rottlerin and Ovarian-Neoplasms

The present study aimed to analyze the compensatory signaling pathways induced by forkhead domain inhibitor‑6 (FDI‑6), which is a forkhead box protein M1 (FOXM1) inhibitor, in ovarian cancer cells and evaluate the effectiveness of simultaneous inhibition of FOXM1 and the compensatory signaling pathway in decreasing the survival of ovarian cancer cells. The present study identified the proteins involved in the compensatory mechanism activated by FDI‑6 in HeyA8 ovarian cancer cells using western blot analysis and a reverse‑phase protein array. In addition, a cell viability assay was performed to determine the effects of FDI‑6 and the compensatory signaling pathway on cancer cell viability. All experiments were performed in three‑dimensional cell cultures. The present study observed that FDI‑6 stimulated the upregulation of N‑Ras, phosphoprotein kinase Cδ (p‑PKCδ) (S664) and HER3 in HeyA8 cells. Tipifarnib as an N‑Ras inhibitor, rottlerin as a p‑PKCδ (S664) inhibitor and sapitinib as a HER3 inhibitor were selected. The combination of FDI‑6 with tipifarnib attenuated the upregulation of N‑Ras induced by FDI‑6 and the combination of FDI‑6 with sapitinib also attenuated HER3 downstream signaling pathway in HeyA8 cells, as shown by on western blot analysis. Rottlerin downregulated p‑PKCδ (S664) by inhibiting the activity of a Src‑related tyrosine kinase that transfers a phosphate group to PKCδ. Compared with FDI‑6 alone, the addition of tipifarnib or rottlerin to FDI‑6 was significantly more effective in reducing the growth of HeyA8 cells. However, the combination of FDI‑6 and sapitinib did not induce a significant decrease in survival of HeyA8 cells. In conclusion, the addition of tipifarnib or rottlerin to inhibit N‑Ras or p‑PKCδ (S664), respectively, inhibited the compensatory signaling pathway response induced by FDI‑6 in HeyA8 cells. These inhibitors increased the efficacy of FDI‑6, which inhibits FOXM1, in reducing ovarian cancer cell viability.

Topics: Acetophenones; Benzopyrans; Cell Line, Tumor; Cell Survival; Female; Forkhead Box Protein M1; GTP Phosphohydrolases; Humans; Membrane Proteins; Ovarian Neoplasms; Pyridines; Quinazolines; Quinolones; Signal Transduction; Thiophenes

The p21-activated kinases (PAKs) are Cdc42/Rac-activated serine-threonine protein kinases that regulate several key cancer-relevant signaling pathways, such as the Mek/Erk, PI3K/Akt, and Wnt/β-catenin cascades. Pak1 is frequently overexpressed and/or hyperactivated in different human cancers, including breast, ovary, prostate, and brain cancer. PAK1 genomic amplification at 11q13 is the most common mechanism of Pak1 hyperactivation, though Pak1 mRNA and/or protein may be overexpressed in the absence of gene amplification. In previous in vitro and in vivo studies we have shown that ovarian cancer cells with amplified/overexpressed Pak1 were significantly more sensitive to pharmacologic inhibition of Pak1 compared to cells without 11q13 amplification. In the present study we examined if additional signaling pathways might be targeted in tandem with the Group I Pak inhibitor Frax-1036 in ovarian cancer cells. Using the ICCB Known Bioactives Library, we found that the cytotoxic effect of Frax-1036 was significantly higher in combination with the PKCδ inhibitor, Rottlerin, suggesting that Pak inhibitors might be combined with other agents to treat 11q13-amplified ovarian cancer.

