Long noncoding RNA SNHG14 promotes breast cancer cell proliferation and invasion via sponging miR-193a-3p.

Since this article has been suspected of research misconduct and the corresponding authors did not respond to our request to prove originality of data and figures, "Long noncoding RNA SNHG14 promotes breast cancer cell proliferation and invasion via sponging miR-193a-3p, by S.-D. Xie, C. Qin, L.-D. Jin, Q.-C. Wang, J. Shen, J.-C. Zhou, Y.-X. Chen, A.-H. Huang, W.-H. Zhao, L.-B. Wang, published in Eur Rev Med Pharmacol Sci 2019; 23 (6): 2461-2468. DOI: 10.26355/eurrev_201903_17393. PMID: 30964172" has been withdrawn. The Publisher apologizes for any inconvenience this may cause. https://www.europeanreview.org/article/17393.

Relationship between the MAPK/ERK pathway and neurocyte apoptosis after cerebral infarction in rats.

OBJECTIVE: The aim of this study was to explore the relationship between the mitogen-activated protein kinase (MAPK)/extracellular regulated protein kinase (ERK) pathway and neurocyte apoptosis after cerebral infarction in rats. MATERIALS AND METHODS: Neural stem cells were isolated from rats by establishing the cerebral infarction model and sham model. Isolated cells were cultured in complete culture medium in vitro. Real-time quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) was used to detect the messenger ribonucleic acid (mRNA) expression of ERK1 and ERK2 in the MARK pathway. Western blotting was applied to examine the activation of the MAPK/ERK pathway and neuron-specific markers. The expression of neuron-specific enolase (NSE) was detected via immunofluorescence. Cell activity and apoptosis were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry, respectively. RESULTS: The mRNA expressions of ERK1 and ERK2 in neural stem cells increased in a time-dependent manner after cerebral infarction in rats. The expressions of ERK1, ERK2, cyclin D1, Nestin, NSE and glial fibrillary acidic-protein (GFAP) in neural stem cells were significantly decreased after being treated with SCH772984. Cell activity, proliferation and differentiation were markedly inhibited. However, cleaved-caspase 3 protein and apoptosis rate were remarkably increased. CONCLUSIONS: The MAPK/ERK pathway seriously affects neurocyte apoptosis after cerebral infarction in rats. When the MAPK/ERK pathway is inhibited, neurocyte apoptosis is remarkably increased after cerebral infarction in rats.

Long noncoding RNA SNHG14 promotes breast cancer cell proliferation and invasion via sponging miR-193a-3p.

OBJECTIVE: Breast cancer (BC) is one of the most ordinary fatal cancers. Recent studies have identified the vital role of long noncoding RNAs (lncRNAs) in the development and progression of BC. In this research, lncRNA SNHG14 was studied to identify how it functioned in the development and metastasis of BC. PATIENTS AND METHODS: SNHG14 expression of tissues was detected by Real Time-quantitative Polymerase Chain Reaction (RT-qPCR) in 50 paired patients with BC. And cell proliferation assay, colony formation assay, and transwell assay were enrolled to observe the biological behavior changes of BC cells through gain or loss of SNHG14. In addition, luciferase assays and RNA immunoprecipitation assay (RIP) were performed to discover the potential targets of SNHG14 in BC cells. RESULTS: SNHG14 expression level of BC samples was higher than that of adjacent ones. Besides, cell growth ability and cell invaded ability of BC cells were inhibited after SNHG14 was silenced, while cell growth ability and cell invaded ability of BC cells were promoted after SNHG14 was overexpressed. In addition, miR-193a-3p was upregulated after silence of SNHG14 in BC cells, while miR-193a-3p was downregulated after overexpression of SNHG14 in BC cells. Furthermore, luciferase assays and RNA immunoprecipitation assay (RIP) showed that miR-193a-3p was a direct target of SNHG14 in BC. CONCLUSIONS: Our study uncovers a new oncogene in BC and suggests that SNHG14 could enhance BC cell proliferation and invasion via sponging miR-193a-3p, which provided a novel therapeutic target for BC patients.

Clostridium butyricum promotes intestinal motility by regulation of TLR2 in interstitial cells of Cajal.

