Concordancia entre las ecuaciones de estimación del filtrado glomerular y el aclaramiento de creatinina en orina de 4horas en pacientes críticos con trauma grave / Concordance between glomerular filtration rate estimation equations and 4-hour urinary creatinine clearance in critically ill patients with severe trauma

Antecedentes y objetivo: Cada vez hay más estudios que evidencian que las ecuaciones utilizadas para conocer la tasa de filtrado glomerular estimada (TFGe) no son adecuadas para los pacientes críticos en los que se producen continuas variaciones del filtrado glomerular (FG). El método más práctico para aproximarse al estudio del FG es el cálculo del aclaramiento de creatinina (ClCr) en periodos de recogida de orina variables. El objetivo del estudio fue observar el comportamiento de las ecuaciones empleadas para estimar el filtrado glomerular cuando se aplican a la subpoblación de pacientes críticos ingresados por trauma grave y comparar el ClCr en orina recogida en un periodo de 4horas (ClCr-4h). Material y métodos: Estudio observacional que incluye pacientes ingresados por trauma grave. Se calculó el ClCr-4h y se determinó la TFGe mediante las ecuaciones de Cockcroft-Gault, Jelliffe modificada, MDRD, t-MDRD y CKD-EPI. Los resultados se expresan referidos a superficie corporal (ml/min/1,73m2). Los análisis se realizaron con el software estadístico R versión 4.0.4. Resultados: Se incluyeron 85 pacientes. La edad mediana de los pacientes fue de 51años; 68 pacientes fueron varones (78,82%). El ClCr-4h ajustado a superficie corporal (ClCr-4h ml/min/1,73m2) medio fue de 84,5ml/min/1,73m2. Hallamos correlación estadísticamente significativa de ClCr-4h/1,73m2 con la TFGe por t-MDRD. Para ClCr-4h/1,73m2 mayores de 130ml/min/m2 la ecuación de Cockcroft-Gault identifica a los pacientes correctamente de una forma estadísticamente significativa. Conclusiones: El cálculo de ClCr en el entorno de UCI proporciona datos fiables del FG, no siendo adecuado el uso de ecuaciones estimativas.(AU)

Background and objective: There is a growing body of evidence that the equations used to estimate the glomerular filtration rate (GFR) are not suitable in critically ill patients, a population whose GFR fluctuates continuously. Glomerular filtration is usually estimated by measuring urine creatinine clearance (CrCl) at various time points. The aim of our study was to evaluate the performance of the most widely used GFR calculators in the subpopulation of critically ill patients admitted for severe trauma, and to compare the results against determinations of CrCl in urine collected over a 4-hour period (4h-CrCl). Material and methods: Observational study in patients hospitalized for severe trauma. We measured the 4h-CrCl and estimated GFR using the Cockcroft-Gault, modified Jelliffe, MDRD, t-MDRD, and CKD-EPI equations, adjusting the results for body surface area (BSA) (ml/min/1.73m2). Data were analysed using R version 4.0.4. Results: A total of 85 patients were included. Median age was 51years, and 68 were men (78.82%). The mean BSA-adjusted 4h-CrCl (4h-ClCr/1.73m2) was 84.5ml/min/1.73m2. We found that GFR estimated using the t-MDRD equation correlated significantly with 4h-CrCl/1.73m2. The Cockcroft-Gault equation correlated significantly with 4h-CrCl/1.73m2 when GFR was greater than 130ml/min/m2. Conclusions: In ICU patients, glomerular filtration can be reliably estimated by determining urine CrCl, but GFR calculators are not accurate in this population.(AU)

Concordance between glomerular filtration rate estimation equations and 4-hour urinary creatinine clearance in critically ill patients with severe trauma.

