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Invasive lobular carcinoma with extracellular mucin (ILCEM) is a rare histologic subtype of breast cancer. Little is known about the pathologic or genomic signatures that distinguish ILCEM from classic invasive lobular carcinoma (ILC) or mucinous carcinoma. We studied 17 breast cancers with lobular morphology and extracellular mucin. Thirteen tumors with sufficient tissue for DNA extraction were analyzed by a next generation sequencing (NGS) assay that interrogates 447 genes for mutations and copy number variations (CNVs). Median patient age was 66 yrs (range: 31-77 yrs). Sixteen patients presented with masses, 7 of which were >2 cm. Seven patients had lymph node metastases. The cases of ILCEM were moderately (n = 13) or poorly differentiated (n = 4), frequently exhibiting variant morphology that has not been previously described or emphasized, including grade 3 nuclei (n = 11), diffuse signet ring cells (n = 10), solid growth (n = 4), tumor necrosis (n = 3) or apocrine features (n = 2). All tumors showed absent or reduced membranous E-cadherin expression. Concurrent lobular carcinoma in situ (LCIS) was seen in 11/17 cases, 1 of which was a striking example of signet ring cell LCIS with extracellular mucin. Receptor profiles were ER+/HER2- (n = 15) and ER+/HER2+ (n = 2). With a median follow-up of 83.5 months (range: 3-171 months) in 12 patients with available information, 8 patients had recurrences resulting in 4 cancer-related deaths. The most common CNVs were 16q loss (n = 11) and 1q gain (n = 9). CDH1 gene-level alterations were detected in all but one case, including frameshift (n = 7), nonsense (n = 2), and donor splice site (n = 1) mutations and indels (n = 2). Recurrent mutations were also seen in PIK3CA (n = 3), POLQ (n = 3), TP53 (n = 3), ERBB3 (n = 3), ERBB2 (n = 2), and RUNX1 (n = 2). Genes with recurrent amplifications included GATA3 (n = 4), FOXA1 (n = 3), CCND1 (n = 2). Our data highlights ILCEM as a distinct variant of ILC that often presents with higher-grade and variant morphologic features and is associated with an aggressive clinical course. NGS data support an overall lobular-type molecular profile and reveal potentially targetable alterations in a subset of cases with recurrence.
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Carcinoma de Mama in situ , Neoplasias de la Mama , Carcinoma Lobular , Adulto , Anciano , Carcinoma de Mama in situ/patología , Neoplasias de la Mama/patología , Cadherinas/genética , Carcinoma Lobular/patología , Fosfatidilinositol 3-Quinasa Clase I/genética , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , ADN , Variaciones en el Número de Copia de ADN , Femenino , Humanos , Persona de Mediana Edad , MucinasRESUMEN
PURPOSE: Safe breast cancer lumpectomies require microscopically clear margins. Real-time margin assessment options are limited, and 20-40% of lumpectomies have positive margins requiring re-excision. The LUM Imaging System previously showed excellent sensitivity and specificity for tumor detection during lumpectomy surgery. We explored its impact on surgical workflow and performance across patient and tumor types. METHODS: We performed IRB-approved, prospective, non-randomized studies in breast cancer lumpectomy procedures. The LUM Imaging System uses LUM015, a protease-activated fluorescent imaging agent that identifies residual tumor in the surgical cavity walls. Fluorescent cavity images were collected in real-time and analyzed using system software. RESULTS: Cavity and specimen images were obtained in 55 patients injected with LUM015 at 0.5 or 1.0 mg/kg and in 5 patients who did not receive LUM015. All tumor types were distinguished from normal tissue, with mean tumor:normal (T:N) signal ratios of 3.81-5.69. T:N ratios were 4.45 in non-dense and 4.00 in dense breasts (p = 0.59) and 3.52 in premenopausal and 4.59 in postmenopausal women (p = 0.19). Histopathology and tumor receptor testing were not affected by LUM015. Falsely positive readings were more likely when tumor was present < 2 mm from the adjacent specimen margin. LUM015 signal was stable in vivo at least 6.5 h post injection, and ex vivo at least 4 h post excision. CONCLUSIONS: Intraoperative use of the LUM Imaging System detected all breast cancer subtypes with robust performance independent of menopausal status and breast density. There was no significant impact on histopathology or receptor evaluation.
