Congenital mesoblastic nephroma 50 years after its recognition: A narrative review.

Congenital mesoblastic nephroma (CMN) is a rare pediatric renal tumor with low malignant potential that most commonly occurs early in infancy. Treatment strategies are based on the few published CMN series, while a significant number of CMN patients have been described in case reports. The aim of this narrative review was to create an up-to-date overview of the literature. Complete surgical removal is curative in most cases. The risk of treatment-related mortality (both surgery- and chemotherapy-related) is relatively high in the first weeks of life, indicating that these young patients deserve special attention with respect to timing and type of treatment.

Image based feasibility of renal sparing surgery for very low risk unilateral Wilms tumors: a report from the Children's Oncology Group.

PURPOSE: Nephrectomy with lymph node sampling is the recommended treatment for children with unilateral Wilms tumor under the Children's Oncology Group protocols. Using radiological assessment, we determined the feasibility of performing partial nephrectomy in a select group of patients with very low risk unilateral Wilms tumor. MATERIALS AND METHODS: We reviewed imaging studies of 60 patients with a mean age of less than 2 years with very low risk unilateral Wilms tumor (mean weight less than 550 gm) to assess the feasibility of partial nephrectomy. We evaluated percentage of salvageable parenchyma, tumor location and anatomical features preventing a nephron sparing approach. RESULTS: A linear relationship exists between tumor weight and computerized tomography estimated tumor volume. Mean tumor weight in the study population was 315 gm. Partial nephrectomy was deemed feasible in only 5 of 60 patients (8%). CONCLUSIONS: When considering a select population with very low risk unilateral Wilms tumor (lower volume tumor), only a small percentage of nonpretreated patients are candidates for nephron sparing surgery.

Incidence and outcomes of patients with late recurrence of Wilms' tumor.

BACKGROUND: Most relapses from Wilms' tumor occur within 2 years from diagnosis. This study aims to describe the incidence and outcome of patients who experienced a late recurrence (LR) more than 5 years after diagnosis across several clinical trials, and to develop evidence-based recommendations for follow-up surveillance. METHODS: Available records on children with Wilms' tumor enrolled onto 10 national or international cooperative clinical trials were reviewed to identify patients who experienced a LR. RESULTS: Seventy of 13,330 (0.5%) patients with Wilms' tumor experienced a LR. No gender bias was observed. Median time elapsing between initial Wilms' tumor diagnosis and first recurrence was 13.2 years (range: 5.1-17.3 years). Initial tumor stage was: stage I (15); stage II (19); stage III (14); stage IV (8); bilateral disease stage V (14). The most frequent sites of relapse were--abdomen: 21, lungs: 20, and contralateral kidney: 15. Thirty-five children died of disease progression. Recurrence in the contralateral kidney was associated with a better outcome (13/15 patients alive), while initial tumor stage did not seem to influence the post-recurrence outcome. Therapies administered at recurrence varied between centers, preventing any conclusion about the best salvage treatment. CONCLUSIONS: LR of Wilms' tumor is rare and associated with similar outcome to those experiencing earlier recurrence. The low rate of LR does not justify prolonged monitoring. Further study of the biology of these tumors may give us some insights in regards to mechanisms on tumor cell dormancy or cancer stem cell maintenance.

Serine-phosphorylated STAT1 is a prosurvival factor in Wilms' tumor pathogenesis.

Wilms' tumor (WT), one of the most common pediatric solid cancers, arises in the developing kidney as a result of genetic and epigenetic changes that lead to the abnormal proliferation and differentiation of the metanephric blastema. As activation of signal transducers and activators of transcription (STATs) plays an important role in the maintenance/growth and differentiation of the metanephric blastema, and constitutively activated STATs facilitate neoplastic behaviors of a variety of cancers, we hypothesized that dysregulation of STAT signaling may also contribute to WT pathogenesis. Accordingly, we evaluated STAT phosphorylation patterns in tumors and found that STAT1 was constitutively phosphorylated on serine 727 (S727) in 19 of 21 primary WT samples and two WT cell lines. An inactivating mutation of S727 to alanine reduced colony formation of WT cells in soft agar by more than 80% and induced apoptosis under conditions of growth stress. S727-phosphorylated STAT1 provided apoptotic resistance for WT cells via upregulation of expression of the heat-shock protein (HSP)27 and antiapoptotic protein myeloid cell leukemia (MCL)-1. The kinase responsible for STAT1 S727 phosphorylation in WT cells was identified based upon the use of selective inhibitors as protein kinase CK2, not p38, MAP-kinase kinase (MEK)1/2, phosphatidylinositol 3'-kinase, protein kinase C or Ca/calmodulin-dependent protein kinase II (CaMKII). The inhibition of CK2 blocked the anchorage-independent growth of WT cells and induced apoptosis under conditions of growth stress. Our findings suggest that serine-phosphorylated STAT1, as a downstream target of protein kinase CK2, plays a critical role in the pathogenesis of WT and possibly other neoplasms with similar STAT1 phosphorylation patterns.

