Attenuated measles virus controls pediatric acute B-lineage lymphoblastic leukemia in NOD/SCID mice

Oncolytic viruses in hematological malignancies: hijacking disease biology and fostering new promises for immune and cell-based therapies

The increased tropism for malignant cells of some viruses has been highlighted in recent studies, prompting their use as a strategy to modify the transcriptional profile of those cells, while sparing the healthy ones. Likewise, they have been recognized as players modulating microenvironmental immunity, namely through an increase in antigen-presenting, natural-killer, and T CD8+ cytotoxic cells by a cross-priming mechanism elicited by tumor-associated antigens. The immunomodulatory role of the oncolytic virus seems relevant in hematological malignancies, which may relapse as a result of a proliferative burst elicited by an external stimulus in progenitor or neoplastic stem cells. By reprogramming the host cells and the surrounding environment, the potential of virotherapy ranges from the promise to eradicate the minimal measurable disease (in acute leukemia, for example), to the ex vivo purging of malignant progenitor cells in the setting of autologous bone marrow transplantation. In this review, we analyze the recent advances in virotherapy in hematological malignancies, either when administered alone or together with chemotherapeutic agents or other immunomodulators.

Oncolytic viral vectors in the era of diversified cancer therapy: from preclinical to clinical

With the in-depth research and wide application of immunotherapy recently, new therapies based on oncolytic viruses are expected to create new prospects for cancer treatment via eliminating the suppression of the immune system by tumors. Currently, an increasing number of viruses are developed and engineered, and various virus vectors based on effectively stimulating human immune system to kill tumor cells have been approved for clinical treatment. Although the virus can retard the proliferation of tumor cells, the choice of oncolytic viruses in biological cancer therapy is equally critical given their therapeutic efficacy, safety and adverse effects. Moreover, previously known oncolytic viruses have not been systematically classified. Therefore, in this review, we summarized and distinguished the characteristics of several common types of oncolytic viruses: herpes simplex virus, adenovirus, measles virus, Newcastle disease virus, reovirus and respiratory syncytial virus. Subsequently, we outlined that these oncolytic viral vectors have been transformed from preclinical studies in combination with immunotherapy, radiotherapy, chemotherapy, and nanoparticles into clinical therapeutic strategies for various advanced solid malignancies or circulatory system cancers.

Self-replicating vehicles based on negative strand RNA viruses

Self-replicating RNA viruses have been engineered as efficient expression vectors for vaccine development for infectious diseases and cancers. Moreover, self-replicating RNA viral vectors, particularly oncolytic viruses, have been applied for cancer therapy and immunotherapy. Among negative strand RNA viruses, measles viruses and rhabdoviruses have been frequently applied for vaccine development against viruses such as Chikungunya virus, Lassa virus, Ebola virus, influenza virus, HIV, Zika virus, and coronaviruses. Immunization of rodents and primates has elicited strong neutralizing antibody responses and provided protection against lethal challenges with pathogenic viruses. Several clinical trials have been conducted. Ervebo, a vaccine based on a vesicular stomatitis virus (VSV) vector has been approved for immunization of humans against Ebola virus. Different types of cancers such as brain, breast, cervical, lung, leukemia/lymphoma, ovarian, prostate, pancreatic, and melanoma, have been the targets for cancer vaccine development, cancer gene therapy, and cancer immunotherapy. Administration of measles virus and VSV vectors have demonstrated immune responses, tumor regression, and tumor eradication in various animal models. A limited number of clinical trials have shown well-tolerated treatment, good safety profiles, and dose-dependent activity in cancer patients.

Oncolytic viruses as a promising therapeutic strategy for hematological malignancies

The incidence of hematological malignancies such as multiple myeloma, leukemia, and lymphoma has increased over time. Although bone marrow transplantation, immunotherapy and chemotherapy have led to significant improvements in efficacy, poor prognosis in elderly patients, recurrence and high mortality among hematological malignancies remain major challenges, and innovative therapeutic strategies should be explored. Besides directly lyse tumor cells, oncolytic viruses can activate immune responses or be engineered to express therapeutic factors to increase antitumor efficacy, and have gradually been recognized as an appealing approach for fighting cancers. An increasing number of studies have applied oncolytic viruses in hematological malignancies and made progress. In particular, strategies combining immunotherapy and oncolytic virotherapy are emerging. Various phase I clinical trials of oncolytic reovirus with lenalidomide or programmed death 1(PD-1) immune checkpoint inhibitors in multiple myeloma are ongoing. Moreover, preclinical studies of combinations with chimeric antigen receptor T (CAR-T) cells are underway. Thus, oncolytic virotherapy is expected to be a promising approach to cure hematological malignancies. This review summarizes progress in oncolytic virus research in hematological malignancies. After briefly reviewing the development and oncolytic mechanism of oncolytic viruses, we focus on delivery methods of oncolytic viruses, especially systemic delivery that is suitable for hematological tumors. We then discuss the main types of oncolytic viruses applied for hematological malignancies and related clinical trials. In addition, we present several ways to improve the antitumor efficacy of oncolytic viruses. Finally, we discuss current challenges and provide suggestions for future studies.

