Potential therapeutic effects of pigment epithelium-derived factor for treatment of diabetic retinopathy

Diabetic retinopathy (DR), a major micro-vascular complication of diabetes, has emerged as a leading cause of visual impairment and blindness among working adults in the worldwide. The pathobiology of DR involves multiple molecular pathways and is characterized chronic neurovascular degeneration. Current approaches to prevent or to treat DR are still far from satisfactory. Therefore, it is important to develop new therapeutic strategies for the prevention and treatment to DR. Pigment epithelium-derived factor (PEDF), a 50-kDa secreted glycoprotein, has been described as a multi-functional protein. Some emerging evidences indicate that PEDF are able to target multiple pathways exerting neurotropic, neuroprotective, anti-angiogenic, antivasopermeability, anti-inflammation, anti-thrombogenic and anti-oxidative effects in DR. In this review, we addressed the functions of PEDF in different pathways, which could lead to potential therapeutics on the treatment to DR.

Are the changes in the peripheral brain-derived neurotrophic factor levels due to platelet activation?

Brain-derived neurotrophic factor(BDNF) plays an important role in central nervous system development, neurogenesis and neuronal plasticity. BDNF is also expressed in several non-neuronal tissues, and it could play an important role in other processes, such as cancer, angiogenesis, etc. Platelets are the major source of peripheral BDNF. However, platelets also contain high amounts of serotonin; they express specific surface receptors during activation, and a multitude of pro-inflammatory and immunomodulatory bioactive compounds are secreted from the granules. Until recently, there was insufficient knowledge regarding the relationship between BDNF and platelets. Recent studies showed that BDNF is present in two distinct pools in platelets, in α-granules and in the cytoplasm, and only the BDNF in the granules is secreted following stimulation, representing 30% of the total BDNF in platelets. BDNF has an important role in the pathophysiology of depression. Low levels of serum BDNF have been described in patients with major depressive disorder, and BDNF levels increased with chronic antidepressant treatment. Interestingly, there is an association between depression and platelet function. This review analyzed studies that evaluated the relationship between BDNF and platelet activation and the effect of treatments on both parameters. Only a few studies consider this possible confounding factor, and it could be very important in diseases such as depression, which show changes in both parameters.

Decreased serum platelet derived growth factor BB levels in acute and increased in chronic pancreatitis

AIM: To examine circulating growth factor concentrations in patients with acute pancreatitis (AP) and chronic pancreatitis (CP), and walled-off pancreatic necrosis (WOPN).

Effects of “Nourishing Liver and Kidney” Acupuncture Therapy on Expression of Brain Derived Neurotrophic Factor and Synaptophysin after Cerebral Ischemia Reperfusion in Rats

