Formaldehyde promotes and inhibits the proliferation of cultured tumour and endothelial cells.

Formaldehyde was applied in various doses (0.1-10.0 mM) to HT-29 human colon carcinoma and HUV-EC-C human endothelial cell cultures. Cell number, apoptotic and mitotic index as well as proportion of cells in S-phase was investigated by morphological methods and flow cytometry. Ten mM of formaldehyde caused high degree of cell damage and practically eradicated the cell cultures. One mM of formaldehyde enhanced apoptosis and reduced mitosis in both types of cell cultures, in a moderate manner. The low dose (0.1 mM) enhanced cell proliferation and decreased apoptotic activity of the cultured cells, the tumour cells appeared to be more sensitive. The possible role of this dose-dependent effect of formaldehyde in various pathological conditions, such as carcinogenesis and atherogenesis is discussed with emphasis on the eventual interaction between formaldehyde and hydrogen peroxide.