MHY-449, a novel dihydrobenzofuro[4,5-b][1,8] naphthyridin-6-one derivative, induces apoptotic cell death through modulation of Akt/FoxO1 and ERK signaling in PC3 human prostate cancer cells

ERK: A Double-Edged Sword in Cancer. ERK-Dependent Apoptosis as a Potential Therapeutic Strategy for Cancer

The RAF/MEK/ERK signaling pathway regulates diverse cellular processes as exemplified by cell proliferation, differentiation, motility, and survival. Activation of ERK1/2 generally promotes cell proliferation, and its deregulated activity is a hallmark of many cancers. Therefore, components and regulators of the ERK pathway are considered potential therapeutic targets for cancer, and inhibitors of this pathway, including some MEK and BRAF inhibitors, are already being used in the clinic. Notably, ERK1/2 kinases also have pro-apoptotic functions under certain conditions and enhanced ERK1/2 signaling can cause tumor cell death. Although the repertoire of the compounds which mediate ERK activation and apoptosis is expanding, and various anti-cancer compounds induce ERK activation while exerting their anti-proliferative effects, the mechanisms underlying ERK1/2-mediated cell death are still vague. Recent studies highlight the importance of dual-specificity phosphatases (DUSPs) in determining the pro- versus anti-apoptotic function of ERK in cancer. In this review, we will summarize the recent major findings in understanding the role of ERK in apoptosis, focusing on the major compounds mediating ERK-dependent apoptosis. Studies that further define the molecular targets of these compounds relevant to cell death will be essential to harnessing these compounds for developing effective cancer treatments.

1,8-Naphthyridine Derivatives: A Privileged Scaffold for Versatile Biological Activities

1, 8- Naphthyridine nucleus belongs to significant nitrogen-containing heterocyclic compounds which has garnered the interest of researchers due to its versatile biological activities. It is known to be used as an antimicrobial, anti-psychotic, anti-depressant, anti-convulsant, anti- Alzheimer's, anti-cancer, analgesic, anti-inflammatory, antioxidant, anti-viral, anti-hypertensive, antimalarial, pesticides, anti-platelets, and CB2 receptor agonist, etc. The present review highlights the framework of biological properties of synthesized 1, 8-naphthyridine derivatives developed by various research groups across the globe.

Targeting the PLK1-FOXO1 pathway as a novel therapeutic approach for treating advanced prostate cancer

The forkhead box protein O1 (FOXO1) is considered to be a key tumor suppressor due to its involvement in a broad range of cancer-related functions, including cellular differentiation, apoptosis, cell cycle arrest, and DNA damage. Given that inactivation of FOXO1 has been reported in many types of human cancer, we sought to investigate whether restoration of the pro-apoptotic activity of FOXO1 may be used as a new promising strategy for cancer treatment. Our previous study revealed that Polo-like kinase 1 (PLK1), a serine/threonine kinase that is essential for cell cycle progression, is a novel and major regulator of FOXO1 in the late phases of the cell cycle. Here, we provided evidence that PLK1-dependent phosphorylation of FOXO1 induces its nuclear exclusion and negatively regulates FOXO1's transcriptional activity in prostate cancer (PCa). Blocking the PLK1-dependant phosphorylation of FOXO1 restored the pro-apoptotic function of FOXO1 in PCa. Combining PLK1 inhibition with nocodazole (to induce mitotic arrest) had synergistic antitumor effects in vitro, with minimal effect on normal prostate epithelial cells. These findings shed light on a novel approach to reactivate apoptotic pathways in advanced PCa and support targeting PLK1-FOXO1 pathways as a novel approach for treating advanced PCa.

