Antimicrobial Agents and Chemotherapy

Biography

Biography: Maamoun Fatfat

Abstract

The maintenance of optimal metal levels is an essential aspect of cell homoeostasis. In many types of cancers, the levels of metals such as iron, zinc and copper diverge from the norm. This disturbance of intracellular metal levels has been the basis of several cancer treatments. TPEN (Tetrakis-(2-Pyridylmethyl) ethylenediamine) is one such drug that exploits disturbances of intracellular metal levels to exert its anticancer effects. Previously, we have shown that the zinc chelator TPEN is involved in copper chelation inside the cell which selectively kills colon cancer cells (HCT116). We have additionally shown that this anticancer effect is mediated by TPEN’s involvement in redox cycling, which increases the generation of reactive oxygen species. In this study we aimed to decipher the mechanisms of TPEN antitumor activity through studying its effects on DNA damage. We show that TPEN causes ROS generation and the death of HCT116 cells at concentrations as low as 5 µM. Pre-treatment of cells with the copper chelator Neocuproine and with CuSO4, restored cell viability and reduced ROS generation, suggesting the requirement of cellular copper for TPEN toxicity. In a spectrophotometric analysis, we found that TPEN binds to calf thymus DNA through an intercalative mode and this binding was enhanced as the ratio of TPEN to DNA was increased. Using the comet assay, TPEN was found to induce significant DNA damage as compared to control cells. In addition, TPEN increased the expression of key proteins involved in DNA damage pathways, such as p-ATM, p-chk1, and p-H2AX. RNA silencing revealed the involvement of chk1 and DNA-PK in cell death caused by TPEN, since the silencing of these genes restored cell viability. Further mechanistic studies are underway to assess the role of DNA damage proteins in TPEN anti-colon cancer effects.