Furthermore, the flavones were able to override multiple powerful prosurvival mediators, including bacterial constituents [ e.g., lipoteichoic acid (LTA) and peptidoglycan] and host-derived factors (e.g., GM-CSF), frequently found at increased concentration at sites of inflammation where they act to delay neutrophil apoptosis.
α-TEA disrupted cholesterol-rich microdomains, acted cooperatively with TAM to reduce prosurvival mediators, and induced DR5-mediated mitochondria-dependent apoptosis via an endoplasmic reticulum stress-triggered pro-death pJNK/CHOP/DR5 amplification loop.
Next, we examined the effects of vNox4 on the prosurvival mediators Akt and ERK1/2.
Furthermore, methyl-β-cyclodextrin (MβCD), a chemical disruptor of cholesterol rich microdomains, acted cooperatively with TAM to reduce prosurvival mediators and to induce apoptosis.
These data document that prosurvival signaling is constitutively highly expressed in TAMR cells in comparison with TAMS cells, and that TAM treatment differentially affects prosurvival signaling between TAMS and TAMR cells; TAM downregulates prosurvival mediators in TAMS cells and increases them in TAMR cells.
To determine whether cholesterol-rich lipid microdomains play a critical role in elevated expression of prosurvival mediators in TAMR cells, TAMR cells were cultured with the cholesterol-depleting agent MβCD followed by analyses of proliferation/survival mediators.
Inhibition of adenosine receptors not only abrogates the IS-limiting effect of statins [ 13, 14], but prevents statins from inducing the phosphorylation of the prosurvival mediators ERK 1/2, Akt, and endothelial nitric oxide synthase (eNOS) [ 15].
As shown in Figure 1a, TAM induces the expression of prosurvival mediators HER-1 and HER-2 (total and phosphorylated forms), as well as pAkt, pERK2/1, and pER-α (Ser 167 and 118) in TAMR cells.
The PI3K, AKT, ERK, and mTOR prosurvival mediators are important therapeutic targets, as they are constitutively activated in many cancers and contribute to cancer progression by promoting cellular proliferation and inhibiting cell death signalling pathways (Falasca, 2010).
As expected, MEK and mTOR inhibitors induced increased levels of pAKT and IRS-1, an outcome that limits their clinical anticancer efficacy; importantly, co-treatment with α-TEA was able to block this counterproductive increase in these potent prosurvival mediators.
