Hypoxia induced paclitaxel resistance in human ovarian cancers via hypoxia-inducible factor 1alpha.
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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ABSTRACT: Growing evidence indicates that perioperative factors, including choice of anesthetic, affect cancer recurrence after surgery although little is known about the effect of anesthetics on cancer cells themselves. Certain anesthetics are known to affect hypoxia cell signaling mechanisms in healthy cells by up-regulating hypoxia-inducible factors (HIFs). HIFs are also heavily implicated in tumorigenesis and high levels correlate with poor prognosis. Renal cell carcinoma (RCC4) cells were exposed to isoflurane for 2 h at various concentrations (0.5-2%). HIF-1α, HIF-2α, phospho-Akt, and vascular endothelial growth factor A levels were measured by immunoblotting at various time points (0-24 h). Cell migration was measured across various components of extracellular matrix, and immunocytochemistry was used to analyze proliferation rate and cytoskeletal changes. Isoflurane up-regulated levels of HIF-1α and HIF-2α and intensified expression of vascular endothelial growth factor A. Exposed cultures contained significantly more cells (1.81 ± 0.25 vs. 1.00 of control; P = 0.03) and actively proliferating cells (89.4 ± 2.80 vs. 64.74 ± 7.09% of control; P = 0.016) than controls. These effects were abrogated when cells were pretreated with the Akt inhibitor, LY294002. Exposed cells also exhibited greater migration on tissue culture-coated (F = 16.89; P = 0.0008), collagen-coated (F = 20.99; P = 0.0003), and fibronectin-coated wells (F = 8.21; P = 0.011) as along with dramatic cytoskeletal rearrangement, with changes to both filamentous actin and α-tubulin. These results provide evidence that a frequently used anesthetic can exert a protumorigenic effect on a human cancer cell line. This may represent an important contributory factor to high recurrence rates observed after surgery.Anesthesiology 09/2013; 119(3):593-605. DOI:10.1097/ALN.0b013e31829e47fd · 6.17 Impact Factor
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ABSTRACT: ObjectiveTo study the in vivo and in vitro effects of adding oxygen carbon nanotubes (CNTs) to chemotherapy for breast cancer.MethodsMCF-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.ResultsOxygen-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.ConclusionsOxygen-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 · 3.53 Impact Factor
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ABSTRACT: Microtubules, an important cytoskeletal protein involved in mitotic and non-mitotic functions of cells, are important targets in cancer therapy. Microtubule-stabilizing drugs like the taxanes are critical adjuvant and palliative first-line therapies for the treatment of early, advanced and metastatic solid tumors of different lineages. Their adverse on- and off-target effects and high susceptibility to multidrug resistance, however, are major challenges encountered in the clinic in the treatment of solid cancers. Although biochemical resistance to microtubule-stabilizing drugs has been well characterized, molecular mechanisms that contribute to clinical resistance to taxanes in solid tumors still remain poorly understood and uncontrolled. The heterogeneous tumor microenvironment leads to greater diversity of resistance mechanisms to taxanes. Tumor hypoxia, a prominent feature of solid tumors, results in a broad range of effects on a number of cellular pathways and is one of the major contributors to the development of resistance to not only microtubule-stabilizing drugs but also other anticancer drugs. In this review, we highlight the potential role of hypoxia in the development of resistance to taxanes through mechanisms that involve altering the cell cycle, changing the properties of microtubules, and inducing the overexpression of gene products that contribute to drug resistance. Hypoxia-induced challenges described in this review are not limited to microtubule-stabilizing drugs alone, but in many cases also impact on treatment with non-microtubule-targeting anticancer drugs. Copyright © 2015. Published by Elsevier B.V.Biochimica et Biophysica Acta (BBA) - Reviews on Cancer 02/2015; 1855(2). DOI:10.1016/j.bbcan.2015.02.001 · 7.58 Impact Factor