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Nodal peripheral T cell lymphomas (PTCLs) are challenging subsets of non-Hodgkin lymphomas characterized by their heterogeneity and aggressive clinical behavior. Given the mixed outcomes reported in previous studies, the efficacy of autologous hematopoietic cell transplantation (auto-HCT) as a consolidation strategy following initial chemotherapy response remains uncertain. This study aims to evaluate the impact of upfront auto-HCT consolidation on overall survival (OS) and event-free survival (EFS) among patients with nodal PTCL who achieved a complete or partial response to initial chemotherapy. A retrospective cohort study was conducted at Moffitt Cancer Center, involving 123 patients with nodal PTCL treated between February 2005 and February 2021. Patients were stratified into 2 groups based on whether they received auto-HCT as part of their initial treatment strategy. Kaplan-Meier method and Cox proportional hazard models were used for statistical analysis to compare OS and EFS between groups. Patients undergoing auto-HCT after first response demonstrated significantly longer median OS (12.3 versus 4.3 yr; P = .035) and EFS (6.2 versus 2.2 yr; P = .003) compared to those who did not. Multivariate analyses indicated that auto-HCT at first response and younger age at diagnosis were favorable prognostic factors. The findings suggest that upfront auto-HCT consolidation can significantly improve long-term outcomes in patients with nodal PTCL, supporting the strategy of early auto-HCT consideration and referral following initial chemotherapy response. These results underscore the importance of integrating upfront auto-HCT into the treatment paradigm for nodal PTCL, emphasizing early referral to transplantation services to optimize patient outcomes.
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Trasplante de Células Madre Hematopoyéticas , Linfoma de Células T Periférico , Trasplante Autólogo , Humanos , Linfoma de Células T Periférico/terapia , Linfoma de Células T Periférico/mortalidad , Trasplante de Células Madre Hematopoyéticas/mortalidad , Femenino , Masculino , Persona de Mediana Edad , Adulto , Estudios Retrospectivos , Anciano , Adulto Joven , Resultado del TratamientoRESUMEN
BACKGROUND: Complement-mediated thrombotic microangiopathy (CM-TMA), also called atypical hemolytic uremic syndrome (aHUS), is a difficult-to-diagnose rare disease that carries severe morbidity and mortality. Anti-C5 monoclonal antibodies (aC5-mab) are standard treatments, but large studies and long-term data are scarce. Here, we report our single institution experience to augment the knowledge of CM-TMA treated with aC5-mab therapy. METHODS: We aimed to assess the short and long-term effects of aC5-mab in patients diagnosed with CM-TMA treated outside of a clinical trial. This was a retrospective study. We included all patients diagnosed with CM-TMA and treated with aC5-mab at our institution. There were no exclusion criteria. Endpoints included complete TMA response (CR) defined as normalization of hematological parameters and ≥25% improvement in serum creatinine (Cr) from baseline in patients with renal disease, relapse defined as losing the previously achieved CR, morbidity, adverse events, and survival. RESULTS: We found 28 patients with CM-TMA treated with aC5-mab. The median age was 50 years. Baseline laboratories: platelet counts 93 × 109 /L, hemoglobin 8.6 g/dL, lactate dehydrogenase 1326 U/L, serum Cr 4.7 mg/dL, and estimated glomerular filtration rate 19 mL/min. One individual was on renal replacement therapy (RRT) and 10 initiated RRT within 5 days of the first dose of aC5-mab. Genetic variants associated with CM-TMA included mutations in C3, CFB, CFH, CFHR1/3, CFI, and MCP. The mean duration of hospitalization was 24 days. The median time to initiation of aC5-mab was 10 days. Sixteen subjects received RRT. At the time of hospital discharge, 27 were alive, 14 remained on RRT, and 4 had a CR. At 6 months, 23 patients were alive, 18 continued aC5-mab, 8 remained on RRT, and 9 had a CR. At the last follow-up visit past 6 months, 20 were alive, 14 continued aC5-mab, 5 remained on RRT, 12 had a CR, and 1 was lost to follow-up. CONCLUSIONS: Our study provides real-world experience and insight into the long-term outcomes of CM-TMA treated with aC5-mab. Our findings validate that CM-TMA is an aggressive disease with significant morbidity and mortality, and confirm that aC5-mab is a relatively effective therapy for CM-TMA. Our study adds practical, real-world experience to the literature, but future research remains imperative.
