Involvement of ORAI1/SOCE in Human AML Cell Lines and Primary Cells According to ABCB1 Activity, LSC Compartment and Potential Resistance to Ara-C Exposure.

Acute myeloid leukemia (AML) is a hematological malignancy with a high risk of relapse. This issue is associated with the development of mechanisms leading to drug resistance that are not yet fully understood. In this context, we previously showed the clinical significance of the ATP binding cassette subfamily B-member 1 (ABCB1) in AML patients, namely its association with stemness markers and an overall worth prognosis. Calcium signaling dysregulations affect numerous cellular functions and are associated with the development of the hallmarks of cancer. However, in AML, calcium-dependent signaling pathways remain poorly investigated. With this study, we show the involvement of the ORAI1 calcium channel in store-operated calcium entry (SOCE), the main calcium entry pathway in non-excitable cells, in two representative human AML cell lines (KG1 and U937) and in primary cells isolated from patients. Moreover, our data suggest that in these models, SOCE varies according to the differentiation status, ABCB1 activity level and leukemic stem cell (LSC) proportion. Finally, we present evidence that ORAI1 expression and SOCE amplitude are modulated during the establishment of an apoptosis resistance phenotype elicited by the chemotherapeutic drug Ara-C. Our results therefore suggest ORAI1/SOCE as potential markers of AML progression and drug resistance apparition.

Pairing cells of different sizes in a microfluidic device for immunological synapse monitoring.

Analyzing cell-cell interaction is essential to investigate how immune cells function. Elegant designs have been demonstrated to study lymphocytes and their interaction partners. However, these devices have been targeting cells of similar dimensions. T lymphocytes are smaller, more deformable, and more sensitive to pressure than many cells. This work aims to fill the gap of a method for pairing cells with different dimensions. The developed method uses hydrodynamic flow focusing in the z-direction for on-site modulation of effective channel height to capture smaller cells as single cells. Due to immune cells' sensitivity to pressure, the proposed method provides a stable system without any change in flow conditions at the analysis area throughout experiments. Paired live cells have their activities analyzed with calcium imaging at the immunological synapse formed under a controlled environment. The method is demonstrated with primary human T lymphocytes, acute myeloid leukemia (AML) cell lines, and primary AML blasts.

TFT sensor array for real-time cellular characterization, stimulation, impedance measurement and optical imaging of in-vitro neural cells.

Real-time in-vitro multi-modality characterization of neuronal cell ensemble involves highly complex interdependent phenomena and processes. Although a variety of microelectrode arrays (MEAs) have been reported, diagnosis techniques are limited in term of sensing area, optical transparency, resolution and number of modalities. This paper presents an optically transparent thin-film-transistor (TFT) array biosensor chip for neuronal ensemble investigation, in which TFT electrodes are used for six modalities including extracellular voltage recording of both action potential (AP) and local field potential (LFP), current or voltage stimulation, chemical stimulation, electrical impedance measurement, and optical imaging. The sensor incorporates a large sensing area (15.6 mm × 15.6 mm) with a 200 × 150 array of indium-tin-oxide (ITO) electrodes placed at a 50 µm or 100 µm pixel pitch and with 10 ms temporal resolution; these performances are comparable to the state-of-the-art MEA devices. The TFT electrode array is designed based on the switch matrix architecture. The reliability and stability of TFTs are examined by measuring their electrical characteristics. Impedance spectroscopy function is verified by mapping the neuron position and the status (cells alive or dead, contamination) on the electrodes, which facilitates the biochemical studies in electrical domain that adds quantitative views to visual observation of cells through the optical microscopy. An in-vitro neuron culture is studied using electrophysiological, electrochemical, and optical characterization. Detailed signal analysis is demonstrated to prove the capability of bioassay.