Protein Expression And Gene Abnormalities Of Bcl-2, Bcl-6, And C-Myc:Evaluation Of Their Prognostic Significance In Patients With Lymphoblastic Lymphoma

ObjectiveLymphoblastic lymphoma(LBL) is a neoplasm of immature or precursor lymphoid cells. It belongs to a rare high-grade pattern of non-Hodgkin’s lymphoma (NHL), which accounts for2%of all NHL. LBL is an aggressive entity most commonly occurring in adolescents and young adults. Because of limited data available in the literature, the etiology of LBL remains uncertain. Is the expression of typical protein abnormal in patients with LBL? Are genetic abnormalities regular in them? Do they have prognostic factors for clinical practice? It is reported that bcl-2, bcl-6and c-myc rearrangements are the most common genetic abnormalities in NHL. Therefore, we hypothesized that they might play an important part in the pathogenesis of LBL because of their role in the regulation of cell proliferation, apoptosis and carcinogenesis. In China, there have been no extensive studies in the literature of protein expression and genetic abnormalities on bcl-2, bcl-6and c-myc in LBL. Thus, we aimed to investigate protein expression and genetic abnormalities of them, especially focus on the correlation of protein levels with gene aberration. Moreover, the prognostic significance of them was further analyzed in LBL.MethodsForty-one lympho node tissue samples of LBL were collected from the Tianjin Medical University Cancer Institute and Hospital from March1999to May2011. The representative cores originated from each tissue sample were constructed into tissue microarrays which were prepared for H&E staining, immunohistochemistry(IHC) and fluorescence in situ hybridization(FISH). IHC staining was performed to evaluate protein expression, including Bcl-2, Bcl-6, c-Myc, TdT, CD1α, CD34, Ki-67, PAX-5, CD20, CD2, CD3, CD4, and CD8. Genetic abnormalities of bcl-2, bcl-6and c-myc were detected by dual color FISH, including gene rearrangement, gain and loss. After a period of follow-up, the survival curves were estimated by Kaplan-Meier method. The prognostic influence of variables on survival was assessed using the log-rank test. Finally, the prognostic factors were analyzed for LBL ResultsThe protein levels of c-Myc ranged from5%to92%, and the median was42%. The c-Myc protein was positive in32(78.0%) patients with LBL. The protein levels of Bcl-2ranged from3%to93%, and the median was38%. The Bcl-2protein was positive in21(51.2%) patients. The protein levels of Bcl-6ranged from2%to42%, and the median was8%. The Bcl-6protein was positive in3(7.3%) patients. Among41LBL patients, genetic abnormalities were found in10(24.4%) cases. Moreover, bcl-2breakpoints were found in2cases with concurrent gene gain of bcl-6and c-myc. There was no evidence of bcl-6or c-myc rearrangement in patients with LBL. However, both gene gain and loss events occurred in bcl-2, bcl-6, and c-myc. Gene gain of bcl-2was observed in3(7.3%) cases. The gene gain of bcl-6and c-myc were found in2(4.9%), and6cases(14.6%), respectively. Another2(4.9%),1(2.4%), and2cases(4.9%) were found to be gene loss of bcl-2, bcl-6, and c-myc, respectively. However, no correlation was found between IHC and FISH results on them(p>0.05).Univariate analysis showed that stage Ⅲ or IV, elevated LDH, and positivity for bcl-2protein were associated with shorter survival(p<0.05). However, other clinicopathological parameters could not predict clinical outcomes in patients with LBL, including age, gender, immunophenotype, central nervous system disease, bone marrow involvement, protein expression of bcl-6and c-myc, and the genetic abnormalities of bcl-2, bcl-6and c-myc. All patients were ultimately classified into3distinct groups according to the number of adverse prognostic factors. The patients with more adverse factors would have increasingly worse prognosis(p<0.05).ConclusionsEnhanced protein expression and detectable genetic abnormalities of bcl-2, bcl-6, and c-myc were observed in patients with LBL. No statistical correlation was found between IHC results and FISH findings. Stage Ⅲ or IV, elevated LDH, and positivity for bcl-2protein were identified as adverse prognostic factors. The patients with more adverse factors would have increasingly worse prognosis.