Immunization with a peptide mimicking lipoteichoic acid induces memory B cells in BALB/c mice.

BACKGROUND: There is an urgent clinical need for developing novel immunoprophylaxis and immunotherapy strategies against Staphylococcus aureus (S. aureus). In our previous work, immunization with a tetra-branched multiple antigenic peptide, named MAP2-3 that mimics lipoteichoic acid, a cell wall component of S. aureus, successfully induced a humoral immune response and protected BALB/c mice against S. aureus systemic infection. In this study, we further investigated whether vaccination with MAP2-3 can elicit immunologic memory. METHODS: BALB/c mice were immunized with MAP2-3 five times. After one month of the last vaccination, mice were challenged with heat-killed S. aureus via intraperitoneal injection. After a 7-day inoculation, the percentage of plasma cells, memory B cells, effector memory T cells, and follicular helper T cells were detected by flow cytometry. The levels of IL-6, IL-21, IL-2, and IFN-γ were measured by real-time PCR and ELISA. Flow cytometry results were compared by using one-way ANOVA or Mann-Whitney test, real-time PCR results were compared by using one-way ANOVA, and ELISA results were compared by using one-way ANOVA or student's t-test. RESULTS: The percentage of plasma cells and memory B cells in the spleen and bone marrow from the MAP2-3 immunized mice was significantly higher than that from the control mice. The percentage of effector memory T cells in spleens and lymphoid nodes as well as follicular helper T cells in spleens from the MAP2-3 immunized mice were also higher. Moreover, the levels of IL-6 and IL-21, two critical cytokines for the development of memory B cells, were significantly higher in the isolated splenocytes from immunized mice after lipoteichoic acid stimulation. CONCLUSIONS: Immunization with MAP2-3 can efficiently induce memory B cells and memory T cells.

Passenger Gene Coamplifications Create Collateral Therapeutic Vulnerabilities in Cancer.

DNA amplifications in cancer do not only harbor oncogenes. We sought to determine whether passenger coamplifications could create collateral therapeutic vulnerabilities. Through an analysis of >3,000 cancer genomes followed by the interrogation of CRISPR-Cas9 loss-of-function screens across >700 cancer cell lines, we determined that passenger coamplifications are accompanied by distinct dependency profiles. In a proof-of-principle study, we demonstrate that the coamplification of the bona fide passenger gene DEAD-Box Helicase 1 (DDX1) creates an increased dependency on the mTOR pathway. Interaction proteomics identified tricarboxylic acid (TCA) cycle components as previously unrecognized DDX1 interaction partners. Live-cell metabolomics highlighted that this interaction could impair TCA activity, which in turn resulted in enhanced mTORC1 activity. Consequently, genetic and pharmacologic disruption of mTORC1 resulted in pronounced cell death in vitro and in vivo. Thus, structurally linked coamplification of a passenger gene and an oncogene can result in collateral vulnerabilities. SIGNIFICANCE: We demonstrate that coamplification of passenger genes, which were largely neglected in cancer biology in the past, can create distinct cancer dependencies. Because passenger coamplifications are frequent in cancer, this principle has the potential to expand target discovery in oncology. This article is featured in Selected Articles from This Issue, p. 384.

Elimusertib has Antitumor Activity in Preclinical Patient-Derived Pediatric Solid Tumor Models.

The small-molecule inhibitor of ataxia telangiectasia and Rad3-related protein (ATR), elimusertib, is currently being tested clinically in various cancer entities in adults and children. Its preclinical antitumor activity in pediatric malignancies, however, is largely unknown. We here assessed the preclinical activity of elimusertib in 38 cell lines and 32 patient-derived xenograft (PDX) models derived from common pediatric solid tumor entities. Detailed in vitro and in vivo molecular characterization of the treated models enabled the evaluation of response biomarkers. Pronounced objective response rates were observed for elimusertib monotherapy in PDX, when treated with a regimen currently used in clinical trials. Strikingly, elimusertib showed stronger antitumor effects than some standard-of-care chemotherapies, particularly in alveolar rhabdomysarcoma PDX. Thus, elimusertib has strong preclinical antitumor activity in pediatric solid tumor models, which may translate to clinically meaningful responses in patients.

Parallel sequencing of extrachromosomal circular DNAs and transcriptomes in single cancer cells.

