Teresa Pecere

Involvement of p53 in specific anti-neuroectodermal tumor activity of aloe-emodin

Previously, we have identified aloe‐emodin (AE) as a new type of anticancer agent, with activity that is based on apoptotic cell death promoted by a neuroectodermal tumor‐specific drug uptake. We attempt to clarify the intracellular target of AE and the apoptosis‐signaling pathway activated by AE in neuroblastoma cell lines. Two‐photon excitation microscopy and spectroscopic titrations documented that AE is highly concentrated in susceptible cells and binds to DNA. One of the most important mediators of apoptotic response to genotoxic stimuli, such as anticancer agents, is the p53 tumor suppressor gene. To evaluate the role played by p53 in AE‐induced apoptosis a p53 mutant cell line, which lacks transcriptional activity of p53 targeted genes, was tested. AE displayed a reduced growth inhibitory and pro‐apoptotic activity in p53 mutant cells (SK‐N‐BE(2c)) with respect to the p53 wild‐type line (SJ‐N‐KP). This effect was not caused by a reduced drug uptake in the mutant neuroblastoma cell line but was related to a different apoptotic cell phenotype. Whereas SJ‐N‐KP cells were susceptible to a p53 transcription‐dependent pathway of apoptosis, SK‐N‐BE(2c) cells underwent apoptosis with up‐regulation of p53 expression but not of p53‐target genes. After AE treatment p53 translocates to the mitochondria inter‐membrane space in both neuroblastoma cell lines. Due to its high accumulation in neuroectodermal tumor cells AE could also kill tumor cells harboring p53 mutant genes. This property would further contribute to AE specific anti‐tumor activity and might be exploitable in the clinic.

New anti-human immunodeficiency virus type 1 6-aminoquinolones: Mechanism of action

ABSTRACT A 6-aminoquinolone derivative, WM5, which bears a methyl substituent at the N-1 position and a 4-(2-pyridyl)-1-piperazine moiety at position 7 of the bicyclic quinolone ring system, was previously shown to exhibit potent activity against replication of human immunodeficiency virus type 1 (HIV-1) in de novo-infected human lymphoblastoid cells (V. Cecchetti et al., J. Med. Chem. 43:3799-3802, 2000). In this report, we further investigated WM5s mechanism of antiviral activity. WM5 inhibited HIV-1 replication in acutely infected cells as well as in chronically infected cells. The 50% inhibitory concentrations were 0.60 ± 0.06 and 0.85 ± 0.05 μM, respectively. When the effects of WM5 on different steps of the virus life cycle were analyzed, the reverse transcriptase activity and the integrase and protease activities were not impaired. By using a transient trans-complementation assay to examine the activity of WM5 on the replicative potential of HIV-1 in a single round of infection, a sustained inhibition of Tat-mediated long terminal repeat (LTR)-driven transcription (>80% of controls) was obtained in the presence of 5 μM WM5. Interestingly, the aminoquinolone was found to efficiently complex TAR RNA, with a dissociation constant in the nanomolar range (19 ± 0.6 nM). These data indicate that WM5 is a promising lead compound for the development of a new class of HIV-1 transcription inhibitors characterized by recognition of viral RNA target(s).