Fig. 2.

Hypoxia increases proline production in vitro. A, B Basal expression of PYCR1 and PYCR2 in 5 human MM cell lines (OPM-2, LP-1, RPMI-8226, JJN-3 and ANBL-6) and one stromal cell line (HS-5) is shown on RNA (A) and protein level (B) in normoxic conditions (n = 3). C Results of a tracer study where ¹³C-labeled glutamine was added to RPMI-8226 during 48 h in normoxic and hypoxic conditions (n = 1, measured in triplicate). The conversion rates of ¹³C-glutamine to proline are measured and shown in percentage. D Change in proline concentration, measured by ELISA after 48 h of culture in normoxic and hypoxic conditions (n = 3). nor = normoxia, hyp = hypoxia. Significance was determined by Mann–Whitney U test. * p ≤ 0.05