60 Years Young: The Evolving Role of Allogeneic Hematopoietic Stem Cell Transplantation in Cancer Immunotherapy

Post-transplant cyclophosphamide compared to sirolimus/tacrolimus in reduced intensity conditioning transplants for patients with lymphoid malignancies

Despite novel cellular and immunomodulatory therapies, allogeneic hematopoietic stem cell transplantation (HSCT) remains a treatment option for lymphoid malignancies. Post-transplant cyclophosphamide (PTCY) is increasingly employed for graft vs. host disease (GVHD) prophylaxis. This study aims to evaluate the safety and efficacy of PTCY in reduce intensity (RIC) HSCT for patients with lymphoid neoplasms compared to sirolimus with tacrolimus (SIR/TAC). The primary endpoint was to compare grade III-IV acute GVHD, severe chronic GVHD, and relapse-free survival (GRFS) between the two GVHD prophylaxis strategies. This study, conducted from January 2012 to December 2020, included 171 consecutive patients (82 in the PTCY and 89 in the SIR/TAC group). Results revealed a significantly decreased incidence of moderate and severe forms of chronic GVHD in PTCY cohort (5.8% [95% CI, 1.8 to 13.1]) versus the SIR/TAC cohort (39.6% [95% CI, 29.3 to 49.7] (p < 0.001)). Other outcomes, including GRFS (PTCY [45.9% (95% CI, 35.8-58.7)] and SIR/TAC groups [36.8% (95% CI, 28-48.4)], (p = 0.72)), non-relapse mortality (NRM), relapse and overall survival (OS) were similar in both groups. Interestingly, the failure to achieve GRFS was mainly attributed to GVHD in the SIR/TAC group, while disease relapse was the primary reason in the PTCY cohort.

Single-cell genomics-based immune and disease monitoring in blood malignancies

Achieving long-term disease control using therapeutic immunomodulation is a long-standing concept with a strong tradition in blood malignancies. Besides allogeneic hematopoietic stem cell transplantation that continues to provide potentially curative treatment for otherwise challenging diagnoses, recent years have seen impressive progress in immunotherapies for leukemias and lymphomas with immune checkpoint blockade, bispecific monoclonal antibodies, and CAR T cell therapies. Despite their success, non-response, relapse, and immune toxicities remain frequent, thus prioritizing the elucidation of the underlying mechanisms and identifying predictive biomarkers. The increasing availability of single-cell genomic tools now provides a system's immunology view to resolve the molecular and cellular mechanisms of immunotherapies at unprecedented resolution. Here, we review recent studies that leverage these technological advancements for tracking immune responses, the emergence of immune resistance, and toxicities. As single-cell immune monitoring tools evolve and become more accessible, we expect their wide adoption for routine clinical applications to catalyze more precise therapeutic steering of personal immune responses.

Cell-free RNA Liquid Biopsy to Monitor Hematopoietic Stem Cell Transplantation

Hematopoietic Stem Cell Transplantation (HSCT) is one of the oldest and most successful immunotherapies. Yet, despite long-standing success in the use of HSCT for the treatment of blood cancers and severe immune disorders, monitoring post-transplant complications remains a challenge due to a lack of informative diagnostic tests. Here, we investigate the utility of cell-free RNA (cfRNA) in plasma as a liquid biopsy to monitor allogeneic HSCT recipients during and after treatment. We assayed longitudinal samples from 92 HSCT recipients by cfRNA sequencing and show that cfRNA provides insight into treatment and recovery trajectories, immune dynamics in response to transplantation, infection, and solid-tissue injury associated with Graft-Versus-Host Disease. Collectively, our results provide support for the use of plasma cfRNA profiling to monitor complications of HSCT.

Sleep Quality in Patients With Ocular Graft-Versus-Host Disease After Allogeneic Hematopoietic Stem Cell Transplantation

OBJECTIVES

To investigate the sleep quality in patients with ocular graft-versus-host disease (oGVHD) compared with patients without oGVHD after allogeneic hematopoietic stem cell transplantation (alloHCT) and healthy controls.

