[Circ_0000263 improves radiosensitivity of Hela cells by inhibiting the activity of telomerase protein through miR-338-3p/TERT].

Objective: To explore the effect and molecular mechanism of circ_0000263 on HeLa cell activity, apoptosis, telomerase activity, and radiosensitivity. Methods: The Hela cells were divided into si-NC, si-circ, vector, circ_0000263, anti-NC, anti-miR-338-3p, miR-NC, miR-338-3p, si-circ+anti-NC, si-circ+ anti-miR-338-3p, si-circ+vector, si-circ+TERT, sh-NC, sh-circ groups. Reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) was used to detect the expressions of circ_0000263 and miR-338-3p. Cell clone formation array was used to detect cell survival; cell counting kit-8 (CCK-8) to detect cell proliferation; flow cytometry to detect apoptosis; western blot method to detect the expressions of proliferating cell nuclear antigen (PCNA), Cleaved-casp3, telomerase reverse transcriptase (TERT) proteins; double luciferase assay to detect the targeting relationships of circ_0000263 and miR-338-3p, miR-338-3p and TERT; telomere repeat amplification enzyme linked immunosorbent assay (TRAR-ELISA) to detect telomerase activity. Results: Circ_0000263 was highly expressed in Hela cells, miR-338-3p was low expressed, and TERT was highly expressed; circ_0000263 was also highly expressed in Hela cells treated with radiation (P＜0.05). Knockdown of circ_0000263 inhibited the clone formation and cell proliferation ability of HeLa cells, and enhanced the radiosensitivity and apoptosis of HeLa cells. In contrast, knockdown of circ_0000263 decreased PCNA protein expression level and enhanced Cleaved-casp3 protein expression level in HeLa cells (P＜0.05). The apoptosis rate in the si-circ group was (13.19±1.12)%, which was higher than (6.80±0.62)% of si-NC group (P＜0.05). The apoptosis rate in the si-circ+4 Gy group was (24.82±1.57)%, which was higher than (17.00±0.96)% of si-NC+4 Gy group (P＜0.05). Circ_0000263 targeted regulated miR-338-3p, and miR-338-3p targeted regulated TERT. MiR-338-3p was lowly expressed in HeLa cells, and knockdown of circ_0000263 elevated miR-338-3p expression level in HeLa cells. Circ_0000263 regulated TERT expression and inhibited telomerase activity through miR-338-3p. MiR-338-3p/TERT can restore the effect of circ_0000263 on the radiosensitivity of Hela cells. The apoptosis rate in the si-circ+anti-NC group was (27.37±0.89)%, which was higher than (18.22±1.18)% of the si-circ+anti-miR-338-3p group (P＜0.05). The apoptosis rate in the si-circ+vector group was (27.55±0.48)%, which was higher than (20.10±0.68)% of si-circ+TERT group (P＜0.05). After 72 hours of radiation by 4 Gy, the cell survival fraction of si-circ+anti-NC group was 0.41±0.02, which was lower than 0.66±0.03 of the si-circ+anti-miR-338-3p group (P＜0.05); the cell survival fraction of si-circ+vector group was 0.42±0.05, which was lower than 0.70±0.03 of si-circ+TERT group (P＜0.05). Conclusion: Inhibiting the expression of circ_0000263 supresses the proliferation of Hela cells by regulating miR-338-3p/TERT, promotes apoptosis, inhibits telomerase activity, increases the radiosensitivity of cancer cells, and provides a theoretical basis for improving the radiosensitivity of Hela cells.

[Treatment of recurrent chylous leakage after neck dissection for one case with thyroid carcinoma].

The incidence of chylous leakage which is one of serious complications after neck dissection is low. The recurrent chylous leakage is even rare. One patient with recurrent chylous leakage after the operation of thyroid papillary carcinoma is reported to investigate the pathogenesis and effective treatment of recurrent chylous leakage after neck surgery.

G2/M-phase arrest and release in ataxia telangiectasia and normal cells after exposure to ionizing radiation.

