Efficient RNA interference in patients' acute lymphoblastic leukemia cells amplified as xenografts in mice

Background

Signaling studies in cell lines are hampered by non-physiological alterations obtained in vitro. Physiologic primary tumor cells from patients with leukemia require passaging through immune-compromised mice for amplification. The aim was to enable molecular work in patients' ALL cells by establishing siRNA transfection into cells amplified in mice.

Results

We established delivering siRNA into these cells without affecting cell viability. Knockdown of single or multiple genes reduced constitutive or induced protein expression accompanied by marked signaling alterations.

Conclusion

Our novel technique allows using patient-derived tumor cells instead of cell lines for signaling studies in leukemia.

Important role of caspase-8 for chemosensitivity of ALL cells

PURPOSE

Sensitivity of tumor cells toward chemotherapy mainly determines the prognosis of patients suffering from acute lymphoblastic leukemia (ALL); nevertheless, underlying mechanisms regulating chemosensitivity remain poorly understood. Here, we aimed at characterizing the role of caspase-8 for chemosensitivity of B- and T-ALL cells.

EXPERIMENTAL DESIGN

Primary tumor cells from children with ALL were evaluated for expression levels of the caspase-8 protein, were amplified in nonobese diabetic/severe combined immunodeficient mice, transfected with siRNA, and evaluated for their chemosensitivity in vitro.

RESULTS

Effective cell death in B- and T-ALL cells depended on the presence of caspase-8 for the majority of cytotoxic drugs routinely used in antileukemia treatment. Caspase-8 was activated independently from extrinsic apoptosis signaling. Accordingly in primary ALL cells, the expression level of caspase-8 protein correlated with cell death sensitivity toward defined cytotoxic drugs in vitro. In the subgroup of primary ALL cells, with low expression of caspase-8, methotrexate (MTX) upregulated the expression of caspase-8 mediated by the transcription factor p53, suggesting epigenetic silencing of caspase-8. RNA interference in patient-derived B- and T-ALL cells revealed that effective cell death induction by most routine drug combinations involving MTX depended on the presence of caspase-8.

CONCLUSION

Our results indicate that caspase-8 is crucial for the high antileukemic efficiency of numerous routine cytotoxic drugs. Reexpression of epigenetically downregulated caspase-8 represents a promising approach to increase efficiency of antileukemic therapy.

Size-dependent melting of matrix-embedded Pb-nanocrystals

We report calorimetric data for the size-dependence of the melting temperature as well as the enthalpy and entropy of melting for nanoscale Pb particles in an Al matrix, prepared by high energy ball-milling. The results are discussed with respect to various models for the melting of small confined systems. We can rule out models based on a temperature-independent Gibbs excess free energy of the particle-matrix interface, and a model based on an increased meansquare displacement of the interfacial layer. The best agreement to the data is provided by modeling the interface as an inert layer of finite thickness, which does not participate in the phase transition.

Peripartum bilateral uterine rupture in a patient with mixed connective tissue disease with favorable outcome for the severely asphyctic newborn after hypothermia

PURPOSE

Information about fetal and maternal outcome in pregnant women with mixed connective tissue disease (MCTD) is rare and in part contradictory. The purpose of this study is to review published literature about MCTD in pregnancy in the context of a rare case of peripartum bilateral uterine rupture in a patient with MCTD with favorable outcome for the severely asphyctic newborn after hypothermia.

METHOD

The study included a selective literature review based on a PubMed search using the search terms MCTD, Sharp syndrome, uterine rupture and hypothermia, and a detailed report of our case with regard to the MCTD of the patient.

RESULTS

Rupture to the backside of the uterus during delivery, independent of prior cesarean section, was unpredictable and its cause remains unclear. The clinical outcome of the newborn was surprisingly favorable and there were no signs of neurodevelopmental sequelae in spite of the fact that the newborn was asphyctic and had a large excess of acids in the umbilical cord blood gas analysis. The favorable outcome is due to treatment with whole body hypothermia.

CONCLUSIONS

Any type of prior surgery of the uterus puts the patient at risk during delivery. MCTD might be a risk factor during birth. These patients should be followed closely during pregnancy and should deliver at a center, which provides all options for immediate surgical and neonatological intervention.

Cytotoxic drug-induced, p53-mediated upregulation of caspase-8 in tumor cells

Apoptosis resistance is crucially involved in cancer development and progression, represents the leading cause for failure of anticancer therapy and is caused, for example, by downregulation of proapoptotic intracellular signaling molecules such as caspase-8. We found that the cytotoxic drugs methotrexate (MTX) and 5-fluorouracil (5-FU) were both able to sensitize resistant tumor cells for induction of apoptosis by p53-mediated upregulation of caspase-8. Increase in caspase-8 messenger RNA and protein expression disabled tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced proliferation and restored sensitivity toward TRAIL-induced apoptosis which was inhibited by transfection of p53 decoy oligonucleotides, p53 shRNA and caspase-8 shRNA. Upregulation of caspase-8 and sensitization toward TRAIL-induced apoptosis was found both in a broad panel of tumor cell lines with downregulated caspase-8 and in TRAIL-resistant primary tumor cells of children with acute leukemia. Taken together, we have identified caspase-8 as an important p53 target gene regulated by cytotoxic drugs. These findings highlight a new drug-induced modulation of physiological apoptosis pathways, which may be involved in successful anticancer therapy using MTX and 5-FU in leukemia and solid tumors over decades.