Telomerase activity in the normal and neoplastic rat mammary gland.

The 1-methyl-1-nitrosourea-induced rat mammary tumor model system is well studied, reproducible, and widely used. We have investigated whether these tumors possess higher telomerase activity than normal mammary tissue. Using the telomeric repeat amplification protocol assay, we found significantly higher telomerase activity in 36 mammary carcinomas than in 72 mammary glands of virgin rats. The level of telomerase activity in virgin rats was unaffected by strain, age, stage of the estrous cycle, or ovariectomy. However, mammary glands obtained from pregnant rats exhibited telomerase activity comparable to that found in the tumors, possibly reflecting the high epithelial content of these tissues. Indeed, isolated epithelial cells from virgin and pregnant mammary glands and from carcinomas had similar telomerase activities. Thus, telomerase activity is constitutive in the rat mammary epithelium and is not a unique characteristic of malignant transformation in this tissue. These results underscore the importance of attributing biochemical properties to specific cell types in a tissue, a situation not paralleled in the interpretation of data from in vitro models.

High telomerase reverse transcriptase (hTERT) messenger RNA level correlates with tumor recurrence in patients with favorable histology Wilms' tumor.

Telomerase is a reverse transcriptase that maintains chromosome ends, compensating for the progressive loss of DNA that occurs during replication. High telomerase enzyme activity is an unfavorable prognostic feature for several types of cancers. We investigated whether telomerase level predicts outcome for patients with the pediatric renal malignancy Wilms' tumor. In a case-cohort study of 78 patients with favorable histology Wilms' tumor, we compared tumor telomerase levels in patients with and without eventual recurrence. Three measures of telomerase were used: (a) telomerase enzyme activity; (b) expression of hTR, the RNA component of telomerase; and (c) mRNA expression of hTERT, the gene that encodes the catalytic component of the enzyme. Of the evaluable samples, 81% had detectable telomerase activity, 97% had detectable hTERT transcript, and 100% had detectable hTR. Weak correlations were observed between telomerase activity and hTR level (r = 0.34, P = 0.02) and between telomerase activity and hTERT mRNA level (r = 0.32, P = 0.04). Of the variables assessed, only hTERT mRNA expression correlated with outcome. The median hTERT mRNA level in tumors with recurrence was higher than that in tumors without recurrence (1.42 versus 0.97 units, P = 0.023, Wilcoxon). Univariate analysis of hTERT mRNA level as a continuous variable suggested that each unit increase in hTERT mRNA level increased the risk of recurrence (RR) by a factor of 1.66 [95% confidence interval (CI), 1.2-2.3; P < 0.005]. Compared with tumors with hTERT mRNA levels of 0-1 units, tumors with hTERT mRNA levels of 1-2 units had a RR of 2.72 (95% CI, 0.91-8.13; P = 0.074), and tumors with hTERT mRNA levels >2 units had a RR of 6.40 (95% CI, 1.49-27.67, P = 0.013). Multivariate analysis of hTERT mRNA level as a predictor of recurrence, adjusted for tumor stage and age at diagnosis, revealed a RR of 1.48 (95% CI, 0.9-2.6; P = 0.16). Measurement of hTERT mRNA level may, therefore, enable clinicians to identify a population of patients at high risk for recurrence and to adjust their therapy accordingly. A larger study will be necessary to determine whether hTERT expression is an independent prognostic indicator. Further biological investigation is warranted to discern whether the link between high hTERT expression and unfavorable prognosis is causative or correlative.

Telomerase activity and prognosis in primary breast cancers.

