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1.
Int J Gynecol Cancer ; 34(4): 550-558, 2024 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-38129136

RESUMEN

OBJECTIVE: In the PAOLA-1/ENGOT-ov25 trial (NCT02477644), adding maintenance olaparib to bevacizumab provided a substantial progression-free survival benefit in patients with newly diagnosed advanced ovarian cancer and homologous recombination deficiency (HRD)-positive tumors, irrespective of clinical risk. Subsequently, a clinically meaningful improvement in overall survival was reported with olaparib plus bevacizumab in the HRD-positive subgroup. We report updated progression-free survival and overall survival by clinical risk and HRD status. METHODS: Patients in clinical response after first-line platinum-based chemotherapy plus bevacizumab received maintenance olaparib (up to 24 months) plus bevacizumab (up to 15 months in total) or placebo plus bevacizumab. This post hoc analysis evaluated 5-year progression-free survival and mature overall survival in patients classified by clinical risk and HRD status. RESULTS: Of 806 randomized patients, 74% were higher-risk and 26% were lower-risk. In higher-risk HRD-positive patients, the hazard ratio (HR) for progression-free survival was 0.46 (95% confidence interval (95% CI) 0.34 to 0.61), with 5-year progression-free survival of 35% with olaparib plus bevacizumab versus 15% with bevacizumab alone; and the HR for overall survival was 0.70 (95% CI 0.50 to 1.00), with 5-year overall survival of 55% versus 42%, respectively. In lower-risk HRD-positive patients, the HR for progression-free survival was 0.26 (95% CI 0.15 to 0.45), with 5-year progression-free survival of 72% with olaparib plus bevacizumab versus 28% with bevacizumab alone; and the HR for overall survival was 0.31 (95% CI 0.14 to 0.66), with 5-year overall survival of 88% versus 61%, respectively. No benefit was seen in HRD-negative patients regardless of clinical risk. CONCLUSION: This post hoc analysis indicates that in patients with newly diagnosed advanced HRD-positive ovarian cancer, maintenance olaparib plus bevacizumab should not be limited to those considered at higher risk of disease progression. Five-year progression-free survival rates support long-term remission and suggest an increased potential for cure with particular benefit suggested in lower-risk HRD-positive patients.


Asunto(s)
Neoplasias Ováricas , Piperazinas , Femenino , Humanos , Bevacizumab , Carcinoma Epitelial de Ovario/tratamiento farmacológico , Neoplasias Ováricas/patología , Ftalazinas , Supervivencia sin Progresión
2.
JAMA Oncol ; 6(12): 1923-1930, 2020 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-33030515

RESUMEN

IMPORTANCE: To our knowledge, this is the first randomized trial in sex cord-stromal tumors, and it establishes weekly paclitaxel as standard-of-care therapy after platinum-based therapy in this setting. OBJECTIVE: To determine the efficacy of weekly paclitaxel with or without bevacizumab as treatment for relapsed sex cord-stromal tumors and evaluate whether the addition of bevacizumab to weekly paclitaxel improves 6-month progression-free rate. DESIGN, SETTING, AND PARTICIPANTS: This open-label, academic, international, randomized phase 2 trial (ALIENOR) was conducted at 28 referral centers in France, Germany, Italy, Japan, and Belgium in collaboration with the Rare Tumor committee of the Gynecologic Cancer InterGroup and used an adaptive bayesian design. It included 60 women with sex cord-stromal tumors that had relapsed after at least 1 platinum-based chemotherapy. Enrollment occurred from 2013 to 2016, and the final analysis database lock was on March 27, 2020 (median follow-up, 38.9 months). INTERVENTIONS: Participants were randomized to receive either paclitaxel (80 mg/m2, days 1, 8, and 15 every 4 weeks) alone or paclitaxel with bevacizumab (10 mg/kg, every 2 weeks) for 6 cycles followed by maintenance bevacizumab (15 mg/kg, every 3 weeks) for up to 1 year or until progression or unacceptable toxicity. Crossover to bevacizumab was permitted after progression during or following paclitaxel alone. MAIN OUTCOMES AND MEASURES: Six-month progression-free rate. RESULTS: Sixty patients (predominantly with granulosa cell tumors) were randomized, 32 to receive single-agent paclitaxel (median [interquartile range] age at inclusion, 60 [53-64] years) and 28 to receive paclitaxel-bevacizumab (median [interquartile range] age at inclusion, 55 [47-61] years; 1 did not receive treatment). The estimated 6-month progression-free rate was 71% (95% credible interval, 55%-84%) with paclitaxel alone and 72% (95% credible interval, 55%-87%) with paclitaxel-bevacizumab. The bayesian estimate for the probability that the 6-month progression-free rate distribution was higher with the combination than with paclitaxel alone was 57%, less than the predefined superiority threshold. The objective response rate increased from 25% (95% CI, 12%-43%) to 44% (95% CI, 26%-65%) with the addition of bevacizumab. One patient discontinued combination therapy within 6 months because of toxicity. CONCLUSIONS AND RELEVANCE: Weekly paclitaxel is a new option for relapsed sex cord-stromal tumors. In this international randomized clinical trial of patients with relapsed sex cord-stromal tumors unsuitable for surgery, adding bevacizumab to weekly paclitaxel does not improve clinical benefit. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01770301.


