Novel Class Of Therapeutic Targets Research Articles

MicroRNAs: an emerging science in cancer epigenetics

MicroRNAs (miRNAs) are remarkable molecules that appear to have a fundamental role in the biology of the cell. They constitute a class of non-protein encoding RNA molecules which have now emerged as key players in regulating the activity of mRNA. miRNAs are small RNAmolecules around 22 nucleotides in length, which affect the activity of specific mRNA, directly degrading it and/or preventing its translation into protein. The science of miRNAs holds them as candidate biomarkers for the early detection and management of cancer. There is also considerable excitement for the use of miRNAs as a novel class of therapeutic targets and as a new class of therapeutic agents for the treatment of cancers. From a clinical perspective, miRNAs can induce a number of effects and may have a diverse application in biomedical research. This review highlights the general mode of action of miRNAs, their biogenesis, the effect of diet on miRNA expression and the impact of miRNAs on cancer epigenetics and drug resistance in various cancers. Further we also provide emphasis on bioinformatics software which can be used to determine potential targets of miRNAs.

Suppressor of Cytokine Signaling (SOCS) Molecules Are Critical to Balance Oncogenic Signaling Strength in Ph+ ALL.

AbstractAbstract 2563 Background:SOCS (suppressors of cytokine signaling) are a family of intracellular proteins, including SOCS1–7 and CISH (cytokine induced SH2 domain protein). They play key roles in negative regulation of cytokine signal transduction, including JAK/STAT pathway. While BCR-ABL1 signaling involves STAT5 in Ph+ acute lymphoblastic leukemia (ALL) cells, STAT5 signaling also results in its own feedback inhibition via CISH, SOCS2 and SOCS3. Interestingly, CISH, SOCS2 and SOCS3 are highly expressed in Ph+ALL and represent the focus of this study. Results:Comparing microarray data for human Ph+ ALL (n=15) and normal human pre-B cells (n=8), we found that mRNA levels of SOCS2 and CISH were 10-fold (p<0.0001) and 3-fold (p<0.0001) upregulated in Ph+ ALL cells compared to normal pre-B cells respectively. As measured by qRT-PCR and Western blot, TKI-treatment rapidly decreased the expression of SOCS2, SOCC3 and CISH in Ph+ALL cells, indicating that high expression levels of CISH, SOCS2 and SOCS3 are induced by tyrosine kinase activity. These findings suggest that high levels of CISH/SOCS inhibitors represent a novel aspect of a leukemia-specific gene expression pattern. Importantly, we found that high expression levels of SOCS2 and CISH are predictive of poor outcome in two clinical trials for patients with ALL. In the COG trial (P9906; n=207) for children with high-risk ALL, we found that patients with minimal residual disease (MRD) findings on day 29 had 4- to 7-fold higher mRNA levels of SOCS2, SOCS3 or CISH (n=207; p=0.004), and patients with high expression of SOCS2, SOCS3 or CISH had decreased overall survival rate (p=0.009) and relapse free survival rate (p=0.011) compared to patients with low expression of SOCS2, SOCS3 or CISH. These results collectively indicate that inhibitory signaling from CISH/SOCS2/SOCS3 molecules contributes to the course of disease of human Ph+ALL.To study the function of SOCS2, SOCS3 and CISH in genetic experiments, we transformed pre-B cells from mutant mice. For inducible deletion of Socs3 and Cish, pre-B cells from Socs3fl/fl or Cishfl/fl mice were transformed by BCR-ABL1 and gene deletion was induced by 4-OHT-mediated activation of Cre recombinase. Inducible deletion of Socs3 or Cish resulted in upregulation of p-STAT5, increased ROS (reactive oxygen species), accumulation of Arf, p53 and p21, cellular senescence and subsequent cell death of leukemia cells. Studying BCR-ABL1 transformed Cishfl/fl ALL cells in vivo, we found that genetic deletion of Cish resulted in rapid leukemia regression and prolonged survival of recipient NOD-SCID mice (13 days vs 30 days; n=7; p<0.001). To study the role of Socs2 in Ph+ ALL, pre-B cells from SOCS2−/− and wildtype mice were transformed by BCR-ABL1. Compared to wildtype ALL cells, SOCS2−/− ALL cells had upregulated p-STAT5 and increased ROS, formed 6-fold fewer colonies in methyl cellulose, underwent G0/G1 cell cycle arrest and cellular senescence. Interestingly, similar observations were made, when a constitutively active mutant of STAT5 (Stat5CA) was expressed in Ph+ ALL cells. Stat5CA leukemia cells underwent apoptosis within 3 days, which indicates that excessively high levels of STAT5 signaling are toxic to Ph+ALL cells. Conclusion:These results indicate that SOCS family members are critical negative regulators of oncogenic signaling strength in BCR-ABL1 ALL. These findings are of particular relevance, because they identify SOCS molecules as members of a fundamentally novel class of therapeutic targets. The concept of pharmacological perturbation of oncogenic signaling equilibrium in leukemia cells by inhibition (e.g. TKI-treatment) or exaggeration of signaling strength (e.g. blockade of SOCS molecules) may lead to the discovery of multiple additional therapeutic targets and broaden our repertoire of currently available pathways for therapeutic intervention. Disclosures:No relevant conflicts of interest to declare.

