Search

15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2), one of the terminal products of cyclooxygenase-2-catalized arachidonic acid metabolism, has been shown to stimulate breast cancer cell proliferation and migration through Akt activation, but the underlying mechanisms remain poorly understood. In the present study, we investigated the effects of 15d-PGJ2 on the activity of PTEN, the inhibitor of the phosphoinositide 3-kinase (PI3K)-Akt axis, in human breast cancer (MCF-7) cells. Since the α,β-unsaturated carbonyl moiety in the cyclopentenone ring of 15d-PGJ2 is electrophilic, we hypothesized that 15d-PGJ2-induced Akt phosphorylation might result from the covalent modification and subsequent inactivation of PTEN that has several critical cysteine residues. When treated to MCF-7 cells, 15d-PGJ2 bound to PTEN, and this was abolished in the presence of the thiol-reducing agent dithiothreitol. A mass spectrometric analysis by using recombinant and endogenous PTEN protein revealed that the cysteine 136 residue (Cys136) of PTEN is covalently modified upon treatment with 15d-PGJ2. Notably, the ability of 15d-PGJ2 to covalently bind to PTEN as well as to induce Akt phosphorylation was abolished in the cells expressing a mutant form of PTEN in which Cys136 was replaced by serine (C136S-PTEN). The present study demonstrates for the first time that electrophilic 15d-PGJ2 directly binds to cysteine 136 of PTEN and provides new insight into PTEN loss in cancer progression associated with chronic inflammation. These observations suggest that 15d-PGJ2 can undergo nucleophilic addition to PTEN, presumably at Cys136, thereby inactivating this tumor suppressor protein with concomitant Akt activation. [ABSTRACT FROM AUTHOR]

15-Deoxy-Δ12,14-prostaglandin J2(15d-PGJ2), a representative J-series cyclopentenone prostaglandin, has biphasic roles in cell proliferation and apoptosis. Hypoxia inducible factor-1 (HIF-1) regulates expression of various genes involved in tumor growth and angiogenesis. In the present study, treatment of human breast cancer (MCF-7) cells with 15d-PGJ2resulted in the accumulation of the α-subunit of HIF-1. Pretreatment with zinc protoporphyrin IX, a pharmacological inhibitor of heme oxygenase-1 (HO-1), as well as siRNA knockdown ofHO-1gene in MCF-7 cells attenuated 15d-PGJ2-mediated HIF-1α accumulation. 15d-PGJ2treatment increased intracellular production of reactive oxygen species (ROS), which was mediated by HO-1 induction. Preincubation of MCF-7 cells with trolox, a water-soluble form of vitamin E, attenuated 15d-PGJ2-induced HIF-1α expression although HO-1 expression was unchanged. This finding suggests that ROS accumulated as a consequence of HO-1 up-regulation can enhance HIF-1α expression in MCF-7 cells treated with 15d-PGJ2. Alternatively, 15d-PGJ2was found to covalently bind to HIF-1α prolyl-4-hydroxylase 2 (PHD2) in MCF-7 cells, which hampers the proline hydroxylation of HIF-1α, thereby disrupting ubiquitin-dependent proteasomal degradation of this transcription factor. Pretreatment with thiol reducing agents blunted 15d-PGJ2-induced HIF-1α stabilization, indicative of a cysteine residue as a direct target of 15d-PGJ2. Molecular docking analysis suggests that 15d-PGJ2preferentially binds to PHD2 in the vicinity of the Cys201residue based on binding energies and carbon–sulfur distances. In summary, 15d-PGJ2stabilizes HIF-1α in MCF-7 cells through HO-1 induction with subsequent ROS generation and also through direct modification of PHD2. [ABSTRACT FROM AUTHOR]

15-Deoxy-Δ 12,14 -prostaglandin J 2 (15d-PGJ 2 ), a representative J-series cyclopentenone prostaglandin, has biphasic roles in cell proliferation and apoptosis. Hypoxia inducible factor-1 (HIF-1) regulates expression of various genes involved in tumor growth and angiogenesis. In the present study, treatment of human breast cancer (MCF-7) cells with 15d-PGJ 2 resulted in the accumulation of the α-subunit of HIF-1. Pretreatment with zinc protoporphyrin IX, a pharmacological inhibitor of heme oxygenase-1 (HO-1), as well as siRNA knockdown of HO-1 gene in MCF-7 cells attenuated 15d-PGJ 2 -mediated HIF-1α accumulation. 15d-PGJ 2 treatment increased intracellular production of reactive oxygen species (ROS), which was mediated by HO-1 induction. Preincubation of MCF-7 cells with trolox, a water-soluble form of vitamin E, attenuated 15d-PGJ 2 -induced HIF-1α expression although HO-1 expression was unchanged. This finding suggests that ROS accumulated as a consequence of HO-1 up-regulation can enhance HIF-1α expression in MCF-7 cells treated with 15d-PGJ 2 . Alternatively, 15d-PGJ 2 was found to covalently bind to HIF-1α prolyl-4-hydroxylase 2 (PHD2) in MCF-7 cells, which hampers the proline hydroxylation of HIF-1α, thereby disrupting ubiquitin-dependent proteasomal degradation of this transcription factor. Pretreatment with thiol reducing agents blunted 15d-PGJ 2 -induced HIF-1α stabilization, indicative of a cysteine residue as a direct target of 15d-PGJ 2 . Molecular docking analysis suggests that 15d-PGJ 2 preferentially binds to PHD2 in the vicinity of the Cys 201 residue based on binding energies and carbon-sulfur distances. In summary, 15d-PGJ 2 stabilizes HIF-1α in MCF-7 cells through HO-1 induction with subsequent ROS generation and also through direct modification of PHD2.