Glioma stem cells are more aggressive in recurrent tumors with malignant progression than in the primary tumor, and both can be maintained long-term in vitro.

BACKGROUND: Despite the advances made during decades of research, the mechanisms by which glioma is initiated and established remain elusive. The discovery of glioma stem cells (GSCs) may help to elucidate the processes of gliomagenesis with respect to their phenotype, differentiation and tumorigenic capacity during initiation and progression. Research on GSCs is still in its infancy, so no definitive conclusions about their role can yet be drawn. To understand the biology of GSCs fully, it is highly desirable to establish permanent and biologically stable GSC lines. METHODS: In the current study, GSCs were isolated from surgical specimens of primary and recurrent glioma in a patient whose malignancy had progressed during the previous six months. The GSCs were cryopreserved and resuscitated periodically during long-term maintenance to establish glioma stem/progenitor cell (GSPC) lines, which were characterized by immunofluorescence, flow cytometry and transmission electronic microscopy. The primary and recurrent GSPC lines were also compared in terms of in vivo tumorigenicity and invasiveness. Molecular genetic differences between the two lines were identified by array-based comparative genomic hybridization and further validated by real-time PCR. RESULTS: Two GSPC lines, SU-1 (primary) and SU-2 (recurrent), were maintained in vitro for more than 44 months and 38 months respectively. Generally, the potentials for proliferation, self-renewal and multi-differentiation remained relatively stable even after a prolonged series of alternating episodes of cryopreservation and resuscitation. Intracranial transplantation of SU-1 cells produced relatively less invasive tumor mass in athymic nude mice, while SU-2 cells led to much more diffuse and aggressive lesions strikingly recapitulated their original tumors. Neither SU-1 nor SU-2 cells reached the terminal differentiation stage under conditions that would induce terminal differentiation in neural stem cells. The differentiation of most of the tumor cells seemed to be blocked at the progenitor cell phase: most of them expressed nestin but only a few co-expressed differentiation markers. Transmission electron microscopy showed that GSCs were at a primitive stage of differentiation with low autophagic activity. Array-based comparative genomic hybridization revealed genetic alterations common to both SU-1 and SU-2, including amplification of the oncogene EGFR and deletion of the tumor suppressor PTEN, while some genetic alterations such as amplification of MTA1 (metastasis associated gene 1) only occurred in SU-2. CONCLUSION: The GSPC lines SU-1 and SU-2 faithfully retained the characteristics of their original tumors and provide a reliable resource for investigating the mechanisms of formation and recurrence of human gliomas with progressive malignancy. Such investigations may eventually have major impacts on the understanding and treatment of gliomas.

[Expression of SV40Tag, Rb and IRS-1 in glioma detected by tissue microarray and their relation with tumorigenesis and progression of gliomas].

OBJECTIVE: To determine the expression of SV40Tag, Rb and IRS-1 in gliomas and to identify their function in gliomagenesis and progression. METHODS: Tissue microarrays were constructed containing 118 samples including human glioma and meningioma, experimental glioma, and normal human brain tissue. The expression of SV40Tag, Rb, IRS-1, SV40Tag combined with Rb, and SV40Tag combined with IRS-1 were assayed by immunofluorescence or immunohistochemical techniques. The expression ratio and level were analyzed. RESULTS: The expressions of SV40Tag, Rb and IRS-1 were detected in gliomas and benign brain tumors. Their positive expression rate in glioma was 65.9%, 64.6% and 48.8%, respectively, with a statistically non-significant difference between the malignant and benign brain tumors. The malignant degree was positively correlated with SV40Tag and IRS-1, but negatively correlated with Rb expression. The combined expression rate of SV40Tag and Rb was 51.2%, and the combined expression rate of SV40Tag and IRS-1 was 40.2%. In the normal human brain tissue only the expression of Rb (77.8%, 7/9) and IRS-1 (22.2%, 2/9) were detected, but expression of SV40Tag could not be observed. CONCLUSION: Our findings that no expression of SV40Tag was observed in normal human brain tissue indicates that expression of SV40Tag may play an important role in the pathogenesis of glioma. It may be assumed that after SV40 virus invading human body, Rb disfunction and IRS-1 activation promote the malignant transformation of cells, which could be one of important factors in pathogenesis and procession of glioms.

[Correlation of stem cell niche to genesis and development of tumor stem cells].

The tumor stem cell model proposes that tumor stem cells are the origin of most tumors. Like normal stem cells, tumor stem cells have the ability to self-renew and to give rise to the variety of proliferating and differentiated cells that make up the bulk of a tumor. Tumor stem cells could be derived from normal stem cells or differentiated cells. The stem cell niches are the microenvironment that maintains stem cells primarily in a quiescent state by providing signals that inhibit cell proliferation and growth. Loss of niches can result in loss of stem cells and increasing niches lead to an increased number of stem cells. Tumor stem cells could live in abnormal niches. Disrupting this abnormal niches may impair tumor stem cell self-renewal, thereby, significantly inhibits the growth of tumors. Targeting the unique microenvironment of tumor stem cells may be the key of effective cancer therapy.