Single-cell transcriptional profiling identifies a cluster of potential metastasis-associated UBE2C+ cells in immature ovarian teratoma.

To dissect the disease heterogeneity and identify the underlying cellular and molecular events related to metastasis of immature ovarian teratoma in children, single-cell RNA sequencing was performed for a 2-year-old patient with liver metastases from immature ovarian teratoma. A total of 5976 cells were obtained for further analysis, with a median unique molecular identifier count of 6011 per cell and a median number of 1741 genes detected per cell. Fourteen clusters were recognized, with the main lineages comprising epithelial cells, macrophages, fibroblasts, glial cells, and dendritic cells. Ten subclusters of epithelial cells were further defined, originating from the urinary tract, esophagus, bronchus, lung, skin, and gastrointestinal tract. An undefined UBE2C + population in an active state of proliferation was also identified and its biological processes were related to meiosis and maturation of oocytes. Pseudotime analysis revealed different distributions of epithelial cells in the development trajectory. In conclusion, a cluster of UBE2C + epithelial cells in an active state of proliferation was identified in an immature ovarian teratoma in a child, and may contribute to metastasis by regulating epithelial-mesenchymal transition. These findings help toward understanding the origin of the malignant behaviors, offer a potential biomarker for early determination of the tumor nature, and provide new ideas for the therapy of immature ovarian teratoma in children.

MEK Inhibition Suppresses Growth of Atypical Teratoid/Rhabdoid Tumors.

Atypical teratoid/rhabdoid (AT/RT) tumors are the most common malignant brain tumor of infancy and have a poor prognosis. We have previously identified very high expression of LIN28A and/or LIN28B in AT/RT tumors and showed that AT/RT have corresponding increased expression of the mitogen-activated protein (MAP) kinase pathway. Binimetinib is a novel inhibitor of mitogen-activated protein kinase (MAP2K1 or MEK), and is currently in pediatric phase II clinical trials for low-grade glioma. We hypothesized that binimetinib would inhibit growth of AT/RT cells by suppressing the MAP kinase pathway. Binimetinib inhibited AT/RT growth at nanomolar concentrations. Binimetinib decreased cell proliferation and induced apoptosis in AT/RT cells and significantly reduced AT/RT tumor growth in flank xenografts. Our data suggest that MAP kinase pathway inhibition could offer a potential avenue for treating these highly aggressive tumors.

Pten-mediated Gsk3ß modulates the naïve pluripotency maintenance in embryonic stem cells.

Mouse embryonic stem cells (ESCs) are isolated from the inner cell mass of blastocysts, and they exist in different states of pluripotency-naïve and primed states. Pten is a well-known tumor suppressor. Here, we generated Pten-/- mouse ESCs with the CRISPR-Cas9 system and verified that Pten-/- ESCs maintained naïve pluripotency by blocking Gsk3ß activity. Serum/LIF and 2i (MAPK and GSK3 inhibitors) conditions are commonly used for ESC maintenance. We show that the Pten-inhibitor SF1670 contributed to sustaining mouse ESCs and that Pten activation by the S380A, T382A, and T383A mutations (Pten-A3) suppressed the pluripotency of ESCs. The in vivo teratoma formation ability of SF1670-treated ESCs increased, while the Pten-A3 mutations suppressed teratoma formation. Furthermore, the embryoid bodies derived from Pten-deficient ESCs or SF1670-treated wild-type ESCs showed greater expression of ectoderm and pluripotency markers. These results suggest that Pten-mediated Gsk3ß modulates the naïve pluripotency of ESCs and that Pten ablation regulates the lineage-specific differentiation.

MEK/MELK inhibition and blood-brain barrier deficiencies in atypical teratoid/rhabdoid tumors.

