Mosaic Analysis with Double Markers Reveals Tumor Cell of Origin in Glioma

Chong Liu,Jonathan C. Sage,Michael R. Miller,Roel G.W. Verhaak,Simon Hippenmeyer,Hannes Vogel,Oded Foreman,Roderick T. Bronson,Akiko Nishiyama,Liqun Luo,and Hui Zong

DOI 10.1016/j.cell.2011.06.014

Presenter: Szu-Jung Chen Date/ Time:09-15-2011, 17:00~18:00

Commentator: Dr.張玲 Location: 601, College of Medicine

Background:

Glioma is a type of tumor derived from glial cells. This tumor mainly located in the brain or spine.In some studies, the human glioma cells which have stem cell features were isolated. This result implied that neural stem cells (NSCs) are the origin of glioma cells. In a mouse model, inactivation of tumor suppressor genes (TSGs) p53 andneurofibromatosis 1 (NF1) or the expression of a mutant form of p53 in NSCs led to glioma formation. Till now, due to the lack of high-resolution analysis method, it is difficult to track the cellular aberrations during the transforming process. Here, the mosaic analysis with double markers (MADM) was introduced. This is a mouse genetic mosaic system could be used to analyze aberrations in individual cell lineages prior to the final transformation and suitable for identifying cancer cell of origin.

Objective:

To identify the cell of origin for glioma when initial concurrent mutations of p53 and neurofibromatosis 1 (NF1) occur in embryonic neural stem cells (NSCs)

Results:

A mosaic analysis mouse models is created through Cre / loxP-mediated mitoticinterchromosomal recombination. In order to track the tumorigenesis of mutant cells, p53/NF1 mutant cells were labeled with green fluorescent protein (GFP) and wild type cells were labeled with red fluorescent protein (RFP). Compared to the brain of the wild type mouse, the brain of the mutant mouse expressed great amount of green fluorescence significantly after postnatal day 30-60(P30-P60). To find the cancer cell of origin, each NSC-derived cell type in mutant mouse brain of P60 was taken for GFP/RFP ratio analysis. The oligodendrocyte precursor cells (OPCs) had the significantly highest GFP/RFP ratio. However, the GFP/RFP ratio of NSCs was less at this stage, suggesting no growth advantage of mutant population of wild type cells. Therefore, at the pretransforming stage of mutant mouse brain, the NSCs failed to be directly transformed but OPCs functioned as the cells of origin for glioma. Next, they analyzed the expression of cell-specific markers in malignant tumors generated from the mutant mouse brain. The observation showed that tumors showed prominent NSCs markers (Nestin and Sox2) and this result was consistent with previous finding that NSCs origin of gliomas. Also, tumors expressed OPC markers(Olig2, PDGFRα, NG2, CD9 and O4) were further confirmed by quantitative RT-PCR. These tumor cells were injected into NOD-SCID mouse brain, and these tumor cells effectively induced secondary tumors and the molecular features were identical to primary tumors. Taken together, NSCs carrying p53/NF1 mutation enables OPCs progress and transform into glioma.

Conclusion:

This study illustrates the importance of analysis of progression of gliomagenesis for clarifying cancer cell of origin. When p53/NF1 was mutated in embryonic NSCs by MADM, this method provides an efficient way to discover cell morphology from premalignant stage to malignant glioma. Finally, they found that gliomagenesis could be induced in OPCs when mutated p53/NF1 was introduced. They also highlight the importance of analyzing premalignant stages to identify the cancer cell of origin,

Reference

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