| Ovarian cancer is one of the most common gynecological malignant tumor as it is difficult to detect at early phase, poor treatment effection, poor prognosis and high mortality rate. Molecular Chaperone is a kind of protein that combined with some unstable conformation of proteins to stabilize them, through regulating binding and releaseing peptide inside cells, which cause the folding, assembly, transport, and degradation and so on, to maintaining cellular homeostasis. Mortalin, also known as Grp75/PBP74/mthsp70, is one of the members of the HSP70 molecular partners. It is extensive distributed in multiple between organelles and cytoplasm, involved in cell proliferation and intracellular transport, control stress reaction, stabilize the cytoskeleton, inhibiting cell apoptosis, etc. Research found in many tumors, such as chronic myelogenous leukemia, colon, brain tumor, breast cancer and liver cancer mortalin expression.Overexpression of mortalin can increase the degree of malignant breast cancer cells, to participate in the lier.Mortalin, a molecular chaperon of HSP70 family, is an essential protein that performs various functions related to stress responses, intracellular transport, mitochondrial transportion and energy production and regulation and differentiation, protect and promote the tumor cells growth through the antiapoptotic function. Enriched of mortalin has been reported in several malignant cancers, including breast cancer, brain cancer, colorectal adenocarcinoma and so on. Elevated levels of mortalin expression contributes to tumorgenesis and drug resistance by its antiapototic function. But, the relationship between mortalin and ovarian cancer is known little.Previously study showed that mortalin is overexpressed in ovarian cancer and mortalin overexpression might be concerned with the staging of ovarian cancer, the higher stage of ovarian cancer, the higher of mortalin expression through 183 ovarian cancer tissue microarray. So we speculated that high expression of mortal may participate in the development of ovarian cancer.Compared with low-grade ovarian cancer cell lines (OV-90), metastatic tumor cell (COC1) and cisplatin resistant ovarian cancer cell (A2780/cis) have a high expression of mortalin in 8 ovarain cancer cell lines A2780/cis, COC1, HO-8910, PM-8910, OV-90, Caov-3, SKOV-3 and ES-2, respectively in the expression of protein level and mRNA level. Previously study showed that protein expression level of mortalin was also higher in cisplatin-resistant A2780/cis cells than in cisplatin-sensitive A2780 cells. This result illustrates that the expression of mortalin is associated with the level of malignancy.Next, A2780 cells were infected with lentiviral mortalin or a control lentiviral vector pLVX-AcGFP to construct mortalin high expression cell lines, and shRNA was employed to silence mortalin expression in A2780 and A2780/cis. Trough CCK-8 cell proliferation assay, colony formation assay, cell migration and invasion assay, mortalin overexpression clones in A2780 cells were significantly present higher growth rate and formed much larger clones than their vector controls, promoted ovarian cancer cell metastasis. In reverse, depletion of endogenous mortalin in A2780 and A2780/cis cells remarkably slowed down ovarian cancer cell proliferation and its metastasis compared with their scrambled controls.Cell cycle analysis used by flow cytometry showed that cells with lower level mortalin cells sequentially proceed through S and G2/M phase, approaching normal distribution of the cell phase at 48 h. On the contrary, higher level mortalin cells lead to a faster overriding through the G1 phase to the G2/M phase of cell cycle at 24h. This data suggested that mortalin promotes G1 transition, leading to a faster restoration of the normal distribution of cell cycle. In addition, Western blot analyses also demonstrate that both Cyclin-D1 and C-myc elevated, and Cyclin-B1 dereased in mortalin stably overexpressing ovarian cancer cells. In contrast, knockdown of mortalin outstandingly reduced the expressions of Cyclin-D1 and C-myc, and upregulated Cyclin-B1 level compared to their control cells.To explore the major molecular events induced by the varied mortalin expression, many antibodies were chosen from cell signaling pathways in altered mortalin cell lines. We validated the upregulation of p-ERK and p-c-Raf alone with the upregulation of mortalin. PARP was also observed along with cell death. Consistent with the observed effect of mortalin overexpression, reduction of the p-c-Raf and p-ERK1/2 occurred in mortalin knockdown model although total protein level remained unchanged. However, the expression of both JNK and p-JNK seems have no oblivious change.In conclusion, our findings suggest that mortalin plays an important role in ovarian cancer development and progression by promoting tumor growth and migration/invasion in aggressive high-grade ovarian cancer, and mortalin is involved in the modulation of MAPK-ERK signaling. Ovarian cancer cell growth and survival can be vitiated by the inactivation of mortalin, suggesting that mortalin can be used as a potential target for the treatment of ovarian cancer. |
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