Hairy Cell Research Articles

CLL-237 Efficacy of Cladribine Combine With Rituximab versus Cladribine Alone in the Treatment of Hairy Cell Leukemia: A Retrospective Single-Center Study

CLL-237 Efficacy of Cladribine Combine With Rituximab versus Cladribine Alone in the Treatment of Hairy Cell Leukemia: A Retrospective Single-Center Study

Improving the cytotoxicity of immunotoxins by reducing the affinity of the antibody in acidic pH

BackgroundImmunotoxins are antibody-toxin conjugates that bind to surface antigens and exert effective cytotoxic activity after internalization into tumor cells. Immunotoxins exhibit effective cytotoxicity and have been approved by the FDA to treat multiple hematological malignancies, such as hairy cell leukemia and cutaneous T-cell lymphoma. However, most of the internalized immunotoxin is degraded in lysosomes, and only approximately 5% of free toxin escapes into the cytosol to exert cytotoxicity. Many studies have improved immunotoxins by engineering the toxin fragment to reduce immunogenicity or increase stability, but how the antibody fragment contributes to the activity of immunotoxins has not been well demonstrated.MethodsIn the current study, we used 32A9 and 42A1, two anti-GPC3 antibodies with similar antigen-binding capabilities and internalization rates, to construct scFv-mPE24 immunotoxins and evaluated their in vitro and in vivo antitumor activities. Next, the antigen-binding capacity, trafficking, intracellular protein stability and release of free toxin of 32A9 scFv-mPE24 and 42A1 scFv-mPE24 were compared to elucidate their different antitumor activities. Furthermore, we used a lysosome inhibitor to evaluate the degradation behavior of 32A9 scFv-mPE24 and 42A1 scFv-mPE24. Finally, the antigen-binding patterns of 32A9 and 42A1 were compared under neutral and acidic pH conditions.ResultsAlthough 32A9 and 42A1 had similar antigen binding capacities and internalization rates, 32A9 scFv-mPE24 had superior antitumor activity compared to 42A1 scFv-mPE24. We found that 32A9 scFv-mPE24 exhibited faster degradation and drove efficient free toxin release compared to 42A1 scFv-mPE24. These phenomena were determined by the different degradation behaviors of 32A9 scFv-mPE24 and 42A1 scFv-mPE24 in lysosomes. Moreover, 32A9 was sensitive to the low-pH environment, which made the 32A9 conjugate easily lose antigen binding and undergo degradation in lysosomes, and the free toxin was then efficiently produced to exert cytotoxicity, whereas 42A1 was resistant to the acidic environment, which kept the 42A1 conjugate relatively stable in lysosomes and delayed the release of free toxin.ConclusionsThese results showed that a low pH-sensitive antibody-based immunotoxin degraded faster in lysosomes, caused effective free toxin release, and led to improved cytotoxicity compared to an immunotoxin based on a normal antibody. Our findings suggested that a low pH-sensitive antibody might have an advantage in the design of immunotoxins and other lysosomal degradation-dependent antibody conjugate drugs.

Genetic Variations in Hairy Cell Leukemia with Brain Involvement: Case Report

Genetic Variations in Hairy Cell Leukemia with Brain Involvement: Case Report

Deceptive Presentation of Low-Grade Lymphoma with Grade 3 Marrow Fibrosis and Aplasia: Diagnostic and Clinical Considerations

AbstractBone marrow fibrosis with lymphoproliferative disorders is rare with the exception of hairy cell leukemia and nodular sclerosis Hodgkin's lymphoma. We report the case of a 63-year-old gentleman with indolent B-cell lymphoma presenting with myelofibrosis and aplasia. He was evaluated for pancytopenia with no organomegaly or lymphadenopathy. Bone marrow aspiration was a dry tap and biopsy revealed a hypocellular marrow with a cellularity of 10 to 20% with absent megakaryocytes and grade 2 to 3 reticulin fibrosis. Myeloproliferative neoplasms were ruled out based on morphology and absence of myeloid mutations on next-generation sequencing. Further sections revealed interstitial infiltrates of lymphoid cells with round, clumped chromatin and inconspicuous nucleoli, which on immunohistochemistry (IHC) were positive for CD20 and BCL2, and negative for CD5, CD10, BCL6, annexin A1, cyclin D1, and TdT. The final diagnosis was thus confirmed as CD5-negative low-grade B-cell lymphoma and he was initiated on therapy with a combination of Bendamustine and Rituximab. He had resolution of symptoms and cytopenia after six cycles of the same. Presence of significant myelofibrosis on the background of a hypocellular marrow can mimic several subtypes of myeloproliferative neoplasms or myelodysplastic syndromes, providing a diagnostic challenge. IHC is essential in determining the exact subtype to decide further therapy. Based on literature search, only a handful of patients with this presentation have been described and this case will be a valuable addition to the same.

