Omental mesenteric myxoid hamartoma, a subtype of inflammatory myofibroblastic tumor? Considerations based on the histopathological evaluation of four cases.

Omental mesenteric myxoid hamartoma (OMH) is a distinctive myxoid lesion of infancy, characterized by a benign clinical behavior. In the current World Health Organization (WHO) classification of soft tissue tumors, it is considered as part of the morphologic spectrum of inflammatory myofibroblastic tumors (IMT), but this relationship with IMT is still subject to debate. Four lesions with histologic features of OMH occurring in newborns and toddlers are described and compared with classic, ALK-positive IMT. All OMH showed a peculiar dot-like immunostaining for ALK, which, in one of the cases, was cytogenetically found to be associated with an inversion of the ALK gene. While OMHs were positive for smooth muscle actin (SMA), desmin, WT1, podoplanin, and cytokeratins (CAM5.2 and AE1-3), IMT were consistently positive only for SMA (10 cases). ALK-1 displayed cytoplasmic staining in IMT and characteristic paranuclear dot-like staining in OMH.

Wilms' tumor 1 (WT1) gene in hematopoiesis: a surrogate marker of cell proliferation as a possible mechanism of action?

BACKGROUND: Wilms' tumor 1 (WT1) gene expression is seen in a significant number of cases of human neoplasia; however, the mechanism of action remains to be clarified. We hypothesized that WT1 gene is a surrogate marker of proliferation in normal hematopoietic cells and leukemias. While we and others have recognized its value as a tool for the detection of minimal residual disease (MRD), the objective of this study was to confirm our hypothesis regarding normal. METHODS: Samples from healthy donors (n=16) and UC blood (n=9) were cultured in Methocult for 21 days. Colonies were analyzed on days 7, 14 and 21 by RT-PCR for WT1 gene expression. Our positive controls were samples from patients with leukemia (n=91). Negative controls were from normal volunteers without stimulation (n=26). RESULTS: Results showed a statistically significant difference (P<0.0001) between cultured groups, with the highest level of WT1 gene expression in the positive controls and on day 14, when cells are at their maximal proliferation. DISCUSSION: In conclusion, WT1 gene expression in the proliferating colonies was highest on day 14, although less than in leukemia samples, confirming our hypothesis that WT1 gene is a surrogate marker of proliferation, not only in leukemogenesis but also, to a lesser degree, in normal cell proliferation.

Platelet chimerism by polymerase chain reaction (PCR) utilizing variable number of tandem repeats (VNTR) in allogeneic stem cell transplant in children: a new novel approach to full chimerism analysis.

Evaluation of chimerism following allogeneic transplantation has been performed traditionally focusing on two cellular compartments, namely lymphoid and myeloid. However, none has been described so far to evaluate platelet chimerism. In order to achieve full chimerism in all three cellular compartments, we prospectively obtained 138 samples of peripheral blood in 55 patients at different post transplant periods following allogeneic hematopoietic transplantation. Evaluation of chimerism was performed utilizing tests of variable number of tandem repeat (VNTR) and sex determination by quantitative polymerase chain reaction (PCR). Tests for platelet chimerism using platelet-rich plasma were simultaneously analyzed with samples for T-cell lymphoid and myeloid compartments. Complete donor chimerism was noted in 49 of 55 patients (89%), while the remaining six have split chimerism ranging from 34 to 98%. There is significant difference (P=0.0004) between the percentages of donor DNA in all three cellular compartments comparing the means+/-s.e.m. (myeloid 95.60+/-0.9, T-cell lymphocytes 87.6+/-1.9, and the platelets 90.8+/-1.5); however, comparison between the medians is not statistically significant. This study represents an additional step towards achieving full chimerism and the observation may help reduce the number of unnecessary platelet transfusions once chimerism is noted in that cellular compartment.

The expression of WT1 in the differentiation of rhabdomyosarcoma from other pediatric small round blue cell tumors.