Asunto(s)
Bevacizumab , Paclitaxel , Tumores de los Cordones Sexuales y Estroma de las Gónadas , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Teorema de Bayes , Bevacizumab/efectos adversos , Bevacizumab/uso terapéutico , Supervivencia sin Enfermedad , Femenino , Humanos , Recurrencia Local de Neoplasia/tratamiento farmacológico , Recurrencia Local de Neoplasia/patología , Paclitaxel/efectos adversos , Paclitaxel/uso terapéutico , Tumores de los Cordones Sexuales y Estroma de las Gónadas/tratamiento farmacológico
3.
Cancers (Basel) ; 11(9)2019 Aug 26.
Artículo en Inglés | MEDLINE | ID: mdl-31455033

RESUMEN

CD3+ and CD8+ lymphocytes are well known prognostic markers in primary ovarian cancer. In contrast, the predictive value of the immune infiltrate concerning treatment response and the involvement of immune heterogeneity between primary and metastatic lesions are poorly understood. In this study, the immune infiltrate of 49 primary tumors and 38 corresponding lesions in the omentum (n = 23) and the peritoneum (n = 15) was immunohistochemically analyzed and correlated with clinicopathological factors and platinum-sensitivity. Immune heterogeneity was observed between paired primary and metastatic lesions for all immune cell phenotypes. The stromal immune infiltrate was higher in the omental lesions than in the primary tumors, which was reflected by CD45 (p=0.007), CD3 (p=0.005), CD8 (p=0.012), and PD-1 (programmed cell-death protein 1) (p=0.013). A higher stromal infiltrate of both CD45+ and CD3+ cells in the omental lesions was associated with the detection of lymph node metastasis (CD45, p=0.018; CD3, p=0.037). Platinum-sensitive ovarian cancers revealed a higher intratumoral CD8+ infiltrate in the peritoneal lesions compared to the primary tumors (p=0.045). In contrast, higher counts of stromal PD-1+ cells in the peritoneal lesions have been associated with reduced platinum-sensitivity (p=0.045). Immune heterogeneity was associated with platinum response and might represent a selection marker for personalized therapy.

4.
J Med Genet ; 56(9): 574-580, 2019 09.
Artículo en Inglés | MEDLINE | ID: mdl-30979843

RESUMEN

BACKGROUND: For individuals with ovarian cancer (OC), therapy options mainly depend on BRCA1/2 germline status. What is the prevalence of deleterious somatic variants, that is, does genetic tumour testing identify subgroups of individuals who also might benefit from targeted therapy? METHODS: Paired analysis of tumour-derived versus blood-derived DNA to determine the prevalence of deleterious somatic variants in OC predisposition genes (ATM, BRCA1/2, BRIP1, MSH2/6, PALB2, RAD51C/D and TP53) and the PIK3CA and PTEN genes in individuals with OC (AGO-TR1 study, NCT02222883). Results were complemented by BRCA1, PALB2 and RAD51C promoter methylation analyses and stratified by histological subtype; 473 individuals were included. RESULTS: The combined analyses revealed that deleterious germline variants in established OC predisposition genes (all: 125/473, 26.4%; BRCA1/2: 97/473, 20.5%), deleterious somatic variants in established OC predisposition genes excluding TP53 (all: 39/473, 8.2%; BRCA1/2: 30/473, 6.3%) and promoter methylation (all: 67/473, 14.2%; BRCA1: 57/473, 12.1%; RAD51C: 10/473, 2.1%; PALB2: 0/473) were mutually exclusive, with a few exceptions. The same holds true for deleterious somatic PIK3CA and/or PTEN variants (33/473, 7.0%) found to be enriched in endometrioid and clear cell OC (16/35, 45.7%); 84.3 % of the deleterious single-nucleotide/indel germline variants in established OC predisposition genes showed significantly higher variant fractions (VFs) in the tumour-derived versus blood-derived DNA, indicating a loss of the wild-type alleles. CONCLUSION: Tumour sequencing of the BRCA1, BRCA2, PIK3CA and PTEN genes along with BRCA1 and RAD51C promoter methylation analyses identified large subgroups of germline mutation-negative individuals who may be addressed in interventional studies using PARP or PI3K/AKT/mTOR inhibitors. TRIAL REGISTRATION NUMBER: NCT02222883.