The aim of the present study was to investigate the effect of ＂nourishing liver and kidney＂ acupuncture therapy on motor and cognitive deficits,and the underlying mechanism following cerebral ischemia-reperfusion（I/R） via increasing the expression of brain derived neurotrophic factor（BDNF） and synaptophysin（SYN） in the hippocampus.Healthy adult male SD rats were randomly divided into sham operation group（n=51）,model group（n=51）,acupuncture group（n=51） and acupuncture control group（n=51）.The middle cerebral I/R model was established.Acupunctures were performed in the acupuncture group and acupuncture control group at acupoints of Taixi（K103）,Taichong（ST09） of both sides,for 30 min once daily every morning.The animals in the sham operation group and model group were conventionally fed in the cage,without any intervention therapy.The rats of each group were assessed with modified neurological severity scores（m NSS）.The expression of BDNF and SYN in the hippocampus was detected by immunohistochemical SP method and the synaptic structure in hippocampus area was assessed morphologically and quantitatively at the 3rd,7th and 14 th day.The Morris water Maze（MWM） test was used to evaluate the rats＇ learning and memory abilities on the 15 th day after acupuncture.The animals in the acupuncture control group and sham operation group presented no neurological deficit.In the acupuncture group,the nerve functional recovery was significantly better than that in the model group at the 7th and 14 th day after modeling.The average MWM escape latency in the acupuncture group was shorter than that in the model group at the 3rd,4th and 5th day.The number of crossings of the platform quadrant in the acupuncture group was significantly more than that in the model group.At the each time point,the expression levels of BDNF and SYN in the hippocampal regions increased significantly in the model group as compared with the sham operation group and the acupuncture control group.In the acupuncture group,the expression levels of BDNF at the 7th and 14 th day increased more significantly than those in the model group.In the acupuncture group,the expression levels of SYN at the each time point increased more significantly than those in the model group.The post-synaptic density（PSD） was significantly increased and the synapse cleft width was narrowed in the acupuncture group as compared with other groups.The synaptic curvatures were improved obviously in the acupuncture group in contrast to the model group.It was concluded that the ＂nourishing liver and kidney＂ acupuncture therapy has positive effects on behavioral recovery,as well as learning and memory abilities,probably by promoting the expression of BDNF and SYN,and synaptic structure reconstruction in the ipsilateral hippocampus after I/R in rats.The ＂nourishing liver and kidney＂ acupuncture therapy can promote the functional recovery in rats after cerebral ischemia injury.

Prolonged propagation of rat neural stem cells relies on inhibiting autocrine/paracrine bone morphogenetic protein and platelet derived growth factor signals

Continuous expansion of rat neural stem cell lines has not been achieved due to proliferation arrest and spontaneous differentiation in vitro. In the current study, neural precursor cells derived from the subventricular zone of adult rats spontaneously underwent astroglial and oligodendroglial differentiation after limited propagation. This differentiation was largely induced by autocrine or paracrine bone morphogenetic protein and platelet derived growth factor signals. The results showed that, by inhibiting bone morphogenetic protein and platelet derived growth factor signals, adult rat neural precursor cells could be extensively cultured in vitro as tripotent stem cell lines. In addition to adult rat neural stem cells, we found that bone morphogenetic protein antagonists can promote the proliferation of human neural stem cells. Therefore, the present findings illustrated the role of autocrine or paracrine bone morphogenetic protein and platelet derived growth factor signaling in determining neural stem cell self-renewal and differentiation. By antagonizing both signals, the long-term propagation of rat neural stem cell lines can be achieved.

Effect of adenovirus-mediated brain derived neurotrophic factor in early retinal neuropathy of diabetes in rats

AIMTo observe effect of adenovirus-mediated brain derived neurotrophic factor in early retinal neuropathy of diabetes in rats.

Association of Increased Urine Brain Derived Neurotrophic Factor with Lower Urinary Tract Symptoms in Men with Benign Prostatic Hyperplasia

Urinary brain-derived neurotrophic factor（BDNF）, an ubiquitous neurotrophin, was found to rise in patients with benign prostatic hyperplasia（BPH）. We hypothesized that the urinary level of BDNF could be a potential biomarker for lower urinary tract symptoms（LUTS） in patients with BPH. Totally, 76 patients with BPH-caused LUTS and 32 male control subjects without BPH were enrolled. International Prostate Symptom Score（IPSS） was applied to assess the symptom severity of LUTS. Urodynamic tests were performed for the diagnosis of underlying detrusor overactivity（DO） in the patients with BPH. Urine samples were collected from all subjects. Urinary BDNF levels were measured using enzyme-linked immunosorbent assays and normalized by urinary creatinine（Cr） levels. Seventy-six BPH patients were divided into moderate LUTS group（n=51, 720） according to the IPSS. Of the 76 BPH patients, DO was present in 34（44.7%） according to the urodynamic test. The urinary BDNF/Cr levels were significantly higher in BPH patients with moderate LUTS（8.29±3.635, P〈0.0001） and severe LUTS（11.8±6.44, P〈0.0001） than normal controls（1.71±0.555）. Patients with severe LUTS tended to have higher urinary BDNF/Cr levels than patients with moderate LUTS（11.8±6.44 vs. 8.29±3.635, P=0.000）. The conditions of BPH with LUTS correlated with elevated urinary BDNF levels, and urinary BDNF levels were even higher in BPH-DO patients. The results of this study have provided evidence to suggest that urinary BDNF level test could evaluate the severity of LUTS in BPH patients, and BDNF level can be used as a biomarker

