Fig 2: CSE knockdown decreases the expression of VEGF and its downstream pathway in MDA-MB-231 cells. (A) Confirmation of the knockdown of CSE by CSE siRNA and (B) quantification showing the effect of CSE knockdown on the expression of VEGF. (C) Blot and (D) graph showing the effect of CSE knockdown on the PI3K pathway. (E) Blot and (F) graph showing the effect of CSE knockdown on the FAK/paxillin pathway. (G) Blot and (H) graph showing effect of CSE knockdown on the Ras/Raf/ERK1/2 pathway. *P<0.05 vs. Sc siRNA group. CSE, cystathionine-?-lyase; Sc, scrambled; siRNA, small interfering RNA; VEGF, vascular endothelial growth factor; PI3K, phosphatidylinositol 3-kinase/protein kinase B; Akt, protein kinase B; pAkt, phosphorylated Akt; FAK, focal adhesion kinase; Ras, rat sarcoma protein; Raf, rapidly accelerated fibrosarcoma; ERK, extracellular signal-regulated protein kinase; pERK, phosphorylated ERK.

Fig 3: Schematic diagram of the molecular mechanism underlying the promoting roles of the expression of CSE on the progression of breast cancer. CSE, cystathionine-?-lyase; VEGF, vascular endothelial growth factor; PI3K, phosphatidylinositol 3-kinase; Akt, protein kinase B; FAK, focal adhesion kinase; Ras, rat sarcoma; Raf, rapidly accelerated fibrosarcoma; ERK, extracellular signal-regulated protein kinase.

Fig 4: CTH-H2S contributes to the 5-FU resistance maintained by xCT overexpression. (A) immunoblots showing inhibiting the expression of xCT or CTH using specific siRNAs. (B) Interfering xCT or CTH expression inhibited clonogenicity of both colon cancer cell lines in the presence of 5-FU. (C) IC50 values of 5-FU after inhibiting xCT and CTH expression in both cell lines. (D) GSH values after inhibiting xCT and CTH expression in both cell lines. (E) H2S fluorescent probe indicating decreased H2S levels in both cell lines after inhibiting xCT or CTH. (F) GYY4137 saved the attenuated clonogenicity in both cell lines after inhibiting xCT. (G) and (H) GYY4137 saved the decreased IC50 of 5-FU and GSH values after inhibiting xCT in both cell lines. (I) GYY4137 promoted the attenuated levels of xCT after inhibiting CTH expression with siRNAs. (J) Quantitative real-time PCR showing no effect of either inhibiting CTH or GYY4137 on xCT mRNA levels. (* P < 0.05 vs negative control [NC], #P < 0.05 vs xCT siRNA groups)

Fig 5: Novel CSE inhibitor I157172 inhibits the proliferation, migration and invasion of MDA-MB-231 cells. (A) Schematic diagram of I157172. (B) A methylene blue assay was used to examine the effect of I157172 on H2S production in MDA-MB-231 cells. I157172 significantly inhibited the production of H2S. *P<0.05 vs. 0 µM I157172 group. (C) Effects of different concentrations of I157172 on the protein expression of CSE. (D) Quantification of CSE protein. *P<0.05 vs. 0 µM I157172 group; ?P<0.05 vs. 10 µM I157172 group; #P<0.05 vs. 20 µM I157172 group. (E) Effects of different concentrations of I157172 on cell growth. *P<0.05 vs. 0 µM I157172 group; ?P<0.05 vs. 5 µM I157172 group; #P<0.05 vs. 10 µM I157172 group; ?P<0.05 vs. 20 µM I157172 group. (F) Effects of different concentrations of I157172 on cell proliferation (image magnification, x200). (G) Images (magnification, x200) and (H) quantification of the effects of different concentrations of I157172 on cell migration. *P<0.05 vs. 0 µM I157172 group; ?P<0.05 vs. 10 µM I157172 group; #P<0.05 vs. 20 µM I157172 group. (I) Images (magnification, x200) and (J) quantification of the effects of different concentrations of I157172 on cell invasion. *P<0.05 vs. 0 µM I157172 group; ?P<0.05 vs. 10 µM I157172 group; #P<0.05 vs. 20 µM I157172 group. CSE, cystathionine-?-lyase; EdU, 5-ethynyl-2'-deoxyuridine.