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Neoplasias de la Mama , Mastectomía Segmentaria , Neoplasias de la Mama/diagnóstico por imagen , Neoplasias de la Mama/cirugía , Femenino , Humanos , Neoplasia Residual , Péptido Hidrolasas , Estudios Prospectivos , ReoperaciónRESUMEN
AIMS: Perinephric fat invasion (PFI) is a key component of renal cell carcinoma (RCC) staging, but there are limited data pertaining to biopsy tract seeding (BTS) resulting in perirenal tissue involvement [BTS with perinephric fat invasion (BTS-P)].The aim is to correlate clinical outcomes with pathologic stage to determine whether the presence of BTS-P should be considered a criterion to stage RCC as part of the pT3a category in the absence of any other upstaging variables. MATERIALS AND RESULTS: We identified 304 renal biopsies from patients with subsequent nephrectomies for RCC; 33 of the tumours contained PFI. Each case was reviewed to determine the presence of BTS-P and other forms of invasion [e.g. non-BTS-P PFI, sinus fat invasion (SFI), and/or renal vein invasion (RVI)], and these findings were compared with survival outcomes. Ten (30%) of 33 tumours with PFI showed BTS-P as the only finding, and were otherwise pT1 tumours; six (60%) patients were alive without disease (AWOD) (mean, 77.5 months), three were lost to follow-up (LTF), and one died of other disease (DOOD). Two patients showed true PFI plus BTS-P; one was LTF and one is AWOD at 107 months. Ten (43%) of 23 patients with tumours with true invasion (PFI ± SFI and/or RVI) are AWOD (mean, 97.7 months), eight (35%) died of disease (DOD), four were LTF, and one DOOD. Kaplan-Meier survival curves showed that the cancer-specific survival was significantly worse in patients with true invasion (P = 0.044) than in those with BTS-P as the sole finding. CONCLUSION: Patients with tumours showing BTS-P only appear to have better outcomes than those with other non-PFI invasion, suggesting that this finding should not be upstaged to pT3a. Additional studies are needed to corroborate the significance of our observations.
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Carcinoma de Células Renales/patología , Estadificación de Neoplasias/métodos , Pronóstico , Tejido Adiposo/patología , Adulto , Anciano , Anciano de 80 o más Años , Biopsia , Femenino , Humanos , Estimación de Kaplan-Meier , Riñón/patología , Neoplasias Renales/patología , Masculino , Persona de Mediana Edad , NefrectomíaRESUMEN
The article Feasibility Study of a Novel Protease-Activated Fluorescent Imaging System for Real-Time, Intraoperative Detection of Residual Breast Cancer in Breast Conserving Surgery, written by Barbara L. Smith et al., was originally published electronically on the publisher's internet portal on January 2, 2020, without open access.
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BACKGROUND: Obtaining tumor-free margins is critical to prevent recurrence after lumpectomy for breast cancer. Unfortunately, current approaches leave positive margins that require second surgeries in 20-40% of patients. We assessed the LUM Imaging System for real-time, intraoperative detection of residual tumor. METHODS: Breast lumpectomy cavity walls and excised specimens were assessed with the LUM Imaging System after 1 mg/kg intravenous LUM015, a protease-activatable fluorescent agent. Fluorescence at potential sites of residual tumor in lumpectomy cavity walls was evaluated intraoperatively with a sterile hand-held probe, with real-time predictive results displayed on a monitor intraoperatively, and later correlated with histopathology. RESULTS: In vivo lumpectomy cavities and excised specimens were imaged after LUM015 injection in 45 women undergoing breast cancer surgery. Invasive ductal and lobular cancers and intraductal cancer (DCIS) were included. A total of 570 cavity margin surfaces in 40 patients were used for algorithm development. Image analysis and display took approximately 1 s per 2.6-cm-diameter circular margin surface. All breast cancer subtypes could be distinguished from adjacent normal tissue. For all imaged cavity surfaces, sensitivity for tumor detection was 84%. Among 8 patients with positive margins after standard surgery, sensitivity for residual tumor detection was 100%; 2 of 8 were spared second surgeries because additional tissue was excised at sites of LUM015 signal. Specificity was 73%, with some benign tissues showing elevated fluorescent signal. CONCLUSIONS: The LUM015 agent and LUM Imaging System allow rapid identification of residual tumor in the lumpectomy cavity of breast cancer patients and may reduce rates of positive margins.
