Enhancement of HepG2 cell radiosensitivity by mutant IkappaBalpha gene transfection / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the efficacy of transfection with a mutant IkappaBalpha gene (mIkappaBalpha) in enhancing the radiosensitivity of hepatocellular carcinoma cells.</p><p><b>METHODS</b>The hepatocellular carcinoma Hep G2 cells were divided into 3 group and transfected with the adenovirus containing mIkappaBalpha vector (Ad-mIkappaBalpha group), Ad vector (Adv group), or without treatment (parental control cells). Before and after irradiation of the cells with 6 Gy high-energy X ray, Western blotting was performed to measure the expression level of IkappaBalpha in the cytoplasm, and electrophoresis mobility shift assay (EMSA) carried out to evaluate the nuclear factor-kappaB (NF- kappa;B) activity in the cell nuclei, with the cell apoptosis detected using TUNEL assay. The radiosensitivity of the HepG2 cells were determined by comparison between the 3 groups in term of the surviving cell fractions (SF2) after 2-Gy X-ray exposure, and of the Do and Dq values obtained using the single-hit multi target model.</p><p><b>RESULTS</b>Before the X-ray exposure, the Hep G2 cells in Adv group and the control group showed low levels of IkappaBalpha absorbance in the cytoplasm, which were further decreased after the exposure. The NF-kappaB activity in the nuclei of the cells in the two groups was positive (+) before irradiation, and substantially enhanced (++) after the exposure and maintained the stably activated state. The apoptotic index of the cells in the two groups was 1.4 and 1.6 before irradiation, and increased to 8.9 and 11.7 after the irradiation, respectively. The cells in the Ad-mIkappaBalpha group, however, exhibited high levels of IkappaBalpha absorbance either before or after the irradiation, which were approximately 3 times that of the Adv group, but the NF-kappaB activity remained negative irrespective of the irradiation. The apoptotic index of the cells in the Ad-mIkappaBalpha group was 18.2 before irradiation, was increased to 88.3 after the irradiation. Among the 3 groups, Ad-mIkappaBalpha group had the smallest SF(2) value of 0.301 but the highest sensitivity enhancement ratio (SER) of2.99, with the lowest Do and Dq values (1.468 and 0.709, respectively).</p><p><b>CONCLUSION</b>mIkappaBalpha gene transfection into HepG2 cells inhibits the anti-apoptotic activity of NF-kappaB to enhance the radiosensitivity of the cells.</p>

Magnetic resonance imaging findings of liver injury induced by three-dimensional conformal radiotherapy / 南方医科大学学报

<p><b>OBJECTIVE</b>To analyze the magnetic resonance imaging (MRI) findings of radiation-induced liver injury following three-dimensional conformal radiotherapy.</p><p><b>METHODS</b>A retrospective review of the MRI data was conducted in 20 patients treated between September 2000 and October 2005, who suffered liver injuries induced by 1 or 2 three-dimensional conformal radiotherapy sessions for liver neoplasm. The patients underwent MR scans with T2-weighted sequences and T1-weighted sequences in both plain and Gd-DTPA enhanced MRI. Four patients with suspected tumor relapse suggested by MRI were pathologically confirmed to have radiation-induced liver injury.</p><p><b>RESULTS</b>Acute radiation-induced liver injury was represented by large patches of liver edema consistent with the irradiation volume, showing low signal intensity on T1-weighted images (T1WI) and high signal intensity on T2-weighted images (T2WI) without arterial phase enhancement after Gd-DTPA injection. Delayed radiation-induced liver injury was manifested by slightly low-intensity signal on plain T1WI and slightly high-intensity signal on T2WI without obvious arterial phase enhancement following Gd-DTPA injection but with marked enhancement during the portal-venous and delayed phases.</p><p><b>CONCLUSION</b>Radiation-induced liver injury presents characteristic MRI features, and plain and dynamic enhanced MRI can be of great value for its diagnosis.</p>