Dequalinium induces cytotoxicity in human leukemia NB4 cells by downregulation of Raf/MEK/ERK and PI3K/Akt signaling pathways and potentiation of specific inhibitors of these pathways.

Delocalized lipophilic cation dequalinium (DQA) selectively accumulates in mitochondria and displays anticancer activity in different malignancies. Our previous studies indicate a DQA-induced cytotoxicity in human acute promyelocytic leukemia NB4 cells by early disturbance in mitochondrial function and oxidative stress. This study shows the ability of DQA to downregulate Raf/MEK/ERK1/2 and PI3K/Akt signaling pathways in NB4 cells which leads to cell death by apoptosis and/or necrosis. Moreover, DQA potentiates the action of specific inhibitors of these pathways. These DQA effects could be mediated by redox regulation of Akt. Our results contribute to a better understanding of the cytotoxic DQA mechanism on leukemia cells and encourage the performance of further studies in combination with other agents such as kinase inhibitors for improving the efficacy of therapies against acute promyelocytic leukemia.

Raf/MEK/ERK signaling inhibition enhances the ability of dequalinium to induce apoptosis in the human leukemic cell line K562.

Delocalized lipophilic cations, such as dequalinium (DQA), selectively accumulate in mitochondria and display anticancer activity in cells from different malignancies. Previous studies in K562 human leukemic cells indicate that DQA causes cell damage as a consequence of an early disturbance in the mitochondrial function, inducing oxidative stress. These cells turned out to be resistant to apoptosis and died by necrosis when treated with high DQA concentrations (20 µmol/L) for long time periods (48 h). Resistance of K562 cells to DQA-induced apoptosis could be eliminated by inhibition of the kinase activity of the Bcr-Abl protein with imatinib. In this paper, we have studied the effect of DQA on the Raf/MEK/ERK1/2 and PI3K/Akt signal transduction pathways in K562 cells. Our data suggest a DQA downregulatory activity on both ERK1/2 and PI3K protein kinase activity supporting an interaction between both proteins. Moreover, inhibition of ERK1/2 with U0126 enhanced the ability of DQA to potentiate imatinib-induced apoptosis, suggesting a role of the Raf/MEK/ERK pathway and the Bcr-Abl tyrosine kinase in the K562 cell survival. This study contributes to a better understanding of the action mechanism of DQA on K562 cells and encourages the study of DQA in combination with other agents for improving the efficacy of targeted therapies and overcoming resistance to chemotherapeutic agents.

Dequalinium induces human leukemia cell death by affecting the redox balance.

Dequalinium, an amphiphilic quinolinium derivative, selectively accumulates in mitochondria and displays anticancer activity in cells from different malignancies. Previous studies indicate a differential DQA-induced cytotoxicity in NB4 and K562 human leukemia cells as a consequence of an early disturbance in mitochondrial function. Results in this paper show that DQA induces a concentration-dependent oxidative stress by decreasing GSH level and increasing ROS in a cell type specific way. Inhibitors of the JNK and p38 stress regulated kinases potentiate DQA-induced NB4 cell death suggesting a protective function for these enzymes. K562 cells with relatively high GSH levels remained resistant to DQA action.

Hepatitis C virus induces the expression of CCL17 and CCL22 chemokines that attract regulatory T cells to the site of infection.

BACKGROUND & AIMS: The mechanisms by which Foxp3+ T regulatory cells (Treg) accumulate in HCV infected livers are not known. Here, we studied the role of chemokines CCL17 and CCL22 in this process. METHODS: Chemokine mRNA levels were determined by qPCR in liver biopsies from 26 HCV chronically infected patients (CHC), 11 patients with treatment-induced sustained virological response (SVR), 16 patients with other liver diseases unrelated to HCV, and 24 normal livers. Double-immunofluorescence Foxp3/CD3 or CD11c/CCL22 was performed in liver sections. Chemokine production by monocyte-derived dendritic cells (MDDC) co-cultured with uninfected or HCV-JFH1 infected Huh7 cells was measured by qPCR and ELISA. Chemotactic activity of culture supernatants was also tested. RESULTS: Foxp3+ Treg were increased in CHC livers as compared to controls. Patients with CHC showed elevated intrahepatic levels of CCL17 mRNA compared to normal livers or livers from subjects with SVR or other forms of liver disease. Intrahepatic CCL22 expression was also higher in CHC than in healthy subjects or SVR patients but similar to that observed in other liver diseases. Dendritic cells producing CCL22 could be found inside the hepatic lobule in CHC patients. Contact between MDDC and HCV-JFH1-infected Huh7 cells induced the expression of CCL17 and CCL22 in a process partially dependent on ICAM-1. Transwell experiments showed that upregulation of these chemokines enhanced Treg migration. CONCLUSIONS: Contact of HCV-infected cells with dendritic cells induces the production of Treg-attracting chemokines, an effect which may favour liver accumulation of Treg in CHC. Our findings contribute to explain the mechanism by which HCV escapes the immune response and thus reveals novel therapeutic targets.

Dequalinium induces cell death in human leukemia cells by early mitochondrial alterations which enhance ROS production.

Dequalinium (DQA) has been proposed as a selective antitumoral agent due to its preferential accumulation in mitochondria of cancer cells. Our aim was a better understanding of DQA cytotoxicity. DQA-induced NB4 and K562 cell alterations are initiated within the first 30 min of treatment at a high DQA concentration with a mitochondrial membrane depolarization. Cytochrome c release to cytoplasm, superoxide anion overproduction and ATP depletion in NB4 cells induce, 16 h later, apoptosis by a typical caspase-9/caspase-3-dependent intrinsic pathway. K562 cells were more resistant to the DQA effect than NB4 cells, remaining viable for longer time periods.

Effects of the antitumoural dequalinium on NB4 and K562 human leukemia cell lines. Mitochondrial implication in cell death.

Dequalinium (DQA) is a delocalized lipophylic cation that selectively targets the mitochondria of carcinoma cells. However, the underlying mechanisms of DQA action are not yet well understood. We have studied the effects of DQA on two different leukemia cell lines: NB4, derived from acute promyelocytic leukemia, and K562, derived from chronic myeloid leukemia. We found that DQA displays differential cytotoxic activity in these cell lines. In NB4 cells, a low DQA concentration (2microM) induces a mixture of apoptosis and necrosis, whereas a high DQA concentration (20microM) induces mainly necrosis. However, K562 cell death was always by necrosis as the cells showed a resistance to apoptosis at all time-periods and DQA concentrations assayed. In both cell lines, the cell death seems to be mediated by alterations of mitochondrial function as evidenced by loss of mitochondrial transmembrane potential, O2*- accumulation and ATP depletion. The current study improves the knowledge on DQA as a novel anticancer agent with a potential application in human acute promyelocytic leukemia chemotherapy.