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Neoplasias de la Mama/cirugía , Cuidados Intraoperatorios , Mastectomía Segmentaria/métodos , Recurrencia Local de Neoplasia/diagnóstico , Neoplasia Residual/diagnóstico , Péptido Hidrolasas/metabolismo , Adulto , Anciano , Neoplasias de la Mama/patología , Carcinoma Ductal de Mama/patología , Carcinoma Ductal de Mama/cirugía , Carcinoma Lobular/patología , Carcinoma Lobular/cirugía , Diagnóstico por Imagen , Estudios de Factibilidad , Femenino , Colorantes Fluorescentes/química , Estudios de Seguimiento , Humanos , Persona de Mediana Edad , Invasividad Neoplásica , Recurrencia Local de Neoplasia/cirugía , Neoplasia Residual/cirugía , Pronóstico , Estudios RetrospectivosRESUMEN
PURPOSE: Obtaining tumor-free surgical margins is critical to prevent recurrence in breast-conserving surgery but it remains challenging. We assessed the LUM Imaging System for real-time, intraoperative detection of residual tumor. METHODS: Lumpectomy cavity walls and excised specimens of breast cancer lumpectomy patients were assessed with the LUM Imaging System (Lumicell, Inc., Wellesley MA) with and without intravenous LUM015, a cathepsin-activatable fluorescent agent. Fluorescence at potential sites of residual tumor was evaluated with a sterile hand-held probe, displayed on a monitor and correlated with histopathology. RESULTS: Background autofluorescence was assessed in excised specimens from 9 patients who did not receive LUM015. In vivo lumpectomy cavities and excised specimens were then imaged in 15 women undergoing breast cancer surgery who received no LUM015, 0.5, or 1 mg/kg LUM015 (5 women per dose). Among these, 11 patients had invasive carcinoma with ductal carcinoma in situ (DCIS) and 4 had only DCIS. Image acquisition took 1 s for each 2.6-cm-diameter surface. No significant background normal breast fluorescence was identified. Elevated fluorescent signal was seen from invasive cancers and DCIS. Mean tumor-to-normal signal ratios were 4.70 ± 1.23 at 0.5 mg/kg and 4.22 ± 0.9 at 1.0 mg/kg (p = 0.54). Tumor was distinguished from normal tissue in pre-and postmenopausal women and readings were not affected by breast density. Some benign tissues produced fluorescent signal with LUM015. CONCLUSION: The LUM Imaging System allows rapid identification of residual tumor in the lumpectomy cavity of breast cancer patients and may reduce rates of positive margins.
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Neoplasias de la Mama/diagnóstico , Neoplasias de la Mama/cirugía , Catepsinas , Mastectomía Segmentaria , Neoplasia Residual/diagnóstico por imagen , Neoplasia Residual/patología , Imagen Óptica , Adulto , Anciano , Biopsia , Neoplasias de la Mama/metabolismo , Femenino , Humanos , Inmunohistoquímica , Periodo Intraoperatorio , Mastectomía Segmentaria/métodos , Persona de Mediana Edad , Neoplasia Residual/metabolismo , Imagen Óptica/métodos , Cirugía Asistida por ComputadorRESUMEN
A large percentage of breast cancer patients treated with breast conserving surgery need to undergo multiple surgeries due to positive margins found during post-operative margin assessment. Carcinomas could be removed completely during the initial surgery and additional surgery avoided if positive margins can be determined intraoperatively. Spectrally encoded confocal microscopy (SECM) is a high-speed reflectance confocal microscopy technology that has a potential to rapidly image the entire surgical margin at subcellular resolution and accurately determine margin status intraoperatively. In this study, in order to test the feasibility of using SECM for intraoperative margin assessment, we have evaluated the diagnostic accuracy of SECM for detecting various types of breast cancers. Forty-six surgically removed breast specimens were imaged with an SECM system. Side-by-side comparison between SECM and histologic images showed that SECM images can visualize key histomorphologic patterns of normal/benign and malignant breast tissues. Small (500 µm × 500 µm) spatially registered SECM and histologic images (n=124 for each) were diagnosed independently by three pathologists with expertise in breast pathology. Diagnostic accuracy of SECM for determining malignant tissues was high, average sensitivity of 0.91, specificity of 0.93, positive predictive value of 0.95, and negative predictive value of 0.87. Intra-observer agreement and inter-observer agreement for SECM were also high, 0.87 and 0.84, respectively. Results from this study suggest that SECM may be developed into an intraoperative margin assessment tool for guiding breast cancer excisions.