BACKGROUND AND OBJECTIVE: There is a growing body of evidence that the equations used to estimate the glomerular filtration rate (GFR) are not suitable in critically ill patients, a population whose GFR fluctuates continuously. Glomerular filtration is usually estimated by measuring urine creatinine clearance (CrCl) at various time points. The aim of our study was to evaluate the performance of the most widely used GFR calculators in the subpopulation of critically ill patients admitted for severe trauma, and to compare the results against determinations of CrCl in urine collected over a 4-h period (4h-CrCl). MATERIAL AND METHODS: Observational study in patients hospitalized for severe trauma. We measured the 4h-CrCl and estimated GFR using the Cockcroft-Gault, modified Jelliffe, MDRD, t-MDRD, and CKD-EPI equations, adjusting the results for body surface area (BSA) (ml/min/1.73m2). Data were analysed using R version 4.0.4. RESULTS: A total of 85 patients were included. Median age was 51 years, and 68 were men (78.82%). The mean BSA-adjusted 4h-CrCl (4h-ClCr/1.73m2) was 84.5 ml/min/1.73m2. We found that GFR estimated using the t-MDRD equation correlated significantly with 4h-CrCl/1.73m2. The Cockcroft-Gault equation correlated significantly with 4h-CrCl/1.73m2 when GFR was greater than 130ml/min/m2. CONCLUSIONS: In ICU patients, glomerular filtration can be reliably estimated by determining urine CrCl, but GFR calculators are not accurate in this population.

Actinomyces and MRONJ: A retrospective study and a literature review.

The AAOMS in 2014 changed from BRONJ to the term Medication-Related Osteonecrosis of the Jaw (MRONJ), because of the growing number of osteonecrosis cases associated with other antiresorptive and antiangiogenic therapies. Even if the drugs involved are different, the histopathological findings are the same. Colonies of Actinomyces are encountered in most cases. The aim of the present study is to report on Actinomyces prevalence among the cases of MRONJ, taking into consideration also antiresorptive and antiangiogenic therapies in the literature and in our sample between 2005 and 2020. The review was performed using the database Medline the linkage between Actinomyces infection and MRONJ. The retrospective study was conducted on patients between with clinical and radiological manifestations of MRONJ May 2005 and February 2020. A total of 42 articles were found, 30 publications have been taken into consideration for the review. A total of 114 patients have been examined at the Padua Hospital. A total of 101 oncological patients presented the histological confirmation of MRONJ. 83 specimens revealed the presence of Actinomyces infection (82.18%). Actinomyces-associated lesions are frequent and present a wide spectrum of clinical manifestation.

Analysis of Kidney Donation and Its Relationship With Graft Failure of the Recipient at 1 Year.

INTRODUCTION: Currently, the shortage of organs available for kidney transplantation and a change in donors' and recipients' profiles (elderly, with cardiovascular risk, donors after cardiac death), it is becoming necessary to assess grafts from expanded-criteria donors (ECD) in order to have methods that allow us to predict viability and graft survival. OBJECTIVE: The aim of this study was to analyze the different methods of renal donor assessment (estimated glomerular filtration rate [eGFR], preimplantation biopsy, and Kidney Donor Profile Index [KDPI] score) as predictors of graft survival and renal function of our recipient at 1 year. METHODS: We performed a descriptive and retrospective study of 183 deceased donor kidney transplantations performed at our center between 2011 and 2015. We calculated the KDPI scores, donor eGFR was estimated using the Chronic Kidney Disease Epidemiology Collaboration Formula equation, and biopsies were evaluated using Banff classification. RESULTS: ECDs comprised 59.60%, 93% of donors had an eGFR ≥ 60 mL/min/1.73 m2, and 41% presented with a KDPI score ≥ 90%. The most frequent range in the biopsy score was 0-3. The 1-year graft survival rate was 86.90%. Factors that negatively influenced graft survival were donor/recipient age, ECD, KDPI, and cold ischemia time (CIT). CONCLUSION: Prolonged CIT and KDPI ≥ 90% were donor variables that were related to graft failure at 1 year in our center.

Efficacy of dialysis in peritoneal dialysis: utility of bioimpedance to calculate Kt/V and the search for a target Kt.

