Induction of apoptosis by 3-amino-6-(3-aminopropyl)-5,6-dihydro-5,11-dioxo-11H-indeno[1,2-c]isoquinoline via modulation of MAPKs (p38 and c-Jun N-terminal kinase) and c-Myc in HL-60 human leukemia cells

Natural and synthetic retinoid X receptor ligands and their role in selected nuclear receptor action

Important key players in the regulatory machinery within the cells are nuclear retinoid X receptors (RXRs), which compose heterodimers in company with several diverse nuclear receptors, playing a role as ligand inducible transcription factors. In general, nuclear receptors are ligand-activated, transcription-modulating proteins affecting transcriptional responses in target genes. RXR molecules forming permissive heterodimers with disparate nuclear receptors comprise peroxisome proliferator-activated receptors (PPARs), liver X receptors (LXRs), farnesoid X receptor (FXR), pregnane X receptor (PXR) and constitutive androstan receptor (CAR). Retinoid receptors (RARs) and thyroid hormone receptors (TRs) may form conditional heterodimers, and dihydroxyvitamin D₃ receptor (VDR) is believed to form nonpermissive heterodimer. Thus, RXRs are the important molecules that are involved in control of many cellular functions in biological processes and diseases, including cancer or diabetes. This article summarizes both naturally occurring and synthetic ligands for nuclear retinoid X receptors and describes, predominantly in mammals, their role in molecular mechanisms within the cells. A focus is also on triorganotin compounds, which are high affinity RXR ligands, and finally, we present an outlook on human microbiota as a potential source of RXR activators. Nevertheless, new synthetic rexinoids with better retinoid X receptor activity and lesser side effects are highly required.

A review of the molecular design and biological activities of RXR agonists

An attractive approach to combat disease is to target theregulation of cell function. At the heart of this task are nuclear receptors (NRs); which control functions such as gene transcription. Arguably, the key player in this regulatory machinery is the retinoid X receptor (RXR). This NR associates with a third of the NRs found in humans. Scientists have hypothesized that controlling the activity of RXR is an attractive approach to control cellular functions that modulate diseases such as cancer, diabetes, Alzheimer's disease and Parkinson's disease. In this review, we will describe the key features of the RXR, present a historic perspective of the first RXR agonists, and discuss various templates that have been reported to activate RXR with a focus on their molecular structure, biological activity, and limitations. Finally, we will present an outlook of the field and future directions and considerations to synthesize or modulate RXR agonists to make these compounds a clinical reality.

Research on the effect of ginseng polysaccharide on apoptosis and cell cycle of human leukemia cell line K562 and its molecular mechanisms

Ginseng polysaccharide (GPS), a polymer of glucose and the primary constituent extracted from panax ginseng, has been documented to exert various pharmacological properties, including anti-tumor properties. To provide further insights into the anti-tumor functions of GPS, the present study was designed to investigate the effect of GPS on apoptosis and the cell cycle of human leukemia cell line K562 cells, and its underlying mechanisms. The results demonstrated that GPS could inhibit K562 cell proliferation and induce apoptosis in vitro in a concentration- and time-dependent manner. The transcription of P38 and c-Jun NH2-terminal kinase (JNK) mRNA were significantly augmented, while the transcription of extracellular signal-regulated kinase (ERK) mRNA were significantly reduced following treatment with GPS compared with the control group (all P<0.05). In addition, GPS treatment markedly suppressed the expression of phosphorylated (p)-ERK, nuclear factor (NF)-κB p65 and cyclin D1, and increased the synthesis of p-P38 and p-JNK protein expression, as evidenced by immunofluorescence and western blotting analyses. In conclusion, the results indicate that the GPS-mediated MAPK/NF-κB/cyclin D1 signaling pathway serves a crucial role in cell cycle arrest and apoptosis of K562 cells.

(E)-2,4-bis(p-hydroxyphenyl)-2-butenal has an antiproliferative effect on NSCLC cells induced by p38 MAPK-mediated suppression of NF-κB and up-regulation of TNFRSF10B (DR5)

BACKGROUND AND PURPOSE

The Maillard Reaction Products (MRPs) are known to be effective in chemoprevention. Here we focused on the anticancer effects of (E)-2,4-bis(p-hydroxyphenyl)-2-butenal (a MRP) on human non-small-cell lung cancer (NSCLC) cells and its mechanism of action.

EXPERIMENTAL APPROACH

We analysed the activity of (E)-2,4-bis(p-hydroxyphenyl)-2-butenal on NSCLC cells (NCI-H460 and A549) by use of Western blot analysis for major apoptotic proteins, MAPK, NF-κB and death receptor expression. We also used RT-PCR to determine its effects on death receptor mRNA expression, EMSA for effects on NF-κB DNA binding activity and colony formation assay for effects of inhibitors on (E)-2,4-bis(p-hydroxyphenyl)-2-butenal's actions.

