Down Regulation of CLDND1 Induces Apoptosis in Breast Cancer Cells.

Identification of targets for apoptosis induction is important to provide novel therapeutic approaches in breast cancer. Our earlier studies showed that down regulation of protein kinase C δ (PKCδ) induces death in breast cancer cells. In this study we set out to identify previously unrecognized apoptosis regulators in breast cancer cells. To identify candidates, global expression analysis with microarray was performed after down regulation of PKCδ in the basal-like breast cancer cell lines MDA-MB-231, MDA-MB-468 and BT-549. Genes that were down regulated in all cell lines were further studied for survival-supporting effects. The claudin-like CLDND1 was singled out since several independent siRNAs targeting CLDND1 induced cell death in several cell lines. The cell death induced by CLDND1 knockdown was caspase-dependent, suggesting induction of apoptosis. Nuclear fragmentation, cleavage of caspase-3 and PARP and release of cytochrome C from the mitochondria upon CLDND1 depletion demonstrated involvement of the intrinsic apoptotic pathway. Inhibition of MEK1/2 and JNK further potentiated the cell death induction by CLDND1 knockdown. However, CLDND1 down regulation augmented ERK1/2 phosphorylation, which thereby may protect against the apoptosis inducing effects of CLDND1 down regulation. A concomitant inhibition of MEK1/2 suppresses the ERK1/2 phosphorylation and markedly potentiates the cell death following CLDND1 siRNA treatment. There is today little information on the function of CLDND1. These data provide novel information on CLDND1 and highlight it as a novel survival factor in basal-like breast cancer cell lines.

Expression of miR-34c induces G2/M cell cycle arrest in breast cancer cells.

BACKGROUND: MicroRNA-34 is a family of three miRNAs that have been reported to function as tumor suppressor miRNAs and show decreased expression in various cancers. Here, we examine functions of miR-34c in basal-like breast cancer cells. METHODS: Data from The Cancer Genome Atlas (TCGA) were used for evaluation of expression in primary breast cancers. Cellular processes affected by miR-34c were investigated by thymidine incorporation, Annexin V-assays and cell cycle analysis using breast cancer cell lines. Effects on potential targets were analyzed with qPCR and Western blot. RESULTS: TCGA data revealed that miR-34c was expressed at lower levels in basal-like breast cancer tumors and low expression was associated with poor prognosis. Ectopic expression of miR-34c in basal-like breast cancer cell lines resulted in suppressed proliferation and increased cell death. Additionally, miR-34c influenced the cell cycle mainly by inducing an arrest in the G2/M phase. We found that expression levels of the known cell cycle-regulating miR-34 targets CCND1, CDK4 and CDK6, were downregulated upon miR-34c expression in breast cancer cell lines. In addition, the levels of CDC23, an important mediator in mitotic progression, were suppressed following miR-34c expression, and siRNAs targeting CDC23 mimicked the effect of miR-34c on G2/M arrest. However, protein levels of PRKCA, a predicted miR-34c target and a known regulator of breast cancer cell proliferation were not influenced by miR-34c. CONCLUSIONS: Together, our results support the role of miR-34c as a tumor suppressor miRNA also in breast cancer.

Anti-leukemic effects of gallic acid on human leukemia K562 cells: downregulation of COX-2, inhibition of BCR/ABL kinase and NF-κB inactivation.

Gallic acid (GA) induces apoptosis in various cancer cell lines. In this study, we investigated the apoptotic activity induced by GA on chronic myeloid leukemia (CML) cell line-K562 and the underlying mechanism. GA reduced the viability of K562 cells in a dose and time dependent manner. GA led to G0/G1 phase arrest in K562 cells by promoting p21 and p27 and inhibiting the levels of cyclin D and cyclin E. Further studies indicated apoptosis with impaired mitochondrial function as a result of deranged Bcl-2/Bax ratio, leakage of cytochrome c and PARP cleavage along with DNA fragmentation and by up-regulating the expression of caspase-3. GA also activated the protein expressions of fatty acid synthase ligand and caspase-8. GA is more effective in imatinib resistant-K562 (IR-K562) cells (IC50 4 µM) than on K562 cells (IC50 33 µM). GA inhibited cyclooxygenase-2 (COX-2) in K562 as well as IR-K562 cells appears to be COX-2 involved in the suppression of growth. Interestingly, GA also inhibited BCR/ABL tyrosine kinase and NF-κB. In conclusion, GA induced apoptosis in K562 cells involves death receptor and mitochondrial-mediated pathways by inhibiting BCR/ABL kinase, NF-κB activity and COX-2.

Structure based drug design, synthesis and evaluation of 4-(benzyloxy)-1-phenylbut-2-yn-1-ol derivatives as 5-lipoxygenase inhibitors.

A group of 4-(benzyloxy)-1-phenylbut-2-yn-1-ol derivatives were designed using Site point connection method, synthesized and evaluated for their 5-Lipoxygenase (5-LOX) inhibitory activity. Hydrophobic site points in 5-LOX were considered for the study and substitutions were planned such that 4k will have strong hydrophobic group in the corresponding site point. Biological results supported the in silico prediction with compound 4k exhibiting good inhibition with IC(50) value of 8 µM against 5-LOX. The compounds 4j and 4k showed potent cytotoxic effects against various cancer cell lines (COLO-205, MDA-MB-231 and HepG2) but with no effect on normal cell line (HaCaT). The overall trend showed 4k as the most potent compound. Further studies demonstrated the protective effect of 4k in mouse Acute Lung Injury (ALI) model induced by lipopolysaccharide (LPS).

