Delayed expression of apoptosis in human lymphoma cells undergoing low-dose taxol-induced mitotic stress

Programmed cell death, redox imbalance, and cancer therapeutics

Cancer cells are disordered by nature and thus featured by higher internal redox level than healthy cells. Redox imbalance could trigger programmed cell death if exceeded a certain threshold, rendering therapeutic strategies relying on redox control a possible cancer management solution. Yet, various programmed cell death events have been consecutively discovered, complicating our understandings on their associations with redox imbalance and clinical implications especially therapeutic design. Thus, it is imperative to understand differences and similarities among programmed cell death events regarding their associations with redox imbalance for improved control over these events in malignant cells as well as appropriate design on therapeutic approaches relying on redox control. This review addresses these issues and concludes by bringing affront cold atmospheric plasma as an emerging redox controller with translational potential in clinics.

Statins enhance efficacy of venetoclax in blood cancers

Statins have shown promise as anticancer agents in experimental and epidemiologic research. However, any benefit that they provide is likely context-dependent, for example, applicable only to certain cancers or in combination with specific anticancer drugs. We report that inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) using statins enhances the proapoptotic activity of the B cell lymphoma-2 (BCL2) inhibitor venetoclax (ABT-199) in primary leukemia and lymphoma cells but not in normal human peripheral blood mononuclear cells. By blocking mevalonate production, HMGCR inhibition suppressed protein geranylgeranylation, resulting in up-regulation of proapoptotic protein p53 up-regulated modulator of apoptosis (PUMA). In support of these findings, dynamic BH3 profiling confirmed that statins primed cells for apoptosis. Furthermore, in retrospective analyses of three clinical studies of chronic lymphocytic leukemia, background statin use was associated with enhanced response to venetoclax, as demonstrated by more frequent complete responses. Together, this work provides mechanistic justification and clinical evidence to warrant prospective clinical investigation of this combination in hematologic malignancies.

The effects of a histone deacetylase inhibitor on biological behavior of diffuse large B-cell lymphoma cell lines and insights into the underlying mechanisms

Background

Epigenetic control using histone deacetylase (HDAC) inhibitors is a promising therapy for lymphomas. Insights into the anti-proliferative effects of HDAC inhibitors on diffuse large B-cell lymphoma (DLBCL) and further understanding of the underlying mechanisms, which remain unclear to date, are of great importance.

Methods

Three DLBCL cell lines (DoHH2, LY1 and LY8) were used to define the potential epigenetic targets for Trichostatin A (TSA)-mediated anti-proliferative effects via CCK-8 assay. Cell cycle distribution and apoptosis were detected by flow cytometry. We further investigated the underlying molecular mechanisms by examining expression levels of relevant proteins using western blot analysis.

Results

TSA treatment inhibited the growth of all three DLBCL cell lines and enhanced cell cycle arrest and apoptosis. Molecular analysis revealed upregulated acetylation of histone H3, α-tubulin and p53, and dephosphorylation of pAkt with altered expression of its main downstream effectors (p21, p27, cyclin D1 and Bcl-2). HDAC profiling revealed that all three cell lines had varying HDAC1–6 expression levels, with the highest expression of all six isoforms, in DoHH2 cells, which displayed the highest sensitivity to TSA.

Conclusion

Our results demonstrated that the HDAC inhibitor TSA inhibited DLBCL cell growth, and that cell lines with higher expression of HDACs tended to be more sensitive to TSA. Our data also suggested that inhibition of pAkt and activation of p53 pathway are the main molecular events involved in inhibitory effects of TSA.

Time-lapse microscopy approaches to track cell cycle and lineage progression at the single-cell level

Time-lapse microscopy can be described as the repeated collection of an image (in n-dimensions; x, y, z, λ) or field of view from a microscope at discrete time intervals. The duration of the time interval defines the temporal resolution, which in turn characterizes the type of event detected. This unit describes the implementation of time-lapse microscopy to link initial cell cycle position during acute exposures to anti-cancer agents with anti-proliferative consequences for individual cells. The approach incorporates fundamental concepts arising from the ability to capture simple video sequences of cells from which it is possible to extract kinetic descriptors that reflect the interplay of mitosis and cell death in the growth of an unsynchronized tumor population. Utilizing a multi-well format enables the user to screen different drug derivatives, multiple dose ranges, or cell cultures with unique genetic backgrounds. The objective of this unit is to present the basic methodology for capturing time-lapse sequences and touch upon subsequent mining of the data for deriving event curves and possible cell lineage maps.

