Inhibition of Akt reverses the acquired resistance to sorafenib by switching protective autophagy to autophagic cell death in hepatocellular carcinoma

Sorafenib is the standard first-line systemic drug for advanced hepatocellular carcinoma (HCC), but the acquired resistance to sorafenib results in limited benefits. Activation of Akt is thought to be responsible for mediating the acquired resistance to sorafenib. The present study aims to examine the underlying mechanism and seek potential strategies to reverse this resistance. Two sorafenib-resistant HCC cell lines, which had been established from human HCC HepG2 and Huh7 cells, were refractory to sorafenib-induced growth inhibition and apoptosis in vitro and in vivo. Sustained exposure to sorafenib activated Akt via the feedback loop of mTOR but independent of protein phosphatase 2A in HCC cells. Autophagy participated in the resistance to sorafenib as inhibition of autophagy reduced the sensitivity of sorafenib-resistant HCC cells to sorafenib, whereas activation of autophagy by rapamycin had the opposite effect. However, rapamycin did not show a synergistic effect with sorafenib to inhibit cell proliferation, while it also activated Akt via a feedback mechanism in sorafenib-resistant HCC cells. Inhibition of Akt reversed the acquired resistance to sorafenib by switching autophagy from a cytoprotective role to a death-promoting mechanism in the sorafenib-resistant HCC cells. Akt inhibition by GDC0068 synergized with sorafenib to suppress the growth of sorafenib-resistant HCC tumors that possessed the sorafenib-resistant feature in vivo. The results have provided evidence for clinical investigation of GDC0068, a novel ATP-competitive pan-Akt inhibitor, as the second-line treatment after the failure of sorafenib-medicated molecular targeted therapy for advanced HCC.

Cardiovascular toxicity of different sizes amorphous silica nanoparticles in rats after intratracheal instillation

The purpose of this work was to investigate the cardiovascular toxicity of different sizes and different dosages of silica nanoparticles in Wistar rats. The three silica nanoparticles (30, 60, and 90 nm) and one fine silica particles (600 nm) at three doses of 2, 5, and 10 (mg/Kg bw) were used in the present experiment. After intratracheal instillation for a total of 16 times, concentration of Si in hearts and serum was measured by inductively coupled plasma optical emission spectrometer. The hematology parameters were analyzed by an automated hematology analyzer, and the inflammatory reaction, oxidative stress, endothelial dysfunction, and the myocardial enzymes in serum were measured by kits. Our results showed intratracheal-instilled silica nanoparticles could pass through the alveolar-capillary barrier into systemic circulation. Concentration of Si in the heart and serum depended on the particles size and dosage. The levels of reactive oxygen species (ROS) at 5, 10 mg/Kg bw of the three silica nanoparticles were higher than the fine silica particles. Blood levels of inflammation-related high-sensitivity C-reactive protein and cytokines such as interleukin-1beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha were increased after exposure to three silica nanoparticles at 10 mg/Kg bw. Moreover, the levels of IL-1β and IL-6 at 10 mg/Kg bw of silica nanoparticles (30 nm) were higher than the fine silica particles. Significant decrease in superoxide dismutase, glutathione peroxidase and significant increase in malondialdehyde were observed at 10 mg/Kg bw of the three silica nanoparticles. A significant decrease in nitric oxide (NO) production was induced which coincided with the reduction of nitric oxide synthase (NOS) activity and the excessive generation of ROS in rats. The levels of intercellular adhesion molecule-l and vascular cell adhesion molecule-l elevated significantly after exposure to three silica nanoparticles at 10 mg/Kg bw, which are considered as early steps of endothelial dysfunction. We conclude that cardiovascular toxicity of silica nanoparticles could be related to the particles size and dosage. Oxidative stress could be involved in inflammatory reaction and endothelial dysfunction, all of which could aggravate cardiovascular toxicology. In addition, endothelial NO/NOS system disorder caused by nanoparticles could be one of the mechanisms for endothelial dysfunction.

