Background: To date all efforts to develop a malaria vaccine have failed, reflecting the still fragmentary knowledge about protective mechanisms against malaria. In order to evaluate if vaccination changes responses of the anti-malaria effectors spleen and liver to blood stage malaria, BALB/c mice succumbing to infection with Plasmodium chabaudi were compared to those surviving after vaccination.

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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-a and p110-b and the antiapoptotic protein Bcl-2 was shown by immunohistochemistry in primary SCLC tissue samples. Targeting the PI3K p110-a with RNA interference or selective pharmacologic inhibitors resulted in strongly affected cell proliferation of SCLC cells in vitro and in vivo, whereas targeting p110-b was less effective. Inhibition of p110-a 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-a inhibition profoundly affected the balance of pro-and antiapoptotic Bcl-2 family proteins. Finally, p110-a inhibition led to impaired SCLC tumor formation and vascularization in vivo.Conclusion: Together our data show the key involvement of the PI3K isoform p110-a in the regulation of multiple tumor-promoting processes in SCLC.

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.

<div>Abstract<p><b>Purpose:</b> 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.</p><p><b>Experimental Design:</b> 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.</p><p><b>Results:</b> 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 <i>in vitro</i> and <i>in vivo</i>, 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 <i>in vivo</i>.</p><p><b>Conclusion:</b> Together our data show the key involvement of the PI3K isoform p110-α in the regulation of multiple tumor-promoting processes in SCLC. <i>Clin Cancer Res; 19(1); 96–105. ©2012 AACR</i>.</p></div>

<p>PDF file - 1196K, PI3K inhibition reduces vascularization in vivo</p>

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<p>PDF file - 1030K, PI3K inhibition blocks SCLC cell viability and PI3K downstream signaling</p>