BACKGROUND: To calculate Kt/V, volume (V) is usually obtained by Watson formula, but bioimpedance spectroscopy (BIS) is a simple and applicable technique to determinate V, along with other hydration and nutrition parameters, in peritoneal dialysis (PD) patients. Dialysis efficacy can also be measured with Kt, but no experience exists in PD, so there is no reference/target value for Kt that must be achieved in these patients to be considered adequately dialyzed. We evaluated the efficacy of PD with Kt/V using Watson formula and BIS for V calculation, assessed hydration status in a PD unit by data obtained by BIS, and attempted to find a reference Kt from the Kt/V previously obtained by BIS. METHODS: In this observational prospective study of 78 PD patients, we measured V using BIS (V bis) and Watson formula (V w) and calculated weekly Kt/V using both volumes (Kt/V bis/V bis and Kt/V w). With the BIS technique, we obtained and subsequently analyzed other hydration status parameters. We achieved a reference Kt, extrapolating the value desired (weekly Kt/V 1.7) to the target Kt using the simple linear regression statistical technique, basing it on the results of the previously calculated Pearson's linear correlation coefficient. RESULTS: Volume was 1.8 l higher by Watson formula than with BIS (p < 0.001). Weekly Kt/V bis was 2.33 ± 0.68, and mean weekly Kt/V w was 2.20 ± 0.63 (p < 0.0001); 60.25 % of patients presented overhydration according to the BIS study (OH >1.1 l). The target value of Kt for the reference weekly Kt/V bis (1.7) was 64.87 l. CONCLUSIONS: BIS is a simple, applicable technique for calculating V in dialysis that can be especially useful in PD patients compared with the anthropometric formulas, by the abnormally distributed body water in these patients. Other parameters obtained by BIS will serve to assess both the distribution of body volume and nutritional status in the clinical setting. The target Kt value obtained from Kt/V bis allowed us to measure the efficacy of PD in a practical way, omitting V measurement.

Chromatin and DNA methylation dynamics during retinoic acid-induced RET gene transcriptional activation in neuroblastoma cells.

Although it is well known that RET gene is strongly activated by retinoic acid (RA) in neuroblastoma cells, the mechanisms underlying such activation are still poorly understood. Here we show that a complex series of molecular events, that include modifications of both chromatin and DNA methylation state, accompany RA-mediated RET activation. Our results indicate that the primary epigenetic determinants of RA-induced RET activation differ between enhancer and promoter regions. At promoter region, the main mark of RET activation was the increase of H3K4me3 levels while no significant changes of the methylation state of H3K27 and H3K9 were observed. At RET enhancer region a bipartite chromatin domain was detected in unstimulated cells and a prompt demethylation of H3K27me3 marked RET gene activation upon RA exposure. Moreover, ChIP experiments demonstrated that EZH2 and MeCP2 repressor complexes were associated to the heavily methylated enhancer region in the absence of RA while both complexes were displaced during RA stimulation. Finally, our data show that a demethylation of a specific CpG site at the enhancer region could favor the displacement of MeCP2 from the heavily methylated RET enhancer region providing a novel potential mechanism for transcriptional regulation of methylated RA-regulated loci.

CCDC6 represses CREB1 activity by recruiting histone deacetylase 1 and protein phosphatase 1.

RET/papillary thyroid carcinoma 1 (PTC1) oncogene is frequently activated in human PTCs. It is characterized by the fusion of the intracellular kinase-encoding domain of RET to the first 101 amino acids of CCDC6. The aim of our work is to characterize the function of the CCDC6 protein to better understand the function of its truncation, that results in the loss of the expression of one allele, in the process of thyroid carcinogenesis. Here, we report that CCDC6 interacts with CREB1 and represses its transcriptional activity by recruiting histone deacetylase 1 and protein phosphatase 1 proteins at the CRE site of the CREB1 target genes. Finally, we show an increased CREB1 phosphorylation and activity in PTCs carrying the RET/PTC1 oncogene. Consistently, an increased expression of two known CREB1 target genes, AREG and cyclin A, was observed in this subgroup of thyroid papillary carcinomas. Therefore, the repression of CREB1 activity by CCDC6 has a critical function in the development of human thyroid papillary carcinomas carrying RET/PTC1 activation.

[Short cold ischaemia time optimises transplant results for kidneys from expanded criteria donors]. / El tiempo de isquemia fría corto optimiza los resultados de los trasplantes renales efectuados con donantes con criterios expandidos.

