Induction of lung lesions in Wistar rats by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and its inhibition by aspirin and phenethyl isothiocyanate.

BACKGROUND: The development of effective chemopreventive agents against cigarette smoke-induced lung cancer could be greatly facilitated by suitable laboratory animal models, such as animals treated with the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). In the current study, we established a novel lung cancer model in Wistar rats treated with NNK. Using this model, we assessed the effects of two chemopreventive agents, aspirin and phenethyl isothiocyanate (PEITC), on tumor progression. METHODS: First, rats were treated with a single-dose of NNK by intratracheal instillation; control rats received iodized oil. The animals were then sacrificed on the indicated day after drug administration and examined for tumors in the target organs. PCNA, p63 and COX-2 expression were analyzed in the preneoplastic lung lesions. Second, rats were treated with a single-dose of NNK (25 mg/kg body weight) in the absence or presence of aspirin and/or PEITC in the daily diet. The control group received only the vehicle in the regular diet. The animals were sacrificed on day 91 after bronchial instillation of NNK. Lungs were collected and processed for histopathological and immunohistochemical assays. RESULTS: NNK induced preneoplastic lesions in lungs, including 33.3% alveolar hyperplasia and 55.6% alveolar atypical dysplasia. COX-2 expression increased similarly in alveolar hyperplasia and alveolar atypical dysplasia, while PCNA expression increased more significantly in the latter than the former. No p63 expression was detected in the preneoplastic lesions. In the second study, the incidences of alveolar atypical dysplasia were reduced to 10%, 10% and 0%, respectively, in the aspirin, PEITC and aspirin and PEITC groups, compared with 62.5% in the carcinogen-treated control group. COX-2 expression decreased after dietary aspirin or aspirin and PEITC treatment. PCNA expression was significantly reduced in the aspirin and PEITC group. CONCLUSION: (1) A single dose of 25 mg/kg body weight NNK by intratracheal instillation is sufficient to induce preneoplastic lesions in Wistar rat lungs. (2) COX-2 takes part in NNK-induced tumorigenesis but is not involved in proliferation. (3) Aspirin and PEITC have protective effects in the early stages of tumor progression initiated by NNK.

[Effects of RNA interference of COX-2 gene expression on malignant proliferation of A549 cells in vitro].

OBJECTIVE: To investigate the inhibition of COX-2 gene expression and its effects on malignant proliferation of human lung adenocarcinoma A549 cells after interfering at different target sites in vitro. METHODS: The 3rd, 7th and 10th exon of COX-2 were selected as the targets and three COX-2 siRNA expression vectors with human U6 promoter were constructed. Three siRNA expression vectors and two vacant vectors were transfected into A549 cells expressing COX-2 with lipofectamine, respectively. The transfected cell strains were constructed and the change of COX-2 expression levels was examined by Western blot and RT-PCR. The effects on the proliferation of A549 cells after interfering at different target sites were studied by cell growth curve and colony formation assay in vitro. RESULTS: The three siRNAs and U6 promoter were validated by PCR, restriction endonuclease digestion, DNA sequencing and BLAST alignment, and cloned into the pEGFP vector. The cell strains transfected were named as A549-3, A549-7, A549-10, A549-p and A549-pU6, respectively. A549-p cells showed expression of GFP and A549-3, A549-7, A549-10, A549-p and A549-pU6 cells did not show at 24, 48 and 72 hours after transfection. The results of RT-PCR and Western blot showed an inhibition of COX-2 expression after interfering at three target sites (3rd, 7th and 10th exons). In contrast to A549 cells, the levels of COX-2 mRNA of A549-3, A549-7 and A549-10 cells were reduced by 10.6%, 33.4% and 61.2%, respectively. The levels of COX-2 protein of A549-3, A549-7 and A549-10 cells were reduced by 26.7%, 44.7% and 56.2%, respectively. The results of cell growth curve and colony formation assay showed a slowing down of the growth of A549-10 cells and reduction of their colony formation rate. The other two targets had no apparent effect on the growth of A549 cells. CONCLUSION: There is a significant inhibiting effect of RNA interference on the malignant proliferation of A549 cells in vitro, and the most striking effect can be seen when the 10th exon of COX-2 is taken as the interference target.

[Ectogenous fragile histidine triad gene inhibits the malignant phenotype of human lung cancer cell line A549 in vitro and in vivo].

OBJECTIVE: To investigate the inhibition effects of fragile histidine triad (FHIT) gene on the malignant growth of A549 cell line. METHODS: A mammalian expression vector PEGFP-FHIT was constructed and transfected into the A549 cell line by lipofectamine. Then the transfected cell line was screened by G418. Individual G418-resistant colonies were isolated by limited dilution. The monoclonal transfected cell line was screened by RT-PCR and immunochemical staining. The inhibition growth efficacy of extraneous FHIT was evaluated by clonogenic survival assay, flow cytometry and heteroplastic transplant on nude mice. RESULTS: Presence of extraneous FHIT gene in FHIT-A549 cell was proved by RT-PCR. Immunochemical stain demonstrated that the expression of extraneous FHIT protein was positive in FHIT-A549 cell and negative in PEGFP-A549 cell and A549 cell. The clonal formation rate of FHIT-A549 (2.6%) was significantly lower than that of A549 cell (50.1%) and PEGFP-A549 cell (53.6%, P < 0.01). FHIT-A549 cell (95.8%) was blocked in G(2) phage. Tumorigenicity of A549 cells in nude mice was greatly inhibited by expression of ectogenous FHIT gene. The weight of tumor was significantly lower in FHIT-A549 cell (0.04 +/- 0.03) than in A549 cell (0.24 +/- 0.11) and PEGFP-A549 cell (0.25 +/- 0.07, P < 0.01). CONCLUSIONS: Reintroduction of the expression of ectogeneous FHIT gene can obviously suppress the proliferation and tumorigenicity in human lung cancer cell line A549 and induce apoptosis. The data demonstrate oncosuppressive properties of FHIT gene.

