Long non-coding RNA LINP1 promotes the malignant progression of prostate cancer by regulating p53.

We detected some serious inaccuracies and mistakes. Therefore, the article "Long non-coding RNA LINP1 promotes the malignant progression of prostate cancer by regulating p53, by H.-F. Wu, L.-G. Ren, J.-Q. Xiao, Y. Zhang, X.-W. Mao, L.-F. Zhou, published in Eur Rev Med Pharmacol Sci 2018; 22 (14): 4467-4476-DOI: 10.26355/eurrev_201807_15498-PMID: 30058678" has been withdrawn. The Publisher apologizes for any inconvenience this may cause. https://www.europeanreview.org/article/15498.

Long non-coding RNA LINP1 promotes the malignant progression of prostate cancer by regulating p53.

OBJECTIVE: We aim to investigate the expression of long non-coding RNA-LINP1 (lncRNA LINP1) in prostate cancer (PCa) and its potential mechanism. PATIENTS AND METHODS: The expression of lncRNA LINP1 in 74 pairs of PCa and normal tissues were detected by quantitative Real-time polymerase chain reaction (qRT-PCR); the relationship between its expression and the pathological features and prognosis of PCa was also analyzed. The expression of lncRNA LINP1 in the PCa cell line was verified by qRT-PCR. Knockdown of LINP1 was constructed by transfection of small interfering RNA (siRNA) in two PCa cell lines (Lncap and PC-3). The biological function of LINP1 was evaluated by cell counting kit-8 (CCK-8) assay, colony formation assay, migration and invasion assay, respectively. Finally, the potential mechanism of LINP1 was explored by Western blot and qRT-PCR. RESULTS: qRT-PCR results showed a higher expression of LINP1 in PCa than that of normal tissues. Compared with PCa patients with a lower expression of LINP1, those with higher expression had a higher tumor stage, lymphatic metastasis and distant metastasis rate, and lower overall survival rate. Proliferation, invasion and metastasis in cells transfected with si-LINP1 were remarkably decreased than those transfected with negative control (si-NC). Moreover, the expressions of the key proteins in the p53 signaling pathway, including p53, PTEN, Akt and CDK2 were remarkably decreased in cells after knockdown of LINP1. In addition, a negative correlation between LINP1 and p53 was confirmed by rescue experiments. CONCLUSIONS: Up-regulated LINP1 in PCa was correlated with a higher PCa stage, lymphatic metastasis, distant metastasis, and worse prognosis. Furthermore, LINP1 could promote the proliferative, migratory and invasive abilities of PCa by regulating the p53-signaling pathway.

[Gastrointestinal leiomyoma with interstitial cells of Cajal: mimicker of gastrointestinal stromal tumor].

Objective: To study clinical and pathologic characteristics of leiomyomas of the gastrointestinal tract, and to investigate the distribution characteristics of interstitial cells of Cajal ( ICCs ) in gastrointestinal leiomyomas. Methods: One hundred and forty-seven cases of leiomyomas of gastrointestinal tract were collected at the Second Affiliated Hospital of Zhengzhou University from June 2012 to June 2017. Clinical and pathologic findings were analyzed, combined with immunohistochemistry, Alcian blue-osafranin staining and molecular study. Results: The age of patients ranged from 13-82 years with mean age of 52 years. Male to female ratio was about 1∶2. Histologically, all tumors were composed of ovoid to spindle cells arranged in short intersecting fascicles. All tumors were diffusely and strongly positive for smooth muscle antibodies, desmin and h-caldesmon by immunohistochemical staining. A prominent interspersed subpopulation of elongated/dendritic-like cells with CD117 and DOG1 positivity (accounting for 1% to 30% of all tumor cells) and negative for Alcian blue-osafranin staining was identified in all esophageal leiomyomas, 16 of 20 (80%) gastric leiomyomas and 3 of 12 small bowel leiomyomas, but none in colonic/rectal leiomyomas. Mutational analysis in 16 cases showed absence of mutation in exons 9, 11, 13 or 17 of C-KIT and exons 12 or 18 of PDGFRA. Conclusions: ICCs are identified in esophageal and gastric leiomyomas, as well as in small percentage of intestinal leiomyomas. Such findings may bring significant diagnostic pitfalls for misdiagnosis as gastrointestinal stromal tumor. Careful attention to the distribution of CD117 and DOG1 positive cells and molecular mutation analysis of C-KIT and PDGFRA may be necessary to establish the correct diagnosis.

