In Vitro Characterization of Valproic Acid, ATRA, and Cytarabine Used for Disease-Stabilization in Human Acute Myeloid Leukemia: Antiproliferative Effects of Drugs on Endothelial and Osteoblastic Cells and Altered Release of Angioregulatory Mediators by Endothelial Cells

Therapeutic Use of Valproic Acid and All-Trans Retinoic Acid in Acute Myeloid Leukemia-Literature Review and Discussion of Possible Use in Relapse after Allogeneic Stem Cell Transplantation

Even though allogeneic stem cell transplantation is the most intensive treatment for acute myeloid leukemia (AML), chemo-resistant leukemia relapse is still one of the most common causes of death for these patients, as is transplant-related mortality, i.e., graft versus host disease, infections, and organ damage. These relapse patients are not always candidates for additional intensive therapy or re-transplantation, and many of them have decreased quality of life and shortened expected survival. The efficiency of azacitidine for treatment of posttransplant AML relapse has been documented in several clinical trials. Valproic acid is an antiepileptic fatty acid that exerts antileukemic activity through histone deacetylase inhibition. The combination of valproic acid and all-trans retinoic acid (ATRA) is well tolerated even by unfit or elderly AML patients, and low-toxicity chemotherapy (e.g., azacitidine) can be added to this combination. The triple combination of azacitidine, valproic acid, and ATRA may therefore represent a low-intensity and low-toxicity alternative for these patients. In the present review, we review and discuss the general experience with valproic acid/ATRA in AML therapy and we discuss its possible use in low-intensity/toxicity treatment of post-allotransplant AML relapse. Our discussion is further illustrated by four case reports where combined treatments with sequential azacitidine/hydroxyurea, valproic acid, and ATRA were used.

The Constitutive Extracellular Protein Release by Acute Myeloid Leukemia Cells-A Proteomic Study of Patient Heterogeneity and Its Modulation by Mesenchymal Stromal Cells

Simple Summary

The formation of normal blood cells in the bone marrow is supported by a network of non-hematopoietic cells including connective tissue cells, blood vessel cells and bone-forming cells. These cell types support and regulate the growth of acute myeloid leukemia (AML) cells and communicate with leukemic cells through the release of proteins to their common extracellular microenvironment. One of the AML-supporting normal cell types is a subset of connective tissue cells called mesenchymal stem cells. In the present study, we observed that AML cells release a wide range of diverse proteins into their microenvironment, but patients differ both with regard to the number and amount of released proteins. Inhibition of this bidirectional communication through protein release between AML cells and leukemia-supporting normal cells may become a new strategy for cancer treatment.

Abstract

Extracellular protein release is important both for the formation of extracellular matrix and for communication between cells. We investigated the extracellular protein release by in vitro cultured normal mesenchymal stem cells (MSCs) and by primary human acute myeloid leukemia (AML) cells derived from 40 consecutive patients. We observed quantifiable levels of 3082 proteins in our study; for the MSCs, we detected 1446 proteins, whereas the number of released proteins for the AML cells showed wide variation between patients (average number 1699, range 557–2380). The proteins were derived from various cellular compartments (e.g., cell membrane, nucleus, and cytoplasms), several organelles (e.g., cytoskeleton, endoplasmatic reticulum, Golgi apparatus, and mitochondria) and had various functions (e.g., extracellular matrix and exosomal proteins, cytokines, soluble adhesion molecules, protein synthesis, post-transcriptional modulation, RNA binding, and ribonuclear proteins). Thus, AML patients were very heterogeneous both regarding the number of proteins and the nature of their extracellularly released proteins. The protein release profiles of MSCs and primary AML cells show a considerable overlap, but a minority of the proteins are released only or mainly by the MSC, including several extracellular matrix molecules. Taken together, our observations suggest that the protein profile of the extracellular bone marrow microenvironment differs between AML patients, these differences are mainly caused by the protein release by the leukemic cells but this leukemia-associated heterogeneity of the overall extracellular protein profile is modulated by the constitutive protein release by normal MSCs.

Randomized phase II study of valproic acid in combination with bevacizumab and oxaliplatin/fluoropyrimidine regimens in patients with RAS-mutated metastatic colorectal cancer: the REVOLUTION study protocol

Background

Despite effective treatments, metastatic colorectal cancer (mCRC) prognosis is still poor, mostly in RAS-mutated tumors, thus suggesting the need for novel combinatorial therapies. Epigenetic alterations play an important role in initiation and progression of cancers, including CRC. Histone-deacetylase inhibitors (HDACi) have shown activity in combination with chemotherapy in the treatment of solid tumors. Owing to its HDACi activity and its safe use for epileptic disorders, valproic acid (VPA) is a good candidate for anticancer therapy that we have largely explored preclinically translating our findings in currently ongoing clinical studies. We have shown in CRC models that HDACi, including VPA, induces synergistic antitumor effects in combination with fluoropyrimidines. Furthermore, unpublished results from our group demonstrated that VPA induces differentiation and sensitization of CRC stem cells to oxaliplatin. Moreover, preclinical and clinical data suggest that HDACi may prevent/reverse anti-angiogenic resistance.

Methods/Design

A randomized, open-label, two-arm, multicenter phase-II study will be performed to explore whether the addition of VPA to first line bevacizumab/oxaliplatin/fluoropyrimidine regimens (mFOLFOX-6/mOXXEL) might improve progression-free survival (PFS) in RAS-mutated mCRC patients. A sample size of 200 patients was calculated under the hypothesis that the addition of VPA to chemotherapy/bevacizumab can improve PFS from 9 to 12 months, with one-sided alpha of 0.20 and a power of 0.80. Secondary endpoints are overall survival, objective response rate, metastases resection rate, toxicity, and quality of life. Moreover, the study will explore several prognostic and predictive biomarkers on blood samples, primary tumors, and on resected metastases.

