Andrejs Liepins

The alkaloid sanguinarine is effective against multidrug resistance in human cervical cells via bimodal cell death

Sanguinarine, a benzophenanthrine alkaloid, is potentially antineoplastic through induction of cell death pathways. The development of multidrug resistance (MDR) is a major obstacle to the success of chemotherapeutic agents. The aim of this study was to investigate whether sanguinarine is effective against uterine cervical MDR and, if so, by which mechanism. The effects of treatment with sanguinarine on human papillomavirus (HPV) type 16-immortalized endocervical cells and their MDR counterpart cells were compared. Trypan blue exclusion assays and clonogenic survival assays demonstrated that MDR human cervical cells are as sensitive as their drug-sensitive parental cells to death induced by sanguinarine. Upon treatment of both types of cells with sanguinarine, two distinct concentration-dependent modes of cell death were observed. Treatment with 2.12 or 4.24 microM sanguinarine induced death in most cells that was characterized as apoptosis using the criteria of cell surface blebbing, as determined by light and scanning electron microscopy, and proteolytic activation of caspase-3 and cleavage of the caspase-3 substrate poly(ADP-ribose) polymerase (PARP), as detected by Western blot analysis. However, 8.48 and 16.96 microM sanguinarine caused a second mode of cell death, oncosis, distinguished by cell surface blistering, and neither caspase-3 activation nor PARP cleavage. This study provides the first evidence that sanguinarine is effective against MDR in cervical cells via bimodal cell death, which displays alternative mechanisms involving different morphologies and caspase-3 activation status.

Role of Bcl-2 family proteins and caspase-3 in sanguinarine-induced bimodal cell death

Sanguinarine, a benzophenanthridine alkaloid, has anticancer potential through induction of cell death. We previously demonstrated that sanguinarine treatment at a low level induced apoptosis or programmed cell death (PCD) in the Bcl-2 low-expressing K562 human erythroleukemia cells, and that a high level induced blister cell death (BCD); whereas Bcl-2 overexpressing, sanguinarine-treated JM1 pre-B lymphoblastic cells displayed neither apoptosis nor BCD morphologies. Here, we report that sanguinarine-treated K562 cells, when analyzed by western blot, showed significant increase in expression of the pro-apoptotic Bax protein in apoptosis, but not in BCD. cDNA expression array of PCD in K562 cells failed to reveal the presence of Bax at the gene transcript level, which suggests that this cell death process does not require de novo protein synthesis. Treated JM1 cells, on the other hand, showed an increase in the expression of Bcl-2 protein in both forms of cell death, but failed to show Bax expression. The role of other members of the Bcl-2 family remained negligible. Caspase-3 activation was observed in apoptosis of K562 cells but not in BCD or in sanguinarine-treated JM1 cells. These results suggest that sanguinarine in K562 cells induces apoptosis through increasing Bax and activating caspase-3, whereas sanguinarine-induced BCD involves neither. These results also suggest that in JM1 cells, Bcl-2 may play a role in susceptibility of cells to induction of apoptosis and BCD.

Sanguinarine induces bimodal cell death in K562 but not in high Bcl-2-expressing JM1 cells

Our previous studies with low Bcl-2-expressing K562 cells have shown that, when treated with the putative anti-cancer drug sanguinarine, concentrations of 1.5 microg/ml induced the morphology of apoptosis or programmed cell death (PCD), while concentrations of 12.5 microg/ml induced a morphology of blister formation or blister cell death (BCD). To elucidate the possible role of Bcl-2 in this dual cell death modality induced by sanguinarine, K562 and the high Bcl-2-expressing JM1 cells were treated with sanguinarine concentrations of 1.5 microg/ml and 12.5 microg/ml respectively, and multiple parameters of their effects were studied using light and electron microscopy, terminal deoxynucleotidyl transferase (TdT) end-labeling, 51Cr release, trypan blue exclusion, propidium iodide exclusion, and annexin-V binding. In general, we found that, while K562 cells underwent PCD and BCD when treated with sanguinarine, JM1 cells failed to undergo either PCD or BCD under the same experimental conditions. Thus, the over-expression of anti-apoptotic Bcl-2 may have prevented sanguinarine from inducing PCD and BCD in JM1 cells. These results indicate that the resistance of JM1 cells to the alkaloid sanguinarine may have been due to an anti-BCD role played by Bcl-2, in addition to its widely reported anti-apoptotic role.

Shedding of Tumor Cell Surface Membranes

Mastocytoma P815 cells are induced to form and shed membrane vesicles (MV) from their surfaces by incubation at low temperature (4 degrees C) for 1 hr. and subsequently allowing them to warm up to room temperature (22 degrees C). Within 1-2 hrs. at room temperature, up to 90% of the P815 cells form and shed MV from their surfaces. Both cells and vesicles remain trypan blue-excluding during the MV shedding process. This process is energy dependent in that it can be inhibited by 2-deoxyglucose, sodium azide and 2-4-dinitrophenol. The shed MV can be harvested by centrifugation on a 6% Ficoll cushion and quantitated in terms of protein content. The shedding of membrane vesicles from the tumor cell surfaces results in a significant reduction in the cell size.

