神经生长因子促进MIA PaCa-2人胰腺癌细胞的增殖

目的：观察神经生长因子-β(nerve growth factorbeta, NGFβ)对人胰腺癌MIA PaCa-2细胞增殖及细胞周期的影响。方法:体外培养MIA PaCa-2细胞,单独或联合给予不同浓度的NGF-β和K252a (NGF-β受体TrKA的抑制剂),应用克隆平板实验、MTT法和流式细胞术检测NGF-β和K252a对MIA PaCa-2细胞克隆形成率、增殖及细胞周期的影响。结果：NGF-β显著促进MIA PaCa-2细胞的克隆形成（P<0.05）,NGF-β使MIA PaCa2细胞增殖能力明显增强（P<0.01）,K252a抑制MIA PaCa-2细胞增殖（P<0.05）,NGF-β与K252a联合作用对MIA PaCa-2细胞的增殖能力无明显影响。NGF-β作用使MIA PaCa2细胞周期阻滞于S期,K252a作用使其周期阻滞于G0/G1期,两者联合作用使MIA PaCa-2细胞周期阻滞于S期。结论：NGF-β具有促进胰腺癌MIA PaCa-2细胞增殖的作用。     

Comparative effects of selected drug combinations on the growth of a human pancreatic carcinoma cell line (MIA PaCa-2)

The inhibitory effect of several drug combinations on the growth of the human pancreatic carcinoma cell line MIA PaCa-2 was studied in relation to drug-scheduling interval in vitro. All drug exposures were for 1 hour. The sequential exposure of cells to 1.5 X 10(-8) M vincristine (VCR) or vindesine (VDS) followed by 2 X 10(-8) M 1,2-dihydroxy-9,10-anthracenedione (DHAD) or 3 X 10(-7) M adriamycin (ADR) had at best an additive effect, demonstrated by isobologram analysis, when the two drugs were given 6 hours apart. Flow cytometry (FCM) analysis after exposure of the cells to the priming drug alone, i.e., VCR or VDS, showed an accumulation of cells in S-phase. The exposure of MIA PaCa-2 cells to 1.6 X 10(-5) M 5-fluorouracil (FUra) followed by 2 X 10(-8) M DHAD or 3 X 10(-7) M ADR had an additive (with DHAD) or synergistic (with ADR) effect when the two drugs were given simultaneously and a synergistic effect with either drug when they were given 2, 6, or 24 hours apart. FCM analysis after exposure to FUra alone showed a rapid S-phase accumulation appearing within 6 hours and increasing further after 24 hours. Sequential exposure of cells to 1.5 X 10(-8) M VCR and 1.6 X 10(-5) M FUra had a synergistic effect, regardless of the sequence or the time interval between the two drugs.     

Initial Approach to the Cellular Irradiation Injury of Human Pancreatic Carcinoma Cell Line MIA PaCa-2 by High Dose per Fraction

OBJECTIVE To investigate an initial approach of radiotherapy,which produces cellular radiation injury by high dose in one fraction.METHODS Human pancreatic carcinoma cell line MIA PaCa-2,was cultivated and divided into 5 groups: 0, 2, 5, 10, 17 Gy.Cultivated cells were irradiated by 6MV-X ray in one fraction.Analysis were done as follows: comet assay, which assessed the level of DNA damage in the treated cells right after the cell was irradiated, flow cytometry, which was performed at 0, 6, 12, 24, 36h after the cell line treated to asses changes of its cell cycle, DNA ladder, which quantitatively assessed the degree of DNA injury after 6 and 12 h, and histological examination, which analyzed cellular morphology after 24 h.RESULTS (1) After X-ray irradiated, the morphological change of human pancreatic carcinoma cell line (MIA PaCa-2) was mainly swelling. (2) When the dose of radiation was lower than 10 Gy,increasing the dose could greatly improve cell necrosis, apoptosis and blockage of cell cycle in G2/M phase, which was consistent with the theory of radiation biology. (3) When radiation dose was more than the 10 Gy, the peak of apoptotic necrosis appeared strong and early. (4) The degree of DNA injury was also related to the dose of radiation therapy and most obvious in the 10 Gy group and not so obvious in the 17 Gy group. (5) When dose was less than 10 Gy, DNA ladder was a single electrophoretic band; in the 10 Gy group, the electrophoresis showed a multiple ladder band;when dose was more than 10 Gy, a vague and irregular band appeared on the electrophoresis.CONCLUSION Oncotic necrosis may be the main cell death style when dose per fraction is high, which differs from conventional dose fraction radiation therapy.     

