Background: Resistance of cancer cells to chemotherapeutic agents is a major cause of treatment failure in patients with cancer. The drug resistance of tumor cells can be significantly modified by specific features of tumor microenvironment, such as oxygen depletion (hypoxia), glucose/energy deprivation and acidosis. Methods: The effects of acidic tumor-like microenvironment on cytotoxicity of antabuse (disulfiram, DSF)/Cu²⁺ complexes to MCF-7 breast carcinoma and HT-29 colon carcinoma cells were studied. Results: We show that acidic pH significantly potentiates toxicity of DSF/Cu²⁺ complex to breast and colon cancer cells. This phenomenon is associated with changes in cell metabolism, altered Akt kinase and NFκB activity and increased reactive oxygen species production. Conclusion: Specific pH of tumor microenvironment enhances cytotoxicity of DSF/Cu²⁺ to breast and colon cancer cells.

Growth of tumor cells depends on sufficient supply of fermentable substrate, such as glucose. This provokes development of new anticancer therapies based on dietary restrictions. However, some tumor cells can lower their glucose dependency and activate processes of ATP formation/saving to retain viability even in limited glucose supply. In addition, tumor cells often lose sensitivity to many conventional anticancer drugs in the low-glucose conditions. Thus, development of the drugs effectively killing the tumor cells in nutrient-limited conditions is necessary. In this study, we show an enhanced cytotoxicity of tetrathiomolybdate, the drug exhibiting antiangiogenic and tumor-suppressing effects, to neuroblastoma SH-SY5Y and SK-N-BE(2) cells in the low-glucose conditions. This preference results from the tetrathiomolybdate-induced upregulation of cell dependency on glucose. The cells treated with tetrathiomolybdate increase the uptake of glucose, production of lactate, activate the Akt- and AMPK-signaling pathways and downregulate COX IV. In cells growing in the low-glucose conditions, these events result in significant decrease of the intracellular ATP supply and apoptosis. We propose tetrathiomolybdate as suitable agent to be used in combination with dietary restrictions in therapy of neuroblastoma.