Epidermal Cell Migration Research Articles

Down-Regulation of ClC-3 Expression Reduces Epidermal Stem Cell Migration by Inhibiting Volume-Activated Chloride Currents.

ClC-3, a member of the ClC chloride (Cl(-)) channel family, has recently been proposed as the primary Cl(-) channel involved in cell volume regulation. Changes in cell volume influence excitability, contraction, migration, pathogen-host interactions, cell proliferation, and cell death processes. In this study, expression and function of ClC-3 channels were investigated during epidermal stem cell (ESC) migration. We observed differential expression of CLC-3 regulates migration of ESCs. Further, whole-cell patch-clamp recordings and image analysis demonstrated ClC-3 expression affected volume-activated Cl(-) current (I Cl,Vol) within ESCs. Live cell imaging systems, designed to observe cellular responses to overexpression and suppression of ClC-3 in real time, indicated ClC-3 may regulate ESC migratory dynamics. We employed IMARIS software to analyze the velocity and distance of ESC migration in vitro to demonstrate the function of ClC-3 channel in ESCs. As our data suggest volume-activated Cl(-) channels play a vital role in migration of ESCs, which contribute to skin repair by migrating from neighboring unwounded epidermis infundibulum, hair follicle or sebaceous glands, ClC-3 may represent a new and valuable target for stem cell therapies.

Excessive Reversal of Epidermal Growth Factor Receptor and Ephrin Signaling Following Tracheal Occlusion in Rabbit Model of Congenital Diaphragmatic Hernia.

Congenital diaphragmatic hernia (CDH) causes severe pulmonary hypoplasia from herniation of abdominal contents into the thorax. Tracheal occlusion (TO) for human CDH improves survival, but morbidity and mortality remain high, and we do not fully understand the cellular pathways and processes most severely impacted by CDH and TO. We created a left diaphragmatic hernia (DH) in rabbit fetuses with subsequent TO and collected left lung sections for NextGen mRNA sequencing. DH, TO, and DHTO fetuses had comparable body and organ growth to control except for lower lung weights in DH (p<0.05). Of 13,687 expressed genes, DHTO had 687 differentially expressed genes compared to DH, but no other group-group comparison had more than 10. Considering genes in combination, many of the genes reduced in DH were more highly expressed in DHTO than in control. Benchmarking fetal rabbit lung gene expression to published lung development data, both DH and DHTO lungs were more highly correlated with the gene expression of immature lung. DNA synthesis was upregulated in DHTO compared to DH and ribosome and protein synthesis pathways were downregulated. DH reduced total and epithelial cell proliferation by half and two-thirds respectively, and DHTO increased proliferation by 2.5 and 3.4-fold respectively. Signaling pathways downregulated by DH and upregulated in DHTO were epidermal growth factor receptor signaling, ephrin signaling, and cell migration; however, levels of ephrin and EGFR signaling in DHTO exceeded that of control. Identification and inhibition of the ligands responsible for this dysregulated signaling could improve lung development in CDH.

Effect of microtubule-associated protein-4 on epidermal cell migration under different oxygen concentrations.

After skin trauma, regional epidermal cell migration mediates the re-epithelialization of the wound surface, which is an important step for wound healing, yet the underlying molecular regulatory mechanism is unclear. In the current study, HaCaT cells were maintained under different oxygen concentrations (1%, 21%, 40% and 65%). Technologies including immunofluorescence staining, wound scratch, transwell invasion, western blot and low-expression lentiviral vector were utilized to observe the changes in microtubule dynamics and the microtubule-associated protein (MAP)4 expression. MAP4's effect on cell migration under different oxygen concentrations was also studied. The results showed that under hyperoxic (40% and 65%) and hypoxic (1%) conditions, HaCaT cells were able to regulate cell microtubule dynamics by MAP4, thus promoting cell migration. On the other hand, MAP4 silencing through targeted shRNA attenuated HaCaT cell migration under the above oxygen concentrations. These results imply that MAP4 plays an important role in epidermal cell migration under different oxygen concentrations.

Quercetin 3-O-glucoside suppresses epidermal growth factor-induced migration by inhibiting EGFR signaling in pancreatic cancer cells.

