Effect of shRNAmir lentiviral vector-mediated COX-2 silencing on the radiosensitivity of nasopharyngeal carcinoma cells / 南方医科大学学报

<p><b>OBJECTIVE</b>To evaluate the effect of COX-2 silencing on the radiosensitivity of a nasopharyngeal carcinoma (NPC) cell line C666-1.</p><p><b>METHODS</b>Anti-COX-2 C666-1 cell line with COX-2 gene silencing mediated by shRNAmir lentiviral vector and the control cell line Anti-GL-2 C666-1 were exposed to various radiation doses. The clonogenic survival assay and curve fitting was used to calculate the radiobiological parameters and the sensitization enhancement ratio after the radiation. Cell cycle changes were assessed after the exposure by flow cytometric analysis. In a BALB/c nude mouse model, the growth curve of the xenografts was generated and the tumor growth inhibition rate was calculated.</p><p><b>RESULTS</b>Compared with the control cells, Anti-COX-2 C666-1 cells showed obviously lowered values of SF2, D0 and Dq but significantly increased α/β with a sensitivity enhancement ratio of 1.4014. COX-2 gene silencing increased the inhibition rate of the tumor xenografts after the radiation, and caused also decreased percentage of G2/M arrest resulting from the exposure.</p><p><b>CONCLUSION</b>Stable COX-2 silencing in NPC cells can improve the effect of radiotherapy both in vitro and in vivo. By changing the radiobiological parameters, genetically based COX-2 inhibitor may be a potentially promising radiosensitizer of NPC.</p>

B-mode ultrasound for defining planning target volume in intensity-modulated radiotherapy for prostate cancer / 南方医科大学学报

<p><b>OBJECTIVE</b>To define the planning target volume (PTV) margins in intensity-modulated radiotherapy (IMRT) for prostate cancer without imaging guidance using B-mode acquisition and targeting (BAT) ultrasound-based prostate localization.</p><p><b>METHODS</b>Ten patients with prostate cancer underwent BAT ultrasound alignment before each IMRT session. The set-up deviations, each consisting of isocenter displacements in 3 directions (anterior-posterior, right-left lateral, and superior-inferior), were recorded for a total of 225 times and analyzed with Kolmogorov-Smimov (K-S) method.</p><p><b>RESULTS</b>The isocenter shift in each direction, which represented an average from all the patients, was 3.56∓2.71 mm, 4.08∓3.99 mm, and 3.20∓2.92 mm in the lateral (RL), anteroposterior (AP), and superior-inferior (SI) dimensions, respectively, and the deviations in each direction conformed to a normal distribution (P=0.806, P=0.061, and P=0.106, respectively). In the absence of imaging guidance for IMRT for prostate cancer, the PTV margin should expand by 8.97 mm in the right, 1.87 mm in the left, 12.05 mm in the anterior, 3.91 mm in the posterior, 9.06 mm in the superior and 2.66 mm in the inferior to allow 95% isodose curve to cover 90% of the clinical target volume.</p><p><b>CONCLUSION</b>The ultrasound imagining guided localization, with simple operation, nonirradiation and small systemic error, can be real-time corrected.</p>

Radiation-induced G2 phase arrest may contribute to the radioresistance of breast cancer stem cells / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate radiation-induced cell cycle changes of human breast cancer stem cells enriched by suspension culture.</p><p><b>METHODS</b>The tumorigenicity of human breast cancer stem cell line MCF-7 cultured in serum-free media was confirmed in NOD/SCID mice, and the radiosensitivity of the cells was tested by clone formation assay following radiation exposure. Flow cytometry was performed to evaluate radiation-induced cell cycle changes, and the protein expression of pCDC25C (ser216) was measured by Western blotting.</p><p><b>RESULTS</b>After the exposure to 2 Gy radiation, the survived fraction of the cells in suspension culture and those in adherent culture was 0.856 ∓ 0.061 and 0.783 ∓ 0.097, respectively, and the cells in suspension culture showed an obviously greater capacity of tumorigenicity in NOD/SCID mice. The radiation exposure resulted in an obvious increase in the proportion of G2 phase cells from (22.03 ∓ 2.12)% to (45.83 ∓ 2.25)% and significantly increased the expression of pCDC25C (ser216).</p><p><b>CONCLUSION</b>Radiation- induced G2 phase arrest may contribute to the resistance of the breast cancer stem cells to radiotherapy.</p>