The WT1 gene encodes a transcription factor implicated in normal and neoplastic development. The purpose of this study was to evaluate the diagnostic utility of a commercial WT1 antibody on a variety of pediatric small round blue cell tumors (SRBCT). A mouse monoclonal antibody (clone: 6F-H2, DAKO) raised against the N-terminal amino acids 1-181 of the human WT1 protein was tested. Microscopic sections from 66 specimens were stained using an antigen retrieval protocol with trypsin. The tumors included peripheral neuroectodermal tumors (PNET/Ewing's), neuroblastomas, desmoplastic small round cell tumors (DSRCT), lymphomas, Wilms' tumors, and rhabdomyosarcomas (RMS). One RMS case was investigated by Western blot analysis and RT-PCR to confirm the antibody specificity. A strong cytoplasmic staining was demonstrated in all RMS (11/11). The Western blot analysis confirmed the WT1 protein in the tissue, and the RT-PCR confirmed the presence of WT1 mRNA in the peripheral blood and tissue of one RMS patient. The Wilms' tumors had a variable nuclear and/or cytoplasmic positivity in most (17/24) cases. All PNET/Ewing's were negative. The nuclei of two lymphoblastic lymphomas stained strongly. A weak nuclear or cytoplasmic staining was reported in a few DSRCT (3/5), lymphomas (2/10), and neuroblastomas (2/8). This is a useful antibody in the differentiation of RMS from other SRBCTs. A strong cytoplasmic staining favors an RMS, and a strong nuclear staining is suggestive of a Wilms' tumor. A role for WT1 in the pathogenesis of rhabdomyosarcomas is raised. The limited sampling precludes any conclusions regarding the value of tissue or peripheral blood analysis for WT1 mRNA in patients with rhabdomyosarcoma.

Calcifying fibrous pseudotumor versus inflammatory myofibroblastic tumor: a histological and immunohistochemical comparison.

Calcifying fibrous pseudotumor (CFP), a recently described lesion, is characterized by a predominantly lymphoplasmacytic infiltrate with abundant hyalinized collagen and psammomatous or dystrophic calcifications. The cause and pathogenesis are unclear, but it has been postulated that CFP may represent a sclerosing end stage of inflammatory myofibroblastic tumor (IMT). We compared the histological and immunohistochemical profiles of seven cases diagnosed as CFP and seven as IMT. Histologically, the CFP demonstrated varying degrees of calcifications in addition to fibroblastic proliferation admixed with inflammatory cells composed of lymphocytes, eosinophils, and mast cells. The IMTs rarely contain calcifications and had a myofibroblastic proliferation varying from hyalinized acellular collagen to florid fibroblastic proliferations simulating sarcoma. The inflammatory component was composed primarily of plasma cells and lymphocytes, sometimes arranged as lymphoid aggregates with germinal centers. All CFP cases were diffusely positive for factor XIIIa and negative for smooth muscle actin, muscle-specific actin, and CD34. All IMTs demonstrated diffuse positivity for actin, variable positivity for CD34, and focal positivity for Factor XIIIa. This study demonstrates certain distinct histologic, immunohistochemical, and electron microscopic features between IMTs and CFPs.

Factors secreted by human neuroblastoma mediated doxorubicin resistance by activating STAT3 and inhibiting apoptosis.

