Daniela Baiocchi

Cell fate decisions are specified by the dynamic ERK interactome.

Extracellular signal-regulated kinase (ERK) controls fundamental cellular functions, including cell fate decisions. In PC12, cells shifting ERK activation from transient to sustained induces neuronal differentiation. As ERK associates with both regulators and effectors, we hypothesized that the mechanisms underlying the switch could be revealed by assessing the dynamic changes in ERK-interacting proteins that specifically occur under differentiation conditions. Using quantitative proteomics, we identified 284 ERK-interacting proteins. Upon induction of differentiation, 60 proteins changed their binding to ERK, including many proteins that were not known to participate in differentiation. We functionally characterized a subset, showing that they regulate the pathway at several levels and by different mechanisms, including signal duration, ERK localization, feedback, crosstalk with the Akt pathway and differential interaction and phosphorylation of transcription factors. Integrating these data with a mathematical model confirmed that ERK dynamics and differentiation are regulated by distributed control mechanisms rather than by a single master switch.

Design, Synthesis, and Biological Evaluation of Substituted Naphthalene Imides and Diimides as Anticancer Agent∞

Naphthalimmide (NI) and 1,4,5,8-naphthalentetracarboxylic diimide (NDI) derivatives were synthesized and evaluated for their antiproliferative activity. NDI derivatives 1-9 were more cytotoxic than the corresponding NI derivatives 10-18. The molecular mechanisms of 1 and 2 were investigated in comparison to mitonafide. They interacted with DNA, were not topoisomerase IIalpha poisons, triggered caspase activation, caused p53 protein accumulation, and down-regulated AKT survival. Furthermore, 1 and 2 caused a decrease of ERK1/2 and, unlike mitonafide, inhibited ERKs phosphorylation.

Abstract C84: Inhibition of cholesterol esterification by fenretinide in osteosarcoma in vitro

Osteosarcoma remains the most common primary malignant bone cancer affecting children and adolescents. Although the combination of systemic chemotherapy and surgery enables long‐term survival in most cases, the poor prognosis of patients with metastatic or recurrent disease and the lack of establishment of second‐line chemotherapy suggest that novel therapeutic strategies for this tumor are needed. Here we show that fenretinide, a synthetic derivative of all‐trans‐retinoic acid, is active against osteosarcoma in vitro, at concentrations identical or lower to those detectable in breast cancer patients plasma during chemopreventive clinical trials. Cell lines were HOS and MG63, known to be resistant to methotrexate and cyclophosphamide, drugs in use in osteosarcoma treatment. We demonstrate for the first time that fenretinide is active in this tumor and that the molecular basis of fenretinide activity is the inhibition of cholesterol esterification, with down‐regulation of ACAT and MDR1 mRNA, followed by downregulation of caveolin‐1 protein expression. This result is in line with our recent results obtained in VSMC and in leukemia cells. The confirmation and extention of these data to different human tumors will provide evidence of a novel mechanism of either cancer or human vascular proliferation disease control by the inhibition of cholesterol esterification. Grants from MIUR, Carisbo Foundation, Pallotti9s Legacy for Cancer Research and University of Bologna. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C84.