Ketogenic diet alleviates cognitive dysfunction and neuroinflammation in APP/PS1 mice via the Nrf2/HO-1 and NF-κB signaling pathways

Alzheimer's disease is a progressive neurological disorder characterized by cognitive decline and chronic inflammation within the brain.The ketogenic diet,a widely recognized therapeutic intervention for refractory epilepsy,has recently been proposed as a potential treatment for a variety of neurological diseases,including Alzheimer's disease.However,the efficacy of ketogenic diet in treating Alzheimer's disease and the underlying mechanism remains unclear.The current investigation aimed to explore the effect of ketogenic diet on cognitive function and the underlying biological mechanisms in a mouse model of Alzheimer's disease.Male amyloid precursor protein/presenilin 1(APP/PS1)mice were randomly assigned to either a ketogenic diet or control diet group,and received their respective diets for a duration of 3 months.The findings show that ketogenic diet administration enhanced cognitive function,attenuated amyloid plaque formation and proinflammatory cytokine levels in APP/PS1 mice,and augmented the nuclear factor-erythroid 2-p45 derived factor 2/heme oxygenase-1 signaling pathway while suppressing the nuclear factor-kappa B pathway.Collectively,these data suggest that ketogenic diet may have a therapeutic potential in treating Alzheimer's disease by ameliorating the neurotoxicity associated with Aβ-induced inflammation.This study highlights the urgent need for further research into the use of ketogenic diet as a potential therapy for Alzheimer's disease.

Neurodegeneration:An early event of diabetic retinopathy

Diabetic retinopathy(DR) has been classically considered to be a microcirculatory disease of the retina caused by the deleterious metabolic effects of hyperglycemia per se and the metabolic pathways triggered by hyperglycemia.However,retinal neurodegeneration is already present before any microcirculatory abnormalities can be detected in ophthalmoscopic examination.In other words,retinal neurodegeneration is an early event in the pathogenesis of DR which predates and participates in the microcirculatory abnormalities that occur in DR.Therefore,the study of the mechanisms that lead to neurodegeneration will be essential to identify new therapeutic targets in the early stages of DR.Elevated levels of glutamate and the overexpression of the renin-angiotensin-system play an essential role in the neurodegenerative process that occurs in diabetic retina.Among neuroprotective factors,pigment epithelial derived factor,somatostatin and erythropoietin seem to be the most relevant and these will be considered in this review.Nevertheless,it should be noted that the balance between neurotoxic and neuroprotective factors rather than levels of neurotoxic factors alone will determine the presence or absence of retinal neurodegeneration in the diabetic eye.New strategies,based on either the delivery of neuroprotective agents or the blockade of neurotoxic factors,are currently being tested in experimental models and in clinical pilot studies.Whether these novel therapies will eventually supplement or prevent the need for laser photocoagulation or vitrectomy awaits the results of additional clinical research.

