Response and resistance to CDK12 inhibition in aggressive B-cell lymphomas.

Despite significant progress in the treatment of patients with diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL), the prognosis of patients with relapsed disease remains poor due to the emergence of drug resistance and subsequent disease progression. Identification of novel targets and therapeutic strategies for these diseases represents an urgent need. Here, we report that both MCL and DLBCL are exquisitely sensitive to transcription-targeting drugs, in particular THZ531, a covalent inhibitor of cyclin-dependent kinase 12 (CDK12). By implementing pharmacogenomics and a cell-based drug screen, we found that THZ531 leads to inhibition of oncogenic transcriptional programs, especially the DNA damage response pathway, MYC target genes and the mTOR-4EBP1-MCL-1 axis, contributing to dramatic lymphoma suppression in vitro. We also identified de novo and established acquired THZ531-resistant lymphoma cells conferred by over-activation of the MEK-ERK and PI3K-AKT-mTOR pathways and upregulation of multidrug resistance-1 (MDR1) protein. Of note, EZH2 inhibitors reversed resistance to THZ531 by competitive inhibition of MDR1 and, in combination with THZ531, synergistically inhibited MCL and DLBCL growth in vitro. Our study indicates that CDK12 inhibitors, alone or together with EZH2 inhibitors, offer promise as novel effective approaches for difficult-to-treat DLBCL and MCL.

Transcriptional programming drives Ibrutinib-resistance evolution in mantle cell lymphoma.

Ibrutinib, a bruton's tyrosine kinase (BTK) inhibitor, provokes robust clinical responses in aggressive mantle cell lymphoma (MCL), yet many patients relapse with lethal Ibrutinib-resistant (IR) disease. Here, using genomic, chemical proteomic, and drug screen profiling, we report that enhancer remodeling-mediated transcriptional activation and adaptive signaling changes drive the aggressive phenotypes of IR. Accordingly, IR MCL cells are vulnerable to inhibitors of the transcriptional machinery and especially so to inhibitors of cyclin-dependent kinase 9 (CDK9), the catalytic subunit of the positive transcription elongation factor b (P-TEFb) of RNA polymerase II (RNAPII). Further, CDK9 inhibition disables reprogrammed signaling circuits and prevents the emergence of IR in MCL. Finally, and importantly, we find that a robust and facile ex vivo image-based functional drug screening platform can predict clinical therapeutic responses of IR MCL and identify vulnerabilities that can be targeted to disable the evolution of IR.

BURMESE ROOFED TURTLE (BATAGUR TRIVITTATA) DISEASE SCREENING IN MYANMAR.

The Burmese roofed turtle (Batagur trivittata), a critically endangered freshwater turtle, is endemic to Myanmar. Once thought to be extinct, remnant wild populations were discovered in 2001 and limited captive individuals identified in pagoda ponds or confiscated from fishers in Myanmar. These and their offspring are maintained in five facilities in Myanmar and form the basis of a conservation program (habitat protection, captive breeding, nest protection, egg collection, head-starting, and release). Prerelease health screenings were performed in 2014 and 2018 at Yadanabon Zoological Gardens, a head-starting facility in Limpha Village, and Lawkanandar Wildlife Park. One hundred forty-three turtles were assessed (37 male, 50 female, 56 juveniles [too young to determine sex]; two females were assessed in both years), age range of 1 to 12 y (one unknown age adult founder), and body mass range of 0.111 to 32.72 kg. Health evaluations both years included physical examination and combined choanal/cloacal swab samples for polymerase chain reaction testing of the potential chelonian pathogens intranuclear coccidia, Mycoplasma, Herpesvirus, Ranavirus, and Adenovirus (not all tests performed each year). In 2018, cloacal swabs from 30 and 20 turtles at the Yadanabon Zoological Gardens and Lawkanandar Wildlife Park, respectively, were cultured for Salmonella. All turtles were assessed as healthy based on normal physical examination findings, and all had negative test results. Prerelease health screening, such as performed in this study, is an important component of release, reintroduction, and translocation projects to prevent introduction of novel pathogens into naïve wild populations.

First description of neonate Batagur trivittata (Testudines: Geoemydidae).

