Cyclin D1 in non-small cell lung cancer: A key driver of malignant transformation

Summary 

Purpose

To review the evidence implicating the deregulation of cyclin D1 in the pathogenesis of non-small cell lung cancer (NSCLC), and to discuss the opportunities for targeted clinical intervention.

Methods

Data published until June 2006 are summarized, and previously unpublished results from our own research are included.

Results

In normal cells, cyclin D1 complexes with and activates cyclin-dependent kinases (CDK) and acts as a transcriptional regulator. The protein is frequently overexpressed in a wide range of cancers, sometimes coincident with CCND1 (cyclin D1) gene amplification (5–20% of tumours). A low level of somatic mutations have been seen in certain tumours. CCND1 is amplified in NSCLC and cyclin D1 is frequently overexpressed in tumours and pre-invasive bronchial lesions, generally from one parental allele. Mutation analyses revealed a frequent CCND1 gene polymorphism (A870G) that modulates alternative splicing and allows expression of an alternative cyclin D1 transcript (transcript cyclin D1b). The encoded cyclin D1b protein lacks a specific phosphorylation site required for nuclear export. Genotype has been correlated with the risk and/or severity of disease or drug response across a range of malignancies, including lung cancer. Together, these findings suggest a strong pathological role for cyclin D1 deregulation in bronchial neoplasia.

Conclusion

Current data indicate that cyclin D1 overexpression is not a consequence of, but rather a pivotal element in the process of malignant transformation in the lung and other tissues. This understanding may open new avenues for lung cancer diagnosis, treatment and prevention.

Abbreviations: CDK, cyclin-dependent kinase, GSK-3β, glycogen synthase kinase 3β, IHC, immunohistochemistry, NSCLC, non-small cell lung cancer, PCR, polymerase chain reaction, Pts, patients, RACE, rapid identification of complementary DNA ends, RFLP, restriction fragment length polymorphism, RT, reverse transcription, SNP, single nucleotide polymorphism, Thr, threonine

Keywords: Lung cancer, Carcinogenesis, Malignant transformation, Oncogene, Cyclin D1, Cyclin-dependent kinase, Splicing, Gene polymorphism, Nuclear export, Cancer risk