Glutamine metabolism is emerging as one aspect of dysregulated metabolism of tumors. Triple-negative breast cancer (TNBC) cells are glutamine dependent, whereas luminal-type cells tend to be glutamine independent. Therefore, TNBC patients might benefit from therapies targeting glutamine metabolism. To investigate the clinical significance of glutamine metabolism, we examined expression and prognostic significance of glutaminase in tumor cells and tumor-infiltrating lymphocytes (TILs) in TNBC. We retrieved 658 surgically resected TNBCs and analyzed glutaminase expression in tumor cells and TILs by immunohistochemical staining. Glutaminase expression was observed in 237 cases (36.0%) in tumor cells and 104 cases (15.5%) in TILs. Although glutaminase expression in tumor cells was significantly associated with a low level of TILs (p = 0.018), glutaminase expression in TILs was significantly higher in cases with a high level of TILs (p = 0.031). Glutaminase expression in tumor cells was significantly associated with poor disease-free survival in patients with lymph node metastasis and high levels of TILs (p = 0.020). In addition, it was an independent poor prognostic factor (hazard ratio = 10.643, 95% confidence interval = 1.999-56.668; p = 0.006). Glutaminase expression in tumor cells was observed in a subset of TNBC patients. It was significantly associated with a low level of TILs and poor disease-free survival in TNBCs presenting with lymph node metastasis and high levels of TILs.
Keywords: Glutaminase; Prognosis; Triple-negative breast cancer; Tumor-infiltrating lymphocytes.