To this end we incubated tumorsphere-derived cells from the MCF-7 and HCC1954 breast tumor cell lines in chemically defined, serum-free media containing serial dilutions of each of 3 different selective MAO-A inhibitors: clorgyline, pirlindole and tetrindole, and 4 days thereafter quantified the number of tumorspheres that arose at each compound concentration. Here, MAOA is linked to breast neoplasm.