Fig. 1. l-Arginine decreases tumor lactate concentration in BM.

(A) Expression of NOS2 in 42 BM specimens. The Y axis indicates the percent of positive cells, the color scale represents intensity of expression, and the shape represents different origins of the primary tumor. Representative immunohistochemistry images of two patients with BM from NSCLC. Scale bars, 100 μm. (B) NOS2 expression in MDA-MB-231 and MDA-MB-231-BrM2 cells treated with interleukin-6 (IL-6) and hypoxia (1% O₂). (C) Hemodynamic parameters obtained from five patients treated with a single oral dose of 10 g of l-arginine. (D) Plasma concentration of l-arginine obtained from patients in (C). (E) Quantification of tumor lactate in BM before (PRE) and after (POST) administration of placebo (n = 5) and l-arginine (n = 5) taken 24 hours apart. (F) Representative magnetic resonance spectrograms and corresponding images from a patient with BM treated with placebo (top) and 24 hours later with l-arginine (bottom). The arrow indicates the lactate peak.