Discussion

The "Revolution" study aims to improve the treatment efficacy of RAS-mutated mCRC through an attractive strategy evaluating the combination of VPA with standard cancer treatment. Correlative studies could identify novel biomarkers and could add new insight in the mechanism of interaction between VPA, fluoropyrimidine, oxaliplatin, and bevacizumab.

Trial Registration

EudraCT: 2018-001414-15; ClinicalTrials.gov identifier: NCT04310176.

The association between haemorrhage and markers of endothelial insufficiency and inflammation in patients with hypoproliferative thrombocytopenia: a cohort study

In daily haematological practice, predicting bleeding in thrombocytopenic patients is difficult, and clinicians adhere to transfusion triggers to guide patients through the aplastic phase of chemotherapy. Platelet count is not the only determinant of bleeding and additional mechanisms for impending haemostasis are likely. Beside clot formation, platelets are essential for the maintenance of integrity of vascular beds. We therefore prospectively investigated associations between biomarkers for endothelial damage (urine albumin excretion) and inflammation (C‐reactive protein) and bleeding (WHO grading) in 88 patients with 116 on‐protocol episodes. We found an increase in grade 2 bleeding with a higher urine albumin/creatinine ratio one day after the measurement [odds ratio (OR) 1·24 for every doubling of the ratio, 95% CI 1·05–1·46, P‐value 0·01] and a 29% increase in the odds of grade 2 bleeding for every doubling of serum C‐reactive protein (CRP) (95% CI 1·04–1·60, P‐value 0·02) after correction for morning platelet count. The 24 h post‐transfusion corrected count increment (CCI₂₄) showed a significant association with these biomarkers: increasing urine albumin/creatinine ratio and CRP were associated with lower CCI_24. We report two inexpensive and easy‐to‐apply biomarkers that could be useful in designing a prediction model for bleeding risk in thrombocytopenic patients.

Valproic Acid Induces Endothelial-to-Mesenchymal Transition-Like Phenotypic Switching

Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, is a widely used anticonvulsant drug that is currently undergoing clinical evaluation for anticancer therapy due to its anti-angiogenic potential. Endothelial cells (ECs) can transition into mesenchymal cells and this form of EC plasticity is called endothelial-to-mesenchymal transition (EndMT), which is widely implicated in several pathologies including cancer and organ fibrosis. However, the effect of VPA on EC plasticity and EndMT remains completely unknown. We report herein that VPA-treatment significantly inhibits tube formation, migration, nitric oxide production, proliferation and migration in ECs. A microscopic evaluation revealed, and qPCR, immunofluorescence and immunoblotting data confirmed EndMT-like phenotypic switching as well as an increased expression of pro-fibrotic genes in VPA-treated ECs. Furthermore, our data confirmed important and regulatory role played by TGFβ-signaling in VPA-induced EndMT. Our qPCR array data performed for 84 endothelial genes further supported our findings and demonstrated 28 significantly and differentially regulated genes mainly implicated in angiogenesis, endothelial function, EndMT and fibrosis. We, for the first time report that VPA-treatment associated EndMT contributes to the VPA-associated loss of endothelial function. Our data also suggest that VPA based therapeutics may exacerbate endothelial dysfunction and EndMT-related phenotype in patients undergoing anticonvulsant or anticancer therapy, warranting further investigation.

TLE4 regulation of wnt-mediated inflammation underlies its role as a tumor suppressor in myeloid leukemia

The presence of AML1-ETO (RUNX1-CBF2T1), a fusion oncoprotein resulting from a t(8;21) chromosomal translocation, has been implicated as a necessary but insufficient event in the development of a subset of acute myeloid leukemias (AML). While AML1-ETO prolongs survival and inhibits differentiation of hematopoietic stem cells (HSC), other contributory events are needed for cell proliferation and leukemogenesis. We have postulated that specific tumor suppressor genes keep the leukemic potential of AML1-ETO in check. In studying del(9q), one of the most common concomitant chromosomal abnormalities with t(8;21), we identified the loss of an apparent tumor suppressor, TLE4, that appears to cooperate with AML1-ETO to confer a leukemic phenotype. This study sought to identify the molecular basis of this cooperation. We show that the loss of TLE4 confers proliferative advantage to leukemic cells, simultaneous with an upregulation of a pro- inflammatory signature mediated through aberrant increases in Wnt signaling activity. We further demonstrate that inhibition of cyclooxygenase (COX) activity partly reverses the pro-leukemic phenotype due to TLE4 knockdown, pointing towards a novel therapeutic approach for myeloid leukemia.

The progress of angiogenic factors in the development of leukemias

Angiogenic factors have been demonstrated to play important roles in modulating angiogenesis of solid tumors. Recently, accumulating studies extensively indicated that some angiogenic factors widely exist in malignant cells of hematologic malignancy, which regulated the expression of a number of genes that were involved in abnormal proliferation, differentiation and apoptosis of these cells. With deep research of angiogenic factors, its expression, function and regulatory mechanism were gradually elucidated, and some of them were related to the development and prognosis of leukemia, or provide more possible strategies for treatment of patients with leukemia. Herein, we summarize the progress in study of some important angiogenic factors and hematological malignancies.