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Mitochondrial p32 is upregulated in Myc expressing brain cancers and mediates glutamine addiction.

Fogal V, Babic I, Chao Y, Pastorino S, Mukthavaram R, Jiang P, Cho YJ, Pingle SC, Crawford JR, Piccioni DE, Kesari S - Oncotarget (2015)

Bottom Line: Loss of p32 in glutamine addicted glioma cells induced resistance to glutamine deprivation and imparted sensitivity to glucose withdrawal.Finally, we provide evidence that p32 expression contributes to Myc-induced glutamine addiction of cancer cells.Our findings suggest that Myc promotes the expression of p32, which is required to maintain sufficient respiratory capacity to sustain glutamine metabolism in Myc transformed cells.

View Article: PubMed Central - PubMed

Affiliation: Translational Neuro-Oncology Laboratories, Moores Cancer Center, University of California San Diego, La Jolla, CA.

ABSTRACT
Metabolic reprogramming is a key feature of tumorigenesis that is controlled by oncogenes. Enhanced utilization of glucose and glutamine are the best-established hallmarks of tumor metabolism. The oncogene c-Myc is one of the major players responsible for this metabolic alteration. However, the molecular mechanisms involved in Myc-induced metabolic reprogramming are not well defined. Here we identify p32, a mitochondrial protein known to play a role in the expression of mitochondrial respiratory chain complexes, as a critical player in Myc-induced glutamine addiction. We show that p32 is a direct transcriptional target of Myc and that high level of Myc in malignant brain cancers correlates with high expression of p32. Attenuation of p32 expression reduced growth rate of glioma cells expressing Myc and impaired tumor formation in vivo. Loss of p32 in glutamine addicted glioma cells induced resistance to glutamine deprivation and imparted sensitivity to glucose withdrawal. Finally, we provide evidence that p32 expression contributes to Myc-induced glutamine addiction of cancer cells. Our findings suggest that Myc promotes the expression of p32, which is required to maintain sufficient respiratory capacity to sustain glutamine metabolism in Myc transformed cells.

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Attenuation of p32 expression reduces glioma cell proliferation and tumor growth(A) Upper panels: colony formation assay of control and p32 knockdown stable cell lines. The graphs represent the mean ± SD of at least three independent colony formation assays each performed in triplicate (middle panel). Lower: Western blot analysis demonstrating p32 stable knockdown in the indicated glioma cell lines. (B) Microscopic analysis of p32 knockdown and control GBM4 and GBM5 glioma stem cell-like neuropheres. Right panel-western blot showing efficient p32 knockdown in the indicated glioma stem cell-like cells. (C) Tumor growth properties of U87 cells (left panel) and GBM4 glioma stem cell-like cells (right panel) infected with viruses encoding control or p32 kd shRNA. The graphs represent the mean ± SEM (p < 0.001) of tumor volumes as a function of time. The lower panels show pictures of tumors from each group (n = 14 or n = 11) at the end point.
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Figure 5: Attenuation of p32 expression reduces glioma cell proliferation and tumor growth(A) Upper panels: colony formation assay of control and p32 knockdown stable cell lines. The graphs represent the mean ± SD of at least three independent colony formation assays each performed in triplicate (middle panel). Lower: Western blot analysis demonstrating p32 stable knockdown in the indicated glioma cell lines. (B) Microscopic analysis of p32 knockdown and control GBM4 and GBM5 glioma stem cell-like neuropheres. Right panel-western blot showing efficient p32 knockdown in the indicated glioma stem cell-like cells. (C) Tumor growth properties of U87 cells (left panel) and GBM4 glioma stem cell-like cells (right panel) infected with viruses encoding control or p32 kd shRNA. The graphs represent the mean ± SEM (p < 0.001) of tumor volumes as a function of time. The lower panels show pictures of tumors from each group (n = 14 or n = 11) at the end point.

Mentions: To assess the impact of p32 on glioma cell proliferation, we generated stable glioma cell lines with attenuated p32 expression (Fig. 5A lower panels). The p32 knockdown (p32 kd) cell lines exhibit reduced proliferation rate as revealed by colony formation assays (Fig. 5A upper panels). Furthermore, stable transduction of patient-derived glioma stem cell-like lines with p32 shRNA lentivirus significantly reduced neurosphere formation when compared to control shRNA infected cells (Fig. 5B). Significantly, p32 kd glioma cells and patient derived cell lines produced smaller tumors in vivo compared to control (Fig. 5C).