[Clinicopathologic features of gastric plexiform fibromyxoma].

Objective: To analyse the clinicopathologic features of gastric plexiform fibromyxoma (PF) including diagnosis, differential diagnosis, immunohistochemistry and molecular pathology. Methods: Eight cases of PF were collected from June 2006 to June 2017 at the Second Affiliated Hospital of Zhengzhou University and the First Affiliated Hospital of Zhengzhou University. The clinicopathologic findings of eight cases of PF were retrospectively analyzed, and immunohistochemistry (EnVision method) and molecular detection of glioma-associated oncogene homologue 1 (GLI1) gene translocation were performed. All cases were histologically reviewed with immunohistochemical staining for smooth muscle actin (SMA), CD10, CD117, DOG1, CD34, ER, PR, ALK and S-100. Fluorescence in situ hybridization (FISH) was used to detect the GLI1 gene translocation, and mutation of CKIT exons 9, 11, 13 and 17; and PDGFRA exons 12, 14 and 18 were identified by Sanger sequencing in four cases. Relevant literature was reviewed. Results: The study included four men and four women, age ranged from 26 to 72 years (mean 51 years). Histologically, the tumors were rich in small thin-walled blood vessels and myxoid matrix, and exhibited multiple nodular growth pattern in the gastric wall. The tumor cells were bland, spindled or oval. Immunohistochemically, all cases strongly expressed vimentin and SMA, and some expressed CD10 (4/8), desmin (3/8), H-caldesmon (5/8) and PR (5/8), but were negative for CD34, S-100, ER, ALK, CD117 and DOG1. The GLI1 gene translocation detection was performed in eight cases by FISH with three positive cases and five negative cases. Mutation analyses for exons 9, 11, 13, and 17 of CKIT genes and exons 12, 14, and 18 of the PDGFRA genes were performed and the tumors all of four tested cases were wild-type. Seven patients were followed up (ranged from 24 to 95 months, mean 50 months) after diagnosis and none of the patients had recurrence or metastasis. Conclusions: PF is a rare novel mesenchymal tumor of the stomach. Its distinct clinicopathologic features and immunohistochemical positivity for SMA, CD10 and PR can help differentiating this entity from other gastrointestinal mesenchymal tumors. FISH detection of GLI1 gene translocation offers an additional molecular diagnostic marker for the diagnosis.

Characterization of tissue chromogranin A (CgA) immunostaining and clinicohistopathological changes for the 125 Chinese patients with primary small cell carcinoma of the esophagus.