BACKGROUND: Atypical teratoid/rhabdoid tumors (AT/RT) are rare, but highly aggressive. These entities are of embryonal origin occurring in the central nervous system (CNS) of young children. Molecularly these tumors are driven by a single hallmark mutation, resulting in inactivation of SMARCB1 or SMARCA4. Additionally, activation of the MAPK signaling axis and preclinical antitumor efficacy of its inhibition have been described in AT/RT. METHODS: We established and validated a patient-derived neurosphere culture and xenograft model of sonic hedgehog (SHH) subtype AT/RT, at diagnosis and relapse from the same patient. We set out to study the vascular phenotype of these tumors to evaluate the integrity of the blood-brain barrier (BBB) in AT/RT. We also used the model to study combined mitogen-activated protein kinase kinase (MEK) and maternal embryonic leucine zipper kinase (MELK) inhibition as a therapeutic strategy for AT/RT. RESULTS: We found MELK to be highly overexpressed in both patient samples of AT/RT and our primary cultures and xenografts. We identified a potent antitumor efficacy of the MELK inhibitor OTSSP167, as well as strong synergy with the MEK inhibitor trametinib, against primary AT/RT neurospheres. Additionally, vascular phenotyping of AT/RT patient material and xenografts revealed significant BBB aberrancies in these tumors. Finally, we show in vivo efficacy of the non-BBB penetrable drugs OTSSP167 and trametinib in AT/RT xenografts, demonstrating the therapeutic implications of the observed BBB deficiencies and validating MEK/MELK inhibition as a potential treatment. CONCLUSION: Altogether, we developed a combination treatment strategy for AT/RT based on MEK/MELK inhibition and identify therapeutically exploitable BBB deficiencies in these tumors.

Generation of four induced pluripotent stem cell lines, GZWWTi001-A, GZWTZi001-A, GZWXYi001-A, and GZWXDi001-A, derived from peripheral blood mononuclear cells from a family with asparagine synthetase deficiency.

Asparagine synthetase (ASNS) deficiency (ASNSD; MIM #615574) is a rare neurodevelopmental disorder caused by mutations in the ASNS gene. The ASNS gene maps to cytogenetic band 7q21.3 and is 35 kb long. ASNSD is characterised by congenital microcephaly, severely delayed psychomotor development, seizures, and hyperekplexic activity. Here, we reported a family with compound heterozygous mutations in ASNS (NM_001178076:c.551C>T; c. 944A>C) and established induced pluripotent stem cells (iPSCs) from blood samples. To date, limited functional data have been reported to explain the underlying pathophysiology of ASNSD; therefore, iPSCs from these patients may be powerful tools for studying disease mechanisms.

CHAC2 is essential for self-renewal and glutathione maintenance in human embryonic stem cells.

Glutathione (GSH), the major non-enzymatic antioxidant, plays a critical role in cellular reactive oxygen species (ROS) neutralization. Moreover, GSH is required for the self-renewal maintenance of human embryonic stem cells (hESCs), and is highly accumulated in undifferentiated cells. Among 8 GSH biosynthesis-related enzymes, we found CHAC2 is highly enriched in undifferentiated hESCs. CHAC2 downregulation in hESCs efficiently decreased the levels of GSH and blocked self-renewal. The self-renewal of sh-CHAC2 cells can be rescued by GSH supplement. CHAC2 downregulation promoted mesoderm differentiation and hampered both teratoma formation and the expression of Nrf2 and glutamate-cysteine ligase (GCL). Notably, CHAC1 knockdown restored the self-renewability of CHAC2-downregulated cells. Although both CHAC1 and CHAC2 purified protein alone showed the catalytic activities to GSH, our data extraordinarily revealed that CHAC2 prevented CHAC1-mediated GSH degradation, which suggests that CHAC2 competes with CHAC1 to maintain GSH homeostasis. This is the first report to demonstrate that CHAC2 is critical for GSH maintenance and the novel roles of the CHAC family in hESC renewal.

Virilism and Ectopic Expression of HSD17B5 in Mature Cystic Teratoma.

Mature cystic teratoma (MCT) is rarely involved in the overproduction of steroid hormones in contrast to sex cord stromal tumors. A 31-year-old woman visited our hospital with hirsutism, hoarseness, and hair loss from the scalp. Serum testosterone and free-testosterone levels were 7.3 ng/ml and 2.3 pg/ml, respectively, which were markedly in excess of the age adjusted female standard levels. Basal blood levels of steroid hormones and serum levels of 17-hydroxyprogesterone at 1 h after intravenous injection of adrenocorticotropic hormone demonstrated that 21-hydroxylase deficiency was not the underlying cause of her virilization. A subsequent chromosomal test with G-banding revealed a karyotype of 46XX. Magnetic resonance imaging revealed a mass in the left ovary, which was subsequently diagnosed as MCT. Detailed pathological analysis of the tumor indicated that it was comprised of skin components, sweat glands, with hair and fat texture, glandular epithelium and fibrous connective tissue, consistent with the characteristic composition of MCT. Immunohistochemical analysis demonstrated marked immunoreactivity of 17beta-hydroxysteroid dehydrogenase (HSD17B5), an enzyme that can convert androstenedione to testosterone. Following surgical removal of the tumor, testosterone and free testosterone levels were markedly decreased (0.3 ng/ml and 0.4 pg/ml, respectively) and other symptoms abated. In conclusion, this is the first report of an ovarian MCT associated with clinical virilization caused by the ectopic production of testosterone possibly because of an overexpression of intratumoral HSD17B5.