BRAF(V600E) mutation together with loss of Trp53 or pTEN drives the origination of hairy cell leukemia from B-lymphocytes

Hairy cell leukemia (HCL) is a B-lymphoma induced by BRAF(V600E) mutation. However, introducing BRAF(V600E) in B-lymphocytes fails to induce hematological malignancy, suggesting that BRAF(V600E) needs concurrent mutations to drive HCL ontogeny. To resolve this issue, here we surveyed human HCL genomic sequencing data. Together with previous reports, we speculated that the tumor suppressor TP53, P27, or PTEN restrict the oncogenicity of BRAF(V600E) in B-lymphocytes, and therefore that their loss-of-function facilitates BRAF(V600E)-driven HCL ontogeny. Using genetically modified mouse models, we demonstrate that indeed BRAF(V600E)KI together with Trp53KO or pTENKO in B-lymphocytes induces chronic lymphoma with pathological features of human HCL. To further understand the cellular programs essential for HCL ontogeny, we profiled the gene expression of leukemic cells isolated from BRAF(V600E)KI and Trp53KO or pTENKO mice, and found that they had similar but different gene expression signatures that resemble that of M2 or M1 macrophages. In addition, we examined the expression signature of transcription factors/regulators required for germinal center reaction and memory B cell versus plasma cell differentiation in these leukemic cells and found that most transcription factors/regulators essential for these programs were severely inhibited, illustrating why hairy cells are arrested at a transitional stage between activated B cells and memory B cells. Together, our study has uncovered concurrent mutations required for HCL ontogeny, revealed the B cell origin of hairy cells and investigated the molecular basis underlying the unique pathological features of the disease, with important implications for HCL research and treatment.

Hairy cell leukaemia with unusual BRAF mutations.

Hairy cell leukaemia (HCL) diagnosis is based on the morphologic detection of circulating abnormal hairy cells in the peripheral blood and/or bone marrow, an HCL immunological score of 3 or 4 based on the expression of the CD11c, CD25, CD103 and CD123 and also the presence of a BRAF V600E activating mutation in the B-raf proto-oncogene (BRAF gene) (7q34). When using new generation sequencing of 21 targeted genes in 124 HCL patients, we identified a cohort of 6/124 (2%) patients with unusual BRAF mutations: two patients presented non-V600 mutations (BRAF F595L, BRAF W604L respectively) and four other patients silent BRAF mutations. When using droplet digital PCR (ddPCR) three of the four patients with concomitant BRAF V600E and silent mutation were negative. The respective role of these mutations in the occurrence of HCL or its progression remains to be clarified, but BRAF sequencing is necessary in case of negative BRAF V600E by ddPCR.

Phenolic compounds as potential adenosine deaminase inhibitors: molecular docking and dynamics simulation coupled with MM-GBSA calculations.

Adenosine deaminase (ADA) is a Zn2+-containing enzyme that catalyzes the irreversible deamination of adenosine to inosine or deoxyadenosine to deoxyinosine. In addition to this enzymatic function, ADA mediates cell-to-cell interactions involved in lymphocyte co-stimulation or endothelial activation. ADA is implicated in cardiovascular pathologies such as atherosclerosis and certain types of cancers, including lymphoma and leukemia. To date, only two drugs (pentostatin and cladribine) have been approved for the treatment of hairy cell leukemia. In search of natural ADA inhibitors, we demonstrated the binding of selected phenolic compounds to the active site of ADA using molecular docking and molecular dynamics simulation. Our results show that phenolic compounds (chlorogenic acid, quercetin, and hyperoside) stabilized the ADA complex by forming persistent interactions with the catalytically essential Zn2+ ion. Furthermore, MM-GBSA ligand binding affinity calculations revealed that hyperoside had a comparable binding energy score (ΔG = -46.56 ± 8.26kcal/mol) to that of the cocrystal ligand in the ADA crystal structure (PDB ID: 1O5R) (ΔG = -51.97 ± 4.70kcal/mol). Similarly, chlorogenic acid exhibited a binding energy score (ΔG = -18.76 ± 4.60kcal/mol) comparable to those of the two approved ADA inhibitor drugs pentostatin (ΔG = -14.54 ± 2.25kcal/mol) and cladribine (ΔG = - 25.52 ± 4.10kcal/mol) while quercetin was found to have modest binding affinity (ΔG = - 8.85 ± 7.32kcal/mol). This study provides insights into the possible inhibitory potential of these phenolic compounds against ADA.