The rarity of primary small cell carcinoma of the esophagus (PSCE) has limited the clinical feature and survival analysis with large sample size. Tissue chromogranin A (CgA) protein expression has been reported to be a useful biomarker for diagnosing PSCE. Interestingly, recent studies have indicated tissue CgA as a significant prognostic marker in multiple human cancers, but without PSCE. The present study, thus, was undertaken to characterize the clinicopathological changes and to evaluate the associations of tissue CgA expression with clinical response on Chinese PSCE patients. All the 125 PSCE patients were enrolled from our 500,000 esophageal and gastric cardia carcinoma databases (1973-2015), constructed by the cooperative team from more than 700 hospitals in China and established by Henan Key Laboratory for Esophageal Cancer Research in Henan, China. Immunostaining for CgA showed that CgA was mainly located in cytoplasm of tumor cells with a positive detection rate of 44.6%. The CgA positive expression rate in PSCE at lower segment of the esophagus (72.2%) was higher than that at middle segment (41.5%) (P = 0.001). However, CgA protein expression did not correlated with lymph node metastasis (P = 0.767), TNM staging (P = 0.740), tumor invasion (P = 0.253), gender (P = 0.262), and age (P = 0.250). Multivariate survival analysis showed that the patients with higher CgA protein expression had a superior long survival than those without CgA expression (P = 0.037). The clinicopathological analysis showed that PSCE occurred predominantly in male (M:F = 1.9:1) at the middle segment (68%) of the esophagus. Histologically, 89.6% were pure PSCE and 10.4% were mixed type with either squamous cell carcinoma (8%) or adenocarcinoma (2.4%). It was noteworthy that, with the in-depth invasion from T1 to T2 and T3, the positive lymph node metastasis rate increased dramatically from 38%, 56% to 74%, respectively. The survival rates of 1-, 2-, 3-, and 5-year were 64%, 35%, 18%, and 7%, respectively. The Kaplan-Meier survival analysis showed that the young patients (≤60 years) had longer survival than the elderly (P = 0.011). Interestingly, multivariate survival analysis revealed that the patients with mixed PSCE had a significantly better survival than those with pure PSCE (P = 0.015). Furthermore, the median survival time for the patients with and without lymph node metastasis was 1.16 and 2.03 years, respectively. But, the difference was not significant (P = 0.143). Univariate analysis did not show any survival influence by gender, tumor location, tumor invasion depth, and TNM staging. It was noteworthy that, of the 13 early PSCE patients (T1N0M0), only one patient had more than 5 year survival, the others died with less than one or two year (65%). The present study indicates that the PSCE is of badly worsen prognosis, even in the pathological early stage. Tissue CgA protein expression is a promising maker not only for diagnosis and also for prognosis. Further assessment is needed to establish specific PSCE pathological staging system and to clarify the mechanisms of CgA protein in PSCE progression and prognosis.

Resistin-like molecule-ß (RELM-ß) targets airways fibroblasts to effect remodelling in asthma: from mouse to man.

BACKGROUND: RELM-ß has been implicated in airways inflammation and remodelling in murine models. Its possible functions in human airways are largely unknown. The aim was to address the hypothesis that RELM-ß plays a role in extracellular matrix deposition in asthmatic airways. METHODS: The effects of RELM-ß gene deficiency were studied in a model of allergen exposure in mice sensitised and challenged with Aspergillus fumigatus (Af). RELM-ß expression was investigated in bronchial biopsies from asthmatic patients. Direct regulatory effects of RELM-ß on human lung fibroblasts were examined using primary cultures and the MRC5 cell line in vitro. RESULTS: Sensitisation and challenge of wild-type mice with Af-induced release of RELM-ß with a time course coincident with that of procollagen in the airways. Af-induced expression of mRNA encoding some, but not all ECM in the lung parenchyma was attenuated in RELM-ß-/- mice. RELM-ß expression was significantly increased in the bronchial submucosa of human asthmatics compared with controls, and its expression correlated positively with that of fibronectin and α-smooth muscle actin. In addition to epithelial cells, macrophages, fibroblasts and vascular endothelial cells formed the majority of cells expressing RELM-ß in the submucosa. Exposure to RELM-ß increased TGF-ß1, TGF-ß2, collagen I, fibronectin, smooth muscle α-actin, laminin α1, and hyaluronan and proteoglycan link protein 1 (Hapl1) production as well as proliferation by human lung fibroblasts in vitro. These changes were associated with activation of ERK1/2 in MRC5 cells. CONCLUSION: The data are consistent with the hypothesis that elevated RELM-ß expression in asthmatic airways contributes to airways remodelling at least partly by increasing fibroblast proliferation and differentiation with resulting deposition of extracellular matrix proteins.

