Clinically relevant doses of chemotherapy agents reversibly block formation of glioblastoma neurospheres

Abstract

Glioblastoma patients have a poor prognosis, even after surgery, radiotherapy, and chemotherapy with temozolomide or 1,3-bis(2-chloroethy)-1-nitrosourea. We developed an in vitro recovery model using neurosphere cultures to analyze the efficacy of chemotherapy treatments, and tested whether glioblastoma neurosphere initiating cells are resistant. Concentrations of chemotherapy drugs that inhibit neurosphere formation are similar to clinically relevant doses. Some lines underwent a transient cell cycle arrest and a robust recovery of neurosphere formation. These results indicate that glioblastoma neurospheres can regrow after treatment with chemotherapy drugs. This neurosphere recovery assay will facilitate studies of chemo-resistant subpopulations and methods to enhance glioblastoma therapy.

Glioma Stem Cells: Cell Culture, Markers and Targets for New Combination Therapies

“…The neurosphere recovery assay provides a quantitative cell culture assay to test the efficacy of drug combinations at inhibiting repopulation. We demonstrated that temozolomide drastically diminished initial neurosphere formation in many glioma cultures; however, these cultures eventually recovered and formed a robust number of secondary neurospheres (Mihaliak et al, 2010). The ability of temozolomide treated neurospheres to recover and repopulate the culture suggests that some cells undergo a transient cell cycle arrest, allowing them to evade cell death and eventually resume proliferation.…”

“…Several groups have proposed that cancer stem cells readily assume a quiescent state and later, following DNA repair, repopulate the tumor (Mellor et al, 2005;Scopelliti et al, 2009). Our laboratory recently demonstrated that even low doses of temozolomide can induce quiescence followed by a robust recovery of the culture (Mihaliak et al, 2010). The neurosphere recovery assay provides a quantitative cell culture assay to test the efficacy of drug combinations at inhibiting repopulation.…”

“…Based on these data, CD133 + populations were more resistant to ionizing radiation in colony formation assays compared to the corresponding CD133 -populations. On the other hand, it has been shown that number of CD133 + glioma cells can decrease or show no significant change after chemotherapy treatment (Beier et al, 2008;Mihaliak et al, 2010). There may be several explanations for these inconsistent results.…”

“…Finally, the disparate results may be on account of the time points that the data are analyzed after treatments and the concentrations of the drug treatments. Mihaliak et al (2010) demonstrated that the chemotherapy treatments induced a cell cycle arrest in the neurosphere initiating cells at clinically relevant doses, but required higher concentrations to induce cell death in the bulk of the cells. The drug concentrations to achieve this cell cycle arrest varied both by cell line and by the chemotherapy drug used.…”

Biophysical Effects of Cold Atmospheric Plasma on Glial Tumor Cells

“…Further publications addressing cancers of breast, brain, colon, lung, skin, and pancreas followed. The main focus in these studies was on the analysis of growth inhibition [28,29], inhibition of migration and invasion [30], induction of cell cycle arrest [31,32] and induction of apoptosis in a dose-dependent manner [33,34], [35][36][37][38][39]. Recent experiments on melanoma verified the induction of apoptosis with high CAP treatment times, whereas low treatment times were able to induce senescence [40].…”