METHODS

This cross-sectional study analyzed 142 patients after alloHCT including 94 patients with oGVHD and 48 without. Fifty healthy controls were also enrolled. oGVHD was diagnosed according to International Chronic Ocular GVHD Consensus Group (ICOGCG) criteria. Sleep quality was assessed by the Chinese version of the Pittsburgh Sleep Quality Index (CPSQI). Poor sleep quality was defined as CPQSI score greater than 6.

RESULTS

Patients after alloHCT demonstrated a significantly higher CPQSI score than those of controls {7.0 [interquartile range (IQR) 5.0-10.0] vs. 5.5 [IQR 4.8-7.0], P =0.002}, especially in the oGVHD subgroup (7.5 [IQR 5.0-11.0] vs. 6.0 [IQR 5.0-8.0], P =0.04) with nearly double prevalence of poor sleep quality (58 [62%] vs. 18 [37%], P =0.006). Poor sleep quality was strikingly correlated with oGVHD diagnosis (adjusted odds ratio [OR]=2.55, 95% confidence interval [CI]: 1.02-6.34, P =0.04) and systemic immunosuppressants (adjusted OR=2.61, 95% CI: 1.32-5.71, P =0.02). Among the ocular parameters, poor sleep quality was significantly associated with higher ICOGCG score (adjusted OR=1.20, 95% CI: 1.03-1.39, P =0.02) and lower tear film break-up time (adjusted OR=0.85, 95% CI: 0.74-0.99, P =0.05).

CONCLUSIONS

Poor sleep quality was associated with an increased severity of oGVHD and tear film instability in the long-term alloHCT survivorship.

Coordinated Immune Cell Networks in the Bone Marrow Microenvironment Define the Graft versus Leukemia Response with Adoptive Cellular Therapy

Understanding how intra-tumoral immune populations coordinate to generate anti-tumor responses following therapy can guide precise treatment prioritization. We performed systematic dissection of an established adoptive cellular therapy, donor lymphocyte infusion (DLI), by analyzing 348,905 single-cell transcriptomes from 74 longitudinal bone-marrow samples of 25 patients with relapsed myeloid leukemia; a subset was evaluated by protein-based spatial analysis. In acute myelogenous leukemia (AML) responders, diverse immune cell types within the bone-marrow microenvironment (BME) were predicted to interact with a clonally expanded population of ZNF683 + GZMB + CD8+ cytotoxic T lymphocytes (CTLs) which demonstrated in vitro specificity for autologous leukemia. This population, originating predominantly from the DLI product, expanded concurrently with NK and B cells. AML nonresponder BME revealed a paucity of crosstalk and elevated TIGIT expression in CD8+ CTLs. Our study highlights recipient BME differences as a key determinant of effective anti-leukemia response and opens new opportunities to modulate cell-based leukemia-directed therapy.

Artificial intelligence methods to estimate overall mortality and non-relapse mortality following allogeneic HCT in the modern era: an EBMT-TCWP study

Allogeneic haematopoietic cell transplantation (alloHCT) has curative potential counterbalanced by its toxicity. Prognostic scores fail to include current era patients and alternative donors. We examined adult patients from the EBMT registry who underwent alloHCT between 2010 and 2019 for oncohaematological disease. Our primary objective was to develop a new prognostic score for overall mortality (OM), with a secondary objective of predicting non-relapse mortality (NRM) using the OM score. AI techniques were employed. The model for OM was trained, optimized, and validated using 70%, 15%, and 15% of the data set, respectively. The top models, "gradient boosting" for OM (AUC = 0.64) and "elasticnet" for NRM (AUC = 0.62), were selected. The analysis included 33,927 patients. In the final prognostic model, patients with the lowest score had a 2-year OM and NRM of 18 and 13%, respectively, while those with the highest score had a 2-year OM and NRM of 82 and 93%, respectively. The results were consistent in the subset of the haploidentical cohort (n = 4386). Our score effectively stratifies the risk of OM and NRM in the current era but do not significantly improve mortality prediction. Future prognostic scores can benefit from identifying biological or dynamic markers post alloHCT.

Patient and Physician Preferences for Acute Myeloid Leukemia Maintenance Treatments Following Hematopoietic Stem Cell Transplantation

Purpose

This study assessed and compared preferences for treatment attributes of maintenance therapies post-hematopoietic stem cell transplantation (HSCT) in patients with acute myeloid leukemia (AML) and in physicians who treat these patients.