Endoscopic management of impacted esophageal foreign bodies.

There are many reports on the endoscopic management of ingested foreign bodies in the upper gastrointestinal tract, however, little is known about the management of a specific subset of esophageal foreign bodies - impacted esophageal foreign bodies (IEFBs), especially perforating esophageal foreign bodies (PEFBs). The aim of this retrospective study on 78 cases was to report experience and outcome in the endoscopic management of the IEFBs in Chinese patients. From January 2006 to July 2011, a total of 750 patients with suspected upper gastrointestinal foreign bodies were admitted to the endoscopy center. Among these 750 patients, 78 cases that met the defined criteria of IEFBs were retrospectively enrolled in the present study, including 12 cases (12/78, 15.4%) with PEFBs. The major types of IEFBs were poultry bones (35.9%) and fish bones (17.9%). Most of the IEFBs (80.8%) were located in the upper esophagus, as were two thirds (66.7%) of the PEFBs. Foreign-body retrieval forceps were the most frequently used accessory devices. Extraction of IEFBs failed in eight patients (10.3%) during the endoscopic procedure. The difficult points in endoscopic management were PEFBs, IEFBs with sharp points, and those with impaction for more than 24 hours. IEFBs should be treated as early as possible, and their endoscopic management is safe and effective. Endoscopic management is the first choice for PEFBs when the duration of impaction is less than 24 hours and there are no abscesses outside of the esophageal tract as determined by a computed tomography scan.

ELAC2 polymorphisms and prostate cancer risk: a meta-analysis based on 18 case-control studies.

Polymorphisms in the elaC homolog-2 (ELAC2)/HPC2 gene have been hypothesized to alter the risk of prostate cancer. However, the results of the related published studies remained conflicting. We performed a meta-analysis of 18 studies evaluating the association between ELAC2 Ser217Leu and Ala541Thr polymorphisms and prostate cancer risk. Overall, ELAC2 Leu217 allele was associated with increased prostate cancer risk as compared with the Ser217 allele (odds ratio (OR)=1.13, 95% confidence interval (CI): 1.03-1.24, P=0.019 for heterogeneity), as well as in the heterozygote comparison (OR=1.21, 95% CI: 1.07-1.36, P=0.034 for heterogeneity) and the dominant genetic model (OR=1.20, 95% CI: 1.07-1.35, P=0.025 for heterogeneity). Furthermore, the ELAC2 Thr541 allele was associated with increased prostate cancer risk as compared with the Ala541 allele (OR=1.22, 95% CI: 1.00-0.48, P=0.131 for heterogeneity). In the stratified analyses for Ser217Leu polymorphism, there was significantly increased prostate cancer risk in Asian and Caucasian populations, and studies using sporadic and familial prostate cancer cases. Similar result was found in the Asian population in the stratified analyses for Ala541Thr polymorphism. This meta-analysis showed evidence that ELAC2 Ser217Leu and Ala541Thr polymorphisms were associated with prostate cancer risk, and might be low-penetrance susceptibility markers of prostate cancer.

The association between MIF-173 G>C polymorphism and prostate cancer in southern Chinese.

BACKGROUND AND OBJECTIVES: Accumulating epidemiological and molecular evidence suggests that inflammation is an important component in the etiology of PCa. Macrophage migration inhibitory factor (MIF) plays an important role in the pro- and anti-inflammatory response to infection. This study is aimed at investigating the potential association between MIF-173 G>C polymorphism, Gleason score, clinical stage, and prostate-specific antigen (PSA) value with respect to PCa incidence among the Han nationality in Southern China. METHODS: Genotyping was performed by using tetraprimer polymerase chain reaction (PCR) on 259 PCa patients and 301 cancer-free controls. RESULTS: We found that the MIF-173*C variant allele was significantly associated with an increased risk of PCa [adjusted odd ratio (OR) = 2.99, 95% confident interval (CI): 1.94-4.60] and higher Gleason scores from the PCa subjects (adjusted OR = 10.72, 95% CI: 5.35-21.49). In addition, we noted that the MIF -173*C variant allele was related to higher clinical stages and PSA values in PCa patients (adjusted OR = 15.68, 95% CI: 7.40-33.23; adjusted OR = 4.37, 95% CI: 2.41-7.92, respectively). CONCLUSION: Our data suggest that MIF-173 polymorphisms may be associated with a higher incidence of prostate cancer compared to controls, and appears to be associated with higher Gleason scores, higher clinical stages, and PSA values in those with prostate cancer.

