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Involvement of PAR-4 in cannabinoid-dependent sensitization of osteosarcoma cells to TRAIL-induced apoptosis.

Notaro A, Sabella S, Pellerito O, Di Fiore R, De Blasio A, Vento R, Calvaruso G, Giuliano M - Int. J. Biol. Sci. (2014)

Bottom Line: In treated cells we also observed the conversion of the cytosolic form of the autophagosome marker LC3-I into LC3-II (the lipidated form located on the autophagosome membrane) and the enhanced incorporation of monodansylcadaverine and acridine orange, two markers of the autophagic compartments such as autolysosomes.WIN also induced morphological effects in MG63 cells consisting in an increase in cell size and a marked cytoplasmic vacuolization.However, WIN effects were not associated with a canonical apoptotic pathway, as demonstrated by the absence of specific features, and only the addition of TRAIL to WIN-treated cells led to apoptotic death probably mediated by up-regulation of the tumor suppressor factor PAR-4, whose levels increased after WIN treatment, and by the translocation of GRP78 on cell surface.

View Article: PubMed Central - PubMed

Affiliation: 1. Laboratory of Biochemistry, Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo, Polyclinic, Palermo, Italy.

ABSTRACT
The synthetic cannabinoid WIN 55,212-2 is a potent cannabinoid receptor agonist with anticancer potential. Experiments were performed to determine the effects of WIN on proliferation, cell cycle distribution, and programmed cell death in human osteosarcoma MG63 and Saos-2 cells. Results show that WIN induced G2/M cell cycle arrest, which was associated with the induction of the main markers of ER stress (GRP78, CHOP and TRB3). In treated cells we also observed the conversion of the cytosolic form of the autophagosome marker LC3-I into LC3-II (the lipidated form located on the autophagosome membrane) and the enhanced incorporation of monodansylcadaverine and acridine orange, two markers of the autophagic compartments such as autolysosomes. WIN also induced morphological effects in MG63 cells consisting in an increase in cell size and a marked cytoplasmic vacuolization. However, WIN effects were not associated with a canonical apoptotic pathway, as demonstrated by the absence of specific features, and only the addition of TRAIL to WIN-treated cells led to apoptotic death probably mediated by up-regulation of the tumor suppressor factor PAR-4, whose levels increased after WIN treatment, and by the translocation of GRP78 on cell surface.

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Suggested model of the mechanism of WIN/TRAIL-induced apoptosis on osteosarcoma MG63 cells.
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Figure 7: Suggested model of the mechanism of WIN/TRAIL-induced apoptosis on osteosarcoma MG63 cells.

Mentions: Taken together, although some important questions remain to be further clarified, here we hypothesize a novel mechanism, described in Fig. 7, through which WIN induces ER stress-dependent activation of autophagy and, in the same time, increases PAR-4 level and GRP78 translocation on cell surface. These events, together with autophagy-mediated activation of caspase-8, could contribute to the formation of a membrane microdomain and be responsible, directly or indirectly, for the sensitization to TRAIL action.


Involvement of PAR-4 in cannabinoid-dependent sensitization of osteosarcoma cells to TRAIL-induced apoptosis.

Notaro A, Sabella S, Pellerito O, Di Fiore R, De Blasio A, Vento R, Calvaruso G, Giuliano M - Int. J. Biol. Sci. (2014)

Suggested model of the mechanism of WIN/TRAIL-induced apoptosis on osteosarcoma MG63 cells.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4007360&req=5

Figure 7: Suggested model of the mechanism of WIN/TRAIL-induced apoptosis on osteosarcoma MG63 cells.
Mentions: Taken together, although some important questions remain to be further clarified, here we hypothesize a novel mechanism, described in Fig. 7, through which WIN induces ER stress-dependent activation of autophagy and, in the same time, increases PAR-4 level and GRP78 translocation on cell surface. These events, together with autophagy-mediated activation of caspase-8, could contribute to the formation of a membrane microdomain and be responsible, directly or indirectly, for the sensitization to TRAIL action.

Bottom Line: In treated cells we also observed the conversion of the cytosolic form of the autophagosome marker LC3-I into LC3-II (the lipidated form located on the autophagosome membrane) and the enhanced incorporation of monodansylcadaverine and acridine orange, two markers of the autophagic compartments such as autolysosomes.WIN also induced morphological effects in MG63 cells consisting in an increase in cell size and a marked cytoplasmic vacuolization.However, WIN effects were not associated with a canonical apoptotic pathway, as demonstrated by the absence of specific features, and only the addition of TRAIL to WIN-treated cells led to apoptotic death probably mediated by up-regulation of the tumor suppressor factor PAR-4, whose levels increased after WIN treatment, and by the translocation of GRP78 on cell surface.

View Article: PubMed Central - PubMed

Affiliation: 1. Laboratory of Biochemistry, Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo, Polyclinic, Palermo, Italy.

ABSTRACT
The synthetic cannabinoid WIN 55,212-2 is a potent cannabinoid receptor agonist with anticancer potential. Experiments were performed to determine the effects of WIN on proliferation, cell cycle distribution, and programmed cell death in human osteosarcoma MG63 and Saos-2 cells. Results show that WIN induced G2/M cell cycle arrest, which was associated with the induction of the main markers of ER stress (GRP78, CHOP and TRB3). In treated cells we also observed the conversion of the cytosolic form of the autophagosome marker LC3-I into LC3-II (the lipidated form located on the autophagosome membrane) and the enhanced incorporation of monodansylcadaverine and acridine orange, two markers of the autophagic compartments such as autolysosomes. WIN also induced morphological effects in MG63 cells consisting in an increase in cell size and a marked cytoplasmic vacuolization. However, WIN effects were not associated with a canonical apoptotic pathway, as demonstrated by the absence of specific features, and only the addition of TRAIL to WIN-treated cells led to apoptotic death probably mediated by up-regulation of the tumor suppressor factor PAR-4, whose levels increased after WIN treatment, and by the translocation of GRP78 on cell surface.

Show MeSH
Related in: MedlinePlus