Patients and Methods

Patients with AML post HSCT and physicians from the United States, United Kingdom, Canada, and Australia (physicians only) completed a web-based discrete choice experiment (DCE). The DCE used inputs identified via a targeted literature review and qualitative interviews to ascertain relevant treatment attributes and associated levels. Six treatment attributes were selected (chance of 2-year relapse-free survival, quality of life [QoL], risk of serious infections, risk of nausea, chance of achieving transfusion independence, and duration of hospitalization annually), each with three or four levels. The experimental design included 36 choice tasks that presented a pair of hypothetical treatment profiles with varying attribute levels; participants chose a preferred treatment for each choice task. Choice tasks were divided into three blocks of 12 tasks each in the patient survey and 4 blocks of 9 tasks each in the physician survey; survey participants were randomly assigned to one of the blocks. Random parameter logit regression models were used to assess the impact of stated attributes on preferences for maintenance treatment post HSCT.

Results

Surveys from 84 patients and 149 physicians were assessed. For patients, QoL was the most important attribute, followed by duration of hospitalization and chance of 2-year relapse-free survival. For physicians, chance of 2-year relapse-free survival was the most important attribute, followed by QoL and risk of serious infections.

Conclusion

Differences in how patients and physicians valued post-HSCT maintenance treatment attributes were identified. These differences suggest that patient-centered decision-making may help physicians choose maintenance treatments for patients with AML post HSCT that better meet their treatment needs and improve their treatment satisfaction.

Decisional Regret in Long-Term Australian Allogeneic Hematopoietic Stem Cell Transplantation Survivors: A Cross-Sectional Survey

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an intensive but effective treatment for malignant and non-malignant diseases. However, long-term survival often comes at a cost, with survivors experiencing chronic morbidity and are at risk of relapse and secondary malignancy. This study aimed to describe decisional regret in a large cohort of Australian long-term allo-HSCT survivors. A cross-sectional survey was conducted with 441 adults in New South Wales, assessing quality of life (QoL), psychological, social, demographic, and clinical variables. Less than 10% of survivors expressed regret, with chronic graft-versus-host disease being the most important clinical factor. Psycho-socioeconomic factors such as depression, lower QoL scores, lower household income, higher treatment burden, and not resuming sex post-HSCT were also associated with regret. Findings highlight the need for valid informed consent and ongoing follow-up and support for allo-HSCT survivors dealing with life post-transplant. Nurses and healthcare professionals play a critical role in addressing decisional regret in these patients.

Nestin+ Mesenchymal Stromal Cells Fibrotic Transition Mediated by CD169+ Macrophages in Bone Marrow Chronic Graft-versus-Host Disease

Chronic graft-versus-host disease (cGVHD) involves multiple organs, but little is known about bone marrow (BM) alterations caused by cGVHD. In mice and humans, we found that cGVHD is associated with BM fibrosis resulting in T cell infiltration, IgG deposition, and hematopoietic dysfunction. Macrophages and Nestin+ mesenchymal stromal cells (MSCs) participated in the process of BM fibrosis during BM cGVHD development. BM macrophage numbers were significantly increased in mice and humans with BM fibrosis associated with cGVHD. Amplified macrophages produced TGF-β1, which recruited Nestin+ MSCs forming clusters, and Nestin+ MSCs later differentiated into fibroblasts, a process mediated by increased TGF-β/Smad signaling. TLR4/MyD88-mediated activation of endoplasmic reticulum (ER) stress in macrophages is associated with fibrosis by increasing Nestin+ MSC migration and differentiation into fibroblasts. Depletion of macrophages by clodronate-containing liposomes and inhibition of ER stress by 4-phenylbutyric acid reversed BM fibrosis by inhibiting fibroblast differentiation. These studies provide insights into the pathogenesis of BM fibrosis during cGVHD development.