Extraperitoneal laparoscopic radical prostatectomy.

A total of 28 patients with clinically localized prostate cancer (PCa) underwent extraperitoneal laparoscopic radical prostatectomy (EP-LRP). The mean operative duration was 309 (287-600) minutes. Estimated blood loss ranged from 380 to 1000 (mean 480) ml. At 3 to 5 days postoperatively, the catheter was removed. No open conversion was required and no patient presented postoperative complications. PSA level was less than 0.1 ng/ml at 3 months after surgery in all patients. At a mean follow-up of 10 (6-16) months, there were no biochemical failures. The extraperitoneal technique potentially decreased the risk of intra-abdominal complications and better approximated than open retropubic radical prostatectomy. In conclusion, EP-LRP is an effective, safe and precise technique.

Probing reactive sites for ion-molecule reactions of anthraquinones with dimethyl ether using an external source ion trap tandem mass spectrometer and computational chemistry.

Gas-phase ion-molecule reactions of anthraquinone derivatives with dimethyl ether (DME) were investigated using an external source ion trap mass spectrometer. Semi-empirical calculations were executed to determine possible reactive sites for the product ions. Collision activated dissociation (CAD) was successfully performed for very low abundance of ion-molecule products. Even for product ions with a relative intensity below 1%, CAD experiments can be successfully performed. Significantly more structural information could be elucidated based on this special feature. Importantly, the CAD spectra of very minor ions could be measured by this ion trap instrument, which significantly enhances the future role of the ion trap as a powerful analytical instrument. CAD of all product ions on anthraquinone compounds typically eliminates neutral molecules such as CO or H(2)O. A hydration phenomenon in the CAD processes resulting from the precursor ions incorporating one molecule of H(2)O and then eliminating one molecule of CO was observed in this study.

Pressure assessment in intercavernous embedding of bulboperineal urethra for treatment of urinary incontinence after prostatic operation.

AIM: To put forward criteria for the pressure assessment in the operation of intercavernous embedding of bulboperineal urethra for the treatment of urinary incontinence after prostatic operation. METHODS: A F14 urethral catheter is inserted during the operation and upon suturing the corpora cavemosa centrally, the catheter is slowly pushed in and pulled out in order that the operator feels a certain degree of close-fit resistance. The degree of tightness of the stitches, which regulate the compression pressure, is adjusted in accordance with this close-fit sensation. To further ascertain the adequacy of the force of compression, the bladder is filled with 300 ml physiological saline and observe the appropriateness (size and continuity) of the outflow stream when the lower abdomen is depressed with a pressure of 80-90 cm H2O. The operation was given to six patients suffered from urinary incontinence for 20 or more months after prostatic operation. RESULTS: Five cases achieved complete recovery, while the therapeutic effect of the 6th one was not satisfactory. A second stage operation was carried out 3 months later with the addition of one more stitch both proximally and distally to reinforce the compression force. The condition was improved dramatically. The follow-up period averaged 3.5 years. CONCLUSION: The adequacy of the compression pressure exerted by the juxtaposed corpora cavernosa is the key point determining the outcome of the operation. The measures for assessing the compression pressure suggested by the authors are helpful in obtaining the good results of the present paper (6/6 success) as compared with 25/34 success in the previous report.

