Hypoxia induced paclitaxel resistance in human ovarian cancers via hypoxia-inducible factor 1α
ABSTRACT Chemoresistance severely restricts the anti-cancer medicines from effectively treating human ovarian cancer, which has been shown to develop and survive in the specific hypoxic environments. To understand the relationship between hypoxia and chemoresistance, we investigated the potential role of hypoxia in the pathophysiology of chemoresistance, especially focusing on hypoxia-inducible factor 1alpha (HIF-1alpha).
The A2780 ovarian cancer cells are cultured in gradient hypoxic conditions (5% O(2), 3% O(2), and 1% O(2)), the sensitivity of the cells to paclitaxel and the cell inhibitory rate were determined by MTT assay. The expression and the transcriptional activity of HIF-1alpha were examined by western blot, Immunocytochemical staining, reverse transcription-polymerase chain reaction (RT-PCR), and the dual luciferase reporter system, respectively. The cell cycle distribution was analyzed by flow cytometry. In addition, we silence HIF-1alpha expression by performing RNA interference.
MTT assay demonstrates that hypoxic challenge substantially reduces the susceptibility of cells to paclitaxel at all the tested concentrations. Coincident with this is the activation of HIF-1alpha in nuclear, which displays the increased transcriptional activity and high protein expression. Hypoxic manipulation (5% O(2), approximately 1% O(2)) significantly increased the cell population at G0/G1. Interestingly, knockdown of endogenous HIF-1alpha significantly alleviates the chemoresistance and promotes G1/S transition with the increased sensitivity of A2780 cells to paclitaxel under each hypoxic condition.
It suggests that HIF-1alpha, stimulated by hypoxia, exerts a pivotal role in chemoresistance by G0/G1 arrest. Eliminating hypoxic conditions or silencing HIF-1alpha by siRNA might provide a potent tool to enhance paclitaxel effectiveness in treatment of human ovarian cancer.
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- "It has also been reported that the expression of HIF-1α in most tumor tissues was related to tumor invasion, metastasis and prognosis . HIF-1α is involved in the hypoxia-induced resistance to paclitaxel . "
ABSTRACT: Objective To study the in vivo and in vitro effects of adding oxygen carbon nanotubes (CNTs) to chemotherapy for breast cancer. Methods MCF-7 and SK-BR-3 breast cancer cells were co-cultured with paclitaxel and then exposed to oxygen-CNTs under hypoxic conditions. Cell proliferation, viability, and apoptosis rate were analyzed. Hypoxia-inducible factor-1 alpha (HIF-1α) expression was measured using reverse transcription-polymerase chain reaction (RT-PCR) and western blot. Nude mice were used as a human breast cancer model to explore the impact of oxygen-CNTs on the in vivo chemotherapeutic effect of paclitaxel. Results Oxygen-CNTs had no significant effects on the growth of breast cancer cells under normoxia and hypoxia. However, in the hypoxic environment, oxygen-CNTs significantly enhanced the inhibitory effect of paclitaxel on cell proliferation, as well as the apoptosis rate. Under hypoxia, downregulation of HIF-1α and upregulation of caspase-3, caspase-8, caspase-9, LC3 and Beclin-1 were observed when paclitaxel was combined with oxygen-CNT. Furthermore, addition of oxygen-CNTs to chemotherapy was found to significantly reduce tumor weight in the tumor-bearing mice model. Conclusions Oxygen-CNTs can significantly increase the chemotherapeutic effect of paclitaxel on breast cancer cells. Oxygen-CNTs may be a potential chemosensitizer in breast cancer therapy.PLoS ONE 08/2014; 9(8):e104209. DOI:10.1371/journal.pone.0104209 · 3.23 Impact Factor
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- "In contrast to the constitutively expressed HIF-1β, HIF-1α stability and synthesis is strictly regulated by cellular oxygen levels and growth factors stimulation (O'Donnell et al., 2006). HIF-1α has been regarded as a key element to mediate the function of HIF-1 to activate a set of hypoxia-inducible genes, regulating tumor angiogenesis (Park et al., 2010), metastasis (Jing et al., 2012), resistance to therapy (Zhu et al., 2005; Huang et al., 2010) and other adaptations to hypoxia. Recently, several literatures have reported that overexpression of HIF-1α protein is significantly correlated with local recurrence, tumor progression and metastasis in human laryngeal carcinoma (Schrijvers et al., 2008; Wu et al., 2010), suggesting that HIF-1α might serve as a determinant of malignant biological behaviors 4854 of laryngeal cancer cells. "
