P11.37 Evaluating water content and electrical properties at 200 kHz in brain and GBM tumor tissue of three TTFields patients with conventional imaging

BACKGROUND

Electrical properties (EPs) of brain tissue, specifically brain tumors, crucially determine the field distribution of Tumor Treating Fields (TTFields), an anti-mitotic treatment approved for glioblastoma multiforme (GBM). Due to the correlation of TTFields efficacy and field intensity at the tumor region, the knowledge of EPs in each patient is of great importance for patient-specific planning of treatment. Water content electrical properties tomography (wEPT) is a non-invasive imaging technique using water content (WC) maps obtained from rapidly acquired and processed conventional sequences to estimate the EPs of brain tissue at 128 MHz. The WC maps of this approach are constructed from two spin echo sequences similar to a T1 and a PD image. Following previous studies in rat tumor models demonstrating promising wEPT mapping of EPs in the brain at 200, this study examines the feasibility of this approach in human GBM patients.

MATERIAL AND METHODS

For three patients of the EF-14 trial population, we divided T1 and PD images pixel-by-pixel to obtain the image ratio. Using a transfer function, WC maps were generated and maps of the electrical conductivity σ and the relative permittivity ε r at 200 kHz were calculated with two different equations.

RESULTS

The median value of estimated WC remains similar in healthy brain tissues among all patients, ~73.5% in the white matter, ~82% in the gray matter. The median values of wEPT-estimated σ at 200 kHz in the white matter is ~0.09 S/m and in the gray matter ~0.18 S/m, corresponding median values of ε r at 200 kHz are ~2100 and ~3000 in white and gray matter respectively. Contrary, in the tumor the spread between the median values of WC and EPs is much higher. Stating the most important findings, in the necrosis median WC are 90.3%, 92.3%, 85.2% in patients 1–3 respectively with corresponding median σ values of 0.494, 0.657, 0.25 S/m. In the enhancing tumor the spread of median WC is even higher (67.2%, 83.6%, 85.5%), yet lower spread but also very heterogeneous median σ values of 0.075 S/m, 0.208, 0.259 S/m are estimated with wEPT.

CONCLUSION

Our results demonstrate the adaption of wEPT for mapping of WC and EPs at 200 kHz in three human GBM patients. In contrast to the vastly irregular tumor tissue, our estimations in healthy brain tissue are similar between patients and in accordance with EPs experimentally measured during our animal experiments and consistent with reported values in the literature. Hence, wEPT is a promising, fast technique based on regular MRI that might help patient-specific treatment planning of TTFields therapy, although the mapping of tumor tissue needs further confirmation in a greater population and investigations of EPs of excised tumor tissue samples should be conducted.

P11.25 Assessing electrical properties of cells as predictive marker for patient-specific TTFields response and optimal frequency

BACKGROUND

Tumor treating fields (TTFields) are currently approved for the treatment of glioblastoma multiforme (GBM, using 200 kHz), and being tested in other tumor types such as non-small cell lung cancer and brain metastases occurring in this indication (LUNAR and METIS trials, using 150 kHz). Response to TTFields in cancer cells was empirically shown to be frequency-dependent specific for cell type; however, there are no markers available predicting optimal frequency or response in different cancer types or individual patients to date. There is evidence indicating electrical properties determine the optimal anti-mitotic frequency. This study analyzed the correlation of electrical properties of cells with their optimal TTFields frequency and sensitivity using the 3DEP reader (LabTech) to determine the electrical properties with the help of Dielectrophoresis (DEP) force. With this technique, cell movements within electric fields of different frequencies can by analyzed based on the physical effect of DEP, exercising a force on polarizable particles inside a non-homogeneous electric field.

MATERIAL AND METHODS

We used the 3DEP reader to obtain baseline properties (permittivity and conductivity) of 17 different cell lines of several tumor types. The resulting curves were analyzed by a 2-way ANOVA. Additionally, we determined the optimal frequency for maximum cytotoxic effect for each cell line using the inovitroTM system and eventually compared with the detected electrical properties.

