Metabolic targeting of EGFRvIII/PDK1 axis in temozolomide resistant glioblastoma

Velpula, Kiran Kumar; Guda, Maheedhara R.; Sahu, Kamlesh Kumar; Tuszyński, Jack A.; Asuthkar, Swapna; Bach, Sarah E.; Lathia, Justin D.; Tsung, Andrew J.

doi:10.18632/oncotarget.16767

Cited by 28 publications

(26 citation statements)

References 51 publications

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“…Interestingly our results showed that TMZ-induced apoptosis is not associated with changes in Bcl-2, Bcl-XL, Mcl-1, and Bax expression in RH30 and C2C12 cell lines. It has been previously reported that TMZ-induced apoptosis decreases mitochondrial membrane potential in glioma cell line 78 , 79 while our results showed that TMZ-induced apoptosis had not affected the mitochondrial membrane potential in both RH30 and C2C12 cells. This observation can be explained by our finding that TMZ has not affected the expression of anti-apoptotic (Bcl-2, Bcl-XL, and Mcl-1), and pro-apoptotic (Bax) Bcl-2 family proteins.…”

Section: Discussioncontrasting

confidence: 49%

Autophagy modulates temozolomide-induced cell death in alveolar Rhabdomyosarcoma cells

et al. 2018

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Rhabdomyosarcoma (RMS) is a muscle-derived tumor. In both pre-clinical and clinical studies Temozolomide (TMZ) has been recently tested against RMS; however, the precise mechanism of action of TMZ in RMS remains unclear. Here we demonstrate that TMZ decreases the cell viability of the RH30 RMS and C2C12 cell line, where cells display evidence of mitochondrial outer membrane permeability. Interestingly, the C2C12 mouse myoblast line was relatively more resistant to TMZ-induced apoptosis. Moreover, we observed that TMZ activated biochemical and morphological markers of autophagy in both cell lines. Autophagy inhibition in both RH30 and C2C12 cells significantly increased TMZ-induced cell death. In RH30 cells, TMZ increased Mcl-1 and Bax protein expression compared to corresponding time match controls while in C2C12 Mcl-1, Bcl-2, Bcl-XL, and Bax protein expression were not changed. Baf-A1 co-treatment with TMZ significantly decrease Mcl-1 expression compared to TMZ while increase Bax expression in C2C12 cells (Bcl2 and Bcl-XL do not significantly change in Baf-A1/TMZ co-treatment). Using a three-dimensional (3D) C2C12 and RH30 culture model we demonstrated that TMZ is significantly more toxic in RH30 cells (live/dead assay). Additionally, we have observed in our 3D culture model that TMZ induced both apoptosis (cleavage of PARP) and autophagy (LC3-puncta and localization of LC3/p62). Therefore, our data demonstrate that TMZ induces simultaneous autophagy and apoptosis in both RH30 and C2C12 cells in 2D and 3D culture model, where RH30 cells are more sensitive to TMZ-induced death. Furthermore, autophagy serves to protect RH30 cells from TMZ-induced death.

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Section: Discussioncontrasting

confidence: 49%

Autophagy modulates temozolomide-induced cell death in alveolar Rhabdomyosarcoma cells

et al. 2018

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“…In fact, Koukourakis et al sensitized glioblastoma cell lines, namely the most resistant ones, to conventional therapies (radiotherapy and chemotherapy with TMZ), using the glycolytic inhibitor 2‐DG and the LDHA inhibitor oxamate, as well as LDHA gene silencing. Velpula et al also demonstrated that other mechanisms than MGMT expression can be involved in MDR phenotype, namely in glioblastomas. The authors observed that DCA increases TMZ cytotoxicity, reverting the Warburg effect through tyrosine kinase signalling, namely via EGFRvIII.…”

Section: Discussionmentioning

confidence: 99%

Bioenergetic modulators hamper cancer cell viability and enhance response to chemotherapy