BACKGROUND: The transcription factor Stat3 has been reported to play a key role in protecting cells against apoptosis by up-regulating expression of the anti-apoptotic gene BCl-xL. This investigation analyzes the relationship between the development of resistance to doxorubicin-mediated apoptosis in neuroblastoma cells (SKN-SH) and activation of the Stat3 signaling pathway. MATERIALS AND METHODS: A drug-resistant cell line (SKN-SH/Dox6) was generated by continuous exposure to incremental concentrations of doxorubicin. Specific antibodies were utilized for Western blots and confocal microscopy to determine the nuclear localization of activated Stat3. RESULTS: Doxorubicin-mediated DNA fragmentation was inhibited and caspase-3 activity decreased in SKN-SH/Dox6 cells. Up-regulation of Stat3 phosphorylation and Bcl-xL expression, increased nuclear translocation of phospho-Stat3, and binding to DNA occurred only in resistant SKN-SH/Dox6 cells. The expression of Bcl-xL was inhibited by AG490, an inhibitor of the JAK/Stat3 signaling pathway, suggesting that the regulation of Bcl-xL and Stat3 involved a common mechanism. Activation of Stat3 in SKN-SH/Dox6 cells was contingent upon stimulation evoked by ligands secreted by the drug-resistant cells. Evidence to support this hypothesis was provided by experiments in which doxorubicin-sensitive SKN-SH cells were preincubated with conditioned media obtained from doxorubicin-resistant SKN-SH/Dox6 cells. This treatment increased Stat3 activation. It also rendered SKN-SH cells resistant to doxorubicin as demonstrated by a sharp decrease in doxorubicin-induced DNA degradation and cytotoxic potency. CONCLUSIONS: These findings suggest that the resistance of SKN-SH/Dox6 cells to doxorubicin may be mediated by anti-apoptotic factor(s) that are synthesized and secreted by tumor cells in response to cytotoxic agents.

Lamina muscularis propria thickness of renal pelvis predicts radiological outcome of surgical correction of ureteropelvic junction obstruction.

PURPOSE: We examine if there is a relationship between the histopathology of the renal pelvis and postoperative radiological findings in children with ureteropelvic junction obstruction. MATERIALS AND METHODS: The records of 220 patients who underwent pyeloplasty for isolated ureteropelvic junction obstruction between 1988 and 1996 were retrospectively reviewed, and 41 (42 kidneys) were identified who had adequate histological specimens and postoperative radiographic studies (ultrasonography and/or well tempered renogram) for examination. Histological features of the lamina muscularis propria from the renal pelvis were correlated with the radiographic outcome after pyeloplasty. RESULTS: Lamina muscularis propria thickness of the renal pelvis correlated significantly with radiological improvement. All kidneys with renal pelvic lamina muscularis propria thickness less than 250 microm. showed radiological improvement at 3 to 6 months postoperatively, those with thickness between 250 and 350 microm. had improvement at 9 months and those with lamina thickness greater than 350 microm. had a significantly worse outcome at all observation points. At 3 and 6 months postoperatively 16 of 30 (53%) and 23 of 34 (68%) children with radiological improvement had a mean lamina muscularis propria thickness of 252 +/- 131.5 microm. and 263 +/- 122.8 microm., respectively, while the remaining unimproved 14 and 12 patients had a mean thickness of 374 +/- 64.3 microm. (p <0.01) 372 +/- 66.1 microm. (p <0.05), respectively. CONCLUSIONS: The lamina muscularis propria thickness of the renal pelvic wall can provide insight to the expected time of postoperative improvement on radiological studies in children with ureteropelvic junction obstruction.

Doxorubicin-induced apoptosis in caspase-8-deficient neuroblastoma cells is mediated through direct action on mitochondria.

UNLABELLED: The induction of p53 expression and stimulation of the Fas/caspase-8 pathway represent major mechanisms by which cytotoxic drugs induce apoptosis, but in neuroblastomas, the caspase-8 gene is often not expressed. PURPOSE: The aim of this study was to determine whether doxorubicin could induce apoptosis in caspase-8-deficient neuroblastoma cells and to define its mechanism of action. METHODS: The caspase-8-deficient human neuroblastoma cell line, SKN-SH, was incubated with doxorubicin and the apoptotic response, as well as expression of apoptotic molecules in the p53/ Fas/caspase-8 pathway, were determined. RESULTS: SKN-SH cells incubated with doxorubicin readily underwent apoptosis in a concentration-dependent manner. Western blot analyses with specific antibodies demonstrated that both p53 and Fas ligand were endogenously expressed in SKN-SH cells, but their expression was not stimulated by doxorubicin. Fas receptor was not detected in these cells and caspase-8 was totally absent. Electron microscopic analyses of SKN-SH cells treated with doxorubicin revealed pronounced alterations in mitochondrial structure. This treatment also induced the release of cytochrome c from mitochondria and activated the downstream apoptotic intermediate, caspase-3. CONCLUSION: These results indicate that the p53/Fas/caspase-8 system does not play a role in mediating the apoptotic action of doxorubicin in the human neuroblastoma cell line SKN-SH. Thus, mitochondria and downstream apoptotic signaling intermediates may be considered as key targets for doxorubicin-induced apoptosis in neuroblastoma tumors having deficiencies in the Fas/caspase-8 system.

Schwann cell-conditioned medium inhibits angiogenesis in vitro and in vivo.

BACKGROUND: Neuroblastomas are biologically heterogeneous tumors that consist of two main cell populations: neuroblastic/ganglionic cells and Schwann cells. The amount of Schwannian stroma strongly impacts prognosis. Low tumor vascularity, localized stage, and favorable outcome are associated with tumors that are Schwannian stroma-rich/stroma-dominant. PROCEDURE: To investigate if Schwann cells play a role in inhibiting angiogenesis in neuroblastoma tumors, we examined the ability of human Schwann cell-conditioned medium to affect bFGF- and VEGF-induced endothelial cell proliferation and migration, and in vivo angiogenesis. RESULTS: Schwann cell-conditioned medium significantly inhibited bFGF- and VEGF-induced endothelial cell proliferation and migration. This effect appears to be specific for endothelial cells as smooth muscle cell and fibroblast proliferation were not inhibited by this medium. Schwann cell-conditioned medium also inhibited in vivo angiogenesis in rat corneal assays. CONCLUSIONS: Schwann cells produce a potent inhibitor(s) of angiogenesis that may be responsible for the low level of vascularity and more benign clinical behavior of Schwannian stroma-rich/stroma-dominant neuroblastoma tumors. Studies to identify the inhibitor(s) are ongoing.

Schwann cell-conditioned medium inhibits angiogenesis.

Neuroblastomas are biologically heterogeneous tumors that consist of two main cell populations: neuroblastic/ganglionic cells and Schwann cells. The amount of Schwannian stroma strongly impacts prognosis, and favorable outcome is associated with tumors that are Schwannian stroma rich/stroma dominant. At the present time, there is controversy regarding the origin of Schwann cells in neuroblastoma tumors. However, recent studies have suggested that the Schwann cells in mature neuroblastoma tumors may be normal cells that produce soluble substances that enhance the survival and differentiation of neuroblastoma cell lines. Previously, we reported that in neuroblastoma, high vascular index correlated with clinically aggressive disease. In contrast, tumors with favorable histology and abundant Schwannian stroma had low tumor vascularity. As a first step toward investigating whether Schwann cells also play a role in inhibiting angiogenesis in neuroblastoma tumors, we examined the ability of conditioned medium collected from normal human Schwann cells to affect basic fibroblast growth factor- and vascular endothelial growth factor-induced endothelial cell proliferation and migration and in vivo angiogenesis. In vitro angiogenesis assays were also performed with conditioned medium collected from Schwann cells derived from a Schwannian stroma-dominant neuroblastoma tumor. Our results indicate that Schwann cells derived from either adult nerve or tumor tissue produce a potent inhibitor(s) of angiogenesis. Expression studies revealed tissue inhibitor of metalloproteinase (TIMP)-2 in conditioned medium collected from both normal and tumor-derived Schwann cells. In addition, TIMP-2 was detected in the cytoplasm of Schwann cells and ganglion cells in stroma-rich/stroma-dominant neuroblastoma tumors by immunohistochemistry studies. We postulate that the low level of vascularity and more benign clinical behavior of Schwannian stroma-rich/stroma-dominant neuroblastoma tumors result from the Schwann cell production of TIMP-2 and/or other inhibitors of angiogenesis.

Fibrous tumors in children - a morphologic and interphase cytogenetic analysis of problematic cases.