The Burmese Roofed Turtle (Batagur trivittata Duméril Bibron, 1835) is a large (straight-line carapace length [CL] to 620 mm; Platt et al., 2019), aquatic, herbivorous turtle endemic to the major river systems of Myanmar (Smith 1931; TTWG 2017). Although historically widespread and apparently abundant, long-term population declines resulted from chronic egg collecting, subsistence harvesting of adults, and loss of critical nesting habitat (Platt et al. 2017a). By the late 1990s B. trivittata was considered a candidate for Extinct status (Bhupathy et al. 2000) until a living specimen purchased in a Chinese wildlife market came into the possession of an American turtle collector in the early 2000s (Platt et al. 2005; W.P. McCord, pers. comm.). Shortly thereafter, field surveys "rediscovered" two remnant populations in the Dokhtawady and upper Chindwin Rivers (Platt et al. 2005; Kuchling et al. 2006). Intense ex- and in-situ recovery efforts were launched shortly thereafter and continue today (Kuchling Tint Lwin 2004; Çilingir et al. 2017).

Study of the perceptions of the educational environment among undergraduate medical students of Taylor's University.

This article was migrated. The article was marked as recommended. A conducive educational environment is vital to successful learning. Perception of students about their particular educational environment may vary depending on their educational background, gender, level of study, and many other factors. Awareness and understanding of the students' perception of educational environment are a key to improve our teaching and learning environment. The aim of the study was to determine the perception of undergraduate medical students of Taylor's University, Malaysia on their educational environment. A cross sectional cohort study was conducted among preclinical and clinical students simultaneously at Taylor's University, School of Medicine in July 2019. Overall total scores of perceptions (136.55 ± 19.6) and those for the subscales were very satisfactory and similar to those of other local universities as well as international universities. There was a significant difference between preclinical and clinical students in two domains; Perception of Course Organizers and Academic Self-Perception, with higher scores among clinical students in all. There was a significant difference between students with Grade 'B' and those with Grade 'C' in the mean total score and Perceptions of Atmosphere. These results, in spite of being satisfactory, urge us to seek methods of and opportunities for further enhancement of the students' education environment.

BCL2 Amplicon Loss and Transcriptional Remodeling Drives ABT-199 Resistance in B Cell Lymphoma Models.

Drug-tolerant "persister" tumor cells underlie emergence of drug-resistant clones and contribute to relapse and disease progression. Here we report that resistance to the BCL-2 targeting drug ABT-199 in models of mantle cell lymphoma and double-hit lymphoma evolves from outgrowth of persister clones displaying loss of 18q21 amplicons that harbor BCL2. Further, persister status is generated via adaptive super-enhancer remodeling that reprograms transcription and offers opportunities for overcoming ABT-199 resistance. Notably, pharmacoproteomic and pharmacogenomic screens revealed that persisters are vulnerable to inhibition of the transcriptional machinery and especially to inhibition of cyclin-dependent kinase 7 (CDK7), which is essential for the transcriptional reprogramming that drives and sustains ABT-199 resistance. Thus, transcription-targeting agents offer new approaches to disable drug resistance in B-cell lymphomas.

PLK1 stabilizes a MYC-dependent kinase network in aggressive B cell lymphomas.

Concordant activation of MYC and BCL-2 oncoproteins in double-hit lymphoma (DHL) results in aggressive disease that is refractory to treatment. By integrating activity-based proteomic profiling and drug screens, polo-like kinase-1 (PLK1) was identified as an essential regulator of the MYC-dependent kinome in DHL. Notably, PLK1 was expressed at high levels in DHL, correlated with MYC expression, and connoted poor outcome. Further, PLK1 signaling augmented MYC protein stability, and in turn, MYC directly induced PLK1 transcription, establishing a feed-forward MYC-PLK1 circuit in DHL. Finally, inhibition of PLK1 triggered degradation of MYC and of the antiapoptotic protein MCL-1, and PLK1 inhibitors showed synergy with BCL-2 antagonists in blocking DHL cell growth, survival, and tumorigenicity, supporting clinical targeting of PLK1 in DHL.

Unification of de novo and acquired ibrutinib resistance in mantle cell lymphoma.

The novel Bruton's tyrosine kinase inhibitor ibrutinib has demonstrated high response rates in B-cell lymphomas; however, a growing number of ibrutinib-treated patients relapse with resistance and fulminant progression. Using chemical proteomics and an organotypic cell-based drug screening assay, we determine the functional role of the tumour microenvironment (TME) in ibrutinib activity and acquired ibrutinib resistance. We demonstrate that MCL cells develop ibrutinib resistance through evolutionary processes driven by dynamic feedback between MCL cells and TME, leading to kinome adaptive reprogramming, bypassing the effect of ibrutinib and reciprocal activation of PI3K-AKT-mTOR and integrin-ß1 signalling. Combinatorial disruption of B-cell receptor signalling and PI3K-AKT-mTOR axis leads to release of MCL cells from TME, reversal of drug resistance and enhanced anti-MCL activity in MCL patient samples and patient-derived xenograft models. This study unifies TME-mediated de novo and acquired drug resistance mechanisms and provides a novel combination therapeutic strategy against MCL and other B-cell malignancies.