Enhancement of anchorage-independent growth of human pancreatic carcinoma MIA PaCa-2 cells by signaling from protein kinase C to mitogen-activated protein kinase

We found that 12-O-tetradecanoylphorbol-13-acetate (TPA) promoted anchorage-independent growth but did not affect anchorage-dependent growth of MIA PaCa-2 human pancreatic carcinoma cells. TPA markedly activated mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase in an anchorage-independent manner. Two protein kinase C (PKC) isoforms, conventional PKC (cPKC) and novel PKC (nPKC), but not apical PKC, translocated from the cytosolic to the particulate fraction upon TPA treatment. To identify the PKC isoforms involved in the regulation of anchorage-independent growth, four PKC isoforms (alpha, delta, epsilon, and zeta) were forced to be expressed in MIA PaCa-2 cells with an adenovirus vector. Overexpression of nPKCdelta or nPKC epsilon activated MAPK and promoted anchorage-independent growth. Overexpression of cPKCalpha alone did not influence anchorage-independent growth but lowered the concentration of TPA that was required to enhance such growth. Expression of constitutively active MAPK kinase-1 (MEK1) also promoted anchorage-independent growth. Furthermore, PKC inhibitors or an MEK inhibitor completely suppressed both TPA-induced activation of MAPK and promotion of anchorage-independent growth, but a cPKC-selective inhibitor partially suppressed TPA-induced promotion of the growth. Based on these results, we suggest that MAPK activation, mediated by certain isoforms of PKC, plays a part in oncogenic growth of MIA PaCa-2 cells. In summary, our data indicated that specific inhibitors of the cPKC and nPKC signaling pathway might be selective anti-oncogenic growth agents for some types of human pancreatic cancer.     

Inhibition of human pancreatic cancer cell (MIA PaCa-2) growth by cholera toxin and 8-chloro-cAMP in vitro.

The effects of cholera toxin (CT) and 8-chloro-cAMP (8-Cl-cAMP) on cell growth were investigated using two human pancreatic carcinoma cell lines (MIA PaCa-2, Panc-1). CT, which catalyses the ADP ribosylation of Gs, suppresses the proliferation of MIA PaCa-2(PC) cells. CT at the low dose of 0.1 pg ml-1 was inhibitory of PC cell growth, and the maximum suppression (70%) was achieved at a CT concentration of 100 pg ml-1. This phenomenon was reversible. The production of cAMP by CT (100 pg ml-1) in PC cells was enhanced 320-fold compared with the control. In addition, cAMP analogues (8-Cl-cAMP, 8-Br-cAMP) and forskolin decreased the growth rate of PC cells in a dose-dependent manner. These results support the view that CT suppresses PC cell growth by stimulating cAMP production. Conversely, Panc-1 cells were far less sensitive to CT in cell growth and cAMP production. 8-Cl-cAMP was also less effective on Panc-1 cell growth. The binding of an insulin-like growth factor (IGF)-I and transforming growth factor (TGF)-alpha, which has been shown to stimulate PC cell growth in an autocrine manner, to PC cells was not modified in cells treated with CT or 8-Cl-cAMP. The results suggest that the inhibitory actions of these substances do not occur at the level of the receptor for IGF-I or EGF/TGF-alpha. We have previously shown that phorbol esters, which decrease the binding of TGF-alpha to PC cells, has an anti-proliferative activity on these tumour cells. Inhibited cell growth by maximum suppressive dose of CT or 8-Cl-cAMP was further inhibited by TPA. In addition, an oncogene product of K-ras which is commonly activated in pancreatic cancer, was increased by CT and 8-Cl-cAMP. It is concluded that CT and 8-Cl-cAMP inhibit PC cell growth, presumably in a similar manner, and their mechanism(s) of action may be different from that of TPA. The anti-proliferative effect of CT or 8-Cl-cAMP was enhanced by TPA, implying that the combination of these substances results in increased inhibition of the PC cell growth.     

