Compartmentalized metabolism supports midgestation mammalian development.

Mammalian embryogenesis requires rapid growth and proper metabolic regulation1. Midgestation features increasing oxygen and nutrient availability concomitant with fetal organ development2,3. Understanding how metabolism supports development requires approaches to observe metabolism directly in model organisms in utero. Here we used isotope tracing and metabolomics to identify evolving metabolic programmes in the placenta and embryo during midgestation in mice. These tissues differ metabolically throughout midgestation, but we pinpointed gestational days (GD) 10.5-11.5 as a transition period for both placenta and embryo. Isotope tracing revealed differences in carbohydrate metabolism between the tissues and rapid glucose-dependent purine synthesis, especially in the embryo. Glucose's contribution to the tricarboxylic acid (TCA) cycle rises throughout midgestation in the embryo but not in the placenta. By GD12.5, compartmentalized metabolic programmes are apparent within the embryo, including different nutrient contributions to the TCA cycle in different organs. To contextualize developmental anomalies associated with Mendelian metabolic defects, we analysed mice deficient in LIPT1, the enzyme that activates 2-ketoacid dehydrogenases related to the TCA cycle4,5. LIPT1 deficiency suppresses TCA cycle metabolism during the GD10.5-GD11.5 transition, perturbs brain, heart and erythrocyte development and leads to embryonic demise by GD11.5. These data document individualized metabolic programmes in developing organs in utero.

A pathogenic UFSP2 variant in an autosomal recessive form of pediatric neurodevelopmental anomalies and epilepsy.

PURPOSE: Neurodevelopmental disabilities are common and genetically heterogeneous. We identified a homozygous variant in the gene encoding UFM1-specific peptidase 2 (UFSP2), which participates in the UFMylation pathway of protein modification. UFSP2 variants are implicated in autosomal dominant skeletal dysplasias, but not neurodevelopmental disorders. Homozygosity for the variant occurred in eight children from four South Asian families with neurodevelopmental delay and epilepsy. We describe the clinical consequences of this variant and its effect on UFMylation. METHODS: Exome sequencing was used to detect potentially pathogenic variants and identify shared regions of homozygosity. Immunoblotting assessed protein expression and post-translational modifications in patient-derived fibroblasts. RESULTS: The variant (c.344T>A; p.V115E) is rare and alters a conserved residue in UFSP2. Immunoblotting in patient-derived fibroblasts revealed reduced UFSP2 abundance and increased abundance of UFMylated targets, indicating the variant may impair de-UFMylation rather than UFMylation. Reconstituting patient-derived fibroblasts with wild-type UFSP2 reduced UFMylation marks. Analysis of UFSP2's structure indicated that variants observed in skeletal disorders localize to the catalytic domain, whereas V115 resides in an N-terminal domain possibly involved in substrate binding. CONCLUSION: Different UFSP2 variants cause markedly different diseases, with homozygosity for V115E causing a severe syndrome of neurodevelopmental disability and epilepsy.

Metabolic impact of pathogenic variants in the mitochondrial glutamyl-tRNA synthetase EARS2.

Glutamyl-tRNA synthetase 2 (encoded by EARS2) is a mitochondrial aminoacyl-tRNA synthetase required to translate the 13 subunits of the electron transport chain encoded by the mitochondrial DNA. Pathogenic EARS2 variants cause combined oxidative phosphorylation deficiency, subtype 12 (COXPD12), an autosomal recessive disorder involving lactic acidosis, intellectual disability, and other features of mitochondrial compromise. Patients with EARS2 deficiency present with variable phenotypes ranging from neonatal lethality to a mitigated disease with clinical improvement in early childhood. Here, we report a neonate homozygous for a rare pathogenic variant in EARS2 (c.949G>T; p.G317C). Metabolomics in primary fibroblasts from this patient revealed expected abnormalities in TCA cycle metabolites, as well as numerous changes in purine, pyrimidine, and fatty acid metabolism. To examine genotype-phenotype correlations in COXPD12, we compared the metabolic impact of reconstituting these fibroblasts with wild-type EARS2 versus four additional EARS2 variants from COXPD12 patients with varying clinical severity. Metabolomics identified a group of signature metabolites, mostly from the TCA cycle and amino acid metabolism, that discriminate between EARS2 variants causing relatively mild and severe COXPD12. Taken together, these findings indicate that metabolomics in patient-derived fibroblasts may help establish genotype-phenotype correlations in EARS2 deficiency and likely other mitochondrial disorders.

