Overexpression of Mdm36 reveals Num1 foci that mediate dynein-dependent microtubule sliding in budding yeast

The current model for spindle positioning requires attachment of the microtubule (MT) motor cytoplasmic dynein to the cell cortex, where it generates pulling force on astral MTs to effect spindle displacement. How dynein is anchored by cortical attachment machinery to generate large spindle-pulling forces remains unclear. Here, we show that cortical clustering of Num1, the yeast dynein attachment molecule, is limited by its assembly factor Mdm36. Overexpression of Mdm36 results in an overall enhancement of Num1 clustering but reveals a population of dim Num1 clusters that mediate dynein anchoring at the cell cortex. Direct imaging shows that bud-localized, dim Num1 clusters containing around only six Num1 molecules mediate dynein-dependent spindle pulling via a lateral MT sliding mechanism. Mutations affecting Num1 clustering interfere with mitochondrial tethering but do not interfere with the dynein-based spindle-pulling function of Num1. We propose that formation of small ensembles of attachment molecules is sufficient for dynein anchorage and cortical generation of large spindle-pulling forces.This article has an associated First Person interview with the first author of the paper.

Abstract 4492: Characterization of the T-Cell receptor repertoire in patients with acute myeloid leukemia treated with 5-Azacytidine plus chemotherapy

Acute Myeloid Leukemia (AML) is a hematological malignancy with a 5 year overall survival of less than 30%. DNA hypomethylating agents such as 5-Azacytidine (5-Aza) have been increasingly used in AML therapy. The effect of hypomethylating agents on T-cell driven anti-leukemia responses remains unclear. For anti-leukemia responses, T-cells must express a T-cell receptor (TCR) with specificity for cancer antigens. TCR recombination, the rearrangement of V, D (beta only) and J segments across the TCR alpha and beta loci into a mature TCR locus, shapes the antigen specificity of TCRs. DNA methylation across the TCR loci may limit the rearrangement of particular V, D, J segments and impact TCR repertoire composition. Whether 5-Aza can alter TCR loci methylation patterns, increase TCR diversity and enhance T-cell driven anti-leukemia responses is unknown.

In a cohort of 23 patient with AML, we performed TCR-seq on pre- (diagnostic) and post-therapy (day 5 post 5-Aza) peripheral blood RNA samples obtained from 13 responders and 10 non-responders. Illumina compatible libraries were generated from patient samples using a 5'RACE like approach and sequenced on the MiSeq platform, generating 300x2bp reads. Reads were processed and analyzed using MiXCR and VDJTools, respectively. GraphPad Prism 8 (Two-sided T test) was used for statistical comparisons, P values < 0.05 were considered significant after adjusting for multiple comparisons using the Bonferroni-Dunn method.

We obtained an average of 1,146,043 (SD± 767,216) reads and identified an average of 15,732 (SD ± 17,388) clones per sample. We compared pre- and post-therapy TCR diversity among both outcome groups using the Shannon diversity index. TCR diversity did not significantly change following 5-Aza treatment (4827 vs 6159, P= 0.55). Also, TCR diversity was not significantly different between outcome groups pre- and post-therapy. We designated clones as minor (< 10 reads) or major (> 10 reads). We compared pre- and post-therapy minor clone TRBV exon patterns and discovered a 2.2 fold increase in unique clones containing TRBV16 among responders post therapy (P = 0.017). We also observed a 2.5 fold increase in unique clones containing TRBV7-4 in non-responders post therapy (P = 0.034). There were no significant exon pattern changes in non-stratified analysis. When pre-therapy minor clone exon patterns were compared between outcome groups, a higher frequency of unique clones containing TRBV12-2 in responders versus non-responders was observed (2.8 fold, P < 0.001). In addition, we observed a higher frequency of major clones containing TRBV12-5 among responders post therapy (2.4 fold, P = 0.0558). In the pre-therapy samples, there was a higher frequency of clones containing TRBV5-4 among responders compared to non-responders (2.7 fold, P =0.045).

In conclusion, changes in TCR repertoire features such as the utilization of specific V exons may associate with response to 5-Azacytidine therapy.

Citation Format: John Beckford, Noreen Fulton, Toyosi Odenike, Wendy Stock, Houda Alachkar. Characterization of the T-Cell receptor repertoire in patients with acute myeloid leukemia treated with 5-Azacytidine plus chemotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4492.

