Lymphopenia at diagnosis predicts survival of patients with immunodeficiency-associated lymphoproliferative disorders

The number of patients who are administered immunosuppressive agents has been increasing. Accordingly, more patients face higher risks for developing immunodeficiency-associated lymphoproliferative disorders (LPD). Although immunodeficiency-associated LPD are distinct from other lymphoid neoplasms in terms of their immunocompromised backgrounds, little is known about the impact of lymphopenia at diagnosis on survival in patients with these LPD. Seventy-one immunodeficiency-associated LPD in Kyoto University Hospital (post-transplant LPD (PTLD), n = 26; other iatrogenic immunodeficiency-associated LPD, n = 45) were reviewed and analyzed. The median age at diagnosis was 63 years (range, 3–83). Diffuse large B cell lymphoma was the most common subtype (n = 33), followed by Hodgkin lymphoma (n = 12), B cell monomorphic LPD not specified (n = 11), and polymorphic LPD or early-phase diseases (n = 15). The median follow-up period for survivors was 2.5 years and overall survival (OS) and progression-free survival (PFS) at 2.5 years were 75% and 67%, respectively. Multivariate analysis showed that lymphopenia (≤ 800/μL) at diagnosis predicted inferior OS (HR, 3.72; P = 0.043) and PFS (HR, 3.82; P = 0.012). Serum albumin values also strongly affected OS (> 3.18 g/dL vs. ≤ 3.18 g/dL; HR, 0.21; P = 0.010) and PFS (HR, 0.26; P = 0.013). Lymphopenia at diagnosis is suggested to predict inferior OS and PFS in patients with immunodeficiency-associated LPDs. Immunocompromised status might affect disease progression in these distinct lymphoid neoplasms growing under immunocompromised backgrounds

Programmed cell death 1‐expressing CD56‐negative natural killer (NK) cell expansion is a hallmark of chronic NK cell activation during dasatinib treatment

Dasatinib treatment markedly increases the number of large granular lymphocytes including natural killer (NK) cells in a proportion of Ph+ leukemia patients, which associates with a better prognosis. In-depth immune profiling of NK cells can predict therapeutic response in these patients. In the present study, we showed that CD56-negative (CD56neg) NK cells increased exclusively in cytomegalovirus-seropositive (CMV+) patients treated with dasatinib. The increase longitudinally paralleled with progressive differentiation of CD56dim NK cells during dasatinib therapy driven by CMV reactivation as shown by principal component analysis on 19 NK cell markers. The CD56neg NK cells showed downregulation of NK-activating receptors, upregulation of PD-1, and lower cytotoxicity and cytokine production, indicating that these cells are anergic and dysfunctional as seen in chronic infections with HIV-1 or hepatitis C virus. Moreover, cytolytic activity of CD56dim and CD56neg NK cells against leukemia cells was partially restored by nivolumab in proportion to the frequency of PD-1+ NK cells. The proportion of patients who achieved deep molecular responses at 2 years was significantly higher in dasatinib-treated patients with ≥3% CD56neg NK cells than in those with fewer CD56neg NK cells (54.5% vs 15.8%, P = .0419). These findings suggest that CD56neg NK cells may be an exhausted population induced by chronic activation through CMV reactivation during dasatinib therapy. Expansion of CD56neg NK cells is a hallmark of chronic NK cell activation in patients treated with dasatinib and may predict a better clinical outcome. Furthermore, PD-1 blockade may enhance anti-leukemia responses of such NK cells

Paradoxical activation of c-Src as a drug-resistant mechanism

抗がん剤抵抗性の新規メカニズムの解明 --薬剤抵抗性がん細胞は抗がん剤により増殖する--. 京都大学プレスリリース. 2021-03-25.ATP-competitive inhibitors have been developed as promising anti-cancer agents. However, drug-resistance frequently occurs, and the underlying mechanisms are not fully understood. Here, we show that the activation of c-Src and its downstream phosphorylation cascade can be paradoxically induced by Src-targeted and RTK-targeted kinase inhibitors. We reveal that inhibitor binding induces a conformational change in c-Src, leading to the association of the active form c-Src with focal adhesion kinase (FAK). Reduction of the inhibitor concentration results in the dissociation of inhibitors from the c-Src-FAK complex, which allows c-Src to phosphorylate FAK and initiate FAK-Grb2-mediated Erk signaling. Furthermore, a drug-resistant mutation in c-Src, which reduces the affinity of inhibitors for c-Src, converts Src inhibitors into facilitators of cell proliferation by enhancing the phosphorylation of FAK and Erk in c-Src-mutated cells. Our data thus reveal paradoxical enhancement of cell growth evoked by target-based kinase inhibitors, providing potentially important clues for the future development of effective and safe cancer treatment

The EZH2 inhibitor tazemetostat upregulates the expression of CCL17/TARC in B‐cell lymphoma and enhances T‐cell recruitment