A microenvironment-mediated c-Myc/miR-548m/HDAC6 amplification loop in non-Hodgkin B cell lymphomas.

A dynamic interaction occurs between the lymphoma cell and its microenvironment, with each profoundly influencing the behavior of the other. Here, using a clonogenic coculture growth system and a xenograft mouse model, we demonstrated that adhesion of mantle cell lymphoma (MCL) and other non-Hodgkin lymphoma cells to lymphoma stromal cells confers drug resistance, clonogenicity, and induction of histone deacetylase 6 (HDAC6). Furthermore, stroma triggered a c-Myc/miR-548m feed-forward loop, linking sustained c-Myc activation, miR-548m downregulation, and subsequent HDAC6 upregulation and stroma-mediated cell survival and lymphoma progression in lymphoma cell lines, primary MCL and other B cell lymphoma cell lines. Treatment with an HDAC6-selective inhibitor alone or in synergy with a c-Myc inhibitor enhanced cell death, abolished cell adhesion­mediated drug resistance, and suppressed clonogenicity and lymphoma growth ex vivo and in vivo. Together, these data suggest that the lymphoma-stroma interaction in the lymphoma microenvironment directly impacts the biology of lymphoma through genetic and epigenetic regulation, with HDAC6 and c-Myc as potential therapeutic targets.

Failure to improve door-to-needle time by switching to emergency physician-initiated thrombolysis for ST elevation myocardial infarction.

INTRODUCTION: Achieving target door-needle times for ST elevation myocardial infarction remains challenging. Data on emergency department (ED) doctor-led thrombolysis in developing countries and factors causing delay are limited. OBJECTIVES: To assess the effect on door-needle times by transferring responsibility for thrombolysis to the ED doctors and to identify predictors of prolonged door-needle times. METHODOLOGY: Data on medical on-call team-led thrombolysis at a tertiary Asian hospital were prospectively collected from May 2007 to Aug 2008 (1st study period). In September 2008, ED doctors were empowered to perform thrombolysis. The practice change was accompanied by new guidelines, tick chart implementation, and training sessions. Data were then consecutively collected from September 2008 to May 2009 (2nd study period). Door-to-needle times for the 1st and 2nd study periods were compared. All cases were analysed for factors of delay by multiple logistic regression. RESULTS: 297 patients were thrombolysed, 169 by the medical on-call team during the 1st study period and 128 by the ED doctors during the 2nd study period. Median door-needle times were 54 and 48 min, respectively (p=0.76). Significant delays were predicted by 'incorrect initial ECG interpretation' (adjusted OR (aOR) 14.3), 'inappropriate triage' (aOR 10.4) and 'multiple referrals' (aOR 5.9). No cases of inappropriate thrombolysis were recorded. CONCLUSIONS: Transfer of responsibility for thrombolysis to the ED doctors did not improve door-needle times despite measures introduced to facilitate this change. Key causative factors for this failure were identified.

Coordinated silencing of MYC-mediated miR-29 by HDAC3 and EZH2 as a therapeutic target of histone modification in aggressive B-Cell lymphomas.

We investigated the transcriptional and epigenetic repression of miR-29 by MYC, HDAC3, and EZH2 in mantle cell lymphoma and other MYC-associated lymphomas. We demonstrate that miR-29 is repressed by MYC through a corepressor complex with HDAC3 and EZH2. MYC contributes to EZH2 upregulation via repression of the EZH2 targeting miR-26a, and EZH2 induces MYC via inhibition of the MYC targeting miR-494 to create positive feedback. Combined inhibition of HDAC3 and EZH2 cooperatively disrupted the MYC-EZH2-miR-29 axis, resulting in restoration of miR-29 expression, downregulation of miR-29-targeted genes, and lymphoma growth suppression in vitro and in vivo. These findings define a MYC-mediated miRNA repression mechanism, shed light on MYC lymphomagenesis mechanisms, and reveal promising therapeutic targets for aggressive B-cell malignancies.

Follicular dendritic cell-dependent drug resistance of non-Hodgkin lymphoma involves cell adhesion-mediated Bim down-regulation through induction of microRNA-181a.