Pancreatic cancer is one of the most dangerous cancers and is associated with a grave prognosis. Despite increased knowledge of the complex signaling networks responsible for progression of pancreatic cancer, many challenging therapies have fallen short of expectations. In this study, we examined the anti-migratory effect of quercetin 3-O-glucoside in epidermal growth factor-induced cell migration by inhibiting EGF receptor (EGFR) signaling in several human pancreatic cancer cell lines. Treatment with quercetin, quercetin 3-O-glucoside, and quercetin 7-O-glucoside differentially suppressed epidermal growth factor-induced migration activity of human pancreatic cancer cells. In particular, quercetin 3-O-glucoside strongly inhibited the infiltration activity of pancreatic cancer cells in a dose-dependent manner. Furthermore, quercetin 3-O-glucoside exerted the anti-migratory effect even at a relatively low dose compared with other forms of quercetin. The anti-tumor effects of quercetin 3-O-glucoside were mediated by selectively inhibiting the EGFR-mediated FAK, AKT, MEK1/2, and ERK1/2 signaling pathway. Combinatorial treatment with quercetin 3-O-glucoside plus gemcitabine showed the synergistic anti-migratory effect on epidermal growth factor-induced cell migration in human pancreatic cancer cell lines. These results suggest that quercetin 3-O-glucoside has potential for anti-metastatic therapy in human pancreatic cancer.

Calcium and Vitamin D Signaling in the Epidermal Response to Wounding

Wound healing is essential for survival. This is a multistep process involving a number of different cell types. In the skin wounding triggers an acute inflammatory response, with the innate immune system contributing both to protection against invasive organisms and to triggering the invasion of inflammatory cells into the wounded area. These cells release a variety of cytokines and growth factors that stimulate the proliferation and migration of dermal and epidermal cells to close the wound. In particular, wounding activates stem cells in the interfollicular epidermis (IFE) and hair follicles (HF) to proliferate and send their progeny to re-epithelialize the wound. Failure to close wounds leads to medical costs estimated in the US at over $25 billion and affecting 6.5 million people. Our previous studies have shown that vitamin D and calcium signaling play important roles in these events. Vitamin D and calcium signaling are necessary for a normal innate immune and inflammatory response to wounding in the epidermis. Moreover, VDR is required for maintenance of hair follicle (HF) stem cells known to contribute to wound closure of the IFE. Mice lacking the calcium sensing receptor (CaSR) or the VDR when placed on a low calcium diet have delayed wound healing. This is associated with a reduction in the number of cells in the stem cell niches in both HF and IFE and reduced proliferation and migration in the cells at the leading edge of the epithelium after wounding. We hypothesize that at least part of this delay in wound closure is due to a reduction of stem cell activation and number in cells lacking the VDR and/or their failure of activation by calcium in cells lacking the CaSR, and are currently investigating this concept. Keywords: Calcium, epidermis, ora 1, signaling, stim1, vitamin D, wounding.

Effect of electric fields on proliferation and migration of epidermal stem cells

Objective To investigate the effect of endogenous electric fields on proliferation and migration of epidermal stem cells (EpSCs) in vitro. Methods EpSCs in the first passage were cultured on simulated endogenous electric field. Galvanic stimulation set at an intensity of 0 mV/mm (GroupⅠ), 100 mV/mm (GroupⅡ) and 200 mV/mm(Group Ⅲ) was given twice a day for 3 days with each time continuing1 hour and resting 1 hour. Effect of bio-electric field on cell proliferation was measured by direct cell counting in fixed visual field. Repeated experiment but continued stimulation for 3 hours was performed. Live cell migration was monitored to determine the effect of bio-electric field on the process of cell migration. Results For the EpSCs cultured in endogenous bio-electric simulation platform for 24, 48 and 72 hours, cell proliferation rate was the highest in Group Ⅲ[(107.4±21.9)%, (270.2±71.4)%, (544.0±95.1)% ] (P<0. 01). And higher cell proliferation was observed in Group Ⅰ[(35.1±21.0)%, (138.6±31.0)%, (323.5±23.0)%] than in Group Ⅱ[(66.9±24.2)% , (192.1±36.2)%, (406.7±50.7)%] (P<0. 01). After continued galvanic stimulation for 3 hours, cells in Groups Ⅱ and Ⅲ oriented towards cathode, but cells in Group Ⅰ moved randomly. In measurements of track velocity (Vt), displacement velocity (Vd) and electric field migration rate (Vx), Group Ⅲ revealed increased values[(42.5±2.8), (32.3 ±1.8), (29.7±1.3)μm/h] as compared with GroupⅠ[(36.2±2.2), (23.6±2.9), (18.2±1.8)μm/h] and Group Ⅱ[(34.3±1.6), (23.8±1.2), (21.2±1.6)μm/h] (P<0.01). Conclusion In vitro experiments reveal that endogenous electric fields can promote the proliferation of EpSCs and induce oriented movements towards the cathode. Key words: Stem cells; Cell proliferation; Cell movement; In vitro

