic artery (LCA) branching from the inferior mesenteric artery. In addition, approximately one third of SFCC patients have an accessory MCA that can originate from the celiac trunk. Herein, we describe the technical procedure of a laparoscopic left hemicolectomy for SFCC using indocyanine green (ICG) for necessary and sufficient lymphadenectomy followed by intracorporeal anastomosis. Two injections of ICG (0.5 mg/0.2 ml × 2) into the subserosa of the proximal and distal sides of the tumor preceded the surgical procedure after pneumoperitoneum. Near infrared images obtained throughout the laparoscopic procedure helped visualize lymphatic drainage vessels and inform decision making for determining vessels requiring ligation according to the CVL concept: MCA, LCA or accessory MCA. Complete intracorporeal anastomosis following necessary and sufficient lymphadenectomy with ICG can minimize the dissecting area of the laparoscopic left hemicolectomy for SFCC patients. Intravenous ICG injection (2.5 mg) after anastomosis helps confirm blood perfusion at the anastomosis site. Four patients with SFCC underwent a laparoscopic colectomy under ICG navigation in 2019 at our institute. The median operative time was 237 min, the median estimated blood loss was 0 ml, and the median number of dissected lymph nodes was 13. No patients experienced postoperative complications. In conclusion, laparoscopic left hemicolectomy with ICG navigation and intracorporeal anastomosis for SFCC patients may be a feasible option for the radical resection of colon cancer.

Molecular Imaging of the Tumor Microenvironment Reveals the Relationship between Tumor Oxygenation, Glucose Uptake, and Glycolysis in Pancreatic Ductal Adenocarcinoma.

Molecular imaging approaches for metabolic and physiologic imaging of tumors have become important for treatment planning and response monitoring. However, the relationship between the physiologic and metabolic aspects of tumors is not fully understood. Here, we developed new hyperpolarized MRI and electron paramagnetic resonance imaging procedures that allow more direct assessment of tumor glycolysis and oxygenation status quantitatively. We investigated the spatial relationship between hypoxia, glucose uptake, and glycolysis in three human pancreatic ductal adenocarcinoma tumor xenografts with differing physiologic and metabolic characteristics. At the bulk tumor level, there was a strong positive correlation between 18F-FDG-PET and lactate production, while pO2 was inversely related to lactate production and 18F-2-fluoro-2-deoxy-D-glucose (18F-FDG) uptake. However, metabolism was not uniform throughout the tumors, and the whole tumor results masked different localizations that became apparent while imaging. 18F-FDG uptake negatively correlated with pO2 in the center of the tumor and positively correlated with pO2 on the periphery. In contrast to pO2 and 18F-FDG uptake, lactate dehydrogenase activity was distributed relatively evenly throughout the tumor. The heterogeneity revealed by each measure suggests a multimodal molecular imaging approach can improve tumor characterization, potentially leading to better prognostics in cancer treatment. SIGNIFICANCE: Novel multimodal molecular imaging techniques reveal the potential of three interrelated imaging biomarkers to profile the tumor microenvironment and interrelationships of hypoxia, glucose uptake, and glycolysis.

Dynamic Imaging of LDH Inhibition in Tumors Reveals Rapid In Vivo Metabolic Rewiring and Vulnerability to Combination Therapy.

The reliance of many cancers on aerobic glycolysis has stimulated efforts to develop lactate dehydrogenase (LDH) inhibitors. However, despite significant efforts, LDH inhibitors (LDHi) with sufficient specificity and in vivo activity to determine whether LDH is a feasible drug target are lacking. We describe an LDHi with potent, on-target, in vivo activity. Using hyperpolarized magnetic resonance spectroscopic imaging (HP-MRSI), we demonstrate in vivo LDH inhibition in two glycolytic cancer models, MIA PaCa-2 and HT29, and we correlate depth and duration of LDH inhibition with direct anti-tumor activity. HP-MRSI also reveals a metabolic rewiring that occurs in vivo within 30 min of LDH inhibition, wherein pyruvate in a tumor is redirected toward mitochondrial metabolism. Using HP-MRSI, we show that inhibition of mitochondrial complex 1 rapidly redirects tumor pyruvate toward lactate. Inhibition of both mitochondrial complex 1 and LDH suppresses metabolic plasticity, causing metabolic quiescence in vitro and tumor growth inhibition in vivo.

Robot-assisted low anterior resection after aluminum potassium sulfate and tannic acid sclerosing therapy for internal hemorrhoids.