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Neoplasias de la Mama/diagnóstico , Neoplasias de la Mama/cirugía , Mastectomía Segmentaria/métodos , Microscopía Confocal/métodos , Estudios de Factibilidad , Femenino , Humanos , Variaciones Dependientes del Observador , Pronóstico , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
BACKGROUND: Intrahepatic cholangiocarcinoma (ICC) often is a diagnosis determined by exclusion. Distinguishing ICC from other metastatic adenocarcinomas based on histopathologic or immunohistochemical analysis often is difficult and requires an extensive workup. This study aimed to determine whether albumin, whose expression is restricted to the liver, has potential as a biomarker for ICC using a novel and highly sensitive RNA in situ hybridization (ISH) platform. METHODS: Modified branched DNA probes were developed for albumin RNA ISH. The study evaluated 467 patient samples of primary and metastatic lesions. RESULTS: Of the 467 samples evaluated, 83 were ICCs, 42 were hepatocellular carcinomas (HCCs), and 332 were nonhepatic carcinomas including tumors arising from the perihilar region and bile duct, pancreas, stomach, esophagus, colon, breast, ovary, endometrium, kidney, and urinary bladder. Albumin RNA ISH was highly sensitive for cancers of liver origin, staining positive in 82 (99 %) of 83 ICCs and in 42 HCCs (100 %). Perihilar and distal bile duct carcinomas as well as carcinomas arising at other sites tested negative for albumin. Notably, 6 (22 %) of 27 intrahepatic tumors previously diagnosed as carcinomas of undetermined origin tested positive for albumin. CONCLUSIONS: Albumin RNA ISH is a sensitive and highly specific diagnostic tool for distinguishing ICC from metastatic adenocarcinoma to the liver or carcinoma of unknown origin. Albumin RNA ISH could replace the extensive diagnostic workup, leading to timely confirmation of the ICC diagnosis. Additionally, the assay could serve as a guide to distinguish ICC from perihilar adenocarcinoma.
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Albúminas/genética , Neoplasias de los Conductos Biliares/diagnóstico , Carcinoma Hepatocelular/diagnóstico , Colangiocarcinoma/diagnóstico , ADN/genética , Hibridación in Situ/métodos , Neoplasias Hepáticas/diagnóstico , Adenocarcinoma/diagnóstico , Adenocarcinoma/genética , Anciano , Neoplasias de los Conductos Biliares/genética , Carcinoma Hepatocelular/genética , Colangiocarcinoma/genética , Femenino , Estudios de Seguimiento , Humanos , Neoplasias Hepáticas/genética , Masculino , Clasificación del Tumor , Pronóstico , ARN Mensajero/genéticaRESUMEN
Melanosis, the aberrant deposition of melanin pigment in the absence of melanocytes, is very rare in the genitourinary tract. We report a case of a 74-year-old male with symptomatic benign prostatic hyperplasia. Diagnostic cystourethroscopy demonstrated bladder mucosa remarkable for numerous flat, velvety, and brown-black lesions. The patient underwent cystolitholapaxy, transurethral resection of the prostate, and bladder biopsy. Microscopic examination of the bladder biopsy demonstrated urothelium with granular, black pigmentation within the mucosa and histiocytes in the lamina propria; a Fontana Masson stain was positive for melanin. Microscopic examination of the transurethral resection of the prostate demonstrated nodular hyperplasia with focal, black pigmentation of the stroma. The rarity of bladder and prostate melanosis highlights the need for further investigation to elucidate its clinical significance and provide assurance of its benignity. Despite its rarity, melanosis should be kept in the differential diagnosis when melanotic lesions are encountered during cystoscopy.