Stromal cell-derived factor 1 (SDF-1) accelerated skin wound healing by promoting the migration and proliferation of epidermal stem cells.

Epidermal stem cells could contribute to skin repair through the migration of cells from the neighboring uninjured epidermis, infundibulum, hair follicle, or sebaceous gland. However, little is known about the factors responsible for the complex biological processes in wound healing. Herein, we will show that the attracting chemokine, SDF-1/CXCR4, is a major regulator involved in the migration of epidermal stem cells during wound repair. We found that the SDF-1 levels were markedly increased at the wound margins following injury and CXCR4 expressed in epidermal stem cells and proliferating epithelial cells. Blocking the SDF-1/CXCR4 axis resulted in a significant reduction in epidermal stem cell migration toward SDF-1 in vitro and delayed wound healing in vivo, while an SDF-1 treatment enhanced epidermal stem cell migration and proliferation and accelerated wound healing. These results provide direct evidence that SDF-1 promotes epidermal stem cell migration, accelerates skin regeneration, and makes the development of new regenerative therapeutic strategies for wound healing possible.

Dipeptidyl peptidase 9 subcellular localization and a role in cell adhesion involving focal adhesion kinase and paxillin

Dipeptidyl peptidase 9 (DPP9) is a ubiquitously expressed member of the DPP4 gene and protease family. Deciphering the biological functions of DPP9 and its roles in pathogenesis has implicated DPP9 in tumor biology, the immune response, apoptosis, intracellular epidermal growth factor-dependent signaling and cell adhesion and migration. We investigated the intracellular distribution of DPP9 chimeric fluorescent proteins and consequent functions of DPP9. We showed that while some DPP9 is associated with mitochondria, the strongest co-localization was with microtubules. Under steady state conditions, DPP9 was not seen at the plasma membrane, but upon stimulation with either phorbol 12-myristate 13-acetate or epidermal growth factor, some DPP9 re-distributed towards the ruffling membrane. DPP9 was seen at the leading edge of the migrating cell and co-localized with the focal adhesion proteins, integrin-β1 and talin. DPP9 gene silencing and treatment with a DPP8/DPP9 specific inhibitor both reduced cell adhesion and migration. Expression of integrin-β1 and talin was decreased in DPP9-deficient and DPP9-enzyme-inactive cells. There was a concomitant decrease in the phosphorylation of focal adhesion kinase and paxillin, indicating that DPP9 knockdown or enzyme inhibition suppressed the associated adhesion signaling pathway, causing impaired cell movement. These novel findings provide mechanistic insights into the regulatory role of DPP9 in cell movement, and may thus implicate DPP9 in tissue and tumor growth and metastasis.

Topical pimecrolimus inhibits high-dose UVB irradiation-induced epidermal Langerhans cell migration, via regulation of TNF-α and E-cadherin.

