ABSTRACT
<p><b>BACKGROUND AND OBJECTIVE</b>Combined hypoxic cytotoxic drugs and chemoradiotherapy is an important mean of oncotherapy, and Tirapazamine (TPZ) is one of the most remarkable drugs. It has been shown that TPZ has a synergistic effect with radiotherapy on tumor cells, but whether TPZ would down-regulate the expression of the hypoxia-induced genes has not been reported. This study was to investigate the hypoxia-induced mRNA expressions of hypoxia inducible factor-1alpha (HIF-1alpha) and osteopontin (OPN) in human nasopharyngeal carcinoma HNE-1 and CNE-1 cells and the radiosensitization of TPZ, a hypoxia-specific drug, on HNE-1 and CNE-1 cells in vitro.</p><p><b>METHODS</b>The IC50 values of TPZ for HNE-1 and CNE-1 cells were measured using MTT assay, and the mRNA expressions of HIF-1alpha and OPN in HNE-1 and CNE-1 cells was determined using RT-PCR under aerobic and hypoxic conditions, respectively. The survival rates of HNE-1 and CNE-1 cells treated with or without TPZ at IC10 in the presence or absence of oxygen for 6 h were determined using colony formation assay following exposure to 1-6 Gy of 60Co radiation. The dose-survival curves were plotted and the values of D0, Dq and SER were calculated as a single-hit multitarget model.</p><p><b>RESULTS</b>The IC50 values of TPZ were 34.81 μmol/L and 35.02 μmol/L in HNE-1 and CNE-1 cells under aerobic condition, and 30.20 μmol/L and 28.48 μmol/L under hypoxic condition, respectively. The expressions of HIF-1alpha and OPN mRNA were reduced by TPZ in HNE-1 cells, but not in CNE-1 cells under hypoxic condition. For the HNE-1 cells, the respective values of D0 and Dq were 0.89 Gy and 0.28 Gy following normoxic irradiation versus 1.47 Gy and 0.44 Gy following hypoxic irradiation. For the CNE-1 cells, the respective values of D0 and Dq were 0.72 Gy and 0.68 Gy following normoxic irradiation versus 0.95 Gy and 0.56 Gy following hypoxic irradiation. The values of D0 and Dq for HNE-1 and CNE-1 cells treated with TPZ under hypoxic condition following irradiation were 0.66 Gy, 0.21 Gy and 0.85 Gy, 0.79 Gy, respectively.</p><p><b>CONCLUSION</b>TPZ can down-regulate hypoxia-induced expression of HIF-1alpha and OPN mRNA of HNE-1 cells and radiosensitize the HNE-1 cells but not CNE-1 cells, and act as a hypoxia modifier.</p>
Subject(s)
Humans , Antineoplastic Agents , Pharmacology , Cell Hypoxia , Cell Line, Tumor , Cell Survival , Radiation Effects , Cobalt Radioisotopes , Down-Regulation , Hypoxia-Inducible Factor 1, alpha Subunit , Genetics , Metabolism , Inhibitory Concentration 50 , Nasopharyngeal Neoplasms , Metabolism , Pathology , Osteopontin , Genetics , Metabolism , RNA, Messenger , Metabolism , Radiation Tolerance , Radiation-Sensitizing Agents , Pharmacology , Triazines , PharmacologyABSTRACT
<p><b>OBJECTIVE</b>To study the influence of a discrete nano-hydroxyapatite crystal (nano-HAp) on lymphatic leukemia P388 behavior by in vivo techniques.</p><p><b>METHODS</b>A nano-HAp was prepared by a neutralization reaction of 0.1 mol calcium hydroxide suspension and 0.06 mol phosphoric acid solutions at room temperature over pH7. The various doses of the nano-HAp only and the nano-HAp mixture with cyclophosphamide (CY) were injected into mice inoculated with solid tumor lymphatic leukemia P388 and dispersed into PRMI 1640 media harvested the leukemia P388 cells. Sixty P388 BALB/C mice were randomly grouped; 36 of them were used as nano-HAp treated groups and 24 mice as the control groups. The leukemia growth in the mice was examined morphologically, histopathologically and under a transmission electron microscope (TEM).</p><p><b>RESULTS</b>The nano-HAp was identified as a hydroxyapatite by an X-ray diffractometry (XRD) and a Fourier transform infrared spectroscopy (FTIR). The morphology and sizes were observed under a TEM. The tissue growth inhibition ratio (weight%) of solid lymphatic leukemia P388 bearing mice treated with nano-HAp at doses 35 mg/kg, 53 mg/kg and nano-HAp (53 mg/kg) combined with CY (35 mg/kg) in 3 consecutive days via intraperitineal injections were 14.95%, 32.67% and 60.45% respectively. Apoptosis of P388 cell cocultured with nano-HAp was confirmed by TEM.</p><p><b>CONCLUSIONS</b>The tissue growth restriction of solid tumor lymphatic leukemia P388 was greater after an injection of nano-HAp only or nano-HAp mixed with CY than that obtained after injection with physiological saline solution as a control (P < 0.01), and the tissue growth restriction of solid tumor after an injection of nano-HAp combined with CY was greater than that obtained after nano-HAp or CY injection only (P < 0.01).</p>