Topics: Acetophenones; Benzopyrans; Cell Line, Tumor; Chromosomes, Human, Pair 11; Drug Synergism; Female; Humans; Ovarian Neoplasms; p21-Activated Kinases; Piperidines; Protein Kinase Inhibitors; Pyrazines; Pyrimidines; Signal Transduction

The gonadotropin hypothesis proposes that elevated serum gonadotropin levels may increase the risk of epithelial ovarian cancer (EOC). We have studied the effect of treating EOC cell lines (OV207 and OVCAR-3) with FSH or LH. Both gonadotropins activated the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase 1/2 (ERK1/2) pathway and increased cell migration that was inhibited by the MAPK 1 inhibitor PD98059. Both extra- and intracellular calcium ion signalling were implicated in gonadotropin-induced ERK1/2 activation as treatment with either the calcium chelator EGTA or an inhibitor of intracellular calcium release, dantrolene, inhibited gonadotropin-induced ERK1/2 activation. Verapamil was also inhibitory, indicating that gonadotropins activate calcium influx via L-type voltage-dependent calcium channels. The cAMP/protein kinase A (PKA) pathway was not involved in the mediation of gonadotropin action in these cells as gonadotropins did not increase intracellular cAMP formation and inhibition of PKA did not affect gonadotropin-induced phosphorylation of ERK1/2. Activation of ERK1/2 was inhibited by the protein kinase C (PKC) inhibitor GF 109203X as well as by the PKCdelta inhibitor rottlerin, and downregulation of PKCdelta was inhibited by small interfering RNA (siRNA), highlighting the importance of PKCdelta in the gonadotropin signalling cascade. Furthermore, in addition to inhibition by PD98059, gonadotropin-induced ovarian cancer cell migration was also inhibited by verapamil, GF 109203X and rottlerin. Similarly, gonadotropin-induced proliferation was inhibited by PD98059, verapamil, GF 109203X and PKCdelta siRNA. Taken together, these results demonstrate that gonadotropins induce both ovarian cancer cell migration and proliferation by activation of ERK1/2 signalling in a calcium- and PKCdelta-dependent manner.

Topics: Acetophenones; Benzopyrans; Calcium; Calcium Channels, L-Type; Cell Line, Tumor; Cell Movement; Cell Proliferation; Dantrolene; Egtazic Acid; Female; Flavonoids; Follicle Stimulating Hormone; Humans; Indoles; Luteinizing Hormone; Maleimides; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Ovarian Neoplasms; Protein Kinase C-delta; RNA, Small Interfering; Signal Transduction; Verapamil

Protein kinase C-delta (PKC delta) plays an important role in DNA damage-induced apoptosis. We have previously shown that the PKC delta inhibitor rottlerin protects against cisplatin-induced apoptosis acting upstream of caspase-9. In the present study, we have investigated if rottlerin regulates caspase-2 activation. Knockdown of caspase-2 by siRNA inhibited processing of apical caspase-9 and caspase-8, whereas depletion of caspase-9 had little effect on caspase-2 processing. Rottlerin inhibited activation and processing of caspase-9 and caspase-8 and cleavage of poly(ADP)ribose polymerase. We made a novel observation that rottlerin induced down-regulation of caspase-2 but not of caspase-3, caspase-7, caspase-8, or caspase-9. Pharmacologic inhibitors of PKC, such as Gö 6983 and bisindolylmaleimide, or depletion of PKC delta by siRNA had no effect on the down-regulation of caspase-2 by rottlerin. The proteasome inhibitor MG132 reversed caspase-2 down-regulation by rottlerin, whereas calpain inhibitor had no effect. These results suggest that rottlerin induces down-regulation of caspase-2 via PKC delta-independent but ubiquitin proteasome-mediated pathway. Furthermore, down-regulation of caspase-2 by rottlerin can explain its antiapoptotic function during DNA damage-induced apoptosis.

Topics: Acetophenones; Benzopyrans; Caspase 2; Cell Line, Tumor; Cysteine Endopeptidases; DNA Damage; Down-Regulation; Enzyme Inhibitors; Female; Gene Expression Regulation, Enzymologic; HeLa Cells; Humans; Ovarian Neoplasms; Protease Inhibitors; Proteasome Endopeptidase Complex; Protein Kinase C-delta; RNA, Small Interfering; Ubiquitin