OBJECTIVE: Clostridium butyricum (C. butyricum) as a probiotic has been reported to have an important role in the pathogenesis of gastrointestinal diseases. However, the effects of C. butyricum on regulation of intestinal motility of ulcerative colitis (UC) remain unclear. Our study aimed to explore the cross-regulation effect of C. butyricum and toll-like receptor 2 (TLR-2) on UC. MATERIALS AND METHODS: Interstitial cells of Cajal (ICCs) were treated by C. butyricum for 2 h, the mRNA and protein levels of TLR-2, IL-6, and IL-8 were detected by RT-qPCR and Western blot. Then, TLR2-specific small interfering RNA (si-TLR2) was transfected into ICCs, and the relative expressions of IL-6 and IL-8, SCF, cell viability, ghrelin, SP, and ET were measured by RT-qPCR, Western blot, CCK-8, and ELISA. Besides, the signal pathways of NF-κB and JNK were determined by Western blot. RESULTS: C. butyricum significantly increased TLR2, IL-6, and IL-8 expressions in ICCs. However, TLR2 silence alleviated C. butyricum-induced IL-6 and IL-8 expressions. Moreover, TLR2 silence significantly inhibited C. butyricum-induced cell viability in ICCs. Additionally, C. butyricum significantly increased SCF expression and promoted the secretion of ghrelin and SP. However, a significant reduction in the levels of SCF, ghrelin, and SP was evident in the silence of TLR2 expression. Besides, TLR2 silence reduced C. butyricum-activation NF-κB and JNK signal pathways in ICCs. CONCLUSIONS: These findings revealed that C. butyricum promoted intestinal motility by regulation of TLR2 in ICCs, which contributed to understand the molecular mechanisms of C. butyricum on UC.

[Elevated Fas expression is related to increased apoptosis of circulating CD8(+)T cell in patients with hepatocellular carcinoma].

Objective: To investigate the mechanism of apoptosis of CD8(+)T lymphocyte in peripheral blood of patients with hepatocellular carcinoma (HCC). Methods: The proportion and apoptosis of peripheral blood CD8(+)T lymphocytes in 30 healthy controls, 30 patients with cirrhosis and 60 HCC patients were detected by Flow cytometry, and the expression of Fas on the surface of CD8(+)T lymphocytes was reported. The differences between groups were compared using independent sample t-test, and data of variance were tested with Mann-Whitney U non-parametric test, P < 0.05 was considered statistically significant. Results: The proportion of CD8(+)T lymphocytes in peripheral blood of patients with HCC was 26.4% ± 9.2%, higher than that of 24.5% ± 7.1% in cirrhosis (t = 0.783, P = 0.489), and and healthy control 19.7% ± 4.7% (t = 2.920, P = 0.004). The proportion of apoptotic CD8(+)T lymphocytes in peripheral blood of HCC patients was 25.3% ± 6.5%, of the total CD8(+)T lymphocytes, which was significantly higher than that of healthy controls 12.1%±6.5% (t = 7.555, P < 0.001) and cirrhotic 13.6% ± 5.8% (t = 5.213, P < 0.001), the differences were statistically significant. The proportion of Fas(+)CD8(+)T lymphocytes in the HCC group was 62.2% ± 18.5%, higher than that in the healthy control group 42.6%±16.5% (t = 4.127, P < 0.001) and 46.1% ± 14.5% (t = 2.561, P < 0.01)of the cirrhosis group, the differences were statistically significant. Fas expression was positively correlated with the apoptosis of CD8(+)T lymphocytes (r (2) = 0.113, P < 0.05). Conclusion: The proportion of CD8(+)T lymphocytes in peripheral blood of patients with HCC is higher than that of healthy controls, but the proportion of CD8(+)T lymphocyte apoptosis based on Fas/FasL pathway increased, which may be an important mechanism for tumor cell immune escape.

[Analysis of sonographic characteristics of thyroid nodules diagnosed as false positive or negative results in shear wave elastography].

Objective:In order to improve diagnostic accuracy, we study the characteristics of two dimensional ultrasound and shear wave elastography in the diagnosis of false negative or false positive thyroid nodules by shear wave elastography.Method:One hundred and eighty-nine nodules in 189 consecutive patients who had been determined by surgical operation and pathology. Conventional ultrasound features and SWE elasticity imaging characteristics and properties of the final postoperative pathology were recorded. A comparative study between true and false results of quantitative SWE elasticity imaging, and the corresponding conventional ultrasound nodule characteristics were compared.Result:Postoperative pathology showed 189 nodules, 74(39.2%) were benign and 115(60.8%) were malignant. The sensitivity, specificity of conventional ultrasound in the diagnosis of thyroid nodules were 56.5% and 81.1% respectively, and those of SWE were 60.9% and 85.1%. The false positive rate of shear wave elastography in diagnosing benign nodules and the false negative rate of malignant nodules were 14.9% and 39.1%, respectively. The false negative rate was higher than the false positive rate. A vertical growth (P< 0.01) and smaller diameter of the masses were significantly associated with false SWE findings (P< 0.01).Conclusion:The SWE imaging has important significance for differentiating benign and malignant thyroid nodules, but false results are inevitable, which requires clinicians conjunction with other test results to prevent errors judgment when reviewing the SWE imaging.

