Phytochemicals as Emerging Antiproliferative Agents in Head and Neck Cancer: Molecular Mechanisms and Therapeutic Strategies

Epidermal growth factor (EGF) receptor (EGFR) signal transduction is organized by scaffold and adaptor proteins, which have specific subcellular distribution. On a way from the plasma membrane to the lysosome EGFRs are still in their active state and can signal from distinct subcellular locations. To identify organelle-specific targets of EGF receptor signaling on endosomes a combination of subcellular fractionation, two-dimensional DIGE, fluorescence labeling of phosphoproteins, and MALDI-TOF/TOF mass spectrometry was applied. All together 23 EGF-regulated (phospho)proteins were identified as being differentially associated with endosomal fractions by functional organelle proteomics; among them were proteins known to be involved in endosomal trafficking and cytoskeleton rearrangement (Alix, myosin-9, myosin regulatory light chain, Trap1, moesin, cytokeratin 8, septins 2 and 11, and CapZbeta). Interestingly R-Ras, a small GTPase of the Ras family that regulates cell survival and integrin activity, was associated with endosomes in a ligand-dependent manner. EGF-dependent association of R-Ras with late endosomes was confirmed by confocal laser scanning immunofluorescence microscopy and Western blotting of endosomal fractions. EGFR tyrosine kinase inhibitor gefitinib was used to confirm EGF-dependent regulation of all identified proteins. EGF-dependent association of signaling molecules, such as R-Ras, with late endosomes suggests signaling specification through intracellular organelles.

Prevalent mutations in the mitogen-activated protein kinase 1 (MAPK1)/extracellular signal-regulated kinase 2 (ERK2) pathway have been identified in cervical squamous cell carcinoma in a large-scale genome sequencing effort. Furthermore, mutations in the rat sarcoma viral oncogene homolog (RAS)/Raf/Mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway have also been revealed to have important roles in the pathogenesis of human cancer. However, whether the potential hotspot mutations in ERK2 and other components of the RAS/RAF/MEK/ERK signaling pathway also exist in Chinese patients with cervical carcinoma remains to be elucidated. In the present study, a total of 260 patients with cervical carcinoma of distinct subtypes were analyzed for the presence of potential hotspot mutations in the RAS/RAF/MEK/ERK signaling pathway. No ERK2 mutations were detected in these samples; however, Kirsten RAS (KRAS) p.G12D (c.35G>A) mutation was identified in 2/26 (7.7%) cervical adenocarcinoma cases, including 1/20 cervical mucinous adenocarcinoma and 1/6 cervical endometrioid carcinoma cases. In addition, no mutations in the ERK1, neuroblastoma RAS, Harvey RAS or B-Raf proto-oncogene serine/threonine kinase genes were detected in the present study. These results indicated that ethnic differences may be a primary reason for the discrepancy in ERK2 mutation frequencies between the current study and previous studies. Furthermore, mutation in the KRAS gene, but not other genes in the RAS/RAF/MEK/ERK signaling pathway, may have an active role in the pathogenesis of cervical carcinoma.

Roles of mitogen activated protein kinases and EGF receptor in arsenite-stimulated matrix metalloproteinase-9 production

KRAS mutations are a major cause of drug resistance to molecular-targeted therapies. Aberrant epidermal growth factor receptor (EGFR) signaling may cause dysregulation of microRNA (miRNA) and gene regulatory networks, which leads to cancer initiation and progression. To address the functional relevance of miRNAs in mutant KRAS cancers, we transfected exogenous KRASG12V into human embryonic kidney 293 and MRC5 cells with wild-type KRAS and BRAF genes, and we comprehensively profiled the dysregulated miRNAs. The result showed that mature miRNA oligonucleotide (miR)-4689, one of the significantly down-regulated miRNAs in KRASG12V overexpressed cells, was found to exhibit a potent growth-inhibitory and proapoptotic effect both in vitro and in vivo. miR-4689 expression was significantly down-regulated in cancer tissues compared to normal mucosa, and it was particularly decreased in mutant KRAS CRC tissues. miR-4689 directly targets v-ki-ras2 kirsten rat sarcoma viral oncogene homolog (KRAS) and v-akt murine thymoma viral oncogene homolog 1(AKT1), key components of two major branches in EGFR pathway, suggesting KRAS overdrives this signaling pathway through inhibition of miR-4689. Overall, this study provided additional evidence that mutant KRAS functions as a broad regulator of the EGFR signaling cascade by inhibiting miR-4689, which negatively regulates both RAS/mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/AKT pathways. These activities indicated that miR-4689 may be a promising therapeutic agent in mutant KRAS CRC.