Cells from patients with ataxia telangiectasia (AT) are abnormal in their response to irradiation as judged by clonogenic survival and accumulation in G2 phase. The relationship of the results of these two assays, however, is still a matter of controversy. Flow cytometry was used to measure the distribution of cells in the phases of the cell cycle after 2 Gy irradiation in Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs) and SV40-transformed fibroblasts. AT cells showed increased and prolonged accumulation in G2/M phase regardless of the cell type (lymphoblastoid or fibroblast) or complementation group (A, C or D). To test the hypothesis that prolonged accumulation of AT cells in G2 phase after irradiation was not simply a reflection of their radiosensitivity, we gave iso-survival radiation doses to SV40-transformed fibroblasts of two AT and one control cell lines. The two AT cell lines exited from the G2/M-phase block more slowly than control cells after each dose tested. This implies that prolonged accumulation in G2/M phase in AT cells is not directly related to radiosensitivity as measured by clonogenic survival, but that factors involved in the exit from G2 phase after irradiation may be abnormally regulated. We found that G2-phase arrest of AT cells did not necessarily result in a fatal consequence in the first cell cycle after irradiation. Furthermore, G2-phase arrest did not lead to detectable DNA fragmentation characteristic of apoptosis as judged by gel electrophoresis.

Radiosensitivity of ataxia-telangiectasia, X-linked agammaglobulinemia, and related syndromes using a modified colony survival assay.

We used a modified colony survival assay to measure the sensitivity to ionizing radiation of more than 50 lymphoblastoid cell lines from normal individuals and from patients with ataxia-telangiectasia, Nijmegen breakage syndrome variants, and X-linked agammaglobulinemia. All of these disorders are associated with an increased frequency of cancer. Lymphoblastoid cell lines from patients with ataxia-telangiectasia complementation groups A, C, D, and E; ATFresno; Nijmegen breakage syndrome variants V1 and V2; and X-linked agammaglobulinemia showed marked radiosensitivity, whereas ataxia-telangiectasia heterozygotes were similar to controls. Friedreich's ataxia is not associated with increased cancer risk; lymphoblastoid cell lines from two such patients showed normal radiosensitivity. Taken together, these results suggest that some forms of X-ray sensitivity and cancer susceptibility share a common mechanism, such as an enzyme that is necessary both for the repair of radiation damage to DNA and for gene rearrangements during V(D)J recombination.

Purification of bovine bone morphogenetic protein by hydroxyapatite chromatography.

Bovine bone morphogenetic protein (bBMP) induces differentiation of mesenchymal-type cells into cartilage and bone. bBMP has an apparent Mr of 18,500 +/- 500 and represents less than 0.001% of the wet weight of bone tissue. A Mr 34,000 protein resembling osteonectin is separated by extraction with Triton X-100. A Mr 24,000 protein and about half of a Mr 22,000 protein are disassociated from bBMP by precipitation in 1.5 M guanidine hydrochloride. Aggregates of bBMP and a Mr 14,000 protein are insoluble in aqueous media; the bBMP becomes soluble when the Mr 14,000 protein is disassociated in 6 M urea and removed from the solution by ultrafiltration. Three separate molecular species with apparent Mrs 18,500, 17,500, and 17,000 are eluted at 0.10, 0.15, and 0.20 M phosphate ion concentrations, respectively, from a hydroxy-apatite column. The Mr 18,500 protein has the amino acid composition of acidic polylpeptide and includes four half-cystine residues; the pI is 4.9-5.1. The Mr 22,000 component is a chromoprotein resembling ferritin. The NH2-terminal amino acid sequence of the Mr 17,500 protein simulates histone H2B. The Mr 17,000 protein may possess calmodulin activity. Aggregates of the Mr 18,500 and other proteins induce formation of large deposits of bone; the Mr 18,500 protein alone is rapidly absorbed and induces formation of small deposits. None of the other proteins induces bone formation.

Human bone morphogenetic protein (hBMP).

Human bone morphogenetic protein (hBMP) was chemically extracted from demineralized gelatinized cortical bone matrix by means of a CaCl2 X urea inorganic-organic solvent mixture, differential precipitation in guanidine hydrochloride, and preparative gel electrophoresis. hBMP is isolated in quantities of 1 mg/kg of wet weight of fresh bone, and has the amino-acid composition of an acidic polypeptide. The mol wt is 17 to 18 k-Da (kilodaltons). Implants of the isolated 17-kDa protein are very rapidly adsorbed and produce a smaller volume of bone than protein fractions consisting of 24-, 17-, and 14-kDa proteins. Since the isolated 24- and 14-kDA components lack hBMP activity, the kinetics of the bone morphogenetic processes including the function of other proteins as carrier molecules, await investigation.