Pro-apoptotic effect of the novel benzylidene derivative MHY695 in human colon cancer cells

The induction of apoptosis is a useful strategy in anti-cancer research. Various Moon Hyung Yang (MHY) compounds have been developed as novel anti-cancer drug candidates; in the present study, the pro-apoptotic effects of (Z)-5-(3-ethoxy-4- hydroxybenzylidene)-2-thioxothiazolidin-4-one (MHY695) on HCT116 human colon cancer cells were assessed. MTT assays were performed to investigate the dose-dependent cytotoxic effects of MHY695 on HCT116 cells. Immunofluorescence staining and flow cytometry analyses were performed to identify apoptotic cell death, and western blot analysis was used to investigate the apoptotic-signaling pathways. A mouse xenograft model was also used to determine the effects of MHY695 in vivo. MHY695 decreased the viability of HCT116 cells and induced apoptotic cytotoxicity. The apoptotic mechanisms induced by MHY695 involved the dephosphorylation of Bcl-2-associated agonist of cell death protein following protein kinase B inactivation, induced myeloid leukaemia cell differentiation protein and BH3-interacting domain death agonist truncation, caspase-3 and -9 activation and poly (ADP-ribose) polymerase cleavage. In addition, MHY695 significantly suppressed tumor growth in the mouse xenograft model, compared with the vehicle control. Notably, MHY695 exhibited potent anti-cancer effects in four different types of human colon cancer cell line, including Caco-2, DLD-1, HT-29 and HCT116. Additionally, MHY695 showed reduced cytotoxicity in NCM460, normal colonic epithelial cells. Furthermore, MHY-induced cytotoxicity in colon cancer cells was independent of the tumor suppressor protein p53. Collectively, these observations suggested that MHY695 may be a novel drug for the treatment of colon cancer.

CTCF regulates the FoxO signaling pathway to affect the progression of prostate cancer

The present research focuses on the influence of CCCTC‐binding factor (CTCF) on prostate cancer (PC) via the regulation of the FoxO signalling pathway. A bioinformatics analysis was conducted to screen out target genes for CTCF in LNCaP cells and to enrich the relevant pathways in LNCaP cells. It was found that the FoxO pathway was enriched according to the ChIP‐seq results of CTCF. The expression of CTCF, pFoxO1a, FoxO1a, pFoxO3a and FoxO3a was tested by RT‐qPCR and Western blot. Inhibition of CTCF could lead to the up‐regulation of the FoxO signalling pathway. The rates of cell proliferation, cell invasion and apoptosis were examined by MTT assay, cell invasion assay and flow cytometry under different interference conditions. Down‐regulation of CTCF could suppress cell proliferation, cell invasion and facilitate cell apoptosis. Lastly, the effect of CTCF on tumour growth was determined in nude mice. Inhibition of CTCF regulated the FoxO signalling pathway, which retarded tumour growth in vivo. In conclusion, CTCF regulates the FoxO signalling pathway to affect the progress of PC.

Deciphering the roles of FOXO1 in human neoplasms

Neoplasms constituted an enormous burden and contributed to an estimated 8.2 million deaths in 2012 worldwide. FOXO1 (forkhead box O1), a member of the forkhead box (FOX) family, is a transcriptional factor involved in diverse cellular functions. Herein, we concentrate on recent studies of the antineoplastic roles of FOXO1 in neoplasms. This article may serve as a guide for future research and identify FOXO1 as a potent therapeutic target in neoplasms.

Synthesis of pyrrolo[1,2-a]naphthyridines by Lewis acid mediated cycloisomerization

Functionalized pyrrolo[1,2-a]naphthyridines were synthesized by application of PtCl₂ and Bi(OTf)₃ as simple Lewis acids in a cycloisomerization reaction.

MHY-449, a novel dihydrobenzofuro[4,5-b][1,8]naphthyridin-6-one derivative, mediates oxidative stress-induced apoptosis in AGS human gastric cancer cells

MHY-449 is a novel dihydrobenzofuro[4,5-b][1,8]naphthyridin-6-one derivative designed and synthesized as a potential anticancer agent. The present study aimed to examine the anticancer activity and underlying mechanism of MHY-449. The cell viability assay performed in AGS human gastric carcinoma cells demonstrated that MHY-449 inhibited cell proliferation in a concentration-dependent manner. MHY-449 induced AGS cell death via apoptosis. The underlying molecular mechanism of MHY-449-mediated apoptosis was also investigated. MHY-449 promoted the upregulation of Fas and Fas-ligand, and activation of caspase-8, suggesting the involvement of a Fas-mediated extrinsic pathway in MHY-449-induced apoptosis. In addition, it was found that MHY-449-induced apoptosis was accompanied by the upregulation of Bax, p21(WAF1/CIP1), p27(KIP1), and p53 and suppression of Bcl-2. MHY-449 exposure activated the caspase cascade and subsequent poly(ADP-ribose) polymerase (PARP) cleavage. Furthermore, the pan-caspase inhibitor, Z-VAD-FMK, significantly attenuated MHY-449-induced apoptosis, indicating that the apoptosis was caspase-dependent. Moreover, the apoptogenic effect of MHY-449 was reactive oxygen species (ROS)-dependent. This result was confirmed by the induction of ROS by MHY-449 and by evidence that the scavenging of ROS by N-acetyl-L-cysteine inhibited MHY-449-induced cell death. Taken together, these results demonstrated that MHY-449 triggers apoptosis via caspase activation and ROS production. This result provides a novel mechanistic explanation and a basis for developing this compound as a novel candidate for human cancer therapy.