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Síndrome Hemolítico Urémico Atípico , Proteínas Inactivadoras de Complemento , Microangiopatías Trombóticas , Humanos , Persona de Mediana Edad , Estudios Retrospectivos , Microangiopatías Trombóticas/diagnóstico , Microangiopatías Trombóticas/tratamiento farmacológico , Microangiopatías Trombóticas/etiología , Síndrome Hemolítico Urémico Atípico/tratamiento farmacológico , Síndrome Hemolítico Urémico Atípico/genética , Proteínas del Sistema ComplementoRESUMEN
Lumbar punctures (LP) are routinely used to administer intrathecal chemotherapy for children and adults with hematologic malignancies. The current guidelines suggest a platelet threshold of ≥ 50 × 109/L prior to LP for intrathecal chemotherapy (ITC). This can be challenging in patients with hematological malignancies who are thrombocytopenic. We conducted a retrospective chart review of 900 LPs for ITC and compared adverse events in patients with a platelet count of ≥ 50 × 109/L and < 50 × 109/L. Cohort 1 included 682 LPs (75.8%) with a pre-procedure platelet count ≥ 50 × 109/L, and cohort 2 included 218 LPs (24.2%) with a pre-procedure platelet count < 50 × 109/L. Cohort 2 was further subdivided into pre-procedure platelet counts of 41 × 109/L-49 × 109/L (n = 43), 31 × 109/L-40 × 109/L (n = 77), 21 × 109/L-30 × 109/L (n = 84), and 11 × 109/L-20 × 109/L (n = 14). Among 900 LP procedures, a pre-procedure platelet count < 50 × 109/L did not demonstrate a higher rate of post-procedure adverse events (6.5% vs 6.8%, p = 0.8237). When cohort 2 was further stratified, the cohort with a pre-procedure platelet count of 21 × 109/L-30 × 109/L had the highest percentage of complications from LP (9.5%) and the highest rates of traumatic taps with observed LP RBC count > 200 (35.7%, p = 0.0015). The rate of red blood cells (RBC) in the CSF was significantly higher in the group with platelets < 50 × 109/L with observed LP RBC count ≥ 200 (31.2% vs 20.5%, p = 0.0016), ≥ 500 (27.1% vs 14.6%, p < 0.0001), and ≥ 1000 (23% vs 11.6%, p < 0.0001). No instances of epidural hematomas were seen. We found no significant difference in bleeding complications between patients undergoing LPs for ITC with a platelet count above or below 50 × 109/L.
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Neoplasias Hematológicas , Trombocitopenia , Niño , Adulto , Humanos , Punción Espinal/efectos adversos , Estudios Retrospectivos , Trombocitopenia/etiología , Lipopolisacáridos , Transfusión de Plaquetas , Neoplasias Hematológicas/complicacionesRESUMEN
BACKGROUND: CPX-351 was approved by the FDA in 2017 as frontline induction chemotherapy for patients aged ≥18 years with newly diagnosed acute myeloid leukemia (AML) which includes myelodysplasia-related changes (AML-MRC) and therapy-related acute myeloid leukemia (t-AML). The efficacy of CPX-351 among younger patients (aged <60 years) is currently unclear, as the large, randomized phase 3 study that led to approval of CPX-351 only included patients between the ages of 60 and 75 years. METHODS: We performed a retrospective study of clinical and molecular data from adult patients with newly diagnosed AML-MRC or t-AML treated with CPX-351. Patients were divided into 2 cohorts: aged <60 years (cohort A) and aged ≥60 years (cohort B). We compared overall response rate (ORR) and median overall survival (mOS) between the cohorts. RESULTS: Of 169 evaluable patients, 21.3% were in cohort A and 78.7% were in cohort B. ORR of the entire cohort was 53.3%; ORR of cohort A was 47.2% compared with 54.9% for cohort B (P = .46). Overall, 54.4% of responding patients proceeded to allogenic stem cell transplant (allo-SCT), including 52.9% of patients in cohort A and 54.8% in cohort B (P = 1.00). At a median follow-up of 24 months, mOS of the entire cohort was 16 months and was similar between cohorts A and B (18 vs. 15 months, respectively; P = .29). CONCLUSION: CPX-351 resulted in similar response rates and survival outcomes among both younger and older adult patients with newly diagnosed AML-MRC or t-AML.
