Altered expression of G1/S regulatory genes occurs early and frequently in lung carcinogenesis in transforming growth factor-beta1 heterozygous mice

Abstract

We developed the AJBL6 transforming growth factor-beta 1 (TGF-beta1) heterozygous (HT) mouse by mating A/J mice with C57BL/6 TGF-beta1 HT mice that shows increased carcinogen-induced lung lesions with decreased latency to examine progressive events in lung tumorigenesis. Mouse cDNA macroarrays were used to identify cell cycle genes that are differentially regulated in ethyl carbamate-induced lung adenocarcinomas compared with normal lung tissue in AJBL6 TGF-beta1 HT mice using probes that were generated from tissues isolated using laser capture microdissection. While expression of the genes for cyclin D1, CDK4, and E2F1 increased in lung adenocarcinomas relative to normal lung, expression of p15(Ink4b), p16(Ink4a), p21(Cip1), p27(Kip1), p57(Kip2), and pRb genes decreased in comparison. Competitive RT-PCR showed that the levels of cyclin D1 and CDK4 mRNAs were 2- and 3-fold higher, respectively, in lung adenocarcinomas than in normal lung, while the mRNAs for p15(Ink4b), p16(Ink4a), p21(Cip1), p27(Kip1), and pRb were 3- to 4-fold lower in adenocarcinomas than in normal lung, thus validating the macroarray findings. Competitive RT-PCR of microdissected lesions also showed that the levels of cyclin D1 and CDK4 mRNAs increased significantly, while the mRNAs for p15(Ink4b) and p27(Kip1) decreased significantly as lung tumorigenesis progressed. Immunohistochemical staining for cyclin D1 and CDK4 showed staining in >80% of nuclei in adenocarcinomas compared with fewer than 20% of nuclei staining positively in normal lung. In contrast, while >60% of normal lung cells showed immunostaining for p15(Ink4b), p16(Ink4a), p21(Cip1), p27(Kip1), and pRb, staining for these proteins decreased in hyperplasias, adenomas, and adenocarcinomas. These data show that multiple components of the cyclin D1/CDK4/p16(Ink4a)/pRb signaling pathway are frequently altered early in lung lesions of AJBL6 TGF-beta1 HT mice that are induced by ethyl carbamate as a function of progressive lung carcinogenesis, suggesting that components of this pathway may be potential targets for gene therapy.

Tea polyphenols can restrict benzo[a]pyrene-induced lung carcinogenesis by altered expression of p53-associated genes and H-ras, c-myc and cyclin D1

“…The increased expression of p53 noted in this study was not accompanied by any change in the expression of p21, p27 and bax, indicating the inability of p53 to influence p21, p27 and bax. However, decreased expression of p21 and p27 was reported in mice lung carcinogenesis [10].…”

“…This may lead to the activation of inflammatory NF-κB and PI3 kinase pathways that functionally interact with proinflammatory signaling pathways and release proinflammatory cytokines to regulate cellular activation and survival in inflammation [41,42]. Deregulation of these genes (i.e., overexpression of c-myc, cyclin D1, H-ras and p53) has been seen during B[a]P, NNK and coal burning smoke-induced mouse lung carcinogenesis [6][7][8][9][10]. B[a]P was found to induce the expression of p53 at both protein and mRNA levels in the A549 and NIH3T3 cell lines [43].…”

“…Kang et al [10] reported altered expression of G1/S-regulatory genes cyclin D1, cyclin-dependent kinase 4 (cdk4), p21, p27, p15 and p16 during early lung carcinogenesis in transforming growth factor-β1 heterozygous mice. K-ras mutation was suggested to be associated with the development of hyperplastic lung lesions in mice, whereas mutation of p53 was found to be associated with the development of adenocarcinoma [11].…”

p57: A multifunctional protein in cancer (Review)

“…Silencing of p57 can abrogate the TGF-ß-induced inhibition of proliferation in primary human limbal epithelial cells (98). Now it is known that p57 participates in the development of lung cancer, leukemia, myeloma and leiomyoma via TGF-ß signaling (99)(100)(101).…”

Transforming Growth Factor-β in Lung Cancer, Carcinogenesis, and Metastasis

“…Reduction of TGF-b RII mRNA expression in progressive stages of lung tumorigenesis in HT mice suggests that loss of TGF-b RII may play an important role in the promotion of lung carcinogenesis in mice with reduced TGF-b1 gene dosage when challenged with carcinogen. Multiple components of the cyclin D/cyclin-dependent kinase-4 (CDK-4)/p16(ink4a)pRb signaling pathway were demonstrated to be frequently altered early in lung tumors of HT mice induced by ethyl carbamate (Kang et al 2002). Heterozygous TGF-b1 mice were also mated with latent activatable (LA) mutated K-ras mice to generate TGF-b1(+/+), K-ras LA (wild-type (WT)/LA) and TGF-b1(+/-), K-ras LA (HT/LA) mice.…”