Chronic myeloid leukemia progenitor cells require autophagy when leaving hypoxia-induced quiescence

// Angela Ianniciello 1, * , Pierre-Yves Dumas 1, * , Claire Drullion 1, * , Amélie Guitart 1 , Arnaud Villacreces 1 , Yan Peytour 1 , Jean Chevaleyre 1, 5 , Philippe Brunet de la Grange 1, 5 , Isabelle Vigon 1 , Vanessa Desplat 1 , Muriel Priault 2 , Persio Dello Sbarba 3 , Zoran Ivanovic 1, 5 , François-Xavier Mahon 4 and Jean-Max Pasquet 1 1 Cellules Souches Hématopoïétiques Normales et Leucémiques, INSERM U1035 BMGIC, Université de Bordeaux, 33076 Bordeaux Cedex, France 2 UMR CNRS 5095, I.B.G.C, Université de Bordeaux, 33077 Bordeaux Cedex, France 3 Department of Experimental and Clinical Biomedical Sciences, Università degli Studi di Firenze, 50134 Firenze, Italia 4 INSERM U1218, Institut Bergonié, 33076 Bordeaux, France 5 Etablissement Français du Sang Aquitaine-Limousin, 33075 Bordeaux, France * These authors contributed equally to this work Correspondence to: Jean-Max Pasquet, email: jean-max.pasquet@inserm.fr Keywords: chronic myeloid leukemia, autophagy, stem cell Received: September 01, 2016      Accepted: June 17, 2017      Published: June 30, 2017 ABSTRACT Albeit tyrosine kinase inhibitors anti-Abl used in Chronic Myeloid Leukemia (CML) block the deregulated activity of the Bcr-Abl tyrosine kinase and induce remission in 90% of patients, they do not eradicate immature hematopoietic compartments of leukemic stem cells. To elucidate if autophagy is important for stem cell survival and/or proliferation, we used culture in low oxygen concentration (0.1% O 2 for 7 days) followed back by non-restricted O 2 supply (normoxic culture) to mimic stem cell proliferation and commitment. Knockdown of Atg7 expression, a key player in autophagy, in K562 cell line inhibited autophagy compared to control cells. Upon 7 days at 0.1% O 2 both K562 and K562 shATG7 cells stopped to proliferate and a similar amount of viable cells remained. Back to non-restricted O 2 supply K562 cells proliferate whereas K562 shATG7 cells exhibited strong apoptosis. Using immunomagnetic sorted normal and CML CD34 + cells, we inhibited the autophagic process by lentiviral infection expressing shATG7 or using a Vps34 inhibitor. Both, normal and CML CD34 + cells either competent or deficient for autophagy stopped to proliferate in hypoxia. Surprisingly, while normal CD34 + cells proliferate back to non restricted O 2 supply, the CML CD34 + cells deficient for autophagy failed to proliferate. All together, these results suggest that autophagy is required for CML CD34 + commitment while it is dispensable for normal CD34 cells.