Microenvironmental CXCL12 deletion enhances Flt3-ITD acute myeloid leukemia stem cell response to therapy by reducing p38 MAPK signaling

Pharmacological p38 MAPK inhibitor SB203580 enhances AML stem cell line KG1a chemosensitivity to daunorubicin by promoting late apoptosis, cell growth arrest in S-phase, and miR-328-3p upregulation

Acute myeloid leukaemia (AML) is characterized by uncontrolled proliferation of myeloid progenitor cells and impaired maturation, leading to immature cell accumulation in the bone marrow and bloodstream, resulting in hematopoietic dysfunction. Chemoresistance, hyperactivity of survival pathways, and miRNA alteration are major factors contributing to treatment failure and poor outcomes in AML patients. This study aimed to investigate the impact of the pharmacological p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 on the chemoresistance potential of AML stem cell line KG1a to the therapeutic drug daunorubicin (DNR). KG1a and chemosensitive leukemic HL60 cells were treated with increasing concentrations of DNR. Cell Titer-Glo®, flow cytometry, phosphokinase and protein arrays, Western blot technology, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were employed for assessment of cell viability, half-maximal inhibitory concentration (IC50) determination, apoptotic status detection, cell cycle analysis, apoptosis-related protein and gene expression monitoring. Confocal microscopy was used to visualize caspase and mitochondrial permeability transition pore (mPTP) activities. Exposed at various incubation times, higher DNR IC50 values were determined for KG1a cells than for HL60 cells, confirming KG1a cell chemoresistance potential. Exposed to DNR, late apoptosis induction in KG1a cells was enhanced after SB203580 pretreatment, defined as the combination treatment. This enhancement was confirmed by increased cleavage of poly(ADP-ribose) polymerase, caspase-9, caspase-3, and augmented caspase-3/-7 and mPTP activities in KG1a cells upon combination treatment, compared to DNR. Using phosphokinase and apoptosis protein arrays, the combination treatment decreased survival Akt phosphorylation and anti-apoptotic Bcl-2 expression levels in KG1a cells while increasing the expression levels of the tumor suppressor p53 and cyclin-dependent kinase inhibitor p21, compared to DNR. Cell cycle analysis revealed KG1a cell growth arrest in G2/M-phase caused by DNR, while combined treatment led to cell growth arrest in S-phase, mainly associated with cyclin B1 expression levels. Remarkably, the enhanced KG1a cell sensitivity to DNR after SB203580 pretreatment was associated with an increased upregulation of miR-328-3p and slight downregulation of miR-26b-5p, compared to DNR effect. Altogether, these findings could contribute to the development of a new therapeutic strategy by targeting the p38 MAPK pathway to improve treatment outcomes in patients with refractory or relapsed AML.

Immunotherapies of acute myeloid leukemia: Rationale, clinical evidence and perspective

Acute myeloid leukemia (AML) is a prevalent hematological malignancy that exhibits a wide array of molecular abnormalities. Although traditional treatment modalities such as chemotherapy and allogeneic stem cell transplantation (HSCT) have become standard therapeutic approaches, a considerable number of patients continue to face relapse and encounter a bleak prognosis. The emergence of immune escape, immunosuppression, minimal residual disease (MRD), and other contributing factors collectively contribute to this challenge. Recent research has increasingly highlighted the notable distinctions between AML tumor microenvironments and those of healthy individuals. In order to investigate the potential therapeutic mechanisms, this study examines the intricate transformations occurring between leukemic cells and their surrounding cells within the tumor microenvironment (TME) of AML. This review classifies immunotherapies into four distinct categories: cancer vaccines, immune checkpoint inhibitors (ICIs), antibody-based immunotherapies, and adoptive T-cell therapies. The results of numerous clinical trials strongly indicate that the identification of optimal combinations of novel agents, either in conjunction with each other or with chemotherapy, represents a crucial advancement in this field. In this review, we aim to explore the current and emerging immunotherapeutic methodologies applicable to AML patients, identify promising targets, and emphasize the crucial requirement to augment patient outcomes. The application of these strategies presents substantial therapeutic prospects within the realm of precision medicine for AML, encompassing the potential to ameliorate patient outcomes.

