Donor matters: Donor selection impact on hematopoietic stem cell transplantation outcomes in Hispanic patients with B-cell acute lymphocytic leukemia: Insights from a myeloablative HSCT study

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is a pivotal treatment for high-risk acute lymphocytic leukemia (ALL), although limited by suitable human leukocyte antigen (HLA)-matched sibling donors (MSD). This study evaluates the impact of donor selection on outcomes in post-HSCT Hispanic B-cell ALL patients.

METHODOLOGY

This single-center retrospective study evaluates outcomes in 88 adult Hispanic B-cell ALL patients who underwent haploidentical, MSD, or MUD myeloablative HSCT between 2013 and 2023.

RESULTS

Compared to Haploidentical transplants, MSD exhibited worse cumulative incidence of relapse (CIR) (HR = 3.39; P = 0.014) and disease-free survival (DFS) (HR = 2.44; P = 0.048) whereas MUD outcomes did not differ. This effect persisted even when controlling for pre-HSCT stage and Minimal residual disease (MRD) status. In addition, Ph-like was a significant predictor of worse DFS (HR = 3.60; P=0.014) and CIR (HR = 2.97; P=0.035) on multivariate analysis. Older donor age correlated with worse GVHD-free, relapse-free survival (GRFS) in haploidentical transplants (HR = 1.05; P=0.036).

CONCLUSION

Our data highlights improved outcomes with younger, haploidentical donors among Hispanic B-cell ALL patients undergoing myeloablative HSCT. This underscores the importance of donor selection in optimizing outcomes for ALL patients.

Concordance of Next-Generation Sequencing and Multiparametric Flow Cytometry Methods for Detecting Measurable Residual Disease in Adult Acute Lymphoblastic Leukemia: Optimizing Prediction of Clinical Outcomes From a Single-Center Study

INTRODUCTION

Detection of measurable residual disease (MRD) in adults with acute lymphoblastic leukemia (ALL) is a vital biomarker in risk prediction and treatment selection. Next-generation sequencing (NGS) offers greater sensitivity relative to multiparametric flow cytometry (MFC) and may be a better predictive tool for identifying ALL patients at risk of relapse.

PATIENTS AND METHODS

This single-center retrospective study compares MRD detection by NGS versus MFC in 52 adult B- and T-ALL patients treated at our institution between 2018 and 2023. Pretreatment bone marrow samples were used for assay calibration, while post-treatment MRD assessment was completed up to 4.5 months after the first complete remission (CR1) using an MRD cutoff of 10-6 for distinguishing relapse risk.

RESULTS

The 2-year cumulative incidence of relapse (CIR) among patients who were MRD positive using MFC and NGS was 39.5% and 46.2%, respectively. Unlike MFC, post-CR1 MRD positivity with NGS significantly predicted CIR (HR = 9.47, P = .028). In patients who were MRD negative by MFC, low levels of MRD detected by NGS distinguished patients at high risk of relapse (HR 10.3, P = .026, 2-year CIR 51.6%).

CONCLUSION

Our data suggests that assessment of post-CR1 MRD using a highly sensitive NGS assay can identify ALL patients undergoing frontline therapy at increased risk of relapse and guide the use of adjuvant therapy.

Case report: Pulse cyclophosphamide for treatment of multi-agent-refractory hepatic graft-versus-host disease

