Radical Nephroureterectomy Tetrafecta: A Proposal Reporting Surgical Strategy Quality at Surgery.

Background: Standardized methods for reporting surgical quality have been described for all the major urological procedures apart from radical nephroureterectomy (RNU). Objective: To propose a tetrafecta criterion for assessing the quality of RNU based on a consensus panel within the Young Association of Urology (YAU) Urothelial Group, and to test the impact of this tetrafecta in a multicenter, large contemporary cohort of patients treated with RNU for upper tract urothelial carcinoma (UTUC). Design setting and participants: This was a retrospective analysis of 1765 patients with UTUC treated between 2000 and 2021. Outcome measurements and statistical analysis: We interviewed the YAU Urothelial Group to propose and score a list of items to be included in the "RNU-fecta." A ranking was generated for the criteria with the highest sum score. These criteria were applied to a large multicenter cohort of patients. Kaplan-Meier curves were built to evaluate differences in overall survival (OS) rates between groups, and a multivariable logistic regression model was used to find the predictors of achieving the RNU tetrafecta. Results and limitations: The criteria with the highest score included three surgical items such as negative soft tissue surgical margins, bladder cuff excision, lymph node dissection according to guideline recommendations, and one oncological item defined by the absence of any recurrence in ≤12 mo. These items formed the RNU tetrafecta. Within a median follow-up of 30 mo, 52.6% of patients achieved the RNU tetrafecta. The 5-yr OS rates were significantly higher for patients achieving tetrafecta than for their counterparts (76% vs 51%). Younger age, lower body mass index, and robotic approach were found to be independent predictors of tetrafecta achievement. Conversely, a higher Eastern Cooperative Oncology Group score, higher clinical stage, and bladder cancer history were inversely associated with tetrafecta. Conclusions: Herein, we present a "tetrafecta" composite endpoint that may serve as a potential tool to assess the overall quality of the RNU procedure. Pending external validation, this tool could allow a comparison between surgical series and may be useful for assessing the learning curve of the procedure as well as for evaluating the impact of new technologies in the field. Patient summary: In this study, a tetrafecta criterion was developed for assessing the surgical quality of radical nephroureterectomy in patients with upper tract urothelial carcinoma. Patients who achieved tetrafecta had higher 5-yr overall survival rates than those who did not.

Clinical Approach to Mast Cell Activation Syndrome: A Practical Overview.

The diagnosis of mast cell activation syndrome (MCAS) is defined by 3 criteria: (1) typical clinical signs and symptoms of acute, recurrent (episodic), and systemic mast cell activation (MCA); (2) increase in tryptase level to >20% + 2 ng/mL within 1-4 hours after onset of the acute crisis; and (3) response of MCA symptoms to antimediator therapy. Classification of MCAS requires highly sensitive and specific methodological approaches for the assessment of clonal bone marrow mast cells at low frequencies. The Spanish Network on Mastocytosis score has been used successfully as a predictive model for selecting MCAS candidates for bone marrow studies based on a high probability of an underlying clonal mast cell disorder. In this article, we propose a diagnostic algorithm and focus on the practical evaluation and management of patients with suspected MCAS.

Predictive factors of overall and major postoperative complications after partial nephrectomy: Results from a multicenter prospective study (The RECORd 1 project).

INTRODUCTION AND OBJECTIVES: To analyze postoperative complications and to assess for significant predictive factors during partial nephrectomy (PN) using a large multicenter dataset. METHODS: Patients who underwent PN for clinical T1 renal tumors at 19 urological Italian centers (Registry of Conservative Renal Surgery [RECORd] project) were evaluated between 2009 and 2012. Anthropometric data, comorbidities and perioperative outcomes were analyzed. Complications were divided as intra- and postoperative, medical and surgical, as appropriate. The severity of postoperative complications was graded according to the modified Clavien classification system. Patients who experienced intraoperative complications were excluded from the analyses for the potential confounding effect in the evaluation of predicting factors for postoperative complications. RESULTS: Overall, 979 patients were analyzed: open, laparoscopic and robot-assisted (available since 2011) surgical approaches were used in 522 (56.4%), 286 (30.9%) and 117 (12.6%) cases, respectively. Surgical postoperative complications were reported in 121 (13.1%) cases (32 (3.5%) were Clavien 3), medical were reported in 52 (5.6%) cases (3 (0.3%) were Clavien 3). No Clavien 4 complications were reported. At multivariable analysis, ECOG score ≥1 (OR 1.98; p = 0.002), lower preoperative hemoglobin (OR 0.71; p < 0.0001) and open surgical approach (2.91; p = 0.02) were significant predictive factors of overall surgical postoperative complications, ECOG score ≥1 (OR 1.93; p = 0.04) and surgical approach (p = 0.05) were significant predictive factors of Clavien 3 either surgical or medical postoperative complications. CONCLUSIONS: Comorbidities and surgical approach should be considered in preoperative evaluation of patients undergoing PN, as they resulted to play a significant role in the occurrence of postoperative complications.