PURPOSE: Recent studies associate telomerase activity with prognostic factors and survival. We compared quantitative telomerase activity in primary tumors with traditional prognostic factors and outcome in a group of invasive but nonmetastatic breast cancers. PATIENTS AND METHODS: Telomerase activity was measured in 203 invasive breast cancers by the quantitative telomeric repeat amplification protocol method. Telomerase expression was compared with 28S rRNA level, tumor content, and clinical variables, including outcome. For clinical correlations, telomerase activity was standardized by two methods: (1) a correction for cellularity using 28S rRNA levels, and (2) a correction for the histologically determined invasive proportion of the specimen. RESULTS: Telomerase activity was found in 82% of breast cancers with measurable 28S rRNA levels. Telomerase activity was associated with the proliferative index (P <.01) of the tumor but not with any other prognostic variable. Neither uncorrected nor corrected telomerase activity was associated with relapse-free or overall survival in this study. CONCLUSION: Telomerase activity level was associated with the proliferative index of invasive breast cancers, but its measurement in samples from this group of nonmetastatic breast cancer patients did not predict survival.

Careful histological confirmation and microdissection reveal telomerase activity in otherwise telomerase-negative breast cancers.

Studies of invasive breast cancers consistently identify a subset of tumors without telomerase activity, compromising its utility as a tumor marker. Telomerase-negative tumors may represent a biologically different subset, or the result could be attributed to assay imperfections. To resolve this issue, we tested 105 invasive breast cancers for telomerase activity and found that 23 (22%) tumors were telomerase negative. Careful histological confirmation of an adjacent cryosection and/or microdissection of pure tumor cells reduced this number to 5 (5%). Thus, truly telomerase-negative invasive breast cancers are rare, making this enzyme a potentially very useful tumor marker in breast cancer.

Clear cell sarcoma of the kidney: a review.

Clear cell sarcoma of the kidney (CCSK) is a rare renal tumour that is observed most often in children under 3years of age. Only a few large series of CCSK have been reported and patients with CCSK are often included among patients with other types of childhood renal tumours. The purpose of this paper is to review the published series and case reports of CCSK and to create an up-to-date overview of clinical and histological features, genetics, treatment, and outcome.

Complex patterns of chromosome 9 alterations including the p16INK4a locus in Wilms tumours.

BACKGROUND: Previous data implicating genetic and epigenetic events on chromosome 9, including the CDKN2A/2B locus, as molecular predictors of Wilms tumour relapse, have been conflicting. AIMS: To clarify this using genome-wide and focused molecular genetic analysis. METHODS: Microarray-based comparative genomic hybridisation (aCGH) using genome-wide coverage was applied to 76 favourable histology Wilms tumours. Additional investigation of the 9p21 locus was carried out using loss of heterozygosity (LOH) and fluorescence in situ hybridisation (FISH), as well as immunohistochemistry for CDKN2A/p16(INK4a) on a paediatric renal tumour tissue microarray. RESULTS: Approximately half of the tumours were found to show chromosome 9 copy number changes. Those cases which harboured alterations comprised at least four distinct patterns: gain of the entire chromosome, loss of 9p, gain of 9q34, or a more complex combination of gains/losses. None of these tumour groups showed any statistically significant correlation with clinicopathological variables. Deletion mapping of 9p by LOH revealed several regions of overlap, including the CDKN2A/2B locus in 4/34 (11.8%) tumours, which was confirmed to represent hemizygous deletions by FISH. CDKN2A/p16(INK4a) protein expression was predominantly negative in Wilms tumours as assessed by immunohistochemistry on a tissue array, reflecting the expression pattern in normal kidney. However, 38/236 (16.1%) non-anaplastic Wilms tumours, 4/9 (44.4%) anaplastic Wilms tumours, 5/7 (71.4%) rhabdoid tumours of the kidney, and 4/10 (40%) clear cell sarcomas of the kidney showed nuclear CDKN2A/p16(INK4a )immunoreactivity. CONCLUSIONS: These data reveal the complex nature of genetic alterations on chromosome 9 in Wilms tumours, but do not provide evidence for their involvement in or association with treatment failure.

Analysis by array CGH of genomic changes associated with the progression or relapse of Wilms' tumour.

