Multipixel x ray detection integrated at the end of a narrow multicore fiber

We introduce and demonstrate the concept of a multipixel detector integrated at the tip of an individual multicore fiber. A pixel consists here of an aluminum-coated polymer microtip incorporating a scintillating powder. Upon irradiation, the luminescence released by the scintillators is efficiently transferred into the fiber cores owing to the specifically elongated metal-coated tips that ensure efficient luminescence matching to the fiber modes. With each pixel being selectively coupled to one of the cores of the multicore optical fiber, the resulting fiber-integrated x ray detection process is totally free from inter-pixel cross talk. Our approach holds promise for fiber-integrated probes and cameras for remote x and gamma ray analysis and imaging in hard-to-reach environments.

Stand-alone optical spinning tweezers with tunable rotation frequency

Advances in optical trapping design principles have led to tremendous progress in manipulating nanoparticles (NPs) with diverse functionalities in different environments using bulky systems. However, efficient control and manipulation of NPs in harsh environments require a careful design of contactless optical tweezers. Here, we propose a simple design of a fibered optical probe allowing the trapping of dielectric NP as well as a transfer of the angular momentum of light to the NP inducing its mechanical rotation. A polarization conversion from linearly-polarized incident guided to circularly transmitted beam is provoked geometrically by breaking the cylindrical symmetry of a coaxial nano-aperture that is engraved at the apex of a tapered metal coated optical fiber. Numerical simulations show that this simple geometry tip allows powerful light transmission together with efficient polarization conversion. This guarantees very stable trapping of quasi spherical NPs in a non-contact regime as well as potentially very tunable and reversible rotation frequencies in both directions (up to 45 Hz in water and 5.3 MHz in air for 10 mW injected power in the fiber). This type of fiber probe opens the way to a new generation of miniaturized tools for total manipulation (trapping, sorting, spinning) of NPs.

Optical link as an alternative for MRI receive coils: toward a passive approach

OBJECTIVE

The objective of this work was to propose an alternative solution to NMR signal transmission by replacing the coaxial cables of the receiver radiofrequency (RF) coil in the context of MRI so as to improve safety. Starting from the analysis of previous studies and reports on the topic, the difficulty of supplying power wirelessly to an RF coil was identified. To avoid this difficult task, the development of a passive analog optical link was studied.

METHODS

In order to quantify the requirements for achieving an analog conversion, the performance of the link was evaluated based on the input NMR signal amplitude and the optical power and compared with that of a galvanic link. Acquisitions were performed on a 7-T preclinical MRI system with a doped saline solution as phantom. A passive and MRI-compatible polarization-state custom-made modulator was tested as well as a commercial Mach-Zehnder interferometer.

RESULTS

The conversion was not sensitive enough to keep similar SNRs, but the main source of noise was identified along with parameters for improvement. Optical power emitted by the laser, insertion loss, and full-phase inversion voltage of the modulators were found to be crucial characteristics for the application. These data indicate that custom application devices are required since the frequency, bandwidth, and amplitude of NMR signals are quite different to usual telecommunication signals.

CONCLUSION

An electro-optic modulation and a transmission channel were successfully conceived and tested. Images were reconstructed with some significant SNR drawbacks that are expected to be compensated with an appropriate modulator.

SIGNIFICANCE

While technical challenges remain, our approach to a two-decades-long problem could solve a major issue of MRI safety by removing the need for supplying on-coil electrical current.

Abstract 2336: Eradicating melanoma cells using combination of nutritional stress and checkpoint inhibitors