Inhibition of acid-sensing ion channel 1a in hepatic stellate cells attenuates PDGF-induced activation of HSCs through MAPK pathway.

Acid-sensing ion channels (ASICs), a group of Na(+)-selective and Ca(2+)-permeant ligand-gated cation channels, can be transiently activated by extracellular acid. Among seven subunits of ASICs, acid-sensing ion channel 1a (ASIC1a), which is responsible for Ca(2+) transportation, is elevated in response to inflammation, tumor, and ischemic injury in central nervous system and non-neuronal tissues. In this study, we demonstrated for the first time the presence of ASIC1a in rat liver and hepatic stellate cells (HSCs). Furthermore, the expression of ASIC1a was increased in primary HSCs and liver tissues of CCl4-treated rats, suggesting that ASIC1a may play certain role in liver fibrosis. Interestingly, we identified that the level of ASIC1a was significantly elevated in response to platelet-derived growth factor (PDGF) induction in a time- and dose-dependent manner. It was also established that Ca(2+)-transporting ASIC1a was involved in acid-induced injury of different cell types. Moreover, inhibition or silencing of ASIC1a was able to inhibit PDGF-induced pro-fibrogenic effects of activated rat HSCs, including cell activation, de novo synthesis of extracellular matrix components through mitogen-activated protein kinase signaling pathway. Collectively, our studies identified that ASIC1a was expressed in rat liver and HSCs and provided a strong evidence for the involvement of the ASIC1a in the progression of hepatic fibrosis.

Role of interleukin-22 in liver diseases.

INTRODUCTION: Interleukin (IL)-22, originally referred to as IL-TIF for IL-10-related T cell-derived inducible factor, is a member of the IL-10-like cytokine family. IL-22 is highly expressed by Th17 cells and is tightly linked to chronic inflammation, including inflammatory bowel disease and local intestinal inflammation among others. MATERIALS AND METHODS: A PubMed and Web of Science databases search was performed for studies providing evidences on the role of IL-22 in liver diseases. CONCLUSION: IL-22 plays an important role in ameliorating liver injury in many rodent models by targeting hepatocytes that express high levels of IL-22 receptor 1 and IL-10 receptor 2. This review concisely summarizes the role of IL-22 in the development progression of liver disease of different etiologies. It is focused mainly on the IL-22 intracellular signaling and its influence on liver diseases.

Inhibition of ASICs reduces rat hepatic stellate cells activity and liver fibrosis: an in vitro and in vivo study.

Hepatic fibrosis is a chronic inflammation-associated disease, which is involved in the infiltration of inflammatory cells and releasing of proinflammatory cytokines. In the pathological process, protons are released by damaged cells and acidosis is considered to play a critical role in cell injury. Although the underlying mechanism (s) remain ill-defined, ASICs (acid-sensing ion channels) are assumed to be involved in this process. The diuretic, amiloride, is neuroprotective in models of cerebral ischemia, a property attributable to the inhibition of central ASICs by the drug. However, the effect of inhibition of ASICs by amiloride in the liver fibrotic process remains unclear. We found that amiloride (25, 50, or 100 µM) could restrain acid-induced HSCs at pH6 in vitro. In vivo experiments showed that amiloride could significantly alleviate liver injury, decreasing levels of profibrogenic cytokines, collagen deposition, and reducing pathological tissue damage. In summary, amiloride inhibits hepatic fibrosis in vivo and in vitro, which is probably associated with the downregulation of ASICs.