The natural compound Guttiferone F sensitizes prostate cancer to starvation induced apoptosis via calcium and JNK elevation

BACKGROUND

In a cytotoxicity screen in serum-free medium, Guttiferone F showed strong growth inhibitory effect against prostate cancer cells.

METHODS

Prostate cancer cells LNCaP and PC3 were treated with Guttiferone F in serum depleted medium. Sub-G1 phase distributions were estimated with flow cytometry. Mitochondrial disruption was observed under confocal microscope using Mitotracker Red staining. Gene and protein expression changes were detected by real-time PCR and Western blotting. Ca(2+) elevation was examined by Fluo-4 staining under fluorescence microscope. PC3 xenografts in mice were examined by immunohistochemical analysis.

RESULTS

Guttiferone F had strong growth inhibitory effect against prostate cancer cell lines under serum starvation. It induced a significant increase in sub-G1 fraction and DNA fragmentation. In serum-free medium, Guttiferone F triggered mitochondria dependent apoptosis by regulating Bcl-2 family proteins. In addition, Guttiferone F attenuated the androgen receptor expression and phosphorylation of ERK1/2, while activating the phosphorylation of JNK and Ca(2+) flux. Combination of caloric restriction with Guttiferone F in vivo could increase the antitumor effect without causing toxicity.

CONCLUSIONS

Guttiferone F induced prostate cancer cell apoptosis under serum starvation via Ca(2+) elevation and JNK activation. Combined with caloric restriction, Guttiferone F exerted significant growth inhibition of PC3 cells xenograft in vivo. Guttiferone F is therefore a potential anti-cancer compound.

Long‑term exposure to leptin enhances the growth of prostate cancer cells

Obesity correlates with an increased risk of developing prostate cancer (PCa) and leptin plays an important role in PCa progression. Since leptin is produced by adipocytes, the serum leptin level is higher in obese than in non-obese individuals. However, the effects of leptin remain controversial and unclear. The aim of the present study was to investigate the effect of leptin on PCa cell aggressiveness. Three human PCa cell lines (LNCaP, DU145 and PC-3) were treated with recombinant leptin for 28 days. Cell proliferation, migration, and invasion were estimated using the WST assay, a wound-healing assay, and a BD Matrigel invasion assay, respectively. The mechanism underlying the proliferative effect of leptin was investigated by cell transfections with small interfering RNA (siRNA) against the leptin receptor (ObR) or forkhead box O1 (FOXO1), and by immunocytochemistry. Long-term exposure of PCa cells to leptin enhanced their proliferation, migration and invasion. Leptin increased ObR expression and enhanced Akt phosphorylation constitutively. Leptin also increased the phosphorylation of FOXO1 via PI3K signaling and FOXO1 gene silencing enhanced PCa cell proliferation. Leptin induced the translocation of FOXO1 from the nucleus to the cytoplasm. Furthermore, the PI3K inhibitor, LY294002 suppressed this translocation. These results suggested that leptin regulated the subcellular localization of FOXO1 and induced Akt phosphorylation. Additionally, we revealed that leptin increased the expression of cyclin D1 and decreased the expression of p21 protein. In conclusion, long-term exposure to leptin increased the cell proliferation, migration, and invasion of PCa cells through inactivation of FOXO1. This inactivation resulted from exclusion of FOXO1 from the nucleus and its restriction to the cytoplasm through PI3K/Akt signaling. Our findings contribute to an understanding of the association between obesity and PCa aggressiveness.