Graft-versus-host disease (GVHD) is a common complication in patients receiving allogeneic hematopoietic stem cell transplantation (HSCT). GVHD is characterized as either acute or chronic based on symptomatology and histopathological findings. Despite advancements in disease-targeting therapeutics, steroid-refractory GVHD remains a significant contributor to mortality in HSCT recipients, highlighting the gaps in our understanding of its pathophysiology and treatment strategies. We present the case of a 46-year-old woman diagnosed with acute undifferentiated leukemia, who exhibited persistently elevated levels of serum total bilirubin (T.Bili), alkaline phosphatase (ALP), and liver function tests (LFTs) beginning on [day +201] post-haploidentical peripheral blood stem cell (PBSC) transplantation. The patient received fludarabine/total body irradiation (Flu/TBI) as a myeloablative conditioning regimen and post-transplant cyclophosphamide/tacrolimus/mycophenolate mofetil (PTCy/Tac/MMF) as GVHD prophylaxis. A liver biopsy confirmed the diagnosis of GVHD, while other possible etiologies were excluded by corresponding tests. Initial treatment with prednisone and tacrolimus, and the later addition of ruxolitinib, all showed poor response indicated by worsening T.Bili, ALP, and LFTs at the same time. Based on a multidisciplinary comprehensive assessment, we decided to administer 1,000 mg/m2 (1,600 mg) of cyclophosphamide ("pulse Cy"), which resulted in a dramatic improvement in T.Bili and transaminases starting from the very next day. A durable response to pulse cyclophosphamide was observed, as all indicators normalized ("complete response") within 55 days without relapses. The patient remains in good health with no recurrence of hepatic GVHD. To our knowledge, this is the first case in which Grade IV hepatic GVHD, refractory to multiple agents including steroids, tacrolimus, and ruxolitinib, demonstrated a complete response to pulse cyclophosphamide. The success highlights the potential therapeutic role of cyclophosphamide, a potent and cost-effective chemotherapy agent, in treating multi-agent-refractory GVHD. Large-scale clinical trials are warranted to validate its efficacy in this setting.

Unique challenges to diagnosing sweet syndrome following induction chemotherapy for relapsed Acute Myeloid Leukemia (AML): A case and brief-review

Background

Sweet Syndrome (SS) is a rare inflammatory skin condition characterized by the sudden appearance of tender, erythematous or violaceous papules, plaques, and nodules typically found on the face, neck, shoulder, upper extremities, and trunk. Often, SS is difficult to diagnose because of its various non-specific manifestations, including fever, arthralgia, myalgia and ocular involvement. In most cases described in literature, cutaneous and pulmonary symptoms of SS present in a concomitant manner. Several reported cases of pulmonary SS have shown that if left untreated, acute respiratory distress syndrome can ensue and progress to fatal respiratory failure.

Case report

A 58-year-old female with acute myeloid leukemia (AML) secondary to chronic lymphocytic leukemia (CLL) presented with new nodular lesions, dyspnea, and fevers. Chest X-ray revealed pulmonary infiltrates. The patient developed new facial lesions and worsening hypoxic respiratory failure. Further infectious workup was negative. She was found to have SS with pulmonary involvement and initiated on high-dose intravenous (IV) steroids with marked clinical improvement.

Conclusions

Major and minor criteria for the diagnosis of lung-associated SS should be carefully evaluated, especially when a biopsy is unavailable. The following case report describes the clinical course and outcomes from treatment for this patient.

Real world experience: Examining outcomes using letermovir for CMV prophylaxis in high-risk allogeneic hematopoietic stem cell patients in the setting of using T-cell depletion as GVHD prophylaxis

BACKGROUND

Cytomegalovirus (CMV) infection significantly impacts the morbidity and mortality of patients undergoing allogeneic hematopoietic stem cell transplant (HSCT). Despite monitoring and pharmacologic prophylaxis with drugs such as valganciclovir or ganciclovir, rates of early CMV reactivation have continually persisted, contributing to increased rates of morbidity and mortality in allogeneic-HSCT patients. This study evaluates the outcomes of letermovir in preventing CMV reactivation and CMV-related complications in HSCT recipients with initiation of therapy at +21 days in high-risk patients.