INTRODUCTION: Outcome of renal transplant from expanded criteria donors (ECD) is usually inferior than those from standard criteria donors (SCD) and may be improved decreasing cold ischemia time (CIT) and minimizing preservation injury. We compare the results obtained with CIT <15 hours in kidney transplants from ECD vs SCD. SUBJECTS AND METHODS: Prospective, single center study of kidney transplants performed since June 2003 to December 2007. Minimum follow-up period was 12 months. Data of donors, receptors and transplant outcome from ECD and SCD are compared. RESULTS: CIT (mean +/- SD) was 9.3+/-2.5 hours in transplants from ECD (n=24) and 8.3+/-3.3 hours in those from SCD (N=50), p=0.18. We did not find significant differences among recipients of grafts from ECD and those from SCD regarding: primary non-function (4.2% vs 2%, respectively), delayed graft function (16.7% vs 10%), surgical complications (25% vs 16%) or acute rejection episodes (8.3% vs 2%). Glomerular filtration rate at one year follow-up was 65.8+/-14.9 ml/min in ECD recipients and 49.4+/-12.5 ml/min (p<0.0001). One year graft survival was 95.8% in ECD recipients and 94% in SCD recipients (p=0.75). CONCLUSIONS: Short CIT in kidney transplant from ECD leads to similar outcome than that obtained from SCD, although renal function is inferior in ECD grafts.

El tiempo de isquemia fría corto optimiza los resultados de los trasplantes renales efectuados con donantes con criterios expandidos / No disponible

Introducción: Los resultados de los trasplantes efectuados condonantes con criterios expandidos (DCE) son inferiores a los obtenidos con donantes con criterios estándar (DCS). Para optimizar su evolución, se podría reducir su tiempo de isquemiafría (TIF) reduciendo su daño de preservación. Comparamoslos resultados obtenidos al aplicar TIF <15 horas tanto a DCE como a DCS. Material y métodos: Realizamos un estudio unicéntrico, de cohortes, prospectivo, de casos incidentes de trasplante renal de cadáver entre junio de 2003 y diciembre de2007. El tiempo mínimo de seguimiento fue de 12 meses. Comparamos los datos de los donantes, de los receptores y de la evolución de los trasplantes efectuados con DCE frente a los de los DCS. Resultados: El TIF para los DCE (N = 24) y para los DCS (N = 50) fue, respectivamente, de 9,3 ± 2,5 y 8,3± 3,3 horas (p = 0,18). No encontramos diferencias significativas entre los receptores de DCE y DCS en cuanto a: no función primaria del injerto 4,2 vs. 4%, retardo en la función del injerto 16,7 vs. 10%, complicaciones quirúrgicas 25 vs. 16% y rechazos agudos 8,3 vs. 2%. El filtrado glomerular estimado al año para los DCS fue de 65,8 ± 14,9 ml/min y para los DCE de 49,4 ± 12,5 ml/min (p <0,0001). La supervivencia renal al año fue del 95,8% para los receptores de DCE y del 94% para los DCS (p = 0,75). Conclusiones: La aplicación de TIF cortos a los DCE permite conseguir una evolución similar a la de los DCS, aunque su función renal sea en todo momento inferior (AU)

Introduction: Outcome of renal transplant from expanded criteria donors (ECD) is usually inferior than those from standard criteria donors (SCD) and may be improved decreasing cold ischemia time (CIT) and minimizing preservation injury. We compare the results obtained with CIT <15 hours in kidney transplants from ECD vs. SCD. Subjects and Methods: Prospective, single center study of kidney transplants performed since June 2003 to December 2007. Minimum follow-up period was 12months. Data of donors, receptors and transplant outcome from ECD and SCD are compared. Results: CIT (mean ± SD)was 9.3 ± 2.5 hours in transplants from ECD (n = 24) and8.3 ± 3.3 hours in those from SCD (N = 50), p = 0.18. We did not find significant differences among recipients of grafts from ECD and those from SCD regarding: primary non-function (4.2% vs. 2%, respectively), delayed graft function (16.7% vs. 10%), surgical complications (25% vs.16%) or acute rejection episodes (8.3% vs. 2%).Glomerular filtration rate at one year follow-up was 65.8± 14.9 ml/min in ECD recipients and 49.4 ± 12.5 ml/min (p<0.0001). One year graft survival was 95.8% in ECD recipients and 94% in SCD recipients (p = 0.75).Conclusions: Short CIT in kidney transplant from ECD leads to similar outcome than that obtained from SCD, although renal function is inferior in ECD grafts (AU)

Conversion to tacrolimus extended-release formulation: short-term clinical results.

