MK5 is degraded in response to doxorubicin and negatively regulates doxorubicin-induced apoptosis in hepatocellular carcinoma cells

TLK1-mediated MK5-S354 phosphorylation drives prostate cancer cell motility and may signify distinct pathologies

Metastases account for the majority of prostate cancer (PCa) deaths, and targeting them is a major goal of systemic therapy. We identified a novel interaction between two kinases: tousled‐like kinase 1 (TLK1) and MAP kinase‐activated protein kinase 5 (MK5) that promotes PCa spread. In PCa progression, TLK1–MK5 signalling appears to increase following antiandrogen treatment and in metastatic castration‐resistant prostate cancer (mCRPC) patients. Determinations of motility rates (2D and 3D) of different TLK1‐ and MK5‐perturbed cells, including knockout (KO) and knockdown (KD), as well as the use of specific inhibitors, showed the importance of these two proteins for in vitro dissemination. We established that TLK1 phosphorylates MK5 on three residues (S160, S354 and S386), resulting in MK5 activation, and additionally, mobility shifts of MK5 also supported its phosphorylation by TLK1 in transfected HEK 293 cells. Expression of MK5‐S354A or kinase‐dead MK5 in MK5‐depleted mouse embryonic fibroblast (MEF) cells failed to restore their motility compared with that of wild‐type (WT) MK5‐rescued MK5^−/− MEF cells. A pMK5‐S354 antiserum was used to establish this site as an authentic TLK1 target in androgen‐sensitive human prostate adenocarcinoma (LNCaP) cells, and was used in immunohistochemistry (IHC) studies of age‐related PCa sections from TRAMP (transgenic adenocarcinoma of the mouse prostate) mice and to probe a human tissue microarray (TMA), which revealed pMK5‐S354 level is correlated with disease progression (Gleason score and nodal metastases). In addition, The Cancer Genome Atlas (TCGA) analyses of PCa expression and genome‐wide association study (GWAS) relations identify TLK1 and MK5 as potential drivers of advanced PCa and as markers of mCRPC. Our work suggests that TLK1–MK5 signalling is functionally involved in driving PCa cell motility and clinical features of aggressiveness; hence, disruption of this axis may inhibit the metastatic spread of PCa.

Neuroprotection by B355252 against Glutamate-Induced Cytotoxicity in Murine Hippocampal HT-22 Cells Is Associated with Activation of ERK3 Signaling Pathway

Glutamate differentially affects the levels extracellular signal-regulated kinase (ERK)1/2 and ERK3 and the protective effect of B355252, an aryl thiophene compound, 4-chloro-N-(naphthalen-1-ylmethyl)-5-(3-(piperazin-1-yl)phenoxy)thiophene-2-sulfonamide, is associated with suppression of ERK1/2. The objectives of this study were to further investigate the impact of B355252 on ERK3 and its downstream signaling pathways affected by glutamate exposure in the mouse hippocampal HT-22 neuronal cells. Murine hippocampal HT22 cells were incubated with glutamate and treated with B355252. Cell viability was assessed, protein levels of pERK3, ERK3, mitogen-activated protein kinase-activated protein kinase-5 (MAPKAPK-5), steroid receptor coactivator 3 (SRC-3), p-S6 and S6 were measured using Western blotting, and immunoreactivity of p-S6 was determined by immunocytochemistry. The results reveal that glutamate markedly diminished the protein levels of p-ERK3 and its downstream targets MK-5 and SRC-3 and increased p-S6, an indicator for mechanistic target of rapamycin (mTOR) activation. Conversely, treatment with B355252 protected the cells from glutamate-induced damage and prevented the glutamate-caused declines of p-ERK3, MK-5 and SRC-3 and increase of p-S6. Our study demonstrates that one of the mechanisms that glutamate mediates its cytotoxicity is through suppression of ERK3 and that B355252 rescues the cells from glutamate toxicity by reverting ERK3 level.