Deciphering the TCR Repertoire to Solve the COVID-19 Mystery

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected several millions and killed more than quarter of a million worldwide to date. Important questions have remained unanswered: why some patients develop severe disease, while others do not; and what roles do genetic variabilities play in the individual immune response to this viral infection. Here, we discuss the critical role T cells play in the orchestration of the antiviral response underlying the pathogenesis of the disease, COVID-19. We highlight the scientific rationale for comprehensive and longitudinal TCR analyses in COVID-19 and reason that analyzing TCR repertoire in COVID-19 patients would reveal important findings that may explain the outcome disparity observed in these patients. Finally, we provide a framework describing the different strategies, the advantages, and the challenges involved in obtaining useful TCR repertoire data to advance our fight against COVID-19.

Upregulation of the EMT marker vimentin is associated with poor clinical outcome in acute myeloid leukemia

Background

Vimentin (VIM) is a type III intermediate filament that maintains cell integrity, and is involved in cell migration, motility and adhesion. When overexpressed in solid cancers, vimentin drives epithelial to mesenchymal transition (EMT) and ultimately, metastasis. The effects of its overexpression in AML are unclear.

Methods

In this study, we analyzed the TCGA data of 173 AML patients for which complete clinical and expression data were available. In this analysis, we assessed the association between VIM mRNA expression and patient’s clinical and molecular characteristics including clinical outcome.

Results

VIM overexpression was associated with higher white blood count (< p = 0.0001). Patients with high VIM expression have worse overall survival (OS) and disease-free survival (DFS) compared with patients with low VIM expression (median OS; 7.95 months vs 19.2 months; p = 0.029). After age-stratification, high VIM expression was significantly associated with worse overall survival in older patients (age ≥ 60; median OS: 5.4 vs 9.9 months: p = 0.0257) but not in younger patients (age < 60). In stratification analysis according to cytogenetic status, high VIM expression was significantly associated with shorter OS (7.95 vs 24.6 months: p = 0.0102) in cytogenetically normal, but not in cytogenetic abnormal AML.

Conclusions

Collectively, the data indicate that overexpression of the EMT marker vimentin is associated with poor clinical outcome in older patients with cytogenetically normal AML; and therefore may play a role in this disease.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1539-y) contains supplementary material, which is available to authorized users.

Specialist vaccination advice and pockets of resistance to MMR vaccination: lessons from an outbreak of measles

An outbreak of measles was associated with a private nursery school in north west London. Sixteen cases were identified of whom 13 were laboratory confirmed. The majority of cases were aged three years or younger. Older cases were siblings of younger cases. None of the cases had been vaccinated against measles. In the nursery school 33% of the children had not received MMR vaccination. Based on specialist advice from the Health Protection Agency the outbreak control team recommended that children with no history of MMR vaccination should have a first MMR dose as soon as possible and that children with one MMR dose should receive the second dose as soon as possible (minimum of one month between doses). Some parents had strong negative views about MMR and represented 'pockets of resistance' to vaccination advice. The specialist vaccination advice, which was different to national immunisation guidelines, also caused some confusion amongst other health professionals. With a decrease in MMR vaccination uptake and resulting increased potential for future measles outbreaks, clinicians should be aware of and understand specialist vaccination advice intended to deal with outbreaks.

Efficacy of prednisone in refractory multiple myeloma and measurement of glucocorticoid receptors. A Southwest Oncology Group study

BACKGROUND

Prednisone is an active drug in the treatment of multiple myeloma. The optimal dose, frequency, and role of glucocorticoid receptors (GR) in response to prednisone is unknown.

PURPOSE

The purposes of this study were (1) to estimate the response rate of alternate-day high dose prednisone in patients with relapsing and refractory multiple myeloma; (2) to measure the rate of GR levels; and (3) to correlate the response of prednisone with GR status.

PATIENTS AND METHODS

Between 8/86 and 1/90, 127 patients were entered onto the study with 121 evaluable for response. The number of GR sites/cell was determined on mononuclear cells isolated from pretreatment bone marrow aspirates using a one point GR binding assay. Patients received prednisone 100 mg po qod x 2 weeks, followed by 50 mg po qod x 10 weeks.

RESULTS

The overall response rate was 10% (95% CI: 5-15%) with a median survival of 11.8 months. The GR sites/cell ranged from 0-53,212 with a mean of 8,371 sites/cells. Stratification of GR sites into 0-2,500, 2,501-6,000 and > 6,000 sites/cells was associated with a response rate of 6%, 27% and 4% respectively (p = 0.009). The median survival of patients in these categories was 8.1, 14.9 and 10.6 months respectively. This was not significant by the logrank test (p = 0.11). Although myeloma patients with intermediate levels of GR sites/cell initially responded more favorably to prednisone, their long-term survival was not significantly improved.

CONCLUSIONS

Alternate-day high-dose prednisone was well tolerated and may provide palliative benefit for a subset of patients with relapsing and refractory multiple myeloma. The survival of patients on this study was comparable to that reported with other but more toxic doses of glucocorticoids.