Fig. 4

Cell chemoresistance induced by light activation of optoNotch (oN) in triple-negative (MDA-MB-468) and estrogen-positive (MCF7) breast cancer cell lines. Cells treated with various concentrations of doxorubicin or paclitaxel were activated by 0.05 s pulses of blue light for 3 h per day. After 96 h of drug treatment, viability of MCF7 and MDA-MB-468 cells was analyzed. OptoNotch-expressing cells were either photo-stimulated or kept in the dark, then exposed to different concentrations of anti-neoplastic agents (a–c). Wild type (WT) MCF7 and MDA-MB-468 were tested in parallel under identical conditions (d–f). The mRNA expression level for HES1, HEY1 and NOTCH3 assessed by qPCR 2^−∆∆Ct method (normalization by GAPDH) in MCF7 and MDA-MB-468 cells after doxorubicin or paclitaxel treatment (g). The expression level of each gene was indicated as fold change compared to WT cells kept in the dark (Control D; indicated as 1). Control D—LOV2^V416L-Zdk1-N1ICD stably expressing cells kept in the dark; Control L—light-activated LOV2^V416L-Zdk1-N1ICD stably expressing cells; Paclitaxel\Doxorubicin D—LOV2^V416L-Zdk1-N1ICD stably expressing cells kept in the dark treated with Paclitaxel\Doxorubicin, respectively. Paclitaxel\Doxorubicin L—light-activated LOV2^V416L-Zdk1-N1ICD stable expressing cells treated with Paclitaxel\Doxorubicin, respectively. Data points represent each sample in triplicate and each graph is representative of three biological replicates. Statistical significance was analyzed by a one-way ANOVA test and Tukey’s multiple comparisons post-hoc test vs. not treated cells and it is presented as ***for p ≤ 0.001, **p ≤ 0.01; *p ≤ 0.05