人脑胶质瘤细胞株MGR2放射抗拒性的诱导

背景与目的:放射治疗是脑胶质瘤重要辅助治疗手段之一,但脑胶质瘤放射敏感性存在很大差异。本研究通过对放射相对敏感的人脑胶质瘤细胞株进行放射诱导得到具有稳定放射抗拒性的后代细胞,从而为研究胶质瘤放射抗拒机制提供具有可比性的成对细胞。方法:选取对X射线相对敏感的人脑胶质瘤细胞株MGR2[2Gy照射下的存活分数(survivalfractionof2Gy,SF2)为0.180±0.05]进行间歇性大剂量X射线照射(每次2Gy,共3次,而后每次5Gy,共2次),每次照射后的细胞继续培养,待5～8周存活的细胞状态稳定后进行下一次照射,整个照射及培养过程历时11个月,最终得到的后代细胞命名为MGR2R(MGR2radiationinduction)。采用MTT法检测MGR2和MGR2R细胞生长的倍增时间,平板集落形成法和线性二次模型(L-Q模型)拟合MGR2和MGR2R细胞的存活曲线并计算相关放射生物学参数和SF2值。血清饥饿细胞周期同步化方法检测MGR2和MGR2R的细胞周期变化。结果:MGR2的倍增时间为3.6天,MGR2R的生长速度减慢,倍增时间为4.0天。MGR2和MGR2R的α值分别为0.447和0.089(t=4.524,P=0.011),β值分别为0.177和0.141(t=1.562,P=0.193),SF2值为0.208和0.478(t=-6.062,P=0.040),MGR2R的放射抗拒性增加。细胞周期同步化后MGR2的细胞周期分布为G1期54.8%,S期30.9%,G2期14.3%,去同步化后G1期35.9%,S期51.2%,G2期12.8%,MGR2R正常生长时存在G2期阻滞(81.7%),同步化后G1期55.7%,S期27.8%,G2期16.6%,去同步化后分别为G1期56.4%,S期26.7%,G2期16.9%,MGR2R存在G1期阻滞,去同步化后两者细胞周期改变不同。结论:人脑胶质瘤细胞株MGR2经间歇性大剂量X射线多次照射后得到的后代细胞MGR2R具有稳定放射抗拒性。MGR2R生长速度减慢,倍增时间延长,同时存在G1和G2期阻滞,可能与其放射抗拒性的产生有关。     

Aldehyde dehydrogenase 1A1 confers intrinsic and acquired resistance to gemcitabine in human pancreatic adenocarcinoma MIA PaCa-2 cells

