Fig. 5: Amiloride-containing serum from patients was sufficient to acidify AML.

A The pHi of MOLM-13 and MV4-11, but not THP-1, decreased in the culture of amiloride-containing serum (ACS) compared with the culture of serum from the normal donor in vitro (n = 3). B Culture of ACS enhanced the apoptosis induction of different therapeutic agents (quizartinib 10 nM, ibrutinib 10 μM, cytarabine 10 μM, and doxorubicin 100 nM) in MV4-11 compared with the culture of serum from the normal donor in vitro (n = 4–6). C Calibrated curve of pHi using MV4-11 against amiloride concentration. pHi was measured for this cell line cultured in ACS to estimate the effective amiloride concentration in serum (n = 4). D ACS significantly reduced pHi of primary AML with FLT3 or RAS mutations (n = 16–25). E, F ACS reduced cell viability of primary AML samples carrying E FLT3 (n = 5–14) or F RAS (n = 7–9) mutations and accentuated the leukemia inhibitory effects of quizartinib (10 μM), ibrutinib (10 μM), and doxorubicin (1 μM). G, H ACS accentuated the apoptotic effects of quizartinib, ibrutinib, and doxorubicin in primary AML samples carrying G FLT3 (n = 8–13) and H RAS (n = 5–7) mutations. N: serum from healthy donors; A: amiloride-containing serum. In D–H, ACS from six individuals who were taking amiloride 20 mg daily for medical conditions unrelated to cancers were used. Serum from three healthy donors was used.