Giridharan Ramsingh

Role of TP53 mutations in the origin and evolution of therapy-related acute myeloid leukaemia

Therapy-related acute myeloid leukaemia (t-AML) and therapy-related myelodysplastic syndrome (t-MDS) are well-recognized complications of cytotoxic chemotherapy and/or radiotherapy. There are several features that distinguish t-AML from de novo AML, including a higher incidence of TP53 mutations, abnormalities of chromosomes 5 or 7, complex cytogenetics and a reduced response to chemotherapy. However, it is not clear how prior exposure to cytotoxic therapy influences leukaemogenesis. In particular, the mechanism by which TP53 mutations are selectively enriched in t-AML/t-MDS is unknown. Here, by sequencing the genomes of 22 patients with t-AML, we show that the total number of somatic single-nucleotide variants and the percentage of chemotherapy-related transversions are similar in t-AML and de novo AML, indicating that previous chemotherapy does not induce genome-wide DNA damage. We identified four cases of t-AML/t-MDS in which the exact TP53 mutation found at diagnosis was also present at low frequencies (0.003–0.7%) in mobilized blood leukocytes or bone marrow 3–6 years before the development of t-AML/t-MDS, including two cases in which the relevant TP53 mutation was detected before any chemotherapy. Moreover, functional TP53 mutations were identified in small populations of peripheral blood cells of healthy chemotherapy-naive elderly individuals. Finally, in mouse bone marrow chimaeras containing both wild-type and Tp53+/− haematopoietic stem/progenitor cells (HSPCs), the Tp53+/− HSPCs preferentially expanded after exposure to chemotherapy. These data suggest that cytotoxic therapy does not directly induce TP53 mutations. Rather, they support a model in which rare HSPCs carrying age-related TP53 mutations are resistant to chemotherapy and expand preferentially after treatment. The early acquisition of TP53 mutations in the founding HSPC clone probably contributes to the frequent cytogenetic abnormalities and poor responses to chemotherapy that are typical of patients with t-AML/t-MDS.

Primary Plasma Cell Leukemia: A Surveillance, Epidemiology, and End Results Database Analysis Between 1973 and 2004

Primary plasma cell leukemia (PCL) is a rare plasma cell disorder, and current knowledge regarding survival in this disease is limited to small series of patients. Although there has been significant improvement in the survival of patients with multiple myeloma (MM) over the past few decades, it is not known whether there has been a similar trend for PCL.

A phase 1 study of concomitant high-dose lenalidomide and 5-azacitidine induction in the treatment of AML

A phase 1 study of concomitant high-dose lenalidomide and 5-azacitidine induction in the treatment of AML

The molecular landscape of pediatric acute myeloid leukemia reveals recurrent structural alterations and age-specific mutational interactions

We present the molecular landscape of pediatric acute myeloid leukemia (AML) and characterize nearly 1,000 participants in Childrens Oncology Group (COG) AML trials. The COG–National Cancer Institute (NCI) TARGET AML initiative assessed cases by whole-genome, targeted DNA, mRNA and microRNA sequencing and CpG methylation profiling. Validated DNA variants corresponded to diverse, infrequent mutations, with fewer than 40 genes mutated in >2% of cases. In contrast, somatic structural variants, including new gene fusions and focal deletions of MBNL1, ZEB2 and ELF1, were disproportionately prevalent in young individuals as compared to adults. Conversely, mutations in DNMT3A and TP53, which were common in adults, were conspicuously absent from virtually all pediatric cases. New mutations in GATA2, FLT3 and CBL and recurrent mutations in MYC-ITD, NRAS, KRAS and WT1 were frequent in pediatric AML. Deletions, mutations and promoter DNA hypermethylation convergently impacted Wnt signaling, Polycomb repression, innate immune cell interactions and a cluster of zinc finger–encoding genes associated with KMT2A rearrangements. These results highlight the need for and facilitate the development of age-tailored targeted therapies for the treatment of pediatric AML.

Acquired copy number alterations of miRNA genes in acute myeloid leukemia are uncommon

Altered microRNA (miRNA) expression is frequently observed in acute myelogenous leukemia (AML) and has been implicated in leukemic transformation. Whether somatic copy number alterations (CNAs) are a frequent cause of altered miRNA gene expression is largely unknown. Herein, we used comparative genomic hybridization with a custom high-resolution miRNA-centric array and/or whole-genome sequence data to identify somatic CNAs involving miRNA genes in 113 cases of AML, including 50 cases of de novo AML, 18 cases of relapsed AML, 15 cases of secondary AML following myelodysplastic syndrome, and 30 cases of therapy-related AML. We identified a total of 48 somatic miRNA gene-containing CNAs that were not identified by routine cytogenetics in 20 patients (18%). All these CNAs also included one or more protein coding genes. We identified a single case with a hemizygous deletion of MIR223, resulting in the complete loss of miR-223 expression. Three other cases of AML were identified with very low to absent miR-223 expression, an miRNA gene known to play a key role in myelopoiesis. However, in these cases, no somatic genetic alteration of MIR223 was identified, suggesting epigenetic silencing. These data show that somatic CNAs specifically targeting miRNA genes are uncommon in AML.