METHODS

We retrospectively analyzed adult patients at University of Southern California (USC) Norris Cancer Hospital who received allogeneic-HSCT from 2018 to 2020 with subsequent serial CMV monitoring and treatment. CMV reactivation was determined in patients if they had clinically significant serum CMV viremia (viremia requiring treatment) or organ involvement by day+100. Primary endpoint assessed was day+100 rates of CMV reactivation. Secondary end-points included 1-year OS, 1-year RFS, and incidence of GVHD. Descriptive statistics were used to compare characteristics between groups used in this study, with a significance level of α = 0.05.

RESULTS

Between 2018 and 2020, 116 adult HSCT recipients were reviewed. 51% were male and 49% were female; donor sources consisted of 27% match related donor (MRD) 28% match-unrelated donor (MUD), and 45% haploidentical donor. Of the 116 patients, 92 were identified as high-risk for CMV reactivation. 71 patients received letermovir prophylaxis, and 21 patients received no prophylaxis. In high-risk patients, after adjusting for GVHD status and transplant type, patients that received letermovir had no statistically significant difference of having D + 100 CMV reactivation compared to patients that did not receive letermovir. 1.02 (95% CI: 0.35, 3.20) (p = 0.97). Moreover, there were no statistically significant difference observed between letermovir treatment and 1-year OS, 1-year RFS, and incidence of GVHD.

CONCLUSION

Patients in the high-risk letermovir group had outcomes that were comparable to the lower risk "non-letermovir" group. There was no significant difference in CMV D + 100 reactivation between high-risk patients who did not receive letermovir compared to the patients who did. While other studies have shown that early initiation of letermovir may be associated with improved outcomes, our study shows that the use of letermovir with initiation at 21 days may not necessarily translate to improved secondary outcomes such as overall survival. Further prospective studies evaluating the time of initiating therapy and outcomes are needed.

MPN-215 Outcomes of Myelofibrosis Patients Post Allogeneic-HSCT at the University of Southern California, a Retrospective Study

CONTEXT

In myelofibrosis (MF) patients, the standard of care curative (SOC) option is through an allogeneic-hematopoietic stem cell transplantation (allo-HSCT); however, no SOC pre- and post-transplant management exists.

OBJECTIVE

To report outcomes of MF patients, post-allo-HSCT at our institution with consideration of patient characteristics, risks, and pre-transplant treatment.

DESIGN

A retrospective chart review.

SETTING

Single institution: academic center hospital/county hospital Patients or Other Participants: 18-99YO M/F patients with MF diagnosis by bone-marrow biopsy since 2012-2020 and received allo-HSCT at our institution.

INTERVENTIONS

Chart review.

MAIN OUTCOME MEASURES

Primary: OS, PFS since time of transplant, stratified to JAK2 inhibitor use, MF type and associated patient characteristics/risks. Secondary: Patient/treatment characteristics, response/mortality rates. P≤ 0.05 is considered significant.

RESULTS

In 18 patients, median age 60.7 years 61.1% White/Non-Hispanic, 16.7% Hispanic with 44.4% high, 55.6% intermediate-1/2 risk by DIPSS, 27.8% high and 33.3% very high risk by MIPSS70+. 66.7% had primary MF. At time of transplant, 11.1% was CR/PR, 38.9% SD, and 50% PD. 38.9% received MSD, 27.8% MUD, and 33.3% received haploidentical stem cells. 76.5% had RIC and 23.5% underwent MAC. 44.4% were +JAK2 V617F, 16.7% had either: ASXL1, EZH2, SRSF2, IDHL1/2, U2AF1. 11.1% had high-risk karyotype/cytogenetics. 61.1% received a JAK2 inhibitor, 72% received non-JAK2 inhibitor treatments pre-transplant. Post-transplant, 78% alive at 1 year. Since transplant, 3-year (3y) OS was 66.7% in primary MF patients, 55.6% in secondary (p=0.75) with similar EFS. 3y-OS in JAK2 V617F+ patients was 83.3% (p=0.13) with similar EFS. 3y-OS of those who received a JAK2 inhibitor pre-transplant was 47.7% (p=0.17) with similar EFS (p=0.16). Those without either ASXL1, EZH2, SRSF2, IDHL1/2, or U2AF1 mutations achieved a higher, 72.2%, 3y-OS (p=0.076) than those with any. High-risk karyotype/cytogenetics 3y-OS was 50% (p=0.43). OS/EFS rates were generally lower with higher DIPSS and MIPSS70+.

