p53 immunohistochemistry as an ancillary tool for rapid assessment of residual disease in TP53-mutated acute myeloid leukemia and myelodysplastic syndromes.

OBJECTIVES: Measurable residual disease flow cytometry (MRD-FC) and molecular studies are the most sensitive methods for detecting residual malignant populations after therapy for TP53-mutated acute myeloid leukemia and myelodysplastic neoplasms (TP53+ AML/MDS). However, their sensitivity is limited in suboptimal aspirates or when the immunophenotype of the neoplastic blasts overlaps with erythroids or normal maturing myeloid cells. In this study, we set out to determine if p53 immunohistochemistry (IHC) correlates with MRD-FC and next-generation sequencing (NGS) in the posttherapy setting and to determine the utility of p53 IHC to detect residual disease in the setting of negative or equivocal MRD-FC. METHODS: We retrospectively identified 28 pre- and posttherapy bone marrow biopsy specimens from 9 patients with TP53+ AML/MDS and a p53 overexpressor phenotype by IHC (strong 3+ staining at initial diagnosis). Next-generation sequencing and/or MRD-FC results were collected for each specimen. RESULTS: Using a threshold of more than ten 2-3+ cells in any one 400× field, p53 IHC detected residual disease with a sensitivity of 94% and a specificity of 89%. The threshold used in this study showed a high degree of concordance among 6 blinded pathologists (Fleiss κ = 0.97). CONCLUSIONS: Our study suggests that p53 IHC can be used as a rapid tool (within 24 hours) to aid in the detection of residual disease that may complement MRD-FC or NGS in cases in which the flow cytometry immunophenotype is equivocal and/or the bone marrow aspirate is suboptimal.

Natural history of clonal haematopoiesis seen in real-world haematology settings.

Recursive partitioning of healthy consortia led to the development of the Clonal Hematopoiesis Risk Score (CHRS) for clonal haematopoiesis (CH); however, in the practical setting, most cases of CH are diagnosed after patients present with cytopenias or related symptoms. To address this real-world population, we characterize the clinical trajectories of 94 patients with CH and distinguish CH harbouring canonical DNMT3A/TET2/ASXL1 mutations alone ('sole DTA') versus all other groups ('non-sole DTA'). TET2, rather than DNMT3A, was the most prevalent mutation in the real-world setting. Sole DTA patients did not progress to myeloid neoplasm (MN) in the absence of acquisition of other mutations. Contrastingly, 14 (20.1%) of 67 non-sole DTA patients progressed to MN. CHRS assessment showed a higher frequency of high-risk CH in non-sole DTA (vs. sole DTA) patients and in progressors (vs. non-progressors). RUNX1 mutation conferred the strongest risk for progression to MN (odds ratio [OR] 10.27, 95% CI 2.00-52.69, p = 0.0053). The mean variant allele frequency across all genes was higher in progressors than in non-progressors (36.9% ± 4.62% vs. 24.1% ± 1.67%, p = 0.0064). This analysis in the post-CHRS era underscores the natural history of CH, providing insight into patterns of progression to MN.

Niche-directed therapy in acute myeloid leukemia: optimization of stem cell competition for niche occupancy.

Acute myeloid leukemia (AML) is an aggressive malignancy of stem cell origin that contributes to significant morbidity and mortality. The long-term prognosis remains dismal given the high likelihood for primary refractory or relapsed disease. An essential component of relapse is resurgence from the bone marrow. To date, the murine hematopoietic stem cell (HSC) niche has been clearly defined, but the human HSC niche is less well understood. The design of niche-based targeted therapies for AML must account for which cellular subsets compete for stem cell occupancy within respective bone marrow microenvironments. In this review, we highlight the principles of stem cell niche biology and discuss translational insights into the AML microenvironment as of 2021. Optimization of competition for niche occupancy is important for the elimination of measurable residual disease (MRD). Some of these novel therapeutics are in the pharmacologic pipeline for AML and may be especially useful in the setting of MRD.

Epstein-Barr virus-positive lymphoproliferative disorder manifesting as pulmonary disease in a patient with acute myeloid leukemia: a case report.