Despite aggressive salvage regimens, approximately half of all children who suffer a Wilms' tumour recurrence will die of their disease. Although there are increasing data on molecular genetic prognostic factors present in the tumour at diagnosis, there is little information regarding the molecular events that occur with Wilms' tumour progression and relapse. In the present study, microarray-based comparative genomic hybridization (aCGH) analysis has been carried out on 58 Wilms' tumour samples, which included 38 untreated primary and 20 recurrent tumours. A higher degree of copy number changes was observed in the recurrent tumours (33.0% genomic clones) than in the primary tumour (21.2%). Paired analysis highlighted the acquisition of 15q gain with high levels of IGF1R expression in the tumour recurrence in two cases. The most statistically significant abnormality acquired between diagnosis and relapse was loss of 17p. One case that experienced 17p loss was classified as favourable histology at diagnosis, but exhibited diffuse anaplasia at recurrence and had a homozygous TP53 deletion. Another instructive case with a constitutional 11p13 deletion presented with bilateral tumours and suffered two subsequent recurrences in the left kidney. A somatic WT1 mutation was found only in the right kidney tumour, while the constitutional 11p13 deletion was the only abnormality detected in the initial left kidney tumour by aCGH. The two subsequent relapses in the left kidney contained an accumulation of additional genetic alterations, including an independent WT1 mutation.

Three molecular determinants of malignant conversion and their potential as therapeutic targets.

The past decade has been marked by an explosion of knowledge regarding the dysregulation of cancer at the molecular level. It has become apparent that oncogenes, tumor suppressor genes, and other ancillary molecules interact in complex pathways that govern cellular homeostasis. We review three molecular events that have been implicated in tumorigenesis and define pathways ripe for the development of new therapeutic approaches: 1) activation of telomerase, 2) dysregulation of the patched/sonic hedgehog pathway, and 3) mutation of the INK4 alpha-ARF locus.

Unusual cleavage furrows in vertebrate tissue culture cells: insights into the mechanisms of cytokinesis.

In cultures of the epithelial cell lines, PtK2 and LLC-PK, some cells assume unusually large flattened morphologies and, during cell division, produce unusual cleavage furrows. We have microinjected some of these large cells with fluorescent actin and myosin probes to determine how the cell's shape and the position of its mitotic spindle affect the deposition of actin and myosin in the forming cleavage furrow. In cells with two spindles, contractile proteins were recruited not only to the cortex bordering the former metaphase plates but also to the cortex midway between each pair of adjacent nondaughter poles or centrosomes. The furrowing between adjacent poles seen in these cultured epithelial cells conformed to the furrows seen when echinoderm eggs were manipulated into a torus shape so that the poles of two mitotic spindles were adjacent to one another [Rappaport, 1961]. The recruitment of contractile proteins and the formation of furrows between adjacent centrosomes was a function of the distances between them. When adjacent centrosomes were positioned too close together neither contractile protein recruitment nor furrow formation occurred. If a normal-sized spindle was present in a very large cell, fibers of contractile protein assembled in the cortex above the former metaphase plate but they did not extend to the cell periphery, resulting in an inhibition of cytokinesis. In all injected cells, the recruitment of actin and myosin to the cell surfaces could first be detected at mid-anaphase before there was any visible sign of furrowing. Our results suggest that vertebrate cells share common mechanisms for the establishment of the cleavage furrow with echinoderm cells. The results are consistent with a model in which (1) the positions of the centrosomes and their linearly connected microtubules determine the position for the assembly of the cleavage furrow, and (2) the signal arrives at the surface within a few minutes after the initiation of anaphase. We speculate that an interaction of the ends of microtubules from adjacent centrosomes with the cell surface promotes a clustering of integral membrane protein(s) that interact with and target contractile proteins to a position midway between centrosomes where furrowing occurs.

Incorporation of fluorescently labeled actin and tropomyosin into muscle cells.

The two major proteins in the I-bands of skeletal muscle, actin and tropomyosin, were each labeled with fluorescent dyes and microinjected into cultured cardiac myocytes and skeletal muscle myotubes. Actin was incorporated along the entire length of the I-band in both types of muscle cells. In the myotubes, the incorporation was uniform, whereas in cardiac myocytes twice as much actin was incorporated in the Z-bands as in any other area of the I-band. Labeled tropomyosin that had been prepared from skeletal or smooth muscle was incorporated in a doublet in the I-band with an absence of incorporation in the Z-band. Tropomyosin prepared from brain was incorporated in a similar pattern in the I-bands of cardiac myocytes but was not incorporated in myotubes. These results in living muscle cells contrast with the patterns obtained when labeled actin and tropomyosin are added to isolated myofibrils. Labeled tropomyosins do not bind to any region of the isolated myofibrils, and labeled actin binds to A-bands. Thus, only living skeletal and cardiac muscle cells incorporate exogenous actin and tropomyosin in patterns expected from their known myofibrillar localization. These experiments demonstrate that in contrast to the isolated myofibrils, myofibrils in living cells are dynamic structures that are able to exchange actin and tropomyosin molecules for corresponding labeled molecules. The known overlap of actin filaments in cardiac Z-bands but not in skeletal muscle Z-bands accounts for the different patterns of actin incorporation in these cells. The ability of cardiac myocytes and non-muscle cells but not skeletal myotubes to incorporate brain tropomyosin may reflect differences in the relative actin-binding affinities of non-muscle tropomyosin and the respective native tropomyosins. The implications of these results for myofibrillogenesis are presented.