Can pancreatic tissue cause haemoptysis?

A mature teratoma is a tumour of primary germ cells. It is often found in the mediastinum. The authors describe a case of a young man who demonstrated haemoptysis as the only symptom of a mediastinal tumour. The tumour was removed operatively, sent for histopathological examination and immunohistochemistry. The removed tumour was a mature teratoma including elements of the pancreas. The authors revealed the presence of trypsin in the pancreatic acinar cells. The proteolytic activity of the tumour was taken as the cause of haemoptysis because of enzymatic erosion of lung tissue intimately attached to the tumour. In such cases surgical removal saves life of patients.

Inhibition of DNA damage repair by the CDK4/6 inhibitor palbociclib delays irradiated intracranial atypical teratoid rhabdoid tumor and glioblastoma xenograft regrowth.

BACKGROUND: Radiation therapy is the most commonly used postsurgical treatment for primary malignant brain tumors. Consequently, investigating the efficacy of chemotherapeutics combined with radiation for treating malignant brain tumors is of high clinical relevance. In this study, we examined the cyclin-dependent kinase 4/6 inhibitor palbociclib, when used in combination with radiation for treating human atypical teratoid rhabdoid tumor (ATRT) as well as glioblastoma (GBM). METHODS: Evaluation of treatment antitumor activity in vitro was based upon results from cell proliferation assays, clonogenicity assays, flow cytometry, and immunocytochemistry for DNA double-strand break repair. Interpretation of treatment antitumor activity in vivo was based upon bioluminescence imaging, animal subject survival analysis, and staining of tumor sections for markers of proliferation and apoptosis. RESULTS: For each of the retinoblastoma protein (RB)-proficient tumor models examined (2 ATRTs and 2 GBMs), one or more of the combination therapy regimens significantly (P < .05) outperformed both monotherapies with respect to animal subject survival benefit. Among the combination therapy regimens, concurrent palbociclib and radiation treatment and palbociclib treatment following radiation consistently outperformed the sequence in which radiation followed palbociclib treatment. In vitro investigation revealed that the concurrent use of palbociclib with radiation, as well as palbociclib following radiation, inhibited DNA double-strand break repair and promoted increased tumor cell apoptosis. CONCLUSIONS: Our results support further investigation and possible clinical translation of palbociclib as an adjuvant to radiation therapy for patients with malignant brain tumors that retain RB expression.

DNA methyltransferase-3 like protein expression in various histological types of testicular germ cell tumor.

OBJECTIVE: DNA methyltransferase 3-like plays an important role in germ cell development. The aim of this study was to analyse the DNA methyltransferase 3-like protein expression in testicular germ cell tumors. METHODS: The immunohistochemical expression of DNA methyltransferase 3-like was examined in 86 testicular germ cell tumor specimens in various clinical settings. The association between DNA methyltransferase 3-like expression and disease stage was analyzed. RESULTS: DNA methyltransferase 3-like was strongly expressed in seven of the eight pure embryonal carcinomas (87.5%). Partial DNA methyltransferase 3-like expression was observed in 6 of 23 (26.1%) pure seminomas. Various degrees of DNA methyltransferase 3-like expression was observed in all four pure yolk sac tumors, of which three were prepubertal yolk sac tumors. In mixed germ cell tumors, DNA methyltransferase 3-like protein was expressed in various degrees in elements of the embryonal carcinoma (14/18, 77.8%), seminoma (4/11, 36.4%), teratoma (4/7, 57.1%) and choriocarcinoma (3/3, 100%) but not in the yolk sac tumors (0/4). When DNA methyltransferase 3-like expression was analyzed according to disease stages, it was significantly correlated with advanced seminoma rather than Stage I seminoma (46.2 vs. 0%, P = 0.019), whereas there was no significant difference in the DNA methyltransferase 3-like-positive proportion between Stage I and advanced disease in the mixed germ cell tumors. CONCLUSIONS: Our findings suggest that DNA methyltransferase 3-like protein may play roles not only in the development of embryonal carcinoma but also in the development of advanced pure seminoma and pure yolk sac tumor.

The histone deacetylase SIRT6 controls embryonic stem cell fate via TET-mediated production of 5-hydroxymethylcytosine.