Objective To evaluate the role of extracellular signal-regulated kinase (ERK) signaling pathway in intrathecal dexmedetomidine-induced reduction of spinal cord ischemia-reperfusion (I/R) injury in rats. Methods Eighty clean-grade male Sprague-Dawley rats, aged 9-10 weeks, weighing 300-350 g, were divided into 4 groups (n=20 each) using a random number table method: sham operation group (group S), spinal cord I/R group (group I/R), dexmedetomidine group (group D), and dexmedetomidine plus ERK signaling pathway blocker PD98059 group (group P). Spinal cord ischemia was produced by cross-clamping of the abdominal aorta distal to the left renal artery for 25 min followed by reperfusion to establish the model of spinal cord I/R injury.Dexmedetomidine 1 μg/kg was intrathecally injected at 20 min before establishing the model in D and P groups, PD98059 2 mg/kg was given via the tail vein at the same time in group P, and the equal volume of normal saline was given instead in S and I/R groups.Five rats were selected at 6, 8, 10 and 12 h of reperfusion, and the modified Basso, Beattie, Bresnahan (BBB) scale was used to assess the hindlimb locomotor function.Five rats were sacrificed after assessing the locomotor function at 6 h of reperfusion, and the L3-5 segments of the spinal cord were taken for determination of cell apoptosis (by TUNEL) and expression of phosphorylated ERK (p-ERK) (by Western blot). The apoptosis index was calculated. Results Compared with group S, the BBB scores were significantly decreased at each time point of reperfusion, the apoptosis index was increased, and the expression of p-ERK was up-regulated in the other three groups (P 0.05). Compared with group D, the BBB scores were significantly decreased at each time point of reperfusion, the apoptosis index was increased, and the expression of p-ERK was down-regulated in group P (P<0.05). Conclusion The mechanism by which intrathecal dexmedetomidine reduces spinal cord I/R injury is related to activating ERK signaling pathway in rats. Key words: Dexmedetomidine; Reperfusion injury; Spinal cord; Extracellular signal-regulated MAP kinases

Objective To evaluate the relationship between vascular endothelial growth factor (VEGF) and extracellular signal-regulated kinase (ERK) signaling pathway in spinal dorsal horns of rats with neuropathic pain.Methods Twenty male Sprague-Dawley rats,aged 2 months,weighing 160-320 g,were randomly divided into 4 groups (n =5 each):sham operation group (group S); chronic constrictive injury (CCI) group; normal saline group (NS group); VEGF antibody group.Neuropathic pain was induced by CCI.The animals were anesthetized with intraperitoneal 10％ chloral hydrate 350 mg/kg.The left sciatic nerve was exposed and 4 ligatures were placed on the sciatic nerve at 1 mm intervals.In group S,the left sciatic nerve was only exposed but not ligated.In VEGF antibody group,VEGF antibody 0.3μg/15 μl was injected intrathecally every 2 days for 4 times starting from 2 h after CCI,while the equal volume of normal saline was injected in NS group.Paw withdrawal threshold to von Frey filament stimulation (PWMT) and paw withdrawal latency to nociceptive thermal stimulation (PWTL) were measured at 1 day before CCI (T1),and 1,3,5 and 7 days after CCI (T2-5).The rats were sacrificed after PWMT and PWTL were measured and the L4-6 segments of the spinal cord were removed for determination of phosphorylated ERK (p-ERK) expression in spinal dorsal horns by immunohistochemistry and Western blot.Results Compared with group S,PWMT and PWTL were significantly decreased at T2-5,and the p-ERK expression in spinal dorsal horns was up-regulated in CCI and VEGF antibody groups (P ＜ 0.05).Compared with CCI group,PWMT and PWTL were significantly increased at T3-5,and the p-ERK expression in spinal dorsal horns was down-regualted in VEGF antibody group (P ＜ 0.05).Conclusion VEGF in the spinal dorsal horn is involved in the development and maintenance of neuropathic pain in rats through activating ERK signaling pathway. Key words: Vascular endothelial growth factors; Extracellular signal-regulated MAP kinases; Neuralgia ; Spinal cord

