Theranostics 2020; 10(6):2727-2743. doi:10.7150/thno.38729

Research Paper

Targeting microtubules sensitizes drug resistant lung cancer cells to lysosomal pathway inhibitors

Tan-Min Chin1,2,3*✉, Gandhi T. K. Boopathy1,4*✉, Ellen P.S. Man1, John G. Clohessy5, Eva Csizmadia5, Margaret P Quinlan6, Thomas Putti2, Seow-Ching Wan1, Chen Xie1, Azhar Ali1, Fhu Chee Wai1, Yan Shan Ong4, Boon-Cher Goh1,2, Jeff Settleman6,8, Wanjin Hong4, Elena Levantini5,7#, Daniel G. Tenen1,5#✉

1. Cancer Science Institute, National University of Singapore, 14 Medical Drive, Singapore 117599.
2. National University Health System, 5 Lower Kent Ridge Road, Singapore 119074.
3. Parkway Cancer Centre, Gleneagles Hospital. 6A Napier Road, Singapore 258500.
4. Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Proteos, Singapore 138673.
5. Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02115.
6. Massachusetts General Hospital Cancer Center, 149 13th Street, Charlestown, MA 02129.
7. Institute of Biomedical Technologies, National Research Council (CNR), Pisa, Italy.
8. Current address for Jeff Settleman: Pfizer, Inc. 10646 Science Center Drive, San Diego, CA 92121
* These authors contributed equally
# These authors contributed equally

This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/). See http://ivyspring.com/terms for full terms and conditions.
Citation:
Chin TM, Boopathy GTK, Man EPS, Clohessy JG, Csizmadia E, Quinlan MP, Putti T, Wan SC, Xie C, Ali A, Wai FC, Ong YS, Goh BC, Settleman J, Hong W, Levantini E, Tenen DG. Targeting microtubules sensitizes drug resistant lung cancer cells to lysosomal pathway inhibitors. Theranostics 2020; 10(6):2727-2743. doi:10.7150/thno.38729. Available from http://www.thno.org/v10p2727.htm

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Abstract

Oncogene-addicted cancers are predominantly driven by specific oncogenic pathways and display initial exquisite sensitivity to designer therapies, but eventually become refractory to treatments. Clear understanding of lung tumorigenic mechanisms is essential for improved therapies.

Methods: Lysosomes were analyzed in EGFR-WT and mutant cells and corresponding patient samples using immunofluorescence or immunohistochemistry and immunoblotting. Microtubule organization and dynamics were studied using immunofluorescence analyses. Also, we have validated our findings in a transgenic mouse model that contain EGFR-TKI resistant mutations.

Results: We herein describe a novel mechanism that a mutated kinase disrupts the microtubule organization and results in a defective endosomal/lysosomal pathway. This prevents the efficient degradation of phosphorylated proteins that become trapped within the endosomes and continue to signal, therefore amplifying downstream proliferative and survival pathways. Phenotypically, a distinctive subcellular appearance of LAMP1 secondary to microtubule dysfunction in cells expressing EGFR kinase mutants is seen, and this may have potential diagnostic applications for the detection of such mutants. We demonstrate that lysosomal-inhibitors re-sensitize resistant cells to EGFR tyrosine-kinase inhibitors (TKIs). Identifying the endosome-lysosome pathway and microtubule dysfunction as a mechanism of resistance allows to pharmacologically intervene on this pathway.

Conclusions: We find that the combination of microtubule stabilizing agent and lysosome inhibitor could reduce the tumor progression in EGFR TKI resistant mouse models of lung cancer.

Keywords: NSCLC, EGFR mutants, tyrosine kinase inhibitors, chloroquine, microtubule dysfunction