An inhibitor of the histone methyltransferase enhancer of zeste homologue 2 (EZH2), tazemetostat, has been developed for the treatment of B-cell lymphoma, but its mechanisms of action are not fully elucidated. We screened for genes targeted by tazemetostat in eleven B-cell lymphoma cell lines and found that tazemetostat significantly increased the expression of chemokine (C-C motif) ligand 17 (CCL17)/thymus- and activation-regulated chemokine (TARC) in all, which codes for a chemokine that is a hallmark of Hodgkin/Reed-Sternberg (H/RS) cells in Hodgkin lymphoma. Notably, gene set enrichment analysis demonstrated a positive correlation between the genes upregulated by tazemetostat in five follicular lymphoma (FL) cell lines and those reported to be overexpressed in H/RS cells. The CCL17 promoter region was enriched in repressive histone modification H3K27me3, and tazemetostat induced H3K27 demethylation and activated gene transcription. CCL17 protein secretion was also induced by EZH2 inhibition, which was further enhanced by concurrent CpG stimulation. In vitro transwell migration assay demonstrated that CCL17 produced by tazemetostat-treated B cells enhanced the recruitment of T cells, which had the potential to exert antilymphoma response. Analysis of publicly available human lymphoma databases showed that CCL17 gene expression was inversely correlated with the EZH2 activation signature and significantly paralleled the CD4⁺ and CD8⁺ T-cell–rich signature in FL and germinal center B-cell–like diffuse large B-cell lymphoma. Our findings indicate that tazemetostat can potentially activate antilymphoma response by upregulating CCL17 expression in B-cell lymphoma cells and promote T-cell recruitment, which provides a rationale for its combination with immunotherapy

Next‐generation sequencing in two cases of de novo acute basophilic leukaemia

Acute basophilic leukaemia (ABL) is a rare subtype of acute myeloid leukaemia (AML); therefore, few data are available about its biology. Herein, we analysed two ABL patients using flow cytometry and next-generation sequencing (NGS). Two cell populations were detected by flow cytometry in both patients. In Case no. 1, blasts (CD34⁺, CD203c⁻, CD117⁺, CD123dim⁺) and basophils (CD34⁻, CD203c⁺, CD117±, CD123⁺) were identified, both of which were found by NGS to harbour the 17p deletion and have loss of heterozygosity of TP53. In Case no. 2, blasts (CD33⁺, CD34⁺, CD123⁻) and basophils (CD33⁺, CD34⁺, CD123⁺) were identified. NGS detected NPM1 mutations in either blasts or basophils, and TET2 in both. These data suggest an overlap of the mutational landscape of ABL and AML, including TP53 and TET2 mutations. Moreover, additional mutations or epigenetic factors may contribute for the differentiation into basophilic blasts

Murine Retrovirus Escapes from Murine APOBEC3 via Two Distinct Novel Mechanisms

SummaryAPOBEC3G (A3G) is an antiretroviral host factor that functions by deaminating dC to dU in retroviral cDNA [1–5]. HIV-1 Vif protein counteracts A3G via a ubiquitin-proteasome pathway [6–12]. In the case of a simple retrovirus such as the murine leukemia virus (MLV), it remains unclear why it can replicate in cells expressing APOBEC3 (A3) even though it doesn't possess any accessory proteins such as Vif [2, 13]. In this study, we demonstrate that MLV escapes from murine A3 (mA3) via two distinct novel mechanisms. First, viral RNA (vRNA) blocks the binding of mA3 to Gag, resulting in the exclusion of mA3 from MLV virions. Second, viral protease (vPR) cleaves mA3 after maturation of virions. Here, we suggest that each virus has its own strategy to escape from A3 proteins and that these mechanisms might be used by other viruses that do not possess Vif-like protein. On the other hand, mice possess another form of mA3, Δexon5, that escapes from the cleavage by vPR to show more antiviral activity than the wild type mA3. This also suggests that battles between host intrinsic immunity and viruses have led to the evolution of proteins on both sides

Quantitative Virion Maturation Fluorescence Microscopy

HIV-1 infectivity is achieved through virion maturation. Virus particles undergo structural changes via cleavage of the Gag polyprotein mediated by the viral protease, causing the transition from an uninfectious to an infectious status. The majority of proviruses in people living with HIV-1 treated with combination antiretroviral therapy are defective with large internal deletions. Defective proviral DNA frequently preserves intact sequences capable of expressing viral structural proteins to form virus-like particles whose maturation status is an important factor for chronic antigen-mediated immune stimulation and inflammation. Thus, novel methods to study the maturation capability of defective virus particles are needed to characterize their immunogenicity. To build a quantitative tool to study virion maturation in vitro, we developed a novel single virion visualization technique based on fluorescence resonance energy transfer (FRET). We inserted an optimized intramolecular CFP-YPF FRET donor-acceptor pair bridged with an HIV-1 protease cleavage sequence between the Gag MA-CA domains. This system allowed us to microscopically distinguish mature and immature virions via their FRET signal when the FRET donor and acceptor proteins were separated by the viral protease during maturation. We found that approximately 80% of the FRET labeled virus particles were mature with equivalent infectivity to wild type. The proportion of immature virions was increased by treatment of virus producer cells with a protease inhibitor in a dose-dependent manner, which corresponded to a relative decrease in infectivity. Potential areas of application for this tool are assessing maturation efficiency in different cell type settings of intact or deficient proviral DNA integrated cells. We believe that this FRET-based single-virion imaging platform will facilitate estimating the impact on the immune system of both extracellular intact and defective viruses by quantifying the Gag maturation status

Decreased serum phosphate levels are a useful biomarker to predict occurrence and severity of cytokine release syndrome in chimeric antigen receptor T-cell therapy

サイトカイン放出症候群の発症と重症化を予見する新たな指標 --キメラ抗原受容体T細胞療法における血清リン値が鍵--. 京都大学プレスリリース. 2022-10-19