In vitro modulation of Bcl-2 levels in small cell lung cancer cells: effects on cell viability

Targeting the phosphoinositide 3-kinase p110-α isoform impairs cell proliferation, survival, and tumor growth in small cell lung cancer

PURPOSE

The phosphoinositide 3-kinase (PI3K) pathway is fundamental for cell proliferation and survival and is frequently altered and activated in neoplasia, including carcinomas of the lung. In this study, we investigated the potential of targeting the catalytic class I(A) PI3K isoforms in small cell lung cancer (SCLC), which is the most aggressive of all lung cancer types.

EXPERIMENTAL DESIGN

The expression of PI3K isoforms in patient specimens was analyzed. The effects on SCLC cell survival and downstream signaling were determined following PI3K isoform inhibition by selective inhibitors or downregulation by siRNA.

RESULTS

Overexpression of the PI3K isoforms p110-α and p110-β and the antiapoptotic protein Bcl-2 was shown by immunohistochemistry in primary SCLC tissue samples. Targeting the PI3K p110-α with RNA interference or selective pharmacologic inhibitors resulted in strongly affected cell proliferation of SCLC cells in vitro and in vivo, whereas targeting p110-β was less effective. Inhibition of p110-α also resulted in increased apoptosis and autophagy, which was accompanied by decreased phosphorylation of Akt and components of the mTOR pathway, such as the ribosomal S6 protein, and the eukaryotic translation initiation factor 4E-binding protein 1. A DNA microarray analysis revealed that p110-α inhibition profoundly affected the balance of pro- and antiapoptotic Bcl-2 family proteins. Finally, p110-α inhibition led to impaired SCLC tumor formation and vascularization in vivo.

CONCLUSION

Together our data show the key involvement of the PI3K isoform p110-α in the regulation of multiple tumor-promoting processes in SCLC.

Higher expression of Caveolin-1 inhibits human small cell lung cancer (SCLC) apoptosis in vitro

Small cell lung cancer (SCLC) is the most aggressive type of lung cancer, and its treatment is closely associated with apoptosis. Caveolin-1 plays an important role in the development of a variety of human cancers. This study sought to investigate the influence of Caveolin-1 on the apoptosis of SCLC in vitro. We demonstrate that higher expression of Caveolin-1 leads to inhibition of cisplatin and Ultraviolet Radiation (UVR)-induced apoptosis in SCLC cells; and also could decrease caspase-3 activity and increase the stability of Bcl-2 at the protein level. Our findings illuminate a potential molecular mechanism regarding CAV-1's role as anti-apoptosis protein.

Evaluation of articles on pulmonology published in Brazilian journals other than the Brazilian Journal of Pulmonology

In Brazil, research on pulmonology has become increasingly more visible in recent years. In addition to the Brazilian Journal of Pulmonology, other journals have contributed to that by publishing relevant articles in this area. The objective of this article was to briefly report the most relevant studies on pulmonology that were published in other important Brazilian journals between 2009 and 2010. Altogether, there were 56 articles related to the various subareas that compose the field of respiratory diseases.

MicroRNA-7 inhibits the growth of human non-small cell lung cancer A549 cells through targeting BCL-2

MicroRNAs(miRNAs) are emerging as important regulators in tumorigenesis. Increasing evidences have indicated microRNA-7(miR-7) to be a potential tumor suppressor in several human cancers. However, only a limited number of target genes have been identified so far and its biological function in Non-Small Cell Lung Cancer (NSCLC) remains to be further elucidated. In the present study, we observed a reduction of miR-7 level in NSCLC cell lines. Overexpression of miR-7 not only suppressed NSCLC A549 cells proliferation, induced cell apoptosis and inhibited cell migration in vitro, but also reduced tumorigenicity in vivo. Bioinformatics predictions revealed a potential binding site of miR-7 on 3'UTR of BCL-2 and it was further confirmed by luciferase assay. Moreover, subsequent experiments showed that BCL-2 was downregulated by miR-7 at both transcriptional and translational levels. These results suggest that miR-7 regulates the expression of BCL-2 through direct 3'UTR interactions. Therefore, we postulate BCL-2 to be a novel target possibly involved in miR-7-mediated growth suppression and apoptosis of A549 cells. These findings may provide a basic rationale for the use of miR-7 in the treatment of NSCLC.