The Landscape of Clonal Characteristics and Evolution with Clinical Implications in B Cell Non-Hodgkin's Lymphoma
Authors: Lu Shixin , Xu Zhouyi , Zhang Zhaoxun , Gu Yun , Zhang Shunjin , Gao Chuanshu , Zhang Liang , Wang Wei , Lu Zefeng , Wu Jinghua , Gao Zizhao , Wang Zhe , Liu Xiao 
Published: December 2024

Introduction: B cellNon-hodgkin's lymphoma accounts for more than 80% of total lymphomas, originating from malignant B cell or precursor with characteristic B cell receptor (BCR) gene rearrangement. However, its BCR clonal landscape and evolution in particular have not been well studied. Here we recruit more than 200 B-cell Non-hodgkin's lymphoma compromising 5 major types, to provide a comprehensive landscape and comparison of their clonal characteristics and evolution patterns, as well as associations with clinical outcomes by immune repertoire sequencing. In-depth analysis of different malignant BCR evolution patterns reveals novel insights on their correlations with survival. The characteristics identified would provide significant implications for risk stratification of B cell Non-hodgkin's lymphoma.

Methods: To determine the correlation of clonal characteristics, clonal evolution and V(H) gene replacement with clinical outcomes, multiplex PCR and high-throughput sequencing were performed on tumor tissue samples from 207 patients with 5 types of Non-hodgkin's lymphoma including 75 marginal zone lymphoma (MZL), 65 small cell lymphoma (SLL), 26 follicular lymphoma (FL), 21 mantle cell lymphoma (MCL) and 20 diffuse large B-cell lymphoma (DLBCL), to detect immunoglobulin heavy/light chain (IgH and IgK/L) rearrangement sequences.

Results: Greater than 90% (68/75) of MZL, greater than 95% (62/65) of SLL, 100% (26/26) of FL, 100% (21/21) of MCL and 85% (17/20) of DLBCL were identified clonal rearrangements of IgH or IGK/L genes. In these samples with IgH or IGK/L clonal rearrangements, 63.2% (43/68), 98.4% (61/62), 76.9% (20/26), 61.9% (13/21), and 88.2% (15/17) exhibited only IgH clonal rearrangements, respectively.

These 5 types of Non-hodgkin's lymphoma exhibited differentiated IGHV gene usage, somatic hyper mutation (SHM) and the length of complementary determining region 3 (CDR3) of IgH. MCL exhibited a significantly lower SHM rate (median rate: 0.67%, p=0.00042), while FL and MZL exhibited a significantly higher SHM rate (median rate: 8.71% and 6.78%, p= 0.00013). SLL with SHM mutated status (SHM&gt;2%) exhibited significantly longer PFS (p=0.0015) with a 10 years follow up. In addition, SLL with discordant SHM status (double productive rearrangements) exhibited analogously to SHM unmutated status (SHM&lt;=2%). A longer length of IGH-CDR3 (&gt;=18 amino acids) of SLL exhibited significantly shorter PFS (p=0.026) with a 10 years follow up when eliminating clonal rearrangements with IGHV4-34 samples. Additionally, shorter IGH-CDR3 length was associated with SHM mutated sample in SLL when eliminating clonal rearrangements with IGHV4-34 samples (p=0.0036). Besides, a longer length of IGH-CDR3 (&gt;=15 amino acids) of MZL also exhibited significantly shorter PFS (p=0.038) with a 5 years follow up, and the lesser length of IGH-CDR3 (&lt;15 amino acids) MZL exhibited completely progression-free survival within 5 years.

Clonal evolution was identified in all IgH rearrangement positive samples. These 5 types of Non-hodgkin's lymphoma exhibited differentiated number of evolutional subclones. We built a model to differentiate two groups by the number of unique evolutional subclones. MZL with lesser unique evolutional subclones exhibited completely progression-free survival, and with greater unique evolutional subclones exhibited significantly shorter PFS (p=0.012) with a 5 years follow up. In contrast, MZL with V(H) gene replacement subclones exhibited significantly shorted PFS (p=0.0037) with a 5 years follow up.

Conclusion: This study provides a landscape and reveals the BCR clonal characteristics and evolution are associated with clinical outcomes in B cell Non-hodgkin's lymphoma. Shorter IGH-CDR3 length correlated with favorable prognosis in SLL and MZL, which gains insight into risk stratification. Importantly, patients with greater unique evolutional subclones are significantly associated with poorer prognosis, which implies a higher level of clonal evolution in malignant B cells as a high-risk factor. In summary, these clonal characteristics and evolution shed new insights on significant implications for risk stratification and may aid in molecular classification in B cell Non-hodgkin's lymphoma.