The course of patients with hairy cell leukemia during the omicron surge of the Covid-19 pandemic.

In this study, we aim to explore the outcomes of Covid-19 infection in patients with Hairy cell leukemia (HCL). The cohort is based on data obtained from electronic medical records. It includes 218 consecutive patients diagnosed with HCL between 16 June 1998, and 20 September 2022, out of which the coronavirus has infected 85 patients during the Omicron surge. Out of 85 patients with HCL who were infected by Covid-19; 7 patients (8.2%) have been hospitalized, and the mortality rate was 2.3% (two patients). Thirteen of the 85 patients had been infected by Covid-19 in previous waves, including 9/13 after vaccination, and none of them developed a severe disease. Humoral immune response after three doses of the BNT162b2 mRNA vaccination regimen was evaluated in 40 patients and was attained in 67.5%. Based on multivariate analysis: unfavorable outcome was significantly more common in patients with HCL above 65years old, who had at least one cytopenia, and with comorbidity of cardiovascular disease or asplenia. Our results indicates that the course of COVID-19 in patients with HCL during the Omicron wave has been improved relatively favorable.

Trends in risk for therapy-related myelodysplastic syndrome/acute myeloid leukemia after initial chemo/immunotherapy for common and rare lymphoid neoplasms, 2000-2018.

Historically, survivors of common lymphoid neoplasms (LNs) had increased risks for therapy-related myelodysplastic syndrome/acute myeloid leukemia (tMDS/AML). Despite major treatment advances in the treatment of LNs over the last two decades, a comprehensive evaluation of tMDS/AML trends following both common and rare LNs treated in this contemporary period is lacking. In US cancer registries during 2000-2018, we identified 1496 tMDS/AML cases among 186,503 adults who were treated with initial chemo/immunotherapy for first primary LN and survived ≥1 year. We quantified tMDS/AML standardized incidence ratios (SIRs), excess absolute risks (EARs, per 10,000 person-years), and cumulative incidence. The highest tMDS/AML risks occurred after precursor leukemia/lymphoma (SIR=39, EAR=30), Burkitt leukemia/lymphoma (SIR=20, EAR=24), peripheral T-cell lymphoma (SIR=12, EAR=23), chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL; SIR=9.0, EAR=27), and mantle cell lymphoma (SIR=8.5, EAR=25). Elevated risks (SIRs=4.2-6.9, EARs=4.9-15) also were observed after all other LN subtypes except hairy cell leukemia and mycosis fungoides/Sézary syndrome. Among patients treated more recently, tMDS/AML risks were significantly higher after CLL/SLL (SIR2000-2005=4.8, SIR2012-2017=10, Ptrend=0.0043), significantly lower after Hodgkin (SIR2000-2005=15, SIR2012-2017=6.3, Ptrend=0.024) and marginal zone (SIR2000-2005=7.5, SIR2012-2017=2.3, Ptrend=0.015) lymphomas, and non-significantly lower after mantle cell lymphoma (SIR2000-2005=10, SIR2012-2017=3.2, Ptrend=0.054), lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (SIR2000-2005=6.9, SIR2012-2017=1.0, Ptrend=0.067), and plasma cell neoplasms (SIR2000-2005=5.4, SIR2012-2017=3.1, Ptrend=0.051). EAR and cumulative incidence trends generally were similar to SIR trends. Median survival after tMDS/AML was 8.0 months (interquartile range, 3.0-22.0). Although tMDS/AML risks are significantly elevated after initial chemo/immunotherapy for most LNs, patients treated more recently have lower tMDS/AML risks, except after CLL/SLL. Though rare, the poor prognosis following tMDS/AML emphasizes the importance of continued efforts to reduce treatment-associated toxicity. This research was supported in part by the Intramural Research Program of the National Cancer Institute, National Institutes of Health. LMM, GMD, REC, and CBS verified the data, and all authors had access to the data and made the decision to submit for publication.

Untangling the Strands of Hairy Cell Leukemia: The Clinicopathological Spectrum over Eleven Years at a Tertiary Care Center.