Targeting Therapy of Choroidal Neovascularization by Use of Polypeptide-and PEDF-loaded Immunoliposomes under Ultrasound Exposure

Pigment epithelium derived factor (PEDF) has been proven to be an effective drug for the treatment of choroidal neovascularization (CNV).However,the lack of ideal administration route is the biggest bottleneck preventing PEDF from wider clinical use.In this study,we developed a novel PEDF-carrying system which employed immuno-nano-liposomes (INLs) under ultrasound exposure.PEDF-loaded INLs were prepared by conjugating nanoliposomes to the peptide ATWLPPR specifically targeting the receptor-2 for vascular endothelial growth factor (VEGFR-2) and reversely encapsuling PEDF.RF/6A cells were incubated with PEDF-loaded INLs.CNV models of BN rats were injected with PEDF-loaded INLs.MTT assay was used to evaluate the cytotoxicity of the INLs on RF/6A cells.Flow cytometry was conducted to detect the apoptotic rate of cells.Laser scanning confocal microscopy was employed to observe the binding and transmitting process of PEDF-loaded INLs and to calculate the area of CNV in the rat model.The results showed that the PEDF-loaded INLs could exclusively bind to CNV but not to the normal choroidal vessels.The CNV area was significantly decreased in PEDF treatment groups in comparison with control group (P【0.05).Moreover,PEDF-loaded INLs exposed under ultrasound were more efficient in reducing the CNV area (P【0.05).It was concluded that INLs in combination with ultrasonic exposure can transmit PEDF into cytoplasma with high specificity and efficiency,which strengthens the inhibitory effects of PEDF on CNV and reduces its side effects.PEDF-loaded INLs possibly represent a new treatment paradigm for patients with ocular neovascularization.

Small Hairpin Loop RNA Targeting HIF-1α Down-regulates VEGF and Up-regulates PEDF in Human Retinal Pigment Epithelial Cells under Hypoxic Condition

The aim of this study was to explore the effect of small hairpin loop RNA （shRNA） silencing hypoxia-induced factor 1α （HIF-1α） gene on the expression of vascular endothelial growth factor （VEGF） and pigment epithelium derived factor （PEDF） in human retinal pigment epithelium （RPE） cells under hypoxic condition. Two target sites of HIF-1α mRNA were chosen and two kinds of shRNA were designed and synthesized against the target sites. Then the two kinds of shRNA were transfected into human RPE cells in vitro, respectively. These cells were cultured under hypoxic condition that was simulated by using 150 μmol/L CoCl2. The mRNA expressions of HIF-1α, VEGF and PEDF were tested by semi-quantitative reverse transcription PCR （RT-PCR）. The protein levels of HIF-1α, VEGF and PEDF were analyzed by Western blotting. After the two kinds of HIF-1α-specific shRNA were transfected into RPE cells respectively, the expression of HIF-1α mRNA and the levels of HIF-1α protein were decreased significantly in RPE cells under hypoxic condition. The expression of VEGF mRNA and the levels of protein significantly were also decreased. However, the levels of PEDF protein was significantly increased, but the expression of PEDF mRNA showed no significant changes. In conclusion, HIF-1α-specific shRNA can effectively silence the HIF-1α gene, and consequently down-regulate VEGF and up-regulate PEDF expression against hypoxia. These results reveal that HIF-1 is associated with posttranslational mechanism for down-regulating PEDF under hypoxia and provide an explanation for hypoxia-provoked increases in VEGF/PEDF ratios. These results also suggest that HIF-1 is one of the key cytokines to retinal neovascularization.

EXPRESSION OF PEDF mRNA AND PROTEIN IN NORMAL MOUSE RETINA AND EXPERIMENTAL CHOROIDAL NEOVASCULARIZATION TISSUES

Objective To study the expression of pigment epithelium derived factor (PEDF) in normal mouse retina and experimental choroidal neovascularization (CNV) tissues. Methods CNV mouse models were induced by diode laser. The expression of PEDF mRNA and protein in normal mouse retina and CNV tissues were detected by in situ hybridization and immunohistochemical study. Results In normal mouse retina, PEDF mRNA was observed in the ganglion cell layer, inner nuclear layer and RPE cell layer, and PEDF protein was observed mainly in the nerve fiber layer, ganglion cell layer, photoreceptor cell layer and RPE cell layer, and lower level expression of PEDF protein was also observed in the inner plexiform layer and outer plexiform layer. In CNV tissues, the expression of PEDF mRNA and protein was also observed. 3d and 1 week after photocoagulation, the expression level of PEDF was relatively lower, and increased following the development of CNV. The level was the highest 2 weeks after photocoagulation, then decreased at 3 weeks. Conclusion PEDF was expressed in different layers of retina and was obviously expressed in the CNV tissues induced by laser photocoagulation. These findings suggest that PEDF may participate and modulate the development of CNV.