A snapshot of nephron-sparing surgery in Italy: a prospective, multicenter report on clinical and perioperative outcomes (the RECORd 1 project).

INTRODUCTION: Nephron-sparing surgery (NSS) has become the standard of care for the surgical management of small and clinically localized renal cell carcinoma (RCC). The conservative management of those RCCs is increasing over time. Aim of this study was to report a snapshot of the clinical, perioperative and oncological results after NSS for RCC in Italy. MATERIAL AND METHODS: We evaluated all patients who underwent conservative surgical treatment for renal tumours between January 2009 and December 2012 at 19 urological Italian Centers (RECORd project). Perioperative, radiological and histopathological data were recorded. Surgical eras (2009 vs 2012 and year periods 2009-2010 vs 2011-2012) were compared. RESULTS: Globally, 983 patients were evaluated. More recently, patients undergoing NSS were found to be significantly younger (p = 0.05) than those surgically treated in the first study period, with a significantly higher rate of NSS with relative and imperative indication (p < 0.001). More recently, a higher percentage of procedures for cT1b or cT2 renal tumours was observed (p = 0.02). Utilization rate of open partial nephrectomy (OPN) constantly decreased during years, laparoscopic partial nephrectomy (LPN) remained almost constant while robot-assisted partial nephrectomy (RAPN) increased. The rate of clampless NSS constantly increased over time. The use of at least one haemostatic agent has been significantly more adopted in the most recent surgical era (p < 0.001). CONCLUSIONS: The utilization rate of NSS in Italy is increasing, even in elective and more complex cases. RAPN has been progressively adopted, as well as the intraoperative utilization of haemostatic agents and the rate of clampless procedures.

Simple enucleation versus standard partial nephrectomy for clinical T1 renal masses: perioperative outcomes based on a matched-pair comparison of 396 patients (RECORd project).

OBJECTIVES: To compare simple enucleation (SE) and standard partial nephrectomy (SPN) in terms of surgical results in a multicenter dataset (RECORd Project). MATERIALS AND METHODS: patients treated with nephron sparing surgery (NSS) for clinical T1 renal tumors between January 2009 and January 2011 were evaluated. Overall, 198 patients who underwent SE were retrospectively matched to 198 patients who underwent SPN. The SPN and SE groups were compared regarding intraoperative, early post-operative and pathologic outcome variables. Multivariable analysis was applied to analyze predictors of positive surgical margin (PSM) status. RESULTS: SE was associated with similar WIT (18 vs 17.8 min), lower intraoperative blood loss (177 vs 221 cc, p = 0.02) and shorter operative time (121 vs 147 min; p < 0.0001). Surgical approach (laparoscopic vs. open), tumor size and type of indication (elective/relative vs absolute) were associated with WIT >20 min. The incidence of PSM was significantly lower in patients treated with SE (1.4% vs 6.9%; p = 0.02). At multivariable analysis, PSM was related to the surgical technique, with a 4.7-fold increased risk of PSM for SPN compared to SE. The incidence of overall, medical and surgical complications was similar between SE and SPN. CONCLUSIONS: Type of NSS technique (SE vs SPN) adopted has a negligible impact on WIT and postoperative morbidity but SE seems protective against PSM occurrence.

Elevated phenylacetic acid levels do not correlate with adverse events in patients with urea cycle disorders or hepatic encephalopathy and can be predicted based on the plasma PAA to PAGN ratio.

