Indium/Gallium Maltolate Effects on Human Breast Carcinoma Cells: In Vitro Investigation on Cytotoxicity and Synergism with Mitoxantrone

[Image: see text] In this study, we aimed to investigate in vitro whether the synthetized indium maltolate (InMal) and gallium maltolate (GaMal) could exert either a toxic effect toward breast cancer cell line MDA-MB-231 or an agonistic activity with mitoxantrone (MTX) in comparison to fibroblast cell line NIH-3T3. Both GaMal and InMal reduced viability of MDA-MB-231, and at a lesser extent of NIH3-T3, in a dose- and time-dependent mode, the outcome was more effective in comparison to MTX sole exposure. Both GaMal and InMal toxicity was reverted by iron citrate addition on NIH3-T3, not on MDA-MB-231, showing indirectly that gallium and indium’s mechanisms of action may include iron targeting. The agonistic activity against MDA-MB-231 survival was shown pretreating with 100 μM InMal for 24 h followed by medium exchange with MTX at 10 ng mL(–1) or vice-versa but not with co-incubation of both compounds. In particular, InMal pretreating resulted more protective to MTX subsequent exposure.