Formaldehyde-releasing prodrugs specifically affect cancer cells by depletion of intracellular glutathione and augmentation of reactive oxygen species.

Histone deacetylase inhibitory prodrugs that are metabolized to carboxylic acid(s) and aldehyde(s) possess antineoplastic properties. Formaldehyde-releasing prodrugs were shown to be the most potent. The objective of this study was to gain understanding on the mode of action of these prodrugs in cancer cells. HL-60 and MCF-7 cells in the presence of N-acetylcysteine or glutathione were protected from death induced by formaldehyde-releasing prodrugs but not from death caused by the homologous acetaldehyde-releasing ones. Cell death induced by the former was accompanied by depletion of intracellular glutathione and increased reactive oxygen species that were attenuated by N-acetylcysteine. At fourfold higher concentration, acetaldehyde-releasing prodrugs increased reactive oxygen species that were further augmented by N-acetylcysteine. In HL-60 cells, formaldehyde-releasing prodrugs dissipated the mitochondrial membrane potential and glutathione or N-acetylcysteine restored it. Although acetaldehyde-releasing prodrugs dissipated mitochondrial membrane potential, it occurred at 20-fold greater concentration and was unaffected by the antioxidants. Formaldehyde-releasing prodrugs abrogated c-myc protein expression and elevated c-Jun and H2AX phosphorylation, N-acetylcysteine partially reversed these changes. Herein, we show that formaldehyde-releasing prodrugs diminish the level of glutathione most likely by forming S-formylglutathione adducts resulting in increase of reactive oxygen species followed by signaling events that lead to cancer cells death.

Carbon nanotubes based electrochemical biosensor for detection of formaldehyde released from a cancer cell line treated with formaldehyde-releasing anticancer prodrugs.

This paper reports the development of an electrochemical biosensor for the detection of formaldehyde in aqueous solution, based on the coupling of the enzyme formaldehyde dehydrogenase and a carbon nanotubes (CNT)-modified screen-printed electrode (SPE). We monitored the amperometric response to formaldehyde released from U251 human glioblastoma cells situated in the biosensor chamber in response to treatment with various anticancer prodrugs of formaldehyde and butyric acid. The current response was higher for prodrugs that release two molecules of formaldehyde (AN-193) than for prodrugs that release only one molecule of formaldehyde (AN-1, AN-7). Homologous prodrugs that release one (AN-88) or two (AN-191) molecules of acetaldehyde, showed no signal. The sensor is rapid, sensitive, selective, inexpensive and disposable, as well as simple to manufacture and operate.

Novel multifunctional acyloxyalkyl ester prodrugs of 5-aminolevulinic acid display improved anticancer activity independent and dependent on photoactivation.

Multifunctional acyloxyalkyl ester prodrugs of 5-aminolevulinic acid in cancer cell lines inhibited the proteasome and induced apoptosis and heme synthesis. The most potent prodrug was butyryloxymethyl 5-amino-4-oxopentanoate (1a). The metabolically released formaldehyde from the prodrugs was the dominant factor affecting cell viability by a ROS-dependent mechanism and was responsible for rapid phosphorylation of H2AX, suppression of the cell survival protein c-myc, and transient elevation in the expression of p21. 1a, which differs from 2a by releasing butyric instead of pivalic acid, was a more potent inducer of heme and acetylated H4 expression and induced apoptosis through activation of caspase 9. 1a and 1b specifically increased the level of the photosensitizer protoporphyrin 9, leading to enhancement of cell death by photodynamic therapy (PDT). The advantage of these multifunctional prodrugs over 5-ALA is their greater potency in the non-PDT mechanism of cancer cell killing and their ability to also augment PDT.