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Leucemia Mieloide Aguda , Neoplasias Primarias Secundarias , Adolescente , Adulto , Anciano , Citarabina/uso terapéutico , Daunorrubicina/uso terapéutico , Humanos , Leucemia Mieloide Aguda/tratamiento farmacológico , Persona de Mediana Edad , Estudios RetrospectivosRESUMEN
Caplacizumab prevents platelet adhesion and has been approved for acquired thrombotic thrombocytopenic purpura (aTTP). This study was retrospective, including all patients diagnosed with aTTP and treated with caplacizumab since commercial availability in 2019 until 28 February 2021 at a single academic hospital with no exclusion criteria. Results used definitions for outcomes in aTTP from the International Working Group Consensus. Ten patients with aTTP received caplacizumab. The median age was 52 years. Six (60%) patients had refractory aTTP while 4 (40%) had newly diagnosed aTTP. The median laboratory values prior to therapy demonstrated: platelet count (PC) 29/uL, LDH 518 U/L (182-1850), ADAMTS13 activity 3% and ADAMTS13 inhibitor 1.4 BU. Everyone received glucocorticoids, rituximab, therapeutic plasma exchange (TPE) and caplacizumab. The median number of TPE was 12 days. Caplacizumab was started at a median of 5 days after the first TPE and the median treatment duration was 31 days. Normalization of PC, LDH and ADAMTS13 activity in days were 5, 3.5, and 32.5, respectively. Six (60%) patients achieved complete response, 3 (30%) had refractory disease and 1 (10%) had relapsed aTTP. No subject suffered abnormal bleeding, or thrombotic event. There were no deaths. Caplacizumab with TPE, glucocorticoids and rituximab was a safe and effective therapy for aTTP.
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Pancytopenia and neutropenia due to coronavirus disease 2019 (COVID-19) are rare. Here we report a case of neutropenia as a sequela of COVID-19 with concern for bone marrow infiltration. The patient was successfully treated with granulocyte colony-stimulating factor.
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Taxanes and anthracyclines have been among the best-studied chemotherapy classes in castration-resistant prostate cancer (CRPC). Docetaxel (D) 75 mg/m2 every 3 weeks has been the standard first line chemotherapy for CRPC. Encapsulation of doxorubicin in polyethylene glycol-coated liposomes (PLD) was developed to enhance the safety and efficacy of conventional doxorubicin. We hypothesize that the combination of weekly low dose-D and PLD would result in a high response rate and low toxicity. Eligibility criteria included metastatic progressive CRPC, no prior D or PLD and good organ function. After a short phase I with no dose-limiting toxicity, D 30 mg/m2 was administered on days 1, 8 and 15; and PLD 30 mg/m2 on day 1 only, every 28 days. Thirty-seven patients were enrolled. The PSA response rate was 53%. Twenty-two subjects had measurable disease; one (5%) achieved complete response, five (23%) partial response, and twelve (54%) stable disease. Twenty-seven patients (73%) manifested pain relief. The median time to progression was 3.7 months for all patients and 7.9 months for responders. Median overall survival was 16.3 months. Grade 4 neutropenia without infection and anemia occurred in 1 patient each. Grade 3 treatment-related toxicities included: 15% fatigue; 9% neutropenia, anemia and nausea; 6% dehydration and hand-foot syndrome; and 3% infection, febrile neutropenia, thrombosis, stomatitis, headache, vomiting, weight loss and weakness. In this non-comparative study D-PLD demonstrated a higher activity than previously reported with single agent D with favorable side effect profile. A phase 3 study would be needed to evaluate the true benefit of this combination.ClinicalTrials.gov Identifier: NCT00456989.
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Adenocarcinoma/tratamiento farmacológico , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Docetaxel/administración & dosificación , Doxorrubicina/análogos & derivados , Neoplasias de la Próstata Resistentes a la Castración/tratamiento farmacológico , Anciano , Anciano de 80 o más Años , Doxorrubicina/administración & dosificación , Humanos , Masculino , Persona de Mediana Edad , Polietilenglicoles/administración & dosificación , Resultado del TratamientoRESUMEN
Current management of locoregional and oligometastatic melanoma is typically with surgery; however, some patients are unable to undergo resection due to location/size of their tumors and/or the anticipated morbidity of the surgery. While there are currently no established guidelines for neoadjuvant therapy in melanoma, neoadjuvant BRAF-targeted therapy may make resection more feasible. A retrospective analysis was conducted of 23 patients with BRAFV600-mutant, stage III/IV melanoma treated with BRAF-targeted therapy prior to surgery, with no adjuvant treatment. Surgical specimens, preoperative imaging, and clinical outcomes were evaluated. Results: Ten of 23 patients (44%) attained a pathologic complete response (pCR), with no correlation between RECIST response based on preoperative imaging and pathologic response. After a median of 43-month follow-up, only 1 patient (10%) with a pCR recurred, while 8 of 13 (62%) patients without a pCR recurred. Patients with a pCR had significantly improved relapse-free (RFS) and overall survival (OS) compared to patients with residual tumor. Neoadjuvant BRAF-targeted therapy is associated with a high pCR rate in patients with stage III-IV melanoma, which may correlate with improved RFS and OS.