BACKGROUND:  Patients with lymphoproliferative disorders following hematopoietic stem cell transplant (HSCT) most commonly present with fever and lymphadenopathy within the first 5 months of transplant. Pulmonary post-transplant lymphoproliferative disorder (PTLD) is a particularly aggressive and rapidly progressive disease, with high morbidity and mortality. There are a very limited number of reported pulmonary PTLD cases following HSCT in patients with acute myeloid leukemia (AML). Early diagnosis and detection of pulmonary PTLD is critical given its high lethality. However, variable clinical presentations and nonspecific radiographic findings make pulmonary PTLD difficult to distinguish from other more common causes of pulmonary disease in AML patients. CASE PRESENTATION: Here, we describe a 68-year-old Caucasian man who presented for salvage induction therapy following relapse of his AML after a haploidentical allogeneic HSCT 10 months earlier. He developed recurrent fevers, dry cough, and hypoxemia, with chest computed tomography (CT) showing bibasilar consolidations and increased nodularity without increased lymphadenopathy. His symptoms initially improved with antibiotic and antifungal therapy, but his follow-up chest CT showed progression of disease despite symptomatic improvement. Epstein-Barr virus (EBV) was detected in his blood by polymerase chain reaction (PCR), and a lung biopsy revealed monomorphic PTLD with B cells positive for EBV. Unfortunately, the patient's condition rapidly deteriorated, and he passed away prior to treatment initiation. CONCLUSIONS:  To our knowledge, this is the first reported case of an AML patient developing pulmonary PTLD relatively late in his post-transplant course in the setting of relapsed disease and salvage therapy. Pulmonary PTLD, a rare but highly lethal disorder, can imitate the symptoms and radiographic findings of pneumonia, a common diagnosis in immunocompromised AML patients. This case illustrates the importance of considering pulmonary PTLD in the differential diagnosis for pulmonary disease in AML patients with a history of HSCT, especially in the setting of progressive radiographic findings despite broad antibacterial and antifungal therapy. Further, our case demonstrates the importance of biopsy and uninterrupted EBV DNA monitoring in the definitive diagnosis of PTLD, given nonspecific symptomatology and radiographic findings.

Targeting LSCs: Peeling Back the Curtain on the Metabolic Complexities of AML.

Most patients with AML succumb to chemoresistant leukemia stem cells (LSCs), which persist and reinitiate disease years after clinical remission. In this issue of Cell Stem Cell, Jones et al. (2020) identify a therapeutically targetable mechanism of resistance to venetoclax in relapsed and refractory AML LSCs mediated by nicotinamide metabolism.

Combined STAT3 and BCR-ABL1 inhibition induces synthetic lethality in therapy-resistant chronic myeloid leukemia.

Mutations in the BCR-ABL1 kinase domain are an established mechanism of tyrosine kinase inhibitor (TKI) resistance in Philadelphia chromosome-positive leukemia, but fail to explain many cases of clinical TKI failure. In contrast, it is largely unknown why some patients fail TKI therapy despite continued suppression of BCR-ABL1 kinase activity, a situation termed BCR-ABL1 kinase-independent TKI resistance. Here, we identified activation of signal transducer and activator of transcription 3 (STAT3) by extrinsic or intrinsic mechanisms as an essential feature of BCR-ABL1 kinase-independent TKI resistance. By combining synthetic chemistry, in vitro reporter assays, and molecular dynamics-guided rational inhibitor design and high-throughput screening, we discovered BP-5-087, a potent and selective STAT3 SH2 domain inhibitor that reduces STAT3 phosphorylation and nuclear transactivation. Computational simulations, fluorescence polarization assays and hydrogen-deuterium exchange assays establish direct engagement of STAT3 by BP-5-087 and provide a high-resolution view of the STAT3 SH2 domain/BP-5-087 interface. In primary cells from chronic myeloid leukemia (CML) patients with BCR-ABL1 kinase-independent TKI resistance, BP-5-087 (1.0 µM) restored TKI sensitivity to therapy-resistant CML progenitor cells, including leukemic stem cells. Our findings implicate STAT3 as a critical signaling node in BCR-ABL1 kinase-independent TKI resistance, and suggest that BP-5-087 has clinical utility for treating malignancies characterized by STAT3 activation.

Over-expression of TRPM8 is associated with poor prognosis in urothelial carcinoma of bladder.