Effects of radiosensitivity and X-ray dose on miR-7 expression in nasopharyngeal carcinoma / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effects of radiosensitivity and X-ray dose on the expression of miR-7 in nasopharyngeal carcinoma (NPC) cells.</p><p><b>METHODS</b>Low radiosensitive NPC cells CNE-1 and high radiosensitive NPC cells CNE-2 were exposed to 0, 2 and 8 Gy X-ray. The total RNAs of the cell lines were extracted 10 h after radiation for reverse transcription of miR-7 and 18S rRNA by stem-loop primer and random hexamers, respectively. The non-irradiated CNE-1 cells served as the control sample and the relative quantity of the expression level was calculated after real-time PCR using SyBR green.</p><p><b>RESULTS</b>miR-7 expression differed significantly between CNE-1 and CNE-2 cells (4.49-/+3.62 vs 1.29-/+1.10, F=135.483, P<0.001). The radiation dose also significantly affected the expression of miR-7 in NPC cells (F=39.565, P<0.001). CNE-1 cells with a 2 Gy exposure had the highest expression level of miR-7, while the non-irradiated CNE-1 cells had the lowest expression. CNE-2 cells exposed to 2 Gy X-ray had the lowest expression level of miR-7 and the non-irradiated CNE-2 cells had the highest.</p><p><b>CONCLUSION</b>Radiosensitivity and radiation dose of X-ray have significant effect on the expression of miR-7 in NPC cells, indicating that miR-7 plays an important role in radioresistance of NPC cells to X-ray, and suppressed miR-7 expression may elevate the radiosensitivity of NPC cells.</p>

Determination of the repair half-time of human nasopharyngeal carcinoma cell lines CNE1, CNE2, HONE1 and C666-1 / 南方医科大学学报

<p><b>OBJECTIVE</b>To determine the repair half-time (T1/2), a speed parameter of sub-lethal damage repair (SLDR), of human nasopharyngeal carcinoma (NPC) cell lines CNE1, HONE1, C666-1 and CNE2.</p><p><b>METHODS</b>A total radiation dose of 8 Gy divided into 4+4 Gy was delivered to the cell lines at the interval of 0 s, 15 s, 30 s, 1 h, 2 h, 4 h or 6 h. The cell survival fractions were determined using the standard cell clonogenic assay. The curves of the changes in the surviving cell fraction after a total dose of 8 Gy, as a function of the interval between the two doses of 4 Gy, were fitted manually, and the T1/2 of each cell line was calculated according to the curves.</p><p><b>RESULTS</b>The T1/2 of CNE1, HONE1, C666-1 and CNE2 were 18 s, 22 s, 29 s and 27 s, respectively.</p><p><b>CONCLUSION</b>The speed of SLDR of NPC cells is quite rapid, indicating that the fraction delivery time longer than 20 s might decrease the effect of radiotherapy.</p>

Ginsenoside Rg1 protects rat hippocampal neurons from radiation injury by regulating NOS activity / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the protective effect of ginsenoside Rg1 on cultured rat hippocampal neurons against radiation injury and explore new therapies for preventing radiation encephalopathy.</p><p><b>METHODS</b>Rat hippocampal neurons cultured for 12 days were subjected to a single-dose X-ray exposure of 30 Gy. 4',6-diamidino-2-phenylindole (DAPI) staining was used to detect the neuronal apoptosis and NOS activity kit utilized to evaluate NOS activity in the cells after the exposure.</p><p><b>RESULTS</b>Nuclear condensation was detected in (25.3-/+3.57)% of the neurons 24 h after 30 Gy X-ray exposure, a rate significantly higher than that in the control cells [(1.95-/+0.78)%, P<0.01]. In the neurons pretreated with ginsenoside Rg1, only (7.43-/+1.51)% of the cells presented with nuclear condensation after the exposure, significantly different from the rates in the control cultures and the exposed cultures (P<0.01). The NOS activity of exposed cultures was 6.46-/+0.95 U/ml, significantly higher than that in the control cultures (3.20-/+0.70 U/ml, P<0.01). The NOS activity of the neurons pretreated with ginsenoside Rg1 was 3.85-/+0.69 U/ml, significantly different from that in the control cultures (P<0.05) and the exposed cultures (P<0.01).</p><p><b>CONCLUSION</b>Ginsenoside Rg1 offers significant protective effect on rat hippocampal neurons from radiation-induced apoptosis by reducing the activity of NOS.</p>