Gemcitabine (GEM) is the front-line standard chemotherapy used for the treatment of pancreatic cancer; however, chemoresistance to GEM remains the major obstacle to the successful control of this disease. Both the expression levels and activity of aldehyde dehydrogenase 1A1 (ALDH1A1) are important features of tumor-initiating and/or cancer stem cell properties in multiple types of human cancer. As one of the intrinsic properties of cancer stem cells is drug resistance, in this study, we examined the correlation between the level and activity of endogenous ALDH1A1 and GEM resistance in the MIA PaCa-2 cell line that contains high expression levels and activity of ALDH1A1. We used small interfering RNAs (siRNAs) to deplete ALDH1A1 and investigate its potential role in conferring GEM resistance. The ALDH1A1 knockdown markedly reduced ALDH1A1 expression and activity and inhibited cell proliferation. Moreover, the combination of ALDH1A1-siRNA and GEM significantly decreased cell viability, increased apoptotic cell death and increased the accumulation of cells at the S-phase compared to the controls. Our data also demonstrated that ALDH1A1 expression and activity were significantly higher in the GEM-resistant MIA PaCa-2 cell line (MIA PaCa-2/GR), compared to the parental MIA PaCa-2 cell line (MIA PaCa-2/P). In the MIA PaCa-2/GR cells, the combination of ALDH1A1-siRNA and GEM also showed a significant decrease in cell viability and an increase in apoptotic cell death, emphasizing the importance of ALDH1A1 in both intrinsic and acquired GEM resistance. This potentially powerful combination treatment of ALDH1A1-siRNA and GEM warrants further investigation as an effective therapeutic regimen to overcome the resistance of pancreatic cancer to GEM.     

The neurotrophic factor Artemin promotes the motility and invasiveness of MIA PaCa-2 pancreatic cancer cells

Objective  

The aim of this study was to analyze the capacity of Artemin promoting the motility and invasiveness of MIA PaCa-2 pancreatic cancer (PAC) cells.     

Cytotoxic analog of somatostatin containing methotrexate inhibits growth of MIA PaCa-2 human pancreatic cancer xenografts in nude mice.

Nude mice bearing xenografts of MIA PaCa-2 human pancreatic cancer cell line were treated for 4 weeks with AN-51, a somatostatin octapeptide analog D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH2 (RC-121) containing methotrexate attached to the alpha-amino group of D-Phe in position 1. Control groups of mice received saline, RC-121 or methotrexate. Drugs were given in equimolar doses by daily s.c. injections. After 7 days of treatment with 25 micrograms/day of AN-51, tumor growth was completely inhibited although the treatment had to be suspended because of toxic side effects, especially on the gastrointestinal tract, accompanied by major weight loss of the animals. Mice were allowed to recover for 1 week and treatment was continued with 12.5 micrograms/day AN-51. After 2 weeks of additional therapy, tumor volume, percentage change in tumor volume, and tumor weights were significantly decreased, compared with controls, only in the group treated with AN-51. Methotrexate and RC-121 also inhibited tumor growth, but their effects were not statistically significant. AN-51 retained its hormonal activity and decreased serum growth hormone levels in mice. Binding affinity of AN-51 for somatostatin receptors on MIA PaCa-2 cells was found to be 2.5-times lower than that of parent compound RC-121. This is the first report on inhibition of human pancreatic cancer growth in vivo by somatostatin analogs carrying cytotoxic radicals.     

Antitumor effect of a combination of lysine, proline, arginine, ascorbic acid, and green tea extract on pancreatic cancer cell line MIA PaCa-2

Background: Current treatment of pancreatic cancer is generally associated with poor prognosis, even if diagnosed early, owing to its aggressive rate of metastasis and non-responsiveness to chemotherapy and radiotherapy. Matrix metalloproteinases (MMPs) have received much attention in recent years for their role in various malignancies, and have been implicated in tumor invasion, metastasis, and angiogenesis. Aim of Study: Reported antitum or properties of ascorbic acid, lysine, proline, and green tea extract prompted us to investigate the effect of a combination of lysine, proline, arginine, ascorbic acid, and green tea extract on pancreatic cancer cell line MIA PaCa-2 for viability, MMP expression, invasion, and morphology. Methods: Viability was evaluated based on cell proliferation by MTT assay and MMP expression in condition media by gelatinase zymography. Invasion through Matrigel? was assayed and morphology was observed by hematoxylin and eosin (H+E)staining. Data was analyzed by independent sample “t” test. Results: The nutrient mixture (NM) did not inhibit cell proliferation at 10 µg/mL and exhibited a dosedependent antiproliferative effect with maximum inhibition of 38% over the control at demonstrated production of only MMP-9, which showed a dose-dependent decreased expression that was abolished at 100 µg/mL of NM. Invasion through Matrigel was inhibited at 10, 50, 100, and 500 µg/mL by 66%, 66%, 87% and 100%, respectively. H&E staining did not indicate changes even at the highest concentration of NM. Conclusion: Our results suggest that the formulation of green tea extract, lysine, proline, and ascorbic acid, tested as a promising adjunct to standard treatment of pancreatic cancer, by inhibiting MMP expression and invasion without toxic effects—important parameters in cancer metastasis.     