We describe and discuss the findings by fluorescent in situ hybridization (FISH) for detection of non-random chromosomal gains, in a group of unusual fibrous lesions in children. Nuclear disaggregation was used to prepare slides from eight cases which were hybridized using alpha-satellite enumeration probes for chromosomes 8, 11 and 17. Trisomy 8 and 11 were detected in a high percentage of nuclei in cases of congenital/infantile fibrosarcomas (ranging from 45 to 80%), and in a low grade fibrosarcoma in an older child (23%). Only gains of chromosome 17 were detected in a case of infantile fibromatosis (22%). In this study we have found that given the unconventional histopathologic features, the detection of more than one non-random chromosomal gains by FISH, may aid in further defining fibrous tumors in children, and may be useful as an ancillary diagnostic test in the future.

Calcifying fibrous pseudotumor involving the neck of a five-week-old infant. Presence of factor XIIIa in the lesional cells.

Calcifying fibrous pseudotumor is an uncommon lesion characterized by hyalinized collagen, psammomatous or dystrophic calcifications, and a predominantly lymphoplasmacytic infiltrate. Although the pathogenesis is unclear, a possible relationship with other inflammatory "pseudotumors" has been proposed. We describe the pathology of two right neck calcifying fibrous pseudotumors present in a five-week-old female infant. The masses had many of the pathologic features of calcifying fibrous pseudotumor. The presence of a florid, mixed infiltrate, and the occurrence of more than one lesion in the same patient, favor the proposal that calcifying fibrous pseudotumor may be a sclerosing end stage of inflammatory myofibroblastic tumor. However, the presence of a previously undescribed participation of Factor XIIIa-positive cells suggests that the tumor may be of dermal dendrocyte origin.

Expression of bisecting GlcNAc in pediatric brain tumors and its association with tumor cell response to vinblastine.

Increased expression of the bisecting GlcNAc has been correlated with tumor progression in several experimental tumor models. Its expression and function in brain tumors are, however, not yet known. In this study, we investigated expression of the bisecting GlcNAc structure in a series of pediatric brain tumors and its relationship to tumor response to vinblastine. A plant lectin (E-PHA) that recognizes the bisecting GlcNAc structure was used for detection of this molecule in a total of 90 pediatric brain tumors and normal brain tissue specimens. Our results showed that, whereas E-PHA staining was undetectable in the normal brain tissue, pediatric brain tumor specimens exhibited different levels of reactivity. Lectin staining was particularly prominent in high-grade astrocytomas (73%) and ependymomas (72%). In astrocytomas, there was a positive correlation with the tumor grade, which suggests that the bisecting GlcNAc may be of particular interest as a tumor marker for diagnosis and/or prognosis. By using a human glioma cell culture model, we have found that treatment of these cells with E-PHA lectin enhances their sensitivity to vinblastine. E-PHA interacted directly with the drug transporter P-glycoprotein and inhibited its drug efflux function. In a drug-resistant glioma cell line transfected with the mdr1 gene, drug resistance was reversed by E-PHA. Our findings indicate that: (a) expression of the bisecting GlcNAc in pediatric brain tumors may have a potential relevance as a tumor marker; and (b) glioma response to chemotherapy may be modulated through the bisecting GlcNAc.

Indeterminate-cell histiocytosis: immunophenotypic and cytogenetic findings in an infant.

BACKGROUND: The authors report the immunohistochemical, ultrastructural, and cytogenetic findings in a case of malignant histiocytic proliferation in an infant. PROCEDURE: The patient presented initially with bone lesions without skin or systemic involvement. Multiple biopsies were studied extensively by immunohistochemistry and electron microscopy. Cytogenetic studies of cell cultures supplemented with granulocyte-monocyte colony stimulating factor (GM-CSF) were also performed. RESULTS: Morphologically, the cells resembled Langerhans cells, although with greater pleomorphism, as evinced by cells with usual polylobated nuclei. These cells expressed markers for macrophages and antigen presenting cells and were CD1a- and S-100-positive, but lacked Birbeck granules. The cells grown in culture supplemented with GM-CSF showed a unique combination of numerical and structural abnormalities affecting chromosomes 1, 6, 8, and 10. The disease followed a malignant course leading to the patient's demise despite aggressive chemotherapy and bone marrow transplant. CONCLUSIONS: The findings suggest a malignant hematopoietic stem-cell neoplasm with a capacity for macrophage or dendritic-cell differentiation. Morphology and immunophenotypic features place this neoplasm within the group recently conceptualized as indeterminate-cell histiocytosis.