[Correlation analysis between glycolipids metabolism and clinicopathologic features in patients with gastric cancer].

OBJECTIVE: To analyze the correlation between glycolipids metabolism and clinicopathologic features in patients with gastric cancer. METHODS: Glycolipids metabolism and clinicopathologic features of 443 gastric cancer patients were collected, and their correlation was analyzed. RESULTS: Compared to gastric cancer patients with normal levels of glycolipids metabolism, there were less male patients who were with low level of total cholesterol (TCH)(χ(2)=7.676, P<0.05), and the number of male patients with low level of high-density lipoprotein (HDL) (χ(2)=7.520) and apoA1 (χ(2)=6.253) was higher (both P<0.05). Serum TCH level showed a negative correlation with age of patients (r=-0.116), tumor size (r=-0.117) and TNM stage (r=-0.111) (P<0.05); serum HDL level was negatively correlated with tumor diameter (r=-0.094), the number of metastatic lymph nodes (r=-0.106), primary tumor invasion depth (r=-0.112), metastatic lymph nodes stage (r=-0.102) and TNM stage (r=-0.107) (P<0.05); serum LDL was negatively correlated with age of patients (r=-0.116) (P<0.05); serum LPa was positively correlated with tumor size (r=0.170), the number of metastatic lymph nodes (r=0.151), primary tumor invasion depth (r=0.160), metastatic lymph nodes stage (r=0.153) and TNM stage (r=0.115) (P<0.05); apoA1 was negatively correlated with distant metastasis (r=-0.168) and TNM stage (r=-0.120) (P<0.05); and apoB was negatively correlated with distant metastases (r=-0.132, P<0.05). Levels of blood glucose and TG had no significant association with clinicopathological features of gastric cancer patients (P>0.05). CONCLUSIONS: Low lipid metabolism but high level of LPa may be the metabolic characteristics of gastric cancer progression. Monitoring the changes of serum lipids levels could be valuable for the prognosis of patients with gastric cancer.

Use of Percutaneous Sonographically Guided Microwave Ablation Therapy to Treat Inoperable Malignant Liver Tumours.

AIMS: Microwave ablation (MWA) is a technique which is used to destroy tumours and soft tissues by using microwave energy to create coagulation and localized tissue necrosis. It is used to treat the tumours which are considered to be inoperable and used to treat those patients who are ineligible for surgery due to some factors. The main objective of this study was to evaluate the use of MWA in the treatment of liver cancer. METHODS: The data were collected from Department of Ultrasound, Harbin Medical University Cancer Hospital. From July 2010 to August 2011, a total of 123 patients with liver tumours was referred to Harbin Medical University Cancer Hospital. One hundred patients were selected for this study and treated with MWA. The study group contained 64 (64%) males and 36 (36%) females with an average age (± SD) of 52 (± 5.1) years. RESULTS: One month after therapy, complete ablation was obtained in nodules. The complete ablation rate in tumors ≤ 3 cm and those > 3 cm was 98% and 94%, respectively. Microwave ablation success was higher with nodules ≤ 3 cm (57/58; 98.3%) in comparison to nodules > 3 cm. CONCLUSION: Sonographically guided percutaneous microwave ablation proved to be safe, fast and effective for treatment of hepatocellular carcinoma.

Meta-analysis of the association between the HNF1B rs4430796 (A>G) polymorphism and risk of prostate cancer based on case-control studies.