[The relationship between genetic polymorphism of metabolizing enzymes and the genetic susceptibility to lung cancer].

OBJECTIVE: To investigate the relationship between the gene polymorphism of metabolizing enzymes and the genetic susceptibility to lung cancer as well as to study the synergistic effects between smoking and the genes. METHODS: A case-control study (case = 217, control = 200) was carried out to compare the frequent distribution of CYP1A1, 2E1, 2D6 and GSTM1 genotypes between the lung cancer group and the control group with a polymerase chain reaction-restriction fragment polymorphism (PCR-RFLP) method and to analyze the relationship between these genes and smoking. RESULTS: GSTM1-null genotype frequency was 58.5% in the lung cancer group and 47.5% in the control group with significant difference (P = 0.02). The frequent distribution of CYP1A1, 2E1, 2D6 genotypes was not significantly different in the two groups (P > 0.05). Synergistic effects were found between smoking and GSTM1 but not between smoking and CYP1A1, 2E1, 2D6. CONCLUSION: Smoking and GSTM1-null genotype seemed to be the risk factors of lung cancer. Those who carrying GSTM1-null genotype and smoking cigarettes were prone to suffer from lung cancer to become the high-risk population of the disease.

[Growth inhibitory effect of adriamycin conjugated to single-chain antibody on human lung adenocarcinoma in vitro].

OBJECTIVE: To evaluate the growth inhibitory effect of adriamycin (ADM) conjugated to an anti-lung cancer single-chain antibody (ScFv) 2A7-1 on lung adenocarcinoma cell line A2 in vitro. METHODS: 2A7-1 cell culture medium was concentrated by ultra-filtration (with Amicon P10Z filter), and soluble ScFv was purified using RPAS purification kit. ADM was conjugated to 2A7-1 by glutaraldehyde. A(280) and A(490) of the conjugate 2A7-1-ADM were determined by spectrophotometry and the molar ratio of 2A7-1 to ADM was calculated. Immunoreactivity of the conjugate was detected by immunohistochemistry. Its growth inhibitory effect on lung adenocarcinoma cell line A2 was determined by colony formation assay in vitro. RESULTS: The molar ratio of 2A7-1 to ADM was 1:3.2. The conjugate strongly reacted with A2 cell. Its growth inhibitory effect on A2 cells was 4 times as potent as ADM. CONCLUSION: Adriamycin conjugated to anti-lung cancer single-chain antibody 2A7-1 has much higher cytotoxic activity than unconjugated adriamycin against human lung adenocarcinoma.

[Inhibitory effect of p53 with deletion of c-terminal 356 - 393 amino acids on malignant phenotype of human lung cancer cell line].

OBJECTIVE: To study the effect of extraneous p53 gene with deletion of c-terminal 356 - 393 amino acids on inhibition of malignant phenotype of human lung cancer cell line. METHODS: Recombinant plasmid pEGFP-p53 (del) with codon deletion of c-terminal 37 amino acids from 393 to 356 region and pEGFP-p53 (wild type) were constructed. The human lung cancer cell line 801D served as a receipt cell had p53 deletion and mutation at 248 codon. 801D cells, having been transfected by pEGFP-p53 (wild type), pEGFP-p53 (del) or pEGFP, were selected by G418. Growing transfected cells were cloned respectively by method of dilution. Presence of extraneous gene was detected by PCR, their expression in cells was examined by fluorescence microscopy. Cloning efficiency was in vitro tested to examine the cellular proliferating ability. The xenograft in nude mice was performed and xenograft tumors were weighed one month later. Expression of GFP in tumor and transplanted cellular mass were detected by blot slices. RESULTS: pEGFP-p53 (del)-801D, pEGFP-p53-801D and pEGFP-801D were established. Extraneous p53 gene and expression of GFP were found in pEGFP-p53 (del)-801D and pEGFP-p53-801D. Inhibitory rate of colony was 99.6% for pEGFP-p53 (del)-801D and 81.0% for pEGFP-p53-801D. Inhibition of malignant proliferation of extraneous p53 (del) was higher than that of p53 (wild type) (P < 0.01). Even when inhibition of malignant proliferation extraneous pEGFP-p53 (del) was obvious, 0.2% colonies were formed, extraneous p53 and expression of GFP were observed. Animal test showed that tumor on the nude mice was positive (4/4, 4/4) in the control group (801D and pEGFP-801D), but negative (0/4, 0/4) in the experiment group [pEGFP-p53 (del) 801D and pEGFP-p53 (wild type) 801D]. Expression of GFP in the cells of cellular mass transplanted by pEGFP-p53 (del) 801D or pEGFP-p53 (wild type) 801D was observed. CONCLUSION: In vitro inhibitory effect of extraneous p53 gene with deletion of C-terminal 356 - 393 amino acids on malignant growth of lung cancer cell with p53 mutation or deletion at 248 codon is marked. Inhibitory action of p53 on malignant proliferation of cancer cells is heterogeneous.