CONCLUSIONS

Given most of our patients were high/very high risks, achieving 3y-OS of 66.7% in primary and 55.6% in secondary MF since the time of transplant is appreciable. Interestingly, even with higher OS/EFS for JAK2V+ patients, the OS/EFS is lower for those who received a JAK2 inhibitor. This could be from the low sample size. Further studies are necessary.

Abstract A066: Histone deacetylase 11 is an epigenetic regulator of T-cell pro-inflammatory function and novel target for enhancing T-cell anti-tumor activity

The efficacy of immunotherapy is dependent on the ability of antigen-specific T-cells to mount a proper anti-tumor response while avoiding a plethora of immunosuppressive mechanisms. Unfortunately, these immunosuppressive mechanisms often overwhelm the T-cell response, resulting in patients failing to respond. Histone deacetylases (HDACs) are a family of epigenetic modifiers named for their ability to remove acetyl groups from lysine residues of histone tails, thereby regulating the chromatin structure and gene expression. Here we report that HDAC11, the most recently discovered HDAC, is a regulator of T-cell pro-inflammatory function. Previous reports have shown HDAC11 expression to be tissue restricted. Consequently, we compared expression levels of HDAC11 using an eGFP reporter mouse, in various immune cells. It was found that T-cells expressed relatively high levels of HDAC11. However, while resting T-cells, both central memory and naïve, had high levels of HDAC11 expression, effector or effector memory T-cells displayed lower levels. Additionally, T-cells experienced rapid down-regulation of HDAC11 upon activation. To expand upon these observations, the function of T-cells from HDAC11KO mice were investigated. Initial experiments revealed no gross changes in the numbers or maturation of T-cells. However, HDAC11KO mice displayed an increased percentage of central memory CD8+ T-cells (p<0.05). Additionally, upon activation these T-cells were more apt to acquire effector status (p<0.001). Upon activation, HDAC11KO T-cells demonstrated a robust increase in IL-2, TNF and IFNγ production (p<0.01), but showed no differences in Th2 or Th17 cytokine production. These T-cells also expressed higher levels of the effector molecules granzyme B and perforin (p<0.01). Moreover, post-activation, CD8+ T-cells lacking HDAC11 also displayed a higher percentage of proliferating cells, and more divisions of proliferating cells (p<0.01). HDAC11KO T-cells displayed higher resistance to proliferative suppression by Tregs and failed to succumb to anergy in a high dose antigen model. Indeed, while OTII T-cells from mice injected with high dose OVA peptide displayed reduced levels of IFNγ production compared to cells from non-injected mice after rechallenge, HDAC11KO/OTII T-cells had an increase in IFNγ production. Mechanistically, T-cells devoid of HDAC11 did not appear to have differences in TCR signaling, but did express higher levels of the transcription factors EOMES and T-bet. Chromatin immunoprecipitation (ChIP) revealed higher basal levels of acetylation of these genes in HDAC11KO mice. ChIP analysis also revealed interactions of HDAC11 at the promoters of both EOMES and T-bet. In a graft vs. host disease (GvHD) model, HDAC11KO T-cells produced a more rapid onset of GvHD, and were able to do so with transfers of cell numbers below that able to induce GvHD using WT T-cells (p<0.01). This GvHD was characterized by greater levels of IFNγ and TNF as well as increased T-cell expansion (p<0.05). In a B16 melanoma model, adoptive transfer of HDAC11KO T-cells resulted in delayed tumor progression (p<0.05) compared to WT T-cells. To begin investigating the clinical potential of these data, the expression levels of HDAC11 were investigated in melanoma tumor sections utilized to grow tumor infiltrating lymphocytes (TIL) for clinical trials of adoptive cell therapy. A reduced level of HDAC11 was found in tumor sections from those patients responding to TIL therapy compared to progressing patients (p<0.01). Collectively, beyond demonstrating HDAC11 as a novel epigenetic regulator of T-cell pro-inflammatory function, these results highlight HDAC11 as a novel target for enhancing the efficacy of immunotherapy.

