Lung Tumor Cell Growth Research Articles

Arachidonic and docosahexaenoic acids reduce the growth of A549 human lung-tumor cells increasing lipid peroxidation and PPARs

Polyunsaturated fatty acids (PUFAs) play an important role in both induction and prevention of carcinogenic process. It is well known that several types of neoplastic cells show decreased total PUFA content, contributing to their resistance to chemotherapy and lipid peroxidation. In the light of this, human lung cancer A549 cells, with low PUFA content, were exposed to arachidonic or docosahexaenoic acid to investigate the effect of n-6 and n-3 PUFAs on growth and elucidate underlying mechanisms. The bulk of the results showed that both n-6 PUFAs and n-3 PUFAs decrease human lung-tumor cell growth in a concentration-dependent manner, inducing cell death mainly evident at 100microM concentration. The mechanism underlying the antiproliferative effect of n-6 and n-3 PUFAs appeared to be the same, involving changes in fatty acid composition of biomembranes, production of cytostatic aldehydes derived from lipid peroxidation and able to affect DNA-binding activity of AP-1, and induction of PPAR. From these results it may be hypothesized that n-6 PUFAs, like n-3 PUFAs, are able to inhibit tumor growth.

Candidate lung tumor susceptibility genes identified through whole-genome association analyses in inbred mice

We performed a whole-genome association analysis of lung tumor susceptibility using dense SNP maps ( approximately 1 SNP per 20 kb) in inbred mice. We reproduced the pulmonary adenoma susceptibility 1 (Pas1) locus identified in previous linkage studies and further narrowed this quantitative trait locus (QTL) to a region of less than 0.5 Mb in which at least two genes, Kras2 (Kirsten rat sarcoma oncogene 2) and Casc1 (cancer susceptibility candidate 1; also known as Las1), are strong candidates. Casc1 knockout mouse tumor bioassays showed that Casc1-deficient mice were susceptible to chemical induction of lung tumors. We also found three more genetic loci for lung adenoma development. Analysis of one of these candidate loci identified a previously uncharacterized gene Lasc1, bearing a nonsynonymous substitution (D102E). We found that the Lasc1 Glu102 allele preferentially promotes lung tumor cell growth. Our findings demonstrate the prospects for using dense SNP maps in laboratory mice to refine previous QTL regions and identify genetic determinants of complex traits.

GTI-2501, an antisense agent targeting R1, the large subunit of human ribonucleotide reductase, shows potent anti-tumor activity against a variety of tumors

GTI-2501 is a 20-mer oligonucleotide that is complementary to a coding region in the mRNA of R1, the large subunit of ribonucleotide reductase (RNR). In vitro studies, have demonstrated that GTI-2501 decreases mRNA and protein levels of R1 in a sequence-specific and dose-dependent manner. Furthermore, GTI-2501 inhibits the growth of human lung, liver, ovary, brain, melanoma, breast and pancreatic tumor cells in colony forming assays. In vivo studies have shown that GTI-2501 significantly inhibits growth of human colon, pancreas, lung, breast, renal, ovarian, melanoma, brain glioblastoma-astrocytoma, and prostatic tumors in CD-1 nude, Balb/c nude and/or SCID mice. GTI-2501 treatment caused total regression of human breast and renal tumor xenografts in mice. These effects are not observed with a scrambled control oligonucleotide containing the same base content but not complementary to R1. GTI-2501 specifically inhibits metastasis of human melanoma cells to the lungs in CD-1 athymic nude mice and prolongs the survival of mice bearing human lymphoma. Taken together these results suggest that an antisense mechanism of action is responsible for growth inhibition in vitro and in vivo and that GTI-2501 can act as a selective and specific anti-tumor agent.

Gastrin-releasing peptide (GRP) induces angiogenesis and the specific GRP blocker 77427 inhibits tumor growth in vitro and in vivo

Angiogenesis is becoming a major target for antitumor therapies, and identifying new angiogenic factors and their specific inhibitors may provide new avenues for tumor management. Here we identify gastrin-releasing peptide (GRP) as a new angiogenic molecule that is secreted by tumors and acts directly upon GRP receptors in the endothelial cells. Addition of GRP increases endothelial cell migration and cord formation in vitro, and induces angiogenesis in an in vivo assay. We have recently identified a small molecule GRP blocker, compound 77427. This inhibitor significantly reduced endothelial cell cord formation in vitro and angiogenesis in vivo. Conversely, when applied to VEGF-induced angiogenesis, the small molecule did not have any effect, demonstrating its specificity. Furthermore, this GRP blocker was able to reduce lung tumor cell growth in vitro as demonstrated by MTT and clonogenic assays. When applied to a xenograft model with lung cancer cells, compound 77427 reduced tumor volume to undetectable sizes, although when the treatment was suspended, tumors began to grow again at normal rates. Our collective observations indicate that GRP is a new angiogenic peptide and that its inhibition offers an attractive tool to reduce tumor burden.

