Molecular approaches to lung cancer evaluation

Role of nicotinamide N-methyltransferase in non-small cell lung cancer: in vitro effect of shRNA-mediated gene silencing on tumourigenicity

Lung cancer is the second most commonly diagnosed neoplasm, and represents the leading cause of tumour death worldwide. As patients are often diagnosed at a late stage, current therapeutic strategies have limited effectiveness and the prognosis remains poor. Successful treatment depends on early diagnosis and knowledge concerning molecular mechanisms underlying lung carcinogenesis. In the present study, we focused on nicotinamide N-methyltransferase (NNMT), which is overexpressed in several malignancies. First, we analysed NNMT expression in a cohort of 36 patients with non-small cell lung cancer (NSCLC) by immunohistochemistry. Subsequently, we examined NNMT expression levels in the human lung cancer cell line A549 by Real-Time PCR, Western blot and catalytic activity assay, and evaluated the effect of NNMT knockdown on cell proliferation and anchorage-independent cell growth by MTT and soft agar colony formation assays, respectively. NSCLC displayed higher NNMT expression levels compared to both tumour-adjacent and surrounding tissue. Moreover, shRNA-mediated gene silencing of NNMT led to a significant inhibition of cell proliferation and colony formation ability on soft agar. Our results show that the downregulation of NNMT significantly reduced in vitro tumorigenicity of A549 cells and suggest that NNMT could represent an interesting molecular target for lung cancer therapy.

DNA methylation: its role in lung carcinogenesis and therapeutic implications

A new era in the treatment of malignant diseases has been observed through the use of biologic agents targeting growth factor receptors, signaling pathways, gene mutations and others. The results have been impressive in some diseases and modest in others. The discovery of new targets has expanded our knowledge of different mechanisms in tumorigenesis. One of these mechanisms has been DNA methylation, which is an important gene transcription regulator. Although the role of methylation in lung carcinogenesis is not well understood, there is an enormous quantity of evolving data suggesting its critical role in lung cancer. In this review, the authors will discuss methylation in lung carcinogenesis and its possible clinical implications.

PCR-quality DNA isolation from human bronchial aspirates and buccal and eyelid swabs by a simple procedure based on alkaline lysis

There are only a few systematic reports about DNA extraction from routine diagnostic cytological specimens. An inevitable drawback of such techniques is increased spending of time and funds required for obligatory DNA purification. To implement a simple protocol for human DNA isolation from cytological specimens related to lung cancer, bronchial aspirates together with samples collected by swabbing of the inner cheek and eyelid were used. By combining alkaline and temperature lyses it was possible to isolate DNA solution ready for PCR in less than an hour. Testing the method used for amplification of sex chromatin gene fragments showed that it is highly efficient. The presented protocol preserves high-quality DNA that is suitable for PCR-based assays.

Role of p53 in the induction of cyclooxygenase-2 by cisplatin or paclitaxel in non-small cell lung cancer cell lines

Non-small cell lung Cancer (NSCLC) is extremely resistant to chemotherapeutic agents, such as cisplatin. High expression of the inflammatory enzyme cyclooxygenase-2 (COX-2) has been shown to inhibit chemotherapy-induced apoptosis, but little is known about COX-2 regulation upon drug treatment. Recent data indicate the tumor suppressor protein p53 as an important regulator of COX-2. Therefore, TP53 status could change tumor sensitivity to chemotherapy through induction of the anti-apoptotic protein COX-2. The main objective of this work was to analyze the effect of chemotherapy on the expression of COX-2, according to TP53 status. We report herein that lung cancer cell lines expressing wild-type p53, when exposed to cisplatin treatment, induced COX-2 (mRNA and protein), with concurrent synthesis of prostaglandins (PGE(2)). In contrast, COX-2 expression was not changed after cisplatin treatment of cells containing an inactive form of p53. Further, after silencing of wild-type p53 expressed in A549 cells by RNA interference, cisplatin was no longer able to induce COX-2 expression. Therefore, we suggest that induction of COX-2 by cisplatin in NSCLC cell lines is dependent on p53. For paclitaxel treatment, an increase in COX-2 mRNA expression was observed in H460 and A549 (wild-type p53 cell lines). Moreover, paclitaxel treatment increased COX-2 expression in ACC-LC-319 cell lines (p53 null), showing a p53-independent effect. These data may have therapeutic implications in the selection of patients and strategy for future COX-2 inhibition trials.