Asunto(s)
Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Neoplasias Ováricas/genética , Eliminación de Secuencia , Proteína BRCA1 , Proteína BRCA2 , Biomarcadores de Tumor , Biología Computacional/métodos , Variaciones en el Número de Copia de ADN , Metilación de ADN , Femenino , Estudios de Asociación Genética/métodos , Pruebas Genéticas , Mutación de Línea Germinal , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , Neoplasias Ováricas/diagnóstico , Neoplasias Ováricas/epidemiología , Prevalencia , Regiones Promotoras Genéticas
5.
J Pathol Clin Res ; 4(2): 93-102, 2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-29665323

RESUMEN

A novel histopathological grading system based on tumour budding and cell nest size has recently been shown to outperform conventional (WHO-based) grading algorithms in several tumour entities such as lung, oral, and oesophageal squamous cell carcinoma (SCC) in terms of prognostic patient stratification. Here, we tested the prognostic value of this innovative grading approach in two completely independent cohorts of SCC of the uterine cervix. To improve morphology-based grading, we investigated tumour budding activity and cell nest size as well as several other histomorphological factors (e.g., keratinization, nuclear size, mitotic activity) in a test cohort (n = 125) and an independent validation cohort (n = 122) of cervical SCC. All parameters were correlated with clinicopathological factors and patient outcome. Small cell nest size and high tumour budding activity were strongly associated with a dismal patient prognosis (p < 0.001 for overall survival [OS], disease-specific survival, and disease-free survival; test cohort) in both cohorts of cervical SCC. A novel grading algorithm combining these two parameters proved to be a highly effective, stage-independent prognosticator in both cohorts (OS: p < 0.001, test cohort; p = 0.001, validation cohort). In the test cohort, multivariate statistical analysis of the novel grade revealed that the hazard ratio (HR) for OS was 2.3 for G2 and 5.1 for G3 tumours compared to G1 neoplasms (p = 0.010). In the validation cohort, HR for OS was 3.0 for G2 and 7.2 for G3 tumours (p = 0.012). In conclusion, our novel grading algorithm incorporating cell nest size and tumour budding allows strongly prognostic histopathological grading of cervical SCC superior to WHO-based grading. Therefore, our data can be regarded as a cross-organ validation of previous results demonstrated for oesophageal, lung, and oral SCC. We suggest this grading algorithm as an additional morphology-based parameter for the routine diagnostic assessment of this tumour entity.


Asunto(s)
Carcinoma de Células Escamosas/diagnóstico , Neoplasias del Cuello Uterino/diagnóstico , Adulto , Anciano , Anciano de 80 o más Años , Carcinoma de Células Escamosas/patología , Cuello del Útero/patología , Estudios de Cohortes , Supervivencia sin Enfermedad , Femenino , Estudios de Seguimiento , Alemania , Humanos , Metástasis Linfática , Persona de Mediana Edad , Clasificación del Tumor , Estadificación de Neoplasias , Pronóstico , Neoplasias del Cuello Uterino/patología , Adulto Joven
6.
PLoS One ; 12(10): e0186043, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-29053726

