IN VITRO EFFECTS OF METFORMIN IN COMBINATION WITH THE INHIBITION OF THE PENTOSE PHOSPHATE PATHWAY IN HUMAN GLIOBLASTOMA CELLS

MACHARASVILI, IVAN; ARBE, MARÍA FLORENCIA; GLIKIN, GC; FINOCCHIARO, LME; VILLAVERDE, MARCELA SOLANGE

Congreso; SAIC 2021; 2021

The pentose phosphate pathway (PPP) enables cancer cells toadapt to oxidative stress and lipid synthesis by means of the production of NADPH. The inhibition of PPP key enzymes, includingglucose-6-phosphate dehydrogenase (G6PD), strongly affects cancer cell proliferation in vitro, as well as in vivo. We have previously shown that monolayers of glioblastoma (GBM) cell lines resultsensitive to PPP inhibition by 6AN. In addition, the combination of6AN with metformin (MET, an oral drug for the treatment of T2MD)increases the effectiveness of both monotherapies. Here we investigated the impact of 6AN (10 or 25 µM) alone or in combinationwith MET (5 mM) on i) clonogenic cells and spheroids (3D) of twoGBM cell lines (U251 and U373), ii) the AMPK/mTOR/S6 axis (byimmunostaining of pACC (an AMPK substrate) and pS6 (a mTORpathway effector)) and iii) the presence of senescent cell (by thesenescent associated β-galactosidase enzyme activity). We foundthat 6AN alone, and the combination of MET/6AN altered spheroids development and clonogenic efficiency of U251 and U373GBM cells. Media supplementation with 5 mM nicotinamide (NAM,a precursor of NADPH) or 100 µM NADPH was able to counteractalmost completely (NAM) and partially (NADPH) the effects of 6ANon clonogenic cells. After 24 h of treatments, we found a decreasein pS6 (decreased mTOR signaling) and an increase in pACC immunostaining (increased AMPK activity) compared to control cells with both monotherapies and combinatory approach. Finally, 7 days of treatment with 10 µM 6AN promoted the presence of β-galactosidase positive giant cells probably related with a senescent process. The presence of these cells was prevented by 5 mM NAM. In conclusion, our results indicate that the combination of MET/6ANdecreases the mTOR pathway signaling affecting 3D cultures andclonogenic efficiency of glioblastoma cells.