erucylphosphocholine and Glioblastoma

The membrane-targeted apoptosis modulators erucylphosphocholine (ErPC) and erucylphosphohomocholine (ErPC3) induce apoptosis in highly apoptosis resistant malignant glioma cell lines and enhance radiation-induced cell death and eradication of clonogenic tumor cells in vitro. Aim of the present study was to elucidate molecular mechanisms of combined action.. Induction of apoptosis was evaluated by determination of nuclear morphology (fluorescence microscopy), alteration of mitochondrial function and caspase-activation (flow cytometry, Western blot). Activity of protein kinase B (PKB/Akt) and key downstream effectors involved in apoptosis regulation was verified by Western blot analysis using activation-specific antibodies.. Increased cytotoxicity of the combination was linked to a more efficient activation of the intrinsic apoptosis pathway with increased damage of the mitochondria and caspase-activation. Moreover, activity of the survival kinase PKB/Akt was downregulated upon treatment with ErPC/ErPC3 alone or in combination with ionizing radiation. Inhibition of PKB/Akt was associated with decreased phosphorylation and thus activation of the pro-apoptotic Bcl-2 protein Bad as well as dephosphorylation of the transcription factor FOXO3A (FKHRL1) that may be responsible for the observed increased expression of the pro-apoptotic Bcl-2 protein Bim.. Our data suggest a role for inhibition of PKB/Akt-mediated anti-apoptotic signaling in increased efficacy of the combination.

Topics: Apoptosis; Astrocytoma; Caspases; Cell Line, Tumor; Combined Modality Therapy; Down-Regulation; Enzyme Activation; Erucic Acids; Glioblastoma; Humans; Mitochondria; Phosphorylcholine; Proto-Oncogene Proteins c-akt; Signal Transduction

Erucylphosphocholine (ErPC) exerts strong anticancer activity in vivo and in vitroand induces apoptosis even in chemoresistant glioma cell lines. We investigated the contribution of Apaf-1 and caspase-3 to the apoptotic response to ErPC using RNA interference (RNAi) in human glioblastoma cells. We could demonstrate that human glioma cell lines are susceptible to RNAi. Apaf-1 and caspase-3 are amenable to specific small interfering RNA (siRNA)-induced degradation resulting in a reduction of protein levels to 8-33% (Apaf-1) and to 30-50% (caspase-3). Transfection of siRNA directed to Apaf-1 and caspase-3 specifically reduced caspase-3 processing induced by ErPC treatment and yielded a reduction in cells that undergo ErPC-induced apoptosis to 17-33% (Apaf-1) and to 38-50% (caspase-3). The caspase-3 siRNA experiments were corroborated in caspase-3-deficient and -reconstituted MCF-7 breast cancer cells. Survival assays and morphological observations revealed that caspase-3 reconstitution significantly sensitized MCF-7 cells to ErPC. Exploring the caspase cascade responsible for ErPC-induced apoptosis MCF-7 cells provided evidence that caspase-3 is required for the activation of caspases-2, -6 and -8 and also participates in a feedback amplification loop. Our results provide evidence that Apaf-1 and caspase-3 are major determinants of ErPC-induced apoptosis and the possible use of ErPC in a clinical setting is discussed.

Topics: Apoptosis; Apoptotic Protease-Activating Factor 1; BH3 Interacting Domain Death Agonist Protein; Breast Neoplasms; Caspase 3; Caspases; Cell Line, Tumor; Cell Proliferation; Down-Regulation; Glioblastoma; Humans; Intracellular Signaling Peptides and Proteins; Phosphorylcholine; Proteins; Proto-Oncogene Proteins c-bcl-2; RNA Interference

Erucylphosphocholine (ErPC) is a promising antineoplastic drug for the treatment of malignant brain tumors. It exerts strong anticancer activity and induces apoptosis even in chemoresistant glioma cells. In the present study, A172 and U373MG glioma cells were treated with ErPC to explore the contribution of MAP kinase family members ERK, JNK and p38 kinase to ErPC-induced cell death. The exposure to ErPC led to activation of JNK and concurrent inhibition of ERK in both cell lines. Using specific MAP kinase inhibitors we confirmed that in U373MG cells ERK was blocked and JNK was activated upon ErPC treatment. Both effects were dependent on caspase activation. In A172 cells, ErPC treatment resulted in an activation of the JNK pathway, whereas the situation with respect to ERK signalling was more complex. We conclude that inhibition of the ERK pathway by ErPC may be related to antiproliferative effects, while activation of the JNK pathway may be responsible for its pro-apoptotic action.

Topics: Brain Neoplasms; Cell Proliferation; Extracellular Signal-Regulated MAP Kinases; Glioblastoma; Humans; JNK Mitogen-Activated Protein Kinases; Phosphorylcholine; Signal Transduction; Tumor Cells, Cultured

Erucylphosphocholine (ErPC) is a promising candidate for the treatment of human brain tumors. The aim of the present study was to investigate whether structural modifications of ErPC would improve its antineoplastic activity in vitro. The novel alkylphosphocholine (APC) derivatives docosenyl-( cis-10,11)-phosphocholine, tricosenyl-( cis-12,13)-phosphocholine, heneicosenyl-( cis-12,13)-phosphocholine and erucyl- N, N, N-trimethylpropanolaminophosphate all reduced cell growth and viability of rat and human astrocytoma/glioblastoma (AC/GBM) cell lines (C6, T98G, U87MG, A172) and had improved antineoplastic activity when compared to the prototypical APC hexadecylphosphocholine (HePC). However, the four cell lines differed in their sensitivity to the APC derivatives. A172 cells were most sensitive to their cytostatic action and T98G cells to their cytotoxic action. The LC(50) values for T98G cells after a 72-h exposure to the novel derivatives varied between 25 and 54 microM compared to 45+/-8.1 microM for ErPC. Complete killing of T98G cells was obtained with all derivatives at 90 microM. Structural modifications of the chain length of the alcohol moiety as well as changing the position of the double bond within the alkyl chain improved cytotoxicity of the APC in C6 and A172 cells and to a lesser extent in T98G cells, whereas U87MG cells showed almost similar sensitivities to the novel drugs and ErPC. Increasing the distance between the phosphorus and nitrogen atoms within the polar phosphocholine group did not alter antineoplastic activity but modified physicochemical characteristics, e.g. increased the solubility in water. In a similar manner to ErPC, all derivatives induced growth arrest in the G(2)/M phase of the cell cycle and apoptotic cell death. Importantly, none of the derivatives showed hemolytic activity. As there was no clear superiority of any of the novel derivatives, ErPC remains the leading APC derivative for future clinical trials in brain tumor chemotherapy.

Topics: Animals; Antineoplastic Agents; Apoptosis; Brain Neoplasms; Cell Cycle; Cell Division; Cell Survival; Glioblastoma; Hemolysis; Humans; Male; Phosphorylcholine; Rats; Structure-Activity Relationship; Tumor Cells, Cultured