Transient receptor protein (TRP) channels are frequently associated with tumors and are correlated to patient's outcome. We firstly investigated TRP channel melastatin 8 (TRPM8) expression in urothelial carcinoma of bladder (UCB) and its correlation with UCB clinicopathological features and additionally evaluated the association between TRPM8 expression and patients' survival rate to elucidate its role in bladder oncogenesis. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was conducted to examine TRPM8 messenger RNA (mRNA) expression in 36 pairs of freshly frozen UCB tissues and matched noncancerous tissues. Immunohistochemistry (IHC) was performed in 156 archived paraffin-embedded UCB samples to explore the correlation between TRPM8 protein and clinicopathological features. The association between TRPM8 expression and patient's survival rate was evaluated using the Kaplan-Meier method and multivariate Cox regression analysis, respectively. The expression levels of TRPM8 mRNA in UCB tissues were significantly higher than those in matched noncancerous tissues (P=0.016). Expression of TRPM8 protein in UCB was significantly and positively associated with histological grade (P=0.039) and tumor stage (P=0.037). Significant correlation between high TRPM8 expression and poor cumulative survival of UCB patients was shown using the Kaplan-Meier survival curve (P=0.039). TRPM8 was represented as an independent prognostic biomarker for UCB patients by multivariate Cox regression analysis (P=0.047). The present study provide the convincing evidence for the first time that over-expression of TRPM8 may play a role in the pathogenesis and progression of UCB, and TRPM8 may serve as an independent prognostic biomarker for UCB patients.

Emerging molecularly targeted therapies in castration refractory prostate cancer.

Androgen deprivation therapy (ADT) with medical or surgical castration is the mainstay of therapy in men with metastatic prostate cancer. However, despite initial responses, almost all men eventually develop castration refractory metastatic prostate cancer (CRPC) and die of their disease. Over the last decade, it has been recognized that despite the failure of ADT, most prostate cancers maintain some dependence on androgen and/or androgen receptor (AR) signaling for proliferation. Furthermore, androgen independent molecular pathways have been identified as drivers of continued progression of CRPC. Subsequently, drugs have been developed targeting these pathways, many of which have received regulatory approval. Agents such as abiraterone, enzalutamide, orteronel (TAK-700), and ARN-509 target androgen signaling. Sipuleucel-T, ipilimumab, and tasquinimod augment immune-mediated tumor killing. Agents targeting classic tumorogenesis pathways including vascular endothelial growth factor, hepatocyte growth factor, insulin like growth factor-1, tumor suppressor, and those which regulate apoptosis and cell cycles are currently being developed. This paper aims to focus on emerging molecular pathways underlying progression of CRPC, and the drugs targeting these pathways, which have recently been approved or have reached advanced stages of development in either phase II or phase III clinical trials.

KIT signaling governs differential sensitivity of mature and primitive CML progenitors to tyrosine kinase inhibitors.

Imatinib and other BCR-ABL1 inhibitors are effective therapies for chronic myelogenous leukemia (CML), but these inhibitors target additional kinases including KIT, raising the question of whether off-target effects contribute to clinical efficacy. On the basis of its involvement in CML pathogenesis, we hypothesized that KIT may govern responses of CML cells to imatinib. To test this, we assessed the growth of primary CML progenitor cells under conditions of sole BCR-ABL1, sole KIT, and dual BCR-ABL1/KIT inhibition. Sole BCR-ABL1 inhibition suppressed mature CML progenitor cells, but these effects were largely abolished by stem cell factor (SCF) and maximal suppression required dual BCR-ABL1/KIT inhibition. In contrast, KIT inhibition did not add to the effects of BCR-ABL1 inhibition in primitive progenitors, represented by CD34(+)38(-) cells. Long-term culture-initiating cell assays on murine stroma revealed profound depletion of primitive CML cells by sole BCR-ABL1 inhibition despite the presence of SCF, suggesting that primitive CML cells are unable to use SCF as a survival factor upon BCR-ABL1 inhibition. In CD34(+)38(+) cells, SCF strongly induced pAKT(S473) in a phosphoinositide 3-kinase (PI3K)-dependent manner, which was further enhanced by inhibition of BCR-ABL1 and associated with increased colony survival. In contrast, pAKT(S473) levels remained low in CD34(+)38(-) cells cultured under the same conditions. Consistent with reduced response to SCF, KIT surface expression was significantly lower on CD34(+)38(-) compared with CD34(+)38(+) CML cells, suggesting a possible mechanism for the differential effects of SCF on mature and primitive CML progenitor cells.