Electron transport chain inhibition increases cellular dependence on purine transport and salvage.

Mitochondria house many metabolic pathways required for homeostasis and growth. To explore how human cells respond to mitochondrial dysfunction, we performed metabolomics in fibroblasts from patients with various mitochondrial disorders and cancer cells with electron transport chain (ETC) blockade. These analyses revealed extensive perturbations in purine metabolism, and stable isotope tracing demonstrated that ETC defects suppress de novo purine synthesis while enhancing purine salvage. In human lung cancer, tumors with markers of low oxidative mitochondrial metabolism exhibit enhanced expression of the salvage enzyme hypoxanthine phosphoribosyl transferase 1 (HPRT1) and high levels of the HPRT1 product inosine monophosphate. Mechanistically, ETC blockade activates the pentose phosphate pathway, providing phosphoribosyl diphosphate to drive purine salvage supplied by uptake of extracellular bases. Blocking HPRT1 sensitizes cancer cells to ETC inhibition. These findings demonstrate how cells remodel purine metabolism upon ETC blockade and uncover a new metabolic vulnerability in tumors with low respiration.

High-throughput functional screen identifies YWHAZ as a key regulator of pancreatic cancer metastasis.

Pancreatic cancer is a leading cause of cancer death due to its early metastasis and limited response to the current therapies. Metastasis is a complicated multistep process, which is determined by complex genetic alterations. Despite the identification of many metastasis-related genes, distinguishing the drivers from numerous passengers and establishing the causality in cancer pathophysiology remains challenging. Here, we established a high-throughput and piggyBac transposon-based genetic screening platform, which enables either reduced or increased expression of chromosomal genes near the incorporation site of the gene search vector cassette that contains a doxycycline-regulated promoter. Using this strategy, we identified YWHAZ as a key regulator of pancreatic cancer metastasis. We demonstrated that functional activation of Ywhaz by the gene search vector led to enhanced metastatic capability in mouse pancreatic cancer cells. The metastasis-promoting role of YWHAZ was further validated in human pancreatic cancer cells. Overexpression of YWHAZ resulted in more aggressive metastatic phenotypes in vitro and a shorter survival rate in vivo by modulating epithelial-to-mesenchymal transition. Hence, our study established a high-throughput screening method to investigate the functional relevance of novel genes and validated YWHAZ as a key regulator of pancreatic cancer metastasis.

Identification of potential prognostic biomarkers among gene models for coiled-coil domain-containing family members in hepatocellular carcinoma elucidates their influence on the hypoxia pathway and immune microenvironment.

Background: The family of coiled-coil domain-containing (CCDC) proteins participates in a wide range of physiological functions and plays a pivotal role in governing the invasion and metastasis of malignant tumor cells. Nonetheless, the precise mechanism governing the interaction among the immune microenvironment, hypoxia pathway, and proliferation in hepatocellular carcinoma (HCC) remains elusive. In this study, our objective was to identify the prognostic significance of CCDC family genes in HCC. Methods: We conducted an analysis of RNA-seq data from HCC patients sourced from The Cancer Genome Atlas (TCGA) database. Our analysis involved comparing the expression profiles of 168 CCDC family genes between tumor and normal tissues to identify differentially expressed genes (DEGs). The prognostic value of these genes was verified using overall survival (OS) data from TCGA-LIHC patients, employing Univariate and multivariate Cox proportional hazards regression models and Kaplan-Meier plots. Subsequently, we constructed a prognostic signature known as the CCDC score and validated it using additional datasets (ICGC-LIRI-JP and GSE14520). Additionally, we performed functional enrichment analysis and conducted an assessment of the tumor immune microenvironment (TIME). Results: We identified 34 DEGs of the CCDC family. Among them, six DEGs (CCDC6/22/51/59/132/134) were upregulated and associated with poor prognosis. Higher CCDC score was an independent predictor of poor OS in TCGA-HCC patients (P<0.001, HR =2.37), which was validated in the ICGC-LIRI-JP (P=0.021, HR =2.15) and GSE14520 (P=0.002, HR =2.23) datasets. Functional enrichment analysis showed that hypoxia pathway genes were enriched in the high CCDC score group. Furthermore, immune microenvironment analysis demonstrated that high CCDC score was associated with a suppressed TIME caused by the extrinsic immune escape. Conclusions: The CCDC score, derived from six CCDC genes, exhibits remarkable expression levels in liver cancer and holds promise as an independent prognostic indicator. Our bioinformatics analysis revealed a high CCDC score is strongly associated with activation of the hypoxia pathway and an immunosuppressive tumor microenvironment in HCC. This profound finding may serve as a cornerstone for innovative targeted drug therapies and pave the way for further investigations into the underlying mechanisms of CCDC-related carcinogenesis in liver cancer.