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Melanoma/patología , Melanoma/terapia , Terapia Molecular Dirigida , Terapia Neoadyuvante , Proteínas Proto-Oncogénicas B-raf/antagonistas & inhibidores , Adulto , Anciano , Supervivencia sin Enfermedad , Femenino , Humanos , Imidazoles/farmacología , Imidazoles/uso terapéutico , Masculino , Melanoma/diagnóstico por imagen , Persona de Mediana Edad , Metástasis de la Neoplasia , Estadificación de Neoplasias , Oximas/farmacología , Oximas/uso terapéutico , Proteínas Proto-Oncogénicas B-raf/metabolismo , Piridonas/farmacología , Piridonas/uso terapéutico , Pirimidinonas/farmacología , Pirimidinonas/uso terapéutico , Resultado del TratamientoRESUMEN
Hepatocellular carcinoma (HCC) is an aggressive tumor that often arises in the setting of liver cirrhosis. Although early-stage disease is often amenable for surgical resection, transplant, or locoregional therapies, many patients are diagnosed at an advanced stage or have poor liver reserve. Systemic therapy is the mainstay of treatment for these patients. At present, the only approved therapy for the treatment of advanced disease is the tyrosine multikinase inhibitor sorafenib. Candidacy for treatment is based on liver reserve. Novel agents for the treatment of this disease are urgently needed. In this article, we review systemic therapy trials and upcoming data for the treatment of HCC.
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Carcinoma Hepatocelular/terapia , Neoplasias Hepáticas/terapia , Carcinoma Hepatocelular/patología , Humanos , Neoplasias Hepáticas/patologíaAsunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Linfoma de Células B Grandes Difuso/tratamiento farmacológico , Albúmina Sérica/metabolismo , Anticuerpos Monoclonales de Origen Murino/administración & dosificación , Ciclofosfamida/administración & dosificación , Doxorrubicina/administración & dosificación , Esquema de Medicación , Femenino , Humanos , Linfoma de Células B Grandes Difuso/sangre , Linfoma de Células B Grandes Difuso/diagnóstico , Masculino , Evaluación de Resultado en la Atención de Salud/estadística & datos numéricos , Valor Predictivo de las Pruebas , Prednisona/administración & dosificación , Pronóstico , Modelos de Riesgos Proporcionales , Rituximab , Análisis de Supervivencia , Vincristina/administración & dosificaciónRESUMEN
BACKGROUND: Neoadjuvant chemotherapy (NACT) is used in breast cancer to evaluate the response to treatment. We examined the usefulness of breast magnetic resonance imaging (MRI) in the evaluation of tumor response after NACT. METHODS: Breast MRIs of 87 women with MRI after NACT were reviewed. The Spearman coefficient was used for estimating the correlation between MRI and pathologic tumor sizes (ypTs). RESULTS: The median age was 50 years (range 25 to 83 years). The median MRI size was 1.25 cm (range 0 to 10 cm). The median ypT was 1.20 cm (range 0 to 10.4 cm). The Spearman coefficient between MRI and ypT was .78 (95% confidence interval, .67 to .85; P < .0001). MRI was found to have a positive predictive value of 92% and a negative predictive value of 64% for residual in-breast disease. The sensitivity and specificity of MRI were 86% and 77%, respectively. CONCLUSIONS: MRI correlates well with the final pathology and can be a useful modality to predict residual disease after NACT and aid in surgical planning.