Hairy Cell Leukemia (HCL) is an uncommon, indolent lymphoproliferative disorder of mature B lymphoid cells, accounting for 2% of all lymphoid tumors. The present study evaluated the clinical-hematological profile of HCL patients diagnosed at a single tertiary care center over a 11-year period. The retrospective observational study was done between October 2010 and September 2021. The relevant clinical and laboratory information were retrieved from hospital medical records and electronic databases. The statistical analysis was performed using version 23.0 of SPSS. 66 (5.9%) of 1125 cases of chronic lymphoproliferative disorder were HCL. Splenomegaly was found in 47 (71.2%), hepatomegaly in 26 (39.5%), and lymphadenopathy in 17 (25.7%) of the cases. The mean hemoglobin, total leukocytes count, and platelets count were 8.04 g/dl, 6.76 X 109/L, and 77 X 109/L, respectively. Pancytopenia was detected in 40 cases (60.61 %). Bone marrow biopsies were majorly hypercellular and showed predominantly diffuse infiltration by atypical lymphoid cells. In two patients, initially thought of having refractory/hypoplastic anemia, the bone marrow biopsy and flow cytometry revealed HCL involvement. 42 cases of HCL underwent flow cytometry. CD20, CD 11c, CD 25 and CD 103 were positive in all the cases. The aberrant expression of CD5, CD10, and CD23 was found in frequencies of 5.71 %, 31.42 %, and 19.35%, respectively. In 40 cases for which follow-up information was available, there was full remission in 26 patients (65%), and later three showed relapse (7.5%) of which one died, and persistent leukemic activity in five (10%). Eight patients (20%) died even before the initiation of treatment. One patient died within one month of therapy. No patient was examined for BRAF V600E mutation analysis. CD 10+ HCL was the most prevalent atypical immunophenotypic subgroup. Bone marrow biopsy and flow cytometry are crucial diagnostic tools to rule out hairy cell leukemia. However, BRAF V600E mutation analysis should be performed in cases with unusual presentation or resistance to treatment.

Hairy Cell Leukemia with Marrow Reactive Plasmacytosis and Mast Cell Hyperplasia: A Case Report and Brief Review of the Literature

Hairy cell leukemia (HCL) and HCL-like disorders, including HCL-variant, are disorders of heterogeneous mature lymphoid B-cells known for their hairy cell infiltration accompanied by a specific genetic profile, various clinical presentations, and, as they are uncommon hematological malignancies characterized by pancytopenia, the need for appropriate therapy. Sometimes HCL creates diagnostic challenges for clinicians, and its coincidence or association with mast cell and plasma cell infiltration is a rare condition. Herein, we report a case of HCL with confusing manifestations. A 44-year-old man was referred to the hospital for weakness, fatigue, and watery, non-bloody diarrhea. The laboratory tests showed pancytopenia, leading to a referral for bone marrow aspiration and biopsy. Medium to large cells exhibiting widespread cytoplasm, oval nuclei similar to monocyte nuclei (kidney-shaped) accompanied by an increased number of mast cells, and plasma cells were observed in the biopsy sample. In flow cytometry, the neoplastic cells were positive for CD19, FMC7, and the co-expression of the CD20/CD25, CD11C/CD22, and CD103 markers. In immunohistochemical staining, the mast cells were positive for CD117, the plasma cells were positive for CD138, and the hairy cells were positive for CD20. Overall, hematopathologists must be aware of various morphologic confounding factors such as lack of typical cell morphological features and increased plasma cell and mast cell infiltration in the diagnosis of patients with HCL.

Flow Cytometry of CD5-Positive Hairy Cell Leukemia.

Hairy cell leukemia (HCL) is a chronic lymphoproliferative disorder for which diagnosis is typically straightforward, based on bone marrow morphology and flow cytometry (FC) or immunohistochemistry. Nevertheless, variants present atypical expressions of cell surface markers, as is the case of CD5, for which the differential diagnosis can be more difficult. The aim of the current paper was to describe diagnosis of HCL with atypical CD5 expression, with an emphasis on FC. The detailed diagnostic methodology for HCL with atypical CD5 expression is presented, including differential diagnosis from other lymphoproliferative diseases with similar pathologic features, by FC analysis of the bone marrow aspirate. Diagnosis of HCL by means of FC started by gating all events based on side scatter (SSC) versus CD45 and B lymphocytes were selected from the lymphocytes gate as CD45/CD19 positive. The gated cells were positive for CD25, CD11c, CD20, and CD103, while CD10 proved to be dim to negative. Moreover, cells positive for CD3, CD4, and CD8, the three pan-T markers, as well as CD19, showed a bright expression of CD5. The atypical CD5 expression is usually correlated with a negative prognosis and thus chemotherapy with cladribine should be initiated. HCL is an indolent chronic lymphoproliferative disorder and diagnosis is usually straightforward. However, atypical expression of CD5 renders its differential diagnosis more difficult, but FC is a useful tool that allows an optimal classification of the disease and allows initiation of timely satisfactory therapy.

