Dynamin impacts homology-directed repair and breast cancer response to chemotherapy
Sophia B. Chernikova, … , Balázs Győrffy, J. Martin Brown
Sophia B. Chernikova, … , Balázs Győrffy, J. Martin Brown
Published October 29, 2018
Citation Information: J Clin Invest. 2018;128(12):5307-5321. https://doi.org/10.1172/JCI87191.
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Dynamin impacts homology-directed repair and breast cancer response to chemotherapy

Abstract

After the initial responsiveness of triple-negative breast cancers (TNBCs) to chemotherapy, they often recur as chemotherapy-resistant tumors, and this has been associated with upregulated homology-directed repair (HDR). Thus, inhibitors of HDR could be a useful adjunct to chemotherapy treatment of these cancers. We performed a high-throughput chemical screen for inhibitors of HDR from which we obtained a number of hits that disrupted microtubule dynamics. We postulated that high levels of the target molecules of our screen in tumors would correlate with poor chemotherapy response. We found that inhibition or knockdown of dynamin 2 (DNM2), known for its role in endocytic cell trafficking and microtubule dynamics, impaired HDR and improved response to chemotherapy of cells and of tumors in mice. In a retrospective analysis, levels of DNM2 at the time of treatment strongly predicted chemotherapy outcome for estrogen receptor–negative and especially for TNBC patients. We propose that DNM2-associated DNA repair enzyme trafficking is important for HDR efficiency and is a powerful predictor of sensitivity to breast cancer chemotherapy and an important target for therapy.

Authors

Sophia B. Chernikova, Rochelle B. Nguyen, Jessica T. Truong, Stephano S. Mello, Jason H. Stafford, Michael P. Hay, Andrew Olson, David E. Solow-Cordero, Douglas J. Wood, Solomon Henry, Rie von Eyben, Lei Deng, Melanie Hayden Gephart, Asaithamby Aroumougame, Claudia Wiese, John C. Game, Balázs Győrffy, J. Martin Brown

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Figure 2

High-throughput chemical screen identifies tubulin binders as inhibitors of HDR.

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High-throughput chemical screen identifies tubulin binders as inhibitors...
(A) A pie chart of the prescreen using the libraries of known compounds shows that 21% of compounds potentiating the chlorambucil effect classify as disruptors of cell trafficking. (B) Fraction of cells undergoing gene conversion after DSBs induced by I-SceI (GFP-positive cells) versus fraction of surviving cells. The plot identifies compounds that are able to inhibit gene conversion without affecting cell viability. The yellow line and the area above it show compounds (light gray symbols) for which inhibition of gene conversion (low fraction of GFP-positive cells) could have resulted from increased cell death associated with compound toxicity. True inhibitors of gene conversion are clustering in the left lower quadrant (below the yellow line), where compounds inhibit gene conversion at concentrations not affecting cell viability. (C) CB2, CB4, and CD3 (see Supplemental Figure 2B) inhibit tubulin polymerization similarly to vinblastine. The results for taxol are shown for comparison purposes. Taxol, vinblastine, CB2, CB4, and CD3 were used at 10 μM. (D) CB2, CB4, CB6, and CB13 inhibit radiation-induced Rad51 formation in CHO AA8 cells. CB2 and CB6 were used at 100, 200, and 400 nM each. CB4 and CB13 were used at 200, 400, and 800 nM each. 17-AAG (control) was used at 100, 200, and 400 nM. Shown are means ± SDs from n > 2 experiments. Significance analysis: ANOVA. **P < 0.01, ****P < 0.0001.