Some speculation on the origin of glioblastoma

Tenascin-C: a novel candidate marker for cancer stem cells in glioblastoma identified by tissue microarrays

Glioblastoma multiforme (GBM) is a highly aggressive brain tumor, with dismal survival outcomes. Recently, cancer stem cells (CSCs) have been demonstrated to play a role in therapeutic resistance and are considered to be the most likely cause of cancer relapse. The identification of CSCs is an important step toward finding new and effective ways to treat GBM. Tenascin-C (TNC) protein has been identified as a potential marker for CSCs in gliomas based on previous work. Here, we have investigated the expression of TNC in tissue microarrays including 17 GBMs, 18 WHO grade III astrocytomas, 15 WHO grade II astrocytomas, 4 WHO grade I astrocytomas, and 7 normal brain tissue samples by immunohistochemical staining. TNC expression was found to be highly associated with the grade of astrocytoma. It has a high expression level in most of the grade III astrocytomas and GBMs analyzed and a very low expression in most grade II astrocytomas, whereas it is undetectable in grade I astrocytomas and normal brain tissues. Double-immunofluorescence staining for TNC and CD133 in GBM tissues revealed that there was a high overlap between theses two positive populations. The results were further confirmed by flow cytometry analysis of TNC and CD133 in GBM-derived stem-like neurospheres in vitro. A limiting dilution assay demonstrated that the sphere formation ability of CD133⁺/TNC⁺ and CD133^–/TNC⁺ cell populations is much higher than that of the CD133⁺/TNC^– and CD133^–/TNC^– populations. These results suggest that TNC is not only a potential prognostic marker for GBM but also a potential marker for glioma CSCs, where the TNC⁺ population is identified as a CSC population overlapping with part of the CD133^– cell population.

Serine/threonine kinase, Melk, regulates proliferation and glial differentiation of retinal progenitor cells

Serine/threonine kinase, Melk, was initially cloned in oocytes, but it is expressed in normal tissues and especially in cancer cells. We had previously identified Melk as a gene that is highly expressed in immature mouse retinal progenitors. To analyze the function of Melk in embryogenesis, we cloned zebrafish Melk and reported that morpholino-based downregulation of Melk in zebrafish resulted in severe anemia. Melk-morpholino-treated zebrafish also showed microphthalmia, suggesting the participation of Melk in retinal development. In Melk-depleted retinas, differentiation of retinal neurons took place but was delayed, and the proliferative period of retinal progenitor cells was prolonged, suggesting that Melk might regulate the timing of the transition from proliferation to differentiation. For more detailed examination, we performed gain- and loss-of-function analyses of Melk in mouse retinas. Knockdown of Melk by shRNA in mouse embryonic retinal explant culture resulted in decreased proliferative activity of retinal progenitors, and accordingly, overexpression of Melk slightly enhanced proliferation. Differentiation of retinal progenitor into subtypes of retinal neurons was not significantly affected, but Müller glia differentiation was perturbed by the level of Melk. Furthermore, process extension of glial cells was enhanced in the absence of Melk, suggesting that Melk is involved in the morphological differentiation of retinal cells. Taken together, our results suggest that Melk is primarily required for proper proliferation, and might play multiple roles in retinal development in vertebrates.

The vasoactive intestinal peptide-receptor system is involved in human glioblastoma cell migration

Glioblastoma multiforme (GBM) is the most aggressive form of brain tumor in adults. This cancer has an infiltrative nature and the median survival of patients is about one year. Vasoactive intestinal peptide (VIP) belongs to a structurally related family of polypeptides and is a major regulatory factor in the central and peripheral nervous systems. VIP regulates proliferation of astrocytes and of numerous cancer cell lines and modulates migration in prostatic and colonic cancer cell lines. Little is known about the involvement of VIP and its receptors (VIP-receptor system) in proliferation or migration of GBM cells. The effects of VIP, PACAP and of synthetic VIP antagonists were tested in two human GBM cell lines, M059K and M059J, established from two different parts of a single tumor. In these cells, the data revealed that the VIP-receptor system did not affect proliferation but controlled cell migration. Indeed, in M059K cells which express components of the VIP receptor system, the VIP receptor antagonists and a PACAP antibody enhanced migration. The VIP receptor antagonists increased generation of typical migration-associated processes: filopodia and lamellipodia, and activation of Rac1 and Cdc42 GTPases. Reciprocally, in M059J cells which poorly express the VIP-receptor system, treatments with the agonists VIP and PACAP resulted in decreased cell migration. Furthermore, the peptides appeared to act through a subclass of binding sites displaying an uncommon very high affinity for these ligands. Taken together, these observations suggest that components of the VIP-receptor system negatively regulate cell migration, thus showing potential anti-oncogenic properties.