BACKGROUND: Internal hemorrhoids are the most common anal diseases. Aluminum potassium sulfate and tannic acid (ALTA) injection is a new sclerosing therapy for the treatment of internal hemorrhoids. Although ALTA injection has been widely used, there are no previous reports of rectal cancer patients who underwent robot-assisted low anterior resection (Rob-LAR) after ALTA injection to treat internal hemorrhoids. CASE PRESENTATION: A 70-year-old man with rectal cancer was presented to our hospital. He had an ALTA injection 2 months before presentation at a clinic due to hematochezia with internal hemorrhoids. The rectal tumor was located 7 cm above the anal verge, and Rob-LAR with the da Vinci Xi system was performed. The patient had sclerosis on the stump of the anal side, which made it difficult to transect the rectum with linear staplers. This required multiple repeats of compression through the SmartClamp feedback. After anastomosis with the double-stapling technique, we constructed a diverting ileostomy. CONCLUSION: Although ALTA injection is a promising strategy for internal hemorrhoids, rectal cancer should be excluded before the sclerosing therapy.

Targeting Glycolysis through Inhibition of Lactate Dehydrogenase Impairs Tumor Growth in Preclinical Models of Ewing Sarcoma.

Altered cellular metabolism, including an increased dependence on aerobic glycolysis, is a hallmark of cancer. Despite the fact that this observation was first made nearly a century ago, effective therapeutic targeting of glycolysis in cancer has remained elusive. One potentially promising approach involves targeting the glycolytic enzyme lactate dehydrogenase (LDH), which is overexpressed and plays a critical role in several cancers. Here, we used a novel class of LDH inhibitors to demonstrate, for the first time, that Ewing sarcoma cells are exquisitely sensitive to inhibition of LDH. EWS-FLI1, the oncogenic driver of Ewing sarcoma, regulated LDH A (LDHA) expression. Genetic depletion of LDHA inhibited proliferation of Ewing sarcoma cells and induced apoptosis, phenocopying pharmacologic inhibition of LDH. LDH inhibitors affected Ewing sarcoma cell viability both in vitro and in vivo by reducing glycolysis. Intravenous administration of LDH inhibitors resulted in the greatest intratumoral drug accumulation, inducing tumor cell death and reducing tumor growth. The major dose-limiting toxicity observed was hemolysis, indicating that a narrow therapeutic window exists for these compounds. Taken together, these data suggest that targeting glycolysis through inhibition of LDH should be further investigated as a potential therapeutic approach for cancers such as Ewing sarcoma that exhibit oncogene-dependent expression of LDH and increased glycolysis. SIGNIFICANCE: LDHA is a pharmacologically tractable EWS-FLI1 transcriptional target that regulates the glycolytic dependence of Ewing sarcoma.

Imaging of glucose metabolism by 13C-MRI distinguishes pancreatic cancer subtypes in mice.

Metabolic differences among and within tumors can be an important determinant in cancer treatment outcome. However, methods for determining these differences non-invasively in vivo is lacking. Using pancreatic ductal adenocarcinoma as a model, we demonstrate that tumor xenografts with a similar genetic background can be distinguished by their differing rates of the metabolism of 13C labeled glucose tracers, which can be imaged without hyperpolarization by using newly developed techniques for noise suppression. Using this method, cancer subtypes that appeared to have similar metabolic profiles based on steady state metabolic measurement can be distinguished from each other. The metabolic maps from 13C-glucose imaging localized lactate production and overall glucose metabolism to different regions of some tumors. Such tumor heterogeneity would not be not detectable in FDG-PET.

Identification of high-risk drugs related to chemotherapy-induced peripheral neuropathy in Cancer Therapy Evaluation Program-sponsored phase I trials.

BACKGROUND: Chemotherapy-induced peripheral neuropathy (CIPN) is a significant and debilitating side effect. However, there have been no studies of the relative risk of CIPN with known causative agents. We examined the risk of CIPN in patients taking such agents as a part of the National Cancer Institute (NCI) Cancer Therapy Evaluation Program-sponsored phase I trials. METHODS: CIPN events in each patient were graded according to the Clinical Terminology of Common Adverse Effects and compared among several high-risk chemotherapeutic agent groups, adjusting for possible confounding factors. Patients receiving tubulin-targeted agents were analysed separately for specific background factors associated with CIPN. RESULTS: In 135 phase I clinical trials, 259 of 3614 patients were identified as developing CIPN during chemotherapy. Tubulin-targeting agents and proteasome inhibitors were identified as high-risk agents (hazard ratio 9.04 and 5.01, respectively) for CIPN, whereas platinum-complex agents and thalidomide analogues imparted lower risk (hazard ratio 1.52 and 1.11, respectively). Age, sex and medical history of diabetes were not significantly related to CIPN. CIPN developed over time as the number of chemotherapy cycles increased. Among patients with CIPN, treatment with tubulin-targeting agents resulted in a significantly higher rate of chemotherapy schedule modification compared with treatments with other chemotherapeutic agents. CONCLUSIONS: Tubulin-targeting agents and proteasome inhibitors were associated with a greatly increased risk of CIPN compared with other agents. CIPN tended to develop in later chemotherapy cycles. These findings will help to minimise the risk of CIPN by encouraging increased surveillance and earlier dose adjustment of high-risk agents in phase I trials.