Extrachromosomal DNAs (ecDNAs) are common in cancer, but many questions about their origin, structural dynamics and impact on intratumor heterogeneity are still unresolved. Here we describe single-cell extrachromosomal circular DNA and transcriptome sequencing (scEC&T-seq), a method for parallel sequencing of circular DNAs and full-length mRNA from single cells. By applying scEC&T-seq to cancer cells, we describe intercellular differences in ecDNA content while investigating their structural heterogeneity and transcriptional impact. Oncogene-containing ecDNAs were clonally present in cancer cells and drove intercellular oncogene expression differences. In contrast, other small circular DNAs were exclusive to individual cells, indicating differences in their selection and propagation. Intercellular differences in ecDNA structure pointed to circular recombination as a mechanism of ecDNA evolution. These results demonstrate scEC&T-seq as an approach to systematically characterize both small and large circular DNA in cancer cells, which will facilitate the analysis of these DNA elements in cancer and beyond.

Therapeutic targeting of ATR in alveolar rhabdomyosarcoma.

Despite advances in multi-modal treatment approaches, clinical outcomes of patients suffering from PAX3-FOXO1 fusion oncogene-expressing alveolar rhabdomyosarcoma (ARMS) remain dismal. Here we show that PAX3-FOXO1-expressing ARMS cells are sensitive to pharmacological ataxia telangiectasia and Rad3 related protein (ATR) inhibition. Expression of PAX3-FOXO1 in muscle progenitor cells is not only sufficient to increase sensitivity to ATR inhibition, but PAX3-FOXO1-expressing rhabdomyosarcoma cells also exhibit increased sensitivity to structurally diverse inhibitors of ATR. Mechanistically, ATR inhibition leads to replication stress exacerbation, decreased BRCA1 phosphorylation and reduced homologous recombination-mediated DNA repair pathway activity. Consequently, ATR inhibitor treatment increases sensitivity of ARMS cells to PARP1 inhibition in vitro, and combined treatment with ATR and PARP1 inhibitors induces complete regression of primary patient-derived ARMS xenografts in vivo. Lastly, a genome-wide CRISPR activation screen (CRISPRa) in combination with transcriptional analyses of ATR inhibitor resistant ARMS cells identifies the RAS-MAPK pathway and its targets, the FOS gene family, as inducers of resistance to ATR inhibition. Our findings provide a rationale for upcoming biomarker-driven clinical trials of ATR inhibitors in patients suffering from ARMS.

Enhancer hijacking determines extrachromosomal circular MYCN amplicon architecture in neuroblastoma.

MYCN amplification drives one in six cases of neuroblastoma. The supernumerary gene copies are commonly found on highly rearranged, extrachromosomal circular DNA (ecDNA). The exact amplicon structure has not been described thus far and the functional relevance of its rearrangements is unknown. Here, we analyze the MYCN amplicon structure using short-read and Nanopore sequencing and its chromatin landscape using ChIP-seq, ATAC-seq and Hi-C. This reveals two distinct classes of amplicons which explain the regulatory requirements for MYCN overexpression. The first class always co-amplifies a proximal enhancer driven by the noradrenergic core regulatory circuit (CRC). The second class of MYCN amplicons is characterized by high structural complexity, lacks key local enhancers, and instead contains distal chromosomal fragments harboring CRC-driven enhancers. Thus, ectopic enhancer hijacking can compensate for the loss of local gene regulatory elements and explains a large component of the structural diversity observed in MYCN amplification.

Clinicopathological Characteristics and Prognostic Factors of Patients with Gastric Cancer Accompanying Neuroendocrine Differentiation (NEDGC).