BackgroundTopical pimecrolimus has been shown to reverse epidermal CD1a+ Langerhans cell reduction induced by high-dose ultraviolet (UV)B irradiation, but the mechanism is still unclear. This study aimed to investigate the possible mechanism of the effect of pimecrolimus on high-dose UVB-irradiated epidermal Langerhans cells.MethodsForty human foreskin tissues were divided into four groups: control; pimecrolimus-only; UVB-only; and UVB + pimecrolimus. All tissues were cultured, and each tissue was cut into four pieces, corresponding to four time points (0 hours, 18 hours, 24 hours, and 48 hours). We collected the tissues and culture medium at each time point. The percentage of CD1a+ cells in medium was detected by flow cytometry. The tissues were detected for messenger (m)RNA and protein expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and E-cadherin, by reverse-transcription polymerase chain reaction (PCR) and Western blot.ResultsAt 18 hours, 24 hours, and 48 hours, the CD1a+ cells in the culture medium of the UVB-only group and the UVB + pimecrolimus group were significantly more than in the control group, while the CD1a+ cells of the UVB + pimecrolimus group was less than of the UVB-only group. For both the UVB-only group and UVB + pimecrolimus group, TNF-α expression (by both reverse-transcription PCR and Western blot) of the tissues was clearly higher and E-cadherin expression was significantly lower compared with the control group, at 18 hours, 24 hours, and 48 hours. For the UVB + pimecrolimus group, TNF-α was clearly lower and E-cadherin was significantly higher compared with the UVB-only group.ConclusionTopical pimecrolimus inhibited epidermal Langerhans cell migration induced by high-dose UVB irradiation, via regulation of TNF-α and E-cadherin.

Calcium, Orai1, and Epidermal Proliferation

Ca2+ influx controls essential epidermal functions, including proliferation, differentiation, cell migration, itch, and barrier homeostasis. The Orai1 ion channel allows capacitive Ca2+ influx after Ca2+ release from the endoplasmic reticulum, and it has now been shown to modulate epidermal atrophy. These findings reveal new interactions among various Ca2+ signaling pathways and uncover novel functions for Ca2+ signaling via the Orai1 channel.

Helium-Neon Laser Irradiation Promotes the Proliferation and Migration of Human Epidermal Stem Cells In Vitro: Proposed Mechanism for Enhanced Wound Re-epithelialization

The present study was conducted to investigate the effects of helium-neon (He-Ne) laser irradiation on the proliferation, migration, and differentiation of cultured human epidermal stem cells (ESCs). A He-Ne laser with a wavelength of 632.8 nm is known to have photobiological effects, and is widely used for accelerating wound healing; however, the cellular mechanisms involved have not been completely understood. The ESCs were prepared from human foreskin, and irradiated by using He-Ne laser at 632.8 nm with 2 J/cm(2). The ESC proliferation, migration, and differentiation were examined by using XTT assay, scratch assay, and flow cytometry technology, respectively. The phosphorylation of extracellular signal-regulated kinases (ERK) was analyzed by using Western blotting. He-Ne laser irradiation markedly promoted cell proliferation and migration accompanied by an increase in the phosphorylation of ERK, but did not significantly influence cell differentiation. Our data indicated that photostimulation with a He-Ne laser resulted in a significant increase in human ESC proliferation and migration in vitro, which might contribute, at least partially, to accelerated wound re-epithelialization by low-level laser therapy.

Focal Contact and Hemidesmosomal Proteins in Keratinocyte Migration and Wound Repair

Significance: During wound healing of the skin, keratinocytes should move over while still adhering to their underlying matrix. Thus, mechanistic insights into the wound-healing process require an understanding of the forms and functions of keratinocyte matrix adhesions, specifically focal contacts and hemidesmosomes, and their components. Recent Advances: Although the structure and composition of focal contacts and hemidesmosomes are relatively well defined, the functions of their components are only now being delineated using mouse genetic models and knockdown approaches in cell culture systems. Remarkably, both focal contact and hemidesmosomal proteins appear involved in determining the speed and directional migration of epidermal cells by modulating several signal transduction pathways. Critical Issues: Although many publications are centered on focal contacts, their existence in tissues such as the skin is controversial. Nonetheless, focal contact proteins are central to mechanisms that regulate skin cell motility. Conversely, hemidesmosomes have been identified in intact skin but whether hemidesmosomal components play a positive regulatory function in keratinocyte motility remains debated in the field. Future Directions: Defective wound healing is a developing problem in the aged, hospitalized and diabetic populations. Hence, deriving new insights into the molecular roles of matrix adhesion proteins in wound healing is a prerequisite to the development of novel therapeutics to enhance tissue repair and regeneration.

