Persistence of Chronic Lymphocytic Leukemia Stem-like Populations under Simultaneous In Vitro Treatment with Curcumin, Fludarabine, and Ibrutinib: Implications for Therapy Resistance.

Leukemic stem cells (LSCs) possess similar characteristics to normal hematopoietic stem cells, including self-renewal capacity, quiescence, ability to initiate leukemia, and drug resistance. These cells play a significant role in leukemia relapse, persisting even after apparent remission. LSCs were first described in 1994 by Lapidot et al. Although they have been extensively studied in acute leukemia, more LSC research is still needed in chronic lymphocytic leukemia (CLL) to understand if reduced apoptosis in mature cells should still be considered as the major cause of this disease. Here, we provide new evidence suggesting the existence of stem-like cell populations in CLL, which may help to understand the disease as well as to develop effective treatments. In this study, we identified a potential leukemic stem cell subpopulation using the tetraploid CLL cell line I83. This subpopulation is characterized by diploid cells that were capable of generating the I83 tetraploid population. Furthermore, we adapted a novel flow cytometry analysis protocol to detect CLL subpopulations with stem cell properties in peripheral blood samples and primary cultures from CLL patients. These cells were identified by their co-expression of CD19 and CD5, characteristic markers of CLL cells. As previously described, increased alkaline phosphatase (ALP) activity is indicative of stemness and pluripotency. Moreover, we used this method to investigate the potential synergistic effect of curcumin in combination with fludarabine and ibrutinib to deplete this subpopulation. Our results confirmed the effectiveness of this ALP-based analysis protocol in detecting and monitoring leukemic stem-like cells in CLL. This analysis also identified limitations in eradicating these populations using in vitro testing. Furthermore, our findings demonstrated that curcumin significantly enhanced the effects of fludarabine and ibrutinib on the leukemic fraction, exhibiting synergistic effects (combination drug index, CDI 0.97 and 0.37, respectively). Our results lend support to the existence of potential stem-like populations in CLL cell lines, and to the idea that curcumin could serve as an effective adjuvant in therapies aimed at eliminating these populations and improving treatment efficacy.

Accurate identification of cell doublet profiles: Comparison of light scattering with fluorescence measurement techniques.

Doublet discrimination is usually based on pulse analysis of light scatter parameters. A combination of two pulse parameters (Area, A; Height, H; or Width, W) can be used to discriminate a pulse originated in a single cell from a pulse originated from cells stuck together. Fluorescence signals can be also used to discriminate aggregates, being essential to identify cells in the G2/M phase from doublets in the G0/G1 phase in cell cycle/DNA applications. The most used method combines FSC-A versus FSC-H, whereas other strategies combine FSC-H versus FSC-W, SSC-H versus SSC-A and SSC-H versus SSC-W. However, when studying activated or proliferating cells, scatter discrimination can be difficult. In this study, we have compared the use of light scattering with fluorescence measurement techniques for successful doublet discrimination for single cells. Effective use of FSC and SSC height, area and width are commonly used to eliminate aggregates. However, fluorescence-based methods using viable DNA stains provide a good compromise between performance and accurate manual gating methods, especially for highly concentrated cell products and pathological specimens. Viable DNA dyes, such as Vybrant™ DyeCycle™ Violet stain or Hoechst 33342, can be used to detect nucleated cells in blood and in bone marrow, or to discriminate cell aggregates and debris based on no-lyse no-wash assays, where scatter degradation is a dominant component of the measured data, which increases with event rate.

Diagnostic performance of the ClearLLab 10C B cell tube.

INTRODUCTION: Pre-analytical and analytical errors can threaten the reliability of flow cytometry (FC) results. A potential solution to some of these is the use of dry, pre-mixed antibodies, such as the ClearLLab 10C system. The purpose of the present study was to compare the diagnostic performance of the ClearLLab 10C B cell tube with that of our standard laboratory practice. METHODS: We compared the diagnoses made with the ClearLLab 10C B cell tube (experimental strategy) with those made with standard laboratory practice (standard strategy). Samples were selected aiming for representation of the full spectrum of B cell disorders, with an emphasis on mature B cell malignancies, as well as healthy controls. RESULTS: We included 116 samples (34 normal controls, 4 acute lymphoblastic leukemias, 54 mature lymphoproliferative disorders in peripheral blood and bone marrow, 3 myelomas, 6 bone marrow samples with involvement by lymphoma and 1 with elevated hematogone count, 14 lymph node samples, 1 cerebrospinal fluid, and 1 pleural effusion). There were two diagnostic errors (1.7%). The agreement between the two strategies in the percentage of CD19 cells and fluorescence intensity of CD5, CD19, CD20, CD200, and CD10 was very good. CONCLUSIONS: In this study, the ClearLLab 10C B cell tube performed similarly to our standard laboratory practice to diagnose and classify mature B cell malignancies.