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Elucidating the Role of DEPTOR in Cultured Glioblastoma Multiforme Cancer Cells
Author(s) -
Ryan Patrick J,
Deaver J William,
Koo Sunwoo,
Touissaint L Gerard,
Fluckey James D
Publication year - 2019
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2019.33.1_supplement.lb604
Subject(s) - pi3k/akt/mtor pathway , cancer research , u87 , p70 s6 kinase 1 , protein kinase b , glioma , rptor , downregulation and upregulation , mtorc1 , carcinogenesis , cancer , mtorc2 , cell growth , biology , chemistry , medicine , signal transduction , microbiology and biotechnology , biochemistry , gene
Glioblastoma multiforme (GBM) is the primary malignancy of the brain, representing 45% of all central nervous system tumors. Aggressive and incurable, GBM is generally fatal within two years of diagnosis, despite the best treatment. The cause and progression of these tumors remains a mystery; however, what is known about GBM pathology indicates a role for the anabolic AKT/mTOR pathway in tumorigenesis and growth. Our group and others recently identified an endogenously produced direct inhibitor of mTOR, DEPTOR, which binds mTOR and potently inhibits its activity. As previous attempts to prevent cell growth in GBM have only been marginally successful, manipulation of an effective innate inhibitor of mTOR could provide a viable avenue toward new therapeutics for this deadly cancer. With this in mind, we set out to characterize the role of DEPTOR in cultured glioblastoma cells. Immortalized U87 glioblastoma cells were grown and harvested in cell culture, along with U87 cells selected for invasive potential to model a more aggressive subset of tumors (designated IM3), and cultured astrocytes to provide an adjacent tissue comparison. Western blot methodology was used to investigate the status of several key proteins in the AKT/mTOR axis (including DEPTOR), as well as the relative abundance and phosphorylation status of downstream targets of mTOR (S6K1 and 4EBP1). We determined that key measures of anabolic signaling were elevated in the cultured GBM cells, with double the ratio of phosphorylated to total S6K1 observed in both GBM lines versus the astrocyte, along with reductions in total 4EBP1, indicating upregulation of cap‐dependent protein synthesis. Further, DEPTOR expression was reduced five‐fold in cultured GBM cells, indicating that this “brake” on mTOR has been removed, resulting in rampant and out‐of‐control anabolism. Taken together, these findings hint that lack of DEPTOR may play a role in GBM pathology, and suggest that further investigation into the interplay between DEPTOR, mTOR, and cancer cell growth in GBM is warranted. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .