ROS-mediated EB1 phosphorylation through Akt/GSK3β pathway: implication in cancer cell response to microtubule-targeting agents

International audienceMicrotubule-targeting agents (MTAs) are largely administered in adults and children cancers. Better deciphering their mechanism of action is of prime importance to develop more convenient therapy strategies. Here, we addressed the question of how reactive oxygen species (ROS) generation by mitochondria can be necessary for MTA efficacy. We showed for the first time that EB1 associates with microtubules in a phosphorylation-dependent manner, under control of ROS. By using phospho-defective mutants, we further characterized the Serine 155 residue as critical for EB1 accumulation at microtubule plus-ends, and both cancer cell migration and proliferation. Phosphorylation of EB1 on the Threonine 166 residue triggered opposite effects, and was identified as a requisite molecular switch in MTA activities. We then showed that GSK3β activation was responsible for MTA-triggered EB1 phosphorylation, resulting from ROS-mediated inhibition of upstream Akt. We thus disclosed here a novel pathway by which generation of mitochondrial ROS modulates microtubule dynamics through phosphorylation of EB1, improving our fundamental knowledge about this oncogenic protein, and pointing out the need to reexamine the current dogma of microtubule targeting by MTAs. The present work also provides a strong mechanistic rational to the promising therapeutic strategies that currently combine MTAs with anti-Akt targeted therapies

4-oxo-N-(4-hydroxyphenyl)retinamide: Two Independent Ways to Kill Cancer Cells

BACKGROUND: The retinoid 4-oxo-N-(4-hydroxyphenyl)retinamide (4-oxo-4-HPR) is a polar metabolite of fenretinide (4-HPR) very effective in killing cancer cells of different histotypes, able to inhibit 4-HPR-resistant cell growth and to act synergistically in combination with the parent drug. Unlike 4-HPR and other retinoids, 4-oxo-4-HPR inhibits tubulin polymerization, leading to multipolar spindle formation and mitotic arrest. Here we investigated whether 4-oxo-4-HPR, like 4-HPR, triggered cell death also via reactive oxygen species (ROS) generation and whether its antimicrotubule activity was related to a ROS-dependent mechanism in ovarian (A2780), breast (T47D), cervical (HeLa) and neuroblastoma (SK-N-BE) cancer cell lines. METHODOLOGY/PRINCIPAL FINDINGS: We provided evidence that 4-oxo-4-HPR, besides acting as an antimicrotubule agent, induced apoptosis through a signaling cascade starting from ROS generation and involving endoplasmic reticulum (ER) stress response, Jun N-terminal Kinase (JNK) activation, and upregulation of the proapoptotic PLAcental Bone morphogenetic protein (PLAB). Through time-course analysis and inhibition of the ROS-related signaling pathway (upstream by vitamin C and downstream by PLAB silencing), we demonstrated that the antimitotic activity of 4-oxo-4-HPR was independent from the oxidative stress induced by the retinoid. In fact, ROS generation occurred earlier than mitotic arrest (within 30 minutes and 2 hours, respectively) and abrogation of the ROS-related signaling pathway did not prevent the 4-oxo-4-HPR-induced mitotic arrest. CONCLUSIONS/SIGNIFICANCE: These data indicate that 4-oxo-4-HPR anticancer activity is due to at least two independent mechanisms and provide an explanation of the ability of 4-oxo-4-HPR to be more potent than the parent drug and to be effective also in 4-HPR-resistant cell lines. In addition, the double mechanism of action could allow 4-oxo-4-HPR to efficiently target tumour and to eventually counteract the development of drug resistance

Upregulation of Cellular Bcl-2 by the KSHV Encoded RTA Promotes Virion Production

Apoptosis of virus infected cells can restrict or dampen full blown virus propagation and this can serve as a protective mechanism against virus infection. Consequently, viruses can also delay programmed cell death by enhancing the expression of anti-apoptotic proteins. Human Bcl-2 is expressed on the surface of the mitochondrial membrane and functions as the regulator of the delicate balance between cell survival and apoptosis. In this report, we showed that the replication and transcription activator (RTA) encoded by KSHV ORF 50, a key regulator for KSHV reactivation from latent to lytic infection, upregulates the mRNA and protein levels of Bcl-2 in 293 cells, and TPA-induced KSHV-infected cells. Further analysis revealed that upregulation of the cellular Bcl-2 promoter by RTA is dose-dependent and acts through targeting of the CCN9GG motifs within the Bcl-2 promoter. The Bcl-2 P2 but not the P1 promoter is primarily responsive to RTA. The results of ChIP confirmed the direct interaction of RTA protein with the CCN9GG motifs. Knockdown of cellular Bcl-2 by lentivirus-delivered small hairpin RNA (shRNA) resulted in increased cell apoptosis and decreased virion production in KSHV-infected cells. These findings provide an insight into another mechanism by which KSHV utilizes the intrinsic apoptosis signaling pathways for prolonging the survival of lytically infected host cells to allow for maximum production of virus progeny

Evolution de la prise en charge du cancer du sein

AIX-MARSEILLE2-BU Pharmacie (130552105) / SudocSudocFranceF

Que peut apporter le pharmacien d'officine à la prise en charge du cancer du sein ?

AIX-MARSEILLE2-BU Pharmacie (130552105) / SudocSudocFranceF

L'ONCOGENE C-MYC (IMPORTANCE ET ACTION DES AGENTS ANTICANCEREUX SUR SON EXPRESSION)

AIX-MARSEILLE2-BU Pharmacie (130552105) / SudocSudocFranceF

Intérêt de l'utilisation des plantes transgéniques pour la production des biomédicaments

AIX-MARSEILLE2-BU Pharmacie (130552105) / SudocSudocFranceF

Mécanismes anti-angiogéniques d'un vinca-alcaloïde, la vinflunine

AIX-MARSEILLE2-BU Pharmacie (130552105) / SudocSudocFranceF