BACKGROUND: Phenylacetic acid (PAA) is the active moiety in sodium phenylbutyrate (NaPBA) and glycerol phenylbutyrate (GPB, HPN-100). Both are approved for treatment of urea cycle disorders (UCDs) - rare genetic disorders characterized by hyperammonemia. PAA is conjugated with glutamine in the liver to form phenylacetyleglutamine (PAGN), which is excreted in urine. PAA plasma levels ≥ 500 µg/dL have been reported to be associated with reversible neurological adverse events (AEs) in cancer patients receiving PAA intravenously. Therefore, we have investigated the relationship between PAA levels and neurological AEs in patients treated with these PAA pro-drugs as well as approaches to identifying patients most likely to experience high PAA levels. METHODS: The relationship between nervous system AEs, PAA levels and the ratio of plasma PAA to PAGN were examined in 4683 blood samples taken serially from: [1] healthy adults [2], UCD patients of ≥ 2 months of age, and [3] patients with cirrhosis and hepatic encephalopathy (HE). The plasma ratio of PAA to PAGN was analyzed with respect to its utility in identifying patients at risk of high PAA values. RESULTS: Only 0.2% (11) of 4683 samples exceeded 500 µg/ml. There was no relationship between neurological AEs and PAA levels in UCD or HE patients, but transient AEs including headache and nausea that correlated with PAA levels were observed in healthy adults. Irrespective of population, a curvilinear relationship was observed between PAA levels and the plasma PAA:PAGN ratio, and a ratio>2.5 (both in µg/mL) in a random blood draw identified patients at risk for PAA levels>500 µg/ml. CONCLUSIONS: The presence of a relationship between PAA levels and reversible AEs in healthy adults but not in UCD or HE patients may reflect intrinsic differences among the populations and/or metabolic adaptation with continued dosing. The plasma PAA:PAGN ratio is a functional measure of the rate of PAA metabolism and represents a useful dosing biomarker.

Concomitant CXCR4 and CXCR7 expression predicts poor prognosis in renal cancer.

CXCR4 is a chemokine receptor implicated in the metastatic process. The CXCR4 ligand, CXCL12, was shown to bind also the CXCR7 receptor, a recently deorphanized chemokine receptor whose signalling pathway and function are still controversial. This study was conducted to determine patients clinic-pathological factors and outcome according to the expressions of CXCR4 and CXCR7 in renal cell carcinoma (RCC). CXCR4 and CXCR7 expression was evaluated in 223 RCC patients through immunohistochemistry; moreover CXCR4 and CXCR7 was detected in 49 others consecutive RCC patients trough RT- PCR. CXCR4 expression was low in 42/223 RCC (18.8%), intermediate in 71/223 (31.9%) and high in 110/223 (49.3%). CXCR7 expression was low in 44/223 RCC patients (19.8%), intermediate in 65/223 (29.1%) and high in 114/223 (51.1%). High CXCR4 and high CXCR7 expression predicted shorter disease free survival. In multivariate analysis, high CXCR4 expression (p= 0.0061), high CXCR7 (p= 0.0194) expression and the concomitant high expression of CXCR4 and CXCR7 (p= 0.0235) are independent prognosis factors. Through RT-PCR, CXCR4 was overexpressed in 36/49 and CXCR7 in 33/49 samples correlating with symptoms at diagnosis and lymph nodes status. So we can hypothesize that CXCR4 and CXCR7, singularly evaluated and in combination, are valuable prognostic factors in RCC patients.

Diagnosis of clavulanic acid allergy using basophil activation and leukotriene release by basophils.

Clavulanic acid is a potent inhibitor of B-lactamase that is increasingly prescribed in association with amoxicillin. We report 2 cases of patients who experienced pruritus, wheals, and angioedema after oral intake of amoxicillin/clavulanic acid. Routine skin tests for B-lactam antibiotics and specific immunoglobulin (Ig) E were negative in both patients. Analysis of CD63 expression by the basophil activation test (BAT) using flow cytometry and of sulphidoleukotriene (sLT) release by basophils using the cellular allergen stimulation test (CAST) revealed significant positive responses with amoxicillin/clavulanic acid and with clavulanic acid, and negative responses with amoxicillin and other beta-lactam antibiotics. In addition, cultured CD3+CD4+ cells showed a significant increase in the expression of CD69, CD25, and HLA-DR in the presence of clavulanic acid. Both patients tolerated therapeutic doses of amoxicillin. BAT and CAST are useful ex vivo procedures for the detection of specific IgE-mediated allergy to clavulanic acid, especially for patients with negative skin test results.