OBJECTIVE: To determine the short-term clinical results of conversion of treatment from tacrolimus twice daily (BID TAC) to the extended-release formulation (OD TAC), milligram for milligram, and whether such conversion is safe in stable kidney transplant recipients. PATIENTS AND METHODS: The study included 38 kidney transplant recipients (median [SD] age, 54.3 [14.4] years) with stable renal function (mean [SD] serum creatinine concentration 1.29 [0.38] mg/dL). Posttransplantation follow-up was 3.4 (3.1) years (range, 4-168 months). All patients had been receiving BID TAC (2.45 [1.52] mg/d) when treatment was converted to OD TAC, milligram for milligram. Follow-up including clinical evaluation and laboratory tests was at 7, 21, and 90 days postconversion. RESULTS: No significant differences were observed during follow-up in serum creatinine concentration, blood glucose level, hemoglobin level, or proteinuria. There were no episodes of acute rejection. No de novo posttransplantation diabetes mellitus was diagnosed; patients with diabetes required similar dosage of hypoglycemia treatment. Arterial pressure remained stable without changes in antihypertension treatment. Tacrolimus doses were not modified (2.45 [1.52] mg/d at baseline vs 2.45 [1.67] mg/d at 3 months postconversion; however, tacrolimus concentration decreased significantly (7.6 [1.8] ng/mL at baseline vs 6.42 [1.13] ng/mL at 3 months postconversion. Reduction in tacrolimus concentration was more remarkable in patients receiving a dose of less than 0.025 mg/kg/d. CONCLUSIONS: Conversion from BID TAC to OD TAC, milligram for milligram, is clinically safe; however, monitoring of tacrolimus concentration in patients receiving low dosage is mandatory to prevent subtherapeutic levels.

Menin molecular interactions: insights into normal functions and tumorigenesis.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disease predisposed by heterozygous germline mutations in the MEN1 tumor suppressor gene. Biallelic loss of MEN1 resulting from small mutation and/or loss of heterozygosity occurs in a large tissue spectrum of MEN1 tumors or non-hereditary tumors. Mouse models of MEN1 underexpression or overexpression have also supported the tumor-suppressor effect of the MEN1 gene. Menin, the 610-amino-acid protein encoded by MEN1, is expressed ubiquitously and found predominantly in the nucleus. Sequence analyses do not reveal motifs of known function other than two nuclear localization sequences. Menin has been found to partner in vitro with a variety of proteins that comprise transcription factors, DNA processing factors, DNA repair proteins, and cytoskeletal proteins. The diverse functions of menin interactors suggest roles for menin in multiple biological pathways. Inactivation of menin switches its JunD partner from a downstream action of growth suppression to growth promotion. This is a plausible mechanism for menin tumorigenesis.

Analysis of cadherin/catenin complexes in transformed thyroid epithelial cells: modulation by beta 1 integrin subunit.

We have analysed the expression of cadherin/catenin complex molecules in PC C13 rat thyroid cells transformed in vitro with different oncogenes. No significant downregulation of either E-cadherin, alpha-, beta- and gamma-catenin was detected following the introduction of activated forms of myc, adenovirus E1A, ras, raf, myc + ras, E1A + raf. However, ras- and raf-transformed PC C13 cells showed altered adherens junctions. An altered distribution of cadherin/catenin complexes characterized by radially oriented membrane spikes perpendicular to cell edges was the most prominent feature evidenced by immunofluorescence. No beta1 integrin localization was observed in areas where this altered pattern of E-cadherin expression was detected. However, beta1 integrin subunit expression was detected at areas of cell-cell contact where E-cadherin showed a normal pattern of expression. Furthermore, ras- and raf-transformed PC C13 cells showed the ability to migrate in collagen gels, in contrast to their normal untransformed counterpart. Overexpression of beta1 integrin was found to restore normal E-cadherin localization at cell-cell contacts and to partially inhibit the ability to migrate in collagen gels. Finally, two cell lines obtained by ras transformation in vivo, and derived from a rat primary thyroid carcinoma (TK6) and its lung metastasis (MPTK6), were found to have lost gamma-catenin expression. TK6 lost also E-cadherin expression and membrane localization of alpha-catenin. These results suggest that: i) in vitro thyroid cell transformation is associated to a change in cadherin/catenin complexes distribution rather than to a decrease in expression; ii) in vivo transformation is associated to the loss of expression of some of these molecules likely due to tumor progression; iii) alterations in beta1 integrin subunit expression can result in changes in cadherin/catenin function thus implying that an integrin-cadherin synergy may exist in thyroid cells.