How embryonic stem cells (ESCs) commit to specific cell lineages and yield all cell types of a fully formed organism remains a major question. ESC differentiation is accompanied by large-scale histone and DNA modifications, but the relations between these epigenetic categories are not understood. Here we demonstrate the interplay between the histone deacetylase sirtuin 6 (SIRT6) and the ten-eleven translocation enzymes (TETs). SIRT6 targets acetylated histone H3 at Lys 9 and 56 (H3K9ac and H3K56ac), while TETs convert 5-methylcytosine into 5-hydroxymethylcytosine (5hmC). ESCs derived from Sirt6 knockout (S6KO) mice are skewed towards neuroectoderm development. This phenotype involves derepression of OCT4, SOX2 and NANOG, which causes an upregulation of TET-dependent production of 5hmC. Genome-wide analysis revealed neural genes marked with 5hmC in S6KO ESCs, thereby implicating TET enzymes in the neuroectoderm-skewed differentiation phenotype. We demonstrate that SIRT6 functions as a chromatin regulator safeguarding the balance between pluripotency and differentiation through Tet-mediated production of 5hmC.

Disrupting LIN28 in atypical teratoid rhabdoid tumors reveals the importance of the mitogen activated protein kinase pathway as a therapeutic target.

Atypical teratoid rhabdoid tumor (AT/RT) is among the most fatal of all pediatric brain tumors. Aside from loss of function mutations in the SMARCB1 (BAF47/INI1/SNF5) chromatin remodeling gene, little is known of other molecular drivers of AT/RT. LIN28A and LIN28B are stem cell factors that regulate thousands of RNAs and are expressed in aggressive cancers. We identified high-levels of LIN28A and LIN28B in AT/RT primary tumors and cell lines, with corresponding low levels of the LIN28-regulated microRNAs of the let-7 family. Knockdown of LIN28A by lentiviral shRNA in the AT/RT cell lines CHLA-06-ATRT and BT37 inhibited growth, cell proliferation and colony formation and induced apoptosis. Suppression of LIN28A in orthotopic xenograft models led to a more than doubling of median survival compared to empty vector controls (48 vs 115 days). LIN28A knockdown led to increased expression of let-7b and let-7g microRNAs and a down-regulation of KRAS mRNA. AT/RT primary tumors expressed increased mitogen activated protein (MAP) kinase pathway activity, and the MEK inhibitor selumetinib (AZD6244) decreased AT/RT growth and increased apoptosis. These data implicate LIN28/RAS/MAP kinase as key drivers of AT/RT tumorigenesis and indicate that targeting this pathway may be a therapeutic option in this aggressive pediatric malignancy.

Telomerase reverse transcriptase has an extratelomeric function in somatic cell reprogramming.

Reactivation of the endogenous telomerase reverse transcriptase (TERT) catalytic subunit and telomere elongation occur during the reprogramming of somatic cells to induced pluripotent stem (iPS) cells. However, the role of TERT in the reprogramming process is unclear. To clarify its function, the reprogramming process was examined in TERT-KO somatic cells. To exclude the effect of telomere elongation, tail-tip fibroblasts (TTFs) from first generation TERT-KO mice were used. Although iPS cells were successfully generated from TERT-KO TTFs, the efficiency of reprogramming these cells was markedly lower than that of WT TTFs. The gene expression profiles of iPS cells induced from TERT-KO TTFs were similar to those of WT iPS cells and ES cells, and TERT-KO iPS cells formed teratomas that differentiated into all three germ layers. These data indicate that TERT plays an extratelomeric role in the reprogramming process, but its function is dispensable. However, TERT-KO iPS cells showed transient defects in growth and teratoma formation during continuous growth. In addition, TERT-KO iPS cells developed chromosome fusions that accumulated with increasing passage numbers, consistent with the fact that TERT is essential for the maintenance of genome structure and stability in iPS cells. In a rescue experiment, an enzymatically inactive mutant of TERT (D702A) had a positive effect on somatic cell reprogramming of TERT-KO TTFs, which confirmed the extratelomeric role of TERT in this process.

PTEN regulates AMPA receptor-mediated cell viability in iPS-derived motor neurons.