Dynamics of the endoplasmic reticulum in living non-muscle and muscle cells.

The dynamic changes of the endoplasmic reticulum (ER) in interphase and mitotic cells was detected by the vital fluorescent dye 3,3'-dihexyloxacarbocyanine iodide. Two types of arrays characterize the continuous ER system in the non-muscle PtK2 cell: 1) a lacy network of irregular polygons and 2) long strands of ER that are found aligned along stress fibers. In cross-striated myotubes there was a periodic localization of fluorescence over each I-band corresponding to the positions of the terminal cisternae of the sarcoplasmic reticulum (SR). In contrast to the arrangement in muscle cells, the alignment of the long strands of ER alon stress fibers showed no strict periodicity that could be correlated with the sarcomeric units of the stress fibers. The ER and SR arrays seen in living cells were also detected in fixed cells stained with antibodies directed against proteins of the endoplasmic reticulum and sarcoplasmic reticulum, respectively. Observations of vitally stained PtK2 cells at 1 to 2 minute intervals using low light level video cameras and image processing techniques enabled us to see the polygonal ER units form and undergo changes in their shapes. During cell division, the ER, rhodamine 123-stained mitochondria, and phagocytosed fluorescent beads were excluded from the mitotic spindle while soluble proteins were not. No obvious concentration or alignment of membranes could be found associated with the contractile proteins in the cleavage furrow. After completion of cell division there was a redeployment of the ER network in each daughter cell.

Analysis of cell division using fluorescently labeled actin and myosin in living PtK2 cells.

Actin and the light chains of myosin were labeled with fluorescent dyes and injected into interphase PtK2 cells in order to study the changes in distribution of actin and myosin that occurred when the injected cells subsequently entered mitosis and divided. The first changes occurred when stress fibers in prophase cells began to disassemble. During this process, which began in the center of the cell, individual fibers shortened, and in a few fibers, adjacent bands of fluorescent myosin could be seen to move closer together. In most cells, stress fiber disassembly was complete by metaphase, resulting in a diffuse distribution of the fluorescent proteins throughout the cytoplasm with the greatest concentration present in the mitotic spindle. The first evidence of actin and myosin concentration in a cleavage ring occurred at late anaphase, just before furrowing could be detected. Initially, the intensity of fluorescence and the width of the fluorescent ring increased as the ring constricted. In cells with asymmetrically positioned mitotic spindles, both protein concentration and furrowing were first evident in the cortical regions closest to the equator of the mitotic spindle. As cytokinesis progressed in such asymmetrically dividing cells, fluorescent actin and myosin appeared at the opposite side of the cell just before furrowing activity could be seen there. At the end of cytokinesis, myosin and actin were concentrated beneath the membrane of the midbody and subsequently became organized in two rings at either end of the midbody.

Occurrence of fibers and their association with talin in the cleavage furrows of PtK2 cells.

PtK2 cells of exceptionally large size were microinjected with fluorescently labeled probes for actin, myosin, filamin, and talin in order to follow the assembly of the contractile proteins into the cleavage furrows. Whereas in cells of normal size, there is usually a diffuse pattern of localization of proteins in the cleavage furrow, in these large, flat cells the labeled proteins localized in fibers in the cleavage furrow. Often, the fibers were striated in a pattern comparable to that measured in the stress fibers of the same cell type. The presence of talin in discrete plaques along fibers in the cleavage furrows of the large cells suggests a further similarity between cleavage furrow and stress fiber structure. The presence of filamin in the cleavage furrows also suggests the possibility of an overlapping mechanism in addition to that of a talin mediated mechanism for the attachment of actin filaments to the cell surfaces in the cleavage furrow. A model is presented that emphasizes the interrelationships between stress fibers, myofibrils, and cleavage furrows.