RESULTS

We found cell lines with an optimal TTFields frequency of 150 kHz (corresponding to cells with a membrane capacitance in the lower range of the observed 3DEP curves, n=9) to possess significantly different (p<0.001) electrical properties from cells with an optimal TTFields frequency of 200 kHz (n=8). According to the curve differences in the lower frequency range, the measure of membrane capacitance served as a good predictor for TTFields response.

CONCLUSION

This study showed a correlation of cell membrane capacitance and optimal TTFields frequency and response. Our results provide a substantial rationale for further studies investigating the predictive potential of electrical properties of tumor cells as a measure for the optimal frequency and sensitivity to TTFields in individual patients.

Electron holography on HfO2/HfO2-x bilayer structures with multilevel resistive switching properties

Unveiling the physical nature of the oxygen-deficient conductive filaments (CFs) that are responsible for the resistive switching of the HfO₂-based resistive random access memory (RRAM) devices represents a challenging task due to the oxygen vacancy related defect nature and nanometer size of the CFs. As a first important step to this goal, we demonstrate in this work direct visualization and a study of physico-chemical properties of oxygen-deficient amorphous HfO_2-x by carrying out transmission electron microscopy electron holography as well as energy dispersive x-ray spectroscopy on HfO₂/HfO_2-x bilayer heterostructures, which are realized by reactive molecular beam epitaxy. Furthermore, compared to single layer devices, Pt/HfO₂/HfO_2-x /TiN bilayer devices show enhanced resistive switching characteristics with multilevel behavior, indicating their potential as electronic synapses in future neuromorphic computing applications.

Modelling Tumor Treating Fields for the treatment of lung-based tumors

Tumor Treating Fields (TTFields), low-intensity electric fields in the frequency range of 100-500 kHz, exhibit antimitotic activity in cancer cells. TTFields were approved by the U. S. Food and Drug Administration for the treatment of recurrent glioblastoma in 2011. Preclinical evidence and pilot studies suggest that TTFields could be effective for treating certain types of lung cancer, and that treatment efficacy depends on the electric field intensity. To optimize TTFields delivery to the lungs, it is important to understand how TTFields distribute within the chest. Here we present simulations showing how TTFields are distributed in the thorax and torso, and demonstrate how the electric field distribution within the body can be controlled by personalizing the layout of the arrays used to deliver the field.

Technology modules from micro- and nano-electronics for the life sciences

The capabilities of modern semiconductor manufacturing offer remarkable possibilities to be applied in life science research as well as for its commercialization. In this review, the technology modules available in micro- and nano-electronics are exemplarily presented for the case of 250 and 130 nm technology nodes. Preparation procedures and the different transistor types as available in complementary metal-oxide-silicon devices (CMOS) and BipolarCMOS (BiCMOS) technologies are introduced as key elements of comprehensive chip architectures. Techniques for circuit design and the elements of completely integrated bioelectronics systems are outlined. The possibility for life scientists to make use of these technology modules for their research and development projects via so-called multi-project wafer services is emphasized. Various examples from diverse fields such as (1) immobilization of biomolecules and cells on semiconductor surfaces, (2) biosensors operating by different principles such as affinity viscosimetry, impedance spectroscopy, and dielectrophoresis, (3) complete systems for human body implants and monitors for bioreactors, and (4) the combination of microelectronics with microfluidics either by chip-in-polymer integration as well as Si-based microfluidics are demonstrated from joint developments with partners from biotechnology and medicine. WIREs Nanomed Nanobiotechnol 2016, 8:355-377. doi: 10.1002/wnan.1367 For further resources related to this article, please visit the WIREs website.

Which elements of the mammalian central nervous system are excited by low current stimulation with microelectrodes?