Citation Format: David M. Woods, Andressa L. Sodre, Karrune Woan, Alejandro Villagra, Amod Sarnaik, Jeffrey Weber, Eduardo M. Sotomayor. Histone deacetylase 11 is an epigenetic regulator of T-cell pro-inflammatory function and novel target for enhancing T-cell anti-tumor activity. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A066.

Abstract 4086: Histone deacetylase 6 (HDAC6) as a new target modulating the proliferation and immune-related pathways in melanoma

Histone deacetylases (HDACs), originally described as histone modifiers, have more recently been demonstrated to modify a variety of other proteins involved in diverse cellular processes unrelated to the chromatin environment. This includes the deacetylation of multiple non-histone targets, such as proteins involved in cell cycle/apoptosis and immune regulation. Specifically, HDACs have garnered significant interest due to the availability of drugs that selectively inhibits HDACs. We recently identified that the pharmacological or genetic abrogation of a single HDAC, HDAC6, modifies the immunogenicity and proliferation of melanoma in both in vitro and in vivo models.

Using specific HDAC6 inhibitors (HDAC6i) we observed decreased proliferation and G1 cell cycle arrest in all melanoma cell lines measured by MTS assay and flow cytometry. These results were also observed in stable HDAC6 knockdown melanoma cell lines (HDAC6KD) generated by specific lentiviral shRNA for HDAC6. In addition to the effects observed in proliferation and apoptosis after inhibiting HDAC6, we found important changes in the expression of immune-related pathways, including increased expression of MHC, co-stimulatory molecules, and specific melanoma tumor associated antigens such as gp100, MART-1, Tyrp1 and Tyrp2.

Our in vitro results were further supported by in vivo tumor growth studies. We observed a delayed tumor growth of inoculated B16 melanoma cells in C57BL/6 mice treated with selective HDAC6i. A similar outcome was identified after inoculation of HDAC6KD B16 melanoma cells in C57BL/6 mice. Such an effect was reverted partially in CD4+ and CD8+ depleted C57BL/6 mice challenged with HDAC6KD cells, suggesting that the disruption of HDAC6 enhances immune system recognition of melanoma cells. This delay in tumor growth could be a reflection of their diminished proliferation and an increase in their immunogenicity leading to improved immune recognition and clearance. These studies provide critical insights into the molecular pathways that are involved in the regulatory role of HDAC6 in cell proliferation, survival, and cytokine signaling of human melanoma cells. Collectively, our data has identified HDAC6 as an attractive therapeutic target in melanoma.

Citation Format: Patricio Perez-Villarroel, Maritza Lienlaf, Calvin Lee, Fengdong Cheng, David Woods, Kelly Barrios, Karrune Woan, Jorge Canales, Tessa Knox, Danay Marante, Hongwei Wang, Pedro Horna, Keiran Smalley, Esteban Celis, Ed Seto, Jeffrey S. Weber, Eduardo M. Sotomayor, Alejandro Villagra. Histone deacetylase 6 (HDAC6) as a new target modulating the proliferation and immune-related pathways in melanoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4086. doi:10.1158/1538-7445.AM2014-4086

A novel role for histone deacetylase 6 in the regulation of the tolerogenic STAT3/IL-10 pathway in APCs

