Identification of Polo-like Kinase 1 as a Potential Therapeutic Target in Anaplastic Thyroid Carcinoma

Loading drugs into carriers such as liposomes can increase the therapeutic ratio by reducing drug concentrations in normal tissues and raising their concentrations in tumors. Although this strategy has proven advantageous in certain circumstances, many drugs are highly hydrophobic and nonionizable and cannot be loaded into liposomes through conventional means. We hypothesized that such drugs could be actively loaded into liposomes by encapsulating them into specially designed cyclodextrins. To test this hypothesis, two hydrophobic drugs that had failed phase II clinical trials because of excess toxicity at deliverable doses were evaluated. In both cases, the drugs could be remotely loaded into liposomes after their encapsulation (preloading) into cyclodextrins and administered to mice at higher doses and with greater efficacy than possible with the free drugs.T here is currently wide interest in the development of nanoparticles for drug delivery (1-7). This area of research is particularly relevant to cancer drugs, wherein the therapeutic ratio (dose required for effectiveness to dose causing toxicity) is often low. Nanoparticles carrying drugs can increase this therapeutic ratio over that achieved with the free drug through several mechanisms. In particular, drugs delivered by nanoparticles are thought to selectively enhance the concentration of the drugs in tumors as a result of the enhanced permeability and retention (EPR) effect (8-18). The enhanced permeability results from a leaky tumor vascular system, whereas the enhanced retention results from the disorganized lymphatic system that is characteristic of malignant tumors.Much current work in this field is devoted to designing novel materials for nanoparticle generation. This new generation of nanoparticles can carry drugs-particularly those that are insoluble in aqueous medium-that are difficult to incorporate into conventional nanoparticles such as liposomes. However, the older generation of nanoparticles has a major practical advantage in that they have been extensively tested in humans and approved by regulatory agencies such as the Food and Drug Administration in the United States and the European Medicines Agency in Europe. Unfortunately, many drugs cannot be easily or effectively loaded into liposomes, thereby compromising their general use.In general, liposomal drug loading is achieved by either passive or active methods (9,(19)(20)(21)(22). Passive loading involves dissolution of dried lipid films in aqueous solutions containing the drug of interest. This approach can only be used for water-soluble drugs, and the efficiency of loading is often low. In contrast, active loading can be extremely efficient, resulting in high intraliposomal concentrations and minimal wastage of precious chemotherapeutic agents (9,23,24). In active loading, drug internalization into preformed liposomes is typically driven by a transmembrane pH gradient. The pH outside the liposome allows some of the drug to exist in an unionized form, able to migrate across the lipid bi...

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“…4B). This efficacy was previously observed in other murine models (41,47,(56)(57)(58)(59), and provided the rationale for the clinical trials.…”

Section: Chemically Modified β-Cyclodextrins Can Encapsulate Small Hysupporting

confidence: 70%

Remote loading of preencapsulated drugs into stealth liposomes

Sur

Fries

Kinzler

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

122

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“…[29][30][31][32][33] In the present study, we demonstrate that PLK1 inhibition with BI 2536 causes mitotic arrest in GBM cell lines, and that pretreatment with this drug efficiently sensitizes cells to radiation by decreasing proliferation and self-renewal in all the cell lines tested. Decreased proliferation after treatment with BI 2536 alone has already been demonstrated in different tumors: cervix adenocarcinoma, 24 leukemia, 34 anaplastic thyroid carcinoma, 35 melanomas, 15 and osteosarcoma cells. 25 Here, we also report that the combinatorial effect of BI 2536 with radiation was superior to treatment with the drug alone on cell proliferation, showing synergic effects.…”

Section: Pezuk Et Almentioning

confidence: 84%

Inhibition of Polo-Like Kinase 1 Induces Cell Cycle Arrest and Sensitizes Glioblastoma Cells to Ionizing Radiation