Low current cortex stimulation produces a sparse and distributed set of activated cells often with distances of several hundred micrometers between cell bodies and the microelectrode. A modeling study based on recently measured densities of high threshold sodium channels Nav1.2 in dendrites and soma and low threshold sodium channels Nav1.6 in the axon shall identify spike initiation sites including a discussion on dendritic spikes. Varying excitability along the neural axis has been observed while studying different electrode positions and configurations. Although the axon initial segment (AIS) and nodes of Ranvier are most excitable, many thin axons and dendrites which are likely to be close to the electrode in the densely packed cortical regions are also proper candidates for spike initiation sites. Cathodic threshold ratio for thin axons and dendrites is about 1:3, whereas 0.2 mum diameter axons passing the electrode tip in 10 mum distance can be activated by 100 mus pulses with 2.6 muA. Direct cathodic excitation of dendrites requires a minimum electrode-fiber distance, which increases with dendrite diameter. Therefore thin dendrites can profit from the stronger electrical field close to the electrode but low current stimulation cannot activate large diameter dendrites, contrary to the inverse recruitment order known from peripheral nerve stimulation. When local depolarization fails to generate a dendritic spike, stimulation is possible via intracellular current flow that initiates an action potential, for example 200 mum distant in the low threshold AIS or in certain cases at the distal dendrite ending. Beside these exceptions, spike initiation site for cathodic low current stimulation appears rather close to the electrode.

Risk factors for invasive aspergillosis in neutropenic patients with hematologic malignancies

Risk factors for invasive aspergillosis (IA) are incompletely identified and may undergo changes due to differences in medical practice. A cohort of 189 consecutive, adult patients with neutropenia hospitalized in the hemato-oncology ward of the University hospital Berne between 1995 and 1999 were included in a retrospective study to assess risk factors for IA. In total, 45 IA cases (nine proven, three probable, 33 possible), 11 patients with refractory fever and 133 controls were analyzed. IA cases had more often acute leukemia or myelodysplastic syndrome (MDS) (88 vs 38%, P < 0.001) and a longer duration of neutropenia (mean 20.6 vs 9.9 days, P < 0.001). They also had fewer neutropenic episodes during the preceding 6 months (mean 0.42 vs 1.03, P < 0.001), that is, confirmed (82%) and probable (73%) IA occurred most often during the induction cycle. A short time interval ( < or = 14 days) between neutropenic episodes increased the risk of IA four-fold (P = 0.06). Bacteremia, however, was not related to the number of preceding neutropenic episodes. Therefore, neutropenic patients with leukemia or MDS have the highest risk of IA. The risk is highest during the first induction cycle of treatment and increases with short-time intervals between treatment cycles.

Rituximab plus gemcitabine: a therapeutic option for elderly or frail patients with aggressive non Hodgkin's lymphoma?

The standard treatment for patients with aggressive B-cell lymphoma--particularly diffuse large-B-cell lymphoma [DLBCL)--is cyclophosphamide, doxorubicin, vincristine and prednisone [CHOP) plus rituximab, a chimeric monoclonal antibody against the CD20 antigen. However, some patients are not fit enough to tolerate CHOP or they relapse after previous therapy with CHOP. Gemcitabine as a monotherapy is active and relatively non-toxic in the treatment of NHL. We investigated the toxicity and efficacy of a combination of gemcitabine with rituximab in a small series of elderly patients with high-grade B-cell lymphoma who had either a relapse after CHOP, or were medically unfit to tolerate CHOP as a first-line therapy. Gemcitabine was given at 1000 mg/m2/week x 3, q28 days; rituximab at 325 mg/m2/week x 4 in the first cycle, and on day 1 of all subsequent cycles. Seven patients have been treated. The median number of cycles given was 4. The major toxicity was haematologic: grade 3/4 leukocytopenia occurred in 4 patients, grade 3/4 thrombocytopenia in 3 patients. There were no episodes of clinically significant bleeding. One patient developed febrile neutropenia and died in the course of treatment; another patient developed non-Q-wave myocardial infarction possibly related to hydration pre-treatment to rituximab and erythrocyte transfusion. He recovered well after symptomatic therapy. In 7 patients, 2 complete and 3 partial remissions were achieved, with an estimated median time to progression of 12 months. This series of patients shows that the combination of gemcitabine and rituximab is feasible in this population not able to undergo standard poly-chemotherapy, shows promising activity, and merits further evaluation.

