Effect of hypoxia on human small cell lung cancer cell line H446

Background and purpose:Hypoxia has been clearly identifi ed as a physiological abnormality associated with solid tumors. Hypoxia can promote genetic instability, protect cancer cell from apoptosis, involve in treatment resistance, enhance metastatic potential and make cancer cells more aggressive. Those might be one of the major reasons accounting for higher malignancy and resistance to drugs in small cell lung cancer(SCLC). This study was to investigate the impact of the hypoxia effect on human small cell lung cancer cell line H446, and the signifi cance of the study not only is benefi cial to our understanding of this progress, but also to fi nd out new therapeutic targets. Methods:TEM, MTT and FACs were utilized to observe cellular morphological changes. The changes have been documented in terms of proliferation ability, medicine-sensitivity changes and the efficacy of drug exclusion and cell cycle of H446 cell line under the hypoxic condition, respectively. Meanwhile, luminometer, flow cytometry and fluorescence microscope were employed to detect the caspase-3/7 activity and generation of ROS, respectively. Furthermore, the expression of GRP78 at the mRNA level was measured by RT-PCR. Results:Under hypoxic condition, mitochondria swelling, organelle bubbling and myelinogenesis were obviously marked in some H446 cells, and microadencavity emerged in a few cells, but mellow damage was observed in most H446 cells. Meanwhile,the proliferation ability of H446 cell decreased signifi cantly, and H446 cells were less sensitive to mechlorethamine hydrochloride, VP-16 and doxorubicin (P0.05), compared with normal condition. Rh123 exclusion effi cacy of H446 cells signifi cantly increased (P0.05). Moreover, Hypoxia induced the arrest of H446 cells in S phase, the G2 phase cells were signifi cantly decreased, even disappeared after 48 h, but the caspase-3/7 activity did not increased until 48 h. Furthermore, FACs showed that ROS increased at fi rst but signifi cantly decreased after 12 h under hypoxic condition, less than that of normoxia. The expression of GRP78 at the mRNA level rapidly reached the peak at 6 h and decreased after 12 h. Conclusion:Hypoxia could inhibit cell growth, induce S phase arrest, increase the efficacy of drug exclusion, decrease apoptotic potential of cells and induce GRP78 stress. Meanwhile, the drug-sensitivities of H446 cells to many drugs decreased. This showed that hypoxia may regulate the biological characteristics of tumor cells and contribute to an increased resistance to chemotherapy through a variety of stress mechanisms.