Elevated levels of cyclin A1 and A (A2) mRNA in acute myeloid leukaemia are associated with increased survival

Histone methyltransferase EZH2 epigenetically affects CCNA1 expression in acute myeloid leukemia

Cyclin A1 (CCNA1) is an alternative A-type cyclin that is expressed in acute myeloid leukemia (AML). However, its functions in AML cell chemoresistance, an important cause for mortality, are incompletely understood. The purpose of this study was to expound the role and potential mechanism of CCNA1 in AML cell chemoresistance. Upregulation of CCNA1 promoted resistance of AML cells to PKC412, AC220, and AraC. Mechanistically, it was confirmed that CCNA1 transcription was negatively regulated by forkhead box A2 (FOXA2), and the downregulation of FOXA2 promoted chemoresistance in AML cells. Moreover, the promoter sequence of CCNA1 has a significant H3K27me3 modification. Enhancer of zeste homolog 2 (EZH2) enhanced H3K27me3 modification of CCNA1 promoter to inhibit CCNA1 expression, thus promoting sensitivity of AML cells to drugs. Taken together, these findings lead to deeper insights into the mechanism of AML cell chemo-sensitivity by inhibiting CCNA1 at the transcriptional level.

Deubiquitinating enzyme inhibitor alleviates cyclin A1-mediated proteasome inhibitor tolerance in mixed-lineage leukemia

Drug resistance is a significant obstacle to effective cancer treatment. Drug resistance develops from initially reversible drug-tolerant cancer cells, which offer therapeutic opportunities to impede cancer relapse. The mechanisms of resistance to proteasome inhibitor (PI) therapy have been investigated intensively, however the ways by which drug-tolerant cancer cells orchestrate their adaptive responses to drug challenges remain largely unknown. Here, we demonstrated that cyclin A1 suppression elicited the development of transient PI tolerance in mixed-lineage leukemia (MLL) cells. This adaptive process involved reversible downregulation of cyclin A1, which promoted PI resistance through cell-cycle arrest. PI-tolerant MLL cells acquired cyclin A1 dependency, regulated directly by MLL protein. Loss of cyclin A1 function resulted in the emergence of drug tolerance, which was associated with patient relapse and reduced survival. Combination treatment with PI and deubiquitinating enzyme (DUB) inhibitors overcame this drug resistance by restoring cyclin A1 expression through chromatin crosstalk between histone H2B monoubiquitination and MLL-mediated histone H3 lysine 4 methylation. These results reveal the importance of cyclin A1-engaged cell-cycle regulation in PI resistance in MLL cells, and suggest that cell-cycle re-entry by DUB inhibitors may represent a promising epigenetic therapeutic strategy to prevent acquired drug resistance.

AML risk stratification models utilizing ELN-2017 guidelines and additional prognostic factors: a SWOG report

Background

The recently updated European LeukemiaNet risk stratification guidelines combine cytogenetic abnormalities and genetic mutations to provide the means to triage patients with acute myeloid leukemia for optimal therapies. Despite the identification of many prognostic factors, relatively few have made their way into clinical practice.

Methods

In order to assess and improve the performance of the European LeukemiaNet guidelines, we developed novel prognostic models using the biomarkers from the guidelines, age, performance status and select transcript biomarkers. The models were developed separately for mononuclear cells and viable leukemic blasts from previously untreated acute myeloid leukemia patients (discovery cohort, N = 185) who received intensive chemotherapy. Models were validated in an independent set of similarly treated patients (validation cohort, N = 166).

Results

Models using European LeukemiaNet guidelines were significantly associated with clinical outcomes and, therefore, utilized as a baseline for comparisons. Models incorporating age and expression of select transcripts with biomarkers from European LeukemiaNet guidelines demonstrated higher area under the curve and C-statistics but did not show a substantial improvement in performance in the validation cohort. Subset analyses demonstrated that models using only the European LeukemiaNet guidelines were a better fit for younger patients (age < 55) than for older patients. Models integrating age and European LeukemiaNet guidelines visually showed more separation between risk groups in older patients. Models excluding results for ASXL1, CEBPA, RUNX1 and TP53, demonstrated that these mutations provide a limited overall contribution to risk stratification across the entire population, given the low frequency of mutations and confounding risk factors.

Conclusions

While European LeukemiaNet guidelines remain a critical tool for triaging patients with acute myeloid leukemia, the findings illustrate the need for additional prognostic factors, including age, to improve risk stratification.