Clonal cytogenetic abnormalities in pediatric brain tumors: cytogenetic analysis and clinical correlation.

The use of contemporary techniques in genetics has resulted in identifying a number of recurring abnormalities in pediatric brain tumors. This information has potential significance in the diagnosis and subtyping of these tumors. Although recurring genetic alterations have been identified in specific tumor types, there are some indications that pediatric brain tumors may be different cytogenetically from adult tumors. In addition, cytogenetic aberrations in certain tumors are associated with unfavorable outcome. In this report we present the cytogenetic characteristics of 14 brain tumors. The clinical outcome is correlated with cytogenetic abnormalities. Clonal abnormalities were observed in 6 of 14 (43%) tumors. All 7 cases had abnormalities specific to histologic subtype. Five of 6 cases with clonal abnormalities (83%) and 2 of 8 with a normal karyotype (25%) were observed in patients with poor prognosis. We also describe the cytogenetic aberrations associated with progression in a rare pediatric brain tumor. This data suggests that cytogenetic analysis of pediatric brain tumors may not be entirely different from their adult counterpart and like the latter may be clinically relevant not only in diagnosis but also as a prognostic indicator.

Atypical Pneumocystis carinii pneumonia in a child with hyper-IgM syndrome.

Children with hyper-immunoglobulin M (hyper-IgM) syndrome are at increased risk for Pneumocystis carinii pneumonia (PCP), an opportunistic infection often found in immunodeficient hosts. PCP can present with increasing hypoxia, fever, cough, and respiratory distress. We describe a child with hyper-IgM syndrome in whom bronchoalveolar washings were negative for PCP. However, there was an atypical lung response in which caseating granulomas predominated. The histopathology, resembling that found in tuberculosis, stresses the importance of a high index of clinical suspicion and histologic confirmation for early intervention and treatment. Immunocompromised children with rapidly progressive pulmonary disease may require lung biopsy and stains such as GMS to identify PCP.

Gonadoblastoma: immunohistochemical localization of Müllerian-inhibiting substance, inhibin, WT-1, and p53.

Gonadoblastomas are rare tumors composed of both germ cells and sex-cord cells. In this study, we investigated two such tumors for the expression of the Wilms' tumor gene (WT1), which has a key role in urogenital development, and the expression of markers associated with sex-cord differentiation, i.e., Müllerian-inhibiting substance (MIS) and inhibin (I). We also studied p53 expression. Archival, paraffin-embedded tissue from two patients with gonadoblastoma, one bilateral and both with concurrent germinomatous areas, were evaluated immunohistochemically with antibodies directed against I, MIS, WT1, and p53. I was noted in the sex-cord component of the gonadoblastoma and not in germinoma cells. MIS was noted in both, although it was more strongly expressed in the sex-cord component. p53 expression was noted in the germ cells of the gonadoblastoma, as well as in the frankly germinomatous areas, whereas WT1 was found only in the sex-cord region and not at all in the germ cells of either of our two cases. These findings lead us to propose that WT1 and I are present in the initiation of gonadoblastomas, but are lost with the progression of these tumors. Similarly, MIS may be involved in its tumorigenesis. The expression of p53 seems to support the concept that gonadoblastoma represents in situ germ cell neoplasia with malignant potential. Additional studies, however, are needed to validate this concept.

Differential expression of p53, c-kit, and CD34 in prepubertal and postpubertal testicular germ cell tumors.