Arginine (Arg) deprivation can inhibit tumors which do not express argininosuccinate synthetase (ASS), a key enzyme for synthesis of Arg. Arg deiminase (ADIPEG20) has shown antitumor activity in such tumors, including melanoma and mesothelioma. Resistance to this treatment occurs due to re-expression of ASS. We have shown that this is mediated via cMyc (positive regulator) and HIF1α ( negative regulator ). Arg starvation rapidly induces chromatin remodeling complex P300-HDAC2-Sin3A which epigenetically deacetylates H3K14ac and H3K27ac at the ASS promoter. Following the PHD2-derived HIF1α-degrading system, the promoter-bound HIF1α is degraded (Sci Rep 7:10814). This allows cMyc (an E-Box binder), to turn on ASS. Arg starvation rapidly triggers externalization of Gas6 to interact with its receptor tyrosine kinase (RTK) Axl. This activates the downstream Ras-PI3K/AKT/GSK3β pathway, resulting in stabilization of cMyc. However, this activation also turns on PDL1 gene expression. This is not surprising since cMyc has been shown to bind to PDL1 promoter and increase its expression. Thus, re-expression of ASS also leads to PDL1 expression. We studied these findings in two other cell lines, Mel114 and Skmel2, and obtained similar results, Interestingly, in three cell lines with high levels of antiapoptotic protein Bcl-2, Arg starvation only leads to growth inhibition, with only less than 2 fold increase in ASS and no PDL1 expression. These results suggest that increased Bcl-2 expression negates the necessity to increase PDL1 and ASS to prevent cell death from nutritional stress. In contrast, transfection of ASS in A2058, A375, Mel1220 and SkMel2 will only confer resistance to Arg starvation, and does not affect PDL1, Bcl2 expression or other alterations in PI3K/AKT pathway. Furthermore, in samples from patients who failed ADIPEG20 due to increased ASS expression, the primary cultures or re-biopsy tumor also exhibited high levels of PDL1 expression, which most likely will make them susceptible to anti PDL1 treatment. On the other hand, six primary cultures derived from patients who failed BRAF/MEK inhibitor (BMR) also showed low levels of ASS and increase in PDL1 expression (1.5-4 fold increase both in mRNA and proteins level compared to their parental cells). These results also applied to 5 pairs of BMR cell lines (A375/BMR, A2058/BMR, Skmel2/BMR, UACC62/BMR, MelRR/BMR). These cells also are very susceptible to combination of ADIPEG20 and PD-L1 treatment. Overall, our data suggest that combination of Arg deprivation and check point inhibitors is effective in patients whose tumors do not express ASS and as salvage therapy for BRAF/MEK inhibitor resistant patients. Supported by the VA Merit Review Award(1BX003328)

Citation Format: Lynn G. Feun, Chunjing Wu, Ying-Ying Li, Min You, Medhi Wangpaichitr, Miguel Suarez, Niramol G. Savaraj. Eradicating melanoma cells using combination of nutritional stress and checkpoint inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2336.

566 Persistent Sleep Apnea and Desaturation in Preterm Children at 18 Months of Age at High Altitude (2640 M)

Introduction

Children born at term who live at high altitude (HA) (≥ 2500 m) have different respiratory patterns from those that live at sea level. It is essential to determine these patterns in preterm children due to their high risk of Sleep Apnea-Hypopnea Syndrome (SAHS). The evolution of the apnea hypopnea index (AHI), desaturation index (ODI), and oxygen saturation (SpO2) is unknown in this group at HA. The objective was to characterize the respiratory patterns during sleep of preterm children living at HA and compare it with those of healthy children born at term.

Methods

We conducted a cross-sectional study in Bogotá, Colombia (altitude: 2640 m). We included 302 children, 127 were preterm with an average of gestational age of 31weeks (SD: 2.9) and an average weight at birth of 1600 g (SD: 594) and 175 healthy full-term infants. Three groups were defined according to age: Group I: 3–4 months, Group II: 6–7 months,, Group III: 10–18 months. All children underwent nocturnal polysomnogram to evaluate their respiratory variables: AHI, average and minimum SpO2, ODI, and T90 during sleep and analyzed the data according to the parameters of the American Academy of Sleep Medicine

Results

302 polysomnograms were performed, 54.3% were girls and were distributed by groups as follows: Group I:105 patients (34.8%), 16 preterm, Group II: 107 patients (35.4%), 46 preterm and Group III: 90 patients (29.8%), 65 preterm. We observed higher respiratory parameters within each age strata in premature infants compared to children born at term. Preterm infants had higher ODI, AHI, obstructive apnea hypopnea index (O-AHI), and Central Apnea hypopnea index (C-AHI). Although the effect decreases over time, we found a significant difference in the first age group. There was a high persistence index in children with a history of preterm birth living at high altitude. We also found a significant decrease in AHI, ODI across time in healthy and preterm children p<0.01

Conclusion

Premature children living at HA persist with higher ODI and AHI compared to children of similar ages born at term. The high desaturation index indicates the presence of intermittent hypoxia that persists in these children over time

Support (if any):

Expression of caveolin-1 in tooth germ, ameloblastoma and ameloblastic carcinoma

BACKGROUND

The caveolin-1 protein (structural component of membrane caveolae) plays important roles in several biological functions, such as endocytosis, cell adhesion, and cell signaling. However, this protein has been associated with mechanisms of tumorigenesis in several neoplasms. The expression patterns and roles of caveolin-1 in the oral epithelium and in embryonic and odontogenic tumor tissues are still unclear.