KEY RESULTS

(E)-2,4-bis(p-hydroxyphenyl)-2-butenal induced a concentration (10-40 μg·mL⁻¹)- and time (30 min-72 h)-dependent inhibitory effect on the growth of NSCLC cells due to induction of apoptosis. Concomitantly, it significantly increased the expression of apoptotic proteins such as cleaved caspase-3, cleaved caspase-9, Bax and p53, but down-regulated the expression of anti-apoptotic proteins Bcl-2, cIAP1 and cIAP2. This effect was induced by up-regulation of MAPK and death receptor proteins TNFRSF12, TNFRSF10B and TNFRSF21, but suppression of NF-κB. Of the death receptors activated, only TNFRSF10B knock down with siRNA reversed the effect of (E)-2,4-bis(p-hydroxyphenyl)-2-butenal. Even though all the MAPKs were activated, only pretreatment with a p38 MAPK inhibitor reversed (E)-2,4-bis(p-hydroxyphenyl)-2-butenal-induced cell growth inhibition, increase in cleaved caspase-3, -9 and TNFRSF10B expression, and NF-κB inactivation.

CONCLUSIONS AND IMPLICATIONS

(E)-2,4-bis(p-hydroxyphenyl)-2-butenal induces apoptosis in NSCLC cells by p38 MAPK-mediated suppression of NF-κB and activation of TNFRSF10B, which then activates the caspase-3 and caspase-9 pathways.

PINCH expression in relation to radiation response in co-cultured colon cancer cells and in rectal cancer patients

Particularly interesting new cysteine-histidine rich protein (PINCH), involved in cell spreading, motility and proliferation, has been shown to enhance radioresistance in colon cancer cell lines. The expression of PINCH in relation to radiation was studied in co-cultured colon cancer cells. Furthermore, the clinical significance between PINCH and radiotherapy (RT) was analyzed in rectal cancer patients with or without RT. The relative PINCH expression in colon cancer (KM12C) cells cultured separately and in co-culture was examined by western blotting and real-time PCR, and was analyzed over a period of 8 and 24 h after radiation. PINCH expression was immunohistochemically examined in 137 primary rectal tumors for which 65 cases did not receive RT and 72 cases received RT. PINCH expression tended to decrease from that in the separately cultured KM12C cells without radiation to that in cells with radiation at 8 h (P=0.060); while in the co-cultured cells, no significant difference was found (P=0.446). In patients with RT, strong PINCH expression was related to worse survival, when compared to patients with weak expression, independent of TNM stage, degree of differentiation, age and p53 status (P=0.029, RR 4.03, 95% CI 1.34‑12.1). No survival relationship for the patients without RT was observed (P=0.287). A statistical interaction analysis between PINCH, RT and survival showed a trend towards significance (P=0.057). In conclusion, PINCH predicts survival in rectal cancer patients with RT, but not in patients without RT. The expression of PINCH may be regulated by radiation and by environmental factors surrounding the cells.

Skeletal muscle PGC-1α controls whole-body lactate homeostasis through estrogen-related receptor α-dependent activation of LDH B and repression of LDH A

The peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) controls metabolic adaptations. We now show that PGC-1α in skeletal muscle drives the expression of lactate dehydrogenase (LDH) B in an estrogen-related receptor-α-dependent manner. Concomitantly, PGC-1α reduces the expression of LDH A and one of its regulators, the transcription factor myelocytomatosis oncogene. PGC-1α thereby coordinately alters the composition of the LDH complex and prevents the increase in blood lactate during exercise. Our results show how PGC-1α actively coordinates lactate homeostasis and provide a unique molecular explanation for PGC-1α-mediated muscle adaptations to training that ultimately enhance exercise performance and improve metabolic health.

Synthesis and biological evaluation of indenoisoquinolines that inhibit both tyrosyl-DNA phosphodiesterase I (Tdp1) and topoisomerase I (Top1)

Tyrosyl-DNA phosphodiesterase I (Tdp1) plays a key role in the repair of damaged DNA resulting from the topoisomerase I (Top1) inhibitor camptothecin and a variety of other DNA-damaging anticancer agents. This report documents the design, synthesis, and evaluation of new indenoisoquinolines that are dual inhibitors of both Tdp1 and Top1. Enzyme inhibitory data and cytotoxicity data from human cancer cell cultures were used to establish structure-activity relationships. The potencies of the indenoisoquinolines against Tdp1 ranged from 5 μM to 111 μM, which places the more active compounds among the most potent known inhibitors of this target. The cytotoxicity mean graph midpoints ranged from 0.02 to 2.34 μM. Dual Tdp1-Top1 inhibitors are of interest because the Top1 and Tdp1 inhibitory activities could theoretically work synergistically to create more effective anticancer agents.