Electron transport chain inhibition increases cellular dependence on purine transport and salvage.

Cancer cells reprogram their metabolism to support cell growth and proliferation in harsh environments. While many studies have documented the importance of mitochondrial oxidative phosphorylation (OXPHOS) in tumor growth, some cancer cells experience conditions of reduced OXPHOS in vivo and induce alternative metabolic pathways to compensate. To assess how human cells respond to mitochondrial dysfunction, we performed metabolomics in fibroblasts and plasma from patients with inborn errors of mitochondrial metabolism, and in cancer cells subjected to inhibition of the electron transport chain (ETC). All these analyses revealed extensive perturbations in purine-related metabolites; in non-small cell lung cancer (NSCLC) cells, ETC blockade led to purine metabolite accumulation arising from a reduced cytosolic NAD + /NADH ratio (NADH reductive stress). Stable isotope tracing demonstrated that ETC deficiency suppressed de novo purine nucleotide synthesis while enhancing purine salvage. Analysis of NSCLC patients infused with [U- 13 C]glucose revealed that tumors with markers of low oxidative mitochondrial metabolism exhibited high expression of the purine salvage enzyme HPRT1 and abundant levels of the HPRT1 product inosine monophosphate (IMP). ETC blockade also induced production of ribose-5' phosphate (R5P) by the pentose phosphate pathway (PPP) and import of purine nucleobases. Blocking either HPRT1 or nucleoside transporters sensitized cancer cells to ETC inhibition, and overexpressing nucleoside transporters was sufficient to drive growth of NSCLC xenografts. Collectively, this study mechanistically delineates how cells compensate for suppressed purine metabolism in response to ETC blockade, and uncovers a new metabolic vulnerability in tumors experiencing NADH excess.

An interactive web application for exploring human plasma and fibroblast metabolomics data from patients with inborn errors of metabolism.

Metabolomic profiling is instrumental in understanding the systemic and cellular impact of inborn errors of metabolism (IEMs), monogenic disorders caused by pathogenic genomic variants in genes involved in metabolism. This study encompasses untargeted metabolomics analysis of plasma from 474 individuals and fibroblasts from 67 subjects, incorporating healthy controls, patients with 65 different monogenic diseases, and numerous undiagnosed cases. We introduce a web application designed for the in-depth exploration of this extensive metabolomics database. The application offers a user-friendly interface for data review, download, and detailed analysis of metabolic deviations linked to IEMs at the level of individual patients or groups of patients with the same diagnosis. It also provides interactive tools for investigating metabolic relationships and offers comparative analyses of plasma and fibroblast profiles. This tool emphasizes the metabolic interplay within and across biological matrices, enriching our understanding of metabolic regulation in health and disease. As a resource, the application provides broad utility in research, offering novel insights into metabolic pathways and their alterations in various disorders.