Genome-wide studies have reported an association between the HNF1B rs4430796 (A>G) polymorphism and prostate cancer risk, but results have been inconsistent and recent meta-analyses have been inadequate. This study aimed to integrate previous results and explore the validity of this association. Electronic searches for all relevant publications through May 18, 2014, were conducted across several databases. Additional studies were identified manually, and only the most recent or complete were used in this meta-analysis. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association. Seven eligible case-control studies were identified, incorporating a total of 14,049 patients and 12,674 controls. Overall, we found that the rs4430796 (A>G) polymorphism had a decreased risk of prostate cancer (GG vs AA: OR = 0.661, 95%CI = 0.615-0.710, P = 0.304; AG vs AA: OR = 0.782, 95%CI = 0.739-0.828, P = 0.435; dominant model: OR = 0.743, 95%CI = 0.704-0.784, P = 0.912; recessive model: OR = 0.764, 95%CI = 0.718-0.813, P = 0.01). Furthermore, in the stratified analysis, there were significantly decreased risks among studies with population- and hospital-based controls. In the subgroup analysis by ethnicity, significantly decreased risks were also found among Caucasians, Americans, and Asians. Our results suggested that the HNF1B rs4430796 (A>G) polymorphism decreased the risk of prostate cancer. In the future, additional and larger studies on patients from across of the world might be required to validate our findings.

New roles of filopodia and podosomes in the differentiation and fusion process of osteoclasts.

The cytoskeleton mediates various cellular processes such as differentiation and fusion, including in the filopodia and podosomes. However, apart from cell migration and formation of the sealing zone, little is known regarding the changes and related regulatory mechanisms of the cytoskeleton and additional roles of the filopodia and podosomes during the differentiation and fusion of osteoclasts. The cytomorphology and cytoskeleton of osteoclasts in the differentiation process were evaluated using tartrate-resistant acid phosphatase staining and immunofluorescence staining. Moreover, the expression levels of Rho GTPases and enzymes related to osteoclast differentiation and bone resorption were detected by quantitative reverse transcription-polymerase chain reaction. We detected 3 types of filopodia in osteoclast precursors and only 1 type of filopodia in undifferentiated cells. Mature osteoclasts were completely devoid of filopodia. Interestingly, cell fusion was highly specific, and the fusion initially occurred to the filopodia. Confocal images revealed that F-actin and microtubules significantly differed among fused cells. These results suggest that filopodia and podosomes not only play important roles in cell migration and the formation of sealing zones but also in the pre-fusion selectivity of 2 cells and the movement direction of the cell nucleus and cytoplasm during the fusion process. In addition, cdc42v1, RhoU, and RhoF regulate the formation of 3 types of filopodia during various stages of differentiation, while Rac1, Rac2, and filament A may be associated with cell selectivity during the fusion process.

Development of three vitrification-based cryopreservation procedures for shoot tips of China's potato.

China is now the largest potato producing country worldwide. The establishment of efficient conservation techniques for potato germplasm is a prerequisite for breeding of elite cultivars. Potato viral diseases have been a great threat for sustainable potato production in China. Use of virus-free seed tubers is an effective and practical means to control viral diseases. In the present study, three vitrification-based cryopreservation techniques, i.e. droplet-vitrification, encapsulation-vitrification and vitrification were successfully developed for the first time for China's potato. Cultivar 'Zihuabai' was used to optimize key parameters involved in the three vitrification-based procedures. With the optimized parameters, shoot regrowth percentages of 71%, 76% and 43% were obtained for droplet-vitrification, encapsulation-vitrification and vitrification, respectively. The three protocols developed were further tested with eight China's major cultivars, with average shoot regrowth of 61%, 38% and 28% for droplet-vitrification, encapsulation-vitrification and vitrification, respectively. Successful development of the three cryopreservation procedures using a single cultivar will facilitate a number of comparative studies such as cryo-injury, regrowth pattern, genetic stability and efficiency of virus elimination. Testing these three cryogenic procedures for potato major cultivars representing a wide range of genetic background, will help the establishment of potato cryobanking in China and the production of virus-free plants.

Benchmark comparison of ab initio microRNA identification methods and software.

MicroRNAs (miRNAs) are short, non-coding RNA molecules that play an important role in the world of genes, especially in regulating the gene expression of target messenger RNAs through cleavage or translational repression of messenger RNA. Ab initio methods have become popular in computational miRNA detection. Most software tools are designed to distinguish miRNA precursors from pseudo-hairpins, but a few can mine miRNA from genome or expressed sequence tag sequences. We prepared novel testing datasets to measure and compare the performance of various software tools. Furthermore, we summarized the miRNA mining methods that study next-generation sequencing data for bioinformatics researchers who are analyzing these data. Because secondary structure is an important feature in the identification of miRNA, we analyzed the influence of various secondary structure prediction software tools on miRNA identification. MiPred was the most effective for classifying real-/pseudo-pre-miRNA sequences, and miRAbela performed relatively better for mining miRNA precursors from genome or expressed sequence tag sequences. RNA-fold performed better than m-fold for extracting secondary structure features of miRNA precursors.

