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How does paclitaxel kill cells and why do some cells evade it?


   School of Biosciences


About the Project

Paclitaxel (Taxol) is a microtubule-stabilizing drug widely used for the treatment of breast, ovarian and lung cancers. For many years, it was thought to kill cancer cells by inducing mitotic arrest, thus preventing proliferation. Recently it became apparent that clinically relevant concentrations of paclitaxel are insufficient for mitotic arrest and instead cause chromosomal instability due to multipolar cell divisions. Correct bipolar divisions need cells to round up before mitosis, which requires disassembly of interphase microtubules.

While paclitaxel is highly efficient in some patients, many eventually develop resistance. Cells round due to changes in the cortical actin cytoskeleton, which is induced by interphase microtubule disassembly. Since paclitaxel stabilises microtubules, it is likely to interfere with microtubule disassembly and therefore cell rounding. Thus, actin regulators are likely candidates for paclitaxel resistance. Additionally, paclitaxel resistance correlates with post-translational modifications of microtubules, such as acetylation and tyrosination, but it is unclear how these modifications contribute to the resistance.

Objectives:

1. Characterise effects of paclitaxel on microtubule disassembly, mitotic rounding and cell proliferation in vivo (Year 1).

2. Identify actin regulators which suppress paclitaxel effects (Year 2-3).

3. Determine how microtubule posttranslational modifications alter the effects of paclitaxel (Year 2-3).

4. Examine effects of identified actin regulators and microtubule modifications on paclitaxel-treated breast cancer cells in vitro (Year 3-3.5).

Experimental approach:

1. Wing imaginal discs of Drosophila larvae fed with paclitaxel will be analysed using immunohistochemistry to quantitate effects on proliferation, apoptosis and chromosome segregation.

2. Wing imaginal discs expressing GFP-tagged tubulin or E-cadherin will be analysed using live imaging in presence of paclitaxel to measure effects on microtubule disassembly and cell rounding.

3. For the objectives 2 and 3, larvae overexpressing interfering RNA or full-length variants of actin regulators (e.g. Pebble, RhoGEF2) and microtubule modifying enzymes (e.g. Atat, TTLL1A) will be generated using the UAS-GAL4 system.

4. MCF7 cells transfected with siRNAs against identified regulators will be cultured with paclitaxel to measure changes in cell rounding and chromosome segregation.

Novelty and timeliness:

Effects of cell rounding and paclitaxel on chromosomal segregation only recently came into light. The student will test the hypothesis that paclitaxel inhibits microtubule disassembly and cell rounding, leading to chromosome mis-segregation and ultimately cell death in vivo. Understanding how paclitaxel acts on the cellular level and how actin regulators and microtubule modifications modulate its effects will clarify why some patients develop resistance and reveal new routes for combating paclitaxel resistance.

Science Graduate School

As a PhD student in one of the science departments at the University of Sheffield, you’ll be part of the Science Graduate School. You’ll get access to training opportunities designed to support your career development by helping you gain professional skills that are essential in all areas of science. You’ll be able to learn how to recognise good research and research behaviour, improve your communication abilities and experience the breadth of technologies that are used in academia, industry and many related careers. Visit http://www.sheffield.ac.uk/sgs to learn more.


Funding Notes

This position is for self funded or externally funded students only.

First class or upper second 2(i) in a relevant subject. To formally apply for a PhD, you must complete the University's application form using the following link: View Website

All applicants should ensure that both references are uploaded onto their application as a decision will be unable to be made without this information.

References

Taubenberger AV, Baum B, Matthews HK. The Mechanics of Mitotic Cell Rounding. Front Cell Dev Biol. 2020 Aug 6;8:687. doi: 10.3389/fcell.2020.00687. PMID: 32850812; PMCID: PMC7423972.
Płochocka AZ, Ramirez Moreno M, Davie AM, Bulgakova NA, Chumakova L. Robustness of the microtubule network self-organization in epithelia. Elife. 2021 Feb 1;10:e59529. doi: 10.7554/eLife.59529. PMID: 33522481; PMCID: PMC7920549.
Weaver BA. How Taxol/paclitaxel kills cancer cells. Mol Biol Cell. 2014 Sep 15;25(18):2677-81. doi: 10.1091/mbc.E14-04-0916. PMID: 25213191; PMCID: PMC4161504.
Leguay, K., et al. Interphase microtubule disassembly is a signaling cue that drives cell rounding at mitotic entry. 2021. bioRxiv: 2021.2006.2014.448335.

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