AIM: Gastric carcinoma with neuroendocrine differentiation (NEDGC) is a relatively rare pathologic diagnosis in clinical practice, which has no specific guidelines or treatment recommendations yet. In this study, we aim to investigate the clinicopathological characteristics and prognostic factors of this disease. PATIENTS AND METHODS: We retrospectively analyzed clinicopathological data from a series of 82 NEDGC patients who underwent surgery for gastrectomy at Huashan Hospital Fudan University between January 2007 and December 2018. Furthermore, a series of 50 cases were used to analyze 3-year overall survival (OS). RESULTS: Ages of the patients ranged from 26 to 83 years (M:F, 4.8:1). The majority of patients suffered from some symptoms (97.6%), as the most common one was abdominal pain (48.8%). Most of the tumors were ≥5 cm (53.7%), in the lower part of the stomach (47.5%), and with advanced T (87.8% ≥T3) and N (67.1% ≥N1) stage. As to the neuroendocrine markers, Syn showed a slight advantage on sensitivity than CgA (79.3 and 75.6%, respectively). The 3-year OS was 54%. Advanced T stage (≥T3) of the primary tumor, positive lymphovascular invasion (LVI), large tumor size (5.5cm), high neutrophil-to-lymphocyte ratio (NLR, 2.51), and low prealbumin level (173.87 mg/L) were associated with inferior OS based on the univariate analysis. Low preoperative hemoglobin level (113.87g/L), laparoscopic-assisted gastrectomy, and advanced N stage (N3) were three independent risk factors for 3-year OS of NEDGC patients in both univariate and multivariate analysis. CONCLUSION: The TN staging system for gastric adenocarcinoma also has a prognostic value for NEDGC patients, while N3 stage works as an independent predictor of patients' survival. Since most of the NEDGC patients were in advanced stage, proper indications to perform operative laparoscopy should be selected.

Publisher Correction: Extrachromosomal circular DNA drives oncogenic genome remodeling in neuroblastoma.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Extrachromosomal circular DNA drives oncogenic genome remodeling in neuroblastoma.

Extrachromosomal circularization of DNA is an important genomic feature in cancer. However, the structure, composition and genome-wide frequency of extrachromosomal circular DNA have not yet been profiled extensively. Here, we combine genomic and transcriptomic approaches to describe the landscape of extrachromosomal circular DNA in neuroblastoma, a tumor arising in childhood from primitive cells of the sympathetic nervous system. Our analysis identifies and characterizes a wide catalog of somatically acquired and undescribed extrachromosomal circular DNAs. Moreover, we find that extrachromosomal circular DNAs are an unanticipated major source of somatic rearrangements, contributing to oncogenic remodeling through chimeric circularization and reintegration of circular DNA into the linear genome. Cancer-causing lesions can emerge out of circle-derived rearrangements and are associated with adverse clinical outcome. It is highly probable that circle-derived rearrangements represent an ongoing mutagenic process. Thus, extrachromosomal circular DNAs represent a multihit mutagenic process, with important functional and clinical implications for the origins of genomic remodeling in cancer.

Small-Molecule Dual PLK1 and BRD4 Inhibitors are Active Against Preclinical Models of Pediatric Solid Tumors.

Simultaneous inhibition of multiple molecular targets is an established strategy to improve the continuance of clinical response to therapy. Here, we screened 49 molecules with dual nanomolar inhibitory activity against BRD4 and PLK1, best classified as dual kinase-bromodomain inhibitors, in pediatric tumor cell lines for their antitumor activity. We identified two candidate dual kinase-bromodomain inhibitors with strong and tumor-specific activity against neuroblastoma, medulloblastoma, and rhabdomyosarcoma tumor cells. Dual PLK1 and BRD4 inhibitor treatment suppressed proliferation and induced apoptosis in pediatric tumor cell lines at low nanomolar concentrations. This was associated with reduced MYCN-driven gene expression as assessed by RNA sequencing. Treatment of patient-derived xenografts with dual inhibitor UMB103 led to significant tumor regression. We demonstrate that concurrent inhibition of two central regulators of MYC protein family of protooncogenes, BRD4, and PLK1, with single small molecules has strong and specific antitumor effects in preclinical pediatric cancer models.

Immunization with a peptide mimicking Lipoteichoic acid protects mice against Staphylococcus aureus infection.

Lipoteichoic acid (LTA), a major component of the cell wall of Staphylococcus aureus (S. aureus), is not generally considered as an ideal vaccine candidate since it is a thymus-independent antigen. In this study, we screened a 12-mer phage peptide library and identified a series of peptide sequences that can mimic the epitope of LTA. A tetra-branched multiple antigenic peptide, named MAP2-3, comprising one of the positive peptide sequences (GHKEDRQWCQHS), was synthesized. Immunization with MAP2-3 induced LTA-specific IgG antibodies, prolonged the survival time, and decreased the bacterial burden in organs of mice infected with S. aureus. Moreover, passive immunization with polyclonal anti-MAP2-3 sera reduced bacterial load in organs of mice with bacteremia, alleviated acute lung injury in mice with pneumonia, and decreased the size of lesions in mice with skin infection. The number of LTA-specific antibody-secreting cells in the spleen of MAP2-3 immunized mice were significantly higher than that in the control mice. In summary, as a surrogate of LTA, vaccination with MAP2-3 elicited humoral immune response and protected mice from S. aureus infection. This study provides a new option to design vaccines against S. aureus.