Evoked facial nerve EMG and brainstem auditory evoked potential monitoring in cerebellopontine angle tumor resection.

BACKGROUND: The preservation of normal nerve function or identification of nerve route is critical in some surgeries of cerebellopontine angle tumors. Over the last 5 years, intraoperative facial nerve electromyogram (EMG) and brainstem auditory evoked potential (BAEP) were applied for evaluation of facial nerve integrity and brainstem function in patients while undergoing resection of cerebellopontine angle (CPA) tumor. This report represents the retrospective analysis of our results. METHODS: The inhalational anesthesia with 1-1.5% isoflurane in pure O2 was used. Muscle relaxation was maintained with continuous infusion of atracurium. The degree of muscle relaxation was aimed at a T4/T1 ratio of train-of-four response more than 20% of the adductus pollicis upon ulnar nerve stimulation at the wrist. In 236 patients suffering from CPA tumor without facial palsy, the EMG of the mentalis muscle ipisilateral to the tumor was obtained through stimulation of the facial nerve. The stimulation was applied with a nerve finder, which delivered an electrical stimulation of a single 2 mamp direct current. The EMG finding was compared with the clinical result. In 198 patients, BAEP was used to monitor the brainstem function during tumor resection. In case of intact hearing the BAEP was taken ipsilateral to the operation side and in case with total hearing loss contralateral BAEP to operation side was used. For BAEP stimulation, 90 db click sound stimulation with frequency of 11.26 Hz was applied to both ears. BAEP signals were obtained and recorded at the mastoid region of either side in reference to the vertex. The EMG and BAEP signals were recorded and saved to an evoked potential monitor. RESULTS: In facial nerve EMG monitoring, there were two false positive and no false negative tests. Except for the two false positive tests, the postoperative clinical results in the other cases were compatible with the intraoperative facial nerve EMG findings. In BAEP monitoring, there were twenty-eight positive tests. CONCLUSIONS: The low incidence of false negative test suggests that facial nerve EMG is valuable in detection of facial nerve function in CPA tumor resection. Intraoperative BAEP abnormality is possibly useful in identifying postoperative brainstem dysfunction.

Neutralization of heparin activity by neutrophil lactoferrin.

Lactoferrin is a prominent component of neutrophil secondary granules, and its blood concentration is increased in certain inflammatory diseases. In contrast to the well-described biochemical characterization of lactoferrin as an iron-binding protein, its physiologic role in the regulation of inflammation and other host defense mechanisms is unclear. In this report, we provide evidence that lactoferrin has a potent heparin-neutralizing activity during thrombin inhibition by the serine proteinase inhibitors (serpins) antithrombin and heparin co-factor II. Activated neutrophil supernatant, which contains lactoferrin and other heparin-binding proteins, could neutralize the heparin-dependent antithrombin-thrombin inhibition reaction. The addition of lactoferrin to plasma corrected the heparin-induced prolongation of blood plasma coagulation as measured by the activated partial thromboplastin time (aPTT). Treatment of whole blood with specific inflammatory mediators, fMLP, lipopolysaccharide (LPS), and tumor necrosis factor-alpha (TNF-alpha) increased the concentration of both plasma lactoferrin and platelet factor 4 while inhibiting the blood anticoagulant activity of heparin as measured by the aPTT. These results suggest that the prothrombotic sequelae of some inflammatory processes may be partly due to various agonists that release neutrophil lactoferrin, which can then neutralize glycosaminoglycan-dependent serpin-thrombin inhibition reactions.

Hydrogen-bonding interactions in gas-phase polyether/ammonium ion complexes.