Epidermal Growth Factor Receptor Is a Critical Mediator of Ultraviolet B Irradiation-Induced Signal Transduction in Immortalized Human Keratinocyte HaCaT Cells

Mitogen-activated protein kinase (MAPK) pathways are involved in the regulation of cellular responses, including cell proliferation, differentiation, cell growth, and apoptosis. Because these responses are tightly related to cellular energy level, AMP-activated protein kinase (AMPK), which plays an essential role in energy homeostasis, has emerged as another key regulator. In the present study, we demonstrate a novel signal network between AMPK and MAPK in HCT116 human colon carcinoma. Glucose deprivation activated AMPK and three MAPK subfamilies, extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK), and p38 MAPK. Under these conditions, inhibition of endogenous AMPK by expressing a dominant-negative form significantly potentiated ERK activation, indicating that glucose deprivation-induced AMPK is specifically antagonizing ERK activity in HCT116 cells. Moreover, we provide novel evidence that AMPK activity is critical for p53-dependent expression of dual-specificity phosphatase (DUSP) 1 & 2, which are negative regulators of ERK. Notably, ERK exhibits pro-apoptotic effects in HCT116 cells under glucose deprivation. Collectively, our data suggest that AMPK protects HCT116 cancer cells from glucose deprivation, in part, via inducing DUSPs, which suppresses pro-apoptotic ERK, further implying that a signal network between AMPK and ERK is a critical regulatory point in coupling the energy status of the cell to the regulation of cell survival.

Objective To evaluate the role of spinal extracellular signal-regulated kinase (ERK) signaling pathway in reduction of remifentanil-induced hyperalgesia by electro-acupuncture (EA) at Zusanli in rats with incisional pain. Methods Fifty male adult Sprague-Dawley rats, weighing 250–280 g, in which the intrathecal catheter was successfully placed without complications, were randomly divided into 5 groups (n= 10 each) using a random number table: control group (group C), remifentanil + incisional pain group (group RI), EA at acupoint group (group E), EA at non-acupoint group (group NE), and 1/2 ERK inhibitor U0126 + EA at acupoint group (group UE). Normal saline 0.1 ml· kg–1· min–l was infused intravenously for 60 min in group C. In RI, E, NE and UE groups, after the model of incisional pain was established, remifentanil 1.0 μg · kg–1· min–l was infused for 60 min, and in addition, EA (intensity 10 mA, frequency 4 Hz) of Zusanli lasting for 60 min was performed at the same time in E and UE groups, and EA was performed at the points 5 mm lateral to the acupoints of Zusanli on the operated side simultaneously in group NE.ERK1/2 inhibitor U0126 5 μg (in 5% dimethyl sulfoxide 10 μl) was injected intrathecally in group UE, and 5% dimethyl sulfoxide 10 μl was injected intrathecally in the other groups.The mechanical paw withdrawal threshold (MWT) was measured before remifentanil or normal saline infusion (T1), and at 2 h, 1, and 2 days after the end of infusion (T2-4). After MWT was measured at T4, the expression of ERK1/2 and phosphorylated ERK1/2 (p-ERK1/2) in spinal cord dorsal horns was measured by Western blot. Results Compared with group C, the MWT was significantly decreased at T2-4 in RI, E, NE and UE groups, and the expression of p-ERK1/2 was up-regulated in RI, E and NE groups (P 0.05). Compared with group E, the MWT was significantly increased at T2-4, and the expression of p-ERK1/2 was down-regulated in group UE (P<0.05). Conclusion The mechaism by which EA at Zusanli reduces hyperalgesia induced by remifentanil in rats with incisional pain is related to inhibited activation of ERK signaling pathway in the spinal cord . Key words: Extracellular signal-regulated MAP kinases; Spinal cord; Electric stimulation therapy; POINT ST36 (ZUSANLI); Piperidines; Pain, postoperative; Hyperalgesia

