Copper compounds can be alternatives to platinum-based anticancer drugs. This study investigated the effects of a series of ternary copper(II) complexes, [Cu(phen)(aa)(H2O)]NO3·xH2O 1-4 (phen = 1,10-phenanthroline; aa = gly (1), DL-ala (2), sar (3), C-dmg (4)), on metastatic and cisplatin-resistant MDA-MB-231 breast cancer cells and MCF10A non-cancerous breast cells, and some aspects of the mechanisms. These complexes were distinctively more antiproliferative towards and induced greater apoptotic cell death in MDA-MB-231 than in MCF10A cells. 2 and 4 could induce cell cycle arrest only in cancer cells. Further evidence from DCFH-DA assay showed higher induction of reactive oxygen species (ROS) in treated cancer cells but minimal ROS increase in normal cells. DNA double-strand breaks, via a γ-H2AX assay, were only detected in cancer cells treated with 5 μM of the complexes. These complexes poorly inhibited chymotrypsin-like activity in the 20S rabbit proteasome while they did not inhibit the three proteolytic sites of MDA-MB-231 cells at 10 μM. However, the complexes could inhibit degradation of ubiquinated proteins of MDA-MB-231 cells. In addition, compound 4 was found to be effective against cervical (Hela), ovarian (SKOV3), lung (A549, PC9), NPC (Hone1, HK1, C666-1), breast (MCF7, T47D), lymphoma and leukemia (Nalmawa, HL60) and colorectal (SW480, SW48, HCT118) cancer cell lines with IC50 values (24 h) in the 1.7-19.0 μM range. Single dose NCI60 screening of 4 showed the complex to be highly cytotoxic to most cancer cell types and more effective than cisplatin.
The treatment of Acanthamoeba infections remains problematic, suggesting that new targets and/or chemotherapeutic agents are needed. Bioassay-guided screening of drugs that are clinically-approved for non-communicable diseases against opportunistic eukaryotic pathogens is a viable strategy. With known targets and mode of action, such drugs can advance to clinical trials at a faster pace. Recently Bortezomib (proteasome inhibitor) has been approved by FDA in the treatment of multiple myeloma. As proteasomal pathways are well known regulators of a variety of eukaryotic cellular functions, the overall aim of the present study was to study the effects of peptidic and non-peptidic proteasome inhibitors on the biology and pathogenesis of Acanthamoeba castellanii of the T4 genotype, in vitro. Zymographic assays revealed that inhibition of proteasome had detrimental effects on the extracellular proteolytic activities of A. castellanii. Proteasome inhibition affected A. castellanii growth (using amoebistatic assays), but not viability of A. castellanii. Importantly, proteasome inhibitors affected encystation as determined by trophozoite transformation into the cyst form, as well as excystation, as determined by cyst transformation into the trophozoite form. The ability of proteasome inhibitor to block Acanthamoeba differentiation is significant, as it presents a major challenge in the successful treatment of Acanthamoeba infection. As these drugs are used clinically against non-communicable diseases, the findings reported here have the potential to be tested in a clinical setting against amoebic infections.
The cobalt(II), copper(II) and zinc(II) complexes of 1,10-phenanthroline (phen) and maltol (mal) (complexes 1, 2, 3 respectively) were prepared from their respective metal(II) chlorides and were characterized by FT-IR, elemental analysis, UV spectroscopy, molar conductivity, p-nitrosodimethylaniline assay and mass spectrometry. The X-ray structure of a single crystal of the zinc(II) analogue reveals a square pyramidal structure with distinctly shorter apical chloride bond. All complexes were evaluated for their anticancer property on breast cancer cell lines MCF-7 and MDA-MB-231, and normal cell line MCF-10A, using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and morphological studies. Complex 2 was most potent for 24, 48 and 72 h treatment of cancer cells but it was not selective towards cancer over normal cells. The mechanistic studies of the cobalt(II) complex 1 involved apoptosis assay, cell cycle analysis, dichloro-dihydro-fluorescein diacetate assay, intracellular reactive oxygen species assay and proteasome inhibition assay. Complex 1 induced low apoptosis, generated low level of ROS and did not inhibit proteasome in normal cells. The study of the DNA binding and nucleolytic properties of complexes 1-3 in the absence or presence of H2O2 or sodium ascorbate revealed that only complex 1 was not nucleolytic.
Bortezomib is the first proteasomal inhibitor (PI) to be used therapeutically for treating relapse cases of multiple myeloma and mantle cell lymphoma. A proposed mechanism for its action is that it prevents the proteasomal degradation of proapoptotic proteins, leading to enhanced apoptosis. Although the α subunit of hypoxia-inducible factor (HIF)-1 is not degraded with bortezomib treatment, the heterodimeric HIF-1 fails to transactivate target genes. HIF-1 and HIF-2 are related hypoxia-inducible transcription factors that are important for the survival of hypoxic tumor cells. The majority of reports have focused on the effects of bortezomib on the transcriptional activities of HIF-1, but not HIF-2. The present study investigated the effects of bortezomib on HIF-2 activity in cancer cells with different levels of HIF-1α and HIF-2α subunits. HIF-α subunit levels were detected using specific antibodies, while HIF transcriptional activities were evaluated using immunodetection, reverse transcription-polymerase chain reaction and luciferase reporter assay. Bortezomib treatment was found to suppress the transcription and expression of CA9, a HIF-1-specific target gene; however, it had minimal effects on EPO and GLUT-1, which are target genes of both HIF-1 and HIF-2. These data suggest that bortezomib attenuates the transcriptional activity only of HIF-1, and not HIF-2. This novel finding on the lack of an inhibitory effect of bortezomib on HIF-2 transcriptional activity has implications for the improvement of design and treatment modalities of bortezomib and other PI drugs.