p66ShcA potentiates the cytotoxic response of triple-negative breast cancers to PARP inhibitors
Eduardo Cepeda Cañedo, Stephanie Totten, Ryuhjin Ahn, Paul Savage, Deanna MacNeil, Jesse Hudson, Chantal Autexier, Genevieve Deblois, Morag Park, Michael Witcher, Josie Ursini-Siegel
Eduardo Cepeda Cañedo, Stephanie Totten, Ryuhjin Ahn, Paul Savage, Deanna MacNeil, Jesse Hudson, Chantal Autexier, Genevieve Deblois, Morag Park, Michael Witcher, Josie Ursini-Siegel
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Research Article Cell biology Oncology

p66ShcA potentiates the cytotoxic response of triple-negative breast cancers to PARP inhibitors

Abstract

Triple-negative breast cancers (TNBCs) lack effective targeted therapies, and cytotoxic chemotherapies remain the standard of care for this subtype. Owing to their increased genomic instability, poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) are being tested against TNBCs. In particular, clinical trials are now interrogating the efficacy of PARPi combined with chemotherapies. Intriguingly, while response rates are low, cohort of patients do respond to PARPi in combination with chemotherapies. Moreover, recent studies suggest that an increase in levels of ROS may sensitize cells to PARPi. This represents a therapeutic opportunity, as several chemotherapies, including doxorubicin, function in part by producing ROS. We previously demonstrated that the p66ShcA adaptor protein is variably expressed in TNBCs. We now show that, in response to therapy-induced stress, p66ShcA stimulated ROS production, which, in turn, potentiated the synergy of PARPi in combination with doxorubicin in TNBCs. This p66ShcA-induced sensitivity relied on the accumulation of oxidative damage in TNBCs, rather than genomic instability, to potentiate cell death. These findings suggest that increasing the expression of p66ShcA protein levels in TNBCs represents a rational approach to bolster the synergy between PARPi and doxorubicin.

Authors

Eduardo Cepeda Cañedo, Stephanie Totten, Ryuhjin Ahn, Paul Savage, Deanna MacNeil, Jesse Hudson, Chantal Autexier, Genevieve Deblois, Morag Park, Michael Witcher, Josie Ursini-Siegel

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Figure 5

ROS scavengers reverse p66ShcA-induced sensitivity of TNBCs to doxorubicin/PARPi combination therapy.

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ROS scavengers reverse p66ShcA-induced sensitivity of TNBCs to doxorubic...
VC- and p66ShcA-expressing Hs578T and MDA-MB-231 cells were treated with doxorubicin (1 nM) and PARPi (300 nM) alone or in combination, in presence or absence of (A) MitoTEMPO (10 μM) or (B) NAC (5 mM). Cell viability was determined by trypan blue exclusion. Data are shown as the mean of mean fold change of the number of viable cells relative to DMSO (mean ± SEM) (n = 3–4 independent experiments). (C) Oxidative stress marker 8-oxodG was analyzed by IHC staining in VC- and p66ShcA-expressing Hs578T tumors. Data are depicted as average percentage of 8-oxodG–positive pixels ± SEM (n = 10–12 tumors per group). Representative images of the IHC staining illustrating 8-oxodG positivity are shown (scale bars: 100 μm). *P < 0.05; **P < 0.01; ***P < 0.001 by 2-way ANOVA/Tukey’s multiple comparisons test (A and B) and 1-way ANOVA/Tukey’s multiple comparisons test (C).