jasplakinolide and Leukemia

Sonodynamic therapy (SDT) is a form of ultrasound therapy that has been shown to preferentially damage malignant cells based on the relatively enlarged size and altered cytology of neoplastic cells in comparison to normal cells. This study sought to determine whether cytoskeletal-directed agents that either disrupt (cytochalasin B and vincristine) or rigidify (jasplakinolide and paclitaxel) microfilaments and microtubules, respectively, affect ultrasonic sensitivity. U937 human monocytic leukemia cell populations were treated with each cytoskeletal-directed agent alone, and then sonicated at 23.5 kHz under relatively low power and intensity (20-40 W; 10-20 W/cm(2)), or at 20 kHz using moderate power and intensity (60 W; 80 W/cm(2)). In addition, human leukemia lines U937, THP1, K562, and Molt-4, and the murine leukemia line L1210 were sonicated using pulsed 20 kHz ultrasound (80.6 W; 107.5 W/cm(2)) both with and without the addition of cytoskeletal-directed agents to assess whether cytoskeletal-directed agents can potentiate ultrasonic sensitivity in different leukemia lines. Human hematopoietic stem cells (hHSCs) and leukocytes were sonicated with continuous 23.5 kHz ultrasound (20 W; 10 W/cm(2)) to determine whether this approach elicited the preferential damage of neoplastic cells over normal blood components. To determine whether ultrasonic sensitivity is exclusively dependent on cell size, leukemia cells were also enlarged via alteration of cell growth parameters including serum deprivation and re-addition, and plateau-phase subculturing. Results indicated that cytochalasin B/ultrasound treatments had the highest rates of initial U937 cell damage. The cells enlarged and partially synchronized, either by serum deprivation and re-addition or by plateau-phase subculturing and synchronous release, were not comparably sensitive to ultrasonic destruction based solely on their cell size. In addition, cytochalasin B significantly potentiated the ultrasonic sensitivity of all neoplastic cell lines, but not in normal blood cells, suggesting that preferential damage is attainable with this treatment protocol. Therefore, it is likely that ultrasonic cell lysis depends not only on cell size and type, but also on the specific molecular mechanisms used to induce cell enlargement and their effects on cell integrity. This is supported by the fact that either the microfilament-or microtubule-disrupting agent produced a higher rate of lysis for cells of a given size th

Topics: Animals; Antineoplastic Agents; Cell Cycle; Cell Death; Cell Growth Processes; Culture Media, Serum-Free; Cytochalasin B; Cytoskeleton; Depsipeptides; Humans; Leukemia; Leukemia L1210; Mice; Microtubules; Paclitaxel; U937 Cells; Ultrasonic Therapy; Ultrasonography; Vincristine

One important mechanism cytotoxic T lymphocytes (CTLs) use to kill virus-infected, transplanted or tumour targets is exocytosis of granules that contain cytotoxic agents such as perforin and granzymes. Granule exocytosis-dependent target cell killing is a complex process, involving initial T-cell receptor (TCR)-dependent signalling that includes Ca2+ influx and activation of protein kinase C, shape changes that serve to bind the CTL to the target and, finally, exocytosis of lytic granules at the site of contact with the target cell. Although there is reason to propose that multiple steps in the lytic process could involve the actin cytoskeleton of CTLs, few studies have examined this issue, and those that have do not allow the specific step(s) involved to be determined. We have used the potent membrane-permeant actin cytoskeleton-modifying drugs jasplakinolide and latrunculin A to investigate the actin dependence of defined processes that are expected to be important for granule exocytosis-dependent killing. Our results, obtained using TALL-104 human leukaemic CTLs as a model system, are consistent with the idea that a functional actin cytoskeleton is required for TCR/CD3-dependent signalling, for activation of store-dependent Ca2+ influx and for CTL shape changes. When cells were stimulated with solid-phase anti-CD3 antibodies, treatment with either jasplakinolide or latrunculin A abolished granule exocytosis. However, when cells were stimulated in a manner that bypasses TCR/CD3-dependent signalling, granule exocytosis was not significantly altered, suggesting that the actin cytoskeleton does not function as a barrier to exocytosis.

Topics: Actin Cytoskeleton; Antibodies, Monoclonal; Antineoplastic Agents; Bridged Bicyclo Compounds, Heterocyclic; Calcium; CD3 Complex; Cell Membrane; Cell Movement; Depsipeptides; Exocytosis; Humans; Leukemia; Lymphoma, B-Cell; Membrane Glycoproteins; Peptides, Cyclic; Perforin; Pore Forming Cytotoxic Proteins; Signal Transduction; T-Lymphocytes, Cytotoxic; Thiazoles; Thiazolidines; Tumor Cells, Cultured