Mutant p53 exhibits trivial effects on mitochondrial functions which can be reactivated by ellipticine in lymphoma cells

Increasing evidence has shown that a fraction of the wild-type (wt) form of the tumor suppressor p53, can translocate to mitochondria due to genotoxic stress. The mitochondrial targets of wt p53 have also been studied. However, whether mutant p53, which exists in 50% of human cancers, translocates to mitochondria and affects mitochondrial functions is unclear. In this study, we used doxorubicin, a chemotherapeutic drug, to treat five human lymphoma cell lines with wt, mutant or deficient in p53, to induce p53 activation and mitochondrial translocation. Our results demonstrated that mutant p53, like wt p53, was induced upon doxorubicin treatment. Similarly, a fraction of mutant p53 also translocated to mitochondria. However, Complex I and II activities in the mitochondria were compromised only in wt p53-bearing cells after doxorubicin treatment, but not in mutant p53-bearing cells. Similarly, doxorubicin treatment caused greater cell death only in wt p53-bearing cells, but not in mutant p53-bearing cells. When p53 deficient Ramos cells were transfected with mutant p53 (249S), the cells showed resistance to doxorubicin-induced cell death and decreases in complex activities. To reactivate mutant p53 and reverse chemoresistance, ellipticine (5,11-dimethyl-6H-pyrido[4,3-b]carbazole) was used to treat mutant p53 cells. Ellipticine enhanced p53 mitochondrial translocation, decreased Complex I activity, and sensitized p53 mutant cells to doxorubicin-induced apoptosis. In summary, our studies suggest that mutations in p53 may not hinder p53's mitochondrial translocation, but impair its effects on mitochondrial functions. Therefore, restoring mutant p53 by ellipticine may sensitize these cells to chemotherapy.

DRAQ5 labeling of nuclear DNA in live and fixed cells

This unit describes the use of a novel DNA-detecting far-red-fluorescing dye, DRAQ5, a modified anthraquinone, which has a unique combination of properties exploitable by cytometry. These include a high capacity to permeate the cell membrane, a high DNA binding affinity and selectivity, a fluorescence emission spectrum beyond that of fluorescein, phycoerythrin, Texas Red, Cy3, and EGFP, and excitation characteristics separate from those of propidium iodide. In this unit, methods are presented for preparation and analysis of both live and fixed cells stained with DRAQ5. While the focus is on flow cytometric assays, typical imaging applications are also indicated because the staining protocols share the same essential features.

Time-lapse microscopy approaches to track cell cycle progression at the single-cell level

Time-lapse microscopy can be described as the repeated collection of a field of view from a microscope at discrete time intervals. The duration of the time interval defines the temporal resolution, which in turn characterizes the type of event detected. This unit describes the implementation of time-lapse microscopy to link initial cell cycle position during acute exposures to anti-cancer agents with anti-proliferative consequences for individual cells. The approach incorporates fundamental concepts arising from the ability to capture simple video sequences of cells from which it is possible to extract kinetic descriptors that reflect the interplay of mitosis and cell death in the growth of an unsynchronized tumor population. Utilizing a multi-well format enables the user to test different drug derivatives, multiple dose ranges, or cell cultures with unique genetic backgrounds. The objective of this unit is to present a generic methodology for capturing time-lapse sequences and subsequently mining the data for comprehensive event analysis.

PDMP sensitizes neuroblastoma to paclitaxel by inducing aberrant cell cycle progression leading to hyperploidy

The sphingolipid ceramide has been recognized as an important mediator in the apoptotic machinery, and its efficient conversion to glucosylceramide has been associated with multidrug resistance. Therefore, inhibitors of glucosylceramide synthase are explored as tools for treatment of cancer. In this study, we used D,L-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol to sensitize Neuro-2a murine neuroblastoma cells to the microtubule-stabilizing agent paclitaxel. This treatment resulted in a synergistic inhibition of viable cell number increase, which was based on a novel mechanism: (a) After a transient mitotic arrest, cells proceeded through an aberrant cell cycle resulting in hyperploidy. Apoptosis also occurred but to a very limited extent. (b) Hyperploidy was not abrogated by blocking de novo sphingolipid biosynthesis using ISP-1, ruling out involvement of ceramide as a mediator. (c) Cyclin-dependent kinase 1 and 2 activities were synergistically decreased on treatment. In conclusion, instead of inducing apoptosis through ceramide accumulation, D,L-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol by itself affects cell cycle-related proteins in paclitaxel-arrested Neuro-2a cells resulting in aberrant cell cycle progression leading to hyperploidy.