Excitatory transmission in the brain is commonly mediated by the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors. In amyotrophic lateral sclerosis (ALS), AMPA receptors allow cytotoxic levels of calcium into neurons, contributing to motor neuron injury. We have previously shown that oculomotor neurons resistant to the disease process in ALS show reduced AMPA-mediated inward calcium currents compared with vulnerable spinal motor neurons. We have also shown that PTEN (phosphatase and tensin homolog deleted on chromosome 10) knockdown via siRNA promotes motor neuron survival in models of spinal muscular atrophy (SMA) and ALS. It has been reported that inhibition of PTEN attenuates the death of hippocampal neurons post injury by decreasing the effective translocation of the GluR2 subunit into the membrane. In addition, leptin can regulate AMPA receptor trafficking via PTEN inhibition. Thus, we speculate that manipulation of AMPA receptors by PTEN may represent a potential therapeutic strategy for neuroprotective intervention in ALS and other neurodegenerative disorders. To this end, the first step is to establish a fibroblast-iPS-motor neuron in vitro cell model to study AMPA receptor manipulation. Here we report that iPS-derived motor neurons from human fibroblasts express AMPA receptors. PTEN depletion decreases AMPA receptor expression and AMPA-mediated whole-cell currents, resulting in inhibition of AMPA-induced neuronal death in primary cultured and iPS-derived motor neurons. Taken together, our results imply that PTEN depletion may protect motor neurons by inhibition of excitatory transmission that represents a therapeutic strategy of potential benefit for the amelioration of excitotoxicity in ALS and other neurodegenerative disorders.

Telomerase-mediated telomere elongation from human blastocysts to embryonic stem cells.

High telomerase activity is a characteristic of human embryonic stem cells (hESCs), however, the regulation and maintenance of correct telomere length in hESCs is unclear. In this study we investigated telomere elongation in hESCs in vitro and found that telomeres lengthened from their derivation in blastocysts through early expansion, but stabilized at later passages. We report that the core unit of telomerase, hTERT, was highly expressed in hESCs in blastocysts and throughout long-term culture; furthermore, this was regulated in a Wnt-ß-catenin-signaling-dependent manner. Our observations that the alternative lengthening of telomeres (ALT) pathway was suppressed in hESCs and that hTERT knockdown partially inhibited telomere elongation, demonstrated that high telomerase activity was required for telomere elongation. We observed that chromatin modification through trimethylation of H3K9 and H4K20 at telomeric regions decreased during early culture. This was concurrent with telomere elongation, suggesting that epigenetic regulation of telomeric chromatin may influence telomerase function. By measuring telomere length in 96 hESC lines, we were able to establish that telomere length remained relatively stable at 12.02 ± 1.01 kb during later passages (15-95). In contrast, telomere length varied in hESCs with genomic instability and hESC-derived teratomas. In summary, we propose that correct, stable telomere length may serve as a potential biomarker for genetically stable hESCs.

Embryonic stem cells are redirected to non-tumorigenic epithelial cell fate by interaction with the mammary microenvironment.

Experiments were conducted to redirect mouse Embryonic Stem (ES) cells from a tumorigenic phenotype to a normal mammary epithelial phenotype in vivo. Mixing LacZ-labeled ES cells with normal mouse mammary epithelial cells at ratios of 1:5 and 1:50 in phosphate buffered saline and immediately inoculating them into epithelium-divested mammary fat pads of immune-compromised mice accomplished this. Our results indicate that tumorigenesis occurs only when normal mammary ductal growth is not achieved in the inoculated fat pads. When normal mammary gland growth occurs, we find ES cells (LacZ+) progeny interspersed with normal mammary cell progeny in the mammary epithelial structures. We demonstrate that these progeny, marked by LacZ expression, differentiate into multiple epithelial subtypes including steroid receptor positive luminal cells and myoepithelial cells indicating that the ES cells are capable of epithelial multipotency in this context but do not form teratomas. In addition, in secondary transplants, ES cell progeny proliferate, contribute apparently normal mammary progeny, maintain their multipotency and do not produce teratomas.

Histone deacetylases expression in atypical teratoid rhabdoid tumors.

PURPOSE: Atypical teratoid rhabdoid tumors (ATRTs) are rare, highly malignant central nervous system tumors that occur during infancy and early childhood. Their poor outcome and resistance to conventional chemotherapies and radiotherapy, urges the development of new therapies. Recent studies have evaluated the effects of histone deacetylase inhibitors (HDACi) as a new potential treatment for ATRTs. However, most HDACi act unselectively against all, or at least several, histone deacetylase (HDAC) family members. We hypothesized that specific HDAC family members are deregulated in ATRT and therefore a more selective class of HDACi would be beneficial to patients with ATRT. METHODS: To test our hypothesis, we evaluated the expression level of different HDAC family members in ATRTs. Eight ATRTs were compared to six medulloblastoma samples in regards to the level of expression of the 18 HDAC family members as determined by microarray gene expression profiling. RESULTS: HDAC1 was the only member of the HDAC family to be significantly differentially expressed in ATRTs (FC = 4.728; p value = 0.00003). CONCLUSIONS: A class of HDACi specifically targeting HDAC1 may allow for the desired therapeutic benefits with fewer side effects for children with ATRT.