Mitochondrial p32 is upregulated in Myc expressing brain cancers and mediates glutamine addiction.

Fogal V, Babic I, Chao Y, Pastorino S, Mukthavaram R, Jiang P, Cho YJ, Pingle SC, Crawford JR, Piccioni DE, Kesari S - Oncotarget (2015)

Attenuation of p32 expression reduces glioma cell proliferation and tumor growth(A) Upper panels: colony formation assay of control and p32 knockdown stable cell lines. The graphs represent the mean ± SD of at least three independent colony formation assays each performed in triplicate (middle panel). Lower: Western blot analysis demonstrating p32 stable knockdown in the indicated glioma cell lines. (B) Microscopic analysis of p32 knockdown and control GBM4 and GBM5 glioma stem cell-like neuropheres. Right panel-western blot showing efficient p32 knockdown in the indicated glioma stem cell-like cells. (C) Tumor growth properties of U87 cells (left panel) and GBM4 glioma stem cell-like cells (right panel) infected with viruses encoding control or p32 kd shRNA. The graphs represent the mean ± SEM (p < 0.001) of tumor volumes as a function of time. The lower panels show pictures of tumors from each group (n = 14 or n = 11) at the end point.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4359224&req=5

Figure 5: Attenuation of p32 expression reduces glioma cell proliferation and tumor growth(A) Upper panels: colony formation assay of control and p32 knockdown stable cell lines. The graphs represent the mean ± SD of at least three independent colony formation assays each performed in triplicate (middle panel). Lower: Western blot analysis demonstrating p32 stable knockdown in the indicated glioma cell lines. (B) Microscopic analysis of p32 knockdown and control GBM4 and GBM5 glioma stem cell-like neuropheres. Right panel-western blot showing efficient p32 knockdown in the indicated glioma stem cell-like cells. (C) Tumor growth properties of U87 cells (left panel) and GBM4 glioma stem cell-like cells (right panel) infected with viruses encoding control or p32 kd shRNA. The graphs represent the mean ± SEM (p < 0.001) of tumor volumes as a function of time. The lower panels show pictures of tumors from each group (n = 14 or n = 11) at the end point.
Mentions: To assess the impact of p32 on glioma cell proliferation, we generated stable glioma cell lines with attenuated p32 expression (Fig. 5A lower panels). The p32 knockdown (p32 kd) cell lines exhibit reduced proliferation rate as revealed by colony formation assays (Fig. 5A upper panels). Furthermore, stable transduction of patient-derived glioma stem cell-like lines with p32 shRNA lentivirus significantly reduced neurosphere formation when compared to control shRNA infected cells (Fig. 5B). Significantly, p32 kd glioma cells and patient derived cell lines produced smaller tumors in vivo compared to control (Fig. 5C).

Bottom Line: Loss of p32 in glutamine addicted glioma cells induced resistance to glutamine deprivation and imparted sensitivity to glucose withdrawal.Finally, we provide evidence that p32 expression contributes to Myc-induced glutamine addiction of cancer cells.Our findings suggest that Myc promotes the expression of p32, which is required to maintain sufficient respiratory capacity to sustain glutamine metabolism in Myc transformed cells.

View Article: PubMed Central - PubMed

Affiliation: Translational Neuro-Oncology Laboratories, Moores Cancer Center, University of California San Diego, La Jolla, CA.

ABSTRACT
Metabolic reprogramming is a key feature of tumorigenesis that is controlled by oncogenes. Enhanced utilization of glucose and glutamine are the best-established hallmarks of tumor metabolism. The oncogene c-Myc is one of the major players responsible for this metabolic alteration. However, the molecular mechanisms involved in Myc-induced metabolic reprogramming are not well defined. Here we identify p32, a mitochondrial protein known to play a role in the expression of mitochondrial respiratory chain complexes, as a critical player in Myc-induced glutamine addiction. We show that p32 is a direct transcriptional target of Myc and that high level of Myc in malignant brain cancers correlates with high expression of p32. Attenuation of p32 expression reduced growth rate of glioma cells expressing Myc and impaired tumor formation in vivo. Loss of p32 in glutamine addicted glioma cells induced resistance to glutamine deprivation and imparted sensitivity to glucose withdrawal. Finally, we provide evidence that p32 expression contributes to Myc-induced glutamine addiction of cancer cells. Our findings suggest that Myc promotes the expression of p32, which is required to maintain sufficient respiratory capacity to sustain glutamine metabolism in Myc transformed cells.

Show MeSH
Related in: MedlinePlus