Suppression of Transposable Elements in Leukemic Stem Cells

Genomic transposable elements (TEs) comprise nearly half of the human genome. The expression of TEs is considered potentially hazardous, as it can lead to insertional mutagenesis and genomic instability. However, recent studies have revealed that TEs are involved in immune-mediated cell clearance. Hypomethylating agents can increase the expression of TEs in cancer cells, inducing ‘viral mimicry’, causing interferon signalling and cancer cell killing. To investigate the role of TEs in the pathogenesis of acute myeloid leukaemia (AML), we studied TE expression in several cell fractions of AML while tracking its development (pre-leukemic haematopoietic stem cells, leukemic stem cells [LSCs], and leukemic blasts). LSCs, which are resistant to chemotherapy and serve as reservoirs for relapse, showed significant suppression of TEs and interferon pathways. Similarly, high-risk cases of myelodysplastic syndrome (MDS) showed far greater suppression of TEs than low-risk cases. We propose TE suppression as a mechanism for immune escape in AML and MDS. Repression of TEs co-occurred with the upregulation of several genes known to modulate TE expression, such as RNA helicases and autophagy genes. Thus, we have identified potential pathways that can be targeted to activate cancer immunogenicity via TEs in AML and MDS.

Prognostic factors influencing survival in solitary plasmacytoma

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Fresh or Cryopreserved CD34+-Selected Mobilized Peripheral Blood Stem and Progenitor Cells for the Treatment of Poor Graft Function after Allogeneic Hematopoietic Cell Transplantation

CD34+-selected stem cell boost (SCB) without conditioning has recently been utilized for poor graft function (PGF) after allogeneic hematopoietic stem cell transplantation with promising results. Unfortunately, many patients have been unable to receive the boost infusion as their donors were unwilling or unable to undergo an additional stem cell collection. Therefore, we conducted this study utilizing either fresh or cryopreserved peripheral blood stem cell products to create CD34+-selected boost infusions for the treatment of PGF. Additionally, to explore relationship of CD34+ dose and response, we included a cohort of donors mobilized with plerixafor in addition to the standard granulocyte colony-stimulating factor (G-CSF). Twenty-six patients with PGF were included in this study. Seventeen donor-recipient pairs were enrolled onto the prospective study; an additional 9 patients treated off protocol were reviewed retrospectively. Three different donor products were used for CD34+ selection: (1) fresh mobilized product using G-CSF only, (2) fresh mobilized products using G-CSF and plerixafor, and (3) cryopreserved cells mobilized with G-CSF. CD34+ cell selection was performed using a CliniMACS. The infusion was not preceded by administration of any chemotherapy or conditioning regimen. The primary objective was hematologic response rate and secondary objectives included CD34+ yields, incidence and severity of acute and chronic graft-versus-host disease (GVHD), overall survival (OS), and relapse-free survival (RFS). The median post-selection CD34+ counts per kilogram of recipient weight were 3.1 × 106, 10.9 × 106, and 1 × 106 for G-CSF only, G-CSF plus plerixafor, and cryopreserved products, respectively. The median CD34+ yields (defined as the number of CD34+ cells after selection/CD34+ cells before CD34+ selection) were 69%, 66%, and 28% for G-CSF only, G-CSF plus plerixafor, and cryopreserved products, respectively. After SCB, 16 of the 26 recipients (62%) had a complete response, including 5 of 8 (63%) who received cryopreserved products. Five had a partial response (19%), resulting in an overall response rate of 81%. One-year RFS and OS were 50% and 65%, respectively. There was no treatment-related toxicity reported other than GVHD: 6 (23%) developed acute GVHD (2 grade I and 4 grade II) and 8 (31%) developed chronic GVHD (2 limited and 6 extensive). Cryopreserved products are viable alternatives to create SCB for the treatment of PGF. When collecting fresh products is an option, the addition of plerixafor increases CD34+ yield over G-CSF alone; however, it is currently unclear if the CD34+ cell dose impacts the efficacy of the SCB.

The presence of Philadelphia chromosome does not confer poor prognosis in adult pre-B acute lymphoblastic leukaemia in the tyrosine kinase inhibitor era - a surveillance, epidemiology, and end results database analysis

The BCR‐ABL1 fusion gene is caused by a translocation between chromosomes 9 and 22, resulting in an abnormal chromosome 22 (Philadelphia chromosome; Ph). Prior to the introduction of tyrosine kinase inhibitors (TKI), the presence of BCR‐ABL1 conferred a poor prognosis in patients with acute lymphoblastic leukaemia (ALL). We compared the survival of Ph+ and Ph−ALL during the period when TKIs were universally available in the US for Ph+ALL, using a Surveillance, Epidemiology, and End Results (SEER) Database analysis. A total of 2694 patients with pre‐B ALL (206 Ph+ALL; 2488 Ph−ALL) aged ≥18 years, who were diagnosed between 2010 and 2014, were identified in SEER registries. The median overall survival (OS) was 32 months in Ph+ALL (95% confidence interval [CI] 18 months‐not reached) and 27 months (95% CI 24–30 months) in Ph−ALL (Log‐rank test P‐value 0·34). Older age was associated with worse prognosis in both Ph+ALL and Ph−ALL. Age‐adjusted OS was inferior in Hispanics and African‐Americans compared to non‐Hispanic whites. Survival of pre‐B ALL shows continued improvement with time. Philadelphia chromosome status does not confer poor prognosis in pre‐B ALL in the TKI era: prognostic factors in pre‐B ALL should be re‐evaluated in the light of this finding.

Author Correction: Suppression of Transposable Elements in Leukemic Stem Cells

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.