Abstract
Recently, mantle cell lymphoma (MCL) has been recognized as a heterogeneous clinical and biological entity, as molecular genetics highlighted different pathways of cell survival and progression. Histological diagnosis may be challenging due to atypical MCL variants, immunophenotyping or absence of cyclin D1 (D1), encountered in 10% of cases. SOX11 is a neural transcription factor, involved in blocking mature B cell differentiation and its overexpression is associated with poor prognosis. It is overexpressed in most conventional MCL (cMCL) and in MCL lacking D1 overexpression, but not detected in other mature B cell lymphomas or normal lymphoid cells. Recently, its overexpression has been considered as a specific biomarker for MCL diagnosis.
Development of novel targeted therapy approaches renders monitoring of minimal residual disease (MRD) essential to assess treatment effectiveness. Amongst methods developed to monitor MRD, allele-specific oligonucleotide quantitative PCR for BCL1 or IgH, is the most sensitive and commonly used approach. Given the role of SOX11 and BCL1 in the pathophysiology of MCL, we developed an easy set up single step quantitative PCR (qPCR) to assess both markers simultaneously, which was tested on a large panel of MCL patients at diagnosis and MRD monitoring.
A reverse transcription qPCR protocol was carried out to quantify SOX11, cyclin D1 and D2 overexpression simultaneously, using specific primers, Taqman probes and B2M house keeping gene (LC480, Roche). RNA was extracted from peripheral blood (PB), bone marrow (BM) and lymph nodes (LN). Sensitivity was determined using 6 fold dilutions starting with 1:10 from 30 subjects with normal lymphocytes. A retrospective study on a total of 170 samples for 145 patients between 2002 and 2017 was conducted. Samples were chosen based on morphology, immunophenotyping and histopathology if available. All samples were CD20+, 162 were CD5+ and 165 were CD10-. All patients had provided an informed written consent in accordance with the declaration of Helsinki. We tested 93 patients with MCL at diagnosis, 79 cMCL and 14 indolent mantle cell lymphoma (iMCL). To assess specificity 52 patients with other lymphoid proliferations CD5/20+, CD10- were studied. 20 samples from 5 patients SOX11+/D1+ were available for MRD monitoring.
Sensitivity of the method achieved 1.10-4. At diagnosis, tumor cells ranged between 11-97% of total lymphocytes in PB and 1-91% in BM. SOX11 and D1 overexpression was correlated with the tumor burden. 79/79 cMCL patients (100%) overexpressed SOX11 and D1 (SOX11+/D1+), 2 cMCL were CD5-, SOX11+/ D1+ and 2 cMCL were CD10+, SOX11 +/ D1+. All 14 iMCL patients were (SOX11-/D1+). Sox 11 was not detected in normal lymphocytes or in other lymphoproliferative diseases. 5 patients presented with the blastoid variant, overexpressed SOX11, but only 4 overexpressed D1 and tumor infiltration rate at diagnosis was over 83% in PB. MRD follow up showed negativity of both markers for 2 patients at complete remission. SOX11 overexpression was detected before cyclin D1 in 2 patients at relapse, prior to clinical manifestations. Persistent SOX11 and D1 overexpression was observed for 1 splenctomized patient. Time to treatment was found to be 0.6 vs 18 months in 18 cMCL and 12 iMCL patients respectively (p= 0.0006). CD43 was evaluated for 27 patients, 4 blastoid variants and 23 cMCL. 100% of blastoid variants were positive for CD43, but only 43.4% of cMCL were positive for CD43 (p=0.0368). Overall survival curve for CD43 positive patients showed a median of 2.3 years survival (p=0.0285). This was not reached for the CD43 negative MCL.
We developed a feasible single step sensitive method to quantify SOX11, D1 and D2 in MCL which allows differential diagnosis with other lymphoid proliferations. A parallel correlation was found between SOX11, D1 and clinical status of MCL during diagnosis and follow up. As histopathology is unsuitable for MRD evaluation, both markers could be used to assess MRD, though SOX11 is preferred to D1 as it lacks the D1 background overexpression. Considering the higher sensitivity of molecular MRD compared to conventional evaluating procedures, its integration in guided treatment strategies is warranted. To the best of our knowledge, this is the first report stating the association of CD43 with adverse prognosis in MCL which might be interesting as a prognostication marker and a target for a novel immunotherapy development.
Troussard: ROCHE: Honoraria; GILEAD: Honoraria; JANSSEN: Honoraria; ABBVIE: Honoraria.
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