Hepcidin mediates transcriptional changes that modulate acute cytokine-induced inflammatory responses in mice.

Hepcidin is a peptide hormone that regulates iron homeostasis and acts as an antimicrobial peptide. It is expressed and secreted by a variety of cell types in response to iron loading and inflammation. Hepcidin mediates iron homeostasis by binding to the iron exporter ferroportin, inducing its internalization and degradation via activation of the protein kinase Jak2 and the subsequent phosphorylation of ferroportin. Here we have shown that hepcidin-activated Jak2 also phosphorylates the transcription factor Stat3, resulting in a transcriptional response. Hepcidin treatment of ferroportin-expressing mouse macrophages showed changes in mRNA expression levels of a wide variety of genes. The changes in transcript levels for half of these genes were a direct effect of hepcidin, as shown by cycloheximide insensitivity, and dependent on the presence of Stat3. Hepcidin-mediated transcriptional changes modulated LPS-induced transcription in both cultured macrophages and in vivo mouse models, as demonstrated by suppression of IL-6 and TNF-alpha transcript and secreted protein. Hepcidin-mediated transcription in mice also suppressed toxicity and morbidity due to single doses of LPS, poly(I:C), and turpentine, which is used to model chronic inflammatory disease. Most notably, we demonstrated that hepcidin pretreatment protected mice from a lethal dose of LPS and that hepcidin-knockout mice could be rescued from LPS toxicity by injection of hepcidin. The results of our study suggest a new function for hepcidin in modulating acute inflammatory responses.

Macrophages from 11beta-hydroxysteroid dehydrogenase type 1-deficient mice exhibit an increased sensitivity to lipopolysaccharide stimulation due to TGF-beta-mediated up-regulation of SHIP1 expression.

11beta-Hydroxysteroid dehydrogenase type 1 (11betaHSD1) performs end-organ metabolism of glucocorticoids (GCs) by catalyzing the conversion of C(11)-keto-GCs to C(11)-hydroxy-GCs, thereby generating activating ligands for the GC receptor. In this study, we report that 11betaHSD1(-/-) mice are more susceptible to endotoxemia, evidenced by increased weight loss and serum TNF-alpha, IL-6, and IL-12p40 levels following LPS challenge in vivo. Peritoneal and splenic macrophage (splnMphi) from these genetically altered mice overproduce inflammatory cytokines following LPS stimulation in vitro. Inflammatory cytokine overexpression by 11betaHSD1(-/-) splnMphi results from an increased activation of NF-kappaB- and MAPK-signaling cascades and an attenuated PI3K-dependent Akt activation. The expression of SHIP1 is augmented in 11betaHSD1(-/-) Mphi and contributes to inflammatory cytokine production because overexpression of SHIP1 in primary bone marrow Mphi (BMMphi) leads to a similar type of hyperresponsiveness to subsequent LPS stimulation. 11betaHSD1(+/+) and 11betaHSD1(-/-) BMMphi responded to LPS similarly. However, 11betaHSD1(-/-) BMMphi derived in the presence of elevated GC levels up-regulated SHIP1 expression and increased their capacity to produce inflammatory cytokines following their activation with LPS. These observations suggest the hyperresponsiveness of 11betaHSD1(-/-) splnMphi results from myeloid cell differentiation in the presence of moderately elevated GC levels found within 11betaHSD1(-/-) mice. GC-conditioning of BMMphi enhanced SHIP1 expression via up-regulation of bioactive TGF-beta. Consistently, TGF-beta protein expression was increased in unstimulated CD11b(-) cells residing in the BM and spleen of 11betaHSD1(-/-) mice. Our results suggest that modest elevations in plasma GC levels can modify the LPS responsiveness of Mphi by augmenting SHIP1 expression through a TGF-beta-dependent mechanism.

Glucocorticoid conditioning of myeloid progenitors enhances TLR4 signaling via negative regulation of the phosphatidylinositol 3-kinase-Akt pathway.