The failure of non-invasive prenatal testing due to maternal dermatomyositis.

We experienced a case of a pregnant woman who failed to obtain a result from NIPT, due to the high level of total cell-free DNA. A subsequent ultrasound examination discovered that the fetus had severe intrauterine growth restriction, so the woman decided to abort the baby. At the same time, the woman developed slight swelling and tenderness of the proximal interphalangeal and meta-carpophalangeal joints. At first, these symptoms were not noticed, but, when the pregnant woman was admitted to the hospital, her laboratory tests were seriously abnormal, such as serum lactate dehydrogenase (640U/L), creatine phosphor kinase (4525U/L), kinase isoenzyme MB (170U/L), and a hydroxybutyrate dehydrogenase (398U/L). The patient had no other symptoms at this time. Misoprostol and subsequent forceps curettage were used for the induced abortion, a 167-g female fetus was aborted. Fetal skin tissue was taken for chromosomal microarray analysis (CMA) and placenta (biopsied in four places and tested as two composite samples) were taken for postnatal karyotyping to exclude a confined placental mosaicism, chromosomal microarray analysis of the fetal skin tissue revealed that the karyotype was 46, XX, karyotyping of placenta (100 cells) gave results of 46, XX, no abnormalities were detected. Ten days after induction, the patient had developed progressive symmetric muscle weakness in the proximal extremities. Physical examination revealed Gottron's sign and erythema. A manual muscle test showed weakness of the muscles (4/5) of her proximal extremities. Electromyography showed myogenic impairment. After excluding the possibility of neoplasia, the patient was diagnosed with dermatomyositis.

Prohibitin promotes de-differentiation and is a potential therapeutic target in neuroblastoma.

Gain of the long arm of chromosome 17 (17q) is a cytogenetic hallmark of high-risk neuroblastoma, yet its contribution to neuroblastoma pathogenesis remains incompletely understood. Combining whole-genome and RNA sequencing of neuroblastomas, we identified the prohibitin (PHB) gene as highly expressed in tumors with 17q gain. High PHB expression correlated with poor prognosis and was associated with loss of gene expression programs promoting neuronal development and differentiation. PHB depletion induced differentiation and apoptosis and slowed cell cycle progression of neuroblastoma cells, at least in part through impaired ERK1/2 activation. Conversely, ectopic expression of PHB was sufficient to increase proliferation of neuroblastoma cells and was associated with suppression of markers associated with neuronal differentiation and favorable neuroblastoma outcome. Thus, PHB is a 17q oncogene in neuroblastoma that promotes tumor cell proliferation, and de-differentiation.

Synergistic activity of BET inhibitor MK-8628 and PLK inhibitor Volasertib in preclinical models of medulloblastoma.

Medulloblastoma is the most prevalent central nervous system tumor in children. Targeted treatment approaches for patients with high-risk medulloblastoma are needed as current treatment regimens are not curative in many cases and cause significant therapy-related morbidity. Medulloblastoma harboring MYC amplification have the most aggressive clinical course and worst outcome. Targeting the BET protein BRD4 has significant anti-tumor effects in preclinical models of MYC-amplified medulloblastoma, however, in most cases these are not curative. We here assessed the therapeutic efficacy of the orally bioavailable BRD4 inhibitor, MK-8628, in preclinical models of medulloblastoma. MK-8628 showed therapeutic efficacy against in vitro and in vivo models of MYC-amplified medulloblastoma by inducing apoptotic cell death and cell cycle arrest. Gene expression analysis of cells treated with MK-8628 showed that anti-tumor effects were accompanied by significant repression of MYC transcription as well as disruption of MYC-regulated transcriptional programs. Additionally, we found that targeting of MYC protein stability through pharmacological PLK1 inhibition showed synergistic anti-medulloblastoma effects when combined with MK-8628 treatment. Thus, MK-8628 is effective against preclinical high-risk medulloblastoma models and its effects can be enhanced through simultaneous targeting of PLK1.

Circadian gene hCLOCK contributes to progression of colorectal carcinoma and is directly regulated by tumor­suppressive microRNA­124.