Beta- and gamma-catenin expression in oral squamous cell carcinomas.

Cell-cell adhesion is mediated by cadherins (integral membrane proteins) which form a complex with catenins (cytoplasmatic proteins). Down-regulation of cadherins and more recently of catenins has frequently been detected in many types of human carcinomas, in which it has been associated to tumor progression. While E-cadherin expression has been extensively studied in many forms of human cancers, including oral SCC, less is known about the expression levels of catenins in oral SCCs. The objective of this study was to evaluate the role of these proteins in the carcinogenetic process of the oral cavity. We evaluated by immunohistochemistry beta- and gamma-catenin expression in 30 cases of intraoral squamous cell carcinomas at different degree of cellular differentiation. As already reported for E-cadherin, the beta- and gamma-catenin expression showed an inverse relationship with the degree of differentiation, being the membranous expression of both catenins homogeneously reduced in less differentiated oral squamous cell carcinomas (grade 3). More interestingly, a decreased expression of these molecules was also found at the invasive front of grade 2 and sometimes of grade 1 carcinomas, thus suggesting a more aggressive biological behavior of these cancer cells. An absent staining for both beta- and gamma-catenins could constitute a hallmark of aggressive biological behavior even in tumor still well or moderately differentiated, at least in the peripheral invading front constituted by less differentiated tumor cells.

Beta- and gamma-catenin expression in thyroid carcinomas.

Cadherins are calcium-dependent cell-cell adhesion molecules whose intracellular domain forms a complex with proteins required for their function, called catenins. Down-regulation of cadherins has frequently been detected in many types of human carcinomas, being associated with tumour progression. The present study investigates the immunohistochemical expression of E-cadherin and beta- and gamma-catenin in 27 human thyroid carcinomas. E-cadherin immunoreactivity was found to be decreased at cell-cell contacts in 8/15 (53 per cent) papillary, 5/7 (71 per cent) follicular, and 5/5 (100 per cent) anaplastic carcinomas. Beta-catenin membrane localization was found to be decreased in 6/15 (40 per cent) papillary, 2/7 (28 per cent) follicular, and 5/5 (100 per cent) anaplastic carcinomas. Gamma-catenin expression was partially or totally lost in 13/15 (86 per cent) papillary, 6/7 (85 per cent) follicular, and 5/5 (100 per cent) anaplastic carcinomas. A normal pattern of expression for these three molecules was observed in areas of normal tissue in each sample. These data indicate that in addition to E-cadherin, catenins are also down-regulated at cell-cell junctions in thyroid tumours and could represent potentially useful differentiation and/or transformation markers. The high frequency of alterations of gamma-catenin expression found in thyroid carcinomas suggests an important role for this gene product in thyroid carcinogenesis.

The insulin receptor content is increased in breast cancers initiated by three different oncogenes in transgenic mice.

The Insulin Receptor (IR) is a potential oncogene for mammary epithelial cells since its content is increased in most human breast cancer specimens, and both ligand-dependent malignant transformation and ligand-dependent enhanced growth occurs in cultured breast cells overexpressing the IR. To better understand whether the IR plays a role in mammary carcinogenesis which is independent of other initiation factors, we measured IR content in transgenic mouse models of breast cancer induced by 3 known oncogenes (Wnt-1, Neu, and Ret). Insulin receptor content was measured by a specific radioimmunoassay. In normal mammary gland tissues IR content was 14.6 +/- 1.4 ng/mg of protein (mean +/- SEM, n = 6). In the 3 cancers IR content was elevated (Neu = 36.1 +/- 4.6, n = 8, p < 0.002; Wnt-1 = 38.3 +/- 2.6, n = 13, p < 0.001; and Ret = 53.6 +/- 7.1, n = 7, p < 0.001). These data indicate that IR overexpression, in addition to being a potential oncogene, is increased in mouse tumors initiated by other oncogenes, and therefore may also play a supportive role in the growth of breast cancers.

