The complex metabolic network gearing the G1/S transition in leukemic stem cells: Hints to a rational use of antineoplastic agents

Abstract

We defined the stem cell profile of K562 line, demonstrating the expression of the Embryonic Transcription Factors Oct3/4, Sox2, Klf4 and Nanog. This profile was associated with a high vulnerability to the physiological oxidizable substrate pyruvate. remarkably, this substrate was shown to be innocuous, even at the highest doses, to normal differentiated cells. This vulnerability is based on a complex metabolic trim centered on the cellular redox state expressed by the NADP/NADPH ratio geared by the mitochondrial respiratory chain. Flow cytometry revealed that the inhibition of this chain by antimycin A produced cell accumulation in the S phase of cell cycle and apoptosis. This block negatively interferes with the aerobic synthesis of purines, without affecting the anaerobic synthesis of pyrimidines. This imbalance was reproduced by using two antifolate agents, LY309887 and raltitrexed (TDX), inhibitors of purine or pyrimidine synthesis, respectively. All this revealed the apparent paradox that low doses of TDX stimulated, instead of inhibiting, leukemia cell growth. This paradox might have significant impact on therapy with regard to the effects of TDX during the intervals of administration, when the drug concentrations become so low as to promote maintenance of dormant cancer cells in hypoxic tissue niches.

Targeting the Extracellular Signal-Regulated Kinase 5 Pathway to Suppress Human Chronic Myeloid Leukemia Stem Cells

“…The combination of XMD8-92 with imatinib suppressed both p27 and p21 proteins. This combination also decreased the expression of the stemness-related genes c-MYC, SOX2, and NANOG ( Laurenti et al., 2008 , Stivarou et al., 2015 ), but not that of OCT3/4 and KLF4, in comparison with either treatment alone or vehicle ( Figure S6 and not shown).

Figure 6 Effects of the Combination of MEK5/ERK5 Inhibitors with Imatinib on the Expression of Stem Cell-Related Proteins (A) Cells were incubated in 0.1% O 2 and treated with DMSO, 1 μM imatinib, 10 μM XMD8-92 (XMD), or their combination from time 0 to day 7.

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“…More importantly, the combination with imatinib did not interfere with the suppressive effect of XMD8-92 on progenitor cell potential in CML cell lines and primary CML cells. Rather, this combination may provide advantages, as the XMD8-92/imatinib combination, differently from the single treatments, reduced the expression of stemness-related genes such as c-MYC, SOX2, and NANOG ( Li et al., 1999 , Laurenti et al., 2008 , Stivarou et al., 2015 ), and suppressed both p21 and p27 proteins. With respect to the latter effects, p21 is critical for preventing HSC and LSC exhaustion while p27 regulates the proliferation and pool size of hematopoietic progenitor cells ( Cheng et al., 2000b ).…”

Low-dose methotrexate enhances cycling of highly anaplastic cancer cells

“…The inhibitory effects of antimycin A or pyruvate are removed by the addition of purines, but not pyrimidines, indicating that the G 1 -S transition of AH130 cells depends on respiration-linked steps of purine synthesis. 7 Since a complex series of NADP-dependent interconversions of F derivatives is necessary for purine synthesis, 8 we hypothesized that some respiration-linked reaction involved in F metabolism represent the limiting step of G 1 -S transition. 2 On this basis, in the study reported here, we tested the effects of 10 nM MTX and/or F on G 1 -S transition of AH130 cells, as determined by R measuring, at 18 hours of incubation in the presence or the absence of pyruvate or antimycin A ( Fig.…”

“… 2 It is worth pointing out here that, in several different cancer (stem) cell populations, the purine pools are sensitive to the inhibition/saturation of respiratory chain (antimycin A/pyruvate), while the pyrimidine pools are usually sufficient to ensure cell cycling. 7,12,13 This implies that purines but not pyrimidines are critical to DNA synthesis. Purine synthesis requires the NADP-dependent oxidation of N 5 N 10 methylenFH 4 to N 5 N 10 methenylFH 4 , which is paralelled by NADPH production.…”

The unveiling of the Warburg effect and the inscribed innovative approach to a radical non toxic anticancer therapy

“…This is a complex, ATP-dependent process, due to multiple DNA mutations, which manifest only after latencies since the application of the initiating event [ 29 ]. We showed that the impairment of the respiratory chain by pyruvate or antimycin A leads to a severe restriction of purine pool, without affecting the pyrimidine pool [ 26 ]. Since DNA synthesis and turn-over are tightly coupled with the balance among the various deoxynucleotides, alteration of this balance produces high ratios of mis-incorporation of this precursors into DNA, and hence genetic mutations [ 30 ].…”