BACKGROUND: The origin of testicular germ cell tumors (TGCTs) in children is poorly understood. There are clear differences between tumors in young children and those in adolescents and adults, which may suggest that they follow different pathways of tumorigenesis. METHODS: Tissue sections from 25 TGCTs (15 from patients age 4 years or younger and 10 from adolescents or adults) were stained immunohistochemically with anti-p53 (DO-1), CD34, and c-kit proto-oncogene protein product. RESULTS: CD34 expression was noted only in 5 prepubertal tumors. Expression of c-kit was observed in 9 of the 15 prepubertal tumors versus 2 of the 10 postpubertal cases. The intensity of expression was equal to that of the adjacent normal tubules in the prepubertal tumors, whereas the intensity was less in the postpubertal tumors. Expression of p53 was strong in 8 of the 10 tumors in adolescents or adults, with a 40-70% positivity, whereas only 6 of 15 prepubertal tumors expressed p53, with < 10% positivity. CONCLUSIONS: CD34 expression in tumors in the group of young children suggests a possible link to teratomas and further provides insight into the fundamental differences between this group and the adolescent/adult group. The expression of c-kit and p53 provides further evidence that c-kit/SCF signaling and p53 play potentially different roles in the initiation and progression of these tumors. Future studies will be required to clarify this issue.

Ependymomas in children express the multidrug resistance gene: immunohistochemical and molecular biologic study.

In view of the poor response of ependymomas to chemotherapy, it may be hypothesized that these tumors have intrinsic drug resistance to some chemotherapeutic agents. The expression of drug resistance may be specific to a single agent or may involve multiple drugs. Among several mechanisms of drug resistance, P-glycoprotein (Pgp) has been the subject of considerable attention in clinical practice. In order to assess the possible participation of Pgp in the chemotherapeutic resistance of ependymomas, 42 biopsy specimens from 35 patients with ependymoma seen at our institutions were studied by immunohistochemistry with two monoclonal antibodies: C219 (Signet) and UIC-2 (Dr. Roninson's gift). In addition, four cases were studied by polymerase chain reaction after reverse transcription to detect transcripts of Pgp. Our results showed that in 35 samples there was a positive reaction for Pgp with both antibodies; two biopsy samples were positive only with C219 and three others with UIC-2; the remaining two samples were negative with both antibodies. Of the four cases studied by RT-PCR, three showed MDR1 transcripts. These results support our hypothesis of Pgp-mediated intrinsic multidrug resistance in these tumors.

Multidrug resistance gene expression in childhood medulloblastoma: correlation with clinical outcome and DNA ploidy in 29 patients.

Twenty-nine children treated for medulloblastoma between 1987 and 1991 were reviewed. Thirteen patients with high-risk medulloblastoma characterized by incomplete resection, diploid tumor or subarachnoid dissemination received chemotherapy following radiation therapy. Three received postoperative chemotherapy. Eight patients who had been treated with postoperative radiation therapy also received chemotherapy for recurrent tumors. After a minimum 3-year follow-up period, 16 were alive but 13 had died from recurrent tumors. In order to evaluate the possible participation of P-glycoprotein (Pgp)-mediated multidrug resistance (MDR) in medulloblastoma therapy and its correlation with prognosis, archival specimens were examined by immuno-histochemistry utilizing 3 monoclonal antibodies against Pgp and 6 cases by reverse-transcriptase polymerase chain reaction (RT-PCR) using MDR1-specific primers. Sixteen patients (55%) had MDR expression detected either by 1 of the 3 antibodies or by RT-PCR. DNA ploidy study was also performed on 18 specimens. We correlated patients' outcome with variable factors (extent of surgical resection, chemotherapy, DNA ploidy) and MDR expression. Patients who were treated with radiation therapy and adjuvant chemotherapy had a significantly better (p = 0.036) survival than those with radiation therapy alone, despite the fact that the former group of patients was considered to be high-risk. The extent of surgical resection and DNA ploidy did not correlate with prognosis. However, a statistically significant association was found between MDR expression and outcome (p = 0.007). Among the patients who received chemotherapy, positive MDR expression significantly correlated with poor outcome (p = 0.036). Our results showed that Pgp-mediated intrinsic MDR in medulloblastomas seems to correlate with an adverse outcome. This information may be used in designing new therapeutic protocols for medulloblastoma.