99mTc-HYNIC-annexin V SPECT imaging of acute stroke and its response to neuroprotective therapy with anti-Fas ligand antibody

PURPOSE

The first aim of the study was to determine whether (99m)Tc-HYNIC-annexin V, a marker of cellular stress and apoptosis, can detect ischemic injury in patients with acute stroke. Secondly, we wished to test radiolabeled annexin's ability to monitor therapy in a rodent model of focal ischemic injury.

METHODS

SPECT imaging of patients was performed between 1 and 2 h after intravenous injection of 30 mCi (1,110 MBq) of tracer. Eight MFL4 (anti-FasL) antibody-treated (400 microg i.p. days 0 and 3) and 21 control adult male Sprague-Dawley rats underwent small animal SPECT imaging with 5-10 mCi (185-370 MBq) of tracer, 1 and 6 days after a 2-h intraluminal thread occlusion of the left middle cerebral artery.

RESULTS

Two patients with acute stroke had regions of multifocal annexin uptake that correlated with sites of restricted diffusion on MRI. Anti-FasL antibody treatment significantly reduced annexin uptake by 92% with a 60% decrease in the number of caspase-8 staining (apoptotic) neurons on day 1. On day 6, treated animals had an 80% reduction in tracer uptake with a 75% decrease in infarct size as compared with controls. Annexin uptake in controls and treated animals (day 6) linearly correlated with infarct size (r (2)=0.603, p=0.0036) and the number of TUNEL-positive (apoptotic) nuclei (r (2)=0.728, p=0.00084).

CONCLUSION

Annexin imaging shows foci of increased uptake at sites of ischemic injury in patients with acute stroke. Annexin imaging can assess the effects of therapy for ischemic cerebral injury in rats, suggesting its potential as a non-invasive indicator of drug efficacy in future clinical trials.

Drug-eluting stents: Sirolimus and paclitaxel differentially affect cultured cells and injured arteries

Sirolimus and paclitaxel eluted from stents inhibit cell proliferation and other cellular processes by dramatically different mechanisms. In this study, the effects of sirolimus and paclitaxel on cultured human coronary artery smooth muscle and endothelial cell function or cell cycle changes in balloon-injured arteries were directly compared. Both sirolimus and paclitaxel inhibited smooth muscle and endothelial cell proliferation. However, only paclitaxel inhibited smooth muscle and endothelial cell migration at low (nM) concentrations. Sirolimus arrested smooth muscle and endothelial cells in the G0/G1 phase of the cell cycle without inducing apoptosis while paclitaxel produced apoptosis in both cell types at low nanomolar concentrations. Although both agents blocked neointimal formation, sirolimus applied locally to injured rat carotid arteries increased the percentage of cycling vascular cells in G0/G1 without inducing apoptosis while paclitaxel increased the percentage of cycling cells in S and G2/M phases while inducing apoptosis. These results suggest that sirolimus reduces neointimal hyperplasia through a cytostatic mechanism while paclitaxel produces apoptotic cell death.

Effects of imatinib and interferon on primitive chronic myeloid leukaemia progenitors

Imatinib has impressive activity against chronic myeloid leukaemia (CML), but does not appear to completely eradicate the disease. Although responses to interferon-alpha (IFN) are slower and less dramatic than those to imatinib, they can be durable even after discontinuation of the drug. Unlike imatinib, the specific mechanisms responsible for IFN's clinical activity in CML are unknown. We found that IFN induced a G1 cell cycle arrest, as well as terminal differentiation, of the CML cell line KT-1 and CML CD34+ cells from clinical specimens. Myeloid growth factors augmented the antileukaemic activity of IFN, and neutralising antibodies directed against myeloid growth factors inhibited IFN's antileukaemic activity. We next directly compared the effects of imatinib and IFN against differentiated and primitive CML progenitors from newly-diagnosed patients. Although less active against CML granulocyte-macrophage colony forming units than imatinib, IFN was significantly more toxic to primitive CML progenitors responsible for the maintenance of long-term cultures. Imatinib and IFN appear to have divergent effects on CML progenitors at different stages of maturation, with imatinib more active against differentiated CML progenitors and IFN more active against primitive CML progenitors. The different target cells for these agents may explain the disparities in the kinetics and durability of their clinical responses. At least part of the clinical effect of IFN in CML appears to result from its ability to differentiate primitive CML progenitors.