The Persistence of COVID-19-Related Pancytopenia as A Possible Sign of Hairy Cell Leukemia: A Case Report

COVID-19 is known to cause many hematological abnormalities, such as thrombocytopenia, leucopenia, and lymphopenia. Pancytopenia, a decrease in all peripheral blood cell lines, is a rare complication not commonly seen in patients with COVID-19. We report a case of a patient who experienced COVID-19 infection with mild clinical symptoms like fever, fatigue, and muscle and bone aches. The laboratory examinations revealed pancytopenia, mainly neutropenia, thrombocytopenia, mild anemia, and relative lymphocytosis, which persisted after infection resolution. The splenomegaly in abdominal echography and the characteristics of lymphocyte elements in peripheral blood smear examination raised suspicion of the presence of hairy cell leukemia (HCL); therefore, the patient was further examined with a bone marrow biopsy, which confirmed the diagnosis. The persistence of pancytopenia after recovery from COVID-19 infection, especially in patients with splenomegaly, should raise suspicion of another hematological coexistence diagnosis like HCL.

Evaluating the effectiveness and tolerability of chemotherapy in hairy cell leukemia: A comprehensive systematic review and meta-analysis.

e19547 Background: Hairy cell leukaemia (HCL) is a rare, chronic B cell cancer that involves the bone marrow, peripheral blood, and spleen. Many treatment options are available for HCL. Our study aims to elucidate the safety and efficacy of each intervention through the pooled proportion of response to treatment and adverse events. Methods: We conducted a literature search across PubMed, Embase, Cochrane, and Google Scholar from inception till February 2023. We included clinical trials and cohorts of patients with HCL receiving modern anticancer drugs (cladribine, rituximab, cladribine plus rituximab, BRAF inhibitors, anti-CD22 monoclonal antibodies, and ibrutinib). The primary efficacy outcomes were Objective Response Rate (ORR) and Complete Response Rate (CRR) and the primary safety outcome was adverse effects (AEs). We used OpenMetaAnalyst to pool data using the Hedges-Olkin Random Effects Model, with subgroup analysis for HCL type and study design. Results: Our meta-analysis included 44 studies (28 trials and 16 cohorts) with 3976 patients with HCL. The median age was 56.7 years. The highest efficacy was seen in patients receiving combination therapy of cladribine and rituximab, with an ORR of 97% and CRR of 92%. Cladribine monotherapy showed an ORR of 95% and CRR of 79%, while rituximab monotherapy had an ORR of 62% and CRR of 31%. BRAF inhibitors, anti-CD22 monoclonal antibodies, and ibrutinib showed less efficacy, with ORRs of 92%,78% and 51% and CRRs of 41%, 49%, and 17% respectively. Subgroup analysis for study design and HCL type did not resolve heterogeneity. The ORR and CRR with 95% Confidence Intervals and AEs for each regimen are given in the table. Conclusions: Cladribine with rituximab is the most effective treatment for untreated and relapsed HCL patients, with neutropenia as the most common AE. Since we pooled the proportions for treatment-naïve and relapsed cases together due to inavailability of segregated data, the results should be used cautiously in clinical decision making and limit the derivation of consensus for treatment of newly diagnosed or relapsed HCL. [Table: see text]

Outcomes of intravenous and subcutaneous cladribine administration in patients with hairy cell leukemia: A systematic review and meta-analysis.

