CBS and breast cancer: These data indicate that H2S may play a slight role as a cytoprotective agent in breast cancer cells, but this effect is fairly minor, and is only detectable for 3-MST-derived H2S or polysulfides, but not for CBS/CSE-derived H2S. AOAA or HMPSNE, on its own, at the concentrations used, did not have any marked effects of cell viability in non-oxidatively stressed cells (Figure 8 and Figure 9).