Antisense Inhibition of Methylenetetrahydrofolate Reductase Reduces Cancer Cell Survival In vitro and Tumor Growth In vivo

Many cancer lines are methionine dependent and decrease proliferation when methionine supply is limited. Methylenetetrahydrofolate reductase (MTHFR) generates the folate derivative for homocysteine remethylation to methionine. We investigated the effect of antisense-mediated inhibition of MTHFR on survival of human cancer cells. We examined the in vitro and in vivo anticancer effects of a combination of MTHFR antisense and standard cytotoxic drugs. Specific antisense against MTHFR (EX5) showed significant inhibitory effects on growth of human colon, lung, breast, prostate, and neuroblastoma tumor cells in vitro compared with that of the control oligonucleotide. Cytotoxic drugs (5-fluorouracil, cisplatin, or paclitaxel) potentiated the effect of EX5. In vivo, antisense alone or in combination with cytotoxic drugs inhibited the growth of human colon and lung carcinoma xenografts. In comparison with control oligonucleotide, treatment with EX5 inhibited growth of colon tumors and lung tumors by 60% and 45%, respectively. EX5 with 5-fluorouracil decreased growth of colon tumors by an additional 30% compared with EX5 alone, and EX5 with cisplatin decreased growth of lung tumors by an additional 40% compared with cisplatin alone. Growth inhibition by EX5 was associated with decreased amounts of MTHFR protein and with increased amounts of an apoptosis marker. Our results confirm that MTHFR inhibition decreases tumor growth and suggest that inhibition of MTHFR by antisense or small molecules may be a novel anticancer approach.

NC381, a novel anticancer agent, arrests the cell cycle in G0-G1 and inhibits lung tumor cell growth in vitro and in vivo.

Although clotrimazole (CLT), an antifungal drug, inhibits tumor cell proliferation and angiogenesis, its clinical application is hampered by significant hepatotoxicity due to the presence of an imidazole moiety. In our attempts to develop CLT analogs that are devoid of imidazole and are as efficacious as CLT, one pharmacophore designated NC381 was generated and shown to inhibit tumor cell growth via a mechanism similar to that of CLT. In vitro, treatment of NCI-H460 nonsmall cell lung cancer (NSCLC) cells with NC381 inhibited growth in a time-dependent manner. Flow cytometric analysis demonstrated that the decrease in cell growth was associated with inhibition of cell cycle progression at the G(1)-S phase transition, resulting in G(0)-G(1) arrest. There was a concomitant inhibition of cyclin D1 expression and subsequent reduction in the formation of the cyclin D1-CDK4 complex. Consistent with a decrease in the cyclin D1-CDK4 complex, NC381 treatment resulted in significant inhibition of pRb phosphorylation. There also were changes in the activity of cell cycle-related proteins, including p16(Ink4) and p27(Kip1). Together, these results are consistent with a model in which NC381 arrests cell cycle progression via inhibition of the pathway that promotes exit from the G(1) phase of the cell cycle. Furthermore, the clinical applicability of NC381 was evaluated in an in vivo murine xenograft model of human NSCLC (NCI-H460). NC381 treatment resulted in significant inhibition of tumor growth. Given the poor prognosis and the limited treatment options available, the present results underscore the potential of NC381 in the treatment of human NSCLC.

Growth inhibition of lung cancer cells by adenosine 5′‐triphosphate

AbstractPreliminary clinical data suggest that adenosine 5′‐triphosphate (ATP) may inhibit lung tumor growth. Because studies of ATP on lung cancer cells are lacking, the aim of the present study was to explore effects of extracellular ATP on the growth and morphology of human lung tumor cells. Five human lung tumor cell lines derived from tumors with different cellular characteristics, i.e., a small cell carcinoma (GLC4), a large cell carcinoma (H460), a squamous cell carcinoma (H520), a mesothelioma (MERO82), and a papillary adenocarcinoma (H441), were exposed to 0, 0.5, 1, 2, and 3 mM ATP. Total cell numbers and dead or damaged cells were measured on days 1, 2, and 3. ATP induced a significant, dose‐dependent growth inhibition in GLC4, H460, H520, and MERO82 cells. In contrast, H441 cells showed already maximal inhibition at 0.5 mM. Compared to untreated control cell lines, a significant growth inhibition (mean ± SEM) of 65 ± 5% (GLC4), 59 ± 5% (H460), 45 ± 5% (H520), 38±2% (MERO82), and 55 ± 8% (H441) was shown after 3 days incubation with 3 mM ATP. ATP also induced changes in morphology and attachment to the substratum. Although not demonstrated by the Trypan Blue exclusion test, on photographs it seems that ATP induces death of GLC4 and H460 cells at higher concentrations. In conclusion, in four out of five explored lung tumor cell lines, ATP induces a dose‐dependent growth inhibition. Lung adenocarcinoma cells show already maximal inhibition at the lowest tested ATP dose. There is a relationship between growth inhibition and morphology changes. Drug Dev. Res. 60:196–203, 2003. © 2003 Wiley‐Liss, Inc.

The inhibitory effect of cisplatin in combination with irradiation on lung tumor cell growth is due to induction of tumor cell apoptosis.