A genome-wide association study in the Japanese population identifies the 12q24 locus for habitual coffee consumption: The J-MICC Study

Coffee is one of the most widely consumed beverages worldwide, and its role in human health has received much attention. Although genome-wide association studies (GWASs) have investigated genetic variants associated with coffee consumption in European populations, no such study has yet been conducted in an Asian population. Here, we conducted a GWAS to identify common genetic variations that affected coffee consumption in a Japanese population of 11,261 participants recruited as a part of the Japan Multi-Institutional Collaborative Cohort (J-MICC) study. Coffee consumption was collected using a self-administered questionnaire, and converted from categories to cups/day. In the discovery stage (n = 6,312), we found 2 independent loci (12q24.12–13 and 5q33.3) that met suggestive significance (P < 1 × 10⁻⁶). In the replication stage (n = 4,949), the lead variant for the 12q24.12–13 locus (rs2074356) was significantly associated with habitual coffee consumption (P = 2.2 × 10⁻⁶), whereas the lead variant for the 5q33.3 locus (rs1957553) was not (P = 0.53). A meta-analysis of the discovery and replication populations, and the combined analysis using all subjects, revealed that rs2074356 achieved genome-wide significance (P = 2.2 × 10⁻¹⁶ for a meta-analysis). These findings indicate that the 12q24.12-13 locus is associated with coffee consumption among a Japanese population.

Protective effects of curcumin against doxorubicin-induced toxicity and resistance: A review

Doxorubicin (DOX)-induced toxicity and resistance are major obstacles in chemotherapeutic approaches. Despite effective in the treatment of numerous malignancies, some clinicians have voiced concern that DOX has the potential to cause debilitating consequences in organ tissues, especially the heart. The mechanisms of toxicity and resistance are respectively related to induction of reactive oxygen species (ROS) and up-regulation of ATP-binding cassette (ABC) transporter. Curcumin (CUR) with several biological and pharmacological properties is expected to restore DOX-mediated impairments to tissues. This review is intended to address the current knowledge on DOX adverse effects and CUR protective actions in the heart, kidneys, liver, brain, and reproductive organs. Coadministration of CUR and DOX is capable of ameliorating DOX toxicity pertained to antioxidant, apoptosis, autophagy, and mitochondrial permeability.

p38 MAPK-MK2 pathway regulates the heat-stress-induced accumulation of reactive oxygen species that mediates apoptotic cell death in glial cells

Previous studies have demonstratedf that heat stress can induce injury of the central nervous system and lead to neuronal cell apoptosis. However, the molecular mechanisms underlying these cellular changes remain unclear. In the present study, flow cytometry was used to investigate heat-stress-induced apoptosis, and caspase-3 activation was also assessed in neurons. The role of reactive oxygen species (ROS) accumulation in the heat-stress-induced apoptosis of neurons was demonstrated using the antioxidant drug manganese (III) tetrakis (4-benzoic acid)porphyrin. The present study presents evidence that heat stress induces mitogen-activated protein kinase (MAPK) activation in rat malignant glioma F98 cells. Following the inhibition of different MAPKs with a range of specific inhibitors, SB203580 (an inhibitor of p38 MAPK), but not PD98059 (an inhibitor of extracellular signal-regulated kinases) or SP600125 (an inhibitor of c-Jun N-terminal kinases), diminished the production of ROS and apoptosis, and prevented activation of the p38-downstream kinase MAPK-activated protein kinase 2 (MK2) in neurons. Inhibiting MK2 with dominant negative adenoviral constructs or a specific inhibitor significantly decreased normal and heat-stress-induced ROS accumulation and cell apoptosis, whereas inhibition of another kinase downstream of p38 MAPK, MAPK-activated protein kinase 5, by transfection with another adenoviral construct did not exert the same effects. Taken together, these findings indicate that heat stress stimulation induces p38-MK2 pathway activation, which exerts a pro-apoptotic effect by regulating ROS accumulation in neurons.