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Neoplasias de la Mama/patología , Neoplasias de la Mama/terapia , Imagen por Resonancia Magnética , Terapia Neoadyuvante , Adulto , Anciano , Anciano de 80 o más Años , Neoplasias de la Mama/metabolismo , Carcinoma in Situ/metabolismo , Carcinoma in Situ/patología , Carcinoma in Situ/terapia , Carcinoma Ductal de Mama/metabolismo , Carcinoma Ductal de Mama/patología , Carcinoma Ductal de Mama/terapia , Carcinoma Lobular/metabolismo , Carcinoma Lobular/patología , Carcinoma Lobular/terapia , Quimioterapia Adyuvante , Femenino , Humanos , Mastectomía , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Receptor ErbB-2/metabolismo , Estudios Retrospectivos , Sensibilidad y Especificidad , Neoplasias de la Mama Triple Negativas/patología , Neoplasias de la Mama Triple Negativas/terapiaRESUMEN
PURPOSE: Preoperative axillary sonography with fine needle aspiration (FNA) in patients with invasive breast cancer identifies patients with nodal metastasis who can be spared further surgery. Indiscriminate use of the diagnostic modality can increase costs and yield inaccurate results. We evaluate the costs associated with the use of highly sensitive axillary ultrasonography in patients with stage ≥T2 tumors. PATIENTS AND METHODS: We constructed a decision analysis tree using TreeAge Pro 2009 software comparing direct hospital charges between patients with and without routine use of axillary ultrasound. Base case estimates were derived from our institutional data and compared with those derived from the literature. One- and two-way sensitivity analyses were performed to check the validity of our inferences. RESULTS: We found that, for the base case estimate with 35% lymph node positivity in stage ≥T2 tumors and sensitivity of the axillary ultrasound set at 86% with a specificity of 40%, the strategy to perform preoperative axillary ultrasound yielded rollback costs of $15,215, compared with $15,940 for surgery plus sentinel lymph node biopsy (cost difference, $725 per patient favoring axillary ultrasound). On two-way sensitivity analysis, the cost benefit for axillary ultrasound was not seen in patients with a low risk for nodal metastasis. CONCLUSION: The adoption of routine preoperative axillary sonography with FNA is a lower-cost strategy than conventional strategies in patients with stage ≥T2 invasive breast cancer.
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Neoplasias de la Mama/diagnóstico por imagen , Neoplasias de la Mama/economía , Ultrasonografía Mamaria/economía , Axila/diagnóstico por imagen , Axila/patología , Axila/cirugía , Biopsia con Aguja Fina/economía , Neoplasias de la Mama/patología , Neoplasias de la Mama/cirugía , Árboles de Decisión , Femenino , Humanos , Ganglios Linfáticos/diagnóstico por imagen , Ganglios Linfáticos/patología , Metástasis Linfática , Modelos EconómicosRESUMEN
BACKGROUND: Axillary ultrasound (AUS) with needle biopsy is used to detect metastasis in patients with invasive breast cancers. Our hypothesis is that preoperative AUS significantly reduces sentinel node biopsy (SLNB) use in patients with invasive breast tumors >2 cm upon clinical examination. METHODS: A single-institution database of patients with breast cancer and AUS was reviewed. Patients with incomplete records, clinical tumor <2 cm, or postoperative AUS were excluded. A control cohort of non-AUS patients with clinical T2 (cT2) or greater disease was identified. Clinicopathologic data were collected. Simple Kappa coefficient and chi-square statistical analyses were performed. RESULTS: AUS was performed in 153 patients vs. 370 controls. Of AUS patients, 112 (73.2%) had cT2 disease vs. 272 (73.5%) controls. Median AUS patient age was 53.7 (range, 22.8-85.8) years vs. 53.8 (range, 26.7-91.6) years; median pathologic tumor was 3.8 (range, 1.0-20.0) cm in AUS patients vs. 2.5 (range, 0.1-11.0) cm. Among AUS patients, 78% had needle biopsy; 85 of 120 (70.8%) were positive. Sixty-eight patients had SLNB: 33 after negative AUS and 35 after negative needle biopsy. Twenty-three SLNB (37.3%) were positive; 15 of 33 after negative AUS and 8 of 35 after a negative needle biopsy. Axillary dissection was performed in 102 of 153 vs. 225 of 370 controls. Sensitivity and specificity of AUS was 86.2% and 40.5%. Sensitivity of AUS plus needle biopsy was 89.3% with 100% specificity. Neoadjuvant chemotherapy was given to 49.7% of AUS patients. AUS reduced costs by more than $4,000 per patient. CONCLUSIONS: AUS reduces SLNB use and affects treatment in patients with cT2 or greater breast cancer. Routine AUS should be considered in this population.
