ABSTRACT
Autophagy can sustain or kill tumor cells depending upon the context. The mechanism of autophagy-associated cell death has not been well elucidated and autophagy has enhanced or inhibited sensitivity of cancer cells to cytotoxic chemotherapy in different models. ARHI (DIRAS3), an imprinted tumor suppressor gene, is downregulated in 60% of ovarian cancers. In cell culture, re-expression of ARHI induces autophagy and ovarian cancer cell death within 72 h. In xenografts, re-expression of ARHI arrests cell growth and induces autophagy, but does not kill engrafted cancer cells. When ARHI levels are reduced after 6 weeks, dormancy is broken and xenografts grow promptly. In this study, ARHI-induced ovarian cancer cell death in culture has been found to depend upon autophagy and has been linked to G1 cell-cycle arrest, enhanced reactive oxygen species (ROS) activity, RIP1/RIP3 activation and necrosis. Re-expression of ARHI enhanced the cytotoxic effect of cisplatin in cell culture, increasing caspase-3 activation and PARP cleavage by inhibiting ERK and HER2 activity and downregulating XIAP and Bcl-2. In xenografts, treatment with cisplatin significantly slowed the outgrowth of dormant autophagic cells after reduction of ARHI, but the addition of chloroquine did not further inhibit xenograft outgrowth. Taken together, we have found that autophagy-associated cancer cell death and autophagy-enhanced sensitivity to cisplatin depend upon different mechanisms and that dormant, autophagic cancer cells are still vulnerable to cisplatin-based chemotherapy.
Subject(s)
Antineoplastic Agents/pharmacology , Autophagy/drug effects , Cisplatin/pharmacology , Drug Resistance, Neoplasm/drug effects , Gene Expression Regulation, Neoplastic , Ovarian Neoplasms/drug therapy , rho GTP-Binding Proteins/genetics , Autophagy/genetics , Caspase 3/genetics , Caspase 3/metabolism , Cell Line, Tumor , Chloroquine/pharmacology , Drug Resistance, Neoplasm/genetics , Female , G1 Phase Cell Cycle Checkpoints/drug effects , Humans , Mitogen-Activated Protein Kinase 1/genetics , Mitogen-Activated Protein Kinase 1/metabolism , Mitogen-Activated Protein Kinase 3/genetics , Mitogen-Activated Protein Kinase 3/metabolism , Nuclear Pore Complex Proteins/genetics , Nuclear Pore Complex Proteins/metabolism , Ovarian Neoplasms/genetics , Ovarian Neoplasms/metabolism , Ovarian Neoplasms/pathology , Poly(ADP-ribose) Polymerases/genetics , Poly(ADP-ribose) Polymerases/metabolism , Proteolysis , Proto-Oncogene Proteins c-bcl-2/genetics , Proto-Oncogene Proteins c-bcl-2/metabolism , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , Reactive Oxygen Species/metabolism , Receptor, ErbB-2/genetics , Receptor, ErbB-2/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Signal Transduction , X-Linked Inhibitor of Apoptosis Protein/genetics , X-Linked Inhibitor of Apoptosis Protein/metabolism , Xenograft Model Antitumor Assays , rho GTP-Binding Proteins/metabolismABSTRACT
BACKGROUND: The aim of this study was to determine whether DNA-associated micro-particles (MPs) in maternal plasma express fetal-derived human leukocyte antigen-G (HLA-G) or placental alkaline phosphatase (PLAP) and whether the levels differ between women with normotensive pregnancies and preeclampsia. METHODS: DNA-associated MPs expressing HLA-G or PLAP were examined in the plasma of normal pregnant women and preeclamptic patients using flow cytometric analysis. RESULTS: DNA-associated HLA-G(+) MPs were significantly increased in maternal plasma compared to plasma from non-pregnant controls (p<0.005), with highest levels found in the first and second trimesters. DNA-associated PLAP(+) MPs were also increased in maternal plasma compared to plasma from non-pregnant controls (p<0.006), with highest levels in the second and third trimesters. Term preeclamptic women had higher levels of DNA-associated MPs than control pregnant women. HLA-G(+) MPs from the plasma of preeclamptic women had more DNA per MP than HLA-G(+) MPs from the plasma of normal pregnant women (p<0.03). CONCLUSIONS: HLA-G(+) and PLAP(+) MPs increase in maternal circulation at different times during gestation. DNA amounts per HLA-G(+) MP increase in preeclamptic women which might indicate dysfunctional extravillous cytotrophoblasts.
