Chimeric antigen receptor T (CAR-T) cell therapies have transformed the treatment of relapsed/refractory (R/R) B-cell malignancies and multiple myeloma by redirecting activated T cells to CD19- or BCMA-expressing tumor cells. However, this approach has yet to be approved for acute myeloid leukemia (AML), the most common acute leukemia in adults and the elderly. Simultaneously, CAR-T cell therapies continue to face significant challenges in the treatment of solid tumors. The primary challenge in developing CAR-T cell therapies for AML is the absence of an ideal target antigen that is both effective and safe, as AML cells share most surface antigens with healthy hematopoietic stem and progenitor cells (HSPCs). Simultaneously targeting antigen expression on both AML cells and HSPCs may result in life-threatening on-target/off-tumor toxicities such as prolonged myeloablation. In addition, the immunosuppressive nature of the AML tumor microenvironment has a detrimental effect on the immune response. This review begins with a comprehensive overview of CAR-T cell therapy for cancer, covering the structure of CAR-T cells and the history of their clinical application. It then explores the current landscape of CAR-T cell therapy in both hematologic malignancies and solid tumors. Finally, the review delves into the specific challenges of applying CAR-T cell therapy to AML, highlights ongoing global clinical trials, and outlines potential future directions for developing effective CAR-T cell-based treatments for relapsed/refractory AML.

Prognostic value of measurable residual disease (MRD) for venetoclax in combination with

Background: Even though venetoclax in combination with azacitidine (VenAza) is considered a low-intensity regimen, its patients present a high incidence of cytopenia and infections during the first courses, making the initial management a challenging phase. Methods: This difficulty in our center led to the establishment of an At-Home (AH) program for ramp-up and follow-up patients during the VenAza combination induction phase focused on therapy administration, patient and caregiver education, and management of adverse events (AEs). A total of 70 patients with newly diagnosed acute myeloid leukemia (ND-AML) or relapsed/refractory AML (R/R AML) were treated with VenAza from March 2019 to May 2022. We compared outcomes between patients managed with a hospital-based (inpatient) approach and those managed through the AH program. Results: Despite most patients experiencing grade 3–4 cytopenias (96.9%), the incidence of serious infections and other AEs was comparable between both groups, with no significant difference in febrile neutropenia (42.3% vs. 27.8%, p = 0.38). Overall, the AH cohort demonstrated a significantly lower hospital readmission rate after ramp-up (29.5% vs. 84.6%, p = 0.001). Moreover, the inpatient cohort’s admission days were longer than in the AH cohort (13 vs. 8, p = 0.28). Conclusions: AH management was feasible and safe, leading to better resource use, enhanced patient comfort, and improved treatment compliance. The potential of AH programs for managing low-intensity chemotherapy regimens can reduce hospital admissions and subsequently improve patient and caregiver well-being.

A specialized microenvironment in the bone marrow, composed of stromal cells including mesenchymal stem cells (MSCs), support hematopoietic stem cells (HSCs) self-renewal and differentiation but also regulates leukemia development and progression. The reciprocal direct interaction between MSCs and CD34+ HSCs under physiological and pathological conditions has not been well characterized yet. Here, we established a direct co-culture model between MSCs and CD34+ HSCs or MSCs and acute myeloid leukemia cells (THP-1, Molm-13, and primary cells from patients) to study cell-cell communication. Following MSCs-CD34+ HSCs co-culture, the expression of adhesion markers N-cadherin and connexin 43 increased in both cell types, forming gap junction channels. Moreover, the clonogenic potential of CD34+ HSCs was increased. However, direct contact of acute myeloid leukemia cells with MSCs reduced the expression levels of connexin 43 and N-cadherin in MSCs. The impairment in gap junction formation could be ascertained to a defect in the acute myeloid leukemia derived MSCs. Interestingly, CD34+ HSCs and acute myeloid leukemia cell lines restrained MSCs from engaging into osteoblastic differentiation upon prolonged direct cell-cell contact. In conclusion, under physiological conditions, connexin 43 and N-cadherin interaction preserves stemness of both CD34+ HSCs and MSCs, a process that is compromised in acute myeloid leukemia, pointing out to the possible role of gap junctions in modulating stemness.

Background/Objectives: A specialized microenvironment in the bone marrow, composed of stromal cells including mesenchymal stem cells (MSCs), supports hematopoietic stem cell (HSC) self-renewal, and differentiation bands play an important role in leukemia development and progression. The reciprocal direct interaction between MSCs and CD34⁺ HSCs under physiological and pathological conditions is yet to be fully characterized. Methods: Here, we established a direct co-culture model between MSCs and CD34⁺ HSCs or MSCs and acute myeloid leukemia cells (THP-1, Molm-13, and primary cells from patients) to study heterocellular communication. Results: Following MSCs-CD34⁺ HSCs co-culture, the expression of adhesion markers N-Cadherin and connexin 43 increased in both cell types, forming gap junction channels. Moreover, the clonogenic potential of CD34⁺ HSCs was increased. However, direct contact of acute myeloid leukemia cells with MSCs reduced the expression levels of connexin 43 and N-Cadherin in MSCs. The impairment in gap junction formation may potentially be due to a defect in the acute myeloid leukemia-derived MSCs. Interestingly, CD34⁺ HSCs and acute myeloid leukemia cell lines attenuated MSC osteoblastic differentiation upon prolonged direct cell–cell contact. Conclusions: In conclusion, under physiological conditions, connexin 43 and N-Cadherin interaction preserves stemness of both CD34⁺ HSCs and MSCs, a process that is compromised in acute myeloid leukemia, pointing to the possible role of gap junctions in modulating stemness.