ABSTRACT: Objectives: To investigate whether hypoxia has an effect on regulation of multidrug resistance (MDR) to chemotherapeutic drugs in laryngeal carcinoma cells and explore the role of hypoxia-inducible factor-1α (HIF- 1α). Methods: Laryngeal cancer cells were cultured under normoxic and hypoxic conditions. The sensitivity of the cells to multiple drugs and levels of apoptosis induced by paclitaxel were determined by MTT assay and annexin-V/propidium iodide staining analysis, respectively. HIF-1α expression was blocked by RNA interference. The expression of HIF-1α gene was detected by real-time quantitative RT-PCR and Western blotting. The value of fluorescence intensity of intracellular adriamycin accumulation and retention in cells was evaluated by flow cytometry. Results: The sensitivity to multiple chemotherapy agents and induction of apoptosis by paclitaxel could be reduced by hypoxia (P<0.05). A the same time, the adriamycin releasing index of cells was increased (P<0.05). However, resistance acquisition subject to hypoxia in vitro was suppressed by down-regulating HIF-1α expression. Conclusion: HIF-1α could be considered as a key regulator for mediating hypoxia-induced MDR in laryngeal cancer cells via inhibition of drug-induced apoptosis and decrease in intracellular drug accumulation.Asian Pacific journal of cancer prevention: APJCP 08/2013; 14(8):4853-4858. DOI:10.7314/APJCP.2013.14.8.4853 · 2.51 Impact Factor
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- "That platinum resistance is related to cellular P-glycoprotein level but not the hypoxic status  may explain why we saw no difference in cell survival between the compacted KLK4-expressing and scattered control SKOV-3 MCAs on platinum treatment. However, the paclitaxel resistance seen in compact KLK4-MCAs may be associated with hypoxia in the inner cell mass of MCAs . Blocking certain peptidases using a small molecule inhibitor may be a potential adjunct therapeutic strategy as we saw that the addition of a KLK4 inhibitory antibody or selective KLK4 active site inhibitor (SFTI-FCQR)  increased paclitaxel sensitivity of MCAs formed by KLK4 expressing cells. "
ABSTRACT: High tumor kallikrein-related-peptidase 4 (KLK4) levels are associated with a poor outcome for women with serous epithelial ovarian cancer (EOC), for which peritoneal dissemination and chemoresistance are key events. To determine the role of KLK4 in these events, we examined KLK4-transfected SKOV-3 and endogenous KLK4 expressing OVCA432 cells in 3-dimensional (3D) suspension culture to mimic the ascites microenvironment. KLK4-SKOV-3 cells formed multicellular aggregates (MCAs) as seen in ascites, as did SKOV-3 cells treated with active KLK4. MCA formation was reduced by treatment with a KLK4 blocking antibody or the selective active site KLK4 sunflower trypsin inhibitor (SFTI-FCQR). KLK4-MCAs formed larger cancer cell foci in mesothelial cell monolayers than those formed by vector and native SKOV-3 cells, suggesting KLK4-MCAs are highly invasive in the peritoneal microenvironment. A high level of KLK4 is expressed by ascitic EOC cells compared to matched primary tumor cells, further supporting its role in the ascitic microenvironment. Interestingly, KLK4 transfected SKOV-3 cells expressed high levels of the KLK4 substrate, urokinase plasminogen activator (uPA), particularly in 3D-suspension, and high levels of both KLK4 and uPA were observed in patient cells taken from ascites. Importantly, the KLK4-MCAs were paclitaxel resistant which was reversed by SFTI-FCQR and to a lesser degree by the general serine protease inhibitor, Aprotinin, suggesting that in addition to uPA, other as yet unidentified substrates of KLK4 must be involved. Nonetheless, these data suggest that KLK4 inhibition, in conjunction with paclitaxel, may improve the outcome for women with serous epithelial ovarian cancer and high KLK4 levels in their tumors.PLoS ONE 02/2013; 8(2):e57056. DOI:10.1371/journal.pone.0057056 · 3.23 Impact Factor