Fig 2: AKT inhibition is synthetic lethal with the homologous recombination (HR) deficiency induced by BRCA1 knockdown. a Experimental layout and detailed protocol used to assess synthetic lethality (SL) induction using a co-culture method of HR+ and HR– isogenic HCT116p21-/- cell lines, generated by lentiviral transduction of shRNAs against BRCA1. Each cell line co-expresses a different fluorescent protein: shSCR (CFP) and shBRCA1 (iRFP). Equal numbers of both isogenic cells were then plated in triplicates in 96 MW plates and combinations of increasing UV doses with AKT inhibitors were performed. Six days post-treatment, the co-cultured population was counted and categorized by the differential expression of fluorescent proteins using automated flow cytometry with an autosampler. The remaining % of each cell population was determined and the ratio of HR–/HR+ cells was calculated. The relative survival of each cell population in comparison with the untreated controls was determined to calculate SL induction by the different treatments. b Positive control to calibrate the robustness of the SL induction assay at 6 days using the PARP inhibitor Olaparib (0.1 µM), which is selectively toxic against the HR– population. c Determination of SL induction using HR+ (shSCR) and HR– (shBRCA1) isogenic HCT116p21-/- cells in a dose-response UV irradiation curve combined with three AKT inhibitors after 6 days of treatment: C11 (0.1 µM), MK-2206 (1 µM) and AZD5363 (1 µM). Statistical analysis shown in figures b and c was performed using analysis of variance (ANOVA) (*p = 0.05; **p = 0.01; ***p = 0.001). d Clonogenic experiments comparing HCT116p21-/- shSCR vs. shBRCA1 cells treated with the combination of AKT inhibition (C11 0.1 µM) and UV irradiation. Duplicates of each treatment are displayed. Seven hundred fifty cells were plated in a 96 MW format and after 6 days the survival fraction was stained with crystal violet. e Control WBs confirming the efficient impairment of PCNA ubiquitylation after UV triggered by AKT inhibition for every cell line used to validate the induction of SL. In the case of mouse and hamster cells (MEF and V-C8), the detection of PCNA ubiquitylation was performed using the total PCNA antibody (PC-10) because the Ubiquityl-PCNA antibody (D5C7P) only reacts with human samples. f Determination of SL induction using HR+ and HR– cells (BRCA1 or BRCA2 deficient) at the optimal UV irradiation dose in combination with the AKT inhibitor C11 (1 µM). A pair of triple-negative breast cancer cell lines (MDA-MB 231-BRCA1wt vs MDA-MB 436-BRCA1KO), a set of wt mouse embryonic fibroblast (MEF) (shSCR vs shBRCA1), a hamster BRCA2 KO cell line with its reconstituted counterpart (V-C8 vs VC#13) and a pair of HCT116p21-/- cells (shSCR vs shBRCA2) were used. Statistical analysis shown in panels b, c, and f was performed using analysis of variance (ANOVA) (*p = 0.05; **p = 0.01; ***p = 0.001)

Fig 3: Specific inhibitors of Erk1/2 and Akt diminished the promotion of angiogenesis by FMNT in HUVECs. HUVECs are exposed to the FMNT (20 µM) for 24 h or pretreated with L-NAME (100 µM), PD98059 (10 µM) and LY294002 (20 µM) for 1 h before incubation with FMNT (20 µM) for 24 h. (A) Cell growth was assessed by using a CCK8 assay. (B) The ability of cell proliferation was detected by using an EdU kit. (C) The migration of HUVECs was examined using wound-healing (C) and transwell migration (D) assays, respectively. (E) The tube formation of HUVECs was assessed by using a matrigel assay. The data represent the mean ± SD (n = 3). * p < 0.05, **p < 0.01, and ***p < 0.001 compared with the control group. # p < 0.05, ## p < 0.01, and ### p < 0.001 compared with the FMNT (20 µM) group.

Fig 4: Specific inhibitors of Erk1/2 and Akt diminished FMNT-induced eNOS phosphorylation and NO production in HUVECs. Erk1/2 (A,B) and Akt (C,D) phosphorylation was detected with Western blot analysis and immunofluorescence assay in HUVECs exposed to FMNT (20 µM) for 24 h with and without pretreatment of PD98059 (10 µM) or LY294002 (20 µM) for 1 h eNOS phosphorylation was detected with Western blot analysis in HUVECs exposed to FMNT (20 µM) for 24 h with and without pretreatment of PD98059 (10 µM) (E) and LY294002 (20 µM) (F) for 1 h. Intracellular NO levels in HUVECs with the same treatments were detected using a NO indicator DAF-FM diacetate that was measured with a flow cytometer (G) and a confocal fluorescence microscope (H). The protein expression and fluorescence value were expressed as the percentage of control. The data were presented as mean ± SD (n = 3). **p < 0.01, and ***p < 0.001 compared with the control group. ## p < 0.01, and ### p < 0.001 compared with the FMNT (20 µM) group.

Fig 5: siErk1/2 and siAkt attenuated FMNT-induced eNOS phosphorylation and NO production in HUVECs. The expression of Erk1/2 and Akt was silenced in HUVECs with transfection with specific siRNA for Erk1/2 (siErk1/2) and for Akt (siAkt), respectively. Protein levels of Erk1/2 and Akt was detected with Western blot analysis and immunofluorescence assay, respectively (A–D). (E) eNOS phosphorylation was detected with Western blot analysis in HUVECs with siErk1/2 or siAkt transfection. Intracellular NO levels in HUVECs with the same treatments were detected using a NO indicator DAF-FM diacetate with a flow cytometer (F) and a confocal fluorescence microscope (G), respectively. The protein expression and fluorescence value were expressed as the percentage of control. The data were presented as mean ± SD (n = 3). **p < 0.01, and ***p < 0.001 compared with the control group. ## p < 0.01, and ### p < 0.001 compared with the FMNT (20 µM) group.