RESUMEN

BACKGROUND: Identification of families at risk for ovarian cancer offers the opportunity to consider prophylactic surgery thus reducing ovarian cancer mortality. So far, identification of potentially affected families in Germany was solely performed via family history and numbers of affected family members with breast or ovarian cancer. However, neither the prevalence of deleterious variants in BRCA1/2 in ovarian cancer in Germany nor the reliability of family history as trigger for genetic counselling has ever been evaluated. METHODS: Prospective counseling and germline testing of consecutive patients with primary diagnosis or with platinum-sensitive relapse of an invasive epithelial ovarian cancer. Testing included 25 candidate and established risk genes. Among these 25 genes, 16 genes (ATM, BRCA1, BRCA2, CDH1, CHEK2, MLH1, MSH2, MSH6, NBN, PMS2, PTEN, PALB2, RAD51C, RAD51D, STK11, TP53) were defined as established cancer risk genes. A positive family history was defined as at least one relative with breast cancer or ovarian cancer or breast cancer in personal history. RESULTS: In total, we analyzed 523 patients: 281 patients with primary diagnosis of ovarian cancer and 242 patients with relapsed disease. Median age at primary diagnosis was 58 years (range 16-93) and 406 patients (77.6%) had a high-grade serous ovarian cancer. In total, 27.9% of the patients showed at least one deleterious variant in all 25 investigated genes and 26.4% in the defined 16 risk genes. Deleterious variants were most prevalent in the BRCA1 (15.5%), BRCA2 (5.5%), RAD51C (2.5%) and PALB2 (1.1%) genes. The prevalence of deleterious variants did not differ significantly between patients at primary diagnosis and relapse. The prevalence of deleterious variants in BRCA1/2 (and in all 16 risk genes) in patients <60 years was 30.2% (33.2%) versus 10.6% (18.9%) in patients ≥60 years. Family history was positive in 43% of all patients. Patients with a positive family history had a prevalence of deleterious variants of 31.6% (36.0%) versus 11.4% (17.6%) and histologic subtype of high grade serous ovarian cancer versus other showed a prevalence of deleterious variants of 23.2% (29.1%) and 10.2% (14.8%), respectively. Testing only for BRCA1/2 would miss in our series more than 5% of the patients with a deleterious variant in established risk genes. CONCLUSIONS: 26.4% of all patients harbor at least one deleterious variant in established risk genes. The threshold of 10% mutation rate which is accepted for reimbursement by health care providers in Germany was observed in all subgroups analyzed and neither age at primary diagnosis nor histo-type or family history sufficiently enough could identify a subgroup not eligible for genetic counselling and testing. Genetic testing should therefore be offered to every patient with invasive epithelial ovarian cancer and limiting testing to BRCA1/2 seems to be not sufficient.


Asunto(s)
Genes BRCA1 , Genes BRCA2 , Predisposición Genética a la Enfermedad , Mutación de Línea Germinal , Neoplasias Ováricas/genética , Femenino , Humanos
7.
Clin Nucl Med ; 39(5): e313-4, 2014 May.
Artículo en Inglés | MEDLINE | ID: mdl-24152664

RESUMEN

Radio-guided sentinel lymph node biopsy in early-stage breast cancer is standard of care. Freehand SPECT is a system for intraoperative visualization of radioactivity in the body. It generates a 3-dimensional image of the radioactivity distribution complementing the acoustic information of the gamma probe by providing depth and radioactive uptake information. In the reported case, freehand SPECT was used in a breast cancer patient as a control method after conventional sentinel lymph node biopsy. Freehand SPECT identified an additional lymph node, changing the original stage from pN1(mic) (micrometastasis) to pN1a (nodal positive), resulting in an axillary lymph node dissection.


Asunto(s)
Neoplasias de la Mama/diagnóstico por imagen , Neoplasias de la Mama/cirugía , Cuidados Intraoperatorios , Ganglios Linfáticos/diagnóstico por imagen , Biopsia del Ganglio Linfático Centinela , Tomografía Computarizada de Emisión de Fotón Único , Femenino , Humanos
8.
Eur J Nucl Med Mol Imaging ; 40(11): 1656-61, 2013 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-23754763

RESUMEN

PURPOSE: Sentinel lymph node biopsy (SLNB) is standard of care in early-stage breast cancer. Freehand SPECT (FhSPECT) is a system generating 3-D images for intraoperative visual detection of radioactivity in the body. The aim of our study was to evaluate the sensitivity of this technology for sentinel lymph node (SLN) detection and SLNB guidance. METHODS: In 40 patients, FhSPECT was additionally used after planar imaging and probe localization for SLNB. The number of SLNs detected was compared with the number detected by planar scintigraphy (reference method) and the conventional acoustic gamma probe (standard alternative). The sensitivity of FhSPECT was compared with that of the conventional gamma probe (McNemar's test). RESULTS: FhSPECT mapped the SLNs in 92.3 % of the basins (36/39) intraoperatively in identical positions to those seen on planar scintigrams. The conventional gamma probe correctly detected the SLNs in 35 of 39 basins (89.7 %). After SLNB, remaining radioactivity was detected by FhSPECT in nine patients, resulting in additional resection of SLNs in four patients. CONCLUSION: FhSPECT is a highly sensitive modality for intraoperative detection of SLNs, resulting in the identification of a higher number of SLNs than conventional gamma probe detection.