APCs are critical in T cell activation and in the induction of T cell tolerance. Epigenetic modifications of specific genes in the APC play a key role in this process, and among them histone deacetylases (HDACs) have emerged as key participants. HDAC6, one of the members of this family of enzymes, has been shown to be involved in regulation of inflammatory and immune responses. In this study, to our knowledge we show for the first time that genetic or pharmacologic disruption of HDAC6 in macrophages and dendritic cells results in diminished production of the immunosuppressive cytokine IL-10 and induction of inflammatory APCs that effectively activate Ag-specific naive T cells and restore the responsiveness of anergic CD4(+) T cells. Mechanistically, we have found that HDAC6 forms a previously unknown molecular complex with STAT3, association that was detected in both the cytoplasmic and nuclear compartments of the APC. By using HDAC6 recombinant mutants we identified the domain comprising amino acids 503-840 as being required for HDAC6 interaction with STAT3. Furthermore, by re-chromatin immunoprecipitation we confirmed that HDAC6 and STAT3 are both recruited to the same DNA sequence within the Il10 gene promoter. Of note, disruption of this complex by knocking down HDAC6 resulted in decreased STAT3 phosphorylation--but no changes in STAT3 acetylation--as well as diminished recruitment of STAT3 to the Il10 gene promoter region. The additional demonstration that a selective HDAC6 inhibitor disrupts this STAT3/IL-10 tolerogenic axis points to HDAC6 as a novel molecular target in APCs to overcome immune tolerance and tips the balance toward T cell immunity.

Divergent roles of histone deacetylase 6 (HDAC6) and histone deacetylase 11 (HDAC11) on the transcriptional regulation of IL10 in antigen presenting cells

The anti-inflammatory cytokine IL-10 is a key modulator of immune responses. A better understanding of the regulation of this cytokine offers the possibility of tipping the balance of the immune response toward either tolerance, or enhanced immune responses. Histone deacetylases (HDACs) have been widely described as negative regulators of transcriptional regulation, and in this context, the primarily nuclear protein HDAC11 was shown to repress il-10 gene transcriptional activity in antigen-presenting cells (APCs). Here we report that another HDAC, HDAC6, primarily a cytoplasmic protein, associates with HDAC11 and modulates the expression of IL-10 as a transcriptional activator. To our knowledge, this is the first demonstration of two different HDACs being recruited to the same gene promoter to dictate divergent transcriptional responses. This dynamic interaction results in dynamic changes in the expression of IL-10 and might help to explain the intrinsic plasticity of the APC to determine T-cell activation versus T-cell tolerance.

The antimelanoma activity of the histone deacetylase inhibitor panobinostat (LBH589) is mediated by direct tumor cytotoxicity and increased tumor immunogenicity

Melanoma is the deadliest skin cancer, and its incidence has been increasing faster than any other cancer. Although immunogenic, melanoma is not effectively cleared by host immunity. In this study, we investigate the therapeutic, antimelanoma potential of the histone deacetylase inhibitor (HDACi) panobinostat (LBH589) by assessing both its cytotoxic effects on melanoma cells as well as enhancement of immune recognition of melanoma. Utilizing murine and human melanoma cell lines, we analyzed the effects of LBH589 on proliferation and survival. In addition, we analyzed the expression of several immunologically relevant surface markers and melanoma differentiation antigens, and the ability of LBH589-treated melanoma to activate antigen-specific T cells. Finally, we assessed the in-vivo effects of LBH589 in a mouse melanoma model. Low nanomolar concentrations of LBH589 inhibit the growth of all melanoma cell lines tested, but not normal melanocytes. This inhibition is characterized by increased apoptosis as well as a G1 cell cycle arrest. In addition, LBH589 augments the expression of major histocompatibility complex and costimulatory molecules on melanoma cells leading to an increased ability to activate antigen-specific T cells. Treatment also increases expression of melanoma differentiation antigens. In vivo, LBH589 treatment of melanoma-bearing mice results in a significant increase in survival. However, in immunodeficient mice, the therapeutic effect of LBH589 is lost. Taken together, LBH589 exerts a dual effect upon melanoma cells by affecting not only growth/survival but also by increasing melanoma immunogenicity. These effects provide the framework for future evaluation of this HDAC inhibitor in melanoma treatment.