Farnesyltransferase inhibitor (L-744,832) restores TGF-beta type II receptor expression and enhances radiation sensitivity in K-ras mutant pancreatic cancer cell line MIA PaCa-2

Activated ras is known to dysregulate TGF-beta signaling by altering the expression of TGF-beta type II receptor (RII). It is well documented that tumor cells harboring mutant ras are more resistant to radiation than cells with wild-type ras. In this study, we hypothesized that the use of farnesyltransferase inhibitor (FTI, L-744,832) may directly restore TGF-beta signaling through RII expression via ras dependent or independent pathway leading to induction of radiation sensitivity. Two pancreatic cancer cell lines, BxPC-3 and MIA PaCa-2 were used in this study. FTI inhibited farnesylation of Ras protein more significantly in MIA PaCa-2 than BxPC-3 cells. In contrast, MIA PaCa-2 cells were resistant to radiation when compared to BxPC-3 cells. BxPC-3 cells were more resistant to FTI than MIA PaCa-2 cells. In combination treatment, no significant radiosensitizing effect of FTI was observed in BxPC-3 cells at 5 or 10 microM. However, in MIA PaCa-2 cells, a significant radiosensitizing effect was observed at both 5 and 10 microM concentrations (P>0.004). The TGF-beta effector gene p21(waf1/cip1) was elevated in combination treatment in MIA PaCa-2 but not in BxPC-3 cells. In MIA PaCa-2 cells, FTI induced TGF-beta responsive promoter activity as assessed by 3TP-luciferase activity. A further induction of luciferase activity was observed in MIA PaCa-2 cells treated with radiation and FTI. Induction of TGF-beta signaling by FTI was mediated through restoration of the RII expression, as demonstrated by RT-PCR analysis. In addition, re-expression of RII by FTI was associated with a decrease in DNA methyltransferase 1 (DNMT1) levels. Thus, these findings suggest that the L-744,832 treatment restores the RII expression through inhibition of DNMT1 levels causing induction of TGF-beta signaling by radiation and this forms a novel molecular mechanism of radiosensitization by FTI.     

Part II. Initial molecular and cellular characterization of high nitric oxide-adapted human tongue squamous cell carcinoma cell lines

It is not understood why some head and neck squamous cell carcinomas, despite having identical morphology, demonstrate different tumor aggressiveness, including radioresistance. High levels of the free radical nitric oxide (NO) and increased expression of the NO-producing enzyme nitric oxide synthase (NOS) have been implicated in tumor progression. We previously adapted three human tongue cancer cell lines to high NO (HNO) levels by gradually exposing them to increasing concentrations of an NO donor; the HNO cells grew faster than their corresponding untreated (“parent”) cells, despite being morphologically identical. Herein we initially characterize the HNO cells and compare the biological properties of the HNO and parent cells. HNO/parent cell line pairs were analyzed for cell cycle distribution, DNA damage, X-ray and ultraviolet radiation response, and expression of key cellular enzymes, including NOS, p53, glutathione S-transferase-pi (GST-pi), apurinic/apyrimidinic endonuclease-1 (APE1), and checkpoint kinases (Chk1, Chk2). While some of these properties were cell line-specific, the HNO cells typically exhibited properties associated with a more aggressive behavior profile than the parent cells (greater S-phase percentage, radioresistance, and elevated expression of GST-pi/APE1/Chk1/Chk2). To correlate these findings with conditions in primary tumors, we examined the NOS, GST-pi, and APE1 expression in human tongue squamous cell carcinomas. A majority of the clinical samples exhibited elevated expression levels of these enzymes. Together, the results herein suggest cancer cells exposed to HNO levels can develop resistance to free radicals by upregulating protective mechanisms, such as GST-pi and APE1. These upregulated defense mechanisms may contribute to their aggressive expression profile.     