Validación del uso de modelos fotográficos para cuantificar el tamaño de las porciones de alimentos / Validation of food photographs as a tool to quantify portion size

The aim of this research was to validate the usefulness of a food photograph atlas for the estimation of food portion sizes. The instrument was tested in 76 adults, of whom 34 were professionals and 42 had only primary school education. Selected foods were weighed before its intake and later on a questionnaire was made about food portion sizes using the food photograph atlas. Total corrected answers were 60.9 percent in the university group and 52.7 percent in the primary school group (p=0.07). Correlation between real weight and the estimated weight for the total observations was good [r =0.722 (p=0.003)] and percentage of variation between both weights had a range of - 29 percent to + 256 percent. Food photograph models give an approximation to food portion sizes, so they are useful instruments to be use in nutritional surveys.

La finalidad de esta investigación fue validar la utilidad de un atlas fotográfico para estimar el peso de las porciones de alimentos. El instrumento se probó en 76 adultos; de los cuales 34 eran profesionales y 42 eran personas con estudios primarios. Los alimentos seleccionados se pesaron previo a su consumo y posteriormente se indagó sobre la cantidad recibida, utilizando para la estimación las fotografías del atlas. El porcentaje de observaciones acertadas fue del 60.9 por ciento en el grupo con estudios universitarios y del 52.7 por ciento en el grupo con estudios primarios (p= 0.07). La correlación hallada para el total de estimaciones entre el peso estimado y el peso real fue elevada y significativa r =0.722 (p=0.003) y el porcentaje de variación entre ambos pesos tuvo un rango de - 29 por ciento a + 256 por ciento. Los modelos fotográficos de alimentos ofrecen una aproximación a las porciones consumidas, por lo que resultan un instrumento de utilidad para la realización de encuestas alimentarias.

Regulatory role of tetraspanin CD9 in tumor-endothelial cell interaction during transendothelial invasion of melanoma cells.

Heterotypic interaction among tumor cells (TCs) and endothelial cells (ECs) may play a critical role during the vascular dissemination of neoplastic cells and during pathologic angiogenesis in tumors. To identify molecules involved in these processes, the distribution of vascular junctional proteins was first studied by immunofluorescence at sites of heterologous intercellular contact using TC-EC mosaic monolayers grown on 2-dimensional collagen. Several members of the tetraspanin superfamily, including CD9, CD81, and CD151, were found to localize at the TC-EC contact area. The localization of tetraspanins to the TC-EC heterologous contact area was also observed during the active transmigration of TCs across EC monolayers grown onto 3-dimensional collagen matrices. Dynamic studies by time-lapse immunofluorescence confocal microscopy showed an active redistribution of endothelial CD9 to points of melanoma insertion. Anti-CD9 monoclonal antibodies were found to specifically inhibit the transendothelial migration of melanoma cells; the inhibitory effect was likely caused by a strengthening of CD9-mediated heterotypic interactions of TCs to the EC monolayer. These data support a novel mechanism of tetraspanin-mediated regulation of TC transcellular migration independent of TC motility and growth during metastasis and a role for these molecules in the formation of TC-EC mosaic monolayers during tumor angiogenesis.

Expression of functional chemokine receptors CXCR3 and CXCR4 on human melanoma cells.

Chemokines are secreted into the tumor microenvironment by tumor-infiltrating inflammatory cells as well as by tumor cells. Chemokine receptors mediate agonist-dependent cell responses, including migration and activation of several signaling pathways. In the present study we show that several human melanoma cell lines and melanoma cells on macroscopically infiltrated lymph nodes express the chemokine receptors CXCR3 and CXCR4. Using the highly invasive melanoma cell line BLM, we demonstrate that the chemokine Mig, a ligand for CXCR3, activates the small GTPases RhoA and Rac1, induces a reorganization of the actin cytoskeleton, and triggers cell chemotaxis and modulation of integrin VLA-5- and VLA-4-dependent cell adhesion to fibronectin. Furthermore, the chemokine SDF-1alpha, the ligand of CXCR4, triggered modulation of beta(1) integrin-dependent melanoma cell adhesion to fibronectin. Additionally, Mig and SDF-1alpha activated MAPKs p44/42 and p38 on melanoma cells. Expression of functional CXCR3 and CXCR4 receptors on melanoma cells indicates that they might contribute to cell motility during invasion as well as to regulation of cell proliferation and survival.

Insulin increases the turnover rate of Na+-K+-ATPase in human fibroblasts.