Use of DNA arrays/microarrays in pancreatic research

In recent years, enormous technical advances in experimental protocols as well as robotic and bioinformatic techniques have allowed DNA array/microarray technology to emerge as the leading technology in the field of functional, disease-related genome analysis. Multiple applications exist for DNA arrays/microarrays including comparative genomic analysis to identify chromosomal imbalances (Matrix-CGH), the study of mutations and genetic polymorphisms, and the study of gene expression (expression profiling). Expression profiling is the most widely used application of DNA array/microarray technology and allows to measure gene expression of thousands of genes simultaneously. The present review describes the basic principles of expression profiling analyses and outlines some applications in pancreatic cancer research.

GRP-receptor-mediated signal transduction, gene expression and DNA synthesis in the human pancreatic adenocarcinoma cell line HPAF

Bombesin-like peptides have been implicated as growth factors in various human cancers. Human adenocarcinoma cell lines (Capan-1, Capan-2, MiaPaCa-2 and HPAF) were tested to determine whether they express the gastrin-releasing peptide-preferring bombesin receptor (GRPR) and neuromedin B-preferring bombesin receptor (NMBR). Using RT-PCR the highest level of GRP receptor mRNA was found in HPAF cells. NMB receptor mRNA expression moderate in all cell lines investigated. We therefore selected the HPAF cell line to investigate whether bombesin treatment affects intracellular Ca(2+) ([Ca(2+)](i)), cAMP level, DNA synthesis as a measure of cell proliferation, and expression of three transcription factors: c-fos, c-myc and high mobility group protein IY (HMG-I(Y)).Bombesin administration led to an immediate increase in free intracellular Ca(2+) concentration ([Ca(2+)](i)) but did not change cAMP levels. The peptide also enhanced [(3)H]thymidine incorporation in HPAF cells (but not in the other cell lines), an effect that was concentration dependent, reaching 36 +/- 5% stimulation over control values at 24 h with an EC(50) of 2.27 x 10(-12) M. Furthermore, bombesin stimulated c-fos, c-myc and HMG-I(Y) expression in a time-dependent manner: the c-fos mRNA level increased dramatically in the first 30 min of exposure, then returned to basal level within 2 h, while the c-myc and HMG-I(Y) mRNA levels peaked at 2 h and 4h, respectively. All actions of bombesin were blocked by BME (D-Phe(6)-bombesin-(6-13)-methylester), a selective GRP receptor antagonist, but not by the NMB receptor antagonist BIM-23127 (D-Nal-cyclo[Cys-Tyr-D-Trp-Orn-Val-Cys]-Nal-NH(2)). We conclude that HPAF cells express mRNA for GRP receptors and that functional receptors are present in the cell membrane. The occupation of these receptors leads to a sequence of intracellular events involving rapid mobilization of intracellular Ca(2+), expression of c-fos, c-myc and HMG-I(Y) mRNA, and stimulation of cell proliferation. Conversely, although NMB receptor mRNA can be detected, its actual translation to functional receptors does not reach a detectable level.

[Multiple morbidity in a patient (87 years old)]

The group of aged people--in particular of highly aged persons--increases and with it also the risk of polymorbidity. Atherosclerosis often occurs in the elderly population; it is not astonishing that atherosclerosis also increasingly affects the renal arteries. Another problem in this age group is chronic back- and leg pain. Considering a medicine that respects the patient's attitude and is reasonable and cost-effective, the care and therapy of a polymorbid patient offers a special challenge in the modern evidence-based medicine.

Novel technology for detection of genomic and transcriptional alterations in pancreatic cancer

AIM

The present review summarizes our strategies aimed at identifying and characterizing genetic alterations occurring at the transcriptional and chromosomal level in pancreatic cancer.

METHODS

To study transcriptional alterations we have used a number of techniques including modified versions of differential hybridizations and cDNA-RDA (representational difference analysis). Comparative genomic hybridization (CGH) was used to study chromosomal aberrations occurring in pancreatic cancer tissues.