Where is the comfort in comfort foods? Mechanisms linking fat signaling, reward, and emotion

BACKGROUND

Food in general, and fatty foods in particular, have obtained intrinsic reward value throughout evolution. This reward value results from an interaction between exteroceptive signals from different sensory modalities, interoceptive hunger/satiety signals from the gastrointestinal tract to the brain, as well as ongoing affective and cognitive processes. Further evidence linking food to emotions stems from folk psychology ('comfort foods') and epidemiological studies demonstrating high comorbidity rates between disorders of food intake, including obesity, and mood disorders such as depression.

PURPOSE

This review paper aims to give an overview of current knowledge on the neurophysiological mechanisms underlying the link between (fatty) foods, their reward value, and emotional responses to (anticipation of) their intake in humans. Firstly, the influence of exteroceptive sensory signals, including visual, olfactory ('anticipatory food reward'), and gustatory ('consummatory food reward'), on the encoding of reward value in the (ventral) striatum and of subjective pleasantness in the cingulate and orbitofrontal cortex will be discussed. Differences in these pathways and mechanisms between lean and obese subjects will be highlighted. Secondly, recent studies elucidating the mechanisms of purely interoceptive fatty acid-induced signaling from the gastrointestinal tract to the brain, including the role of gut peptides, will be presented. These studies have demonstrated that such subliminal interoceptive stimuli may impact on hedonic circuits in the brain, and thereby influence the subjective and neural responses to negative emotion induction. This suggests that the effect of foods on mood may even occur independently from their exteroceptive sensory properties.

Upregulation of HIF-2α induced by sorafenib contributes to the resistance by activating the TGF-α/EGFR pathway in hepatocellular carcinoma cells

Sorafenib, the first-line systemic drug for advanced hepatocellular carcinoma (HCC), has demonstrated limited benefits with very low response rates. Thus it is essential to investigate the underlying mechanisms for the resistance to sorafenib and seek potential strategy to enhance its efficacy. Hypoxic cells inside solid tumors are extremely resistant to therapies as their survival ability is increased due to the cellular adaptive response to hypoxia, which is controlled by hypoxia-inducible factor (HIF)-1 and HIF-2. Sorafenib inhibits HIF-1α synthesis, making the hypoxic response switch from HIF-1α- to HIF-2α-dependent pathways and providing a mechanism for more aggressive growth of tumors. The present study has demonstrated that upregulation of HIF-2α induced by sorafenib contributes to the resistance of hypoxic HCC cells by activating the transforming growth factor (TGF)-α/epidermal growth factor receptor (EGFR) pathway. Blocking the TGF-α/EGFR pathway by gefitinib, a specific EGFR inhibitor, reduced the activation of STAT (signal transducer and activator of transcription) 3, AKT and ERK (extracellular signal-regulated kinase), and synergized with sorafenib to inhibit proliferation and induce apoptosis of hypoxic HCC cells. Transfection of HIF-2α siRNA into HCC cells downregulated the expression of VEGF (vascular endothelial growth factor), cyclin D1, HIF-2α and TGF-α, and inhibited the activation of EGFR. HIF-2α siRNA inhibited the proliferation and promoted the apoptosis of HCC cells in vitro, and synergized with sorafenib to suppress the growth of HCC tumors in vivo. The results indicate that targeting HIF-2α-mediated activation of the TGF-α/EGFR pathway warrants further investigation as a potential strategy to enhance the efficacy of sorafenib for treating HCC.

Stro-1-positive human mesenchymal stem cells prolong skin graft survival in mice

BACKGROUND

Human mesenchymal stem cells (MSCs) and its stromal cell antigen 1 Stro-1 positive (Stro-1(+)) subgroup possess immunosuppressive properties. Our objective was to evaluate the in vivo inhibitory effect of MSCs and the Stro-1 subset.