Tavares-Valente

Granja

Baltazar

et al. 2018

J Cellular Molecular Medi

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Gliomas are characterized by a marked glycolytic metabolism with a consequent production of massive amounts of lactate, even in the presence of normal levels of oxygen, associated to increased invasion capacity and to higher resistance to conventional treatment. This work aimed to understand how the metabolic modulation can influence tumour aggressive features and its potential to be used as complementary therapy. We assessed the effect of bioenergetic modulators (BMs) targeting different metabolic pathways in glioma cell characteristics. The in vivo effect of BMs was evaluated using the chicken chorioallantoic membrane model. Additionally, the effect of pre‐treatment with BMs in the response to the antitumour drug temozolomide (TMZ) was analysed in vitro. Cell treatment with the BMs induced a decrease in cell viability and in migratory/invasion abilities, as well as modifications in metabolic parameters (glucose, lactate and ATP) and increased the cytotoxicity of the conventional drug TMZ. Furthermore, all BMs decreased the tumour growth and the number of blood vessels in an in vivo model. Our results demonstrate that metabolic modulation has the potential to be used as therapy to decrease the aggressiveness of the tumours or to be combined with conventional drugs used in glioma treatment.

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“…Studies that investigate the features of drug-resistant tumor cells in vitro frequently employ long-term culture of tumor cells, where slowly increasing concentrations of a given drug are repeatedly added over the course of weeks or many months [ 3 , 4 , 5 , 6 , 7 ]. In the in vivo situation, or in patient tissues, as well, when before-and-after specimens are being compared, the samples usually differ by many cycles of drug treatment [ 8 , 9 , 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

Rare Stochastic Expression of O6-Methylguanine- DNA Methyltransferase (MGMT) in MGMT-Negative Melanoma Cells Determines Immediate Emergence of Drug-Resistant Populations upon Treatment with Temozolomide In Vitro and In Vivo

Chen

Chan

Minea

et al. 2018

Cancers

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The chemotherapeutic agent temozolomide (TMZ) kills tumor cells preferentially via alkylation of the O6-position of guanine. However, cells that express the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT), or harbor deficient DNA mismatch repair (MMR) function, are profoundly resistant to this drug. TMZ is in clinical use for melanoma, but objective response rates are low, even when TMZ is combined with O6-benzylguanine (O6BG), a potent MGMT inhibitor. We used in vitro and in vivo models of melanoma to characterize the early events leading to cellular TMZ resistance. Melanoma cell lines were exposed to a single treatment with TMZ, at physiologically relevant concentrations, in the absence or presence of O6BG. Surviving clones and mass cultures were analyzed by Western blot, colony formation assays, and DNA methylation studies. Mice with melanoma xenografts received TMZ treatment, and tumor tissue was analyzed by immunohistochemistry. We found that MGMT-negative melanoma cell cultures, before any drug treatment, already harbored a small fraction of MGMT-positive cells, which survived TMZ treatment and promptly became the dominant cell type within the surviving population. The MGMT-negative status in individual cells was not stable, as clonal selection of MGMT-negative cells again resulted in a mixed population harboring MGMT-positive, TMZ-resistant cells. Blocking the survival advantage of MGMT via the addition of O6BG still resulted in surviving clones, although at much lower frequency and independent of MGMT, and the resistance mechanism of these clones was based on a common lack of expression of MSH6, a key MMR enzyme. TMZ treatment of mice implanted with MGMT-negative melanoma cells resulted in effective tumor growth delay, but eventually tumor growth resumed, with tumor tissue having become MGMT positive. Altogether, these data reveal stochastic expression of MGMT as a pre-existing, key determinant of TMZ resistance in melanoma cell lines. Although MGMT activity can effectively be eliminated by pharmacologic intervention with O6BG, additional layers of TMZ resistance, although considerably rarer, are present as well and minimize the cytotoxic impact of TMZ/O6BG combination treatment. Our results provide rational explanations regarding clinical observations, where the TMZ/O6BG regimen has yielded mostly disappointing outcomes in melanoma patients.

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Metabolic targeting of EGFRvIII/PDK1 axis in temozolomide resistant glioblastoma

Cited by 28 publications

References 51 publications

Autophagy modulates temozolomide-induced cell death in alveolar Rhabdomyosarcoma cells

Autophagy modulates temozolomide-induced cell death in alveolar Rhabdomyosarcoma cells

Bioenergetic modulators hamper cancer cell viability and enhance response to chemotherapy

Rare Stochastic Expression of O6-Methylguanine- DNA Methyltransferase (MGMT) in MGMT-Negative Melanoma Cells Determines Immediate Emergence of Drug-Resistant Populations upon Treatment with Temozolomide In Vitro and In Vivo

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