Asunto(s)
Neoplasias de la Mama/diagnóstico , Biopsia Guiada por Imagen/métodos , Biopsia del Ganglio Linfático Centinela/métodos , Tomografía Computarizada de Emisión de Fotón Único/métodos , Adulto , Anciano , Anciano de 80 o más Años , Neoplasias de la Mama/diagnóstico por imagen , Neoplasias de la Mama/patología , Femenino , Humanos , Persona de Mediana Edad , Sensibilidad y Especificidad
9.
Breast Care (Basel) ; 7(6): 484-6, 2012 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-24715831

RESUMEN

After the development of a hand-held intraoperative device for 3D real-time imaging of radioactively labeled sentinel lymph nodes in the human body, we present our first experience with the newest version of the freehand single-photon emission computed tomography (SPECT) technology in the operating room. The freehand SPECT system combines a gamma probe and an optical infrared positioning system, and provides surgeons with 3D imaging including exact depth information of the radioactive target. This technology was used intraoperatively in a female breast cancer patient to localize the axillary sentinel lymph nodes. The data obtained with freehand SPECT correlate well with conventional lymphoscintigraphy and with data collected using a conventional hand-held probe. By offering fast real-time intraoperative imaging, the new freehand SPECT system might facilitate the detection and removal of the sentinel lymph node(s) in certain situations and can be used for documentation and quality assurance purposes.

10.
Eur J Nucl Med Mol Imaging ; 37(8): 1452-61, 2010 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-20354851

RESUMEN

PURPOSE: Freehand SPECT is a 3-D tomographic imaging modality based on data acquisition with a hand-held detector that is moved freely, in contrast to conventional, fixed gamma camera systems. In this pilot study, the feasibility of freehand SPECT for 3-D lymphatic mapping in breast cancer was evaluated. METHODS: A total of 85 patients (age: 29-88 years) with an initial diagnosis of invasive breast cancer and no clinical evidence of nodal involvement prospectively underwent sentinel lymph node (SLN) biopsy. Preoperative lymphatic mapping (35-87 MBq (99m)Tc-Nanocoll) included tomographic imaging with a SPECT/CT device (Siemens Symbia T6) serving as reference. Initially, the freehand SPECT approach was assessed in a pilot study consisting of 50 patients. The quality of each freehand SPECT acquisition was assessed and ranked as good, intermediate or poor. In another series comprising a further 35 patients (validation study), a guidance system for the acquisition was implemented based on the results of the pilot study, ensuring acquisitions with good quality. For 3-D tomographic image reconstruction, ad hoc models and iterative reconstruction algorithms were used in all 85 patients. To allow for adequate comparison, SPECT/CT data and freehand SPECT data were registered within the same coordinate system. RESULTS: In the pilot study, freehand SPECT enabled mapping of 24 of 83 SLNs in 20 of 44 patients (3 dropouts, 3 patients without SLN either in SPECT/CT or in freehand SPECT). Using SPECT/CT as reference, the accuracy of freehand SPECT was 77.8% (7/9 nodes) in scans with good quality, while for intermediate and poor quality scans, the accuracy was reduced to 34.3 and 12.8%, respectively. In the validation study, quality feedback improved the results significantly and freehand SPECT enabled the mapping of at least one SLN in 87.5% of the patients (28/32 - 3 dropouts). Compared to the reference method, freehand SPECT showed a sensitivity of 83.3% (35/42 nodes). False-negative findings were related to insufficient scanning time, insufficient coverage of the axillary region, close proximity of the SLN to the injection site and low tracer uptake in the SLNs. CONCLUSION: In this preliminary study, we could demonstrate that 3-D localization of SLNs is feasible using freehand SPECT technology. Prerequisites for acquisition of a good scan quality, most likely allowing precise SLN mapping, have been defined. This approach has high potential to allow image-guided biopsy and further standardization of SLN dissection, thus bringing 3-D nuclear imaging into the operating room.


Asunto(s)
Neoplasias de la Mama/diagnóstico por imagen , Neoplasias de la Mama/cirugía , Imagenología Tridimensional/métodos , Biopsia del Ganglio Linfático Centinela/métodos , Tomografía Computarizada de Emisión de Fotón Único/métodos , Adulto , Anciano , Anciano de 80 o más Años , Estudios de Factibilidad , Humanos , Periodo Intraoperatorio , Persona de Mediana Edad , Control de Calidad , Tomografía Computarizada por Rayos X
11.
Gene ; 341: 189-97, 2004 Oct 27.
Artículo en Inglés | MEDLINE | ID: mdl-15474301

RESUMEN

Ras-related C3 toxin substrate 1 (Rac1) is a small Rho-GTPase with important functions in fundamental cellular processes such as cytoskeleton rearrangements, signal transduction, cell cycle progression and malignant transformation. Using Rac1 primer, we identified a 5.5-kb DNA sequence on chromosome 4 (Chr. 4) in the human genome, containing the intronless protein coding sequence of Rac1. Sequence analysis revealed features of a processed pseudogene, which we named psi1Rac1, that could be detected by Southern blot and polymerase chain reaction (PCR) on genomic DNA. A psi1Rac1 pseudogene transcript was not detected by reverse transcription-polymerase chain reaction (RT-PCR), nor had the psi1Rac1 promoter any transcriptional activity. In addition, three other intronless pseudogenes of Rac1 on chromosomes 4, 13 and X were identified (psi1Rac1-psi4Rac1) sharing an 86-96% sequence similarity with Rac1. Neither RT-PCR with pseudogene specific restriction enzymes, nor the sequencing of 130 cDNA clones from benign and malignant breast tissue and cell lines, detected the transcription of any of the Rac1 pseudogenes (psi2Rac1-psi4Rac1). Existence of Rac1 pseudogenes should be taken into consideration when analyzing genomic alterations of the human Rac1 gene.


Asunto(s)
Genoma Humano , Neuropéptidos/genética , Seudogenes/genética , Proteínas de Unión al GTP rac/genética , Secuencia de Aminoácidos , Secuencia de Bases , Southern Blotting , Línea Celular , Clonación Molecular , ADN/química , ADN/genética , ADN/aislamiento & purificación , Humanos , Datos de Secuencia Molecular , Filogenia , Alineación de Secuencia , Análisis de Secuencia de ADN , Homología de Secuencia de Aminoácido , Homología de Secuencia de Ácido Nucleico , Proteína de Unión al GTP rac1
12.
Mol Cell ; 15(1): 117-27, 2004 Jul 02.
Artículo en Inglés | MEDLINE | ID: mdl-15225553

RESUMEN

Selective activation of Rac GTPase signaling pathways requires the specific release of Rac from RhoGDI complexes. We identified a RhoGDI kinase from bovine brain as p21-activated kinase (Pak). Pak1 binds and phosphorylates RhoGDI both in vitro and in vivo at Ser101 and Ser174. This resulted in dissociation of Rac1-RhoGDI, but not RhoA-RhoGDI, complexes, as determined by in vitro assays of complexation and in vivo by coimmunoprecipitation analysis. We observed that Cdc42-induced Rac1 activation is inhibited by expression of Pak1 autoinhibitory domain. The dissociation of Rac1 from RhoGDI and its subsequent activation stimulated by PDGF or EGF is also attenuated by Pak1 autoinhibitory domain, and this is dependent on the ability of RhoGDI to be phosphorylated at Ser101/174. These results support a role for Pak1-mediated RhoGDI phosphorylation as a mechanism for Cdc42-mediated Rac activation, and suggest the possibility of Rac-induced positive feed-forward regulation of Rac activity.


Asunto(s)
Inhibidores de Disociación de Guanina Nucleótido/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas de Unión al GTP rac/metabolismo , Animales , Sitios de Unión/efectos de los fármacos , Sitios de Unión/fisiología , Bovinos , Factor de Crecimiento Epidérmico/farmacología , Células HeLa , Humanos , Fosforilación/efectos de los fármacos , Factor de Crecimiento Derivado de Plaquetas/farmacología , Estructura Terciaria de Proteína/efectos de los fármacos , Estructura Terciaria de Proteína/fisiología , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiología , Proteína de Unión al GTP cdc42/metabolismo , Quinasas p21 Activadas , Proteína de Unión al GTP rac1/metabolismo , Inhibidor alfa de Disociación del Nucleótido Guanina rho , Inhibidores de la Disociación del Nucleótido Guanina rho-Específico
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