MATERIAL AND METHODS

The expression of caveolin-1 was evaluated in samples of the normal gingival epithelium (n=7), human tooth germ (TG) (n=12), ameloblastoma (AM) (n=83), and ameloblastic carcinoma (AC) (n=9) by immunohistochemistry. Additionally, AM samples were analyzed by qRT-PCR and Western blot.

RESULTS

Most TG (91.7%), AM (73.5%) and AC (100%) samples showed diverse patterns of immunohistochemical positivity for caveolin-1, while only one gingival sample was positive. The transcript levels of cav-1 were significantly upregulated by 14.9-fold in AM tissue (P = 0.0014) compared to those in normal gingival epithelial tissue, as shown by qRT-PCR. Presence of caveolin-1 protein was confirmed by Western blot analysis. The caveolin-1 immunoexpression patterns throughout the stages of TG show its importance during odontogenesis.

CONCLUSIONS

The overexpression of caveolin-1 in AM and AC compared to its expression in normal gingival epithelium (adult tissue) suggests a possible role of caveolin-1 in protumoral events, but due to the similar immunoexpression observed in AM and AC, caveolin-1 may not necessarily participate in the malignant transformation process. However, future studies are needed to clarify and confirm these hypotheses.

Louis E, Suarez M, Boeve B, Silber M, Low P, Singer W. 0787 Autonomic Dysfunction and Phenoconversion in Idiopathic/Isolated REM Sleep Behavior Disorder

Introduction

REM-sleep behavior disorder (RBD) is a common finding among patients with synucleinopathies. We aimed to determine the degree of autonomic dysfunction in patients presenting with idiopathic RBD (iRBD), and the predictive value of autonomic dysfunction for phenoconversion to a defined neurodegenerative disease.

Methods

We searched our electronic medical record for patients diagnosed with iRBD who also underwent standardized autonomic function testing within 6 months of iRBD diagnosis, and who had clinical follow-up of at least 3 years following iRBD diagnosis. Patients who received a diagnosis of phenoconversion within 3 months of autonomic testing were excluded. The composite autonomic severity score (CASS) was derived and compared between phenoconverters and non-converters using chi-square and Wilcoxon rank-sum tests.

Results

We identified 18 patients who fulfilled in- and exclusion criteria. Average age at autonomic testing was 67 ± 6.6 years. Twelve (67%) patients phenoconverted during the follow-up period; 6 developed PD, the other 6 DLB. Fifteen (83%) patients had at least mild autonomic dysfunction. There were no significant differences between overall converters and non-converters in total CASS or CASS subscores. However, iRBD patients who developed DLB had significantly higher total and cardiovagal CASS scores compared with those who developed PD (p <0.05), and a trend for higher adrenergic CASS scores compared to those who developed PD and those who did not phenoconvert (p=0.08 for each).

Conclusion

Autonomic dysfunction was seen in 83% of iRBD patients, and more severe baseline cardiovagal and adrenergic autonomic dysfunction in iRBD was associated with phenoconversion to DLB but not PD. Prospective studies are needed to confirm the value of autonomic testing for predicting phenoconversion and disease phenotype in iRBD.

Support

 

Revealing photonic symmetry-protected modes by the finite-difference-time-domain method

This Letter is devoted to pointing out a specific feature of the finite-difference-time-domain (FDTD) method through the study of nano-structures supporting geometrical symmetry-protected modes that cannot be excited at certain conditions of illumination. The spatial discretization performed in the FDTD algorithm naturally leads to breaking this symmetry and allows the excitation of these modes. The quality factors of the corresponding resonances are then directly linked to the degree of symmetry breaking, i.e., the spatial grid dimension, even though the convergence criteria of the FDTD are fulfilled. This finding shows that the FDTD must be handled with great care and, more importantly, that very huge quality-factor resonances can be achieved at the cost of nanometer-scale mastered fabrication processes.