Dynamic Imaging of Glucose and Lactate Metabolism by 13C-MRS without Hyperpolarization.

Metabolic reprogramming is one of the defining features of cancer and abnormal metabolism is associated with many other pathologies. Molecular imaging techniques capable of detecting such changes have become essential for cancer diagnosis, treatment planning, and surveillance. In particular, 18F-FDG (fluorodeoxyglucose) PET has emerged as an essential imaging modality for cancer because of its unique ability to detect a disturbed molecular pathway through measurements of glucose uptake. However, FDG-PET has limitations that restrict its usefulness in certain situations and the information gained is limited to glucose uptake only.13C magnetic resonance spectroscopy theoretically has certain advantages over FDG-PET, but its inherent low sensitivity has restricted its use mostly to single voxel measurements unless dissolution dynamic nuclear polarization (dDNP) is used to increase the signal, which brings additional complications for clinical use. We show here a new method of imaging glucose metabolism in vivo by MRI chemical shift imaging (CSI) experiments that relies on a simple, but robust and efficient, post-processing procedure by the higher dimensional analog of singular value decomposition, tensor decomposition. Using this procedure, we achieve an order of magnitude increase in signal to noise in both dDNP and non-hyperpolarized non-localized experiments without sacrificing accuracy. In CSI experiments an approximately 30-fold increase was observed, enough that the glucose to lactate conversion indicative of the Warburg effect can be imaged without hyper-polarization with a time resolution of 12s and an overall spatial resolution that compares favorably to 18F-FDG PET.

Direct and indirect assessment of cancer metabolism explored by MRI.

Magnetic resonance-based approaches to obtain metabolic information on cancer have been explored for decades. Electron paramagnetic resonance (EPR) has been developed to pursue metabolic profiling and successfully used to monitor several physiologic parameters such as pO2 , pH, and redox status. All these parameters are associated with pathophysiology of various diseases. Especially in oncology, cancer hypoxia has been intensively studied because of its relationship with metabolic alterations, acquiring treatment resistance, or a malignant phenotype. Thus, pO2 imaging leads to an indirect metabolic assessment in this regard. Proton electron double-resonance imaging (PEDRI) is an imaging technique to visualize EPR by using the Overhauser effect. Most biological parameters assessed in EPR can be visualized using PEDRI. However, EPR and PEDRI have not been evaluated sufficiently for clinical application due to limitations such as toxicity of the probes or high specific absorption rate. Hyperpolarized (HP) 13 C MRI is a novel imaging technique that can directly visualize the metabolic profile. Production of metabolites of the HP 13 C probe delivered to target tissue are evaluated in this modality. Unlike EPR or PEDRI, which require the injection of radical probes, 13 C MRI requires a probe that can be physiologically metabolized and efficiently hyperpolarized. Among several methods for hyperpolarizing probes, dissolution dynamic nuclear hyperpolarization is a widely used technique for in vivo imaging. Pyruvate is the most suitable probe for HP 13 C MRI because it is part of the glycolytic pathway and the high efficiency of pyruvate-to-lactate conversion is a distinguishing feature of cancer. Its clinical applicability also makes it a promising metabolic imaging modality. Here, we summarize the applications of these indirect and direct MR-based metabolic assessments focusing on pO2 and pyruvate-to-lactate conversion. The two parameters are strongly associated with each other, hence the acquired information is potentially interchangeable when evaluating treatment response to oxygen-dependent cancer therapies.

Targeting the Hsp40/Hsp70 Chaperone Axis as a Novel Strategy to Treat Castration-Resistant Prostate Cancer.