The delicate balance of graft versus leukemia and graft versus host disease after allogeneic hematopoietic stem cell transplantation

INTRODUCTION

The curative basis of allogeneic hematopoietic stem cell transplantation (HSCT) relies in part upon the graft versus leukemia (GvL) effect, whereby donor immune cells recognize and eliminate recipient malignant cells. However, alloreactivity of donor cells against recipient tissues may also be deleterious. Chronic graft versus host disease (cGvHD) is an immunologic phenomenon wherein alloreactive donor T cells aberrantly react against host tissues, leading to damaging inflammatory symptoms.

AREAS COVERED

Here, we discuss biological insights into GvL and cGvHD and strategies to balance the prevention of GvHD with maintenance of GvL in modern HSCT.

EXPERT OPINION/COMMENTARY

Relapse remains the leading cause of mortality after HSCT with rates as high as 40% for some diseases. GvHD is a major cause of morbidity after HSCT, occurring in up to half of patients and responsible for 15-20% of deaths after HSCT. Intriguingly, the development of chronic GvHD may be linked to lower relapse rates after HSCT, suggesting that GvL and GvHD may be complementary sides of the immunologic foundation of HSCT. The ability to fine tune the balance of GvL and GvHD will lead to improvements in survival, relapse rates, and quality of life for patients undergoing HSCT.

Development and application of nanomaterials, nanotechnology and nanomedicine for treating hematological malignancies

Hematologic malignancies (HMs) pose a serious threat to patients' health and life, and the five-year overall survival of HMs remains low. The lack of understanding of the pathogenesis and the complex clinical symptoms brings immense challenges to the diagnosis and treatment of HMs. Traditional therapeutic strategies for HMs include radiotherapy, chemotherapy, targeted therapy and hematopoietic stem cell transplantation. Although immunotherapy and cell therapy have made considerable progress in the last decade, nearly half of patients still relapse or suffer from drug resistance. Recently, studies have emerged that nanomaterials, nanotechnology and nanomedicine show great promise in cancer therapy by enhancing drug targeting, reducing toxicity and side effects and boosting the immune response to promote durable immunological memory. In this review, we summarized the strategies of recently developed nanomaterials, nanotechnology and nanomedicines against HMs and then proposed emerging strategies for the future designment of nanomedicines to treat HMs based on urgent clinical needs and technological progress.

Engineering T cells to suppress acute GVHD and leukemia relapse after allogeneic hematopoietic stem cell transplantation

Acute graft-versus-host disease (aGVHD) limits the therapeutic benefit of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and requires immunosuppressive prophylaxis that compromises antitumor and antipathogen immunity. OX40 is a costimulatory receptor upregulated on circulating T cells in aGVHD and plays a central role in driving the expansion of alloreactive T cells. Here, we show that OX40 is also upregulated on T cells infiltrating GVHD target organs in a rhesus macaque model, supporting the hypothesis that targeted ablation of OX40+ T cells will mitigate GVHD pathogenesis. We thus created an OX40-specific cytotoxic receptor that, when expressed on human T cells, enables selective elimination of OX40+ T cells. Because OX40 is primarily upregulated on CD4+ T cells upon activation, engineered OX40-specific T cells mediated potent cytotoxicity against activated CD4+ T cells and suppressed alloreactive T-cell expansion in a mixed lymphocyte reaction model. OX40 targeting did not inhibit antiviral activity of memory T cells specific to Epstein-Barr virus, cytomegalovirus, and adenoviral antigens. Systemic administration of OX40-targeting T cells fully protected mice from fatal xenogeneic GVHD mediated by human peripheral blood mononuclear cells. Furthermore, combining OX40 targeting with a leukemia-specific chimeric antigen receptor in a single T cell product provides simultaneous protection against leukemia and aGVHD in a mouse xenograft model of residual disease posttransplant. These results underscore the central role of OX40+ T cells in mediating aGVHD pathogenesis and support the feasibility of a bifunctional engineered T-cell product derived from the stem cell donor to suppress both disease relapse and aGVHD following allo-HSCT.

Ruxolitinib on acute graft-versus-host disease prophylaxis after modified donor lymphocyte infusion

OBJECTIVE

To evaluate the effectiveness of ruxolitinib on acute graft-versus-host disease (aGVHD) prophylaxis and its impact on graft-versus-leukemia (GVL) effect in patients after modified donor lymphocyte infusion (mDLI).