Allergic Rhinitis and OSA in Children Residing at a High Altitude

BACKGROUND

OSA affects 2% to 4 % of the pediatric population; allergic rhinitis (AR) has been identified as a risk factor in sleep-disordered breathing, but no studies evaluating such an association have been conducted in high-altitude environments. The goal of this study was to assess whether the severity of AR is associated with the severity of OSA in children undergoing polysomnography (PSG) in the high-altitude city of Bogotá, Colombia.

METHODS

A cross-sectional observational study of children with AR was conducted. Severity of AR was evaluated by using the AR health-related quality of life questionnaire for children (ESPRINT-15) and the Allergic Rhinitis and its Impact on Asthma (ARIA) classification. Diagnosis and severity of OSA were established by using PSG. Potential associations between AR severity and OSA severity were assessed by using binary logistic regression and the Spearman correlation coefficient (ρ).

RESULTS

A total of 99 children (mean age, 7.9 years; 45% female) were included; 53% had OSA. An ESPRINT-15 score was associated with severe OSA (OR, 2.0; 95% CI, 1.12-6.04; P = .01). Patients with moderate/severe persistent rhinitis according to ARIA exhibited a 10.1-fold greater risk of severe OSA (OR, 10.15; 95% CI, 1.15-89.0). Furthermore, the apnea-hypopnea index was associated with the ESPRINT-15 score (ρ = 0.215; P = .03) and with the ARIA severity scale (P = .04; ρ = 0.203).

CONCLUSIONS

In symptomatic children with AR residing at a high altitude, increasing AR severity is associated with more severe OSA.

Nivolumab to pembrolizumab switch induced a durable melanoma response: A case report

RATIONALE

While checkpoint inhibitors have revolutionized the treatment of melanoma, it is not known whether switching from one monoclonal antibody drug to another one would be justified in the case of a treatment failure. Herein, we report a case illustrating a durable response to pembrolizumab after a failure with nivolumab.

PATIENT CONCERNS

A 76-year-old white male noticed an enlarging papular lesion on his neck.

DIAGNOSIS

Malignant melanoma.

INTERVENTIONS

The patient underwent surgery in December 2013 and was found to have a B-Rapidly Accelerated Fibrosarcoma (BRAF) V600E mutated melanoma. Treatment with BRAF and MAPK/Erk kinase (MEK) inhibitors along with radiation was initiated. After 1 year, the disease progressed, and the treatment was switched to the cytotoxic T-lymphocyte antigen 4 (CTLA-4) blocking antibody, ipilimumab. As the tumor did not respond, the treatment was changed to programmed cell death receptor-1 (PD-1) blockers: nivolumab followed by pembrolizumab. Since the initial diagnosis, the tumor response was monitored by computed tomography (CT) scans. Immunohistochemistry (IHC) was also used for the assessment of programmed death ligand 1 PD-L1) expression in the neck, lung, and spleen lesions.

OUTCOMES

The patient had an initial mixed response to nivolumab, but the disease ultimately progressed as evidenced by new metastases to the spleen, thus the treatment was switched to pembrolizumab. After 46 cycles of treatment, all sites of metastases disappeared, including a substantial shrinkage of the splenic metastasis. To gain understanding about the pharmacological differences between nivolumab and pembrolizumab, the PD-1-ligands interactions and conformational dynamics responsible for the PD-1/PD-L1 checkpoint blockade were investigated. The higher affinity of pembrolizumab might likely arise from a unique and large patch of interactions engaging the C'D loop of PD-1, thus forcing an important motion across the PD-1 immunoreceptor.

LESSONS

In this case report, we described the tolerance and response of a melanoma patient to a sequence of various agents, including ipilimumab, nivolumab, and pembrolizumab. To the best of our knowledge, this is the first clinical report highlighting differences between PD-1 blockers, as shown by the unexpected and durable response of the tumor to pembrolizumab, after a treatment failure with nivolumab.

Abstract P5-22-10: Intraoperative ultrasound guided surgery after neoadjuvant treatment in breast cancer improves patient´s quality of life

Background: Intraoperative ultrasound guided surgery (IOUS) has shown not only to improve surgical outcomes by achieving higher rates of negative margins and reducing the need for re-excisions, but also showing better cosmetic results and patient's satisfaction in the adjuvant setting. After neoadjuvant treatments (NAT) we have shown that IOUS lowers the volume of resection in patients with pathologic complete response or minimal microscopic disease after NAT without compromising margins and local recurrences when compared to wire localization techniques (WL) The aim of this study was to determine if IOUS after NAT contributes to improve cosmetic outcomes and quality of life (QOL) when compared with WL.

