Evidence for two apoptotic pathways in light-induced retinal degeneration.

Excessive phototransduction signaling is thought to be involved in light-induced and inherited retinal degeneration. Using knockout mice with defects in rhodopsin shut-off and transducin signaling, we show that two different pathways of photoreceptor-cell apoptosis are induced by light. Bright light induces apoptosis that is independent of transducin and accompanied by induction of the transcription factor AP-1. By contrast, low light induces an apoptotic pathway that requires transducin. We also provide evidence that additional genetic factors regulate sensitivity to light-induced damage. Our use of defined mouse mutants resolves some of the complexity underlying the mechanisms that regulate susceptibility to retinal degeneration.

Oligomycin-induced bioenergetic adaptation in cancer cells with heterogeneous bioenergetic organization.

Cancer cells constantly adapt to oxidative phosphorylation (OXPHOS) suppression resulting from hypoxia or mitochondria defects. Under the OXPHOS suppression, AMP-activated protein kinase (AMPK) regulates global metabolism adjustments, but its activation has been found to be transient. Whether cells can maintain cellular ATP homeostasis and survive beyond the transient AMPK activation is not known. Here, we study the bioenergetic adaptation to the OXPHOS inhibitor oligomycin in a group of cancer cells. We found that oligomycin at 100 ng/ml completely inhibits OXPHOS activity in 1 h and induces various levels of glycolysis gains by 6 h, from which we calculate the bioenergetic organizations of cancer cells. In glycolysis-dominant cells, oligomycin does not induce much energy stress as measured by glycolysis acceleration, ATP imbalance, AMPK activation, AMPK substrate acetyl-CoA carboxylase phosphorylation at Ser(79), and cell growth inhibition. In OXPHOS-dependent LKB1 wild type cells, oligomycin induces 5-8% ATP drops and transient AMPK activation during the initial 1-2 h. After AMPK activation is completed, oligomycin-induced increase of acetyl-CoA carboxylase phosphorylation at Ser(79) is still detected, and cellular ATP is back at preoligomycin treatment levels by sustained elevation of glycolysis. Cell growth, however, is inhibited without an increase in cell death and alteration in cell cycle distribution. In OXPHOS-dependent LKB1-null cells, no AMPK activation by oligomycin is detected, yet cells still show a similar adaptation. We also demonstrate that the adaptation to oligomycin does not invoke activation of hypoxia-induced factor. Our data suggest that cancer cells may grow and survive persistent OXPHOS suppression through an as yet unidentified regulatory mechanism.

Discovery of the catechol structural moiety as a Stat3 SH2 domain inhibitor by virtual screening.

The Stat3 SH2 domain is essential for its activation, and development of a potent SH2 inhibitor will be therapeutically valuable in treating cancers with constant Stat3 activation. We report here the identification of the catechol (1,2-dihydroxybenzene) structural moiety by virtual screening as a Stat3 SH2 inhibitor. The catechol compound docked to the Stat3 SH2 domain in computer modeling forms hydrogen bonds with the conserved pTyr-interacting amino acids. In the biochemical assay, a catechol-containing compound, but not the hydroxyl group-acetalized analogue, was able to inhibit Stat3 DNA-binding activity. Furthermore, the catechol compound was demonstrated to compete with pTyr peptides in binding to the Stat3 SH2 domain, suggesting that the catechol moiety is a pTyr bioisostere and may potentially be used for designing cell-permeable SH2 inhibitors. In our preliminary effort, we also demonstrated that the potency of catechol compound as Stat3 SH2 inhibitors could be improved by modifying the non-catechol part of the compound structure.

FAM83 family oncogenes are broadly involved in human cancers: an integrative multi-omics approach.

The development of novel targeted therapies for cancer treatment requires identification of reliable targets. FAM83 ('family with sequence similarity 83') family members A, B, and D were shown recently to have oncogenic potential. However, the overall oncogenic abilities of FAM83 family genes remain largely unknown. Here, we used a systematic and integrative genomics approach to investigate oncogenic properties of the entire FAM83 family members. We assessed transcriptional expression patterns of eight FAM83 family genes (FAM83A-H) across tumor types, the relationship between their expression and changes in DNA copy number, and the association with patient survival. By comparing the gene expression levels of FAM83 family members in cancers from 17 different tumor types with those in their corresponding normal tissues, we identified consistent upregulation of FAM83D and FAM83H across the majority of tumor types, which is largely driven by increased DNA copy number. Importantly, we found also that a higher expression level of a signature of FAM83 family members was associated with poor prognosis in a number of human cancers. In breast cancer, we found that alterations in FAM83 family genes correlated significantly with TP53 mutation, whereas significant, but inverse correlation was observed with PIK3CA and CDH1 (E-cadherin) mutations. We also identified that expression levels of 55 proteins were significantly associated with alterations in FAM83 family genes including a decrease in GATA3, ESR1, and PGR proteins in tumors with alterations in FAM83. Our results provide strong evidence for a critical role of FAM83 family genes in tumor development, with possible relevance for therapeutic target development.

Phaeosphaeride A, an inhibitor of STAT3-dependent signaling isolated from an endophytic fungus.

Phaeosphaeride A, a nitrogen-containing bicyclic compound produced by an endophytic fungus, inhibits signaling by the transcription factor STAT3.

Inhibition of the signal transducer and activator of transcription-3 (STAT3) signaling pathway by 4-oxo-1-phenyl-1,4-dihydroquinoline-3-carboxylic acid esters.

The JAK-STAT3 pathway regulates genes that are important in cell proliferation and thus is a promising target for cancer therapy. A high-throughput screening (HTS) campaign using an Apo-ONE Homogenous Caspase 3/7 assay in U266 cells identified 4-oxo-1-phenyl-1,4-dihydroquinoline-3-carboxylic acid ethyl ester 4 as a potential STAT3 pathway inhibitor. Optimization of this HTS hit led to the identification of the 7-cyano analogue 8, which inhibited STAT3-Y705 phosphorylation with an EC 50 of 170 nM. Compound 8 also inhibited cytokine induced JAK activation but did not inhibit BCR-ABL activated STAT5 phosphorylation in K562 cells.