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Neoplasias de la Mama/diagnóstico por imagen , Neoplasias de la Mama/patología , Ultrasonografía Mamaria , Adulto , Anciano , Anciano de 80 o más Años , Axila , Femenino , Estudios de Seguimiento , Humanos , Metástasis Linfática , Persona de Mediana Edad , Invasividad Neoplásica , Estadificación de Neoplasias , Pronóstico , Sensibilidad y Especificidad , Biopsia del Ganglio Linfático Centinela , Adulto JovenRESUMEN
Methods to prime human CD4(+) T cells in vitro would be of significant value for the pre-clinical evaluation of vaccine candidates and other immunotherapeutics. However, to date, there is no reliable method for the induction of primary human T cell responses in the laboratory. Here, we optimized a culture strategy incorporating highly purified lymphocytes and dendritic cells, in the absence of any exogenous growth factors, for the in vitro sensitization of naïve CD4(+) T cells against a variety of protein antigens. This fully autologous approach, which was superior to the more traditional PBMC assay for supporting the induction of primary human T helper cell responses in culture, elicited effector cells capable of producing a variety of Th cytokines, including IFNgamma, TNFalpha, IL-2, IL-5, IL-17 and IL-21, and memory cells that could be restimulated multiple times with a specific antigen. Through simple modifications to this culture method, we evaluated the role of dendritic cell maturation state and regulatory T cells on the sensitization of naïve T helper cells, which highlights its utility for addressing basic questions of human immunobiology. Finally, using the formulated yellow fever vaccine, YF-VAX (R), we provide a proof-of-concept demonstration of the utility of the system for evaluating the T cell immunogenicity of vaccine candidates in a pre-clinical setting.
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Linfocitos T CD4-Positivos/inmunología , Células Dendríticas/inmunología , Ensayo de Inmunoadsorción Enzimática , Activación de Linfocitos , Presentación de Antígeno , Separación Celular , Células Cultivadas , Técnicas de Cocultivo , Humanos , Memoria Inmunológica , Interferón gamma/metabolismo , Interleucinas/metabolismo , Linfocitos T Colaboradores-Inductores/inmunología , Linfocitos T Reguladores/inmunología , Factor de Necrosis Tumoral alfa/metabolismo , Vacunas de Subunidad/inmunología , Vacuna contra la Fiebre Amarilla/inmunologíaRESUMEN
Eosinophilic esophagitis is an under-recognized inflammatory disorder of the esophagus. It has been frequently diagnosed in pediatric patients; however, over the last few years, there has been an increase in the number of cases recognized in adults as well. Despite this fact, eosinophilic esophagitis (EE) is often a delayed diagnosis in the primary care setting due to the overlapping symptoms it shares with other esophageal and gastrointestinal disorders such as gastroesophageal reflux disease and gastroenteritis, as well as a lack of awareness among physicians who see adult patients. We performed an exhaustive search of the literature, which revealed over 400 articles on EE; however, most were reported in gastroenterology or autoimmune specialty journals. We report a case of eosinophilic esophagitis in a 39-year-old man who presented with persistent epigastric abdominal pain and who was diagnosed via endoscopy and biopsy.
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Isoprenylated proteins have important functions in cell growth and differentiation of eukaryotic cells. Inhibitors of protein prenylation in malaria have recently shown strong promise as effective antimalarials. In studying protein prenylation in the malaria protozoan parasite Plasmodium falciparum, we have shown earlier that the incubation of P. falciparum cells with (3)H-prenol precursors resulted in various size classes of labeled proteins. To understand the physiological function of prenylated proteins of malaria parasites, that are targets of prenyltransferase inhibitors, we searched the PlasmoDB database for proteins containing the C-terminus prenylation motif. We have identified, among other potentially prenylated proteins, an orthologue of a PRL (protein of regenerating liver) subgroup protein tyrosine phosphatases, termed PfPRL. Here, we show that PfPRL is expressed in the parasite's intraerythrocytic stages, where it partially associates with endoplasmic reticulum and within a subcompartment of the food vacuole. Additionally, PfPRL targeting parallels that of apical membrane antigen-1 in developing merozoites. Recombinant PfPRL shows phosphatase activity that is preferentially inhibited by a tyrosine phosphatase inhibitor suggesting that PfPRL functions as a tyrosine phosphatase. Recombinant PfPRL can also be farnesylated in vitro. Inhibition of malarial farnesyltransferase activity can be achieved with the heptapetide RKCHFM, which corresponds to the C-terminus of PfPRL. This study provides the first evidence for expression of enzymatically active PRL-related protein tyrosine phosphatases in malarial parasites, and demonstrates the potential of peptides derived from Plasmodium prenylated proteins as malarial farnesyltransferase inhibitors.