Tumor necrosis factor-related apoptosis-inducing ligand-mediated proliferation of tumor cells with receptor-proximal apoptosis defects

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) might represent a future cytotoxic drug to treat cancer as it induces apoptosis in tumor cells without toxicity in animal trials. We recently described that in contrast to apoptosis, TRAIL mediates tumor cell survival and proliferation in certain tumor cells. Here we studied the effect of TRAIL on 18 cell lines and 53 primary leukemia cells and classified these tumor cells into four groups: TRAIL, anti-DR4 or anti-DR5 induced apoptosis in group A cells, whereas they had no effect on group 0 cells and mediated proliferation in group P cells. To our surprise, TRAIL induced simultaneous apoptosis and proliferation in group AP cells. More than 20% of all cells tested belonged to group P and showed TRAIL-mediated proliferation even in the presence of certain cytotoxic drugs but not inhibitors of nuclear factor-kappaB. Transfection with B-cell leukemia/lymphoma protein 2 transformed group A cells into group 0 cells, whereas transfection with Fas-associated polypeptide with death domain (FADD)-like interleukin-1-converting enzyme-inhibitory protein (FLIP) transformed them into group AP cells. Loss of caspase-8 or transfection of dominant-negative FADD transformed group A cells into group P cells. Taken together, our data suggest that proliferation is a frequent effect of TRAIL on tumor cells, which is related to receptor-proximal apoptosis defects at the level of the death-inducing signaling complex and should be prevented during antitumor therapy with TRAIL.

Betulinic acid-induced apoptosis in leukemia cells

Betulinic acid (BA), a natural component isolated from Birch trees, effectively induces apoptosis in neuroectodermal and epithelial tumor cells and exerts little toxicity in animal trials. Here, we show that BA-induced marked apoptosis in 65% of primary pediatric acute leukemia cells and all leukemia cell lines tested. When compared for in vitro efficiency with conventionally used cytotoxic drugs, BA was more potent than nine out of 10 standard therapeutics and especially efficient in tumor relapse. No crossresistances were found between BA and any cytotoxic drug. Intracellular apoptosis signaling in leukemia tumor cells paralleled the pathway found in neuroectodermal cells involving caspases, but not death receptors. In isolated mitochondria, BA induced release of both cytochrome c and Smac. Taken together, BA potently induces apoptosis in leukemia cells and should be further evaluated as a future drug to treat leukemia.

TRAIL induced survival and proliferation in cancer cells resistant towards TRAIL-induced apoptosis mediated by NF-kappaB

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis in cancer cells. Examining primary cells of children with untreated acute leukemia, TRAIL induced apoptosis in 50% of cells, but to our surprise attenuated spontaneous apoptosis in the remaining samples or, most importantly, even mediated proliferation. We therefore examined tumor cell lines of leukemic and nonleukemic origin with apoptosis resistance towards TRAIL because of absent Caspase-8 or dysfunctional FADD. In all cell lines tested, TRAIL treatment increased cell numbers in average to 163% within 4 days and accelerated doubling time from 24 to 19 h. TRAIL-mediated proliferation was completely abrogated by blockade of NF-kappaB activation using proteasome inhibitors or in RIP-negative, IKKgamma-negative cells or in cells overexpressing dominant-negative IkappaBalpha. Our data describe the biological significance of TRAIL-mediated activation of NF-kappaB in cancer cells resistant to TRAIL-mediated apoptosis: TRAIL leads to an increase in tumor cell count by a prosurvival and possibly mitogenic function. Given the promising therapeutic potential of TRAIL as a novel anticancer drug, TRAIL-mediated survival or proliferation of target cells may restrict its use to apoptosis-sensitive tumors.

Effects of the inspiratory pressure waveform during patient-triggered ventilation on pulmonary stretch receptor and phrenic nerve activity in cats

OBJECTIVE

To examine the effects of square wave, sinusoidal, and linear inspiratory pressure waveforms during pressure-controlled assist/control ventilation on the firing pattern of pulmonary stretch receptors and phrenic nerve activity.

DESIGN

Experimental, comparative study.

SETTING

Research laboratory at a university biomedical center.

SUBJECTS

Nine anesthetized, endotracheally intubated young cats (2.5-3.4 kg).

INTERVENTION

With interposed periods of continuous positive airway pressure (0.2 kPa), each cat was exposed to periods of assist/control ventilation with three different pressure waveforms, where the peak inspiratory pressure (0.74 +/- 0.13 kPa), end-expiratory pressure (0.2 +/- 0.02 kPa), and tidal volume (14.9 +/- 5.22 mL/kg) were kept constant. Preset controlled ventilator rate was set below the rate of spontaneous breathing, and the mechanical inflation time equaled the inspiratory time during spontaneous breathing on continuous positive airway pressure.

MEASUREMENTS AND MAIN RESULTS

Respiratory rate and arterial blood gases did not change between the three pressure waveforms during assist/control ventilation. Peak pulmonary stretch receptor activity was lower and mean phrenic nerve activity higher during continuous positive airway pressure than during assist/control ventilation (p <.05). Peak inspiratory pulmonary stretch receptor activity was the same with all three pressure waveforms (82 +/- 17 impulses.sec-1) but occurred earlier with square wave than with sinusoidal or linear pressure waveforms (p <.05). The total number of impulses in the phrenic nerve activity burst was smaller with square wave than with the other two pressure waveforms (0.21 +/- 0.17 vs. 0.33 +/- 0.27 and 0.42 +/- 0.30 arbitrary units; p <.05), and the phrenic nerve activity burst duration was shorter with square wave (1.10 +/- 0.45 vs. 1.54 +/- 0.36 and 1.64 +/- 0.25 secs; p <.05).

CONCLUSION

Square wave pressure waveform during pressure-controlled assist/control ventilation strongly inhibits spontaneous inspiratory activity in cats. One mechanism for this inhibition is earlier and sustained peak pulmonary stretch receptor activity during inspiration. These findings show that differences in inspiratory pressure waveforms influence the spontaneous breathing effort during assist/control ventilation in cats.