Pezuk

Brassesco

Morales

et al. 2013

Cancer Biotherapy and Radiopharmaceuticals

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Despite efforts to improve surgical, radiologic, and chemotherapeutic strategies, the outcome of patients with glioblastoma (GBM) is still poor. Polo-like kinase 1 (PLK1) is a serine/threonine kinase that plays key roles in cell cycle control and has been associated with tumor growth and prognosis. Here, we aimed at testing the radiosensitizing effects of the PLK1 inhibitor BI 2536 on eight GBM cell lines. For cell cycle analysis, T98G, U251, U343 MG-a, LN319, SF188, U138 MG, and U87 MG cell lines were treated with 10, 50, or 100 nM of BI 2536 for 24 hours. In addition, cell cultures exposed to BI 2536 50 nM for 24 hours were irradiated with c-rays from 60 Cobalt source at final doses of 2, 4, and 6 Gy. Combinatorial effects were evaluated through proliferation and clonogenic capacity assays. Treatment with BI 2536 caused mitotic arrest after 24 hours, and increased apoptosis in GBM cells. Moreover, our results demonstrate that pretreatment with this drug sensitized six out of seven GBM cell lines to different doses of c-irradiation as shown by decreased growth and abrogation of colony-formation capacity. Our data suggest that PLK1 blockage has a radiosensitizing effect on GBM, which could improve treatment strategies for this devastating tumor.

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“…Two independent RNAi studies both showed that the elimination of Plk1 function preferentially reduced the survival of cells with mutant p53 (25,26). There are also reports that anaplastic thyroid carcinoma (ATC), which has high frequency of p53 mutation (70-90%) and carries chromosomal instability signature, is profoundly sensitive to Plk1 inhibition by both siRNA knockdown study (44) and compound study (45). Interestingly, Aurora kinase inhibitor VX-680 was also shown to preferentially kill cancer cells with compromised p53 function, and a similar mechanism of weakened pseudo-G 1 tetraploidy checkpoint in p53-defective cells was proposed (46).…”

Section: Discussionmentioning

confidence: 99%

Sensitivity of Cancer Cells to Plk1 Inhibitor GSK461364A Is Associated with Loss of p53 Function and Chromosome Instability

Degenhardt

Greshock

Laquerre

et al. 2010

Molecular Cancer Therapeutics

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Polo-like kinases are a family of serine threonine kinases that are critical regulators of cell cycle progression and DNA damage response. Predictive biomarkers for the Plk1-selective inhibitor GSK461364A were identified by comparing the genomics and genetics of a panel of human cancer cell lines with their response to a drug washout followed by an outgrowth assay. In this assay, cell lines that have lost p53 expression or carry mutations in the TP53 gene tended to be more sensitive to GSK461364A. These more sensitive cell lines also had increased levels of chromosome instability, a characteristic associated with loss of p53 function. Further mechanistic studies showed that p53 wild-type (WT) and not mutant cells can activate a postmitotic tetraploidy checkpoint and arrest at pseudo-G 1 state after GSK461364A treatment. RNA silencing of WT p53 increased the antiproliferative activity of GSK461364A. Furthermore, silencing of p53 or p21/CDKN1A weakened the tetraploidy checkpoint in cells that survived mitotic arrest and mitotic slippage. As many cancer therapies tend to be more effective in p53 WT patients, the higher sensitivity of p53-deficient tumors toward GSK461364A could potentially offer an opportunity to treat tumors that are refractory to other chemotherapies as well as early line therapy for these genotypes. Mol Cancer Ther; 9(7); 2079-89. ©2010 AACR.

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Identification of Polo-like Kinase 1 as a Potential Therapeutic Target in Anaplastic Thyroid Carcinoma

Cited by 56 publications

References 38 publications

Remote loading of preencapsulated drugs into stealth liposomes

Remote loading of preencapsulated drugs into stealth liposomes

Inhibition of Polo-Like Kinase 1 Induces Cell Cycle Arrest and Sensitizes Glioblastoma Cells to Ionizing Radiation

Sensitivity of Cancer Cells to Plk1 Inhibitor GSK461364A Is Associated with Loss of p53 Function and Chromosome Instability

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