e19546 Background: Hairy cell leukaemia (HCL) is a rare, chronic B cell cancer that involves the bone marrow, peripheral blood, and spleen. Cladribine (2CdA) monotherapy is used as a first line treatment for HCL. 2CdA can be administered intravenously (IV) or subcutaneously (SC). The aim of our study is to compare the safety and efficacy of these two routes of administration of 2CdA as a first line treatment of HCL. Methods: We conducted a systematic literature search across multiple databases and Google up to February 2023. We included studies that reported outcomes for either intravenous (IV) or subcutaneous (SC) cladribine (2CdA) therapy, as well as those that directly compared the two routes. Our primary efficacy outcomes were overall response rate (ORR) and complete response rate (CRR), and our primary safety outcome was adverse effects (AEs). We used OpenMetaAnalyst to pool data using the Hedges-Olkin Random effects model and conducted subgroup analysis for HCL type (classical vs classic and variant both). We calculated odds ratios (ORs) for studies involving a head-to-head comparison between the two routes and used the Higgins I2 statistic to assess heterogeneity. Results: We identified a total of 25 studies (15 trials, 10 cohorts) with a patient population of 2669. The median age of the patients was 53.5 years. The pooled ORR and CRR for IV and SC 2CdA therapy were 96%, 82%, 88% and 67% respectively. The incidence of neutropenia (82% vs 61%) and infections (13% vs 16%) was greater for SC 2CdA than IV 2CdA. Five studies provided a direct comparison between SC and IV routes but three were excluded from the analysis due to unavailability of desired outcomes. Studies involving a direct comparison between the 2 routes of administration showed that the odds of achieving CRR were 86.6% greater with IV than SC 2CdA but these results were not significant. The proportion of adverse events was comparable for IV and SC routes. Subgroup analysis for HCL type did not resolve heterogeneity for ORR and CRR. It did, however, result in greater ORR for classic (92%) and mixed (92%) HCL treated with SC 2CdA. Conclusions: Compared to SC 2CdA, IV 2CdA is safer and more effective as a first-line treatment of HCL. However, future high-power randomized control trials that directly compare IV and SC routes are needed to confirm this evidence. [Table: see text]

Single‐agent rituximab as an effective salvage therapy in pre‐treated hairy cell leukemia

Introduction: Hairy cell leukemia (HCL) patients usually experience multiple disease relapses during the course of their disease. The CD20 antigen is highly expressed on the surface of hairy cells. Single-agent rituximab can be a suitable treatment options in patients relapsing after repeated courses of purine analogs, if purine analogs are contraindicated (e.g., in case of poor bone marrow cellularity, high disease infiltration predicting long-lasting aplasia), especially if newer agents (such as moxetumomab or vemurafenib) are not easily available (as it happens in several countries). Methods: Our institutional series of HCL patients receiving single-agent rituximab as salvage therapy was retrospectively reviewed. Patients received rituximab at the standard dose of 375 mg/m2 weekly for 4 weeks. The main study objectives were overall response rate (ORR), time-to-next treatment (TTNT), progression-free survival (PFS) and overall survival (OS). Responses have been categorized according to the Consensus Resolution Criteria. Results: Thirty-three patients received 39 courses of rituximab (4 patients received it twice, one patient three times), in median as third line of therapy (range 2–8). First rituximab was given at a median age of 61 years and at a median time from disease diagnosis of 65 months. Out of 39 courses, a complete response was obtained in 28.2% of cases, a partial response in 23.1% and a minimal response in 20.5%, yielding an ORR of 71.8%. In 28.2% of patients, we observed no response. Median TTNT was reached at 33 months (65% at 2 years), while median PFS was reached at 24 months (51% at 2 years). Median OS resulted of 154 months (22% at 20 years). Among the 5 patients receiving rituximab more than once, all responded after the first course, although the ORR after the second or later course was only 50%. Median TTNT following the first rituximab was 38.5 months in these patients, ranging from 15 to 205 months. Keywords: Immunotherapy, Lymphoid Cancers No conflicts of interests pertinent to the abstract.

SINGLE‐CELL RNA‐SEQ OF CLASSIC HAIRY CELL LEUKEMIA REVEALS DISEASE DRIVERS LINKED TO INTRINSIC TREATMENT RESISTANCE AND IDENTIFIES DUSP1 AS POTENTIAL NEW THERAPEUTIC TARGET