Substituent effects on photosensitized splitting of thymine cyclobutane dimer by an attached indole.

In chromophore-containing cyclobutane pyrimidine dimer (CPD) model systems, solvent effects on the splitting efficiency may depend on the length of the linker, the molecular conformation, and the oxidation potential of the donor. To further explore the relationship between chromophore structure and splitting efficiency, we prepared a series of substituted indole-T< >T model compounds 2 a-2 g and measured their splitting quantum yields in various solvents. Two reverse solvent effects were observed: an increase in splitting efficiency in solvents of lower polarity for models 2 a-2 d with an electron-donating group (EDG), and vice versa for models 2 e-2 g with an electron-withdrawing group (EWG). According to the Hammett equation, the negative value of the slope of the Hammett plot indicates that the indole moiety during the T< >T-splitting reaction loses negative charge, and the larger negative value implies that the repair reaction is more sensitive to substituent effects in low-polarity solvents. The EDGs of the models 2 a-2 d can delocalize the charge-separated state, and low-polarity solvents make it more stable, which leads to higher splitting efficiency in low-polarity solvents. Conversely, the EWGs of models 2 e-2 g favor destabilization of the charge-separated state, and high-polarity solvents decrease the destabilization and hence lead to more efficient splitting in high-polarity solvents.

Predictive value of early kinetics of ctDNA combined with cfDNA and serum CEA for EGFR-TKI treatment in advanced non-small cell lung cancer.

BACKGROUND: Circulating tumor DNA (ctDNA) has made a breakthrough as an early biomarker in operable early-stage cancer patients. However, the function of ctDNA combined with cell-free DNA (cfDNA) as a predictor in advanced non-small cell lung cancer (NSCLC) remains unknown. Here, we explored its potential as a biomarker for predicting the efficacy of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) in patients with advanced NSCLC. METHODS: A retrospective analysis was undertaken. Plasma collected from 51 patients with advanced NSCLC prior to and serially after starting treatment with EGFR-TKIs was analyzed by next-generation sequencing (NGS). The performance of ctDNA, cfDNA, and combining ctDNA with cfDNA were evaluated for their ability to predict survival outcomes. RESULTS: Patients with early undetectable ctDNA and increasing cfDNA had a markedly better progression-free survival (PFS) (p < 0.001) and overall survival (OS) (p = 0.001) than those with early detectable ctDNA and decreasing cfDNA. Patients with early ctDNA clearance were more likely to have the ctDNA persistent clearance (p = 0.006). The early clearance rate of ctDNA in the normal carcinoembryonic antigen (CEA) group was significantly higher than in the low and high groups (p = 0.028). Patients with greater CEA decline had a higher early clearance rate of ctDNA than those with minor CEA change (p = 0.016). CONCLUSIONS: We based this study on ctDNA and cfDNA, explored its prognostic predictive ability, and combined CEA to monitor EGFR-TKI efficacy. This study may provide new perspectives and insights into the precise treatment strategies for NSCLC patients.

Functional Assessment of Lipoyltransferase-1 Deficiency in Cells, Mice, and Humans.

Inborn errors of metabolism (IEMs) link metabolic defects to human phenotypes. Modern genomics has accelerated IEM discovery, but assessing the impact of genomic variants is still challenging. Here, we integrate genomics and metabolomics to identify a cause of lactic acidosis and epilepsy. The proband is a compound heterozygote for variants in LIPT1, which encodes the lipoyltransferase required for 2-ketoacid dehydrogenase (2KDH) function. Metabolomics reveals abnormalities in lipids, amino acids, and 2-hydroxyglutarate consistent with loss of multiple 2KDHs. Homozygous knockin of a LIPT1 mutation reduces 2KDH lipoylation in utero and results in embryonic demise. In patient fibroblasts, defective 2KDH lipoylation and function are corrected by wild-type, but not mutant, LIPT1 alleles. Isotope tracing reveals that LIPT1 supports lipogenesis and balances oxidative and reductive glutamine metabolism. Altogether, the data extend the role of LIPT1 in metabolic regulation and demonstrate how integrating genomics and metabolomics can uncover broader aspects of IEM pathophysiology.

