Zosuquidar: An Effective Molecule for Intracellular Ca2+ Measurement in P-gp Positive Cells.

Intracellular calcium, as a second messenger, is involved in multilevel cellular regulatory pathways and plays a role (among other processes) in switching between survival and initiation of cell death in neoplastic cells. The development of multidrug resistance (MDR) in neoplastic cells is associated with the ability of cells to escape programmed cell death, in which dysregulation of intracellular calcium may play an important role. Therefore, reliable monitoring of intracellular calcium levels is necessary. However, such a role might be limited by a real obstacle since several fluorescent intracellular calcium indicators are substrates of membrane ABC drug transporters. For example, Fluo-3/AM is a substrate of P-glycoprotein (ABCB1 member of the ABC family), whose overexpression is the most frequent cause of MDR. The overexpression of ABCB1 prevents MDR cell variants from retaining this tracer in the intracellular space where it is supposed to detect calcium. The solution is to use a proper inhibitor of P-gp efflux activity to ensure the retention of the tracer inside the cells. The present study showed that Zosuquidar and Tariquidar (P-gp inhibitors) are suitable for monitoring intracellular calcium, either by flow cytometry or confocal microscopy, in cells overexpressing P-gp.

Targeting acute myeloid leukemia cells by CD33 receptor-specific MoS2-based nanoconjugates.

Acute myeloid leukemia (AML) is a highly aggressive type of cancer caused by the uncontrolled proliferation of undifferentiated myeloblasts, affecting the bone marrow and blood. Systemic chemotherapy is considered the primary treatment strategy; unfortunately, healthy cells are also affected to a large extent, leading to severe side effects of this treatment. Targeted drug therapies are becoming increasingly popular in modern medicine, as they bypass normal tissues and cells. Two-dimensional MoS2-based nanomaterials have attracted attention in the biomedical field as promising agents for cancer diagnosis and therapy. Cancer cells typically (over)express distinctive cytoplasmic membrane-anchored or -spanning protein-based structures (e.g., receptors, enzymes) that distinguish them from healthy, non-cancerous cells. Targeting cancer cells via tumor-specific markers using MoS2-based nanocarriers loaded with labels or drugs can significantly improve specificity and reduce side effects of such treatment. SKM-1 is an established AML cell line that has been employed in various bio-research applications. However, to date, it has not been used as the subject of studies on selective cancer targeting by inorganic nanomaterials. Here, we demonstrate an efficient targeting of AML cells using MoS2nanoflakes prepared by a facile exfoliation route and functionalized with anti-CD33 antibody that binds to CD33 receptors expressed by SKM-1 cells. Microscopic analyses by confocal laser scanning microscopy supplemented by label-free confocal Raman microscopy proved that (anti-CD33)-MoS2conjugates were present on the cell surface and within SKM-1 cells, presumably having been internalized via CD33-mediated endocytosis. Furthermore, the cellular uptake of SKM-1 specific (anti-CD33)-MoS2conjugates assessed by flow cytometry analysis was significantly higher compared with the cellular uptake of SKM-1 nonspecific (anti-GPC3)-MoS2conjugates. Our results indicate the importance of appropriate functionalization of MoS2nanomaterials by tumor-recognizing elements that significantly increase their specificity and hence suggest the utilization of MoS2-based nanomaterials in the diagnosis and therapy of AML.