Insulin stimulates K+ transport by the Na+-K+-ATPase in human fibroblasts. In other cell systems, this action represents an automatic response to increased intracellular [Na+] or results from translocation of transporters from an intracellular site to the plasma membrane. Here we evaluate whether these mechanisms are operative in human fibroblasts. Human fibroblasts expressed the alpha(1) but not the alpha(2) and alpha(3) isoforms of Na+-K+-ATPase . Insulin increased the influx of Rb+, used to trace K+ entry, but did not modify the total intracellular content of K+, Rb+, and Na+ over a 3-h incubation period. Ouabain increased intracellular Na+ more rapidly in cells incubated with insulin, but this increase followed insulin stimulation of Rb+ transport. Bumetanide did not prevent the increased Na+ influx or stimulation of Na+-K+-ATPase. Stimulation of the Na+-K+-ATPase by insulin did not produce any measurable change in membrane potential. Insulin did not affect the affinity of the pump toward internal Na+ or the number of membrane-bound Na+-K+-ATPases, as assessed by ouabain binding. By contrast, insulin slightly increased the affinity of Na+-K+-ATPase toward ouabain. Phorbol esters did not mimic insulin action on Na+-K+-ATPase and inhibited, rather than stimulated, Rb+ transport. These results indicate that insulin increases the turnover rate of Na+-K+-ATPases of human fibroblasts without affecting their number on the plasma membrane or modifying their dependence on intracellular [Na+].

Maturation-dependent expression and function of the CD49d integrin on monocyte-derived human dendritic cells.

Dendritic cells (DC) are highly specialized APC that are critical for the initiation of T cell-dependent immune responses. DC exert a sentinel function while immature and, after activation by inflammatory stimuli or infectious agents, mature and migrate into lymphoid organs to prime T cells. We have analyzed integrin expression on monocyte-derived DC (MDDC) and found that expression of CD49d integrins (CD49d/CD29 and CD49d/beta7) was induced/up-regulated during TNF-alpha- or LPS-initiated MDDC maturation, reflecting the induction/up-regulation of CD49d and beta7 mRNA. CD49d mRNA steady-state level increased more than 10 times during maturation, with the highest levels observed 24 h after TNF-alpha treatment. CD49d integrin expression conferred mature MDDC with an elevated capacity to adhere to the CS-1 fragment of fibronectin, and also mediated transendothelial migration of mature MDDC. Up-regulation of CD49d integrin expression closely paralleled that of the mature DC marker CD83. CD49d integrin expression was dependent on cell maturation, as its induction was abrogated by N:-acetylcysteine, which inhibits NF-kappaB activation and the functional and phenotypic maturation of MDDC. Moreover, CD49d integrin up-regulation and MDDC maturation were prevented by SB203580, a specific inhibitor of p38 mitogen-activated protein kinase, but were almost unaffected by the mitogen-activated protein/extracellular signal-related kinase kinase 1/2 inhibitor PD98059. Our results support the existence of a link between functional and phenotypic maturation of MDDC and CD49d integrin expression, thus establishing CD49d as a maturation marker for MDDC. The differential expression of CD49d on immature and mature MDDC might contribute to their distinct motility capabilities and mediate mature DC migration into lymphoid organs.

Insulin-induced gene 33 mRNA expression in Chinese hamster ovary cells is insulin receptor dependent.

Gene 33 (g33) is a non-tissue-specific gene regulated in rat liver and hepatoma cells by insulin and other agents. It is thought to participate in the transition from quiescence to proliferation in mitogen-treated cells. The mechanism(s) by which insulin exerts its action on g33 are not totally understood; it is unclear whether a functional insulin receptor is required for this action. In this study, we evaluate the mechanism for insulin induction of g33 mRNA in Chinese hamster ovary (CHO) cells transfected with the neomycin-resistant plasmid (CHONeoB), human insulin receptor (CHONewIRa), and a kinase-defective insulin receptor mutated at the ATP-binding site (CHOK1018A). Transfected cells had higher levels of insulin binding than that of CHONeoB cells; insulin-induced phosphorylation of the insulin receptor and its intracellular substrates were impaired in CHOK1018A cells. Maximal insulin induction of mRNA(g33) occurred 3 h after hormonal exposure in all cell lines. The degree of insulin stimulation of g33 mRNA levels was four- to sixfold higher in CHONewIRa than in CHONeoB or CHOK1018A cells, which had minimal levels of insulin-stimulated g33 mRNA levels. Half-maximal stimulation of g33 mRNA levels was observed at 0.06 +/- 0.01 nM in CHONewIRa cells, consistent with insulin interaction with its own receptor. Wortmannin, an inhibitor of phosphatidyl inositol 3-kinase (PI3K), had some effects on insulin stimulation of g33 mRNA in CHO NewIRa cells. PD98059, an inhibitor of mitogen-activated kinase kinase (MAPKK), and rapamycin, a p70 S6 kinase inhibitor, had minimal effect on insulin stimulation of g33 mRNA in all cells tested. By contrast, hydroxy-2-naphthalenylmethyl)phosphonic acid triacetoxymethyl ester (HNMPA(AM)(3), a selective inhibitor of the insulin receptor tyrosine kinase, caused complete inhibition of insulin stimulation of g33 mRNA levels. These data indicate that the insulin receptor with intact kinase activity is required for insulin stimulation of g33 mRNA levels. They also suggest that AKT, a PI 3-kinase downstream effector molecule, could mediate insulin stimulation of g33 mRNA. The mechanism(s) of insulin regulation of g33 expression downstream of receptor do not seem to rely entirely on the classic insulin receptor transduction pathway, as a minor effect was observed upon inhibition of MAPKK, suggesting that multiple pathways may be involved.