The immunomodulatory effects of glucocorticoids (GCs) have been described as bimodal, with high levels of GCs exerting immunosuppressive effects and low doses of GCs being immunopermissive. While the mechanisms used by GCs to achieve immunosuppression have been investigated intensely, the molecular mechanisms underlying the permissive effects of GCs remain uncharacterized. Herein, we demonstrate that GC conditioning during the differentiation of myeloid progenitors into macrophages (Mphis) results in their enhanced LPS responsiveness, demonstrated by an overexpression of the inflammatory cytokines TNF-alpha, IL-6, and IL-12. Inflammatory cytokine overexpression resulted from an increased activation of NF-kappaB and the MAPK signaling cascade and a reduced activation of the PI3K-Akt pathway following LPS stimulation. GC conditioning during Mphi differentiation induced an increase in the expression of SHIP1, a phosphatase that negatively regulates the PI3K signaling pathway. Small interfering RNA-mediated knockdown of SHIP1 expression increased PI3K-dependent Akt activation and subsequently decreased inflammatory cytokine expression, suggesting GC-mediated up-regulation of SHIP1 expression is responsible for the augmentation in inflammatory cytokine production following LPS stimulation. We also show that splenic Mphis purified from normal mice that were implanted with timed-release GC pellets exhibited an enhanced LPS responsiveness and increased SHIP1 expression, indicating that GCs can regulate SHIP1 expression in vivo. Our results suggest that minor fluctuations in physiological levels of endogenous GCs can program endotoxin-responsive hemopoietic cells during their differentiation by regulating their sensitivity to stimulation.

The expression of 11 beta-hydroxysteroid dehydrogenase type I by lymphocytes provides a novel means for intracrine regulation of glucocorticoid activities.

The 11beta-hydroxysteroid dehydrogenase (11beta-HSD) enzymes control the interconversion of active glucocorticoids (GCS) and their inactive 11-keto metabolites, a process commonly referred to as the cortisone/cortisol shuttle. Although the prereceptor metabolism of GCS by 11beta-HSD is well documented in a variety of cells and tissues, it has not yet been carefully investigated in the major cell types of the immune system. In this study, we demonstrate that 11beta-HSD1 transcripts, protein, and enzyme activities are actively expressed in murine CD4(+), CD8(+), and B220(+) lymphocytes, as well as CD11c(+) dendritic cells. Only reductase activity was observed in living cells, evidenced by the restricted conversion of cortisone to cortisol. Activation of CD4(+) T cells increased their 11beta-HSD1 activity, as did their polarization into Th1 or Th2 cells. CD4(+) T cells isolated from aged donors (>16 mo) had increased 11beta-HSD1 protein and an elevated capacity to convert cortisone to cortisol. The GCS generated in murine CD4(+) T cells from their inactive 11-keto metabolites could activate the GCS receptor, demonstrated by an up-regulation of IL-7Ralpha and GCS-induced leucine zipper gene expression. The presence of a functional 11beta-HSD1 provides lymphocytes with a novel intracrine regulatory mechanism that could influence such processes as lymphocyte development, effector function, and susceptibility to apoptosis. Thus, the presence of 11beta-HSD1 provides an additional means to facilitate GCS influences over lymphocyte activities, uncoupled from the plasma concentration of GCS.

Peroxisome proliferator-activated receptor alpha negatively regulates T-bet transcription through suppression of p38 mitogen-activated protein kinase activation.

Expression of the nuclear hormone receptor peroxisome proliferator-activated receptor alpha (PPARalpha) in resting lymphocytes was recently established, although the physiologic role(s) played by this nuclear hormone receptor in these cell types remains unresolved. In this study, we used CD4(+) T cells isolated from PPARalpha(-/-) and wild-type mice, as well as cell lines that constitutively express PPARalpha, in experiments designed to evaluate the role of this hormone receptor in the regulation of T cell function. We report that activated CD4(+) T cells lacking PPARalpha produce increased levels of IFN-gamma, but significantly lower levels of IL-2 when compared with activated wild-type CD4(+) T cells. Furthermore, we demonstrate that PPARalpha regulates the expression of these cytokines by CD4(+) T cells in part, through its ability to negatively regulate the transcription of T-bet. The induction of T-bet expression in CD4(+) T cells was determined to be positively influenced by p38 mitogen-activated protein (MAP) kinase activation, and the presence of unliganded PPARalpha effectively suppressed the phosphorylation of p38 MAP kinase. The activation of PPARalpha with highly specific ligands relaxed its capacity to suppress p38 MAP kinase phosphorylation and promoted T-bet expression. These results demonstrate a novel DNA-binding independent and agonist-controlled regulatory influence by the nuclear hormone receptor PPARalpha.