An abundance of studies has demonstrated that disruption of circadian rhythms is one of the factors that may contribute to the initiation and development of human colorectal carcinomas (CRCs). Recently, microRNA­124 has been demonstrated to suppress tumor growth or metastasis of CRCs. However, the mechanisms of cross­talk between microRNA­124 (miR­124) and circadian rhythms in the regulation of CRCs are poorly understood. The present study demonstrated that the protein expression levels of human circadian locomoter output cycles protein kaput (hCLOCK) is significantly increased, while miR­124 is attenuated in high­grade human CRC tissues and in the more invasive colorectal cancer cell lines SW620 and LOVO. It was further demonstrated that hCLOCK is a direct target of miR­124. Upregulation of miR­124 significantly inhibited hCLOCK expression in LOVO cells, and consequently inhibited its promoting effects on the proliferation and migration of LOVO cells. In conclusion, these data revealed that hCLOCK serves an enhancing role, whereas mir­124 serves a suppressive role, in human CRC. Attenuation of miR­124, of which hCLOCK is a direct target, leads to increased hCLOCK expression and disruption of circadian rhythms in CRC.

A novel method of self-pulling and latter transected delta-shaped Billroth-I anastomosis in totally laparoscopic distal gastrectomy.

BACKGROUND: We developed a modified delta-shaped gastroduodenostomy technique in totally laparoscopic distal gastrectomy. This novel technique, which effectively reduces the required quantity of linear stapler [1-3], was named as self-pulling and latter transected delta-shaped anastomosis (Delta SPLT) [4]. METHODS: Delta SPLT was performed on 15 patients with stage cT1-2 antral cancer. We ligated the duodenum with a rope instead of transecting it and used the ligature rope to pull the duodenum during the whole progress of gastroduodenostomy. When closing the entry hole, the duodenum was transected at the same time, which saved one linear stapler. Data of clinicopathologic characteristics, surgical and postoperative outcomes were collected and expressed as means ± standard deviations. RESULTS: All the operations were successfully performed by using no more than four 60-mm linear staplers. The mean BMI of the patients is 23.0 ± 2.5 kg/m2 (range 17.0-26.0 kg/m2), and duration of the operation was 115.0 ± 33.4 min (range 75-215 min), including 22.3 ± 6.7 min (range 15-35 min) of reconstruction. Mean blood loss was 82.7 ± 71.3 mL (range 10-300 mL), and mean times to first flatus was 2.3 ± 1.1 days (range 1-5 days). A mean number of 27.5 ± 5.4 (range 18-38) lymph nodes was retrieved. Overall postoperative morbidity rate was 6.7% (1/15). There was no anastomosis-related complication, but one case of pneumonia developed on postoperative day (POD) 2 which was successfully managed by conservative methods. Patients were discharged (POD mean 5.8 ± 1.3, range 4-9) when their bowel movements recovered and no discomfort with soft diet was claimed. CONCLUSION: Delta SPLT is a safe and feasible technique and requires less clinical costs.

A novel method of self-pulling and latter transected reconstruction in totally laparoscopic total gastrectomy: feasibility and short-term safety.

BACKGROUND: This study depicts a novel reconstruction method of self-pulling and latter transection (SPLT) in totally laparoscopic total gastrectomy (TLTG) and evaluates its feasibility and short-term safety by comparing its surgical and postoperative outcomes with the conventional TLTG. PATIENTS AND METHODS: Forty patients with gastric cancer from June 2014 to December 2015 received SPLT-TLTG. Data of clinicopathologic characteristics, surgical and postoperative outcomes, and follow-up findings in SPLT cases were collected and retrospectively compared with those of conventional TLTG to clarify the clinical benefits. RESULTS: The mean duration of the operation was 179.5 ± 37.7 min in SPLT-TLTG, including 23.2 ± 8.8 min of reconstruction; both were significantly shorter than the conventional TLTG (P = 0.030; P < 0.001). There were no significant differences in blood loss, time of the first flatus and postoperative hospital stays between two groups. SPLT-TLTG developed no complication beyond the conventional TLTG. CONCLUSION: SPLT-TLTG is safe, feasible and minimally invasive. It may serve as a promising procedure for gastric cancer that helps to expand the indication of TLTG to cases with even high level of tumor invasion and requires less in both surgical skills and clinical costs.

A Multiple Antigenic Peptide Mimicking Peptidoglycan Induced T Cell Responses to Protect Mice from Systemic Infection with Staphylococcus aureus.