METHODS

Isolated human MSCs from bone marrow-derived mononuclear cells of healthy adults, and Stro-1(+) cells were cultured before sorting. Female C57BL/6 mice and female BALB/c mice were used as donors and recipients in an allogeneic skin graft model, respectively. The recipients were divided randomly into 4 groups: (1) The Stro-1(+) MSCs group received 2 × 10(6) Stro-1(+) MSCs injected into irradiated recipients before skin grafting. (2) The MSC group (2 × 10(6)) injected into the irradiated recipient mice before skin grafting. (3) The irradiated control group just irradiated before skin grafting. (4) The syngenic control group included irradiated BALB/c mice that received skin from syngenic mice. The main data included skin graft survival times, histologic changes on hematoxylin and eosin (HE) staining and plasma transforming growth factor (TGF)-β concentrations in recipients measured by enzyme-linked immunosorbent assay (ELISA) before and after transplantation.

RESULTS

The skin graft survival time in the MSCs group (12.13 ± 3.34 days) was not significantly prolonged versus the irradiated controls (11.38 ± 1.01 days), but it was notably prolonged among the Stro-1(+) MSCs group (30.68 ± 5.89 days) compared with the irradiated control and the MSCs groups, respectively. The histology of skin grafts among the stro-1(+) group showed a clear structure. After grafting, plasma TGF-β concentrations were almost the same as before transplantation among the irradiated and the syngenic controls but significantly increased in the MSCs and Stro-1(+) MSCs groups.

CONCLUSIONS

Stro-1(+) MSCs induced greater prolongation of skin grafts in mice than unsorted MSCs; however, TGF-β expression did not contribute to this effect.

First Report of Corynespora Leaf Spot Caused by C. cassiicola on Golden Vicary Privet (Ligustrum × vicaryi) in China

Golden vicary privet (Ligustrum × vicaryi Rehd.), a hybrid between L. ovalifolium 'Aureum' Rehd. and L. vulgare L., is widely used as a landscape shrub for horticultural ornamentation. From 2009 to 2011, a leaf spot disease of L. × vicaryi was observed in the parks in Luoyang, Henan Province, China. Lesions were initially brown and punctiform, and with age the lesions turned into elliptic, subcircular to irregular and pale brown, faintly zonate, and depressed. Fully mature lesions were mostly irregular to circular, 5 to 15 mm in diameter, centers tan to dark brown, with reddish brown to reddish purple margins of varying width. The disease eventually caused substantial premature defoliation. After infected leaves were collected from parks and maintained in a humid atmosphere, a layer of black mold developed on the surface of the lesions. Conidiophores were cylindrical, straight to slightly curved, brown, unbranched (2 to 7 septa), and were 98.5 to 403.9 μm in length, 4.5 to 6.6 μm in width. Conidia were solitary or in short chains containing two to five spores, and were cylindrical or obclavate, straight or flexuose (3 to 19 pseudosepta), pale olivaceous brown or brown when mature, and were 78.8 to 315.2 μm in length by 5.3 to 12.3 μm in width. Morphological characteristics of the fungus were similar to those of Corynespora cassiicola (Berk. & Curt.) Wei (1). Lesions on leaves were excised, surface sterilized, and plated on potato dextrose agar (PDA) and incubated at 25°C for 2 to 3 days. A fungus was isolated from the lesions, and pure isolates that were obtained after from single spored isolates were cultured on PDA. Colonies on PDA formed concentric growth rings, abundant aerial mycelia, and were grey or dark brown in color. The isolate ST1 was selected as a representative for molecular identification. The ITS1-5.8S-ITS2 region of the isolate was amplified by PCR with primers ITS1/ITS4 (3) and sequenced. BLAST analysis of the 559 bp amplicon (GenBank Accession No. KC138855) indicated 100% sequence similarity with C. cassiicola (GU138988) (2). To validate Koch's postulates, pathogenicity tests were performed by spraying leaves of five healthy potted L. vicaryi with a 10⁶ conidia per ml aqueous suspension. Control plants were inoculated with sterile water. Plants were covered with plastic bags for 24 h after inoculation and maintained at 25°C. After 3 days, all inoculated plants showed typical symptoms, whereas water sprayed controls remained healthy. C. cassiicola was consistently reisolated from these lesions. The reisolated conidia showed the same morphological characteristics as described above. To our knowledge, this is the first report of leaf spot caused by C. cassiicola on L. × vicaryi in China. Its confirmation is a significant step toward management recommendations for growers. References: (1) M. B. Ellis et al. Corynespora cassiicola. CMI Descriptions of Pathogenic Fungi and Bacteria, no. 303. Commonwealth Mycological Institute, Kew, UK, 1971. (2) X. B. Liu et al. Plant Dis. 94:916, 2010. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