Introduction: Standard treatment with purine analogs such as cladribine (2-CdA) achieves excellent remissions in classic hairy cell leukemia (HCL), but up to 25% of patients relapse early and there is a non-diminishing risk of late relapse in complete responders. Even when targeting the recurrent genetic driver mutation BRAF V600E, HCL cells frequently persist in the bone marrow suggesting cooperating biologic alterations facilitating disease survival and persistence. Methods: Single-cell RNA sequencing (scRNA-Seq) was performed in primary HCL cells derived from three long-term (>10 years progression-free survival, PFS) and three short-term responders after 2-CdA treatment (SR, <3 years PFS) and from up to three time points (HCL diagnosis, first, and second relapse). Functional studies were performed using the BRAF D594E-mutated HAIR-M cell line after validating BRAF D594E as an activating mutation with similar downstream signaling and inhibitory potential with BRAF inhibitors as compared to BRAF V600E in primary HCL cells. Results: scRNA-Seq revealed distinct HCL cell clusters characterized by marked overexpression of DUSP1, FOS and JUND in all six patients that were outgrowing at first and second relapse in all three SR. In these DUSP1hi/FOShi/JUNDhi HCL cells, PROGENy cancer pathway analysis demonstrated induced activation of MAPK pathways and gene ontology analysis found negative regulation of the pro-apoptotic p38-MAPK-cascade as potential underlying biologic alteration. BRAF D594E-mutated HAIR-M cells were selected as substitute for primary HCL cells in cell culture due to comparable changes upon exposure to BRAF inhibitors in BRAF kinase activity conformation as assessed by the modular kinase conformation biosensor platform (KinCon) and similar reduction in ERK phosphorylation levels in HEK293T cells transiently overexpressing either flag-tagged BRAF D594E or BRAF V600E. In HAIR-M, we confirm stable expression levels of DUSP1, FOS and JUND, which were highly increased when co-cultured with HS5 stromal cells. Whereas increased expression of FOS and JUND was reversible upon exposure to BRAF inhibitors, expression of DUSP1, a direct target of BRAF-MEK-ERK signaling, and phosphorylation of p38 remained unaffected. As DUSP1 preferentially dephosphorylates/inactivates p38, we studied exposure of the DUSP1-inhibitor BCI in co-culture and found re-phosphorylated p38. Conclusion: DUSP1hi/FOShi/JUNDhi HCL cells may represent a distinct subset of HCL cells highly dependent on environmental cues with an inherently more resistant phenotype to treatment with 2-CdA or BRAF-inhibitors. Inhibition of DUSP1 may represent a novel therapeutic approach by effectively truncating HCL cells from extracellular pro-survival stimuli. Finally, our results suggest that BRAF D594E-mutated HAIR-M cells may serve as a representative disease model for functional studies. Keywords: bioinformatics, computational and systems biology, indolent non-Hodgkin lymphoma, tumor biology and heterogeneity No conflicts of interests pertinent to the abstract.

Implementing a germline testing program using fingernail specimens for patients with hematologic malignancies and initial clinical findings.

10632 Background: About 5-20% of hematologic malignancies (HM) occur in the setting of a genetic cancer predisposition syndrome. Additionally, overt constitutional syndromes involving multiple systems may also predispose to HM. The spectrum of cancer predisposition in patients with HM has been limited partially due to the difficulty of germline sample ascertainment from patients with liquid tumors as skin biopsies and fibroblast cultures are often required for testing. Methods: Hematologic malignancy patients enrolled in Memorial Sloan Kettering Cancer Center’s institutional 12-245 study who were having somatic testing performed on their tumor were given the option to consent to germline testing using fingernail specimens. The validated germline assay using nails as a sample type was approved as a clinical test by the New York State Department of Health. Samples were analyzed using a custom panel consisting of 82 cancer predisposition genes. Single nucleotides, insertions deletions, and copy number variants were detected using our analytic pipeline and analyzed according to ACMG criteria for pathogenicity. Only pathogenic and likely pathogenic germline variants (gPV) were returned. Results: Among 86 HM patients (acute myeloid leukemia, n = 19; myelodysplastic syndrome, n = 16; acute B lymphoblastic leukemia, n = 9; acute T-cell leukemia, n = 4; mixed phenotypic acute leukemia, n = 1; chronic lymphocytic leukemia, n = 7; hairy cell leukemia, n = 1; chronic myeloid leukemia, n = 4; chronic myelomonocytic leukemia, n = 1, non-Hodgkin lymphoma, n = 12; Hodgkin lymphoma, n = 8; and multiple myeloma, n = 4), gPV were detected in 16 % (14/86). Heterozygous gPV identified in high/moderate penetrant genes included 2 BRCA1, 2 ATM, 1 PALB2, and 3 CHEK2. Monoallelic carriers for homozygous disease included 2 MUTYH and 1 MSH3. Biallelic gPV were identified in 3 patients (1 FANCA, 1 ATM, 1 MSH6); the patients with Fanconi anemia (age 25) manifesting with MDS and constitutional mismatch repair deficiency (age 13) presenting with T-cell lymphoblastic lymphoma had not been previously diagnosed with these conditions and did not have obvious clinical features outside of their cancer diagnosis. In all 3 patients, identification of an autosomal recessive syndrome impacted therapeutic planning. Conclusions: Our study demonstrates the feasibility of utilizing nails, a non-contaminated germline sample source, for HM predisposition with a significant proportion of pediatric and adult HM patients identified to harbor gPV in a cancer predisposition gene. Autosomal recessive diseases should be considered not only in pediatrics but also adult patients and requires confirmation of allele segregation in parents. Our data also demonstrate the importance of gPV in HM for therapeutic planning.

