Orland, Mark D.

Abstract Myeloid neoplasia encompasses a heterogeneous and complex molecular landscape whereby the distinct combinatorial patterns associated with clinical phenotypes are difficult to delineate. Given that genetic heterogeneity can be a consequence of the topology of the fitness landscape (peaked/non-peaked=high vs low fitness), we investigated co-mutational patterns in TP53 context as an example of hallmark genomic heterogeneity. Indeed, TP53 gene is characterized by hypomorphic/loss-of-function lesions, truncating mutations (frameshifts, stop codons), missense mutations often having a dominant-negative effect and loss of heterozygosity by chromosome 17p deletion driving clonal expansion. Clinical phenotypes of TP53 mutants are also heterogeneous. Here, we stratify TP53 mutations based on our previous published data1 whereby patients with single-hit TP53 and variant allelic frequency (VAF) >50% were classified as obligatory biallelic, patients with VAF between 23-50% as probable biallelic and <23% as probable monoallelic. A threshold of VAF 23% was optimal to separate monoallelic vs biallelic and was based on all-cause mortality. A tree-based model (RandomForestSRC) was used to build a survival model with VAF as a single covariate and minimum node size set to 15 to optimize the cut-off. Using this cut-off, we delineate the epistatic landscape and potential interactions among different TP53 mutational spectra and its fitness. We curated a cohort of 800 patients with TP53 mutations from our institution. In total 36% of the cases carried single hits while 64% had double hits genomic configuration. About 70% of the mutations were missense and were detected at canonical sites (R175H, Y220C, M237I, R273H, R282W, R248Q). We took into consideration 35 features and clustered our cohort of TP53 mutants using factor analysis. When we stratified the cohort based on our predetermined VAF threshold, we found that majority of the variants with high VAF, to be deemed as obligatory biallelic, co-occurred with complex karyotype. These cases were very homogeneous hence had on average a low number of additional variants, likely due to TP53 clones having reduced fitness in the presence of additional mutations. Conversely, patients without complex karyotype were mostly assigned to the monoallelic group due to low to median VAFs. Consequently, these samples had on average a higher number of additional hits, hence a heterogeneous molecular landscape. To substantiate this finding, we noticed that among monoallelic patients two characteristic pairs were observed (TP53-TET2 and TP53-SF3B1) and showed different patterns according to karyotypic associations. Indeed, both pairs in normal karyotype (TP53-TET2, 65%; TP53-SF3B1, 23%) had the highest number of additional mutations on average compared to other monoallelic hits in complex karyotype suggesting that clones resulting by these pairs were advantageous and produced higher fitness driving heterogeneity when together with other mutations. As a preliminary analysis to characterize the fitness landscape of canonical missense TP53 mutations, we investigated whether distinct TP53 mutations conferred differential clonal fitness by implementing a previously published model of stochastic hematopoietic stem cell growth based on the distribution of allelic frequencies across different age groups. Given a fixed stem cell population pool and a constant mutation rate, the distribution of allelic frequencies in the population of corresponding mutations across age can inform the fitness/selection coefficient. The model predicts that high fit mutations will expand more in the population (high VAF) depending on the time the mutation is allowed to expand (age). Based on the literature, we set the stem cell pool to 100,000 and the mutation rate to 1.4E-8.2We limited our analysis to mutations found in at least 10 individual in our cohort and to single hits due to potential epistatic interactions across multiple mutations in the same gene. Given this criterion two mutations R273H and R248Q were analyzed. Interestingly, we observed a 15% increase in fitness gain for R273H compared to R248Q. In summary, mutational heterogeneity and clonal fitness might provide clues to the diversity of TP53 mutational configurations. Our model will be further optimized for the upcoming ASH meeting by incorporating temporal sampling and increasing sample size to define differences in fitness according to mutation site.

