Targeting TP53-Mutated Acute Myeloid Leukemia: Research and Clinical Developments.

TP53 is a key tumor suppressor gene that plays an important role in regulating apoptosis, senescence, and DNA damage repair in response to cellular stress. Although somewhat rare, TP53-mutated AML has been identified as an important molecular subgroup with a prognosis that is arguably the worst of any. Survival beyond one year is rare after induction chemotherapy with or without consolidative allogeneic stem cell transplant. Although response rates have been improved with hypomethylating agents, outcomes remain particularly poor due to short response duration. Improvements in our understanding of AML genetics and biology have led to a surge in novel treatment options, though the clinical applicability of these agents in TP53-mutated disease remains largely unknown. This review will focus on the epidemiology, molecular characteristics, and clinical significance of TP53 mutations in AML as well as emerging treatment options that are currently being studied.

Improvement of Cardiac Vegetations in Antiphospholipid Syndrome with Enoxaparin and Corticosteroids after Rivaroxaban Failure.

Cardiac disease is a well-known complication of antiphospholipid syndrome (APS), with many patients presenting with valvular thickening or vegetations, referred to as Libman-Sacks endocarditis (LSE). Because cases of APS with cardiac involvement are relatively rare, paucity of large clinical trials studying this complication has made management challenging. In the absence of acute heart failure and embolic events, a medical approach is usually selected, consisting of anticoagulation and possibly corticosteroids when another underlying autoimmune disease is present. However, the role of various anticoagulant classes and the duration of steroid therapy continue to be debated. Here, we present a 45-year-old woman who developed two vegetations in the setting of secondary APS while taking rivaroxaban before experiencing marked improvement with the use of enoxaparin and steroids.

Advances on immunotherapy in genitourinary and renal cell carcinoma.

Genitourinary (GU) cancers are a group of epithelial malignancies associated with the organs involved in the excretion of urine. Renal cell, urothelial, and prostatic carcinoma are the overwhelming subtypes diagnosed by oncologists. Each of these was traditionally treated surgically when local and non-invasive. When these carcinomas spread, invade, or metastasize, surgical control lacks in efficacy. Chemotherapeutic regimens have been implemented for decades and have increased overall survival but many patients progress. Molecular targeting through tyrosine kinase inhibition of the vascular endothelial growth factor (VEGF) has emerged as a frontline therapy in kidney cancer with more durable responses. More recently, immunotherapy has begun to find efficacy in many other solid tumors including melanoma and non-small cell lung cancer. The inherent genetic instability of this group of cancers makes them ideal solid tumors for immune modulation. Vaccines manufactured to initiate T-Cell regulation through neoplastic-antigen presentation are available for prostate cancer and are currently on trial in renal cell carcinoma (RCC). Programmed death-1 (PD-1) and its ligand (PD-L1) are intricate members of cellular immunity against neoplastic cells. In an activated, unbound state, these molecules permit T-cell activation and cytotoxic killing of cancer cells. However, when they are linked, cellular immunity is attenuated and local cancer cells are permitted the opportunity to proliferate and invade. A novel class of monoclonal antibodies have been developed which stop PD-1 linkage and thus uncouple the 'stop' signal of these neoplastic regulatory cells. The increased overall and progression free survival have made them attractive options alone as well as in combination with anti-VEGF inhibitors for patients. Although more tolerable than chemotherapy, immunotherapeutics have adverse potential toxicities. Overall, the use of immunomodulatory medications have opened a new paradigm in the anti-neoplastic regimen of GU cancers and further developments will determine the appropriate patient to treat for optimum tumor burden eradication.

MLL fusion protein-driven AML is selectively inhibited by targeted disruption of the MLL-PAFc interaction.

MLL rearrangements are common in leukemia and considered an adverse risk factor. Through interactions with the polymerase-associated factor complex (PAFc), mixed lineage leukemia (MLL) fusion proteins activate genes critical for blocking differentiation, such as HOXA9. Here we investigate whether the MLL-PAFc interaction can be exploited therapeutically using both genetic and biochemical approaches. We tested the genetic requirement of the PAFc in acute myeloid leukemia (AML) using a conditional allele of the PAFc subunit, Cdc73. We show that the PAFc is indiscriminately necessary for the proliferation of AML cells through the epigenetic regulation of proleukemogenic target genes, such as MEIS1 and Bcl2. To investigate the therapeutic potential of targeting the MLL-PAFc interaction, we engineered a dominant negative fragment of MLL capable of binding to the PAFc. Disruption of the MLL-PAFc interaction selectively inhibits the proliferation of MLL leukemic cells without affecting cells transformed by an unrelated E2A-HLF fusion protein. Using in vivo hematopoietic reconstitution assays, we demonstrate that disruption of the MLL-PAFc does not alter normal hematopoietic stem cell function. Together, our data show a selective growth inhibition of MLL-associated leukemic cells and tolerance of normal hematopoiesis to disruption of the MLL-PAFc interaction establishing the MLL-PAFc interaction as an attractive therapeutic target.

Requirement for Dot1l in murine postnatal hematopoiesis and leukemogenesis by MLL translocation.

Disruptor of telomeric silencing 1-like (Dot1l) is a histone 3 lysine 79 methyltransferase. Studies of constitutive Dot1l knockout mice show that Dot1l is essential for embryonic development and prenatal hematopoiesis. DOT1L also interacts with translocation partners of Mixed Lineage Leukemia (MLL) gene, which is commonly translocated in human leukemia. However, the requirement of Dot1l in postnatal hematopoiesis and leukemogenesis of MLL translocation proteins has not been conclusively shown. With a conditional Dot1l knockout mouse model, we examined the consequences of Dot1l loss in postnatal hematopoiesis and MLL translocation leukemia. Deletion of Dot1l led to pancytopenia and failure of hematopoietic homeostasis, and Dot1l-deficient cells minimally reconstituted recipient bone marrow in competitive transplantation experiments. In addition, MLL-AF9 cells required Dot1l for oncogenic transformation, whereas cells with other leukemic oncogenes, such as Hoxa9/Meis1 and E2A-HLF, did not. These findings illustrate a crucial role of Dot1l in normal hematopoiesis and leukemogenesis of specific oncogenes.