Abeykoon, Jithma P.

Abstract Advances in the treatment of Langerhans cell histiocytosis (LCH) have resulted in a growing survivor population. There is a lack of data on long-term outcomes among adults with LCH. We conducted a retrospective record review of 219 adults (aged ≥18 years) with LCH. Most common presentation was multisystem (34.2%), followed by single-system pulmonary (32%), unifocal (28.3%), and single-system multifocal (5.5%) LCH. Risk organ involvement (the liver, spleen, or bone marrow) was seen in 8.7% of cases, and 40 of 88 (45.5%) tested cases were BRAFV600E. At a median follow-up of 74 months, 5-year progression-free survival (PFS) was 58.3% and estimated median PFS was 83 months. Median overall survival (OS) was not reached; 5- and 10-year OS rates were 88.7% and 74.5%, respectively. Risk organ involvement was associated with worse PFS (hazard ratio [HR], 4.5) and OS (HR, 10.8). BRAFV600E was not associated with risk organ involvement or survival. When compared with matched unaffected US population, individuals with LCH had a significantly higher risk of overall mortality (standardized mortality ratio [SMR], 2.66), specifically among those aged <55 years at diagnosis (SMR, 5.94) and those with multisystem disease (SMR, 4.12). Second cancers occurred in 16.4% cases, including diverse hematologic and solid organ malignancies. LCH-associated deaths constituted 36.1% of deaths and occurred within 5 years of diagnosis. After 5 years, non-LCH causes of death, including second cancers, chronic obstructive pulmonary disease, and cardiovascular diseases, predominated. Our study highlights, to our knowledge, for the first time, that adults with LCH experience early and late mortality from non-LCH causes and the need for development of targeted survivorship programs to improve outcomes.

Abstract In this retrospective study, BRAF mutation status did not correlate with disease extent or (event-free) survival in 156 adults with Langerhans cell histiocytosis. BRAFV600E was associated with an increased incidence of second malignancies, often comprising hematological cancers, which may be clonally related.

Abstract Lymphoma is the sixth most commonly diagnosed cancer in the US. Genome-wide association studies have identified common variants associated with risk of specific lymphoma subtypes, but less is known about the contribution of rare inherited variants in the genetic architecture of lymphoma risk. CHEK2 is important to DNA repair and 2 small studies have found evidence of an association between CHEK2 variants and risk of lymphoma. Here, we investigated loss of function (LoF) variants in CHEK2 with risk of lymphoma (overall and subtypes). The study population included newly diagnosed lymphoma cases from Mayo who were enrolled in the Lymphoma SPORE Molecular Epidemiology Resource (MER). Controls were from the Mayo Clinic Biobank, from which we excluded a prior hematologic malignancy. Whole exome sequencing was performed by Regeneron on an Illumina NovaSeq panel (mean coverage of 48X). Variants were called using GATK v4 and variant annotation was performed using BioR. All LoF variants (nonsense, frameshift and consensus splice sites) in CHEK2 with a minor allele frequency < 0.5% were included in the analyses. Logistic regression was used to estimate odds ratio (OR) and 95% confidence intervals (CI) for the association between CHEK2mutation status and risk of lymphoma overall, and by lymphoma subtypes that had more than 5 mutation carriers, which included diffuse large B-cell (DLBCL), follicular (FL), and T-cell lymphoma (TCL). All analyses were adjusted for age (at diagnosis for cases and at enrollment for controls) and sex. A total of 4,852 lymphoma cases and 49,724 controls were included in this analysis. Median age for both cases and controls was 62 years (range 18-99 years). Males accounted for 57.5% (n=2,789) of the cases and 40.6% (n=20,186) of the controls. The DLBCL (23.6% of cases) and FL (23.3% of cases) subtypes were the most common; 7.6% of cases had TCL. A total of 407 (0.7%) individuals had a LoF variant. The frequency of LoF variants was 1.2% in lymphoma cases and 0.7% in controls. LoF variants were associated with increased risk of lymphoma overall (OR=1.77; 95%CI: 1.32-2.33), DLBCL (OR=2.07; 95%CI: 1.20-3.13), and TCL (OR=2.78; 95%CI: 1.178-5.50), but not FL (OR=1.31; 95%CI: 0.65-2.34). CHEK2 c.1100delC was the most frequently mutated variant in this population, accounting for 76% of all LoF variants. Individuals with a c.1100delC variant had an increased risk of lymphoma overall (OR=1.90; 95%CI: 1.37-2.58), DLBCL (OR=2.06; 95%CI: 1.09-3.54), and TCL (OR=3.17; 95%CI:1.24-6.58), but not FL (OR=1.05; 95%CI: 0.41-2.15). When restricted to cases, there was no significant difference in age at diagnosis (P=0.62) or sex (P=0.53) between LoF variant carriers and non-carriers. In this large lymphoma case-control study, CHEK2 LoF variants were associated with increased risk of lymphoma, demonstrating that rare inherited variants may play an important role in the etiology of lymphoma. Additional work is needed to investigate missense variants in CHEK2 and risk of lymphoma. Citation Format: Nicholas J. Boddicker, Raphael Mwangi, Dennis P. Robinson, Allison C. Rosenthal, Thomas M. Habermann, Andrew L. Feldman, Lisa M. Rimsza, Rebecca L. King, Melissa C. Larson, Brianna J. Gysbers, Stephen M. Ansell, Jithma P. Abeykoon, Grzegorz S. Nowakowski, Thomas E. Witzig, Anne J. Novak, Susan L. Slager, James R. Cerhan. Germline CHEK2 variants and risk of lymphoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5233.