Platelet derived growth factor and basic fibroblast growth factor immunolocalized in proliferative retinal diseases

Objective To study the role of platelet derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) in the development of proliferative vitreoretinopathy (PVR) Methods Immunohistochemical localization was performed on frozen sections of the epiretinal or subretinal membranes from 21 PVR patients using!monoclonal antibodies against PDGF and bFGF and the streptavidin peroxidase system Results PDGF was expressed in 15 of 21 specimens (71 4%), and bFGF was expressed in 14 specimens (66 7%) Different cell density was seen in different types of epiretinal membranes The cell density of vascular membranes induced by PDR and Eales disease was the highest (≥61 cells/field, ×1000); nonvascular membranes induced by PVR or traumatic PVR had moderate cell density (31-60 cells/field); and the macular membrane had the lowest cell density (≤30 cells/field) Conclusion The presents of PDGF and bFGF in PVR tissues suggest that PDGF and bFGF may play an important role in the development of PVR

Primary multiple extragastrointestinal stromal tumors of the omentum with different mutations of c-kit gene

The author reports a very rare case of sporadic primary multiple extragastrointestinal stromal tumors (EGISTs) of the omentum associated with different mutations of the exon 11 of the c-kit gene in a 75-year-old man with gastric cancer. During an operation for the cancer, two solid tumors (10 mm and 8 mm) were found in the omentum. Both tumors consisted of cellular spindle cells. Mitotic figures were two and three per 50 high power fields. The tumor cells were positive for KIT, CD34 and vimentin, but negative for desmin, S100 protein, α-smooth muscle actin and p53 protein. Ki67 labeling was 2% and 3%. The larger EGIST showed a deletion of codons 552-558 of exon 11 of the c-kit gene, while the smaller EGIST had a point mutation at codon 559 (GTT←GAT) in exon 11 of the c-kit gene. Exons 9, 13, and 17 of the c-kit gene, and exons 12 and 18 of the platelet derived growth factor receptor α genes showed no mutations. The case shows that sporadic multiple EGISTs can occur in the omentum.

Intermittent hypoxia with or without hypercapnia is associated with tumorigenesis by decreasing the expression of brain derived neurotrophic factor and miR-34a in rats

Background Very recent studies revealed that obstructive sleep apnoea （OSA） is a contributor of the increased incidence and mortality of cancer in humans,but mechanisms of how OSA promotes tumorigenesis remains largely unknown.We investigated whether intermittent hypoxia with and without hypercapnia plays a role in tumorigenesis.Methods First,Sprague-Dawley （SD） male rats （12 weeks old） were subjected to different hypoxia exposures：intermittent hypoxia and intermittent hypoxia with hypercapnia; continuous hypoxia and normal air.The systemic application of chronic fast rate hypoxia with or without hypercapnia mimicked severe OSA patients with apnoea/hypopnea index equivalent to 60 events per hour.Then routine blood tests were performed and the levels of brain derived neurotrophic factor （BDNF） and miR-34a were examined.Results In contrast to intermittent hypoxia with hypercapnia,both intermittent hypoxia and continuous hypoxia treatments caused significantly higher levels of haematology parameters than normoxia treatments.Compared to normoxia,intermittent hypoxia with hypercapnia exposure resulted in substantial decrease of serum BDNF and,miR-34a in the lower brainstem,while less pronounced results were found in intermittent hypoxia and continuous hypoxia exposure.Conclusions The exposure of intermittent hypoxia with or without hypercapnia,mimicking the situations in severe OSA patients,was associated with,or even promoted tumorigenesis.

