A highly invasive subpopulation of MDA-MB-231 breast cancer cells shows accelerated growth, differential chemoresistance, features of apocrine tumors and reduced tumorigenicity<i>in vivo</i>

Abstract

// Adriana Amaro 1, * , Giovanna Angelini 1, * , Valentina Mirisola 1 , Alessia Isabella Esposito 1 , Daniele Reverberi 1 , Serena Matis 1 , Massimo Maffei 1 , Walter Giaretti 1 , Maurizio Viale 2 , Rosaria Gangemi 2 , Laura Emionite 3 , Simonetta Astigiano 4 , Michele Cilli 3 , Beatrice E. Bachmeier 5 , Peter H. Killian 5 , Adriana Albini 6 , Ulrich Pfeffer 1 1 Molecular Pathology, IRCCS AOU San Martino &ndash; IST Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy 2 Biotherapy, IRCCS AOU San Martino &ndash; IST Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy 3 Animal Facility, IRCCS AOU San Martino &ndash; IST Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy 4 Immunology, IRCCS AOU San Martino &ndash; IST Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy 5 Institute of Laboratory Medicine, Ludwig-Maximilians-University, Munich, Germany 6 Scientific and Technology Park, IRCCS MultiMedica, Milan, Italy * These authors have contributed equally to the work Correspondence to: Adriana Albini, email: adriana.albini@multimedica.it Ulrich Pfeffer, email: patologia.molecolare.integrata@gmail.com Keywords: breast cancer, invasion, apocrine breast cancer, metastasis, aneuploidy Received: May 16, 2016&emsp;&emsp;&emsp;&emsp; Accepted: August 13, 2016&emsp;&emsp;&emsp;&emsp; Published: September 10, 2016 ABSTRACT The acquisition of an invasive phenotype is a prerequisite for metastasization, yet it is not clear whether or to which extent the invasive phenotype is linked to other features characteristic of metastatic cells. We selected an invasive subpopulation from the triple negative breast cancer cell line MDA-MB-231, performing repeated cycles of preparative assays of invasion through Matrigel covered membranes. The invasive sub-population of MDA-MB-231 cells exhibits stronger migratory capacity as compared to parental cells confirming the highly invasive potential of the selected cell line. Prolonged cultivation of these cells did not abolish the invasive phenotype. ArrayCGH, DNA index quantification and karyotype analyses confirmed a common genetic origin of the parental and invasive subpopulations and revealed discrete structural differences of the invasive subpopulation including increased ploidy and the absence of a characteristic amplification of chromosome 5p14.1-15.33. Gene expression analyses showed a drastically altered expression profile including features of apocrine breast cancers and of invasion related matrix-metalloproteases and cytokines. The invasive cells showed accelerated proliferation, increased apoptosis, and an altered pattern of chemo-sensitivity with lower IC50 values for drugs affecting the mitotic apparatus. However, the invasive cell population is significantly less tumorigenic in orthotopic mouse xenografts suggesting that the acquisition of the invasive capacity and the achievement of metastatic growth potential are distinct events.