Stem-like and highly invasive prostate cancer cells expressing CD44v8-10 marker originate from CD44-negative cells

// Chiara Di Stefano 1 , Paola Grazioli 2 , Rosaria Anna Fontanella 1 , Paola De Cesaris 3 , Antonella D’Amore 1 , Michele Regno 1 , Donatella Starace 1 , Fabrizio Padula 1 , Micol Elena Fiori 4 , Rita Canipari 1 , Antonella Stoppacciaro 6 , Margherita Pesce 6 , Antonio Filippini 1 , Antonio Francesco Campese 5 , Elio Ziparo 1, * and Anna Riccioli 1, * 1 Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Section of Histology and Medical Embryology, Sapienza University, Rome, Italy 2 Department of Experimental Medicine, Sapienza University, Rome, Italy 3 Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, L’Aquila, Italy 4 Department of Oncology and Molecular Medicine, Istituto Superiore di Sanita, Rome, Italy 5 Department of Molecular Medicine, Sapienza University, Rome, Italy 6 Division of Pathology, Sant'Andrea University Hospital, Rome, Italy * These authors have contributed equally to this work Correspondence to: Antonio Francesco Campese, email: antonello.campese@uniroma1.it Antonio Filippini, email: antonio.filippini@uniroma1.it Keywords: CD44; invasiveness; alternative splicing; prostate stem cells Received: April 16, 2018      Accepted: June 22, 2018      Published: July 20, 2018 ABSTRACT In human prostate cancer (PCa), the neuroendocrine cells, expressing the prostate cancer stem cell (CSC) marker CD44, may be resistant to androgen ablation and promote tumor recurrence. During the study of heterogeneity of the highly aggressive neuroendocrine PCa cell lines PC3 and DU-145, we isolated and expanded in vitro a minor subpopulation of very small cells lacking CD44 (CD44 neg ). Unexpectedly, these sorted CD44 neg cells rapidly and spontaneously converted to a stable CD44 high phenotype specifically expressing the CD44v8-10 isoform which the sorted CD44 high subpopulation failed to express. Surprisingly and potentially interesting, in these cells expression of CD44v8-10 was found to be induced in stem cell medium. CD44 variant isoforms are known to be more expressed in CSC and metastatic cells than CD44 standard isoform. In agreement, functional analysis of the two sorted and cultured subpopulations has shown that the CD44v8-10 pos PC3 cells, resulting from the conversion of the CD44 neg subpopulation, were more invasive in vitro and had a higher clonogenic potential than the sorted CD44 high cells, in that they produced mainly holoclones, known to be enriched in stem-like cells. Of interest, the CD44v8-10 is more expressed in human PCa biopsies than in normal gland. The discovery of CD44v8-10 pos cells with stem-like and invasive features, derived from a minoritarian CD44 neg cell population in PCa, alerts on the high plasticity of stem-like markers and urges for prudency on the approaches to targeting the putative CSC.