Damnacanthal, an effective inhibitor of LIM-kinase, inhibits cell migration and invasion

LIM-kinases (LIMKs) play crucial roles in various cell activities, including migration, division, and morphogenesis, by phosphorylating and inactivating cofilin. Using a bimolecular fluorescence complementation assay to detect the actin-cofilin interaction, we screened LIMK1 inhibitors and identified two effective inhibitors, damnacanthal (Dam) and MO-26 (a pyrazolopyrimidine derivative). These compounds have already been shown to inhibit Lck, a Src family tyrosine kinase. However, in vitro kinase assays revealed that Dam inhibited LIMK1 more effectively than Lck. Dam suppressed LIMK1-induced cofilin phosphorylation and deceleration of actin retrograde flow in lamellipodia in N1E-115 cells. Dam impaired CXCL12-induced chemotactic migration of Jurkat T lymphocytes and Jurkat-derived, Lck-deficient JCaM1.6 cells and also inhibited serum-induced migration and invasion of MDA-MB-231 breast carcinoma cells. These results suggest that Dam has the potential to suppress cell migration and invasion primarily through the inhibition of LIMK kinase activity. Topical application of Dam also suppressed hapten-induced migration of epidermal Langerhans cells in mouse ears. Dam provides a useful tool for investigating cellular and physiological functions of LIMKs and holds promise for the development of agents against LIMK-related diseases. The bimolecular fluorescence complementation assay system used in this study will provide a useful method to screen for inhibitors of various protein kinases.

Recombinant keratinocyte growth factor 1 in tobacco potentially promotes wound healing in diabetic rats.

Keratinocyte growth factor 1 (KGF1) is a growth factor that promotes epidermal cell proliferation, migration, differentiation, and wound repair. It is expressed at low levels in a form of inclusion body in E. coli. In order to increase its expression and activity, we produced tobacco plants expressing KGF1 via Agrobacterium-mediated transformation using a potato virus X (PVX)-based vector (pgR107). The vector contained the sequence encoding the KGF1 gene fused with a green florescence protein. The recombinant plasmid was introduced into leaf cells of Nicotiana benthamiana (a wild Australian tobacco) via Agrobacterium-mediated agroinfiltration. As determined by fluorescence and Western blot of leaf extracts, the KGF1 gene was correctly translated into the tobacco plants. The recombinant KGF1 was purified from plant tissues by heparin affinity chromatography, and cell proliferation in NIH/3T3 cells was stimulated by the purified KGF1. The purified KGF1 was also applied to the wounds of type-II diabetic rats. KGF1 had accumulated to levels as high as 530 μg/g fresh weight in the leaves of agroinfected plants. We show that plant-derived KGF1 can promote the proliferation of NIH/3T3 cells and have significant effects on the type-II diabetic rat. The present findings indicated that KGF1 from tobacco maintains its biological activity, implying prospective industrial production in a plant bioreactor.

Key differences identified between actinic keratosis and cutaneous squamous cell carcinoma by transcriptome profiling

Background:Cutaneous squamous cell carcinoma (cSCC) is one of the most common malignancies in fair-skinned populations worldwide and its incidence is increasing. Despite previous observations of multiple genetic abnormalities in cSCC, the oncogenic process remains elusive. The purpose of this study was to elucidate key molecular events associated with progression from premalignant actinic keratoses (AKs) to invasive cSCC by transcriptome profiling.Methods:We combined laser capture microdissection with the Affymetrix HGU133 Plus 2.0 microarrays to profile 30 cSCC and 10 AKs.Results:We identified a core set of 196 genes that are differentially expressed between AK and cSCC, and are enriched for processes including epidermal differentiation, cell migration, cell-cycle regulation and metabolism. Gene set enrichment analysis highlighted a key role for the mitogen activated protein kinase (MAPK) pathway in cSCC compared with AK. Furthermore, the histological subtype of the tumour was shown to influence the expression profile.Conclusion:These data indicate that the MAPK pathway may be pivotal to the transition from AK to cSCC, thus representing a potential target for cSCC prevention. In addition, transcriptome differences identified between cSCC subtypes have important implications for future development of targeted therapies for this malignancy.