Valproic Acid Induces Endocytosis-Mediated Doxorubicin Internalization and Shows Synergistic Cytotoxic Effects in Hepatocellular Carcinoma Cells

Valproic acid (VPA), a well-known histone deacetylase (HDAC) inhibitor, is used as an anti-cancer drug for various cancers, but the synergistic anti-cancer effect of VPA and doxorubicin (DOX) combination treatment and its potential underlying mechanism in hepatocellular carcinoma (HCC) remain to be elucidated. Here, we evaluate the mono- and combination-therapy effects of VPA and DOX in HCC and identify a specific and efficient, synergistic anti-proliferative effect of the VPA and DOX combination in HCC cells, especially HepG2 cells; this effect was not apparent in MIHA cells, a normal hepatocyte cell line. The calculation of the coefficient of drug interaction confirmed the significant synergistic effect of the combination treatment. Concurrently, the synergistic apoptotic cell death caused by the VPA and DOX combination treatment was confirmed by Hoechst nuclear staining and Western blot analysis of caspase-3 and poly (ADP-ribose) polymerase (PARP) activation. Co-treatment with VPA and DOX enhanced reactive oxygen species (ROS) generation and autophagy, which were clearly attenuated by ROS and autophagy inhibitors, respectively. Furthermore, as an indication of the mechanism underlying the synergistic effect, we observed that DOX internalization, which was induced in the VPA and DOX combination-treated group, occurred via by the caveolae-mediated endocytosis pathway. Taken together, our study uncovered the potential effect of the VPA and DOX combination treatment with regard to cell death, including induction of cellular ROS, autophagy, and the caveolae-mediated endocytosis pathway. Therefore, these results present novel implications in drug delivery research for the treatment of HCC.

Mechanisms of doxorubicin resistance in hepatocellular carcinoma

Hepatocellular carcinoma, one of the most common solid tumors worldwide, is poorly responsive to available chemotherapeutic approaches. While systemic chemotherapy is of limited benefit, intra-arterial delivery of doxorubicin to the tumor frequently produces tumor shrinkage. Its utility is limited, in part, by the frequent emergence of doxorubicin resistance. The mechanisms of this resistance include increased expression of multidrug resistance efflux pumps, alterations of the drug target, topoisomerase, and modulation of programmed cell death pathways. Many of these effects result from changes in miRNA expression and are particularly prominent in tumor cells with a stem cell phenotype. This review will summarize the current knowledge on the mechanisms of doxorubicin resistance of hepatocellular carcinoma and the potential for approaches toward therapeutic chemosensitization.

CD166 positively regulates MCAM via inhibition to ubiquitin E3 ligases Smurf1 and βTrCP through PI3K/AKT and c-Raf/MEK/ERK signaling in Bel-7402 hepatocellular carcinoma cells

Both Cluster of Differentiation 166 (CD166) and Melanoma Cell Adhesion Molecule (MCAM) play critical roles in maintaining transformative phenotype of Hepatocellular Carcinoma (HCC) cells. However, the relationship between these two membrane proteins remains unknown. Here, we found that CD166 has a positive impact on the expression of MCAM, while MCAM has no feedback on CD166. Tissue microarray analysis (TMA) also showed a positive correlation between CD166 and MCAM. Depletion of CD166-induced anti-carcinogenic phenotype could be reversed by overexpression of MCAM, suggesting MCAM is functional important in the CD166-induced liver tumorigenesis. Furthermore, we found CD166 regulates MCAM mainly through protecting MCAM from ubiquitin-mediated protein degradation. Mechanically, CD166 down-regulated two ubiquitin E3 ligases, βTrCP and Smurf1, which play critical roles in the destability of MCAM protein. In addition, overexpression of βTrCP and Smurf1-reduced transformative phenotype could be partially reversed by MCAM, providing evidence that MCAM is a target of βTrCP and Smurf1. Moreover, we identified c-Raf/MEK/ERK signaling acts as a downstream effecter of CD166/PI3K/AKT axis to stimulate ubiquitination and destability of βTrCP and Smurf1. Taken together, we establish a model that CD166 regulates MCAM through a signaling flow from activation of PI3K/AKT and c-Raf/MEK/ERK signaling to the inhibition of potential MCAM ubiquitin E3 ligases, βTrCP and Smurf1, blockage of this signaling cascade may be useful in the treatment of CD166 and MCAM-dependent HCC.