3p22.1 and 10q22.3 deletions detected by fluorescence in situ hybridization (FISH): a potential new tool for early detection of non-small cell lung Cancer (NSCLC)

BACKGROUND

Our objective was to study the feasibility of detecting chromosomal deletions at 3p22.1 and 10q22.3 by fluorescent in situ hybridization (FISH) and to examine their distribution in different areas of the airway in patients with non-small cell lung cancer.

METHODS

Brush biopsies from the mainstem bronchus on the normal side contralateral to the tumor (NBB) and mainstem bronchus on the tumor side (TBB) were obtained from 122 patients who underwent surgical resection. Touch preparations from the tumor (TTP), normal lung parenchyma, and bronchi adjacent to the tumor were also obtained. Two FISH assays using probes complementary to 3p22.1 and 10q22.3 were used to detect deletions.

RESULTS

NBB showed a relatively low deletion rate of 3p22.1 and 10q22.3 compared with TTP (p < 0.0001). TBB showed a significantly higher rate of deletions compared with NBB but lower than TTP from the tumor (p < 0.05) for both 3p22.1 and 10q22.3. A significantly higher deletion rate was seen at TTP compared with normal lung parenchyma at both the 3p22.1 and 10 q22.3 (p < 0.0001). Correlations were seen between the deletion rates of TTP and TBB at 3p22.1 (rho = 0.61, p < 0.0001) and between TTP and bronchi adjacent to the tumor at 10q22.3 (rho = 0.64, p < 0.0001).

CONCLUSION

Deletions of the 3p22.1 and 10q22.3 regions can be reliably detected by FISH. As one progresses from the contralateral normal bronchus to the bronchus on the side of tumor and the tumor itself, the percentage of chromosomal deletions increases in a statistically significant fashion. This suggests that, FISH analysis of bronchoscopic brushes may be useful for identifying patients at high risk for developing non-small cell lung cancer.

p53 and FHIT mutations and microsatellite alterations in malignancy-associated pleural effusion

Cancer is a genetic disease and thus is influenced by oncogenes and tumor suppressor genes. To determine whether the genetic analysis of pleural fluid can be used to diagnose malignant effusion, we investigated p53 and FHIT mutations and microsatellite alterations (MA) in the pleural fluid of 40 patients with pleural effusion associated with malignancy (ME) and in the pleural fluid of 17 patients with tuberculous pleurisy (TB) as a control group. p53 mutations were detected in five ME patients (13%) and in no TB patient, and FHIT mutations were detected in seven ME patients (18%) and two TB patients (12%). For four microsatellite markers, D3S1234, D3S1285, D9S171, and TP53, in ME patients, loss of heterozygosity (LOH) was seen in 10 (25%), 5 (13%), 10 (25%), and 6 patients (15%), respectively, and microsatellite instability (MI) in 6 (15%), 0 (0%), 1 (3%), and 3 patients (8%), respectively. Using the same markers, in TB patients, LOH was seen in three (18%), one (6%), three (18%), and one (6%), respectively, and MI in one (6%), zero (0%), zero (0%), and zero (0%), respectively. Twenty-five ME cases (63%) exhibited MA (LOH or MI) in at least one marker. Moreover, in four (80%) of five ME cases with negative cytology and no carcinoembryonic antigen increase in pleural fluid, MAs were identified. In ME, positive cytology was found in 42.5%, and positive MA, using four markers, in 63%. Although still limited in terms of sensitivity and specificity, this study shows that molecular diagnostic strategies could enhance the diagnostic yield in cases of malignant effusion.