Chemoradiation is becoming an important method of treatment of advanced lung cancer. Although many studies have demonstrated the efficacy of chemoradiation against lung tumors, the mechanism of its effect is still poorly understood. In this study, we analyzed the combined effect of cisplatin (CDDP) and irradiation on human lung cancer cell lines (PC-9 and Lu 134A) in vitro using MTT assay and isobologram analysis. To study whether the combined effect is due to induction of tumor cell apoptosis, we further quantified the nuclear fragmentation of tumor cells by flow cytometric analysis. Our study revealed that a combination of cisplatin and irradiation had an additive inhibitory effect on both PC-9 (adenocarcinoma) and Lu 134A (small cell carcinoma) tumor cell growth. Cisplatin improved the sensitivity of tumor cells to irradiation. The use of both cisplatin and irradiation doses could be reduced without decreasing the inhibitory effect. The additive inhibitory effect was correlated positively with the levels of tumor cell nuclear fragmentation. We concluded that combination treatment with cisplatin and irradiation is effective against lung tumors, not only small cell carcinoma but also non-small cell carcinoma, and the inhibitory effect was due to induction of tumor cell apoptosis.

Therapeutic Effects of Tumor-Reactive Type 1 and Type 2 CD8+ T Cell Subpopulations in Established Pulmonary Metastases

Cytolytic CD8+ T cells fall into two subpopulations based on cytokine-secretion. Type 1 CD8+ cells (Tc1) characteristically secrete IFN-gamma, whereas type 2 CD8+ cells (Tc2) secrete IL-4 and IL-5. We assessed the relative therapeutic effects of adoptively transferred OVA-specific Tc1 and Tc2 CD8+ cells in mice bearing established OVA-transfected B16 melanoma lung metastases. Both Tc1 and Tc2 subpopulations mediated a reduction in lung tumor growth that subsequently prolonged survival times in mice with both early (day 7) and more advanced (day 14) levels of tumor development. CD8+ T cell populations recovered from spleens of tumor-bearing mice receiving Tc1 or Tc2 cells showed markedly enhanced tumor Ag-specific cytolytic and cytokine-releasing activities that correlated with delays in tumor cell growth and progression. Initially, both tumor-reactive Tc1 and Tc2 effector cells accumulated at the tumor site with nearly equal frequency. Tc1 cells persisted, whereas Tc2 cell numbers progressively diminished over time. Titration of Tc1 and Tc2 effector cells showed that protection was dose dependent with the former being 5-fold more effective. Tc2 cells achieved a comparable reduction in lung tumor cell growth at higher concentrations of cell transfer. Tc1 effectors from IFN-gamma-deficient mice were less therapeutically effective than wild-type mice, but there was no significant reduction in activity between corresponding Tc2 populations. We speculate that the effectiveness of Tc1 and Tc2 cells may depend on different mechanisms. These studies suggest a potential role for Tc1 and Tc2 CD8+ subpopulations in tumor regression and immunotherapy.

Inhibition of lung tumor cell growth in vitro and mouse lung tumor formation by lovastatin

The HMG-CoA reductase inhibitor, lovastatin (LOV), has been reported to inhibit Ras farnesylation and the growth of Ras-transformed cells. Mouse lung tumors and human lung adenocarcinomas often have activating mutations in K-ras alleles. In the present study, we determined whether LOV inhibited the growth in vitro of mouse (C10, E9, LM1, LM2, and 82-132) and human (NCl-H125, H292, H441, H460, and H661) nor-transformed and neoplastically transformed lung epithelial cells and whether growth inhibition was related to cell transformation or K-ras activation. LOV inhibited the growth of mouse and human lung cells, but cell sensitivities were unrelated to neoplastic transformation or K-ras mutation. In addition, we evaluated whether LOV could inhibit the formation of lung adenomas induced by the tobacco-specific nitrosamine, 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in mice. LOV was administered in the diet at 0, 40, 160, or 400 ppm ad libitum to male strain A/J mice beginning 1 week after lung tumor induction with NNK (10 mumol/mouse). Mice were euthanized 6 months later. Enumeration of lung tumors revealed that LOV did not affect tumor incidence or size, but significantly reduced tumor multiplicity in a dose-related manner. These data suggest that LOV can suppress the formation of NNK-induced lung tumors, possibly at an early promotional stage. This suppression does not appear to be related to either the presence of mutated K-ras or to changes in K-ras expression.

WAF1, a potential mediator of p53 tumor suppression

The ability of p53 to activate transcription from specific sequences suggests that genes induced by p53 may mediate its biological role as a tumor suppressor. Using a subtractive hybridization approach, we identified a gene, named WAF1, whose induction was associated with wild-type but not mutant p53 gene expression in a human brain tumor cell line. The WAF1 gene was localized to chromosome 6p21.2, and its sequence, structure, and activation by p53 was conserved in rodents. Introduction of WAF1 cDNA suppressed the growth of human brain, lung, and colon tumor cells in culture. Using a yeast enhancer trap, a p53-binding site was identified 2.4 kb upstream of WAF1 coding sequences. The WAF1 promoter, including this p53-binding site, conferred p53-dependent inducibility upon a heterologous reporter gene. These studies define a gene whose expression is directly induced by p53 and that could be an important mediator of p53-dependent tumor growth suppression.