Inhibition of activated K-ras gene by sirna expression cassettes in human pancreatic carcinoma cell line MIAPaCa-2

Objective: To construct the small interfering RNA(siRNA) expression cassettes (SECs) targeting activated K-ras gene sequence and investigate the effects of SECs on K-ras gene in human pancreatic cancer cell line MIAPaCa-2. Methods: Three different sites of SECs were constructed by PCR. The K1/siRNA, K2/siRNA and K3/siRNA were located at the site 194, 491 and 327, respectively. They were transfected into MiaPaCa-2 cells by liposome to inhibit the expression of activated K-ras. In the interfering groups of site 194, 491, we observed the cytopathic effect of confluent MiaPaCa-2 cells after they were incubated for 48 hours, and detected the apoptosis in cells by FACS, then we tested the alternation of K-ras gene in confluent MiaPaCa-2 cells by RT-PCR, immunofluorescence and western blot, respectively. Results: Introductions of the K1/siRNA and K2/siRNA against K-ras into MiaPaCa-2 cells led to cytopathic effect, slower proliferation and increased apoptosis, while the appearances of control MiaPaCa-2 cells remained well. The number of apoptotic cells increased compared with control cells. RT-PCR, immunofluorescence and western blot showed the effects of inhibited expression of activated K-ras gene by RNA interference in the K1/siRNA and K2/siRNA groups. We also found that the introduction of K3/siRNA had no effect on MiaPaCa-2 cells. Conclusion: K1/siRNA and K2/siRNA can inhibit the expression of activated K-ras and decrease the growth of MiaPaCa-2 cells, while K3/siRNA has no such effect, demonstrating that the suppression of tumor growth by siRNA is sequence-specific. We conclude that K-ras is involved in maintenance of tumor growth of human pancreatic cancer, and SECs against K-ras expression may be a powerful tool to be used therapeutically against human pancreatic cancer.     

Dosimetry of single fraction high dose total body irradiation as measured by thermoluminescent dosimeters

Eighty-five patients with acute myelogenous or acute lymphoblastic leukemia were treated at the City of Hope National Medicine Center with chemotherapy, total body irradiation, and bone marrow transplant. The average mid-line dose to these patients was 1002 rad with a uniformity of 8%.     

Antagonistic interactions between gemcitabine and 5-fluorouracil in the human pancreatic carcinoma cell line Capan-2

Although the recently-developed Gemcitabine (GEM) has renewed interest in clinical research in pancreatic carcinoma, it offers modest improvement of tumor-related symptoms and marginal survival advantage, even when combined with other currently-available chemotherapeutic agents such as 5-Fluorouracil (5-FU). We hypothesized that this disappointing result could be due to an interaction between the two drugs affecting cytotoxic activity. We measured in-vitro growth inhibition, cell cycle distribution, gene and protein expression of apoptosis regulators bcl-2, bcl-x and survivin, NFkappaB and telomerase activities of human pancreatic carcinoma cell line Capan-2 following exposure to GEM and 5-FU singly or combined, by MTT assay and median effect analysis, flow cytometry, real-time RT-PCR, Western blotting, electrophoretic mobility shift assay (EMSA) and telomeric repeat amplification protocol (TRAP) assay, respectively. We found cell growth to be inhibited by both drugs, decreasing the percentage of cells in S and G2/M phases and inducing apoptosis, dependent on the levels of bcl-2, bcl-xL and survivin expression in the case of 5-FU, but not for GEM. Moreover, while telomerase activity was reduced equally by both drugs, 5-FU but not GEM effectively downregulated NFkappaB binding activity. Intriguingly, a substantial antagonistic effect was noticed when GEM was combined with 5-FU in the concentration range tested, with the exception of the TRAP assay. These indications of an antagonistic interaction between GEM and 5-FU in some pancreatic cancer context urge further investigation of both genetic and non-genetic differences to identify the variables most relevant for optimal selection and dosing of treatment for the individual patient.     