Recovery from Mercury Contamination in the Second Songhua River, China.

Mercury pollution in the Second Songhua River (SSR) was serious in the last century due to effluent from a chemical corporation. Effects of riverine self-purification on mercury removal were studied by comparing monitoring data of mercury concentrations varieties in water, sediment, and fish in the past, about 30 years. The present work suggested that a river of such a size like the SSR possessed the potential ability to recover from mercury pollution under the condition that mercury sources were cut off, though it needs a very long time, which might be several decades or even a century of years. During the 30 years with no effluent containing mercury input, total mercury (T-Hg) of water and sediment in some typical segments, mostly near the past effluent outlet, had decreased radically but still higher than the background values, though the decrease amplitudes were over 90% compared with that in 1975. T-Hg had decreased by more than 90% in most fishes, but some were still not suitable for consumption. Methylmercury concentrations (MeHg) of water, sediment, and fish were higher or close to the background levels in 2004. In the coming decades, the purification processes in the SSR would be steady and slow for a long period.

Elimination of two viruses which interact synergistically from sweetpotato by shoot tip culture and cryotherapy.

Sweet potato chlorotic stunt virus (SPCSV; Closteroviridae) and Sweet potato feathery mottle virus (SPFMV; Potyviridae) interact synergistically and cause severe diseases in co-infected sweetpotato plants (Ipomoea batatas). Sweetpotato is propagated vegetatively and virus-free planting materials are pivotal for sustainable production. Using cryotherapy, SPCSV and SPCSV were eliminated from all treated single-virus-infected and co-infected shoot tips irrespective of size (0.5-1.5mm including 2-4 leaf primordia). While shoot tip culture also eliminated SPCSV, elimination of SPFMV failed in 90-93% of the largest shoot tips (1.5mm) using this technique. Virus distribution to different leaf primordia and tissues within leaf primordia in the shoot apex and petioles was not altered by co-infection of the viruses in the fully virus-susceptible sweetpotato genotype used. SPFMV was immunolocalized to all types of tissues and up to the fourth-youngest leaf primordium. In contrast, SPCSV was detected only in the phloem and up to the fifth leaf primordium. Because only cells in the apical dome of the meristem and the two first leaf primordia survived cryotherapy, all data taken together could explain the results of virus elimination. The simple and efficient cryotherapy protocol developed for virus elimination can also be used for preparation of sweetpotato materials for long-term preservation.

Bioaccumulation of total and methyl mercury by arthropods.

Three arthropods, Locusta migratoria manilensis, Acrida chinensis, and Paraten-odera sinensis were selected to study the bioaccumulation of total and methyl mercury. Concentrations of total mercury in the tissues of Locusta migratoria manilensis and Acrida chinensis were 0.013-0.154 and 0.009-0.138 mg/kg, respectively, while those of methylmercury were 0.001-0.012 and 0.001-0.006 mg/kg, respectively. Concentrations of total mercury in Locusta migratoria manilensis and Acrida chinensis, which are the primary consumers, are lower than those in their food, while mercury is accumulated more by the secondary consumer, Paraten-odera sinensis. For total mercury, the concentrations in Locusta migratoria manilensis are inversely proportional to body length and those in Acrida chinensis increase first and then decrease with increased body length. For methyl mercury, concentration is proportional to body length for both of these arthropods. Total mercury concentrations vary in different parts of the arthropod body, and increase in the order of: abdomen > thorax > head.

Lowering of pI by acylation improves the renal uptake of 99mTc-labeled anti-Tac dsFv: effect of different acylating reagents.

Anti-Tac disulfide-stabilized variable region fragment (dsFv) was labeled with 99mTc by a preformed chelate approach using 99mTc-MAG3-trifluorophenyl (TFP) ester. Simultaneously it was acylated with TFP-lactate or succinic anhydride to decrease the isoelectric point of dsFv (pI 10). Acylation of dsFv (0.04 mM) with the lactate at a 73 times molar excess reduced the pI to 5.0-6.7, whereas acylation with succinic anhydride at a 30 times molar excess reduced the pI to 4.9-8.7. Comparative biodistribution studies performed in mice (n = 5) showed the reduced renal accumulation of the 99mTc proportional to the pI reduction. The effect of the pI on the reduced renal uptake was especially pronounced at 15 min postinjection. The reduced renal uptake was also reflected in the reduced whole-body retention, indicating that lowering the pI inhibited the tubular reabsorption of the labeled dsFv.

Fingertip injuries.