Aurintricarboxylic Acid Inhibits Protein Synthesis Independent, Sanguinarine-Induced Apoptosis and Oncosis

Sanguinarine, a benzophenanthridine alkaloid, has anticancer potential through induction of cell death. We previously demonstrated that sanguinarine treatment at a low concentration (1.5 μg/ml) induced apoptosis in K562 human erythroleukemia cells, and a high concentration (12.5 μg/ml) induced the morphology of blister formation or oncosis-blister cell death (BCD). Treatment of cells at an intermediate sanguinarine concentration (6.25 μg/ml) induced diffuse swelling or oncosis-diffuse cell swelling (DCS). To assess the underlying mechanism of sanguinarine-induced apoptosis and oncosis-BCD in K562 cells, we studied their response to pre-treatment with two chemical compounds: aurintricarboxylic acid (ATA) and cycloheximide (CHX). The pretreatment effects of both chemical compounds on apoptosis and oncosis-BCD were evaluated by measuring multiple parameters using quantitative morphology, electron microscopy, terminal deoxynucleotidyl transferase (TdT) end-labeling and annexin-V-binding. ATA, a DNA endonuclease inhibitor, efficiently prevented DNA nicking and inhibited apoptosis almost completely and oncosis-BCD by about 40%, while CHX, a protein synthesis inhibitor, failed to inhibit both apoptosis and oncosis-BCD. These results demonstrate, first, the importance of endonuclease in sanguinarine-induced apoptosis and to some extent in oncosis-BCD and, second, that this inhibition does not require de novo protein synthesis.

Migration patterns and functional activity of cloned cytotoxic T lymphocytes in syngeneic and allogeneic mice

The quantitative distribution of cytolytic T lymphocytes (CTL) generated in mixed leukocyte culture (MLC) and an interleukin-2 (IL-2)-dependent, CTL clone (WRL-A3) was investigated in various tissues of irradiated syngeneic and allogeneic mice. In addition, the ability of the WRL-A3 CTL clone to remain viable and retain antigen specificity following in vivo passage was evaluated. Injection i.v. of 51Cr-labeled cultured CTL resulted in: (1) extensive deposition of cells in the lungs with significantly more lymphocytes being recovered in allogeneic as compared with syngeneic lung tissue; (2) minimal accumulation in spleen with more in syngeneic than in allogeneic tissue; and (3) no localization in blood, femurs, thymus, or lymph nodes. The migration rate of cultured CTL exiting the lung during the first 4 hr was markedly faster in syngeneic than in allogeneic recipients and was directly associated with the distribution of these cells in other tissues at 24 hr. The WRL-A3 CTL clone recovered from irradiated syngeneic and allogeneic lung tissue at 1, 3, 6, 8, and 13 days after i.v. injection remained viable, even though no exogenous IL-2 was administered to the recipient mice. The recovered cells proliferated when recultured with IL-2, and retained their antigen specificity for Qed-lb target cells after in vivo passage. These findings indicate that restricted and undesirable tissue distribution, rather than impaired viability or loss of antigenic specificity, is the major obstacle to successful use of cultured CTL for adoptive immunotherapy of disseminated cancer.

Role of K+ Ion Channels in Lymphokine-Activated Killer (LAK) Cell Lytic Function

Cells of the immune system possess K+ ion channels which have been implicated in various cellular functions including activation, differentiation and cytolytic function. To define the role of K+ ion channels in the lytic function of lymphokine-activated killer (LAK) cells, we investigated the effects of K+ channel blockers on their cytolytic activity. Results show that when LAK cell mediated cytolysis of AKIL-20 tumor cells was carried out in the presence of: a) the K+ channel blocker, 4-aminopyridine (4-AP); b) the monoamine, serotonin (5-hydroxytryptamine; 5-HT); c) the serotonin agonist, quipazine; d) or the Ca++ dependent K+ channel blocker, quinidine, the cytolytic activity of the LAK cells was inhibited in a dose-dependent manner. Preincubation of LAK effector cells also inhibited lysis in a dose-dependent manner, whereas preincubation of the AKIL-20 tumor target cells produced no inhibitory effects. This study demonstrates that K+ ion channels are involved in the LAK cell cytolytic process and that compounds, including neuroendocrine products, which modulate K+ ion channel function are capable of modulating the lytic activity of these effector cells.

Morphological, Physiological and Biochemical Parameters Associated with Cell Injury: A Review

Various forms of cellular injury, whether induced by immune effector cells, aberrant metabolic processes, chemotherapeutic drugs or temperature shifts, result in common morphological changes consisting of the formation and shedding of membrane vesicles from the injured cell surfaces. This dynamic cell surface membrane behavior appears to be dependent on the disruption of cytoplasmic microtubules. Concomitant with the altered cell surface morphology certain physiological and biochemical events have been found to be associated with cell injury. These include changes in membrane permeability, elevated oxygen consumption rates and nuclear DNA fragmentation. However, it remains to be experimentally established which of these biological changes defines a state of irreparable cell injury. The objective of the present review is to compare and evaluate the cell injury process induced by effector lymphocytes with that caused by low temperature. The latter mimics most, if not all, the currently known criteria of immune effector cell mediated injury of target tumor cells.

Kinetic analysis of K+ ion channel function in lymphokine-activated killer (LAK) cells

K+ ion channels of lymphocytes have been implicated in cellular differentiation, activation and cytolytic functions. We previously demonstrated that K+ channel blockers modulate lytic activity of CTLs and LAK cells. In the present study, we define and quantitate the inhibitory effects of ion channel blockers on the lytic process using kinetic analysis of lysis. The K+ channel blocker, 4-aminopyridine, the neuroendocrine monoamine, serotonin, its agonist, quipazine, and the Ca++ dependent K+ channel blocker, quinidine were found to non-competitively inhibit the lytic process in a dose-dependent manner. These compounds inhibit lytic activity by causing a decrease in the maximum velocity (Vmax) by which LAK cells lyse tumor targets. These ion channel blockers did not alter effector or target cell viability or the binding of LAK cells to tumor cells. The inhibitory effects occurred at the effector cell level, since preincubation of LAK effector cells resulted in a dose-dependent decrease in Vmax which was related to a slower rate of target cell lytic programming (k2) by the LAK effector cells. Modulation of LAK cell lytic function occurs at a post-binding step, perhaps in the generation or release of the lytic signal.