Glioblastoma multiforme in children: experience at Hospital Infantil de Mexico Federico Gomez

OBJECTIVE

To evaluate clinical evolution of pediatric patients diagnosed with glioblastoma multiforme (GBM) at Hospital Infantil de México Federico Gómez.

METHODS

Cases of patients treated from January to May, 2007, were included in this study. Variables analyzed were: age, diagnosis, size of tumor, histopathological description, degree of resection, time of stay in hospital, complications and outcome using Pearson's chi-squared test and logistic regression.

CONCLUSION

Sixteen patients were identified. Mean age of presentation was 8.8. An increased frequency of complications was observed in younger patients and longer survival rates in patients with greater resections; main mode of presentation was directly related to intracranial hypertension; size of tumor was not related to evolution or outcome. Modern histological classifications especially designed for children are deemed necessary to accurately diagnose GBM.

Radiosensitisation of U87MG brain tumours by anti-epidermal growth factor receptor monoclonal antibodies

As epidermal growth factor receptor (EGFR) has been reported to be a radiation response modulator, HER inhibitors are regarded to act as potential radiosensitisers. Our study examined the role of nimotuzumab and cetuximab both, the two monoclonal antibodies (mAbs) to EGFR, as radiosensitisers in a murine glioma model in vivo. Co-administration of both the antibodies with radiation increased the radiosensitivity of U87MG, resulting in a significant delay of subcutaneous (s.c.) tumour growth. Furthermore, the addition of antibodies to the radiation decreased brain tumour sizes and is inhibited by 40–80% the increased tumour cell invasion provoked by radiotherapy, although promoted tumour cell apoptosis. Whereas nimotuzumab led to a reduction in the size of tumour blood vessels and proliferating cells in s.c. tumours, cetuximab had no significant antiangiogenic nor antiproliferative activity. In contrast, cetuximab induced a more marked inhibition of EGFR downstream signalling compared with nimotuzumab. Moreover, both antibodies reduced the total number of radioresistant CD133+ cancer stem cells (CSCs). These results were encouraging, and showed the superiority of combined treatment of mAbs to EGFR and radiation over each single therapy against glioblastoma multiforme (GBM), confirming the role of these drugs as radiosensitisers in human GBM. In addition, we first showed the ability of mAb specifics against EGFR to target radioresistant glioma CSC, supporting the potential use in patients.

Selective distribution of protein kinase A regulatory subunit RII{alpha} in rodent gliomas

Differential diagnosis of brain tumor types is mainly based on cell morphology and could benefit from additional markers. The cAMP second-messenger system is involved in regulating cell proliferation and differentiation and is conceivably modulated during cancer transformation. The cAMP second-messenger system mainly activates protein kinases, which are in part docked to cytoskeleton, membranes, or organelles by anchoring proteins, forming protein aggregates that are detergent insoluble and not freely diffusible and that are characteristic for each cell type. The intracellular distribution of the detergent-insoluble regulatory subunits (R) of the cAMP-dependent protein kinase has been examined in mouse and rat glioma cells both in vitro and in vivo by immunohistochemistry. In normal rodent brains, the RIIalpha regulatory subunit is detergent insoluble only in ependymal cells, while in the rest of the brain it is present in soluble form. Immunohistochemistry shows that in both mouse and rat glioma cell lines, RIIalpha is mainly detergent insoluble. RIIalpha is localized close to the nucleus, associated with smooth vesicles in the trans-Golgi network area. Both paclitaxel and vinblastine cause a redistribution of RIIalpha within the cell. Under conditions that increased intracellular cAMP, apoptosis of glioma cells was observed, and it was accompanied by RIIalpha redistribution. Also in vivo, detergent-insoluble RIIalpha can be observed in mouse and rat gliomas, where it delineates the border between normal brain tissue and glioma. Therefore, intracellular distribution of detergent-insoluble RIIalpha can assist in detecting tumor cells within the brain, thus making the histologic diagnosis of brain tumors more accurate, and may represent an additional target for therapy.