Targeting Aurora Kinase A enhances radiation sensitivity of atypical teratoid rhabdoid tumor cells.

Atypical teratoid/rhabdoid tumors (ATRT) are rare, highly malignant, embryonal CNS tumors with a poor prognosis. Therapy relies on highly toxic chemotherapy and radiotherapy. To improve outcomes and decrease morbidity, more targeted therapy is required. Gene expression analysis revealed elevated expression of multiple kinases in ATRT tissues. Aurora Kinase A was one of the candidate kinases. The objective of this study was to evaluate the impact of Aurora Kinase A inhibition in ATRT cell lines. Our analysis revealed that inhibition of Aurora Kinase A induces cell death in ATRT cells and the small molecule inhibitor MLN 8237 sensitizes these cells to radiation. Furthermore, inhibition of Aurora Kinase A resulted in decreased activity of pro-proliferative signaling pathways. These data indicate that inhibition of Aurora Kinase A is a promising small molecule target for ATRT therapy.

Exacerbation of oxidative stress-induced cell death and differentiation in induced pluripotent stem cells lacking heme oxygenase-1.

Embryonic stem cells (ESCs) are promising donor sources in cell therapies for various diseases. Although low levels of reactive oxygen species (ROS) are necessary for the maintenance of stem cells, increased ROS levels initiate differentiation and cell damage. We and others have previously demonstrated that heme oxygenase (HO)-1, a stress response protein with antioxidative and anti-inflammatory properties, plays critical protective functions in cardiovascular and other diseases. However, the functions of HO-1 in ESCs remain to be elucidated. Our goal was to investigate the roles of HO-1 in ESC survival and differentiation. Due to the lack of HO-1-deficient ESCs, we used Oct3/4, Sox2, c-Myc, and Klf4 retroviruses to reprogram mouse embryonic fibroblasts into induced pluripotent stem (iPS) cells of different HO-1 genotypes. These iPS-HO-1 cells exhibited characteristics of mouse ESCs (mESCs) and formed teratomas that were composed of cell types of all 3 germ layers after injected into severe combined immunodeficiency mice. In response to oxidant stress, iPS-HO-1(-/-) cells accumulated higher levels of intracellular ROS compared with D3 mESCs or iPS-HO-1(+/+) cells and were more prone to oxidant-induced cell death. Spontaneous differentiation experiments revealed that Oct4 levels were significantly lower in iPS-HO-1(-/-) cells after leukemia inhibitory factor withdrawal and removal of feeders. Further, during the course of spontaneous differentiation, iPS-HO-1(-/-) cells had enhanced Erk1/2 phosphorylation, which has been linked to ESC differentiation. By the loss-of-function approach using iPS-HO-1(-/-) cells, our results demonstrate that a lack of HO-1 renders iPS cells more prone to oxidative stress-induced cell death and differentiation.

Immunohistochemical analyses of alpha1 and alpha3 Na+/K+-ATPase subunit expression in medulloblastomas.

BACKGROUND: The levels of expression of the α1 and α3 subunits of the Na(+)/K(+)-ATPase (the NaK sodium pump) in medulloblastomas are unclear. PATIENTS AND METHODS: This study investigated the expression of the NaK subunits using immunohistochemical methods in 29 medulloblastomas including 23 classic, three large-cell/anaplastic and three nodular/desmoplastic medulloblastomas, as well as in three atypical teratoid/rhabdoid tumors (AT/RTs). RESULTS: There was overexpression of the α1 or α3 NaK subunits in more than half of the medulloblastomas and atypical AT/RTs, with about one-third of these tumours displaying overexpression of both subunits. CONCLUSION: These preliminary data suggest that targeting these subunits in AT/RTs and medulloblastomas that overexpress these proteins may lead to therapeutic benefit. These findings warrant confirmation in larger numbers of patients than those used in this study. Moreover, it should be determined whether inhibition of the α1/α3 NaK subunits can be integrated into the risk stratification schemes already in use for medulloblastoma patients.