Acquired differential regulation of caspase-8 in cisplatin-resistant non-small-cell lung cancer.

Failure to efficiently induce apoptosis contributes to cisplatin resistance in non-small-cell lung cancer (NSCLC). Although BCL-2-associated X protein (BAX) and BCL-2 antagonist killer (BAK) are critical regulators of the mitochondrial apoptosis pathway, their requirement has not been robustly established in relation to cisplatin. Here, we show that cisplatin can efficiently bypass mitochondrial apoptosis block caused by loss of BAX and BAK, via activation of the extrinsic death receptor pathway in some model cell lines.

Obatoclax induces Atg7-dependent autophagy independent of beclin-1 and BAX/BAK.

Direct pharmacological targeting of the anti-apoptotic B-cell lymphoma-2 (BCL-2) family is an attractive therapeutic strategy for treating cancer. Obatoclax is a pan-BCL-2 family inhibitor currently in clinical development. Here we show that, although obatoclax can induce mitochondrial apoptosis dependent on BCL-2 associated x protein/BCL-2 antagonist killer (BAX/BAK) consistent with its on-target pharmacodynamics, simultaneous silencing of both BAX and BAK did not abolish acute toxicity or loss of clonogenicity.

Glucocorticoids can activate the alpha-ENaC gene promoter independently of SGK1.

The role of SGK1 (serum- and glucocorticoid-induced protein kinase 1) in the glucocorticoid induction of alpha-ENaC (epithelial Na+ channel alpha subunit) gene transcription was explored by monitoring the transcriptional activity of a luciferase-linked, alpha-ENaC reporter gene construct (pGL3-KR1) expressed in H441 airway epithelial cells. Dexamethasone evoked a concentration-dependent (EC50 approximately 4 microM) increase in transcriptional activity dependent upon a glucocorticoid response element in the alpha-ENaC sequence. Although dexamethasone also activated endogenous SGK1, artificially increasing cellular SGK1 activity by expressing a constitutively active SGK1 mutant (SGK1-S422D) in hormone-deprived cells did not activate pGL3-KR1.

SGK1 activity in Na+ absorbing airway epithelial cells monitored by assaying NDRG1-Thr346/356/366 phosphorylation.

Studies of HeLa cells and serum- and glucocorticoid-regulated kinase 1 (SGK1) knockout mice identified threonine residues in the n-myc downstream-regulated gene 1 protein (NDRG1-Thr(346/356/366)) that are phosphorylated by SGK1 but not by related kinases (Murray et al., Biochem J 385:1-12, 2005). We have, therefore, monitored the phosphorylation of NDRG1-Thr(346/356/366) in order to explore the changes in SGK1 activity associated with the induction and regulation of the glucocorticoid-dependent Na(+) conductance (G (Na)) in human airway epithelial cells.

Proenkephalin assists stress-activated apoptosis through transcriptional repression of NF-kappaB- and p53-regulated gene targets.

The respective pro- and antiapoptotic functions of the transcription factors p53 and nuclear factor kappaB (NF-kappaB), and their potential impact on tumorigenesis and response to tumor therapy are well recognized. The capacity of the RelA(p65) subunit of NF-kappaB to specify a pro-apoptotic outcome in response to some stimuli is less well recognized, but needs to be understood if rational manipulation of the NF-kappaB pathway is to be deployed in cancer therapy. In this report, we provide evidence that the growth-responsive nuclear protein, proenkephalin (Penk), is required, in part, for apoptosis induction, in response to activation or overexpression of p53 and RelA(p65).