Abstract Introduction: Cytokines are protein factors that regulate diverse cellular processes. The malignant progression of immunoglobulin M monoclonal gammopathy of undetermined significance (IgM-MGUS) to Waldenstrom macroglobulinemia (WM) is in part cytokine mediated, and we have previously shown IL-6 mediates IgM secretion in WM via the JAK/STAT pathway. Cytokine signaling can be epigenetically modulated by micro-RNAs (miRs). We aimed to identify the role of miRs in the regulation of inflammatory cytokine pathways between these diseases. Methods: Bone marrow samples of patients with IgM-MGUS (n=7) and WM (n=25) were prospectively collected and sorted for CD19+ and/or CD138+ malignant cells. Total RNA extraction and sequencing were performed, miR and mRNA profiling was conducted, and differential expression was calculated between WM and IgM-MGUS using a log2 fold change (FC)>0.5 and ←0.5, false discovery rate<0.05. Experimental differentially expressed miR-mRNA pairing was performed, and pairs were filtered for correlated expression (i.e., upregulated miR/downregulated mRNA, and vice-versa). Filtered pairs were analyzed using the Ingenuity Pathway Analysis to identify pathways between WM and IgM-MGUS with absolute activation Z-score ≥1. Results: We identified 34 differentially expressed miRs experimentally targeting 1132 mRNAs. Pathway analysis showed overall miR-based inactivation of inflammatory cytokine signaling pathways in WM compared to IgM-MGUS, especially of the interleukin (IL) family: IL-2, IL-6, IL-8, IL-9, IL-15, and IL-17. Underlying multiple pathways was upregulation of miRs-146a, 150, 194, all targets of Signal Transducer and Activator of Transcription 1 (STAT1), observed to be downregulated. Of relevance, miR-146a has been previously shown to be an inhibitor of inflammatory cytokines, including IL-6. Next, we observed upregulation of miR-142 which targets phosphoinositide-3-kinase regulatory subunit 6 (PIK3R6), observed to be downregulated. Both the STAT and PIK3 families are important cytokine signal transducers, and we have previously shown the PI3k-AKT-IkB-p65 pathway induces expression of IL-6 via a GLI2-mediated mechanism. We additionally observed granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling to be inactivated in WM. Here, miR-19b and miR-30e were upregulated, both target CSF 2 receptor subunit beta (CSF2RB), found to be downregulated. CSF2RB is the common receptor subunit of GM-CSF, IL-3, and IL-5. Conclusion: Our study identifies multiple cytokines pathways involved in inflammation and the tumor microenvironment to be potentially inactivated by differentially expressed miRs in WM compared to IgM-MGUS. Downregulation of these pathways and targeting of the STAT and PIK3 family indicates a possible miR-based negative feedback loop to down-modulate inflammatory cytokine signaling in WM. Citation Format: Karan Chohan, Jonas Paludo, Surendra Dasari, Jithma P. Abeykoon, Prashant Kapoor, Esteban Braggio, Michelle K. Manske, Aneel Paulus, Craig B. Reeder, Sikander Ailawadhi, Asher A. Chanan-Khan, Robert A. Kyle, Morie A. Gertz, Anne J. Novak, Stephen M. Ansell. Micro-RNA induced inactivation of inflammatory cytokine signaling pathways in Waldenstrom macroglobulinemia compared to IgM-MGUS. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3811.

Abstract Objectives Understanding of histiocytic disorders has been revolutionized by demonstration of mitogen-activated protein kinase (MAPK) pathway mutations, most commonly BRAFV600E. The optimal testing strategy to assess BRAFV600E is unknown. We aimed to compare performance of testing modalities, to propose a framework for evaluation of BRAFV600E mutation status in histiocytic disorders. Methods We retrospectively reviewed patients with histiocytic disorders and BRAF mutation testing on a lesional tissue specimen. Results In 120 patients, BRAF assessment included immunohistochemistry (IHC) in 97 (80.2%), polymerase chain reaction (PCR) in 35 (28.9%), and next-generation sequencing (NGS) in 62 (51.2%). Forty-five underwent both NGS and IHC. With NGS as the gold standard, the sensitivity and specificity of IHC were 82.4% and 96.4%. Three false negatives were observed in biopsy specimens with low BRAFV600E variant allele frequency or decalcified tissue. One false-positive IHC was observed in a lung biopsy specimen, likely due to antibody cross-reactivity with respiratory cilia. Among 14 with successful NGS and PCR, a single discordance was observed. Two PCR-to-IHC discrepancies were observed, including one other false-positive IHC. Conclusions Immunohistochemistry was highly specific for detection of BRAFV600E. Main caveats were false negatives and lack of detection of non-BRAFV600E mutations. We propose the use of IHC as initial screening in general practice with reflex molecular testing if negative.