Elimination of matrix effect and simultaneous determination of multi-components in complex systems by matrix coefficient non-linearity multivariate calibration based on single point response signals.

In order to deal with the matrix effect in the simultaneous determination of multi-components in a complex system, we have developed a novel method named matrix coefficient multivariate calibration method (MCMCM) for simultaneously determining n analytes in complex systems. The calibration models of n analytes, which are based on the experimental data of known samples, are first transformed into n linear equations, and then the equations are solved to obtain matrix calibration coefficients of the analytes in congeneric samples. In this way, the concentrations of n analytes in the unknown sample could be obtained easily and simultaneously by solving another n-variate linear equations with the help of the matrix calibration coefficients obtained-above. The method proposed in this work has been tested by voltammetry and atomic absorption spectrometry (AAS) with satisfactory results. On determining the elements such as Cu, Pb, Cd, Ni, Zn, Fe, Mn, Co, Ca, Mg, etc. in synthetic samples, the relative standard deviations (RSDs) of the results were 0.91 - 4.5%, and the recoveries were 95.8 - 105%. For actual samples, the RSDs and the recoveries were 1.5 - 6.9 and 92.0 - 110%, respectively.

Identification of the metastasis potential and its associated genes in melanoma multinucleated giant cells using the PHA-ECM830 fusion method.

Malignant melanoma causes skin cancer with high rates of mortality. Multinucleated giant cells (MGCs) are frequently observed in tumor pathological analysis, especially in metastasized sites, and are related to poor prognosis. However, the role of MGCs in melanoma development and metastasis is currently unknown. In the present study, we obtained melanoma MGCs (M-MGCs) in vitro using the modified phytohaemagglutinin (PHA)-ECM830 electronic fusion method (fusion efficiency was significantly enhanced by adding PHA to agglutinate cells before electronic fusion). We found that M-MGCs showed decreased proliferation potential but increased pulmonary metastasis ability relative to the parental B16-F10 cells. Microarray and bioinformatics analysis showed that ß-tubulin gene group was significantly upregulated in MMGCs. A member of this gene group, TUBB2B, exhibited significantly enhanced expression, indicating that it may play an important role in melanoma metastasis. Our results provide novel insights into the properties of melanoma and they could contribute towards the design of new strategies for rapid diagnosis and treatment of this cancer.

Simulated microgravity alters the metastatic potential of a human lung adenocarcinoma cell line.

Simulated microgravity (SM) has been implicated in affecting diverse cellular pathways. Although there is emerging evidence that SM can alter cellular functions, its effect in cancer metastasis has not been addressed. Here, we demonstrate that SM inhibits migration, gelatinolytic activity, and cell proliferation of an A549 human lung adenocarcinoma cell line in vitro. Expression of antigen MKI67 and matrix metalloproteinase-2 (MMP2) was reduced in A549 cells stimulated by clinorotation when compared with the 1×g control condition, while overexpression of each gene improves ability of proliferation and migration, respectively, under SM conditions. These findings suggest that SM reduced the metastatic potential of human lung adenocarcinoma cells by altering the expression of MKI67 and MMP2, thereby inhibiting cell proliferation, migration, and invasion, which may provide some clues to study cancer metastasis in the future.

Antidepressant-like effect of resveratrol: involvement of antioxidant effect and peripheral regulation on HPA axis.