First Report of Branch Blight of Tree Peony Caused by Phoma glomerata in China

Tree peony (Paeonia suffruticosa Andrews) is a perennial woody deciduous shrub native to China and famous for its beautiful flowers. Starting in early autumn 2010, blighted branches of tree peony were detected in the International Peony Garden in Luoyang. The disease incidence was greater than 10% and disease symptoms included bulb atrophy and twig and branch dieback. Pycnidia were embedded within the bark of diseased branches. They were small, black, ostiolate, and measured 145 to 275 × 140 to 251 μm. Pycnoconidia were single-celled, hyaline or sandy beige, rounded to ellipsoidal, and 3.9 to 10.3 × 2.3 to 7.0 μm. Pure cultures were obtained by plating the pycnoconidia on potato dextrose agar (PDA). In culture, the fungus produced a circular, white to pink colony with pyknotic and linter shaped aerial mycelium. Numerous pycnidia, initially brown and dark at maturity, were embedded in the mycelium, especially in the center of the colony, with a few of them scattered in the edge. The morphological characteristics were consistent with Phoma (2). The ITS1-5.8S-ITS2 region of three isolates were PCR amplified and sequenced with primers ITS1 and ITS4. Sequences (GenBank Accession No. JX885584) showed 99% identity with reference isolates of Peyronellaea glomerata (Corda) Goid (AB470906.1 and HQ380779.1) and Phoma glomerata (Corda) Wollenw. & Hochapfel (EU098115.1). These two species are synonyms (1). To test pathogenicity, nine healthy branches of 3-year-old potted tree peony plants were wound-inoculated with a PDA disk containing pycnidia from an actively growing colony of P. glomerata. Three control branches were inoculated with sterile PDA disks. Each inoculated branch was wrapped in a plastic bag and maintained in a greenhouse at 25 to 28°C. After 3 days, brown patches appeared on inoculated branches and extended by up to 1 cm. Pycnidia identical to those observed in the field and in storage appeared on all inoculated branches 7 days after inoculation. Control branches did not show symptoms. The pathogen was reisolated from inoculated branches, fulfilling Koch's postulates. P. glomerata was reported as the causal agent of withering of flowers and young shoots of grapevines in Yugoslavia (3). To our knowledge, P. glomerata and Botryosphaeria dothidea have always been reported together, causing branch wilting or dieback. To our knowledge, this is the first report of branch blight of tree peony caused by P. glomerata in China. References: (1) M. M. Aveskamp et al. Mycol. Soc. Am. 101:363, 2009. (2) G. H. Boerema et al. Studies in Mycology, 3, 1973. (3) A. Šaric-Sabadoš et al. Atti Ist. bot. Univ. Pavia 18:101, 1960.

Successful use of aromatase inhibitor letrozole in NOA with an elevated FSH level: a case report

Aromatase inhibitors inhibit the conversion of testosterone to oestrogens and could reduce serum oestradiol concentrations. Letrozole is one of aromatase inhibitors frequently used in treatment of men with oligospermia. We present the case of an infertile man with small testes and an elevated FSH level, which was diagnosed as NOA, hypospermatogenesis proven by testicular biopsy. After taking letrozole for 3 months, semen analyses by computer-aided sperm analysis present that this man had normal spermatogenesis. This is the first case report of the activation of spermatogenesis, in man who was NOA with elevated FSH level, resulting from the use of the one of aromatase inhibitors.