Hydrogen bonds are among the most important interactions involved in selective complexation in host-guest chemistry. In this study a variety of hydrogen-bonded crown ether/ammonium ion complexes are generated in the gas phase by association reactions between an amine substrate and a polyether, one of which is initially protonated, and stabilized by many collisions in the chemical ionlzation source of a triple quadrupole mass spectrometer or in a quadrupole ion trap. The nature of the hydrogen-bonding interactions of the ion complexes are evaluated by comparison of their collision-activated dissociation spectra. After collisional activation, those complexes that are weakly bound dissociate to form intact protonated polyether molecules and/or ammonium ions by simple cleavages of the hydrogen-bond association interactions. In contrast, those complexes strongly bound by multiple hydrogen bonds dissociate not only to the protonated polyether and/or ammonium ions but also by extensive covalent bond cleavage of the protonated ether skeleton.This latter type of dissociation behavior suggests that the polyether/ammonium ion complexes may be sufficiently strongly bound that surpassing the high barrier to decomposition results in formation of internally excited polyether molecules that may then undergo subsequent fragmentation by skeletal cleavages. Moreover, complexes involving multiple hydrogen bonds may have slower dissociation kinetics, allowing competition from fast dissociation processes that have substantial energy barriers.

The deduced amino acid sequences of human platelet and frontal cortex monoamine oxidase B are identical.

Monoamine oxidases (MAOs) A and B play important roles in the metabolism of neuroactive, vasoactive amines. Human platelets contain only MAO B, often used as an indicator of brain MAO B. The validity of this model remained to be evaluated. This report describes the molecular cloning of human MAO B from frontal cortex and platelets. Two overlapping PCR-amplified clones of human platelet MAO B and four PCR-amplified clones of human frontal cortex MAO B covering the entire coding region were sequenced using five internal oligomers and M13 reverse and forward primers. The nucleotide sequences of human MAO B cDNA from platelet and frontal cortex were identical to that of human liver MAO B except for three nucleotides that differed in frontal cortex: nucleotides 440 A-->G, 794 C-->T, and 825 C-->T. Whether or not these differences are artifactual, all three represent silent mutations, which would not alter the amino acid of the encoded polypeptides. Thus, the deduced amino acid sequences of MAO B from frontal cortex, platelet, and liver are identical. These findings indicate the validity of using platelet MAO B mRNA as a marker for brain MAO B and provide a new approach to study the role of brain MAO B in humans.

Site-directed mutagenesis of monoamine oxidase A and B: role of cysteines.

Nine cysteines are found in the deduced amino acid sequences of both human liver monoamine oxidase (MAO)-A and MAO-B. The role of these cysteine residues in MAO-A and -B catalytic activity was studied by site-directed mutagenesis, whereby each cysteine residue was converted to serine. The wild-type and mutant cDNAs were then transiently transfected into COS cells and assayed for MAO-A and -B catalytic activity using 5-[3H]hydroxytryptamine and [14C]phenylethylamine, respectively, as substrates. Catalytic activities were retained in seven MAO-A cysteine to serine mutants (mutations at residues 165, 210, 266, 306, 321, 323, and 398) and in six MAO-B cysteine to serine mutants (mutations at residues 5, 172, 192, 297, 312, and 389). Kinetic parameters (Km) of these mutants were also similar to those of the wild-type enzymes, indicating that these cysteines are not necessary for enzymatic activity. Substitution of MAO-A Cys-374 and -406 and MAO-B Cys-156, -365, and -397 with serine resulted in complete loss of MAO-A and -B catalytic activity. The loss of catalytic activity was not due to unsuccessful transfection of the mutants, as indicated by either Northern blot or Western blot analysis. The loss of catalytic activity in the MAO-A Ser-406 and MAO-B Ser-397 mutants may be due to the prevention of covalent binding of the enzyme to the cofactor FAD, which is necessary for catalytic activity. The loss of catalytic activity of MAO-A Ser-374 and MAO-B Ser-156 and -365 suggests that these cysteines are important for catalytic activity, but whether they are involved in forming the active site or are important for the appropriate conformation of MAO-A and -B remains to be studied.