This study focused on exploring the antidepressant potential of resveratrol (RES) and its possible mechanisms of action. Cell injury was induced by corticosterone (CORT) and detected through cell viability and contents of lactate dehydrogenase (LDH) and malonaldehyde (MDA). A rat model of depression was established through 3weeks of consecutive chronic unpredictable mild stress (CUMS), and both the depression-like behaviors and the activity of the hypothalamic-pituitary-adrenal (HPA) axis were tested. Apart from the inhibitory effect on MDA production in vitro and in vivo, the results showed that RES (10(-10)mol/L to 10(-5)mol/L) could significantly increase the cell viability and decrease the LDH activity and that RES (15mg/kg) treatment could alleviate the depression-like behavior of CUMS rats, as indicated by increased sucrose preference and decreased immobility in forced swimming test and tail suspension test. Rats that received RES treatment displayed a reduction of serum CORT, suggesting that RES affected the hyperactivity of the HPA axis in CUMS rats. However, RES did not affect the expression of corticotropin-releasing hormone (CRH) mRNA in the hypothalamus of CUMS rats. In summary, our results demonstrated that in addition to its widely known antioxidant properties, RES also has antidepressant-like effects, and suggested that the underlying mechanism might involve its peripheral effect on the regulation of the HPA axis.

Anti-tumor effect of 4-Amino-2-Trifluoromethyl-Phenyl Retinate on human breast cancer MCF-7 cells via up-regulation of retinoid receptor-induced gene-1.

4-Amino-2-Trifluoromethyl-Phenyl Retinate (ATPR) is one of the retinoid derivatives designed and synthesized in our team. In this paper, we explored the potential anti-tumor effects of ATPR in breast cancer. Here we found that ATPR showed remarkable anti-proliferative effects in a dose- and time-dependent manner, caused cell cycle arrest in the G0/G1 phase and significantly increased the expression of retinoid receptor-induced gene-1 (RRIG1). ATPR decreased the expression of phosphorylation-ERK (p-ERK) and increased the expression of estrogen receptor ß (ERß) and phosphorylation-p38 (p-p38). Following RRIG1 knockdown by RNAi interference, we found that the changes of ERß, p-ERK and p-p38 induced by ATPR were both depressed. Our data suggest that ATPR could inhibit the proliferation and induce differentiation of MCF-7 cells via mediating the expression of RRIG1.

Fusion between tumor cells enhances melanoma metastatic potential.

PURPOSE: Malignant melanoma, characterized by early distant metastasis to the lungs and brain, is a leading cause of mortality related to skin cancer. Cell fusion and the subsequent aneuploidy, commonly observed in melanoma, are associated with poor prognosis. However, the pathological consequences of cell fusion in melanoma remain unknown. Therefore, the present study aims to investigate the pathological consequences of cell fusion in melanoma and the mechanism of melanoma metastasis. METHODS: Phytohemagglutinin-polyethylene glycol (PHA-PEG) fusion method was developed for the fusion of tumor cells. Melanoma cells were fused through the improved PHA-PEG fusion method and obtained by fluorescence-activated cell sorting. DNA content was analyzed through flow cytometry. Cell proliferation rate was detected by cell culture in vitro, and the cell number was counted daily. To detect the tumor growth rate in vivo, cells were injected subcutaneously and the tumor volumes were measured using a vernier caliper. To analyze the tumor metastatic potential, cells were injected intravenously, and the collected lung-metastasis samples were weighed by an electronic balance and the surface nodules were counted. RESULTS: We established an improved phytohemagglutinin-polyethylene glycol fusion method and successfully obtained stable melanoma tumor-tumor cell fusion hybrids. Cell size, DNA content, and chromosome numbers of the fusion hybrids were approximately twice those of the parents. The metastatic potential of the fusion hybrids was dramatically enhanced, in contrast to their proliferation rate. Their metastasis was specific to the lungs. CONCLUSIONS: We developed a highly efficient cell fusion method that can be applied in many fields, particularly cancer research. Our study has proven that tumor-tumor cell fusion hybrids in melanoma can acquire enhanced and specific metastatic potential. Thus, blockage of cell fusion may be a new strategy for melanoma metastasis therapy.