Structure-activity Relationships of Vasorelaxing Effect of Polyarginine Oligopeptides

Based on the EDRF(endothelium derived relaxing factor)-like effects for polyarginine Arg-Arg-oH was selected as the lead compound and its derivatives Arg-Arg- OCH_3.Arg Arg-Arg-OH,HO-ArgCOCH_2CH_2COArg-OH,HO-ArgCOCH_2COArg-OH,were synthesized.These substances showed on bioassay various degrees of vasorelaxant activities. With protection for the C-terminal of Arg-Arg-OH with a methyl ester.the vasorelaxing ac- tivitv was decreased.In contrast.when the N-terminal of Arg-OH was protected with mal- onic acid or butane diacid.the biological activites were lower than those of Arg-Arg-OH due to the lowered metabolic rate.With protection of N-terminal of Arg-Arg-OH with L-Arg residue.Arg-Arg-Arg-OH was obtained,which showed a vasorelaxing activity better than that of Arg-Arg-OH.The bioactivities observed on the Wister's rats for the former com- pound become the experimental basis for prodrug design of EDRF.

Effects of Xinfeng Capsule(新风胶囊) on the Expression of Platelet Derived Growth Factor in Synovium of Adjuvant Arthritis Rats

Objective： To observe the effects of Xinfeng Capsule （新风胶囊, XFC） on platelet parameters in peripheral blood and expression of platelet derived growth factor （PDGF） in synovium of adjuvant arthritis （AA） rats. Methods： A total of 40 male Sprague-Dawley （SD） rats were randomized into 5 groups： normal control （NC）, AA model control （MC）, methotrexate （MTX） treatment, Tripterygium wilfordii polycoride tablet （TPT） treatment, and XFC treatment. Excluding the NC group, the AA model was induced by intracutaneous injection of 0.1 mL Freund＇s complete adjuvant in the right hind limb. Induction of AA and the effects of drug treatments were assessed by voix pedis swelling, arthritis index （AL） body mass, and the pathological changes of joints and cartilage with a light microscopy. Platelet parameters in peripheral blood were detected with an automated hematology analyzer. PDGF in synovium was detected with immunohistochemical methods and PDGF mRNA expression in synovium was detected with reverse transcription polymerase chain reaction. Results： Compared with the NC group, the MC group had significantly increased voix pedis swelling, AI, platelet （PLT） and plateletcrit （PCT） in peripheral blood and PDGF as well as PDGF mRNA in synovium （all P〈0.01） and the joint cartilage was also highly degenerated. Compared with the MC group, the 3 treated groups had significantly decreased voix pedis swelling, AI, PLT, PCT, PDGF, and PDGF mRNA （P〈0.01）. The body mass in the XFC group was significantly higher than those in MTX and TPT groups （P〈0.05）. The levels of PLT, PCT, PDGF, and PDGF mRNA in the XFC group showed a decreasing tendency with no significant difference compared with the M＇IX and TPT groups （P〉0,05）. PDGF and PDGF mRNA of AA rats were positively correlated with voix pedis swelling, AI, PLT, and PCT （P〈0.05 or P〈0.01）. Conclusions： The expression and biosynthesis of PDGF increase in the synovium of AA rats and correlate with voix pedis swelling, AI, PLT, and PCT. XFC can decrease the levels of PDGF, PDGF mRNA, PLT, and PCT, thereby mitigating inflammation induced by platelet activation and reducing voix pedis swelling and the AI in AA rats.

