| BackgroundNasopharyngeal carcinoma (NPC), a highly malignant tumor that can easilymetastasize, is highly prevalent in Southeast Asia, particularly in south China. Theincidence of NPC varies from races and regions. It is lower than one millionth inwestern countries, but 20-100 times higher in our country and Southeast Asia, andthere is a growing tendency in endemic areas.The current treatment of NPC is mainly by radiotherapy, or synthetic therapycombineing with chemotherapy and operation. Although the therapeutic efficacyis found better in early stage, it is unsatisfactory for those patients in middle andadvanced stage. The primary cause of death is local recurrence and distantmetastasis. With the development of computer technology, radiation physics,radiobiology and the promotion of radiotherapy experience in recent years, thecontrol rate of local tumor have been obviously promoted. However, radiotherapyor synthetic therapy, which directly targets to tumor cells, has its weaknesses suchas insensitivity to radiotherapy, disorders of delivery and penetrativity forchemotherapeutics and drug resistance as well. Therefore, it is necessary to explore more effective treatments to enhance the control rate of local NPC as wellas to reduce and prevent metastasis to distant organs.Biotherapy and gene therapy were "hot spot" in current tumor clinicalresearch. As one of the most important tumor biotherapy agents, interferon havebeen widely used alone or with chemotherapeutics for the treatment of more thanfourteen kinds tumors such as liver cancer, hairy-cell leukemia, lymphadenoma,malignant melanoma, lung cancer and renal cell carcinoma etc. And certaincurative effect have been achieved in the treatment. However, only a little attentionhas been paid to the biological effects of interferon to NPC.Interferon protein has been extensively investigated for antitumor treatment,however, in the form of protein drug, its side effects is strong and need long-termadministration. Gene therapy, which can deliver gene encoding interferon andstably express bioactive interferon protein in vivo, may provide a solution to theseproblems. The key issue of gene therapy is the selection of vectors capable of safe,effective and long-term expression without vector-associated toxicity or immunity.Recombinant adeno-associated virus (rAAV) vector is a promising candidate forcancer gene therapy because of its non-pathogenicity, non-immunogenicity andefficient transfection, rAAV is able to integrate into the host genome and mediateefficient and long-term gene transduction across a wide range of dividing ornon-dividing mammalian cells.Based on the aboving background, we used recombinant adeno-associatedvirus to mediate interferon-α-1b gene transduction, studied its effects on xenografttransplanted human nasopharyngeal carcinoma in nude mice, and comparedominance of recombinant adeno-associated viral vector mediating humaninterferon-α-1b gene therapy with interferon-α-1b proteinum. ObjectiveTo investigate interferon antitumor mechanism and provide experimental datafor the feasibility of nasopharyngeal carcinoma interferon gene therapy and a newway for nasopharyngeal carcinoma, we used adeno-associated virus-mediatedhuman interferon-α-1b to study the inhibitory effect on growth and metastasis ofhuman nasopharyngeal carcinoma in nude mice and compare its advantage withinterferon-α-1b proteinum in vivo.MethodsThe xenografted model of liver nasopharyngeal carcinoma was established byinjecting the human nasopharyngeal carcinoma cell line CNE-2 into the liver ofnude mice. Forty nude mice were randomly divided into four groups by randomnumber table method, with ten mice in each group. (Group A: rAAV-IFN-α-1b,Group B: IFN-α-1b; Group C: rAAV-EGFP; Group D: PBS). 24 hours later, A, Cand D group was injected with rAAV-IFN-α-1b encoding human Interferon-α-1b,rAAV-EGFP and phosphate buffer saline via tail vein injection. After 5 days, micein group B was injected with human Interferon-α-1b protein once per two day.Three weeks later five nude mice in each group were randomly chosen forsacrificed and then observe their liver tumor formation and pulmonary metastasis.Tumor size was measured and tumor inhibition ratio were calculated, and apoptoticindex (AI) was detected by terminal deoxyribonucleotide transferase-mediateddUTP nick-end-labeling, (TUNEL). The contents of IFN-αcontained in peripheralblood and mice IL-12 was determined by high performance liquid chromatographychip techniques respectively. And other five mice were left for the observation ofsurviving study. Data were analyzed with SPSS12.0. ResultsAfter human nasopharyngeal carcinoma implants in nude mice liver 3 weeks,the average volum of A group(0.11±0.12)cm~3 and B group(0.42±0.14)cm~3 weresignificantly lower than that of C group(2.48±0.64)cm~3 and Dgroup(2.68±0.70)cm~3 (F=38.536 P＜0.001). Compared with D group, therestrained percentage of tumor in group A was 95.74％and group B was 84.24％.Staining with hematoxylin-eosin indicated that in group C and group D. Necrosiswas rarely observed while tumor cells grew extensively, and metastasized tumorswere found in lung tissues. However, large areas of necrosis can be observed in thetumor tissues, and tumor was not found in lung tissues in group A and group B.This indicated that IFN-α-1b inhibited the tumor metastasis. The apoptotic indexincreased significantly in group A(21.88±3.29)％and group B(19.85±1.96)％versus group C(4.37±0.50)％and group D(3.40±1.05)％(F=120.964 P＜0.001).The average content of interferon-αin serum increased significantly in groupA(101.50±11.33)pg/ml and group B(91.55±9.80)pg/ml versus groupC(23.06±4.36)pg/ml and group D(16.93±9.96)pg/ml(F=69.128 P＜0.001).Theaverage content of IL-12 increased significantly in group A (80.36±13.35)pg/mlpg/ml and group B(51.15±9.72)pg/ml versus group C(19.44±7.03)pg/ml and groupD(14.49±4.21)pg/ml(F=57.116 P＜0.001). The survival time of tumor bearingmice in group A (55.80±2.77)d and group B (48.20±2.39)d was significantly longerthan group C (35.40±2.61)d and group D (36.80±1.92)d(x~2=25.623 P＜0.001).ConclusionsInterferon-α-1b can inhibit the growth and metastasis of nasopharyngealcarcinoma cell line CNE-2 in xenografted model of mice liver and prolong the lifespan of nude mice. rAAV-mediated Inferon-α-1b gene therapy indicated more efficengcy than Interferonα-1b protein. Intravenous injection rAAV-IFN-α-1b andsubcutaneous injection IFN-α-1b can induce the apoptosis of NPC cells in nudemice and promote the formation of IL-12 and enhance immunoloregulation effectsof IFN-α-1b in nude mice.
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