Histone deacetylase 11 is an epigenetic regulator of cytotoxic T-lymphocyte effector function and memory formation (P1404)

The roles of individual histone deacetylases in the regulation of T-cell development and function remain largely unknown. Here we provide evidence for HDAC11 as an epigenetic regulator of T-cell inflammatory response as well as CTL central memory formation. To investigate the role of HDAC11 in T-cells, an HDAC11 knockout (HDAC11KO) mouse model was utilized. HDAC11KO mice display no gross phenotypic abnormalities and no alterations in T-cell development or CD4+/CD8+ population distributions. However, HDAC11KO CTLs are hyper-proliferative and secrete significantly higher levels of IL-2, TNF, and IFN-γ upon activation, and HDAC11KO mice accumulate higher percentages of central memory CTLs. In an allogeneic bone marrow transfer model, HDAC11KO T-cells mediate more potent and robust graft vs host disease associated with increased inflammatory cytokines. Mechanistically, we provide evidence that in CTLs HDAC11 interacts with the Eomes gene promoter, a known regulator of IFN-γ production and memory formation. HDAC11KO CTLs, at both basal state and post stimulation, display higher levels of acetylation at the Eomes promoter, indicative of a permissive transcriptional state. Correspondingly, eomes mRNA levels in HDAC11KO cells are elevated. Finally, chromatin immunoprecipitation of HDAC11 reveals interaction between HDAC11 and the Eomes promoter in CTLs. These results support HDAC11 as an epigenetic regulator of CTL function and memory formation through epigenetic regulation of Eomes.

Critical role of histone deacetylase 11 in lineage differentiation of immune cells (P4378)

Previously our group reported HDAC11 as a regulator of IL-10 expression in immune cells; however the functions of HDAC11 still remain largely unknown. Here we reveal the novel role of HDAC11 as an epigenetic regulator of lineage differentiation in leukocytes. To “visualize” dynamic changes in HDAC11 transcriptional activation, we utilized HDAC11 promoter-driven eGFP reporter mice, where eGFP expression is indicative of HDAC11 transcription. Using this system, we found that hematopoietic stem cells are devoid of eGFP expression. However, eGFP expression increases from CD4-/CD8- T-cells to single positive CD4+ and CD8+, and decreases in effector compared to naïve T-cells. In the bone marrow, expression of eGFP moderately increases in the transition from Pro- to Pre-B-cells, however in the periphery eGFP significantly increases in the B-1 stage of differentiation. Remarkably, in plasma cells eGFP expression appears to be at its highest. Moreover, less plasma cells and more B-1 cells were observed when HDAC11KO were compared to wild-type mice. Expression of eGFP in myeloblasts appears to be absent, however it increases to 50% in the promyelocytes and to 98% in the granulocytes. Strikingly, monocytes showed no eGFP expression. These results unveiled a previously unknown role of HDAC11 in hematopoiesis, regulating leukocyte lineage differentiation and expansion. These key findings will potentially lead to targeted epigenetic therapies to influence immune cell differentiation.

Selective histone deacetylase 6 inhibitors bearing substituted urea linkers inhibit melanoma cell growth

The incidence of malignant melanoma has dramatically increased in recent years thus requiring the need for improved therapeutic strategies. In our efforts to design selective histone deactylase inhibitors (HDACI), we discovered that the aryl urea 1 is a modestly potent yet nonselective inhibitor. Structure-activity relationship studies revealed that adding substituents to the nitrogen atom of the urea so as to generate compounds bearing a branched linker group results in increased potency and selectivity for HDAC6. Compound 5 g shows low nanomolar inhibitory potency against HDAC6 and a selectivity of ∼600-fold relative to the inhibition of HDAC1. These HDACIs were evaluated for their ability to inhibit the growth of B16 melanoma cells with the most potent and selective HDAC6I being found to decrease tumor cell growth. To the best of our knowledge, this work constitutes the first report of HDAC6-selective inhibitors that possess antiproliferative effects against melanoma cells.