Due to the enormous capacity of Staphylococcus aureus to acquire antibiotic resistance, it becomes imperative to develop vaccines for decreasing the risk of its life-threatening infections. Peptidoglycan (PGN) is a conserved and major component of S. aureus cell wall. However, it has not been used as a vaccine candidate since it is a thymus-independent antigen. In this study, we synthesized a multiple antigenic peptide, named MAP27, which comprised four copies of a peptide that mimics the epitope of PGN. After immunization with MAP27 five times and boosting with heat-inactivated bacterium one time, anti-MAP27 serum bound directly to S. aureus or PGN. Immunization with MAP27 decreased the bacterial burden in organs of BALB/c mice and significantly prolonged their survival time after S. aureus lethal-challenge. The percentage of IFN-γ(+)CD3(+) T cells and IL-17(+)CD4(+) T cells in spleen, as well as the levels of IFN-γ, IL-17A/F and CCL3 in spleen and lung, significantly increased in the MAP27-immunized mice after infection. Moreover, in vitro incubation of heat-inactivated S. aureus with splenocytes isolated from MAP27-immunized mice stimulated the production of IFN-γ and IL-17A/F. Our findings demonstrated that MAP27, as a thymus-dependent antigen, is efficient at eliciting T cell-mediated responses to protect mice from S. aureus infection. This study sheds light on a possible strategy to design vaccines against S. aureus.

MiR-222 overexpression promotes proliferation of human hepatocellular carcinoma HepG2 cells by downregulating p27.

OBJECTIVE: Hepatocellular carcinoma (HCC) represents the third leading cause of cancer-related death worldwide. Increasing evidence suggests that microRNAs, a novel class of non-coding RNAs that function as endogenous suppressors of gene expression, are deregulated in HCC. Although microRNA-222 (miR-222) overexpression has been described in HCC, the role of miR-222 and its target genes in the proliferation of hepatocellular carcinoma cells remain poorly elucidated. METHODS: HepG2 cells were transfected with miR-222 mimic, inhibitor or their negative controls. Cell proliferation was assessed by Cell Counting Kit-8 (CCK-8) and EdU incorporation assay. Flow cytometry was performed to assess the effects of miR-222 on HepG2 cell cycle progression. MiR-222 and putative targets genes (p27 and p57) expression levels were determined using qRT-PCR and/or Western blot. RESULTS: MiR-222 overexpression induced an enhancement of HepG2 cell proliferation in vitro, paralleling with an altered cell cycle progression via increased cell population in S phase. P27 expression, other than p57, was negatively regulated by miR-222 overexpression at post-transcriptional level in HepG2 cells. Transfection of either small interfering RNA (siRNA) for p27 or miR-222 mimic increased HepG2 cell proliferation rate, whereas co-transfection of p27 siRNA and miR-222 mimic did not further enhance HepG2 cell proliferation in comparison with the cells transfected with p27 siRNA or miR-222 mimic alone, validating that p27 is a target gene of miR-222 during HepG2 cell proliferation. CONCLUSION: This study suggests that miR-222 overexpression promotes HepG2 cell proliferation by downregulating p27.

[A Paralytic shellfish poisoning GTX2,3 mimic peptide isolated from phage display: characterization and potential applications].

AIM: To screen peptide mimics of PSP (Paralytic shellfish poisoning) GTX2,3 from a random 12-mer phage display peptide library and to identify and characterize the specificity and accuracy of the peptide mimotope of GTX2,3. METHODS: The monoclonal antibody against GTX2,3 (mAb E(9);F(10);) was used as a target to screen the 12-mer phage display peptide library and the specificity of phage clones were identified by sandwich ELISA and blocking assay. The peptide sequences of positive phage clones were determined and analyzed by DNA sequencing. The affinity and specificity of synthetic peptide were identified by a competitive ELISA. RESULTS: The 20 clones were identified to be specific reactivity with the mAb E(9);F(10);. Amino acid sequence analysis revealed seven different types of mimotope sequence, most of which contained a common motif DXLXPP(X presents random acid amino), X was random amino acid. The Phage No.2(phage 2), the clone with mimotope sequence WPSLDXLXPPSY showed the strongest binding, and inhibited the reactivity of the mAb with GTX2,3. Another ELISA result showed that synthetic peptide-1 (SP-1) which contain mimotope amino acid sequence was able to inhibit the mAb- GTX2,3 interaction. CONCLUSION: The mimotope peptide of GTX2,3 is obtained by using the phage display technology. The results also showed that SP-1 bind to mAb E(9);F(10); at the same site as GTX2,3.