Low PKCα expression within the MRD-HR stratum defines a new subgroup of childhood T-ALL with very poor outcome

// Gloria Milani 1 , Paola Rebora 2 , Benedetta Accordi 1 , Luisa Galla 1 , Silvia Bresolin 1 , Gianni Cazzaniga 3 , Barbara Buldini 1 , Rossella Mura 4 , Saverio Ladogana 5 , Eugenia Giraldi 6 , Valentino Conter 7 , Geertruy Te Kronnie 1 , Maria Grazia Valsecchi 2 and Giuseppe Basso 1 1 Laboratory of Oncohematology, Department of Women’s and Children’s Health, University of Padova, Italy 2 Center of Biostatistics for Clinical Epidemiology, Department of Health Sciences, University of Milano-Bicocca, Monza, Italy 3 Centro Ricerca Tettamanti, University of Milano-Bicocca, Ospedale San Gerardo, Monza, Italy 4 Oncoematologia Pediatrica e Patologia della Coagulazione, Ospedale Regionale per le Microcitemie, Cagliari, Italy 5 Oncoematologia Pediatrica, Ospedale “Casa Solievo della Sofferenza”, San Giovanni Rotondo, Italy 6 U.O. Pediatria, Ospedale Papa Giovanni XXIII, Bergamo, Italy 7 Pediatric Department, University of Milano-Bicocca, Ospedale San Gerardo, Monza, Italy Correspondence: Geertruy te Kronnie, email: // Keywords : Low PKCα expression, Childhood T-cell Acute Lymphoblastic Leukemia, T-ALL prognostic marker Received : April 8, 2014 Accepted : June 5, 2014 Published : June 6, 2014 Abstract Pediatric T-cell Acute Lymphoblastic Leukemia (T-ALL) outcome has improved in the last decades, yet one patient in every four still relapses. Except treatment response and immunophenotype, few markers are reliably prognostic in pediatric T-ALL patients. Aiming to improve T-ALL risk stratification, we investigated a new candidate biomarker with potential prognostic relevance.  A phosphoproteomic screening of 98 pediatric T-ALL samples at diagnosis had been performed using the high-throughput Reverse Phase Protein Arrays technique, which led to the identification of PKCαS657 as an activated protein with a broad variation among T-ALL samples.  To evaluate PKCα potential as a prognostic biomarker, PKCα expression was analyzed using RQ-PCR in a cohort of 173 patients, representative of ALL2000-ALLR2006 AIEOP study. A threshold of PKCα expression with the highest discrimination for incidence of relapse was identified. Patients with PKCα down-regulation, compared to patients with PKCα levels above the threshold, presented a markedly increased cumulative incidence of relapse (43.8% vs. 10.9%, P<0.001), as well as a worse 4-year overall survival (66% vs. 87.9%, P=0.002) and event-free survival (53.1% vs. 85.2%, P=0.002). In particular, low PKCα expression identified cases with extremely poor outcome within the high-risk minimal residual disease (MRD) stratum, their incidence of relapse being of 69% vs. 15% in the high PKCα levels group.  In a multivariate analysis adjusting for main prognostic features, PKCα proved to be an independent prognostic factor related to incidence of relapse. Very high risk patients within the high-risk MRD stratum, identified by PKCα expression, could be proposed for experimental therapeutic protocols.