Material and Methods. The pilot study enrolled patients treated with NAT who underwent breast-conserving surgery (BCS) between July 2008 and December 2012. On the follow up visit, cosmetic outcomes were assessed by the patient and surgeon on a 4 point Likert scale, by the Breast Cancer Conservative Treatment cosmetic results (BCCT.core) software, and by an independent panel. QOL was assessed using cancer-specific (EORTC QLQ-C30 and EORTC QLQ-B23) questionnaires.

Results. The study investigated 113 patients: 81 (71.6 %) in the IOUS group and 32 (28.3 %) in the WL group. The patient and tumor characteristics were comparable between the two groups. Mean follow up was 64 months (range, 12-90) in the WL group while 41 months (range, 18-107) in the IOUS group.

Cosmetic outcomes reported by the patient showed a tendency (p=0.07) for better results in the IOUS group. Patient reported cosmetic outcomes and the independent panel cosmetic evaluation significantly correlated with lumpectomy volume excised (p= 0.04, p = 0.02 respectively). The BCCT.core did not correlate with volume of tissue excised (p < 0.14). IOUS achieved better cosmetic outcomes compared to WL, with excellent outcomes of 30% and 19% respectively, although poor cosmetic outcomes were 3% and 0% respectively. Correlation between patients and surgeons evaluation regarding cosmetic outcomes and satisfaction was low (0.38 and 0.40 respectively). A comparison of the QOL scores of 113 patients showed a significantly better global health status (p = 0.03), better emotional and role function (p = 0.004), for patients with IOUS compared to WL patients.

Conclusions. This is the first study to show that breast volume excised significantly correlates with cosmetic outcomes in the neoadjuvant setting. These results suggest that IOUS after NAT contributes to a better quality of life and may influence cosmetic outcomes in breast cancer patients. Patient reported outcomes should be included in the quality assessment in breast surgery as the correlation with surgeons' evaluation is low.

Citation Format: Rubio IT, Rodriguez R, Esgueva-Colmenarejo A, Suarez M, Espinosa-Bravo M, Siso C, Cordoba O, Alvarado S, Volders J, Van Den Tol P. Intraoperative ultrasound guided surgery after neoadjuvant treatment in breast cancer improves patient´s quality of life [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-22-10.

Association between intravenous acetaminophen and reduction in intraoperative opioid consumption during transsphenoidal surgery for pituitary tumors

Background and Aims

Pain during and after transsphenoidal surgeries originates from stimulation of branches of the trigeminal cranial nerve that supply the inner aspect of the nose cavity and dura mater. Thereby, patients undergoing transsphenoidal surgery may require moderate-to-large amounts of analgesics including opioids. Intravenous acetaminophen provides analgesia and reduces opioid consumption for a wide variety of surgeries. We hypothesized that the use of intravenous acetaminophen is associated with a reduction in intraoperative opioid consumption and provides significant analgesia during and after transsphenoidal surgery.

Material and Methods

This retrospective study included 413 patients who underwent transsphenoidal surgery for pituitary adenomas. The primary outcome of this study was intraoperative opioid consumption. Secondary outcomes included pain intensity, Richmond Agitation Sedation Scale scores, and nausea and vomiting upon arrival to postoperative anesthesia care unit. Patients were divided into two groups based on the intraoperative acetaminophen use. A prospensity score matching analysis was used to balance for important variables between the two groups of treatment. Regression models were fitted after matching the covariates. A P < 0.05 was considered statistically significant.

Results

After matching, 126 patients were included in each group of treatment. Patients in the acetaminophen group required significantly less amount (a decrease by 14.9%) of opioids during surgery than those in the non-acetaminophen group. Postoperative pain, postoperative nausea and vomiting, and sedation scores were not significantly different between patients who received intravenous acetaminophen and those who did not.

Conclusion

Intravenous acetaminophen is associated with a reduction in intraoperative opioids during transsphenoidal pituitary surgery.