Castration-resistant prostate cancer (CRPC) is characterized by reactivation of androgen receptor (AR) signaling, in part by elevated expression of AR splice variants (ARv) including ARv7, a constitutively active, ligand binding domain (LBD)-deficient variant whose expression has been correlated with therapeutic resistance and poor prognosis. In a screen to identify small-molecule dual inhibitors of both androgen-dependent and androgen-independent AR gene signatures, we identified the chalcone C86. Binding studies using purified proteins and CRPC cell lysates revealed C86 to interact with Hsp40. Pull-down studies using biotinylated-C86 found Hsp40 present in a multiprotein complex with full-length (FL-) AR, ARv7, and Hsp70 in CRPC cells. Treatment of CRPC cells with C86 or the allosteric Hsp70 inhibitor JG98 resulted in rapid protein destabilization of both FL-AR and ARv, including ARv7, concomitant with reduced FL-AR- and ARv7-mediated transcriptional activity. The glucocorticoid receptor, whose elevated expression in a subset of CRPC also leads to androgen-independent AR target gene transcription, was also destabilized by inhibition of Hsp40 or Hsp70. In vivo, Hsp40 or Hsp70 inhibition demonstrated single-agent and combinatorial activity in a 22Rv1 CRPC xenograft model. These data reveal that, in addition to recognized roles of Hsp40 and Hsp70 in FL-AR LBD remodeling, ARv lacking the LBD remain dependent on molecular chaperones for stability and function. Our findings highlight the feasibility and potential benefit of targeting the Hsp40/Hsp70 chaperone axis to treat prostate cancer that has become resistant to standard antiandrogen therapy.Significance: These findings highlight the feasibility of targeting the Hsp40/Hsp70 chaperone axis to treat CRPC that has become resistant to standard antiandrogen therapy. Cancer Res; 78(14); 4022-35. ©2018 AACR.

Wireless implantable coil with parametric amplification for in vivo electron paramagnetic resonance oximetric applications.

PURPOSE: To develop an implantable wireless coil with parametric amplification capabilities for time-domain electron paramagnetic resonance (EPR) spectroscopy operating at 300 MHz. METHODS: The wireless coil and lithium phthalocyanine (LiPc), a solid paramagnetic probe, were each embedded individually in a biocompatible polymer polydimethoxysiloxane (PDMS). EPR signals from the LiPc embedded in PDMS (LiPc/PDMS) were generated by a transmit-receive surface coil tuned to 300 MHz. Parametric amplification was configured with an external pumping coil tuned to 600 MHz and placed between the surface coil resonator and the wireless coil. RESULTS: Phantom studies showed significant enhancement in signal to noise using the pumping coil. However, no influence of the pumping coil on the oxygen-dependent EPR spectral linewidth of LiPc/PDMS was observed, suggesting the validity of parametric amplification of EPR signals for oximetry by implantation of the encapsulated wireless coil and LiPc/PDMS in deep regions of live objects. In vivo studies demonstrate the feasibility of this approach to longitudinally monitor tissue pO2 in vivo and also monitor acute changes in response to pharmacologic challenges. The encapsulated wireless coil and LiPc/PDMS engendered no host immune response when implanted for ∼3 weeks and were found to be well tolerated. CONCLUSIONS: This approach may find applications for monitoring tissue oxygenation to better understand the pathophysiology associated with wound healing, organ transplantation, and ischemic diseases.

Molecular imaging of tumor photoimmunotherapy: Evidence of photosensitized tumor necrosis and hemodynamic changes.

Near-infrared photoimmunotherapy (NIR PIT) employs the photoabsorbing dye IR700 conjugated to antibodies specific for cell surface epidermal growth factor receptor (EGFR). NIR PIT has shown highly selective cytotoxicity in vitro and in vivo. Cell necrosis is thought to be the main mode of cytotoxicity based mainly on in vitro studies. To better understand the acute effects of NIR PIT, molecular imaging studies were performed to assess its cellular and vascular effects. In addition to in vitro studies for cytotoxicity of NIR PIT, the in vivo tumoricidal effects and hemodynamic changes induced by NIR PIT were evaluated by 13C MRI using hyperpolarized [1,4-13C2] fumarate, R2* mapping from T2*-weighted MRI, and photoacoustic imaging. In vitro studies confirmed that NIR PIT resulted in rapid cell death via membrane damage, with evidence for rapid cell expansion followed by membrane rupture. Following NIR PIT, metabolic MRI using hyperpolarized fumarate showed the production of malate in EGFR-expressing A431 tumor xenografts, providing direct evidence for photosensitized tumor necrosis induced by NIR PIT. R2* mapping studies showed temporal changes in oxygenation, with an accompanying increase of deoxyhemoglobin at the start of light exposure followed by a sustained decrease after cessation of light exposure. This result suggests a rapid decrease of blood flow in EGFR-expressing A431 tumor xenografts, which is supported by the results of the photoacoustic imaging experiments. Our findings suggest NIR PIT mediates necrosis and hemodynamic changes in tumors by photosensitized oxidation pathways and that these imaging modalities, once translated, may be useful in monitoring clinical treatment response.