p35 and p25 expressions and Cdk5 kinase activity in primary cultured rat hippocampal neurons with X-ray exposure / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the expressions of p35 and p25 and Cdk5 kinase activity in cultured rats hippocampal neurons following X-ray exposure to provide experimental evidence for prevention and treatment of radiation encephalopathy.</p><p><b>METHODS</b>The hippocampal neurons cultured for 12 days were subjected to a single-dose X-ray exposure of 30 Gy. Western blotting was used to detect the p35 and p25 protein levels, and the effect of pretreatment with roscovitine, a Cdk5 inhibitor, on the apoptosis of the hippocampal neurons following the exposure was examined with 4',6-diamidino-2-phenylindole (DAPI) staining.</p><p><b>RESULTS</b>The protein level of p35 increased significantly 3.5 and 4 h after the irradiation by 1.51-/+0.13 and 1.45-/+0.14 folds in comparison with the control level, respectively (P<0.01), and the p25 level increased significantly 6 h after irradiation by 1.62-/+0.28 folds (P<0.05). Nuclear condensation occurred in (24.8-/+3.97)% of the neurons 24 h after 30 Gy X-ray exposure, a rate significantly higher than that in the nonexposed cells [(1.82-/+1.08)%, P<0.01) and that in roscovitine-pretreated neurons [(7.74-/+2.27)%, P<0.01).</p><p><b>CONCLUSION</b>X-ray exposure activates Cdk5 by increasing the p35 and p25 expressions in rat hippocampal neurons, and inhibition of Cdk5 activity with roscovitine can significantly protect the neurons from apoptosis.</p>

Rna interference of annexin II gene in PC3 cells by using small interference RNA synthesized with in vitro transcription / 中国医学科学杂志(英文版)

<p><b>OBJECTIVE</b>To silence annexin II gene expression by using small interference RNA (siRNA) in prostate cancer cell line PC3.</p><p><b>METHODS</b>For in vitro transcription, four sequences of 29-nucleotide DNA template oligonucleotides were designed, and one pair of the sequences were complementary to annexin II gene. The other pair was negative control. The 8 nucleotides at the 3' end of each oligonucleotide were complementary to the T7 Promoter Primer. The sense and antisense siRNA templates were transcribed by T7 RNA polymerase and the resulting RNA transcripts were hybridized to create dsRNA. The siRNA was transfected into prostate cancer cell PC3. For assaying the efficiency of siRNA, confocal microscopy, Northern blotting, and Western blotting were employed to examine the expression of annexin II protein and its mRNA. 3H thymidine was used to measure DNA synthesis.</p><p><b>RESULTS</b>The siRNA sequence specific to annexin II gene was capable of inhibiting the expression of annexin II protein and its mRNA. And cellular DNA synthesis was significantly reduced in siRNA transfected cells.</p><p><b>CONCLUSIONS</b>The protocol for the synthesis of siRNA by T7 RNA polymerase is feasible. Annexin II might be involved in DNA synthesis.</p>

Relationship between radiosensitivity of nasopharyngeal carcinoma and MDR1 gene polymorphism / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the relationship between human multidrug resistancel gene (MDR1) polymorphisms and the radiosensitivity of nasopharyngeal carcinoma (NPC).</p><p><b>METHODS</b>Blood samples were collected from 59 NPC patients, who were devided into radiosensitive or radioresistant groups according to their responses to radiation therapy. The genotypes for MDR1 polymorphisms (G2677T in exon 21 and C3435T in exon 26) and their haplotypes were determined by PCR and restriction fragment length polymorphism analysis. The results were further confirmed by sequencing.</p><p><b>RESULTS</b>The 3435CC genotype was associated with a significantly better response to radiotherapy than combined 3435 CT and TT genotype (P=0.026). The 2677GG genotype was also associated with a better response in comparison with combined 2677 GT and TT genotype, but this relation was not statistically significant. Patients with 2677G-3435C haplotype had a significant better response to radiotherapy than those with the other haplotypes (P=0.017).</p><p><b>CONCLUSION</b>The MDR1 G2677T and C3435T polymorphisms may help predict the response to radiotherapy in NPC patients.</p>