Abstract Chronic idiopathic neutropenia (CIN) is characterized by a persistently reduced absolute neutrophil count, typically <1.5×10⁹/L for ≥3 months, without identifiable infectious, nutritional, autoimmune, clonal, congenital, or drug-related causes. It most commonly affects adult women, carries a variable risk of infection, and is frequently managed expectantly in the absence of severe or recurrent infections. An index case of CIN with irregular menses and normalization of counts during pregnancy prompted an institution-wide review of adult neutropenia. U[p front we excluded cases of known congenital and drug-induced neutropenia. Among 238 presumed CIN patients, 88 had large granular lymphocytic (LGL) leukemia–associated neutropenia, 63 had autoimmune neutropenia defined by the presence of anti-neutrophil antibodies, and 87 met criteria for idiopathic neutropenia. Within the presumptive CIN group, extended blood antigen screening identified 12 patients with a Duffy-null phenotype, who were excluded from further idiopathic analysis (final n=75). This included 10 African American, 1 Caucasian, and 1 Asian patient. Extended blood-group profiling (Kidd, Colton, Lutheran, Dombrock, LW, ABO) showed no significant deviation from population frequencies. In the remaining non-Duffy CIN patients, remarkably 54/75 were female with a mean age of 45±16 years. At presentation, mean WBC was 2.84±0.58×10⁹/L and ANC was 0.92±0.39×10⁹/L, Hgb was 13.5±1.2g/dL and platelets were 229±83×10⁹/L. Antinuclear antibodies were assessed in 73 patients, with 63 negative and 10 positive, predominantly speckled (66%) but rheumatologic consultation did not yield systemic autoimmune diagnoses. Hypothyroidism was noted in two CIN cases. Irregular menses were reported in 50% of female CIN patients with documented histories, and among those, 80% exhibited higher or normal neutrophil counts during gestation. Physiologically, pregnancy is a progesterone-high state associated with neutrophilia and physiologic leukocytosis; in addition, progesterone can dampen cytotoxic T-cell activity and inflammatory signaling while supporting marrow niche function. Furthermore, progesterone binds PR on marrow stromal cells and can upregulate CSF3 (G-CSF) and possibly other hematopoietic growth factors, thus regulating granulopoiesis. By contrast, anovulatory or irregular cycles often reflect luteal progesterone deficiency, which may predispose susceptible patients to lower ANC prompting us to formulate a theory that excess of CIN in females may be due to a progesterone-responsive CIN subtype. From our cohort, there were no patients on progesterone-supplement to evaluate if there would be responsiveness secondary to its utilization. To further support this theory we turned to metanalytic resources. TriNetX1allowed us search and identify women receiving exogenous progesterone versus a control receiving non-hormonal contraceptives and assign to them a corresponding ANC. When we compared ANC in 1:1 greedy propensity-score matching to control for covariates (demographics, BMI, and disease confounders e.g., malignancy). balance between comparator groups was confirmed by standardized mean differences <0.10. After matching (n=18,561 per arm), the exogenous progesterone group had a significantly higher neutrophil count compared to non-hormonal contraception (1.9±3.7 vs 1.5±1.7; t=3.5, p=.0004). The cohort age range was similar to our patient population 44 ±19. Our observations motivate prospective evaluation of progesterone-high states as potential modifiers of ANC in otherwise idiopathic cases and particularly refractory cases Cycle-synchronized CBC with paired progesterone and estradiol measurements, together with controlled progesterone augmentation trials, can quantify ANC changes and clinical outcomes in this subset. We thank TriNetX and all participants for their contribution, without whom this research would not have been possible. ReferencesRobertson SA, Mayrhofer G, Seamark RF. Ovarian steroid hormones regulate granulocyte-macrophage colony-stimulating factor synthesis by uterine epithelial cells in the mouse. Biol Reprod. 1996 Jan;54(1):183-96. doi: 10.1095/biolreprod54.1.183. PMID: 8838016.

Abstract Outgrowth of a founder mutant clone is an initial event in leukemogenesis. The corresponding somatic hit likely conveys a fitness advantage over a polyclonal background. Several factors may modulate the competitiveness of hematopoietic stem or progenitor cells, including aging, genotoxic stress, repeated cycles of stress hematopoiesis, and inherited genetic fitness deficiency. The nature of these conditions provides a particularly fertile environment in which only certain mutant clones thrive. For instance, chemotherapy facilitates expansion of PPMD1MT or TP53MT clones, aging-related loss of fitness predisposes to outgrowth of TET2MT clones, while many inherited bone marrow failure (BMF) syndromes are associated with specific clonal acquisitions due to somatic gene rescue. Identification of factors enabling the expansion of clones with specific mutations may help to develop targeted preventive, screening, or therapeutic strategies. Recently, high levels of erythropoietin (EPO) induced by frequent blood donation were shown to favor the emergence of DNMT3AR882 clones due