Displacement of Bax by BMF Mediates STARD13 3′UTR-Induced Breast Cancer Cells Apoptosis in an miRNA-Depedent Manner

The balance of pro- and antiapoptotic gene expression programs dominates the apoptotic progress of cancer cells. We previously demonstrated that STARD13 3′UTR suppressed breast cancer metastasis via inhibiting epithelial-mesenchymal transition (EMT). However, the roles of STARD13 3′UTR in breast cancer apoptosis remain elusive. Here, we identified that STARD13 3′UTR promoted cell apoptosis <i>in vitro</i> and <i>in vivo</i>. Mechanistically, STARD13 3′UTR acted as a ceRNA for BMF (Bcl-2 modifying factor), thus increasing BMF expression in an miRNA-dependent manner. Meanwhile, STARD13 3′UTR enhanced the interaction of BMF/Bcl-2 to release Bax (Bcl-2 associated X protein) in breast cancer cells. Finally, we verified the ceRNA relationship between STARD13 and BMF <i>in vivo</i>. Collectively, these findings suggest that STARD13 3′UTR could act as a ceRNA for BMF to promote apoptosis and recognize STARD13 3′UTR as a potential therapeutic target in breast cancer cells

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Figure S6. Target miRNAs attenuated the promotive effects of STARD13-correlated ceRNA network on Hippo signaling. Target miRNAs (miR-424, miR-374a, miR-590-3p, miR-448, and miR-15a) mimics mix was co-transfected with STARD13-correlated ceRNAs-3′UTR overexpression constructs or not, the protein level of LATS1/2 and downstream effectors (p-YAP/p-TAZ, YAP/TAZ, and CTGF) was examined. (TIF 1437 kb

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Figure S3. STARD13-correlated ceRNA network inhibits CSC traits of breast cancer cells in vivo. (A, B, and C) Images (left) and weight (right) of tumors harvested when serially diluted MDA-MB-231 cells with STARD13-correlated ceRNAs-3′UTR overexpression were planted. (D and E) Images (left) and weight (right) of tumors harvested when serially diluted MCF-7 cells with STARD13 or its ceRNA knockdown were planted. (TIF 4230 kb

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Figure S5. STARD13-correlated ceRNAs-3′UTRs regulate TAZ nuclear abundance. Confocal images of TAZ distribution in MDA-MB-231 cells with STARD13-correlated ceRNAs-3′UTR overexpression or not. Data were presented as the mean ± SD, n = 3, *p < 0.05, **p < 0.01 vs. Vector. (TIF 4364 kb

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Figure S1. The infection efficiency of lentivirus. (A) Lentiviral infection efficiency of MDA-MB-231 cells stably expressing STARD13-3′UTR, CDH5-3′UTR, HOXD1-3′UTR, and HOXD10-3′UTR was examined by qRT-PCR. (B) Lentiviral infection efficiency of MCF-7 cells stably depleted of STARD13, CDH5, HOXD1, and HOXD10 was verified by Western blot analysis. Data were presented as the mean ± SD, n = 3, ***p < 0.001 vs. Ctrl. (TIF 1373 kb

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Figure S9. STARD13-correlated ceRNA network regulates breast cancer EMT through LATS1/2. EMT marker (see in main text) expressions were measured in MDA-MB-231 cells with STARD13- or its ceRNAs-3′UTR overexpression plus LATS1 or LATS2 or LATS1/2 knockdown by lentiviral infection. (TIF 2846 kb

Additional file 4: of STARD13-correlated ceRNA network-directed inhibition on YAP/TAZ activity suppresses stemness of breast cancer via co-regulating Hippo and Rho-GTPase/F-actin signaling

Table S4. Sequences of primers used for plasmid constructions. (DOC 41 kb

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Table S5. The number of common miRNA binding sites on STARD13 3′UTR and LATS1/2 3′UTR is predicted using Targetscan 6.2 and microRNA.org . (DOC 33 kb

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Figure S11. Depletion of STARD13-correlated ceRNAs dampens the response of breast cancer cells to doxorubicin. (A) IC50 curves of MCF-7 cells with STARD13-correlated ceRNA knockdown and were fitted with a nonlinear regression model and were presented as log (Doxorubicin) vs cell viability. (B) Western blot assay of lysates from MCF-7 cells with STARD13-correlated ceRNA knockdown. (C) Images of tumors harvested when STARD13 3′UTR stable overexpression cells were planted and followed by doxorubicin treatment or not. The weight of tumors harvested in (C) was monitored. (D) The weight of mice depicted in (C) was monitored. (E) The volume of tumors harvested in (C) was monitored. (G) Confocal images of MCF-7 cells described in (B) with doxorubicin treatment. Depletion of STARD13-correlated ceRNAs impaired the cellular retention of doxorubicin. (F) Western blot assay of lysates from MCF-7 cells with STARD13-correlated ceRNA knockdown plus si-Dicer or not. (TIF 3999 kb

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Figure S8. Representative FACS profile of MDA-MB-231 cells with STARD13- or its ceRNAs-3′UTR overexpression plus LATS1 or LATS2 or LATS1/2 knockdown by lentiviral infection. (TIF 1568 kb