Adipose-derived stem cell (ADSC) transplantation has emerged as a potential tool for the treatment of cardiovascular disease. However, with a limited renewal capacity and the need for mass cells during the engraftment, strategies are needed to enhance ADSC proliferative capacity. In this study, we explored the effects of exendin-4 (Ex-4), a glucagon-like peptide-1 analog, on the growth of ADSCs, focusing in particular on c-Jun NH2-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) signaling pathways. Firstly, ADSCs were isolated and cultured in vitro. Then, flow cytometry demonstrated that ADSCs were positive for CD90 and CD29 but negative for CD31, CD34, and CD45. Ex-4 (0-50nM) treatment increased ADSC proliferation in a dose-dependent manner but had no effects on stem cell markers of ADSCs. Moreover, we found that Ex-4 treatment elevated the phosphorylation levels of the JNK and ERK signaling pathways. Furthermore, utilization of Ex-4 also promoted cyclin D1 and cyclin E protein expression, which was accompanied by more Edu(+) cells and a higher percentage of cells in the S-phase of the cell cycle after Ex-4 treatment. In parallel, the application of inhibitors SP600125 and PD98059, inhibitors of the JNK and ERK signaling pathways, respectively, not only reversed such effects of Ex-4 on JNK and ERK but also resulted in lower percentages of S-phase cells and fewer numbers of Edu(+) cells. In summary, Ex-4 has no effects on stem cell markers in ADSCs but promotes ADSC growth via JNK and ERK signaling pathways.

Inhibitors of the epidermal growth factor receptor (EGFR) have generated considerable hope for cancer treatment, specifically for lung and breast cancers. Therefore, identification of a natural, nontoxic agent(s) as an inhibitor of EGFR is of considerable importance. Delphinidin, an anthocyanidin present in pigmented fruits and vegetables, possesses potent antioxidant and antiproliferative properties. In our study, employing EGFR positive breast cancer AU-565 cells and immortalized MCF-10A cells, we evaluated the effect of delphinidin on EGFR and its downstream signaling pathways. Delphinidin (5-40 microM; 3 hr) treatment of both AU-565 cells and MCF-10A cells inhibited the (i) phosphorylation of EGFR, (ii) activation of PI3K, (iii) phosphorylation of AKT and MAPK. Further, delphinidin treatment of AU-565 cells inhibited EGF-induced autophosphorylation of EGFR, AKT and MAPK, activation of PI3K and cell invasion. We then compared the growth inhibitory effects of delphinidin (5-40 microM; 48 hr), and found that it resulted in a decrease in cell growth of AU-565 and MCF-10A cells but had only minimal effects on normal mammary epithelial 184A1 cells. Treatment of AU-565 cells with delphinidin resulted in (i) induction of apoptosis, (ii) cleavage of PARP protein, (iii) activation of caspase-3 and (iv) downregulation of Bcl-2 with an increase in the expression of Bax. In summary, our study identifies a naturally occurring dietary agent delphinidin as an effective inhibitor of EGFR signaling in breast cancer cells. We suggest that delphinidin could be developed as an agent for the management of EGFR positive human cancers.

