Host genetics in follicular lymphoma

Causal relationship between circulating cytokines and follicular lymphoma: a two-sample Mendelian randomization study

Follicular lymphoma (FL), derived from germinal centre (GC) B cells, is a kind of systemic neoplasm. Even though FL is indolent, it remains an incurable haematology Neoplasm. Accumulating evidence has suggested that the circulating cytokine is associated with the development of FL, yet the causal relationship between FL and circulating cytokines remains undetermined. Therefore, we conducted a two-sample Mendelian randomization (MR) to confirm the causal link between FL and levels of circulating cytokines with the use of summary data on circulating cytokines and FL. All these data from genome-wide association study were derived from the Genome-wide pQTL mapping which contains 14,824 individuals. FL data were acquired exclusively from FinnGen, where 218,792 individuals (522 cases vs. 218,270 controls) were involved. Various statistical methods, including the inverse variance weighted method (IVW), weighted median (WME), simple model, weighted model (WM) and MR-Egger, were used to evaluate the potential causal connection between circulating cytokines and FL. Sensitivity analysis, which involves the examination of the heterogeneity, pleiotropy, and leave-one-out method, was also performed to ensure more trustworthy results. A bidirectional MR test was performed to evaluate the direction of causal association between circulating cytokines and FL. Combining all the steps of MR analysis, we revealed four causal cytokines: C-X-C motif chemokine ligand 5 (CXCL5), interleukin-15 receptor A (IL15RA), interleukin-20 (IL20), and neurotrophin-3 (NT-3). The risk of FL may be inversely linked to CXCL5 (OR=0.73, CI: 0.545-0.979, P=0.036), IL-15RA (OR=0.669, CI: 0.451-0.993, P=0.046), and IL-20 (OR=0.565, CI: 0.325-0.981, P=0.043) but positively linked to NT-3 (OR=1.872, CI: 1.063-3.297, P=0.03). In addition, in our study, no causal effect of FL on cytokines was demonstrated and no significant heterogeneity and pleiotropy were found. Our research revealed the causal relationship between cytokines and FL, along with both the anti-protective effect of CXCL5, IL-15RA, and IL-20 and the protective effect of neurotrophin-3 on FL. These findings aim to provide new clues regarding the pathogenesis of FL and to extend the potential of circulating cytokines to therapeutic interventions.

Epidemiology of Follicular Lymphoma

Follicular lymphoma (FL) is a common indolent lymphoma subtype in Western countries. FL incidence increases with age, and shows considerable variation by race/ethnicity and geography. In the United States and France, FL incidence has been stable since 2000, whereas in other Western and Asian countries it has been increasing. Five-year relative survival rates have been increasing in Western and Asian countries. Progress on identifying FL-specific risk factors has accelerated with the implementation of the InterLymph nested classification and the availability of larger epidemiologic studies and pooled analyses. Identification of risk factors for FL requires further research.

Familial predisposition and genetic risk factors for lymphoma

Our understanding of familial predisposition to lymphoma (collectively defined as non-Hodgkin lymphoma [NHL], Hodgkin lymphoma [HL], and chronic lymphocytic leukemia [CLL]) outside of rare hereditary syndromes has progressed rapidly during the last decade. First-degree relatives of NHL, HL, and CLL patients have an ∼1.7-fold, 3.1-fold, and 8.5-fold elevated risk of developing NHL, HL, and CLL, respectively. These familial risks are elevated for multiple lymphoma subtypes and do not appear to be confounded by nongenetic risk factors, suggesting at least some shared genetic etiology across the lymphoma subtypes. However, a family history of a specific subtype is most strongly associated with risk for that subtype, supporting subtype-specific genetic factors. Although candidate gene studies have had limited success in identifying susceptibility loci, genome-wide association studies (GWAS) have successfully identified 67 single nucleotide polymorphisms from 41 loci, predominately associated with specific subtypes. In general, these GWAS-discovered loci are common (minor allele frequency >5%), have small effect sizes (odds ratios, 0.60-2.0), and are of largely unknown function. The relatively low incidence of lymphoma, modest familial risk, and the lack of a screening test and associated intervention, all argue against active clinical surveillance for lymphoma in affected families at this time.

Follicular lymphoma-protective HLA class II variants correlate with increased HLA-DQB1 protein expression

Multiple follicular lymphoma (FL) susceptibility single-nucleotide polymorphisms in the human leukocyte antigen (HLA) class I and II regions have been identified, including rs6457327, rs3117222, rs2647012, rs10484561, rs9268853 and rs2621416. Here we validated previous expression quantitative trait loci results with real-time reverse transcription quantitative PCR and investigated protein expression in B-lymphoblastoid cell lines and primary dendritic cells using flow cytometry, cell-based enzyme-linked immunosorbent assay and western blotting. We confirmed that FL-protective rs2647012-linked variants, in high linkage disequilibrium with the extended haplotype DRB1*15:01-DQA1*01:02-DQB1*06:02, correlate with increased HLA-DQB1 expression. This association remained significant at the protein level and was reproducible across different cell types. We also found that differences in HLA-DQB1 expression were not related to changes in activation markers or class II, major histocompatibility complex, transactivator expression, suggesting the role of an alternative regulatory mechanism. However, functional analysis using RegulomeDB did not reveal any relevant regulatory candidates. Future studies should focus on the clinical relevance of increased HLA-DQB1 protein expression facilitating tumor cell removal through increased immune surveillance.

Lifestyle factors, autoimmune disease and family history in prognosis of non-hodgkin lymphoma overall and subtypes

Lifestyle factors and medical history are known to influence risk of non-Hodgkin lymphoma (NHL). Whether these factors affect the prognosis of NHL, especially its subtypes, is unclear. To investigate this, the association between these factors and all-cause and lymphoma-related mortality was assessed in a population-based cohort of 1,523 Swedish NHL patients included in the Scandinavian Lymphoma Etiology study in 1999-2002. Participants contributed time from NHL diagnosis until death or October 1, 2010, with virtually complete follow-up through linkage to the Swedish Cause of Death Register. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using stratified and multivariable-adjusted Cox regression models. During a median follow-up of 8.8 years, 670 patients (44%) died, with the majority of deaths attributed to lymphoma (86%). Current versus never smoking at diagnosis was associated with increased rate of all-cause death for all NHL (HR = 1.5, 1.2-1.8) and diffuse large B-cell lymphoma (HR = 1.8, 1.2-2.7). Low educational level (HR = 1.3, 1.1-1.7, <9 vs. >12 years) and NHL risk-associated autoimmune disease (HR = 1.4, 1.0-1.8) were associated with death for all NHL combined. However, evidence of an association with lymphoma-related death was limited. Body mass index, recent sunbathing and family history of hematopoietic malignancy were not consistently associated with death after NHL or its specific subtypes. These results add to the evidence that cigarette smoking, socioeconomic status and certain autoimmune diseases affect survival after NHL. Further investigations are needed to determine how these factors should be incorporated into clinical prognostic assessment.