Lck domains differentially contribute to pre-T cell receptor (TCR)- and TCR-alpha/beta-regulated developmental transitions.

Maturational changes at the CD4(-)CD8(-) double negative (DN) to CD4(+)CD8(+) double positive (DP) transition are dependent on signals generated via the pre-T cell receptor (TCR) and the nonreceptor protein tyrosine kinase p56(lck) (Lck). How Lck activities are stimulated or relayed after pre-TCR formation remains obscure. Our structure-function mapping of Lck thymopoietic properties reveals that the noncatalytic domains of Lck are specialized to signal efficient cellular expansion at DN to DP transition. Moreover, although substitution of the Lck catalytic domain with FynT sequences minimally impacts DP development, single positive thymocytes are most efficiently produced in the presence of kinases containing both the NH(2)-terminal and catalytic regions of Lck. These findings demonstrate that the Lck structure is uniquely adapted to mediate signals at both major transitions in thymopoiesis.

Functional characterization of the carnitine transporter defective in primary carnitine deficiency.

Primary carnitine deficiency is an autosomal recessive disorder caused by defective carnitine transport which impairs fatty acid oxidation and manifests as nonketotic hypoglycemia or skeletal or heart myopathy. Here we report the functional characterization of this transporter in human fibroblasts. Carnitine enters normal cells by saturable and unsaturable routes, the latter corresponding to Na+-independent uptake. Saturable carnitine transport was absent in cells from patients with primary carnitine deficiency. In control cells, saturable carnitine transport was energized by the electrochemical gradient of Na+. Carnitine uptake was not inhibited by amino acid substrates of transport systems A, ASC, and X-AG, but was inhibited competitively (in potency order) by butyrobetaine > carnitine > palmitoylcarnitine = acetylcarnitine > betaine. Carnitine uptake was also noncompetitively inhibited by verapamil and quinidine, inhibitors of the multidrug resistance family of membrane transporters, suggesting that the carnitine transporter may share a functional motif with this class of transporters. A high-affinity carnitine transporter was present in kidney 293 cells, but not in HepG2 liver cells, whose carnitine transporter had a Km in the millimolar range. These result indicate the presence of multiple types of carnitine transporters in human cells.

Regulation of Src-family protein tyrosine kinase transcription during lymphocyte ontogeny.

The distribution and quantity of cellular signaling elements influence response patterns to a variety of stimuli. As protein tyrosine phosphorylation is a requisite event induced by a majority of surface receptors, and protein tyrosine kinases of the src-family (src-PTKs) act as proximal transducers for many hematopoietic receptors, we have designed a quantitative RT-PCR assay to measure src-family PTK expression during critical stages of lymphocyte ontogeny. With this assay we demonstrate that the distal promoter element regulating expression of lck, a src-PTK essential for T-cell development and activation, is similarly regulated during ontogeny of T and B cells. However, lck transcript abundance is drastically reduced in B lineage cells, suggesting that transcriptional elements influencing lck promoter activity are modulated in these cells. Moreover, although transcripts encoding the src-PTK fyn accumulate at 0.1% of lck mRNA levels in thymocytes, diminished activity of the lck distal promoter in the B-cell background brings lck and fyn transcript levels to near equivalence in this population. Importantly, transcripts arising from the lck distal promoter element and the fyn locus are similarly upregulated during developmental transitions associated with antigen-receptor expression in both B and T cells. These findings suggest that although the magnitude of lck and fyn expression is differentially regulated in B and T cells, expression at these loci is similarly developmentally programmed during ontogeny of both lymphocyte lineages.