Exon Junction Complex Subunits Are Required to Splice Drosophila MAP Kinase, a Large Heterochromatic Gene

A Feedback Loop between Androgen Receptor and ERK Signaling in Estrogen Receptor-Negative Breast Cancer

BackgroundGlioma is the most common tumor of the central nervous system with a poor prognosis. This study aims to explore the role of calcium/calmodulin-dependent protein kinase IIβ (CAMK2B) in regulating the malignant progression of glioma cells, as well as the molecular mechanisms underlying these malignant behaviors.MethodsThe correlation between CAMK2B expression in gliomas and patient prognosis was analyzed using immunohistochemistry, quantitative reverse transcription polymerase chain reaction (qRT-PCR), and western blot. Furthermore, the study explored the role of CAMK2B in glioma cell proliferation, invasion, and migration using cell counting kit-8 (CCK-8), 5-Ethynyl-2′-deoxyuridine (EdU), wound healing, transwell, and in vivo tumor xenograft assays.ResultPatients with high CAMK2B expression exhibited significantly better prognostic outcomes compared to those with low expression levels. Furthermore, CAMK2B expression was significantly lower in glioma tissues and cells compared to both normal brain tissue and human astrocyte cell lines. Notably, overexpression of CAMK2B in glioma cells led to an approximate 40% reduction in proliferative capacity and a 60–70% decrease in invasive and migratory abilities, compared to control glioma cells. These differences were statistically significant at p < 0.05. Conversely, knockdown of CAMK2B using siRNA-CAMK2B significantly enhanced the proliferative, invasive, and migratory capabilities of glioma cells in both in vitro and in vivo settings, enhancing these abilities by 1.5 to 3 times. Notably, these effects were reversed through the application of the Rat Sarcoma viral oncogene homolog (Ras) pathway inhibitor, Salirasib. Western blot analysis revealed that knockdown of CAMK2B led to activation of the Ras/Rapidly Accelerated Fibrosarcoma (Raf)/Mitogen-activated protein kinase kinase (MEK)/Extracellular signal-regulated kinase (ERK) signaling pathway in glioma cell lines, whereas overexpression of CAMK2B resulted in the suppression of this pathway.ConclusionCAMK2B inhibits glioma proliferation, invasion, and migration through the Ras/Raf/MEK/ERK signaling pathway.

Loss of cell-matrix adhesion is often associated with acute epithelial injury, suggesting that "anoikis" may be an important contributor to cell death. Resistance against anoikis is a key characteristic of transformed cells. When nontransformed epithelia are injured, activation of the epidermal growth factor (EGF) receptor (EGFR) by paracrine/autocrine release of soluble ligands can induce a prosurvival program, but there is generally evidence for concomitant dedifferentiation. The EGFR ligand, heparin-binding EGF-like growth factor (HB-EGF), is synthesized as a membrane-anchored precursor that can activate the EGFR via juxtacrine signaling or can be released and act as a soluble growth factor. In Madin-Darby canine kidney cells, expression of membrane-anchored HB-EGF increases cell-cell and cell-matrix adhesion. Therefore, these studies were designed to test the effects of juxtacrine HB-EGF signaling upon cell survival and epithelial integrity when cells are denied proper cell-matrix interactions. Cells expressing a noncleavable mutated form of membrane-anchored HB-EGF demonstrated increased survival from anoikis, formed larger cell aggregates, and maintained epithelial characteristics even following prolonged detachment from the substratum. Physical association between membrane-anchored HB-EGF and EGFR was observed. Signaling studies indicated synergistic effects of EGFR activation and phosphatidylinositol 3-kinase signaling to regulate apoptotic and survival pathways. In contrast, although administration of exogenous EGF partially suppressed anoikis in wild type cells, it also led to an increased expression of mesenchymal markers, suggesting dedifferentiation. Taken together, we propose a novel role for membrane-anchored HB-EGF in the cytoprotection of epithelial cells.