Targeting phosphoinositide 3-kinase signalling in lung cancer

Lung cancer is the leading cause of cancer-related mortality worldwide and more than 1 million people annually die in consequence of lung cancer. Although an improvement in lung cancer treatment could be achieved, especially in the last decade, the development of additional therapeutic strategies is urgently required in order to provide improved survival benefit for patients. Lung cancer formation is caused by genetic modifications commonly caused by tobacco smoking. Numerous studies have demonstrated the role of extracellular growth factors in lung cancer cell proliferation, metastasis, and chemoresistance. Mutations and amplifications in molecules related to receptor tyrosine signalling, such as EGFR, ErbB2, c-Met, c-Kit, VEGFR, PI3K, and PTEN are only some of the alterations known to contribute to the development of lung cancer. The phosphoinositide 3-kinase (PI3K) pathway, fundamental for cell development, growth, and survival, is known to be frequently altered in neoplasia, including carcinomas of the lung. Based on the high frequency of alterations, which include mutations and amplifications, leading to over-activation of certain upstream/downstream mediators, targeting components of the PI3K signalling pathway is considered to be a promising therapeutic approach in cancer treatment. In this article we will summarize the current knowledge about the involvement of PI3K signalling in lung cancer and discuss the development of targeted therapies involving PI3K pathway inhibitors

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

Novel agents targeting the IGF-1R/PI3K pathway impair cell proliferation and survival in subsets of medulloblastoma and neuroblastoma

The receptor tyrosine kinase (RTK)/phosphoinositide 3-kinase (PI3K) pathway is fundamental for cancer cell proliferation and is known to be frequently altered and activated in neoplasia, including embryonal tumors. Based on the high frequency of alterations, targeting components of the PI3K signaling pathway is considered to be a promising therapeutic approach for cancer treatment. Here, we have investigated the potential of targeting the axis of the insulin-like growth factor-1 receptor (IGF-1R) and PI3K signaling in two common cancers of childhood: neuroblastoma, the most common extracranial tumor in children and medulloblastoma, the most frequent malignant childhood brain tumor. By treating neuroblastoma and medulloblastoma cells with R1507, a specific humanized monoclonal antibody against the IGF-1R, we could observe cell line-specific responses and in some cases a strong decrease in cell proliferation. In contrast, targeting the PI3K p110α with the specific inhibitor PIK75 resulted in broad anti-proliferative effects in a panel of neuro- and medulloblastoma cell lines. Additionally, sensitization to commonly used chemotherapeutic agents occurred in neuroblastoma cells upon treatment with R1507 or PIK75. Furthermore, by studying the expression and phosphorylation state of IGF-1R/PI3K downstream signaling targets we found down-regulated signaling pathway activation. In addition, apoptosis occurred in embryonal tumor cells after treatment with PIK75 or R1507. Together, our studies demonstrate the potential of targeting the IGF-1R/PI3K signaling axis in embryonal tumors. Hopefully, this knowledge will contribute to the development of urgently required new targeted therapies for embryonal tumors

Effects of R1507 in combination with targeted therapies in medulloblastoma.

<p>The R1507-insensitive cell line DAOY was incubated with increasing concentrations of the EGFR inhibitor gefinitib (A), the Abl inhibitor imatinib (B), the IGF-1R inhibitor NVP-AEW541 (C) and the mTOR inhibitor rapamycin (D) in presence or absence of the IGF-1R antibody R1507. Cell proliferation was assessed using the MTS assay after 72 h. The data represent the mean of 6 replicates with SD from 3 independent experiments.</p

Sensitivity to R1507 and PIK75, and presence of IGFR in neuroblastoma cell lines LAN1 and LAN1R, a LAN1 cell line resistant to doxorubicin.

<p>(A) R1507 treatment for 48 hours. (B) PIK75 treatment for 48 hours. Error bars represent ±S.D. of means from 3 experiments, each with 3 replicates, except that there was only one experiment with 500 nM PIK75 in B. (C) Western blot analysis of components of the IGF-1R/PI3K pathway in LAN1 and LAN1R whole cell extracts. Src was used as internal loading control. (D) Transfection of LAN1 cells with siRNA targeting the IGF-1R (non-targeting siRNA was used as control. Expression levels of the IGF-1R were assessed by Western blot analysis in LAN1 whole cell lysates after 96 h). Cell proliferation in LAN1 cells upon IGF-1R silencing was assessed in absence or presence of R1507 after 96h by MTS. (*p<0.05).</p

The effect of R1507 on cell proliferation of NB and MB cells.

<p>A panel of NB cell lines (A) and MB cell lines (B) were incubated with increasing concentrations of the antibody R1507 inhibiting the IGF-1R in serum-containing medium. Cell viability was assessed using the MTS assay after 2 days. The data represent the mean with SD from at least 6 replicates and 3 independent experiments.</p

Cell proliferation of NB and MB cells after inhibition of the PI3K p110α.

<p>A panel of NB cell lines (A) and MB cell lines (B) were incubated with increasing concentrations of the specific pharmacological PI3K p110α inhibitor PIK75 in serum-containing medium. Cell viability was assessed using the MTS assay after 2 (NB) or 3 (MB) days. The data represent the mean with SD from at least four replicates and 1–3 independent experiment.</p

Targeted therapies in medulloblastoma.

<p>The MB cell lines Daoy (A) and UW228 (B) were incubated with increasing concentrations of the EGFR inhibitors gefinitib or erlotinib, the Abl inhibitor imatinib, the IGF-1R inhibitor NVP-AEW541 and the mTOR inhibitor rapamycin. Cell proliferation was assessed using the MTS assay after 72 h. The data represent the mean of 6 replicates with SD from 3 independent experiments.</p