RESUMEN
<p><b>OBJECTIVE</b>To prepare nanoparticles containing E1A gene and observe the efficiency and feasibility of transfecting E1A gene into human undifferentiated thyroid cancer cell line HTC/3. To examine the sensitivity of transgene cells to X-ray and X-ray-induced apoptosis in those cells.</p><p><b>METHODS</b>Nanoparticle-DNA complex was prepared with PLGA coating adenoviral early expression gene E1A, and the package efficiency, release progress in vitro, and size of the complex were determined. The nanoparticle-DNA was transfected into the HTC/3 cells. Lipofectamine was used to transfect E1A gene as a control. RT-PCR was used to examine E1A gene mRNA expression in the transfected cells. The survival ratio of HTC/3-E1A and control cells, and the growth inhibition ratio induced by different doses of X-ray in HTC/3-E1A cells were examined by MTT assay. The apoptosis in HTC/3-E1A cells induced by 2 Gy X-ray iradiation was examined by flow cytometry and DNA electrophoresis.</p><p><b>RESULTS</b>The package efficiency, release progress in vitro, and size of the nanoparticle-DNA complex were 0.78%, 18 days, and 150-280 nm, respectively when transfected the plasmid at the same level, the nanoparticle group got more positive transgene cell clones than that in lipofectamine group, with a statistically significant difference (P < 0.05). RT-PCR showed that transgenic cells from both nanoparticle-DNA and lipofectamine groups had E1A gene mRNA expression. The HTC/3-E1A cells grew slowly, and their doubling time was prolongated (1.44 times in comparison with that in parental cells). According to IC50, the sensitivity of HTC/3-E1A cells to X-ray was improved 2.9 and 2.8 times, respectively, in comparison with that in HTC/3-Vect and HTC/3 cells. The ratio of subG0/G1 phase of HTC/3-E1A cells was significantly higher than that in HTC/3-Vect and HTC/3 cells (P < 0.01). The ratio of S phase of HTC/3-E1A cells was significantly lower than that in HTC/3-Vect and HTC/3 cells (P < 0.01). A typical DNA ladder pattern of apoptosis in HTC/3-E1A cells was observed by electrophoresis, but not found in HTC/3-Vect and HTC/3 cells.</p><p><b>CONCLUSION</b>A nanoparticle-DNA complex has been successfully prepared, and it may carry a foreign gene into cells. The sensitivity of HTC/3-E1A cells to X-ray is significantly improved. Moreover, apoptosis is induced by x-ray in the E1A gene-transfected cells.</p>