Calcium oxalate crystals with a bipyramidal morphology and a high tendency to aggregate attach directly to breast cancer cells and affect their phenotype

However, much less is known about calcium oxalate dihydrate (COD) crystals, which are commonly associated with benign conditions. In general, calcium oxalates are pathological biominerals found in kidney stones and as microcalcifications (MCs) in breast and thyroid cancers.

In breast cancer MCs, COD crystals are exclusively associated with benign lesions, and we have recently shown that they suppress breast precancer progression in vitro. Here, we studied the influence of synthetic calcium oxalate crystals – both COD and calcium oxalate monohydrate (COM) – with different morphologies and properties on crystal-cell interactions. We found that the less negatively charged crystals exhibited a greater tendency to aggregate and, as aggregates, attached better to cells, particularly to the cells of an invasive breast cancer cell line.