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This study demonstrated that coronopilin efficiently inhibited leukaemia cell population growth by triggering cell type-specific responses. Moreover, coronopilin-mediated cell population expansion inhibition was specific to neoplastic cells, as normal white blood cell viability was not significantly affected. Thus, coronopilin may represent an interesting new chemical scaffold upon which to develop new anti-leukaemic agents.

Rimonabant (SR141716), a cannabinoid CB1 receptor antagonist known for anti-obesity activity, has more recently been shown to inhibit tumor cell growth. Here we demonstrated the anti-tumor potential of SR141716 in leukemia-derived cell lines and its low toxicity in normal cells (PBMC). SR141716(1-20 M range of doses) reduced Jurkat and U937 cell number by activating death signals as well as affecting cell cycle progression. The most prominent response in U937 to SR141716 was a G 0 /G 1 block, while in Jurkat cells there was activation of cell death processes.SR141716-treated cells exhibited the morphological and biochemical features of apoptosis and to some extent necrosis. Apoptotic mode of cell death was confirmed in both cell lines by analysis of cell morphology, phosphatidylserine exposure and DNA fragmentation. Moreover, the drug was found to induce an early and robust mitochondrial membrane depolarization. In Jurkat cells the apoptotic process was typically caspase-dependent, while in U937 caspase-independent pathways were also activated. The contribution of PARP activation to SR141716-induced apoptosis in U937 was suggested by protein PARylation, AIF release and apoptosis reversal by PARP inhibitors.Moreover, SR141716 negatively modulated, especially in U937, the PI3K/AKT pathways. In conclusion, our data indicate that SR141716 elicits alternative response and/or cell death pathways depending on the cell type affected.

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In human cancer cells, BAG3 protein is known to sustain cell survival. Here, for the first time, we demonstrate the expression of BAG3 protein both in equine sarcoids in vivo and in EqS04b cells, a sarcoid-derived fully transformed cell line harbouring bovine papilloma virus (BPV)-1 genome. Evidence of a possible involvement of BAG3 in equine sarcoid carcinogenesis was obtained by immunohistochemistry analysis of tumour samples. We found that most tumour samples stained positive for BAG3, even though to a different grade, while normal dermal fibroblasts from healthy horses displayed very weak staining pattern for BAG3 expression. By siRNA technology, we demonstrate in EqS04b the role of BAG3 in counteracting basal as well as chemical-triggered pro-death signals. BAG3 down-modulation was indeed shown to promote cell death and cell cycle arrest in G0/G1. In addition, we found that BAG3 silencing sensitized EqS04b cells to phenethylisothiocyanate (PEITC), a promising cancer chemopreventive/chemotherapeutic agent present in edible cruciferous vegetables. Notably, such a pro-survival role of BAG3 was less marked in E. Derm cells, an equine BPV-negative fibroblast cell line taken as a normal counterpart. Altogether our findings might suggest a mutual cooperation between BAG3 and viral oncoproteins to sustain cell survival.

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BAG3 is a multi-functional component of tumor cell pro-survival machinery, and its biological functions have been largely associated to proteasome system. Here, we show that BAG3 down-modulation resulted in reduced cell viability and enhanced PEITC-induced apoptosis largely more extensively in HeLa (HPV18(+)) rather than in C33A (HPV(-)) cervical carcinoma cell lines. Moreover, we demonstrate that BAG3 suppression led to a decrease of viral E6 oncoprotein and a concomitant recovery of p53 tumor suppressor, the best recognized target of E6 for proteasome degradation. E6 and p53 expression were modulated at protein level, since their respective mRNAs were unaffected. Taken together our findings reveal a novel role for BAG3 as host protein contributing to HPV18 E6-activated pro-survival strategies, and suggest a possible relevance of its expression levels in drug/radiotherapy-resistance of HPV18-bearing cervical carcinomas.