单次、分次照射与125I 粒子低剂量率照射对人喉鳞癌 Hep2细胞的抑制作用

目的：探讨125I 粒子持续低剂量率照射与分次照射、单次照射对人喉鳞癌细胞 Hep2的抑制作用及其作用机制。方法实验分为无照射对照组（Ctrl 组）、单次照射组（SDR 组）、分次照射组（FDR 组）和125I 粒子持续低剂量率照射组（125I-CLDR 组）四组。采用细胞克隆形成实验法检测 Hep2细胞在不同照射条件下细胞克隆的形成能力;用流式细胞仪检测细胞凋亡和细胞周期阻滞情况;用蛋白印迹法检测不同照射条件后 Hep2细胞总γ-H2AX、CyclinB1、Caspase3蛋白表达的变化。结果经2 Gy、4 Gy、6 Gy 的剂量照射,125I-CLDR 组 Hep2细胞克隆形成率均低于 SDR 组和 FDR 组。经4 Gy 的剂量照射后,125I-CLDR 组 Hep2细胞出现 G2/M 期阻滞,且阻滞效应较 SDR 组及 FDR 组的细胞强;125I-CLDR 组 Hep2细胞的凋亡比例明显高于 SDR 组及 FDR 组;三个照射组γ-H2AX、CyclinB1、Caspase3、NF-κB、P21和 Cdk1的表达水平上调,125I-CLDR 组 p-Cdc25c 蛋白表达水平低于 SDR 组和 FDR 组。结论在本实验条件下,125I 粒子持续低剂量率照射较单次照射、分次照射能够诱发更多 Hep2细胞出现 DNA 损伤、引起持续的 G2/M 期阻滞、诱导细胞凋亡并抑制细胞的再增殖。     

延长分次照射时间对人鼻咽癌细胞CNE1放射生物效应的影响

目的:模拟调强放射治疗模式研究延长分次照射时间对人鼻咽癌细胞系CNE1放射生物效应的影响.方法:研究分组为急速照射组(A组):设0、1、2、4、6、8Gy共6个剂量点,剂量率为2Gy/min,每个剂量点照射单次完成;延长时间照射组(B组),剂量点和剂量率同A组,按照射时间和模式又分为B1组:分2次,15min完成;B2组:分8次,15min完成;B3组:分15次,20min完成;B4组:分22次,30min完成.克隆集落形成试验计算细胞存活率.单击多靶数学模型拟合细胞存活曲线,计算Do,Dq,SF2的值.银染核仁组成区技术观察增殖动力学参数AgNOR面积与胞核面积之比(I/S%值).结果: B组与A组相比,细胞存活率提高5%-10%,有统计学意义.B3、B4组与B1、B2组相比,细胞存活率提高,有统计学意义.A组、B2组和B4组的Do值为0.56Gy、0.60Gy、0.70Gy;Dq值为1.18Gy、1.24Gy、1.30Gy;SF2值为0.209、0.261、0.324;放射前后不同时间点,不同组间的增殖动力学参数(I/S%值)较常规照射没有发生显著变化.结论: IMRT较常规照射对肿瘤的控制率降低,照射剂量200cGy,小于30min的照射时间内肿瘤细胞的增殖动力较常规照射没有发生明显变化.