Differential peripheral blood gene expression profile based on Her2 expression on primary tumors of breast cancer patients

Breast cancer prognosis and treatment is highly dependent on the molecular features of the primary tumors. These tumors release specific molecules into the environment that trigger characteristic responses into the circulatory cells. In this study we investigated the expression pattern of 84 genes known to be involved in breast cancer signaling in the peripheral blood of breast cancer patients with ER-, PR- primary tumors. The patients were grouped according to Her2 expression on the primary tumors in Her2+ and Her2- cohorts. Transcriptional analysis revealed 15 genes to be differentially expressed between the two groups highlighting that Her2 signaling in primary tumors could be associated with specific blood gene expression. We found CCNA1 to be up-regulated, while ERBB2, RASSF1, CDH1, MKI67, GATA3, GLI1, SFN, PTGS2, JUN, NOTCH1, CTNNB1, KRT8, SRC, and HIC1 genes were down-regulated in the blood of triple negative breast cancer patients compared to Her2+ cohort. IPA network analysis predicts that the identified genes are interconnected and regulate each other. These genes code for cell cycle regulators, cell adhesion molecules, transcription factors or signal transducers that modulate immune signaling, several genes being also associated with cancer progression and treatment response. These results indicate an altered immune signaling in the peripheral blood of triple negative breast cancer patients. The involvement of the immune system is necessary in favorable treatment response, therefore these results could explain the low response rates observed for triple negative breast cancer patients.

Identification of genes with abnormal expression changes in acute myeloid leukemia

Acute myeloid leukemia (AML) is one of the most common and deadly forms of hematopoietic malignancies. We hypothesized that microarray studies could identify previously unrecognized expression changes that occur only in AML blasts. We were particularly interested in those genes with increased expression in AML, believing that these genes may be potential therapeutic targets. To test this hypothesis, we compared gene expression profiles between normal hematopoietic cells from 38 healthy donors and leukemic blasts from 26 AML patients. Normal hematopoietic samples included CD34+ selected cells (N = 18), unselected bone marrows (N = 10), and unselected peripheral bloods (N = 10). Twenty genes displayed AML-specific expression changes that were not found in the normal hematopoietic cells. Subsequent analyses using microarray data from 285 additional AML patients confirmed expression changes for 13 of the 20 genes. Seven genes (BIK, CCNA1, FUT4, IL3RA, HOMER3, JAG1, WT1) displayed increased expression in AML, while 6 genes (ALDHA1A, PELO, PLXNC1, PRUNE, SERPINB9, TRIB2) displayed decreased expression. Quantitative RT/PCR studies for the 7 over-expressed genes were performed in an independent set of 9 normal and 21 pediatric AML samples. All 7 over-expressed genes displayed an increased expression in the AML samples compared to normals. Three of the 7 over-expressed genes (WT1, CCNA1, and IL3RA) have already been linked to leukemogenesis and/or AML prognosis, while little is known about the role of the other 4 over-expressed genes in AML. Future studies will determine their potential role in leukemogenesis and their clinical significance.

Expression of cyclin A1 and cell cycle proteins in hematopoietic cells and acute myeloid leukemia and links to patient outcome

Abnormal expression of several key regulators essential for G1/S transitions has been implicated in tumorigenesis. A critical role of cyclin A1 in the development of acute myeloid leukemia (AML) has previously been demonstrated in transgenic mice. Our present study focused on the expression and prognostic significance of cyclin A1 and a panel of cell cycle regulatory proteins including cyclin A2, cyclin B1, cyclin E, CDK1, CDK2, p21 and p27 in bone marrow samples from 40 patients with AML. Freshly isolated CD34+ hematopoietic cells and bone marrow samples from 10 healthy donors were also assessed for cell type- and subcellular-specific expression of the cell cycle regulatory proteins. The level of cyclin A1 expression was the only factor that showed a significant correlation with patient outcome. In log-rank test stratified by levels of cyclin A1 expression, patients with high levels of cyclin A1 had significantly worse overall survival (OS) (P = 0.012) compared to those with low levels. Further, patients with high levels of cyclin A1 had significantly lower disease-free survival (DFS) (P = 0.028). Multivariate analysis indicated that cyclin A1 protein expression was an independent prognostic factor for predicting DFS (P = 0.035) and OS (P = 0.045). No correlation between cyclin A1 expression and age was found. However, expression of cyclin A2, cyclin B1, cyclin E, CDK1, CDK2, p21 and p27 did not show prognostic significance in these AML patients.

The role of CREB as a proto-oncogene in hematopoiesis and in acute myeloid leukemia

CREB is a transcription factor that functions in glucose homeostasis, growth factor-dependent cell survival, and memory. In this study, we describe a role of CREB in human cancer. CREB overexpression is associated with increased risk of relapse and decreased event-free survival. CREB levels are elevated in blast cells from patients with acute myeloid leukemia. To understand the role of CREB in leukemogenesis, we studied the biological consequences of CREB overexpression in primary human leukemia cells, leukemia cell lines, and transgenic mice. Our results demonstrate that CREB promotes abnormal proliferation and survival of myeloid cells in vitro and in vivo through upregulation of specific target genes. Thus, we report that CREB is implicated in myeloid cell transformation.