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OBJECTIVE: To determine whether discontinuation of delta-9-tetrahydrocannabinol (THC) use mitigates THC-associated changes in male reproductive health using a rhesus macaque model of daily THC edible consumption. DESIGN: Research animal study. SETTING: Research institute environment. PATIENT(S): Adult male rhesus macaques (age, 8-10 years; n = 6). INTERVENTION(S): Chronic daily THC edible administration at medically and recreationally relevant contemporary doses followed by cessation of THC use. MAIN OUTCOME MEASURE(S): Testicular volume, serum male hormones, semen parameters, sperm deoxyribonucleic acid (DNA) fragmentation, seminal fluid proteomics, and whole genome bisulfite sequencing of sperm DNA. RESULT(S): Chronic THC use resulted in significant testicular atrophy, increased gonadotropin levels, decreased serum sex steroid levels, changes in seminal fluid proteome, and increased DNA fragmentation with partial recovery after discontinuation of THC use. For every increase of 1 mg/7 kg/day in THC dosing, there was a significant decrease in the total testicular volume bilaterally by 12.6 cm3 (95% confidence interval [CI], 10.6-14.5), resulting in a 59% decrease in volume. With THC abstinence, the total testicular volume increased to 73% of its original volume. Similarly, with THC exposure, there were significant decreases in the mean total testosterone and estradiol levels and a significant increase in the follicle-stimulating hormone level. With increasing THC dose, there was a significant decrease in the liquid semen ejaculate volume and weight of coagulum; however, no other significant changes in the other semen parameters were noted. After discontinuing THC use, there was a significant increase in the total serum testosterone level by 1.3 ng/mL (95% CI, 0.1-2.4) and estradiol level by 2.9 pg/mL (95% CI, 0.4-5.4), and the follicle-stimulating hormone level significantly decreased by 0.06 ng/mL (95% CI, 0.01-0.11). Seminal fluid proteome analysis revealed differential expression of proteins enriched for processes related to cellular secretion, immune response, and fibrinolysis. Whole genome bisulfite sequencing identified 23,558 CpGs differentially methylated in heavy-THC vs. pre-THC sperm, with partial restoration of methylation after discontinuation of THC use. Genes associated with altered differentially methylated regions were enriched for those involved in the development and function of the nervous system. CONCLUSION(S): This is the first study demonstrating that discontinuation of chronic THC use in rhesus macaques partially restores adverse impacts to male reproductive health, THC-associated sperm differentially methylated regions in genes important for development, and expression of proteins important for male fertility.
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Dronabinol , Semen , Animales , Masculino , Macaca mulatta , Epigenoma , Proteoma , Espermatozoides/fisiología , Testosterona , Hormona Folículo Estimulante , Fertilidad , Estradiol , ADN , Recuento de EspermatozoidesRESUMEN
CONTEXT.: The 8th edition of the American Joint Committee on Cancer (AJCC) staging manual changed the tumor, node, metastasis (TNM) classification systems of genitourinary malignancies in 2017. However, some of the changes appear not well appreciated or recognized by practicing pathologists. OBJECTIVE.: To review the major changes compared with the 7th edition in cancers of the prostate, penis, testis, bladder, urethra, renal pelvis/ureter, and kidney and discuss the challenges that pathologists may encounter. DATA SOURCES.: Peer-reviewed publications and the 8th and 7th editions of the AJCC Cancer Staging Manual. CONCLUSIONS.: This article summarizes the updated staging of genitourinary malignancies, specifically highlighting changes from the 7th edition that are relevant to the pathologic staging system. Pathologists should be aware of the updates made in hopes of providing clarification and the remaining diagnostic challenges associated with these changes.
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Neoplasias Renales/patología , Estadificación de Neoplasias/métodos , Neoplasias de la Próstata/patología , Neoplasias Uretrales/patología , Neoplasias de la Vejiga Urinaria/patología , Neoplasias Urogenitales/patología , Femenino , Humanos , Neoplasias Renales/diagnóstico , Metástasis Linfática , Masculino , Neoplasias de la Próstata/diagnóstico , Neoplasias Uretrales/diagnóstico , Neoplasias de la Vejiga Urinaria/diagnóstico , Neoplasias Urogenitales/diagnósticoRESUMEN
CONTEXT.: Tumor histology offers a composite view of the genetic, epigenetic, proteomic, and microenvironmental determinants of tumor biology. As a marker of tumor histology, histologic grading has persisted as a highly relevant factor in risk stratification and management of urologic neoplasms (ie, renal cell carcinoma, prostatic adenocarcinoma, and urothelial carcinoma). Ongoing research and consensus meetings have attempted to improve the accuracy, consistency, and biologic relevance of histologic grading, as well as provide guidance for many challenging scenarios. OBJECTIVE.: To review the most recent updates to the grading system of urologic neoplasms, including those in the 2016 4th edition of the World Health Organization (WHO) Bluebook, with emphasis on issues encountered in routine practice. DATA SOURCES.: Peer-reviewed publications and the 4th edition of the WHO Bluebook on the pathology and genetics of the urinary system and male genital organs. CONCLUSIONS.: This article summarizes the recently updated grading schemes for renal cell carcinoma, prostate adenocarcinomas, and bladder neoplasms of the genitourinary tract.