RESULTS

The study of transcriptional alterations led to the identification of more than 500 genes with differential expression in pancreatic cancer. The sum of these alterations represented the first expression profile characteristic for pancreatic tumors. The CGH analysis allowed the identification of a number of chromosomal regions containing putative tumor suppressor genes or oncogenes. These regions are presently being characterized at the molecular level. In a first approach the myb-oncogene was identified as the relevant oncogene of an amplification on 6q occurring in up to 10% of pancreatic cancer patients.

CONCLUSIONS

Genes isolated in both approaches represent potential new disease genes for pancreatic cancer and are at present being characterized by individual or serial analysis.

Strategies for the detection of disease genes in pancreatic cancer

The present review summarizes our strategies aimed at identifying and characterizing genetic alterations occurring at the transcriptional and chromosomal level in pancreatic cancer. To study transcriptional alterations we have used a number of techniques including modified versions of differential hybridizations and cDNA RDA (representational difference analysis). These approaches have led to the identification of more than 500 genes with differential expression in pancreatic cancer. To study chromosomal aberrations occurring in pancreatic cancer tissues we used comparative genomic hybridization (CGH). This allowed the identification of a number of chromosomal regions containing putative tumor suppressor genes or oncogenes. Genes isolated in both approaches represent potential new disease genes for pancreatic cancer and are at present being characterized by individual or serial analysis.

Expression and differential regulation of connective tissue growth factor in pancreatic cancer cells

CTGF is an immediate early growth responsive gene that has been shown to be a downstream mediator of TGFbeta actions in fibroblasts and vascular endothelial cells. In the present study hCTGF was isolated as immediate early target gene of EGF/TGFalpha in human pancreatic cancer cells by suppression hybridization. CTGF transcripts were found in 13/15 pancreatic cancer cell lines incubated with 10% serum. In 3/7 pancreatic cancer cell lines EGF/TGFalpha induced a significant rise of CTGF transcript levels peaking 1-2 h after the start of treatment. TGFbeta increased CTGF transcript levels in 2/7 pancreatic cancer cell lines after 4 h of treatment and this elevation was sustained after 24 h. Only treatment with TGFbeta was accompanied by a parallel induction of collagen type I transcription. 15/19 human pancreatic cancer tissues were shown to overexpress high levels of CTGF transcripts. CTGF transcript levels in pancreatic cancer tissues and nude mouse xenograft tumors showed a good correlation to the degree of fibrosis. In situ hybridization and the nude mouse experiments revealed that in pancreatic cancer tissues, fibroblasts are the predominant site of CTGF transcription, whereas the tumor cells appear to contribute to a lesser extent. We conclude that CTGF may be of paramount importance for the development of the characteristic desmoplastic reaction in pancreatic cancer tissues.

Retinal pigment epithelial cells secrete substances that are chemotactic for monocytes

Monocyte/macrophages play a prominent role in several forms of retinal pathology including proliferative vitreoretinopathy, senile macular degeneration, and retinal wound healing. In each of these entities, the retinal pigment epithelium (RPE) is characteristically involved as well. Since RPE cells are known to secrete chemoattractants for astrocytes, we considered the possibility that they might secrete chemotactic factors for monocytes in addition. We have found in in vitro assays that a 5% concentration of medium from 6 different well-established RPE culture lines each consistently induced monocyte migration greater than that elicited by either buffer or unconditioned medium. "Checkerboard" analysis indicated that RPE culture supernatants induced optimal migration with a stimulus gradient (chemotaxis as opposed to chemokinesis alone). Chemotactic activity could be detected in eluates from ion exchange high performance liquid chromatography or gel filtration columns. Several peaks of activity suggested that more than one factor may be responsible for the ability to induce cell migration. The chemotactic activity was largely heat stable. The chemotactic factor induced only minimal migration of polymorphonuclear leukocytes. The secretion of chemotactic factors for monocytes could contribute significantly to the pathogenesis of several retinal diseases.