Abstract A34: A regulatory role of beta-PIX in epidermal growth factor-induced cancer cell migration

Abstract Expression of epidermal growth factor receptor (EGFR) in non–small cell lung cancer (NSCLC) tumors correlates with poor prognosis. EGFR signaling is Src dependent. Activation of EGFR leads to cycles of membrane protrusion, cell adhesion, contraction, and retraction, therefore promoting cell migration. Here, we show a novel role of beta-PIX (Pak-interactive exchange factor) in EGFR-mediated NSCLC cell migration. EGFR signals through Src, which phosphorylates beta-PIX sequentially at two specific tyrosine residues, 442 and 595. Phosphorylation of beta-PIX at tyrosine 442 leads to activation of small GTPase Rac1, which promotes membrane protrusion and cell adhesion assembly around 5 min after EGF stimulation. After another 20 minutes, tyrosine 442 is dephosphorylated, while tyrosine 595 of beta-PIX is phosphorylated. Phosphorylation of tyrosine 595 results in activation of small GTPase RhoA, contraction generation, adhesion disassembly, and cell retraction. These data suggest that the phosphorylation-dephosphorylation cycle of beta-PIX at tyrosine 442 and 595 serves as a regulatory signal downstream of EGFR to control migration and invasion of NSCLC cells. Note: This abstract was not presented at the conference. Citation Format: Jean-Cheng Kuo. A regulatory role of beta-PIX in epidermal growth factor-induced cancer cell migration. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr A34.

Caenorhabditis elegans anillin (ani-1) regulates neuroblast cytokinesis and epidermal morphogenesis during embryonic development

The formation of tissues is essential for metazoan development. During Caenorhabditis elegans embryogenesis, ventral epidermal cells migrate to encase the ventral surface of the embryo in a layer of epidermis by a process known as ventral enclosure. This process is regulated by guidance cues secreted by the underlying neuroblasts. However, since the cues and their receptors are differentially expressed in multiple cell types, the role of the neuroblasts in ventral enclosure is not fully understood. Furthermore, although F-actin is required for epidermal cell migration, it is not known if nonmuscle myosin is also required. Anillin (ANI-1) is an actin and myosin-binding protein that coordinates actin–myosin contractility in the early embryo. Here, we show that ANI-1 localizes to the cleavage furrows of dividing neuroblasts during mid-embryogenesis and is required for their division. Embryos depleted of ani-1 display a range of ventral enclosure phenotypes, where ventral epidermal cells migrate with similar speeds to control embryos, but contralateral neighbors often fail to meet and are misaligned. The ventral enclosure phenotypes in ani-1 RNAi embryos suggest that the position or shape of neuroblasts is important for directing ventral epidermal cell migration, although does not rule out an autonomous requirement for ani-1 in the epidermal cells. Furthermore, we show that rho-1 and other regulators of nonmuscle myosin activity are required for ventral epidermal cell migration. Interestingly, altering nonmuscle myosin contractility alleviates or strengthens ani-1's ventral enclosure phenotypes. Our findings suggest that ventral enclosure is a complex process that likely relies on inputs from multiple tissues.

Thyroid cancer cell resistance to gefitinib depends on the constitutive oncogenic activation of the ERK pathway.