Blood glucose fluctuation affects skin collagen metabolism in the diabetic mouse by inhibiting the mitogen-activated protein kinase and Smad pathways

BACKGROUND

We recently reported that in mice, blood glucose fluctuations (BGF) produced more detrimental effects on skin structure and function than did diabetes alone.

AIM

To determine whether treatment of BGF changes the collagen metabolism in the skin of diabetic mice, and to explore its possible molecular mechanism further.

METHODS

The study used diabetic and BGF animal models. Immunohistochemistry, western blotting and real-time PCR analysis were used to detect the expression of type I collagen, matrix metalloproteinase (MMP)-1, MMP-2 and MMP-13, tissue inhibitor of metalloproteinase (TIMP)-1, extracellular signal-regulated kinase, p38, and Smad2/3. The activities of mitogen-activated protein kinase (MAPK) and Smad signal molecules were also detected by western blotting, and the skin fibroblast ultrastructure was examined using an electron microscope.

RESULTS

BGF treatment produced a twofold reduction in type I collagen synthesis compared with diabetes-only mice. Expression of MMP-1, MMP-2 and MMP-13 increased markedly in the BGF-treated mice, but TIMP-1 expression was strongly downregulated by the BGF treatment. There was also evidence of higher levels of apoptosis of skin fibroblasts after BGF treatment.

CONCLUSIONS

BGF treatment can affect collagen production in the skin of diabetic BGF mice by inhibiting collagen synthesis and increasing collagen degradation. Furthermore, both MAPK and Smad signalling pathways seem to play a role in the inhibition of collagen production in diabetic mice treated with BGF.

Predictive value of ankle-brachial index and blood glucose on the outcomes of six-year all-cause mortality and cardiovascular mortality in a Chinese population of type 2 diabetes patients

AIM

The aim of this paper was to investigate the predictive value of ankle-brachial index (ABI) and blood glucose to estimate mortality in Chinese type 2 diabetes patients.

METHODS

Chinese type 2 diabetes patients (1706 subjects) were followed up for about 6 years,

RESULTS

One thousand four hundred fourteen were included in the final statistical analysis during a median follow-up of 69 months. Overall, 398 patients died during follow-up and 254 deaths were attributable to cardiovascular disease (CVD). Relative risks of all-cause and CVD mortality of patients with ABI≤0.4 were increased by 2.073-fold (95% CI: 1.236-3.478) and 3.086-fold (95% CI: 1.702-5.595), compared with those of patients with ABI>1.0 and ≤1.4. Mortality was significantly increased with increasing plasma glucose and decreasing ABI. All-cause and CVD mortality was the highest (55.6% and 44.4%) with ABI≤0.4 and plasma glucose >10 mmol/L simultaneously. Relative risks of all-cause and CVD mortality in these patients were increased by 3.905-fold (95% CI: 1.334-11.431) and 3.771-fold (95% CI: 1.079-13.171), compared with patients with ABI>1.0 and ≤1.4, and plasma glucose ≤6 mmol/L simultaneously. Models to evaluate additional predictive value of ABI for mortality of type 2 diabetes patients suggested that addition of ABI significantly improved the prediction of the death rate compared with the model including conventional risk factors only.

CONCLUSION

High plasma glucose and low ABI had synergistic effects on increasing mortality of type 2 diabetes patients. The addition of ABI can significantly improve the prediction of mortality compared to protocol using conventional risk factors only.

A model of isolated, vascular whole thymus transplantation in nude rats

BACKGROUND

We used a model of vascularized thymus lobes as a whole isolated organ transplantation in rats.

