Association of cyclin D1 expression in lung cancer and the smoking habits of patients

Lung carcinoma signaling pathways activated by smoking

Lung cancer is the leading cause of cancer death in men and women worldwide, with over a million deaths annually. Tobacco smoke is the major etiologic risk factor for lung cancer in current or previous smokers and has been strongly related to certain types of lung cancer, such as small cell lung carcinoma and squamous cell lung carcinoma. In recent years, there has been an increased incidence of lung adenocarcinoma. This change is strongly associated with changes in smoking behavior and cigarette design. Carcinogens present in tobacco products and their intermediate metabolites can activate multiple signaling pathways that contribute to lung cancer carcinogenesis. In this review, we summarize the smoking-activated signaling pathways involved in lung cancer.

Relationship of phospho-pRb (Ser-807/811) level to exposure to tobacco smoke in primary non-small cell lung cancer

This study was aimed at understanding the effect of smoking on pRb phosphorylation and the clinicopathological significance of phospho-pRb in non-small cell lung cancers (NSCLCs). Phospho-pRb (Ser-807/811) expression was not detected in 149 (39%) of 382 patients, and the mean phospho-pRb (Ser-807/811) level was 5.7%. Squamous cell carcinoma had higher phospho-pRb (Ser-807/811) levels than adenocarcinoma (7.1%+/-10.4% versus 4.7%+/-7.9%; P=0.003). The association between phospho-pRb (Ser-807/811) levels and exposure to tobacco smoke was different according to the statuses of cyclin D1 expression and p16 methylation, suggesting that their statuses might play a role as an effect modifier in the relationship between phospho-pRb (Ser-807/811) levels and exposure to tobacco smoke. In stratified multivariate analysis, phospho-pRb (Ser-807/811) levels were not associated with exposure to tobacco smoke in 38 patients with p16 hypermethylation and cyclin D1 expression >5%, after adjusting for confounding factors. However, in the remaining 344 patients, the mean phospho-pRb (Ser-807/811) levels in patients who had smoked >40 pack years increased by 4.65% (P<0.0001) on average than those who had never smoked. No association was found between the phospho-pRb (Ser-807/811) levels and overall survival. In conclusion, the present study suggests that exposure to tobacco smoke is associated with phosphorylation of pRb in NSCLC patients and its relationship depends on the p16 methylation status and cyclin D1 expression levels.

Effects of cyclin D1 (CCND1) polymorphism on susceptibility to lung cancer in a North Indian population

Cyclin D1 is involved in normal regulation of the cell cycle and plays an important role in the transition from G1 to S phase of the cell cycle. The CCND1 gene has a G-->A polymorphism in exon 4 that increases the frequency of alternate splicing. We analyzed the potential role of CCND1 gene polymorphisms in lung cancer patients (n = 151) and in a matched control population (n = 151). DNA was isolated from blood samples, and exon 4 of CCND1 was amplified by polymerase chain reaction. After digestion with MspI, common CCND1 polymorphic alleles were analyzed by means of agarose gel electrophoresis. The data obtained were analyzed using multiple logistic regression. After adjustment for age, sex, and smoking status, the AG genotype was associated with an increased risk for overall lung cancer (odds ratio OR = 1.7, 95% confidence interval CI = 0.92-3.14). No association was found between AA genotype and risk of lung cancer. In smokers, the combined AG+AA genotypes of CCND1 were found to be significant (OR = 1.9, 95% CI = 1.03-3.71, P = 0.03). No positive association was found between CCND1 genotypes in nonsmokers. The results suggest that the CCND1 A870G gene polymorphisms may increase the risk of lung cancer in smokers from north India.

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

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.

Association of cyclin D1 (G870A) polymorphism with susceptibility to esophageal and gastric cardiac carcinoma in a northern Chinese population

Our aim was to investigate the association of cyclin D1 (G870A) single nucleotide polymorphism with susceptibility to esophageal and cardiac carcinoma in a northern Chinese population. By polymerase chain reaction-single strand conformation polymorphism analysis, cyclin D1 (G870A) genotyping was carried out among 120 patients with esophageal squamous cell carcinoma (ESCC), 87 patients with gastric cardiac adenocarcinoma (CAC), and 183 age- and gender-matched controls. The cyclin D1 genotype distribution among ESCC patients was significantly different from that among healthy controls (chi(2) = 7.372, p = 0.025). The G/G genotype was significantly less frequent among ESCC patients (9.2%) than among healthy controls (20.8%) (chi(2) = 7.192, p = 0.007). The G/G genotype significantly reduced risk for the development of ESCC compared to the combination of G/A and A/A genotypes (adjusted odds ratio [OR] = 0.37, 95% confidence interval [CI] = 0.16-0.83). After stratification according to smoking status, the A/A frequency among smoking ESCC (34.3%) and CAC patients (35.7%) was significantly higher than that among smoking healthy controls (18.6%) (chi(2) = 5.426 and 5.599, p = 0.020 and 0.018, respectively). Smokers with the A/A genotype had an about 2-fold increased risk for both of ESCC and CAC compared to the G/A and G/G genotypes, with an adjusted OR of 2.26 in ESCC (95% CI = 1.14-4.49) and of 2.42 in CAC (95% CI = 1.17-4.98). No correlation between the cyclin D1 genotype and development of ESCC or CAC was found among nonsmokers. Determination of the cyclin D1 (G870A) single nucleotide polymorphism may be suitable to identify individuals with increased risk for ESCC or CAC in the northern Chinese population.