Follicular dendritic cells (FDCs), an essential component of the lymph node microenvironment, regulate and support B-lymphocyte differentiation, survival, and lymphoma progression. Here, we demonstrate that adhesion of mantle cell lymphoma and other non-Hodgkin lymphoma cells to FDCs reduces cell apoptosis and is associated with decreased levels of the proapoptotic protein, Bim. Bim down-regulation is posttranscriptionally regulated via up-regulation of microRNA-181a (miR-181a). miR-181a overexpression decreases, whereas miR-181a inhibition increases Bim levels by directly targeting Bim. Furthermore, we found that cell adhesion-up-regulated miR-181a contributes to FDC-mediated cell survival through Bim down-regulation, implicating miR-181a as an upstream effector of the Bim-apoptosis signaling pathway. miR-181a inhibition and Bim upregulation significantly suppressed FDC-mediated protection against apoptosis in lymphoma cell lines and primary lymphoma cells. Thus, FDCs protect B-cell lymphoma cells against apoptosis, in part through activation of a miR-181a-dependent mechanism involving down-regulation of Bim expression. We demonstrate, for the first time, that cell-cell contact controls tumor cell survival and apoptosis via microRNA in mantle cell and other non-Hodgkin lymphomas. Regulation of microRNAs by B-cell-FDC interaction may support B-cell survival, representing a novel molecular mechanism for cell adhesion-mediated drug resistance and a potential therapeutic target in B-cell lymphomas.

microRNA expression profile and identification of miR-29 as a prognostic marker and pathogenetic factor by targeting CDK6 in mantle cell lymphoma.

Mantle cell lymphoma (MCL) is one of the most aggressive B-cell lymphomas. Although several protein-coding genes are altered, expression signature and importance of microRNA (miRNA) have not been well documented in this malignancy. Here, we performed miRNA expression profile in 30 patients with MCL using a platform containing 515 human miRNAs. Eighteen miRNAs were down-regulated and 21 were up-regulated in MCL compared with normal B lymphocytes. The most frequently altered miRNAs are decrease of miR-29a/b/c, miR-142-3p/5p, and miR-150 and increase of miR-124a and miR-155. Notably, expression levels of miR-29 family are associated with prognosis. The patients with significant down-regulated miR-29 had short survival compared with those who express relatively high levels of miR-29. The prognostic value of miR-29 is comparable with the Mantle Cell Lymphoma International Prognostic Index. Furthermore, we demonstrate miR-29 inhibition of CDK6 protein and mRNA levels by direct binding to 3'-untranslated region. Inverse correlation between miR-29 and CDK6 was observed in MCL. Because cyclin D1 overexpression is a primary event and exerts its function through activation of CDK4/CDK6, our results in primary MCL cells indicate that down-regulation of miR-29 could cooperate with cyclin D1 in MCL pathogenesis. Thus, our findings provide not only miRNA expression signature but also a novel prognostic marker and pathogenetic factor for this malignancy.

Cell adhesion induces p27Kip1-associated cell-cycle arrest through down-regulation of the SCFSkp2 ubiquitin ligase pathway in mantle-cell and other non-Hodgkin B-cell lymphomas.

Mounting evidence suggests that dynamic interactions between a tumor and its microenvironment play a critical role in tumor development, cell-cycle progression, and response to therapy. In this study, we used mantle cell lymphoma (MCL) as a model to characterize the mechanisms by which stroma regulate cell-cycle progression. We demonstrated that adhesion of MCL and other non-Hodgkin lymphoma (NHL) cells to bone marrow stromal cells resulted in a reversible G(1) arrest associated with elevated p27(Kip1) and p21 (WAF1) proteins. The adhesion-mediated p27(Kip1) and p21 increases were posttranslationally regulated via the down-regulation of Skp2, a subunit of SCF(Skp2) ubiquitin ligase. Overexpression of Skp2 in MCL decreased p27(Kip1), whereas inhibition of Skp2 by siRNA increased p27(Kip1) and p21 levels. Furthermore, we found cell adhesion up-regulated Cdh1 (an activating subunit of anaphase-promoting complex [APC] ubiquitin ligase), and reduction of Cdh1 by siRNA induced Skp2 accumulation and hence p27(Kip1) degradation, thus implicating Cdh1 as an upstream effector of the Skp2/p27(Kip1) signaling pathway. Overall, this report, for the first time, demonstrates that cell-cell contact controls the tumor cell cycle via ubiquitin-proteasome proteolytic pathways in MCL and other NHLs. The understanding of this novel molecular pathway may prove valuable in designing new therapeutic approaches for modifying tumor cell growth and response to therapy.