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Adenocarcinoma/patología , Carcinoma de Células Renales/patología , Neoplasias Renales/patología , Clasificación del Tumor/métodos , Neoplasias de la Próstata/patología , Neoplasias de la Vejiga Urinaria/patología , Humanos , Masculino , Reproducibilidad de los Resultados , Neoplasias Urológicas/clasificación , Neoplasias Urológicas/patologíaRESUMEN
Tumor associated monocytes/macrophages (MO/MA) are known contributors to the immune-inflammatory cell environment of advanced epithelial ovarian carcinoma (EOC). The secreted proteome of ascitic MO/MA was examined as an aid to the discovery of novel proteins in EOC that are likely to have biological relevance in the inflammatory pathways of EOC. Ascitic fluid MO/MA were isolated from EOC patients, grown short-term in serum-free media. MO/MA supernatants were analyzed for secreted proteins by HPLC fractionation followed by LC-tandem mass spectrometric analysis. The 14-3-3 zeta adaptor protein was identified in supernatants of three of three EOC patients but not in supernatants of buffy coat monocytes isolated from normal donors or the established monocyte cell line THP1. Moreover, 14-3-3 zeta was identified in ascitic fluids in eight of eight chemotherapy-naïve patients by both immunoblot and mass spectrometric analysis. Immunofluorescent staining for 14-3-3 zeta demonstrated expression of the protein on ascitic and peritumoral macrophages in EOC patients. 14-3-3 zeta was also expressed on endothelial cells in the peritumoral stroma and partially on tumor cells. Uptake of 14-3-3 zeta was observed in EOC cell lines co-cultured with the recombinant protein expressed in E. coli. It is demonstrated for the first time that the important adaptor protein 14-3-3 zeta is common to the secretome of ascitic MO/MA and the ascites of advanced EOC patients.
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Proteínas 14-3-3/metabolismo , Ascitis/metabolismo , Macrófagos/metabolismo , Monocitos/metabolismo , Neoplasias Glandulares y Epiteliales/metabolismo , Neoplasias Ováricas/metabolismo , Proteínas 14-3-3/química , Proteínas 14-3-3/genética , Secuencia de Aminoácidos , Anticuerpos Monoclonales/inmunología , Ascitis/inmunología , Línea Celular Tumoral , Femenino , Técnica del Anticuerpo Fluorescente , Humanos , Immunoblotting , Macrófagos/inmunología , Espectrometría de Masas , Datos de Secuencia Molecular , Monocitos/inmunología , Neoplasias Glandulares y Epiteliales/inmunología , Neoplasias Ováricas/inmunología , Proteoma , Alineación de SecuenciaRESUMEN
Sec9p and Spo20p are two SNAP25 family SNARE proteins specialized for different developmental stages in yeast. Sec9p interacts with Sso1/2p and Snc1/2p to mediate intracellular trafficking between post-Golgi vesicles and the plasma membrane during vegetative growth. Spo20p replaces Sec9p in the generation of prospore membranes during sporulation. The function of Spo20p requires enzymatically active Spo14p, which is a phosphatidylcholine (PC)-specific phospholipase D that hydrolyzes PC to generate phosphatidic acid (PA). Phosphatidic acid is required to localize Spo20p properly during sporulation; however, it seems to have additional roles that are not fully understood. Here we compared the fusion mediated by all combinations of the Sec9p or Spo20p C-terminal domains with Sso1p/Sso2p and Snc1p/Snc2p. Our results show that Spo20p forms a less efficient SNARE complex than Sec9p. The combination of Sso2p/Spo20c is the least fusogenic t-SNARE complex. Incorporation of PA in the lipid bilayer stimulates SNARE-mediated membrane fusion by all t-SNARE complexes, likely by decreasing the energetic barrier during membrane merger. This effect may allow the weak SNARE complex containing Spo20p to function during sporulation. In addition, PA can directly interact with the juxtamembrane region of Sso1p, which contributes to the stimulatory effects of PA on membrane fusion. Our results suggest that the fusion strength of SNAREs, the composition of organelle lipids and lipid-SNARE interactions may be coordinately regulated to control the rate and specificity of membrane fusion.