Chebulagic acid synergizes the cytotoxicity of doxorubicin in human hepatocellular carcinoma through COX-2 dependant modulation of MDR-1.

Non-steroidal anti-inflammatory drugs (NSAIDs) and cyclooxygenase-2 (COX-2) specific inhibitors are anti-inflammatory agents that have also shown to be useful in anticancer therapy. The effects of chebulagic acid (CA), a benzopyran tannin from Terminalia chebula having COX-2/5-LOX dual inhibitory properties, on the sensitivity of doxorubicin (Dox) in human hepatocellular carcinoma cell line HepG2 were studied in the present investigation. CA increased the accumulation of Dox in a concentration dependant manner and also enhanced the cytotoxicity of Dox in HepG2 cells by 20 folds. Quantitation of interaction by calculating Combination Index (CI) showed a strong synergistic interaction between CA and Dox in terms of cell growth inhibition. Calculation of dose reduction index (DRI) for CA-Dox combinations also showed a significant decrease in the dosage of Dox in the presence of CA. The induction of MDR1 expression by PGE(2), a metabolite of COX-2, and its downregulation by COX-2 knockdown or CA implies that the enhanced sensitivity of HepG2 cells to doxorubicin by CA is mediated by the downregulation of MDR1 expression, via COX-2-dependent mechanism. Further studies reveal the inactivation of signal transduction pathways involving Akt, ERK, JNK and p38 and the transcription factor NF-κB in the CA induced down regulation of MDR1. The present study shows the efficacy of CA to overcome MDR-1 mediated drug resistance in HepG2 cells through COX-2 dependant modulation of MDR-1.

Design, synthesis, and biological evaluation of prenylated chalcones as 5-LOX inhibitors.

Ten novel mono- and di-O-prenylated chalcone derivatives were designed on the basis of a homology derived molecular model of 5-lipoxygenase (5-LOX). The compounds were docked into 5-LOX active site and the binding characteristics were quantified using LUDI. To verify our theoretical assumption, the molecules were synthesized and tested for their 5-LOX inhibitory activities. The synthesis was carried out by Claisen-Schmidt condensation reaction of mono- and di-O-prenylated acetophenones with appropriate aldehydes. 5-LOX in vitro inhibition assay showed higher potency of di-O-prenylated chalcones than their mono-O-prenylated chalcone analogs. Compound 5e exhibited good inhibition with an IC(50) at 4 microM. The overall trend for the binding energies calculated and LUDI score was in good qualitative agreement with the experimental data. Further, the compound 5e showed potent anti-proliferative effects (GI(50) at 9 microM) on breast cancer cell line, MCF-7.

Celecoxib inhibits MDR1 expression through COX-2-dependent mechanism in human hepatocellular carcinoma (HepG2) cell line.

The role of COX-2 in the regulation of the expression of MDR1, a P-glycoprotein involved in hepatocellular carcinoma cell line, HepG2, was studied in the present investigation. Celecoxib, a selective inhibitor of COX-2, at 25 microM concentration increased the accumulation of doxorubicin in HepG2 cells and enhanced the sensitivity of the cells to doxorubicin by tenfold. The induction of MDR1 expression by PGE2 and its downregulation by celecoxib or by COX-2 knockdown suggests that the enhanced sensitivity of HepG2 cells to doxorubicin by celecoxib is mediated by the downregulation of MDR1 expression, through COX-2-dependent mechanism. Further studies revealed the involvement of AP-1 in the celecoxib-induced downregulation of MDR1 expression. These experimental studies correlated well with in silico predictions and further suggested the inactivation of the signal transduction pathways involving ERK, JNK and p38. The present study thus demonstrates the usefulness of COX-2 intervention in overcoming the drug resistance in HepG2 cells.

Inhibition of 12-LOX and COX-2 reduces the proliferation of human epidermoid carcinoma cells (A431) by modulating the ERK and PI3K-Akt signalling pathways.

Eicosanoids, the oxygenated metabolites of arachidonic acid (AA), mediate a variety of human diseases, such as cancer, inflammation and arthritis. To evaluate the role of eicosanoids in epidermoid carcinoma, the expression of AA metabolizing enzymes, such as lipoxygenases (LOXs) and cyclooxygenases (COXs), was analysed in a human epidermoid carcinoma cell line (A431). These studies revealed overexpression of 12-R-LOX and COX-2 in A431 cells. Baicalein (a 12-LOX inhibitor) and celecoxib (a COX-2 inhibitor) significantly reduced thymidine incorporation, whereas 12-(R)-HETE and 12-(S)-HETE (12-LOX metabolites) and PGE(2) (COX-2 metabolite) significantly enhanced thymidine incorporation, suggesting a role for these enzymes in the regulation of A431 cell proliferation. Further studies on the mechanism of cell death by baicalein and celecoxib revealed that the induction of apoptosis in A431 cells was associated with reduction in the Bcl-2/Bax ratio, release of cytochrome c, activation of caspase-3 and PARP cleavage. The apoptosis induced by baicalein and celecoxib was mediated by down regulation of ERK and PI3K-Akt pathways. Further, 12-(R)-HETE, 12-(S)-HETE and PGE(2) upregulated the p-ERK and p-Akt levels, suggesting the involvement of ERK and Akt pathways in the 12-LOX- and COX-2-mediated regulation of growth in A431 cells. Our findings suggest that 12-R-LOX and COX-2 play a critical role in the regulation of growth in epidermoid carcinoma and that their inhibitors may be of potential therapeutic importance.