Poorly differentiated thyroid carcinomas are refractory to common anticancer therapies, and novel inhibitors are being tested in these deadly malignancies. The epidermal growth factor receptor (EGFR) tyrosine kinase represents an attractive target for treatment because it is up-regulated in thyroid cancer and plays a role in cancer progression. However, EGFR inhibitors have provided poor results in thyroid carcinomas. We evaluated the possible mechanism underlying the resistance of thyroid cancer cells to EGFR inhibitors. We tested the effect of the EGFR tyrosine kinase inhibitor gefitinib in a panel of thyroid cancer cell lines. We found that in most of the cell lines, although gefitinib inhibited EGFR phosphorylation, it was poorly effective in reducing cell viability. gefitinib, however, was able to inhibit epidermal growth factor-induced cell migration and matrix invasion. In most thyroid cancer cell lines, gefitinib significantly inhibited Akt phosphorylation by inhibiting EGFR activation, but it had limited or no effect on ERK phosphorylation. The poor cell response to gefitinib was associated with genetic alterations, leading to constitutive activation of the ERK pathway, including BRAF(V600E) and HRAS(G12A/Q61R) mutations and RET/PTC1 rearrangement. When BRAF(V600E)-positive thyroid cancer cells were incubated with the specific BRAF inhibitor PLX4032, sensitivity to gefitinib was restored. Similar results were obtained with rat sarcoma and RET/papillary thyroid cancer inhibitors. These results indicate that thyroid cancer resistance to gefitinib is due to the constitutive activation of the mitogenic pathway by either signals downstream of EGFR or other tyrosine kinase receptors. This resistance can be overcome by the combined use of selective inhibitors.

SGEF enhances EGFR stability through delayed EGFR trafficking from early to late endosomes

Previously, we demonstrated an elevated SH3-containing guanine nucleotide exchange factor (SGEF) expression in clinical specimens with prostate cancer and implicated the role of SGEF in prostate tumorigenesis. However, the molecular mechanism behind the SGEF regulation of prostate cancer development is not known. In this study, we show that SGEF expression delays epidermal growth factor receptor (EGFR) degradation in prostate cancer cells and is independent from its guanine nucleotide exchange factor (GEF) function. We further show that the delayed degradation is due to a delay in EGFR trafficking from early to late endosomes and not to a decrease in EGFR ubiquitination. Finally, we show that depletion of SGEF significantly inhibits epidermal growth factor-induced EGFR signaling cascade and cell migration in the prostate cancer cells. We report for the first time an SGEF function for RhoG that excludes GEF and the ability of SGEF to enhance EGFR stability and signaling by delaying its lysosomal sorting and degradation. This could be one mechanism by which SGEF contributes to prostate cancer progression.

Effects of μ-opoiod receptor on proliferation and migration of human epidermal stem cells in vitro

Objective To investigate the affects of μ-opioid receptor activation on proliferation and migration of epidermal stem cells (ESCs) in vitro.Methods Primary human ESCs (hESCs) were isolated and cultured,and marked by both integrin β31 and eytokeratin 19 (CK19) to be identified.The hESCs of the second generation were cultured with K-SFM supplemented with 1 nmol/L β-endorphins in group A,with K-SFM supplemented with 10 nmol/L naloxone and 1 nmol/L β-endorphins in group B,and with K-SFM supplemented with no drugs in group C.The proliferative ability of hESCs in each group was determined by using methyl thiazol tetrazolium (MTT) assay for 5 consecutive days.The 100 μm scratch wounds were created by scraping confluent hESCs plated on Petri-dishes with a sterile pipette tip in vitro.The pictures of migrating cells from the wound edge were taken at 24,48,72 and 96 h after incubarton with different media.The wound healing rate was calculated by Image-Pro Plus software at 72 h.Results Cultured primary hESCs could adhere to the wall and showed cobblestone-like shape.Immunofluorescence staining showed the positive results for integrin β1 and CK19.The proliferation rate of hESCs detected hy using MTT assay was significantly higher in group A than in groups C,visibly higher in group C than in group B during the day 2 to day 5,and the difference between each two groups was statistically significant (P ＜ 0.05).In group A,the number of cells migrating the wound edge was greater than in group C,and less in group B than in group C at 24 h.The wound healing rate in groups A,B and C at 72 h was (91.80 ± 0.05) ％,(79.40 ± 0.06) ％,and (86.30 ± 0.75) ％ respectively,showing significant differences among groups (P ＜ 0.05).Conclusion The activation of μ-opioid receptor can promote the proliferation and migration of hESCs in vitro.The μ-opioid receptor may be involved in some modutory processes of skin metabolisms. Key words: Epidermal stem cells ; Opioid receptor ; Proliferation ; Migration