Induction of Cell Death in the Human Acute Lymphoblastic Leukemia Cell Line Reh by Infection with Rotavirus Isolate Wt1-5

Cancer is a major health problem that poses a great challenge to health care systems worldwide. Tools for cancer treatment have rapidly advanced in recent years, resulting in therapeutic strategies which are alternative and complementary to conventional treatment. To identify the cell surface receptors used by a tumor cell-adapted rotavirus and the cell death markers induced by its infection, we use Wt1-5, a rotavirus isolate recently adapted to tumor cells, to infect the human acute lymphoblastic leukemia cell line, Reh. The expression of cell surface receptors used by Wt1-5 was determined using flow cytometry and an antibody blocking assay to test for their implication in virus infection. Viral antigens and cell death markers induced by rotavirus infection were followed by flow cytometric analysis. The present study showed that rotavirus Wt1-5 was able to use cell surface proteins such as heat shock proteins (HSPs) 90, 70, 60 and 40, Hsc70, PDI and integrin β3. Rotavirus Wt1-5 induced cytotoxic effects including changes in cell membrane permeability, alteration of mitochondrial membrane potential, DNA fragmentation and activation of cell death signaling. Wt1-5 deserves to be further studied as a candidate oncolytic agent due to its ability to induce apoptosis in lymphoblastic leukemia-derived cells.

Signaling lymphocytic activation molecules Slam and cancers: friends or foes?

Signaling Lymphocytic Activation Molecules (SLAM) family receptors are initially described in immune cells. These receptors recruit both activating and inhibitory SH2 domain containing proteins through their Immunoreceptor Tyrosine based Switch Motifs (ITSMs). Accumulating evidence suggest that the members of this family are intimately involved in different physiological and pathophysiological events such as regulation of immune responses and entry pathways of certain viruses. Recently, other functions of SLAM, principally in the pathophysiology of neoplastic transformations have also been deciphered. These new findings may prompt SLAM to be considered as new tumor markers, diagnostic tools or potential therapeutic targets for controlling the tumor progression. In this review, we summarize the major observations describing the implications and features of SLAM in oncology and discuss the therapeutic potential attributed to these molecules.

Potential and clinical translation of oncolytic measles viruses

INTRODUCTION

Oncolytic viruses represent a novel treatment modality that is unencumbered by the standard resistance mechanisms limiting the therapeutic efficacy of conventional antineoplastic agents. Attenuated engineered measles virus strains derived from the Edmonston vaccine lineage have undergone extensive preclinical evaluation with significant antitumor activity observed in a broad range of preclinical tumoral models. These have laid the foundation for several clinical trials in both solid and hematologic malignancies, which have demonstrated safety, biologic activity and the ability to elicit antitumor immune responses. Areas covered: This review examines the published preclinical data which supported the clinical translation of this therapeutic platform, reviews the available clinical trial data and expands on ongoing phase II testing. It also looks at approaches to optimize clinical applicability and offers future perspectives. Expert opinion: Reverse genetic engineering has allowed the generation of oncolytic MV strains retargeted to increase viral tumor specificity, or armed with therapeutic and immunomodulatory genes in order to enhance anti-tumor efficacy. Continuous efforts focusing on exploring methods to overcome resistance pathways and determining optimal combinatorial strategies will facilitate further development of this encouraging antitumor strategy.

Central nervous system acute lymphoblastic leukemia: role of natural killer cells

Central nervous system acute lymphoblastic leukemia (CNS-ALL) is a major clinical problem. Prophylactic therapy is neurotoxic, and a third of the relapses involve the CNS. Increased expression of interleukin 15 (IL-15) in leukemic blasts is associated with increased risk for CNS-ALL. Using in vivo models for CNS leukemia caused by mouse T-ALL and human xenografts of ALL cells, we demonstrate that expression of IL-15 in leukemic cells is associated with the activation of natural killer (NK) cells. This activation limits the outgrowth of leukemic cells in the periphery, but less in the CNS because NK cells are excluded from the CNS. Depletion of NK cells in NOD/SCID mice enabled combined systemic and CNS leukemia of human pre-B-ALL. The killing of human leukemia lymphoblasts by NK cells depended on the expression of the NKG2D receptor. Analysis of bone marrow (BM) diagnostic samples derived from children with subsequent CNS-ALL revealed a significantly high expression of the NKG2D and NKp44 receptors. We suggest that the CNS may be an immunologic sanctuary protected from NK-cell activity. CNS prophylactic therapy may thus be needed with emerging NK cell-based therapies against hematopoietic malignancies.