Degradation of AMPK-α1 sensitizes BRAF inhibitor-resistant melanoma cells to arginine deprivation

Melanomas harboring BRAF mutation (V600E) are known to recur frequently following treatment with BRAF inhibitors (BRAFi) despite a high initial response rate. Our previous study has uncovered that BRAFi‐resistant melanoma (BR) cells are vulnerable to arginine deprivation. It has been reported that naïve melanoma cells undergo autophagy and re‐express argininosuccinate synthetase 1 (ASS1) to enable them to synthesize arginine for survival when encountering arginine deprivation. Abolishing these two factors in BR cells confers sensitivity to arginine deprivation. In this report, we further demonstrated that downregulation of AMPK‐α1 in BR cells is a major factor contributing to impairment of autophagy as evidenced by decreased autophagosome formation. These BR cells also showed a metabolic shift from glucose to arginine dependence, which was supported by decreased expressions of GLUT1 (glucose transporter) and hexokinase II (HKII) coupled with less glucose uptake but high levels of arginine transporter CAT‐2 expression. Furthermore, silencing CAT‐2 expression also distinctly attenuated BR cell proliferation. Notably, when naïve melanoma cells became BR cells by long‐term exposure to BRAFi, a stepwise degradation of AMPK‐α1 was initiated via ubiquitin‐proteasome system (UPS). We discovered that a novel E3 ligase, RING finger 44 (RNF44), is responsible for promoting AMPK‐α1 degradation in BR cells. RNF44 expression in BR cells was upregulated by transcription factor CREB triggered by hyperactivation of ERK/AKT. High levels of RNF44 corresponding to low levels of AMPK‐α1 appeared in BR xenografts and melanoma tumor samples from BR and BRAFi/MEK inhibitor (MEKi)‐resistant (BMR) melanoma patients. Similar to BR cells, BMR cells were also sensitive to arginine deprivation. Our study provides a novel insight into the mechanism whereby BRAFi or BRAFi/MEKi resistance drives proteasomal degradation of AMPK‐α1 and consequently regulates autophagy and metabolic reprogramming in melanoma cells.

Polarization controlled directional propagation of Bloch surface wave

Bloch surface waves (BSWs) are recently developing alternative to surface plasmon polaritons (SPPs). Due to dramatically enhanced propagation distance and strong field confinement these surface states can be successfully used in on-chip all-optical integrated devices of increased complexity. In this work we propose a highly miniaturized grating based BSW coupler which is gathering launching and directional switching functionalities in a single element. This device allows to control with polarization the propagation direction of Bloch surface waves at subwavelength scale, thus impacting a large panel of domains such as optical circuitry, function design, quantum optics, etc.

BRAF inhibitor resistance enhances vulnerability to arginine deprivation in melanoma

BRAF inhibitor (BRAFi) has been used for treatment of melanomas harboring V600E mutation. Despite a high initial response rate, resistance to BRAFi is inevitable. Here, we demonstrate that BRAFi-resistant (BR) melanomas are susceptible to arginine deprivation due to inability to initiate re-expression of argininosuccinate synthetase (ASS1, a key enzyme for arginine synthesis) as well as ineffective autophagy. Autophagy and ASS1 re-expression are known to protect melanoma cells from cell death upon arginine deprivation. When melanoma cells become BR cells by long-term in vitro incubation with BRAFi, c-Myc-mediated ASS1 re-expression and the levels of autophagy-associated proteins (AMPK-α1 and Atg5) are attenuated. Furthermore, our study uncovers that downregulation of deubiquitinase USP28 which results in more active c-Myc degradation via ubiquitin-proteasome machinery is the primary mechanism for inability to re-express ASS1 upon arginine deprivation in BR cells. Overexpression of USP28 in BR cells enhances c-Myc expression and hence increases ASS1 transcription upon arginine deprivation, and consequently leads to cell survival. On the other hand, overexpression of Atg5 or AMPK-α1 in BR cells can redirect arginine deprivation-induced apoptosis toward autophagy. The xenograft models also confirm that BR tumors possess lower expression of ASS1 and are hypersensitive to arginine deprivation. These biochemical changes in BRAFi resistance which make them vulnerable to arginine deprivation can be exploited for the future treatment of BR melanoma patients.

Tunable Bloch surface waves in anisotropic photonic crystals based on lithium niobate thin films

We present an original type of one-dimensional photonic crystal that includes one anisotropic layer made of a lithium niobate thin film. We demonstrate the versatility of such a device sustaining different Bloch surface waves (BSWs), depending on the orientation of the incident wave. By varying the orientation of the illumination of the multilayer, we measured an angle variation of 7° between the BSWs corresponding to the extraordinary and the ordinary index of the lithium niobate thin film. The potential of such a platform opens the way to novel tunable and active planar optics based on the electro- and thermo-optical properties of lithium niobate.