Clinical trial perspective for adult and juvenile Huntington's disease using genetically-engineered mesenchymal stem cells

Progress to date from our group and others indicate that using genetically-engineered mesenchymal stem cells（MSC） to secrete brain-derived neurotrophic factor（BDNF） supports our plan to submit an Investigational New Drug application to the Food and Drug Administration for the future planned Phase 1 safety and tolerability trial of MSC/BDNF in patients with Huntington＇s disease（HD）. There are also potential applications of this approach beyond HD. Our biological delivery system for BDNF sets the precedent for adult stem cell therapy in the brain and could potentially be modified for other neurodegenerative disorders such as amyotrophic lateral sclerosis（ALS）, spinocerebellar ataxia（SCA）, Alzheimer＇s disease, and some forms of Parkinson＇s disease. The MSC/BDNF product could also be considered for studies of regeneration in traumatic brain injury, spinal cord and peripheral nerve injury. This work also provides a platform for our future gene editing studies, since we will again use MSCs to deliver the needed molecules into the central nervous system.

KIT exon 11 codon 557/558 deletion/insertion mutations define a subset of gastrointestinal stromal tumors with malignant potential

AIM: To study the association of the frequency and pattern of KIT and PDGFRA mutations and clinicopathological factors in a group of patients with gastrointestinal stromal tumors (GIST). METHODS: Thirty patients with GIST were examined. Exons 9, 11, 13, and 17 of the KIT and exons 12 and 18 of the PDGFRA gene were analyzed for the presence of mutations by PCR amplification and direct sequencing. RESULTS: KIT or PDGFRA mutations were detected in 21 of the 30 patients (70%). Sixteen patients had mutations within KIT exon 11, three within KIT exon 9, and two within PDGFRA exon 18. GISTs with KIT exon 9 mutations were predominantly located in the small intestine, showed a spindle cell phenotype, and were assessed as potentially malignant. GISTs with KIT exon 11 mutations were located in the stomach and intestine, showed mainly a spindle cell phenotype, and were scored as potentially malignant (P < 0.05). Tumors with KIT exon 11 codon 557/558 deletion/insertion mutations were found to be associated with a potentially malignant clinical behaviour (P < 0.003). GISTs with PDGFRA mutations located in stomach showed a mixedcell phenotype and were classified as of very low or low moderate malignant potential. CONCLUSION: Determination of KIT and PDGFRA mutations should be additional parameters for the better prediction of GISTs clinical behaviour. Tumors with deletion/insertion mutations affecting codons 557/558 of the KIT gene seem to represent a distinct subset of malignant GISTs.

Amelanotic malignant melanoma of the esophagus:Report of two cases with immunohistochemical and molecular genetic study of KIT and PDGFRA

The author reports herein two cases of amelanotic malignant melanoma of the esophagus. Case 1 is an 87-year-old woman who was admitted to our hospital because of nausea and vomiting. Endoscopic examination revealed an ulcerated tumor of the distal esophagus, and a biopsy was taken. The biopsy showed malignant polygonal and spindle cells. No melanin pigment was recognized. Immunohistochemically, the tumor cells were positive for melanosome （HMB45）, S100 protein, KIT and Platelet derived growth factor receptor-α （PDG- FRA）. The patient was treated by chemotherapy and radiation, but died of systemic metastasis 12 mo after the presentation. Case 2 is a 56-year-old man presenting with dysphagia. Endoscopic examination revealed a polypoid tumor in the middle esophagus, and a biopsy was obtained. The biopsy showed malignant spindle cells without melanin pigment. Immunohistochemically, the tumor cells were positively labeled for melanosome,S100 protein, KIT and PDGFRA. The patient refused operation, and was treated by palliative chemotherapy and radiation. He died of metastasis 7 mo aEer the admission. In both cases, molecular genetic analyses of gene （exons 9, 11, 13 and 17） and PDGFRA gene （exons 12 and 18） were performed by the PCR direct sequencing method, which showed no mutations of KIT and PDGFRA genes. This is the first report of esophageal malignant melanoma with an examination of the expression of KIT and PDGFRA and the mutational status of K/T and PDGFRA genes.