MATERIALS AND METHODS

Male Fisher rats (F344, RT11v1; n = 10) and male homozygous Rowett nude rats (rnu/rnu; n = 10) were used as donors and recipients, respectively. Both vascular lobes of the thymus as a whole isolated organ were heterotopically transplanted to the neck of recipients. The right common carotid artery of the donor thymus was anastomosed end-to-end to the homonymous artery of the recipient. The anterior vena cava and the left brachiocephalic vein of the donor thymus were anastomosed end-to-side to the right and left external jugular veins of the recipient, respectively. Histological examination was used to monitor graft viability; graft function was assessed using flow cytometry (FCM) and immunologic effects by skin grafts in vivo.

RESULTS

All recipients survived. Preparation of the donors and recipients took 35.6 ± 5.5 minutes and 60.3 ± 15.1 minutes, respectively. The blood supply to the thymus graft was patent. Histology of the thymus on postoperative days 14, 56, and 112 revealed viable grafts with preserved microarchitecture. FCM analysis showed 37.18 ± 11.1% CD3+ T cells at day 21 after transplantation. Skin grafts from F344 and Rowett rats survived 8-10 and more than 30 days, respectively, whereas all third-party Sprague Dawley grafts were rejected within 5 days.

CONCLUSION

We developed a novel model of isolated, direct vascularized whole thymus transplantation in nude rats, in which both lobes of the fully vascularized thymus were harvested en bloc for successful transplantation.

Morphology and volatile compounds of metathoracic scent gland in Tessaratoma papillosa (Drury) (Hemiptera: Tessaratomidae)

Tessaratoma papillosa (Drury) (Hemiptera: Tessaratomidae) is a serious insect pest of litchi and longan in South China. When disturbed, this insect could release large quantities of disagreeable odorous volatiles from its scent gland. Knowledge on the scent gland and its secretion is crucial for developing the semiochemical methods to manage this pest. Morphology and ultrastructure of the metathoracic scent glands (MTGs) were studied under stereo and scanning electron microscopy, and the volatile compounds of MTGs from both male and female T. papillosa were analyzed with coupled gas chromatography-mass spectrometry (GC-MS). The MTG complex is located between the metathorax and the first abdominal segment at the ventral surface of the insect, which has a well-developed single double valve cystic-shaped orange median reservoir, paired colorless lateral glands in both sides, and a long and wavy tubular accessory gland that inlays tightly into the ventral edge around the median reservoir. The MTG opens to the body surface through paired ostioles located between the meso- and metacoxae of the evaporatorium with mushroom bodies. The GC-MS analyses showed that female and male adults have nine major volatile components in common. Tridecane is the most abundant in both females and males, reaching up to 47.1% and 51.8% of relative amount, respectively. The minor component is benzophenone with only 0.28% and 0.14%. Furthermore, undecane, tetradecane, 3-methyl-tridecane, and cyclopentadecane were found only in males. The possible function of volatile compounds of MTG contents in T. papillosa is addressed.

SU-E-T-06: A Mathematical Explanation to Tumor's Response to Perfusion and Hypoxic Fraction after Radiation

PURPOSE

To develop a dynamic model that explains oxygen dynamics between the microvascular perfusion and the hypoxic cell population inside a tumor.

METHODS

Bussink et al (Radiat Res 153(4), p.398 (2000)) observed fast oxygen dynamics, faster than cell-death. Based on a simplified three-compartment-model: the microvasculature, well-oxygenated, and hypoxic tumor cell populations. We applied a first-order differential model for the tumor's transient response as a function of oxygen content within the blood vessels. The sink terms in our model for each compartment are fast changing parameters because radiation rapidly changes the oxygen consumption of the tumor cell in a time scale which is much faster than the population changes of the tumor. Transportation balance condition is also applied for each compartment.

RESULTS

Our simulation results can explain the experimental data in Bussink et al's (Radiat Res 153(4), p.398 (2000)) paper. We provide an explanation for the relative complex behavior of the microvascular perfusion after radiation that emphasizes the role of dynamic metabolic changes in addition to population changes.