Simple production of membrane-based LiNbO3 micro-modulators with integrated tapers

We report on free-standing electro-optical LiNbO₃ waveguides with integrated tapers made by optical grade dicing. Membranes with a calibrated thickness are produced simultaneously with tapers acting as spot-size converters. Thereby, thicknesses from 450 to 500 μm can simply be achieved together with integrated tapers guaranteeing low insertion losses. These developments open the way to the low-cost production of compact and low-power-consuming electro-optical components. As an example, a 200 μm-long free-standing electro-optical Fabry-Perot is demonstrated with a figure of merit of only 0.19 V·cm in a 4.5 μm-thick membrane.

Abstract 2671: BRAF inhibitor resistance reprograms metabolic and survival pathways to sensitize melanoma cells to arginine deprivation

The combination of BRAF inhibitor (BRAFi) and MEK inhibitor (MEKi) has been FDA approved to treat melanomas harboring (V600E) mutation. Although most BRAF mutant melanomas are highly responsive to these treatments, they all relapse ultimately. In this study, we found a unique mechanism which can be used to treat BRAFi resistant patients. Five BRAFi resistant (BR) cells were established from known BRAF mutant cell lines A375, MEL-1220, A2058, UACC-62, and SK-MEL28 by long-term exposure to BRAFi. These BR cells are hypersensitive to ADI-PEG20, an enzyme which degrades arginine to citrulline. ADI-PEG20 treatment resulted in a 2-3-fold decrease in BR cell viability (MTT assay) and 10-30% increase in apoptosis (Annexin V/PI) in BR cells compared to their paternal cells. The mechanisms involved are as follows: All BR cells express very low levels or do not express argininosuccinate synthetase (ASS, a key enzyme to generate arginine from citrulline). Thus, these BR cells rely primarily on exogenous arginine. Furthermore, these BR cells also have attenuation of glucose uptake which makes them rely mainly on amino acids. Importantly, their ability to undergo autophagy upon nutritional stress is also impaired. The underlying mechanism for low levels of ASS is due to diminished c-Myc expression which is a positive regulator for ASS. Additionally, AMPK-α1, which possesses phosphorylation site at Thr172 governing autophagy and glucose uptake, was attenuated in BR cells. Overexpression of AMPK-α1 using plasmid transfection in A2058BR and MEL-1220BR cells rescued 8-28% ADI-PEG20-induced apoptosis and enhanced autophagosome formation (detected by LysoTacker). Conversely, knockdown of AMPK-α1 using siRNA significantly enhanced ADI-PEG20-reduced cell viability (compared to non-targeting siRNA) in A2058 and MEL-1220 cells through attenuation of autophagy and glucose uptake. This is evidenced by decreased GLUT1 and LC3-II expression, and low activity of 2-NBDG uptake, which also can be seen in most BR cells. The xenograft model also showed that ADI-PEG20 aborted tumor growth of A2058BR and A375BR cells but retarded growth of A2058 and A375 cells. Immunohistochemical staining further confirmed lower levels of ASS and AMPK-α1 in A2058BR xenograft and in tumor tissues from 10 BR patients relative to their parental counterparts (average H-scores of ASS and AMPK in parental tissues vs. BR tissues are 58.2 vs. 7.8, and 146 vs. 78.3, respectively, p &lt;0.03). Importantly, these findings also apply to cell lines and tumor samples from patients who failed both BRAF and MEK inhibitor. In summary, our data suggest that attenuated AMPK-α1 mediated autophagy and glucose uptake and decreased c-Myc mediated ASS re-expression sensitize BR cells to arginine deprivation. Thus, ADI-PEG20 is a potential salvage therapy for BR patients (Supported by R01CA152197).

Citation Format: Ying-Ying Li, Chunjing Wu, Sumedh Shah, Shu-Mei Chen, Medhi Wangpaichitr, Lynn Feun, Macus Kuo, Miguel Suarez, Niramol Savaraj. BRAF inhibitor resistance reprograms metabolic and survival pathways to sensitize melanoma cells to arginine deprivation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2671.