Hypoxia microenvironment plays a crucial role during tumor progression and it tends to exhibit poor prognosis and make resistant to various conventional therapies. HIF-1α acts as an important transcriptional regulator directly or indirectly associated with genes involved in cell proliferation, angiogenesis, apoptosis and energy metabolism during tumor progression in hypoxic microenvironment. This study was aimed to investigate the expression pattern of the hypoxia associated genes and their association during breast cancer progression under hypoxic microenvironment in breast cancer cells. Cell proliferation in MCF-7 and MDA-MB-231 cell lines treated with different concentration of CoCl2 was analyzed by MTT assay. Flow cytometry was performed to check cell cycle distribution, whereas cell morphology was examined by phase contrast microscopy in both the cells during hypoxia induction. Expression of hypoxia associated genes HIF-1α, VEGF, p53 and BAX were determined by semiquantitative RT-PCR and real-time PCR. Western blotting was performed to detect the expression at protein level. Our study revealed that cell proliferation in CoCl2 treated breast cancer cells were concentration dependent and varies with different cell types, further increase in CoCl2 concentration leads to apoptotic cell death. Further, accumulation of p53 protein in response to hypoxia as compare to normoxia showed that induction of p53 in breast cancer cells is HIF-1α dependent. HIF-1α dependent BAX expression during hypoxia revealed that after certain extent of hypoxia induction, over expression of BAX conquers the effect of anti-apoptotic proteins and ultimately leads to apoptosis in breast cancer cells. In conclusion our results clearly indicate that CoCl2 simulated hypoxia induce the accumulation of HIF-1α protein and alter the expression of hypoxia associated genes involved in angiogenesis and apoptosis.

A series of new benzimidazole containing compounds 2-((1-R-1-H-benzimidazol-2-yl)phenyl-imino)naphthol HL^1–3 (R = methyl, ethyl or propyl, respectively) have been synthesized by Schiff base condensation of 2-(1-R-1-H-benzo[d]imidazol-2-yl)aniline and 2-hydroxy-1-naphthaldehyde. The reactions of HL^1–3 with Cu(NO₃)₂·2.5H₂O led to the corresponding copper(II) complexes [Cu(L)(NO₃)] 1–3. All the compounds were characterized by conventional analytical techniques and, for 1 and 3, also by single-crystal X-ray analysis. The interactions of complexes 1–3 with calf thymus DNA were studied by absorption and fluorescence spectroscopic techniques and the calculated binding constants (K_b) are in the range of 3.5 × 10⁵ M⁻¹–3.2 × 10⁵ M⁻¹. Complexes 1–3 effectively bind DNA through an intercalative mode, as proved by molecular docking studies. The binding affinity of the complexes decreases with the size increase of the N-alkyl substituent, in the order of 1 > 2 > 3, which is also in accord with the calculated LUMO_complex energies. They show substantial in vitro cytotoxic effect against human lung (A-549), breast (MDA-MB-231) and cervical (HeLa) cancer cell lines. Complex 1 exhibits a significant inhibitory effect on the proliferation of the A-549 cancer cells. The antiproliferative efficacy of 1 has also been analysed by a DNA fragmentation assay, fluorescence activated cell sorting (FACS) and nuclear morphology using a fluorescence microscope. The possible mode for the apoptosis pathway of 1 has also been evaluated by a reactive oxygen species (ROS) generation study.