Ed targeting SOD1 selectively induced cell death in major lymphocytic leukemia cells and ovarian cancer cells, but not their regular counterparts [5]. In human umbilical vein endothelial cells (HUVEC) ATN-224 decreased SOD1 activity, enhanced superoxide and inhibited proliferation but did not induce cell death [12]. This suggests that ATN-224 selectively induces cell death in tumor cells. Peroxynitrite is definitely the key oxidant responsible for ATN-224 induced cell death. Scavenging superoxide, a peroxynitrite precursor, or peroxynitrite directly was shown to become fully protective. Our obtaining that peroxynitrite would be the effector oxidant, in lieu of the previously assumed superoxide [12], assists to recommend important targets of ATN-224 therapy and tumorFree Radic Biol Med. Author manuscript; available in PMC 2014 July 01.Lee et al.Pagetypes that could advantage from ATN-224 treatment. Peroxynitrite can target MnSOD (SOD2) along with the mitochondrial permeability transition (MPT) pore, resulting in mitochondrial dysfunction and induction of cell death [27]. The MPT pore is susceptible to oxidation by peroxynitrite, which may well let for the release of cytochrome c and the activation of caspases, resulting in programmed cell death [27]. The opening of this pore could circumvent the overexpression of anti-apoptotic proteins for instance Bcl-2, Bcl-xL and Mcl-1.1450752-97-2 Chemscene Peroxynitrite also inactivates SOD2 [27]. In particular malignant tumors high levels of SOD2 are related with poor prognosis and in cell models overexpression of SOD2 causes elevated resistance to oxidants and ROS-implicated therapeutics [42]. Inactivation of SOD2 by peroxynitrite could overcome SOD2 overexpression and sensitize cells to ROSgenerating therapeutics. Our information suggest that ATN-224 could prove helpful in tumors with improved SOD or Bcl-2. Despite the fact that our data are constant with inhibition of SOD1 because the most significant impact of ATN-224 for inducing cell death, inhibition of CcOX could also play a part. 1 possibility is that inhibition of CcOX and resulting mitochondrial dysfunction “primes” the cells for apoptosis [43]. In principal leukemia and many myeloma cells Chonghaile et al. demonstrated that mitochondrial “priming”, which describes the proximity towards the apoptotic threshold, correlates to far better response and clinical outcome [43]. While ATN-224 is usually a moderate to poor inhibitor of CcOX at millimolar concentrations in standard hepatic mitochondria [12], in our tumor model, ATN-224 abolished CcOX activity in the WEHI7.2 and WEHI7.2 variants. Treatment with ATN-224 decreased m to almost the identical extent inside the WEHI7.Formula of 2-Aminobenzaldehyde 2 and WEHI7.PMID:23460641 two variants. Use of ATN-224 to target CcOX and reduce m, in place of working with promiscuously interacting BH3 peptides [43], may be one more, a lot more particular approach to “prime” mitochondria and hence boost the efficacy of cytotoxic agents like doxorubicin, vincristine and etoposide. Although we’ve got focused on inhibiton of SOD1 and CcOX as targets of ATN-224 you will discover other copper-dependent enzymes that may perhaps also contribute for the observed impact [44]. This possibility remains to be tested. Overexpression of Bcl-2 is usually a main mechanism of chemoresistance in lymphoid malignancies. The improvement of BH3 mimetics, that straight target the canonical function of Bcl-2, are in clinical trials [45]. While these mimetics have shown promise, upregulation of other anti-apoptotic proteins, like Mcl-1, lead to chemoresistance [46]. Here we report a different approach to circumvent Bcl.