CONCLUSIONS

A newly developed dynamic model leads our understanding to the interrelationship between microvascular oxygen content within the blood vessels and the hypoxia state of the tumor to a deeper level, which has the potential to provide the theoretical foundation for the patient' specific adaptive radiotherapy.

SU-E-J-197: A Novel Optical Interstitial Fiber Spectroscopic System for Real-Time Tissue Micro-Vascular Hemodynamics Monitoring

PURPOSE

To demonstrate a novel interstitial optical fiber spectroscopic system, based on diffuse optical spectroscopies with spectral fitting, for the simultaneous monitoring of tumor blood volume and oxygen tension. The technique provides real-time, minimally-invasive and quantification of tissue micro-vascular hemodynamics.

METHODS

An optical fiber prototype probe characterizesthe optical transport in tissue between two large Numerical Aperture (NA) fibers of 200μm core diameter (BFH37-200, ThorLabs) spaced 3-mm apart. Two 21-Ga medical needles are used to protect fiber ends and to facilitate tissue penetration with minimum local blunt trauma in nude mice with xenografts. A 20W white light source (HL-2000-HP, Ocean Optics) is coupled to one fiber with SMA adapter. The other fiber is used to collect light, which is coupled into the spectrometer (QE65000 with Spectrasuite Operating software and OmniDriver, Ocean Optics). The wavelength response of the probe depends on the wavelength dependence of the light source, and of the light signal collection that includes considerable scatter, modeled with Monte-Carlo techniques (S. Jacques 2010 J. of Innov. Opt. Health Sci. 2 123-9). Measured spectra of tissue are normalized by a measured spectrum of a white standard, yielding the transmission spectrum. A head-and-neck xenograft on the flank of a live mouse is used for development.

RESULTS

The optical fiber probe delivers and collects light at an arbitrary depth in the tumor. By spectral fitting of the measured transmission spectrum, an analysis of blood volume and oxygen tension is obtained from the fitting parameters in real time.

CONCLUSIONS

A newly developed optical fiber spectroscopic system with an optical fiber probe takes spectroscopic techniques to a much deeper level in a tumor, which has potential applications for real-time monitoring hypoxic cell population dynamics for an eventual adaptive therapy metric of particular use in hypofractionated radiotherapy.

SU-E-J-196: In-Vivo Tumor Blood-Oxygen Content Measurement via Interstitial Optical Transmission Spectroscopy

PURPOSE

To demonstrate the application of in-vivo diffuse optical transmission spectroscopy in quantifying oxygen saturation in interstitial tissue, and to use this technique to examine reoxygenation dynamics in real-time as tumors responds to radiotherapy.

METHODS

Two 200 micron core fiber optics were threaded through two 21 gauge hypodermic needles: one coupled to an OceanOptics QE65000 spectrometer, and the other to an Ocean Optics HL-2000-HP 20W light source. These needles were fixed approximately 3 mm apart, and inserted into nude mice with human head- and-neck tumor xenografts. The oxygen saturation was then measured as a function of time after irradiation at intervals of 0.5, 1, 2, 6, 12, and 24, to measure the tumors' prompt oxygen saturation response to radiation.

RESULTS

Blood volume, deoxy and oxy-hemoglobin concentrations were measured through least-squares fitting of transmission spectra. Furthermore, various configurations of interstitial fiber optic probes were explored to optimize signal strength. Improvement of the optical coupling to the biological system and a concurrent increase in source intensity are the main two focuses for boosting signal strength.

CONCLUSIONS

This work has the potential to give an understanding of the time-scales of hypoxia and reoxygenation in vivo as tumors respond to radiation injury. This technique is of particular interest for hypofractionated therapies particularly treatments of only two or three treatments, where optimizing treatment timing can increase the tumorcidal effect of the remaining fractions.