17th International Conference on Malignant Lymphoma, Palazzo dei Congressi, Lugano, Switzerland, 13 - 17 June, 2023.

Introduction: Peripheral T-cell lymphomas (PTCL) are a rare and heterogeneous group of malignancies that share a unifying feature of epigenetic dysregulation. Recent evidence suggests that PTCL, unlike other forms of cancer or even lymphoma, exhibits a marked vulnerability to hypomethylating agents (HMAs) alone and especially in combination with HDAC inhibitors. HMAs like azacitidine (AZA) and decitabine (DAC) have been shown to reverse transcriptional repression secondary to hypermethylation. Cladribine (CLAD) is FDA-approved for the treatment of hairy cell leukemia and is postulated to inhibit both DNA and histone methylation. Here, we sought to define the mechanistic differences between different DNA HMAs in order to inform a rationale on the optimal combinations that might exploit the epigenetic vulnerabilities of PTCL. Methods: Cell viability, caspase activity assay, and western blotting (WB) were performed on a panel of T-cell lymphoma cell lines to identify the effects of AZA/DAC/CLAD on cell survival, apoptosis, and DNA methyltransferase (DNMT) levels. Liquid chromatography-based mass spectrometry (LC-MS) was done to quantify 5-methyl cytosine (5-mC) levels. Results: Cell viability analysis confirmed that the dose and time-dependent sensitivity of the six PTCL cell lines differed following exposure to AZA/DAC/CLAD, where CLAD showed the lowest IC50 value (0.1–1 µM) across all cell lines, followed by AZA (IC50: 1–10 µM), and DAC had the least effect on cell viability (IC50: >100 µM, except T-ALL). A differential threshold of caspase activation was observed across the PTCL cell lines where CLAD showed the most superior caspase activity leading to the highest apoptotic potential. However, WB analysis showed that after 24 hours of treatment, DNMT1 and DNMT3A protein levels were significantly depleted at low concentrations of DAC (<0.01 µM) compared to AZA whereas CLAD did not affect the DNMT1 and DNMT3A levels. LC-MS-based quantification of 5-mC showed a similar relationship in methylation, with initial changes observed at doses >0.01 μM of DAC and >0.1 μM of AZA/CLAD. Taking the short half-life of AZA/DAC into account, cell viability assays with daily addition of AZA/DAC showed increased cell cytotoxicity for AZA/DAC treated samples, which was comparable to CLAD. Ongoing analyses of gene expression and metabolism of the universal methyl donor S-adenosylmethionine (SAM) will help to understand the mechanistic difference between these HMAs. Conclusions: These data suggest that the HMAs have a distinct mechanism of action for hypomethylation. While AZA/DAC induces hypomethylation by depletion of DNMTs, CLAD acts in a DNMT depletion-independent pathway. A mechanistic understanding of AZA/DAC/CLAD will inform how best to use them in clinic as well as assist in the strategic development of biological correlates to further support their therapeutic application. The research was funded by: Translational Orphan Blood Cancer Research Initiative Fund and RO1 # FD-R-006814-01. Keywords: Genomics, Epigenomics, and Other -Omics, Molecular Targeted Therapies No conflicts of interests pertinent to the abstract.

A cyanine-based NIR fluorescent Vemurafenib analog to probe BRAFV600E in cancer cells

BRAF represents one of the most frequently mutated protein kinase genes and BRAFV600E mutation may be found in many types of cancer, including hairy cell leukemia (HCL), anaplastic thyroid cancer (ATC), colorectal cancer and melanoma. Herein, a fluorescent probe, based on the structure of the highly specific BRAFV600E inhibitor Vemurafenib (Vem, 1) and featuring the NIR fluorophore cyanine-5 (Cy5), was straightforwardly synthesized and characterized (Vem-L-Cy5, 3), showing promising spectroscopic properties. Biological validation in BRAFV600E-mutated cancer cells evidenced the ability of 3 to penetrate inside the cells, specifically binding to its elective target BRAFV600E with high affinity, and inhibiting MEK phosphorylation and cell growth with a potency comparable to that of native Vem 1. Taken together, these data highlight Vem-L-Cy5 3 as a useful tool to probe BRAFV600E mutation in cancer cells, and suitable to acquire precious insights for future developments of more informed BRAF inhibitors-centered therapeutic strategies.