METHODS

We retrospectively included patients with relapsed leukemia after allogeneic hematopoietic stem cell transplantation (allo-HSCT) who received ruxolitinib prophylaxis between October 2018 and April 2020. The incidence of aGVHD, disease-free survival (DFS), overall survival (OS), and treatment safety were evaluated.

RESULTS

Seventeen patients were followed up for a median time of 8 months (range: 1-26 months). The incidence of aGVHD on Day 30 after mDLI was 41.2% and ranged from Grade 1 to 4; ten of 17 patients (58.8%) achieved a complete response (CR), and two (11.8%) had a partial response (PR). Cytomegalovirus (CMV) reactivation rate was 23.5%, and the median time from mDLI to CMV reactivation was 48.5 days. The mean DFS and OS after mDLI were 1.0 (95% CI 0.0-3.5) and 9.0 (95% CI 1.2-16.8) months, respectively. The causes of death for 10 patients were leukemia relapse (n = 5), aGVHD and septic shock (n = 3), intracranial lesion (n = 1), and COVID-19 (n = 1).

CONCLUSIONS

We reported encouraging results of ruxolitinib monotherapy in the prevention of aGVHD and maintenance of GVL for post-transplantation relapsed patients, even though being at high risk with poor initial prognosis.

Vision-specific and cancer-specific quality of life in ocular graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

PURPOSE

To compare the vision-specific and cancer-specific quality of life (QOL) between patients with and without ocular graft-versus-host disease (oGVHD) after allogeneic hematopoietic stem cell transplantation (alloHCT).

METHODS

This cross-sectional observational study analyzed 142 patients after alloHCT including 94 patients with oGVHD and 48 without. oGVHD was diagnosed according to International Chronic Ocular GVHD Consensus Group (ICOGCG) criteria. QOL was assessed by using the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25) and the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30).

RESULTS

Compared with non-oGVHD patients, patients with oGVHD had worse vision-specific (NEI VFQ-25: 64.3 ± 20.3 vs. 77.6 ± 19.3, P < 0.001) and cancer-specific (EORTC QLQ-C30: 59.9 ± 20.3 vs. 67.4 ± 17.5, P = 0.03) QOL, as well as impaired cognitive function (72.7 ± 22.1 vs. 82.3 ± 19.0, P = 0.01). The vision-specific QOL was significantly correlated with ICOGCG score (β =  - 1.88, 95%CI: - 3.35 to - 0.41, P = 0.01) and post-alloHCT medical expense (β =  - 5.70, 95%CI: - 10.35 to - 1.05, P = 0.02), while cancer-specific QOL was strikingly correlated with post-alloHCT medical expense (β =  - 9.91, 95%CI: - 14.43 to - 5.39, P < 0.001), frequency of ophthalmic medication (β =  - 0.93, 95%CI: - 1.64 to - 0.21, P = 0.01), education (β =  - 6.97, 95%CI: - 13.31 to - 0.62, P = 0.03), and peripheral blood stem cell use (β =  - 6.42, 95%CI: - 12.59 to - 0.25, P = 0.04).

CONCLUSIONS

Patients with oGVHD experienced significant impairment in both vision-specific and cancer-specific QOL including cognitive function when compared with those without after alloHCT. Multidimensional QOL assessment should be included in the long-term alloHCT survivorship care.

How I treat high-risk acute myeloid leukemia using preemptive adoptive cellular immunotherapy

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a potentially curative treatment for patients with high-risk acute leukemias, but unfortunately disease recurrence remains the major cause of death in these patients. Infusion of donor lymphocytes (DLI) has the potential to restore graft-versus-leukemia immunologic surveillance; however, efficacy varies across different hematologic entities. Although relapsed chronic myeloid leukemia, transplanted in chronic phase, has proven remarkably susceptible to DLI, response rates are more modest for relapsed acute myeloid leukemia and acute lymphoblastic leukemia. To prevent impending relapse, a number of groups have explored administering DLI preemptively on detection of measurable residual disease (MRD) or mixed chimerism. Evidence for the effectiveness of this strategy, although encouraging, comes from only a few, mostly single-center retrospective, nonrandomized studies. This article seeks to (1) discuss the available evidence supporting this approach while highlighting some of the inherent challenges of MRD-triggered treatment decisions post-transplant, (2) portray other forms of postremission cellular therapies, including the role of next-generation target-specific immunotherapies, and (3) provide a practical framework to support clinicians in their decision-making process when considering preemptive cellular therapy for this difficult-to-treat patient population.