Emerging and Future Targeted Therapies for Pediatric Acute Myeloid Leukemia: Targeting the Leukemia Stem Cells

Acute myeloid leukemia (AML) is a rare subtype of acute leukemia in the pediatric and adolescent population but causes disproportionate morbidity and mortality in this age group. Standard chemotherapeutic regimens for AML have changed very little in the past 3-4 decades, but the addition of targeted agents in recent years has led to improved survival in select subsets of patients as well as a better biological understanding of the disease. Currently, one key paradigm of bench-to-bedside practice in the context of adult AML is the focus on leukemia stem cell (LSC)-targeted therapies. Here, we review current and emerging immunotherapies and other targeted agents that are in clinical use for pediatric AML through the lens of what is known (and not known) about their LSC-targeting capability. Based on a growing understanding of pediatric LSC biology, we also briefly discuss potential future agents on the horizon.

The interplay of FLT3 and CXCR4 in acute myeloid leukemia: an ongoing debate

FLT3 mutations are very frequent in AML and utilization of FLT3 inhibitors as approved treatment options are very common. Despite the initial success of inhibitor treatment, the development of resistances against this treatment is a major challenge in AML therapy. One of the mechanisms causing resistance is the homing of the leukemic cells in the protective niche of the bone marrow microenvironment (BMM). A pathway mediating homing to the BMM and leukemic cell survival is the CXCL12/CXCR4 axis. The analysis of patient samples in several independent studies indicated that FLT3-ITD expression led to higher CXCR4 surface expression. However, several in vitro studies reported contradictory findings, suggesting that FLT3-ITD signaling negatively influenced CXCR4 expression. In this commentary, we provide an overview summarizing the studies dealing with the relationship of FLT3 and CXCR4. Taken together, the current research status is not sufficient to answer the question whether FLT3 and CXCR4 act together or independently in leukemia progression. Systematic analyses in model cell systems are needed to understand the interplay between FLT3 and CXCR4, since this knowledge could lead to the development of more effective treatment strategies for AML patients.

Comparison of Quantitative Mass Spectrometric Methods for Drug Target Identification by Thermal Proteome Profiling

Thermal proteome profiling (TPP) provides a powerful approach to studying proteome-wide interactions of small therapeutic molecules and their target and off-target proteins, complementing phenotypic-based drug screens. Detecting differences in thermal stability due to target engagement requires high quantitative accuracy and consistent detection. Isobaric tandem mass tags (TMTs) are used to multiplex samples and increase quantification precision in TPP analysis by data-dependent acquisition (DDA). However, advances in data-independent acquisition (DIA) can provide higher sensitivity and protein coverage with reduced costs and sample preparation steps. Herein, we explored the performance of different DIA-based label-free quantification approaches compared to TMT-DDA for thermal shift quantitation. Acute myeloid leukemia cells were treated with losmapimod, a known inhibitor of MAPK14 (p38α). Label-free DIA approaches, and particularly the library-free mode in DIA-NN, were comparable of TMT-DDA in their ability to detect target engagement of losmapimod with MAPK14 and one of its downstream targets, MAPKAPK3. Using DIA for thermal shift quantitation is a cost-effective alternative to labeled quantitation in the TPP pipeline.

HMGB3 promotes the malignant phenotypes and stemness of epithelial ovarian cancer through the MAPK/ERK signaling pathway

BACKGROUND

Ovarian cancer, particularly epithelial ovarian cancer (EOC), is the leading cause of cancer-related mortality among women. Our previous study revealed that high HMGB3 levels are associated with poor prognosis and lymph node metastasis in patients with high-grade serous ovarian carcinoma; however, the role of HMGB3 in EOC proliferation and metastasis remains unknown.

METHODS

MTT, clonogenic, and EdU assays were used to assess cell proliferation. Transwell assays were performed to detect cell migration and invasion. Signaling pathways involved in HMGB3 function were identified by RNA sequencing (RNA-seq). MAPK/ERK signaling pathway protein levels were evaluated by western blot.

RESULTS

HMGB3 knockdown inhibited ovarian cancer cell proliferation and metastasis, whereas HMGB3 overexpression facilitated these processes. RNA-seq showed that HMGB3 participates in regulating stem cell pluripotency and the MAPK signaling pathway. We further proved that HMGB3 promotes ovarian cancer stemness, proliferation, and metastasis through activating the MAPK/ERK signaling pathway. In addition, we demonstrated that HMGB3 promotes tumor growth in a xenograft model via MAPK/ERK signaling.

CONCLUSIONS

HMGB3 promotes ovarian cancer malignant phenotypes and stemness through the MAPK/ERK signaling pathway. Targeting HMGB3 is a promising strategy for ovarian cancer treatment that may improve the prognosis of women with this disease. Video Abstract.