Oncogenic PI3K mutations lead to NF-κB-dependent cytokine expression following growth factor deprivation.

The phosphoinositide 3-kinase (PI3K) pathway is one of the most commonly misregulated signaling pathways in human cancers, but its impact on the tumor microenvironment has not been considered as deeply as its autonomous impact on tumor cells. In this study, we show that NF-κB is activated by the two most common PI3K mutations, PIK3CA E545K and H1047R. We found that markers of NF-κB are most strongly upregulated under conditions of growth factor deprivation. Gene expression analysis conducted on cells deprived of growth factors identified the repertoire of genes altered by oncogenic PI3K mutations following growth factor deprivation. This gene set most closely correlated with gene signatures from claudin-low and basal-like breast tumors, subtypes frequently exhibiting constitutive PI3K/Akt activity. An NF-κB-dependent subset of genes driven by oncogenic PI3K mutations was also identified that encoded primarily secreted proteins, suggesting a paracrine role for this gene set. Interestingly, while NF-κB activated by oncogenes such as Ras and EGF receptor leads to cell-autonomous effects, abrogating NF-κB in PI3K-transformed cells did not decrease proliferation or induce apoptosis. However, conditioned media from PI3K mutant-expressing cells led to increased STAT3 activation in recipient THP-1 monocytes or normal epithelial cells in a NF-κB and interleukin-6-dependent manner. Together, our findings describe a PI3K-driven, NF-κB-dependent transcriptional profile that may play a critical role in promoting a microenvironment amenable to tumor progression. These data also indicate that NF-κB plays diverse roles downstream from different oncogenic signaling pathways.

Neuroantigen-specific, tolerogenic vaccines: GM-CSF is a fusion partner that facilitates tolerance rather than immunity to dominant self-epitopes of myelin in murine models of experimental autoimmune encephalomyelitis (EAE).

BACKGROUND: Vaccination strategies that elicit antigen-specific tolerance are needed as therapies for autoimmune disease. This study focused on whether cytokine-neuroantigen (NAg) fusion proteins could inhibit disease in chronic murine models of experimental autoimmune encephalomyelitis (EAE) and thus serve as potential therapeutic modalities for multiple sclerosis. RESULTS: A fusion protein comprised of murine GM-CSF as the N-terminal domain and the encephalitogenic MOG35-55 peptide as the C-terminal domain was tested as a tolerogenic, therapeutic vaccine (TTV) in the C57BL/6 model of EAE. Administration of GMCSF-MOG before active induction of EAE, or alternatively, at the onset of EAE blocked the development and progression of EAE. Covalent linkage of the GM-CSF and MOG35-55 domains was required for tolerogenic activity. Likewise, a TTV comprised of GM-CSF and PLP139-151 was a tolerogen in the SJL model of EAE. CONCLUSION: These data indicated that fusion proteins containing GM-CSF coupled to myelin auto-antigens elicit tolerance rather than immunity.