Expression of the RET receptor tyrosine kinase and GDNFR-alpha in normal and leukemic human hematopoietic cells and stromal cells of the bone marrow microenvironment.

The RET proto-oncogene product is a receptor tyrosine kinase representing the signal-transducing molecule of a multisubunit surface receptor complex for the glial cell line-derived neurotrophic factor (GDNF), in which a novel glycosyl-phosphatidylinositol (PI)-linked protein (termed GDNFR-alpha) acts as the ligand-binding component. We have analyzed expression of RET and GDNFR-alpha in purified normal hematolymphopoietic cells, leukemia/lymphoma cell lines, and 154 primary samples from patients with hematopoietic malignancies encompassing different lineages and differentiation stages. Relatively low amounts of RET mRNA were found in early CD34+ hematopoietic progenitors, but RET transcripts appeared to increase after myelomonocytic maturation. No expression of RET was found in peripheral blood and tissue B and T lymphocytes. Analysis of human myelomonocytic cell lines was overall consistent with results obtained on purified normal cells. Accordingly, RET expression was mainly confined to acute myeloid leukemias (AMLs) displaying either monocytic (French-American-British M4 and M5) or intermediate-mature myeloid (M2 and M3) phenotypes, being less frequently detected in early myeloid (M0 and M1) AMLs. In contrast, RET mRNA was sporadically detected in B-cell tumors, whereas, among T-cell malignancies, RET transcripts were mainly detected in cells of postthymic and mature T-cell phenotype. RET broad detection in primary tumors was not paralleled by the mutual expression of GDNFR-alpha, which was detected only in 2 isolated primary samples and in 3 leukemia/lymphoma cell lines. However, GDNFR-alpha transcripts, in the absence of RET mRNA, were found in normal bone marrow stromal cells (BMSC), in BM fibroblasts, and in two osteoblast cell lines previously described to support normal hematopoiesis. In the presence of GDNF-receptors derived from BMSC by PI-specific phospholipase C cleavage, GDNF efficiently bound RET-expressing AML blasts and was functionally active by reducing their clonogenic growth and triggering the monocytic maturation of leukemic cells.

Development of mammary and cutaneous gland tumors in transgenic mice carrying the RET/PTC1 oncogene.

RET/PTC1 is a chimeric oncogene created by the fusion of the tyrosine kinase domain of RET to the 5'-terminal region of another gene named H4. So far, this oncogene has been found activated only in human papillary thyroid carcinomas. In order to investigate its transforming properties in vivo, we have produced transgenic mice carrying RET/PTC1 under the control of the H4 promoter. The transgene was expressed in several tissues, consistently with the ubiquitous expression of the wild type H4 gene. Mammary adenocarcinomas and, less frequently, hyperplasia of sebaceous glands and rare benign skin tumors, named pilomatrixomas, developed in these mice. The tumors were shown to express the transgene both at the RNA and protein level. These results demonstrate that the transforming ability of the RET/PTC1 oncogene is not restricted to the thyroid epithelium in vivo. Despite its ubiquitous expression, however, RET/PTC1 was able to induce only a limited number of tumor types; specifically mammary epithelium was affected by transgene expression, thus suggesting that RET/PTC1 is able to couple with transforming pathways specific for these glandular cells.

Development of thyroid papillary carcinomas secondary to tissue-specific expression of the RET/PTC1 oncogene in transgenic mice.

Gene rearrangements activating the RET proto-oncogene are frequently associated with human thyroid carcinomas belonging to the papillary subtype. These arrangements cause the fusion of the tyrosine-kinase domain of RET to the 5'-terminal region of different genes creating the RET/PTC chimeric oncogenes. Here we report the generation of transgenic mice lines expressing the RET/PTC1 oncogene under the control of the thyroid-specific rat thyroglobulin promoter. RET/PTC1-transgenic mice developed thyroid tumors displaying the histological aspect of papillary carcinomas. These tumors were slowly progressive and did not cause premature death of the animals. Two additional mice developed areas of thyroid hyperplasia. Immunohistochemical and reverse-transcriptase polymerase chain reaction analyses confirmed the thyroid-specific expression of the transgene. Given the frequency of activating rearrangements of RET in human papillary thyroid carcinomas we conclude that this animal system could be a good model for studying the neoplastic progression of thyroid carcinomas.