Induction of mitotic arrest and apoptosis by evodiamine in human leukemic T-lymphocytes

Leukemias are a heterogenous group of diseases characterized by uncontrolled proliferation of abnormal blood cells of hematopoietic system. Evodiamine, a characteristic alkaloid extracted from Evodia fruits, has been reported to exhibit inhibitory effect on cell proliferation and migration in several types of cancer cells. However, there is no report elucidating the action target and anti-cancer mechanism of this potential natural compound. In this study, we have defined the anti-proliferative and apoptotic mechanisms of evodiamine in human acute leukemia CCRF-CEM cells. According to the MTT assay, the cell viability was inhibited by evodiamine in a concentration-dependent manner with an IC50 of 0.57 +/- 0.05 microM. Flow cytometry analysis showed that the apoptotic cell death proceeded by evodiamine was accompanied with a cell cycle arrest at the G2/M phase. Using Wright-Giemsa staining, we observed that evodiamine caused the cells to arrest in mitosis. It also profoundly caused an increase in polymerized tubulin levels and Bcl-2 phosphorylation on serine 70 in these cells. These data imply that the microtubular cytoskeleton appears to be one of the cellular targets in response to evodiamine. Moreover, treatment of CCRF-CEM cells with evodiamine was associated with increased levels of pro-apoptotic protein Bax, activation of caspase-3, and proteolytic cleavage of poly (ADP-ribose) polymerase, an endogenous caspase-3 substrate. Taken together, we demonstrate that evodiamine causes the mitotic arrest and a consequent apoptosis in CCRF-CEM cells through the enhancement of polymerized tubulin levels. Furthermore, several biological events including the Bcl-2 phosphorylation, Bax up-regulation and increase of caspase-3 activity could explain evodiamine-induced cell apoptosis.

The imaging of apoptosis with the radiolabeled annexin V: optimal timing for clinical feasibility

In recent years, the imaging of drug-induced apoptosis has become one of the centers of interest in experimental and clinical research. In particular, the accurate monitoring of chemosensitivity as well as the early prediction of chemoresistance in response to various pro-apoptotic interventions are critical requirements for the best management of oncology patients. The use of technetium [(99m)Tc]-labeled annexin V on animal and human models of cancers provides a proof of principle for the feasibility of a non-invasive, in vivo detection of an apoptotic signal and then for the early assessment of tumor response in the course of chemotherapy. Although promising, however, the initial clinical data point out on the technical limitations that are still to be resolved in terms of tumor-to-background ratio and optimal timing for the imaging of apoptosis. In the present review article, we report the results of animal studies aimed to the evaluation of apoptotic peaks following chemotherapy. In the light of these basic research works, we analyze the profiles of radiolabeled annexin V uptake over time as observed in clinical trials. We then discuss possible new imaging strategies designed to optimize the visualization of apoptotic changes within tumor tissues using the [(99m)Tc]-labeled annexin V. We also suggest longer lived forms of radiolabeled annexin V designed to better understand the temporal patterns of apoptotic tumor response, which in turn, may help to capture the best time-window for the imaging of cell death.

Multi-modality Imaging Identifies Key Times for Annexin V Imaging as an Early Predictor of Therapeutic Outcome

Radiolabeled annexin V may provide an early indication of the success or failure of anticancer therapy on a patient-by-patient basis as an in vivo marker of tumor cell killing. An important question that remains is when, after initiation of treatment, should annexin V imaging be performed. To address this issue, we obtained simultaneous in vivo measurements of tumor burden and uptake of radiolabeled annexin V in the syngeneic orthotopic murine BCL1 lymphoma model using in vivo bioluminescence imaging (BLI) and small animal single-photon emission computed tomography (SPECT). BCL1 cells labeled for fluorescence and bioluminescence assays (BCL1-gfp/luc) were injected into mice at a dose that leads to progressive disease within two to three weeks. Tumor response was followed by BLI and SPECT before and after treatment with a single dose of 10 mg/kg doxorubicin. Biodistribution analyses revealed a biphasic increase of annexin V uptake within the tumor-bearing tissues of mice. An early peak occurring before actual tumor cells loss was observed between 1 and 5 hr after treatment, and a second longer sustained rise from 9 to 24 hr after therapy, which heralds the onset of tumor cell loss as confirmed by BLI. Multimodality imaging revealed the temporal patterns of tumor cell loss and annexin V uptake revealing a better understanding of the timing of radiolabeled annexin V uptake for its development as a marker of therapeutic efficacy.