Immunotherapy approaches for hematological cancers

Hematological cancers such as leukemia, lymphoma, and multiple myeloma have traditionally been treated with chemo and radiotherapy approaches. Introduction of immunotherapies for treatment of these diseases has led to patient remissions that would not have been possible with traditional approaches. In this critical review we identify main disease characteristics, symptoms, and current treatment options. Five common immunotherapies, namely checkpoint inhibitors, vaccines, cell-based therapies, antibodies, and oncolytic viruses, are described, and their applications in hematological cancers are critically discussed.

100 plus years of stem cell research-20 years of ISSCR

The International Society for Stem Cell Research (ISSCR) celebrates its 20^th anniversary in 2022. This review looks back at some of the key developments in stem cell research as well as the evolution of the ISSCR as part of that field. Important discoveries from stem cell research are described, and how the improved understanding of basic stem cell biology translates into new clinical therapies and insights into disease mechanisms is discussed. Finally, the birth and growth of ISSCR into a leading stem cell society and a respected voice for ethics, advocacy, education and policy in stem cell research are described.

Analysis of Subset Chimerism for MRD-Detection and Pre-Emptive Treatment in AML

Allogeneic hematopoietic stem cell transplantation (alloHCT) represents the only potentially curative treatment in high-risk AML patients, but up to 40% of patients suffer from relapse after alloHCT. Treatment of overt relapse poses a major therapeutic challenge and long-term disease control is achieved only in a minority of patients. In order to avoid post-allograft relapse, maintenance as well as pre-emptive therapy strategies based on MRD-detection have been used. A prerequisite for the implementation of pre-emptive therapy is the accurate identification of patients at risk for imminent relapse. Detection of measurable residual disease (MRD) represents an effective tool for early relapse prediction in the post-transplant setting. However, using established MRD methods such as multicolor flow cytometry or quantitative PCR, sensitive MRD monitoring is only applicable in about half of the patients with AML and advanced MDS undergoing alloHCT. Donor chimerism analysis, in particular when performed on enriched leukemic stem and progenitor cells, e.g. CD34+ cells, is a sensitive method and has emerged as an alternative option in the post alloHCT setting. In this review, we will focus on the current strategies for lineage specific chimerism analysis, results of pre-emptive treatment using this technology as well as future developments in this field.

Natural Barcodes for Longitudinal Single Cell Tracking of Leukemic and Immune Cell Dynamics

Blood malignancies provide unique opportunities for longitudinal tracking of disease evolution following therapeutic bottlenecks and for the monitoring of changes in anti-tumor immunity. The expanding development of multi-modal single-cell sequencing technologies affords newer platforms to elucidate the mechanisms underlying these processes at unprecedented resolution. Furthermore, the identification of molecular events that can serve as in-vivo barcodes now facilitate the tracking of the trajectories of malignant and of immune cell populations over time within primary human samples, as these permit unambiguous identification of the clonal lineage of cell populations within heterogeneous phenotypes. Here, we provide an overview of the potential for chromosomal copy number changes, somatic nuclear and mitochondrial DNA mutations, single nucleotide polymorphisms, and T and B cell receptor sequences to serve as personal natural barcodes and review technical implementations in single-cell analysis workflows. Applications of these methodologies include the study of acquired therapeutic resistance and the dissection of donor- and host cellular interactions in the context of allogeneic hematopoietic stem cell transplantation.

Immunology 101: fundamental immunology for the practicing hematologist

From an evolutionary perspective, the immune system developed primarily to protect the host from pathogens. In the continuous balance between killing pathogens and protecting host tissues, selective pressures have shaped the discriminatory functions of the immune system. In addition to protection against microbial pathogens, the immune system also plays a critical role in antitumor immunity. Immune dysfunction, either under- or overactivity, is found in a wide range of hematologic disorders. Here we review the fundamental features of the immune system and the key concepts critical to understanding the impact of immune dysfunction on hematologic disorders.