Histone deacetylase inhibitor LAQ824 augments inflammatory responses in macrophages through transcriptional regulation of IL-10

APCs are important in the initiation of productive Ag-specific T cell responses and the induction of T cell anergy. The inflammatory status of the APC at the time of encounter with Ag-specific T cells plays a central role in determining such divergent T cell outcomes. A better understanding of the regulation of proinflammatory and anti-inflammatory genes in its natural setting, the chromatin substrate, might provide novel insights to overcome anergic mechanisms mediated by APCs. In this study, we show for the first time, to our knowledge, that treatment of BALB/c murine macrophages with the histone deacetylase inhibitor LAQ824 induces chromatin changes at the level of the IL-10 gene promoter that lead to enhanced recruitment of the transcriptional repressors HDAC11 and PU.1. Such an effect is associated with diminished IL-10 production and induction of inflammatory cells able of priming naive Ag-specific T cells, but more importantly, capable of restoring the responsiveness of anergized Ag-specific CD4(+) T cells.

A novel chemoimmunomodulating property of docetaxel: suppression of myeloid-derived suppressor cells in tumor bearers

PURPOSE

Myeloid-derived suppressor cells (MDSC) accumulate in tumor-bearing hosts and are associated with immune suppression. To date, there have only been few studies that evaluate the direct effect of chemotherapeutic agents on MDSCs. Agents that inhibit MDSCs may be useful in the treatment of patients with various cancers.

EXPERIMENTAL DESIGN

We investigated the in vivo effects of docetaxel on immune function in 4T1-Neu mammary tumor-bearing mice to examine if a favorable immunomodulatory effect accompanies tumor suppression. Primary focus was on the differentiation status of MDSCs and their ability to modulate T-cell responses.

RESULTS

Docetaxel administration significantly inhibited tumor growth in 4T1-Neu tumor-bearing mice and considerably decreased MDSC proportion in the spleen. The treatment also selectively increased CTL responses. Docetaxel-pretreated MDSCs cocultured with OT-II splenocytes in the presence of OVA(323-339) showed OT-II-specific CD4 activation and expansion in vitro. In characterizing the phenotype of MDSCs for M1 (CCR7) and M2 [mannose receptor (CD206)] markers, MDSCs from untreated tumor bearers were primarily MR(+) with few CCR7(+) cells. Docetaxel treatment polarized MDSCs toward an M1-like phenotype, resulting in 40% of MDSCs expressing CCR7 in vivo and in vitro, and macrophage differentiation markers such as MHC class II, CD11c, and CD86 were upregulated. Interestingly, docetaxel induced cell death selectively in MR(+) MDSCs while sparing the M1-like phenotype. Finally, inhibition of signal transducer and activator of transcription 3 may in part be responsible for the observed results.

CONCLUSIONS

These findings suggest potential clinical benefit for the addition of docetaxel to current immunotherapeutic protocols.

Potential therapeutic role of natural killer cells in cancer

Cancer immunotherapy is a growing field that aims at restoring and enhancing immune function to combat oncogenic conditions. One target of this field is natural killer (NK) cells. Part of innate immunity, NK cells are able to kill tumor cells without previous priming. Results from stem cell transplants containing alloreactive donor NK cells and in vitro work have evidenced a great antitumor potential. In addition, NK cells are likely to interact with dendritic cells, potent antigen-presenting cells, thus forming a bridge between innate and adaptive immunity. This review aims to provide an overview of NK cells with particular emphasis on properties that can and are being targeted in order to potentiate the antitumor activity of these cells.