Glutamine Dependence Is Not a Cancer-specific Vulnerability in Contrast to Methionine Dependence

BACKGROUND/AIM: Glutamine (GLN) addiction has been proposed as a cancer vulnerability and a therapeutic target. However, the glutamine requirement of normal cells is poorly understood. In the present study, we used a unique co-culture model to study the glutamine requirement of cancer cells compared to normal cells co-cultured together. MATERIALS AND METHODS: The human fibrosarcoma cell line HT1080 and normal human fibroblasts HS27 were co-cultured in 12-well dishes seeded with equal numbers of cells of each type. Additionally, HS27 cells were cultured alone in 6-well plates. The cells were grown in Dulbecco's Modified Eagle's Medium (DMEM) which did not contain GLN, methionine (MET), or cystine (CYS). 150 μM L-cystine 2HCl was added to all media. Co- and mono- cultures were grown under the following conditions: Complete medium (GLN 4 mM and MET 100 μM); MET restriction [Methionine restriction (MR), GLN 4 mM and MET 0 μM]; GLN restriction [Glutamine restriction (GR), GLN 0 mM and MET 100 μM] and MR+GR (GLN 0 mM and MET 0 μM). Cells were observed under phase-contrast and fluorescence microscopy for seven days. ImageJ was used to compare the three groups: MR, GR and MR+GR. RESULTS: In complete DMEM, HT1080 fibrosarcoma cells dominated HS27 normal fibroblasts in co-culture. Under MR, HT1080 cells became mostly non viable, but HS27 cells remained viable. Under GR and MR+GR, both HT1080 and HS27 cells became mostly non-viable. Monoculture experiments showed that normal cells survived under MR but not GR. CONCLUSION: GR is not a cancer-specific vulnerability, while MR is. Therefore, GR is not a promising cancer-therapy strategy.