to their increased EPO sensitivity1. We theorized that this may be a more general phenomenon operating in other diseases characterized by high EPO levels. Thus, we selected 644 patients in whom endogenous serum EPO levels had been assessed and who underwent mutational NGS analysis. Given that this cohort consisted of patients with hematologic neoplasms, EPO levels were broad with the majority falling outside the normal clinical reference range. For this study we used EPO levels ≥100mU/mL as the threshold to define high and low EPO groups. This threshold laid above the 75th percentile for our cohort (M=31.1; IQR=109.7) to capture outliers more likely to reflect biologically significant erythropoietic stress. DNMT3AMT were present in 14% of high EPO and in 12% of low EPO groups (p=0.5). However, in the high EPO group, R882 constituted 32% of DNMT3AMT while in the low EPO group R882 was found in only 11% of DNMT3AMT cases (p=.02). In a reverse fashion, the mean level of EPO in DNMT3AR882 was 441.7mU/mL while it was 215.3mU/mL in other DNMT3AMT carriers (p=0.03) and 186.2mU/mL in DNMT3AWT cases (p<0.001). To assess whether the effect on DNMT3A was dependent on EPO levels rather than anemia, we determined mean hemoglobin levels in R882 (µ=10.2g/dL), other DNMT3AMT (µ=10.4g/dL), and wild type cases (µ=10.9g/dL) and found no significant differences (p=0.33). To assess whether R882-EPO sensitivity was related to EPO-R expression levels, we compared EPO-R expression in R882 (µ=2.7), non-R882 (µ=2.6) mutations, and WT cases (µ=2.8) and found no significant difference. To assess whether the impact of high EPO states was specific to DNMT3AMT we next analyzed the distribution of other mutations. We observed that frameshift mutations in BCOR (p = 0.013) and BCORL1 (p=0.036) were significantly more frequent in high EPO patients. BCORMT was also overall more prevalent in the high EPO group (p=.001), while BCORL1 frequency was similar across EPO strata (p=0.77) showing a similar trend to DNMT3AMT. Beyond these genes, other patterns emerged, particularly within CH-associated genes. Individuals with U2AF1MT had elevated EPO (p=.0087), with variant-specific enrichment: p.S34F was more common in high EPO (p=.038) whereas p.Q157P predominated in low EPO patients (p=0.038). No significant EPO associations were observed for other CH-related genes such as ASXL1, CBL, and TET2. The limitations of this study notwithstanding, these findings support a biologically meaningful relationship between elevated EPO levels and the acquisition or enrichment of specific CH-associated mutations in patients with hematologic malignancies. The association of high EPO with DNMT3AR882, frameshift mutations in BCOR/L1, and variant-specific enrichment in U2AF1 suggests that EPO-driven stress may contribute to clonal selection or expansion. Our study of high EPO levels and DNMT3AMT analysis illustrates that external conditions may influence selection pressure for specific mutations. However, selection pressure may be a complex combination of factors. Non-malignant conditions with high EPO, such as hypoxia or intrinsic BMF, may also create conditions facilitating the acquisition of specific somatic hits. Recognition of evolutionary pressures and their associations with specific mutations may improve our understanding of CH pathogenesis, and conceptualization of therapeutic or preventative measures.

Abstract Background: Chronic immunosuppression in solid organ transplant recipients leads to B- and T-cell depletion, which increases the risk of somatic driver mutations that drive monoclonal lymphocyte proliferation. Paradoxically, this impairs cellular immunity, leading to increased susceptibility to both bacterial and viral pathogens. Methods: This retrospective cohort study evaluated solid organ transplant recipients diagnosed with post-transplant lymphoproliferative disorder (PTLD) at the Cleveland Clinic Foundation between January 1, 2010, and December 30, 2021. Patients aged ≥18 years with infection data available for at least one-year post-PTLD diagnosis were included, excluding hematopoietic stem cell transplant recipients. Data on PTLD subtype, Epstein-Barr virus (EBV) status, infectious complications, and outcomes were analyzed using univariate analysis (Pearson’s χ² test) and multivariable logistic regression to identify predictors of infections and mortality. Results: Among 98 PTLD cases, the median onset was 7.03 years post-transplant. EBV-positive PTLD had an onset of 6.97 ± 7.21 years, whereas EBV-negative cases occurred later (8.06 ± 5.24 years). Monomorphic PTLD (94.9%), particularly diffuse large B-cell lymphoma (DLBCL, 63.3%), was predominant. Infections occurred in 60% of patients post-PTLD, with bacterial (41.25%), viral (31.66%), fungal (25.9%), and parasitic (1.19%) infections. At one year, infection-related mortality (48%) exceeded PTLD progression-related deaths (36%). Conclusion: PTLD presents with a complex interplay of immunosuppression, malignancy, and infection. Infections, particularly bacterial infections, are major causes of morbidity and mortality. These findings highlight the need for vigilant infectious disease surveillance and tailored interventions to reduce infection-related mortality and improve outcomes in high-risk populations.