The family physician often provides the first and only medical intervention for fingertip injuries. Proper diagnosis and management of fingertip injuries are vital to maintaining proper function of the hand and preventing permanent disability. A subungual hematoma is a painful condition that involves bleeding beneath the nail, usually after trauma. Treatment requires subungual decompression, which is achieved by creating small holes in the nail. A nail bed laceration is treated by removing the nail and suturing the injured nail bed. Closed fractures of the distal phalanx may require reduction but usually are minimally displaced and stable, and can be splinted. Open or intra-articular fractures of the distal phalanx may warrant referral. Patients with mallet finger cannot extend the distal interphalangeal joint because of a disruption of the extensor mechanism. Radiographs help to differentiate between tendinous and bony mallet types. Most mallet finger injuries heal with six to eight weeks of splinting, but some require referral. Flexor digitorum profundus avulsion always requires referral. Dislocations of the distal interphalangeal joint are rare and usually occur dorsally.

Inhibition of TNF-alpha produced by Kupffer cells protects against the nonspecific liver toxicity of immunotoxin anti-Tac(Fv)-PE38, LMB-2.

LMB-2 (anti-Tac(Fv)-PE38) is a recombinant immunotoxin composed of the Fv fragment of the anti-Tac Ab fused to a 38-kDa form of Pseudomonas: exotoxin A. Recent clinical trials showed that LMB-2 is a promising agent for the treatment of patients with Tac-positive leukemia or lymphoma. One major side effect that needs to be overcome is nonspecific liver toxicity. In the current study, we have analyzed the mechanism of this toxicity using a mouse model. Mice that were injected with a lethal dose of LMB-2 showed severe hepatic necrosis. Immunohistochemistry revealed that LMB-2 accumulated in Kupffer cells in the liver, suggesting that the damage to the hepatocytes was indirect. When we examined the effects of LMB-2 on peritoneal macrophages, cells in the same lineage as Kupffer cells, we found that LMB-2 induced the production of TNF-alpha by these cells. Following LMB-2 administration to mice, the levels of TNF-alpha in the liver increased to very high levels, whereas the rise in serum levels was modest. In addition, the LMB-2-induced liver toxicity was blocked by a specific TNF binding protein (TNFsRp55). Liver toxicity was also blocked by indomethacin, which also blocked the rise of TNF-alpha in the liver. Both TNFsRp55 and indomethacin treatment protected mice against a lethal dose of LMB-2. These data indicate that TNF-alpha produced in the liver by Kupffer cells has an important causal role in the nonspecific liver toxicity of LMB-2. These findings have important clinical implications for the use of immunotoxins in the therapy of patients with cancer.

Anti-tumor activity of K1-LysPE38QQR, an immunotoxin targeting mesothelin, a cell-surface antigen overexpressed in ovarian cancer and malignant mesothelioma.

Mesothelin, a differentiation antigen, is a 40-kD glycosylphosphatidylinositol-linked cell-surface glycoprotein, that is present on the surface of normal mesothelium and is overexpressed in many patients with epithelial ovarian cancer and malignant mesotheliomas. Monoclonal antibody K1 is a murine immunoglobulin G1 that recognizes mesothelin. LysPE38QQR is a truncated form of Pseudomonas exotoxin that lacks the cell-binding domain, but retains the translocation and adenosine diphosphate-ribosylation domains. It has a single lysine residue near the amino terminus that is available for conjugation to antibodies. To prevent chemical conjugation of the antibody to lysine residues at the C-terminus of Pseudomonas exotoxin, the two lysine residues at positions 590 and 606 were mutated to glutamine, and the lysine residue at position 613 was mutated to arginine. Monoclonal antibody K1 was chemically conjugated with LysPE38QQR, by modifying the antibody with sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate and coupling it with SPDP N-succinimidyl 3-(2-pyridyldithio)propionate-modified LysPE38QQR. The resulting immunotoxin K1-LysPE38QQR was highly toxic to A431-K5 cells (a human epidermoid carcinoma cell line transfected with a mesothelin expression plasmid) with a half-maximal inhibitory concentration of 3-6 ng/mL. The immunotoxin had negligible activity against A431 cells, which do not express mesothelin (median inhibitory concentration > 100 ng/mL). This immunotoxin also caused complete regression of tumors in nude mice that received xenografts of mesothelin-positive human carcinomas. These results show that immunotoxins directed against mesothelin are a therapeutic option that merits further investigation for the treatment of ovarian cancer and malignant mesotheliomas.