ITIM-Containing Inhibitory Receptors Are Required to Balance Oncogenic Signaling Strength in Ph+ ALL

Abstract 291▪▪This icon denotes a clinically relevant abstract Background:ITIM (immunoreceptor tyrosine-based inhibition motifs) motifs in the cytoplasmic tail of inhibitory receptors recruit inhibitory phosphatases. Upon ligation, these phosphatases inhibit signal transduction from tyrosine kinases including BCR-ABL1. ITIM-receptors are critical in the control of immune responses of B and T cells. Surprisingly, we found that a number of inhibitory ITIM-receptors are expressed at very high levels on the surface of patient-derived Ph+ acute lymphoblastic leukemia (ALL) cells compared to normal pre-B cells. In this study, three central ITIM-receptors were identified and analyzed for their function in Ph+ALL: PECAM1 (platelet/endothelial cell adhesion molecule 1/CD31), CD300A and LAIR1 (leukocyte-associated immunoglobulin-like receptor 1). Results:Microarray data showed mRNA levels of PECAM1, CD300A and LAIR1 were about 5-fold higher (p<0.005) in Ph+ ALL (n=15) than normal human pre-B cells (n=8). We confirmed this difference at the protein level by flow cytometry studying patient-derived Ph+ALL (n=11) and pre-B cells from normal bone marrow samples (n=2).These findings seem counterintuitive because signaling from these receptors would attenuate the signaling strength downstream of BCR-ABL1. Importantly, we found that high expression levels of ITIM-receptors are predictive of poor outcome in two clinical trials. In the COG trial (P9906; n=207) for children with high-risk ALL, we found that mRNA levels of PECAM1, CD300A and LAIR1 at diagnosis positively correlated with early minimal residual disease (MRD) findings on day 29 (p<0.0005), and negatively correlated with overall survival (OS) rate (p<0.02) or relapse free survival (RFS) rate (p<0.05). In ECOG trial E2993 for adults with ALL (n=215), we found that PECAM1 mRNA level in ALL patients negatively correlated with OS rate (p=0.0285). These results collectively indicate that inhibitory ITIM-receptors contribute to the course of human ALL disease.To study the role of PECAM1, CD300A and LAIR1 in Ph+ ALL in genetic experiments, we transformed pre-B cells from Pecam1−/−, Cd300a−/− and wildtype mice with BCR-ABL1. Compared to wildtype ALL cells, Pecam1−/− or Cd300a−/− ALL cells showed increased ROS levels. Consistent with higher levels of ROS, the Pecam1−/− and Cd300a−/− ALL cells accumulate p53, p21 and p27 protein, are prone to G0/G1cell cycle arrest and cellular senescence. Colony forming assays revealed that Pecam1- and cd300-deficient leukemia cells also formed 10-fold fewer colonies in methyl cellulose compared to wildtype ALL cells (p<0.0001). For Lair1, we performed genetic loss-of-function experiments by inducible activation of Cre in Lair1fl/fl leukemia cells. Inducible deletion of Lair1 resulted in drastic upregulation of ROS, accumulation of Arf, p53 and p21, cellular senescence and subsequent leukemia cell death. Transplanting Lair1fl/fl ALL cells into NOD-SCID mice, we found that Lair1 deletion resulted in rapid leukemia regression and prolonged survival of recipient mice. Leukemia cell death caused by Lair1 deletion could be rescued by overexpression of the inhibitory phosphatase Ptpn6 (SHP1) indicating that the protective effect of the Lair1 is indeed mediated by ITIM-based recruitment of inhibitory phosphatases. To test whether these findings are also relevant to other subtypes of ALL, we used a model for NRASG12D-driven ALL. BCR-ABL1 (∼25%) and NRAS lesions (∼30%) account for more than half of cases of ALL. Consistent with our findings with BCR-ABL1, NRASG12D Pecam1−/−, Cd300a−/−leukemia cells were prone to G0/G1 cell cycle arrest and cellular senescence (p<0.01). Conclusion:These results indicated that inhibitory ITIM-receptors are critical regulators of oncogenic signaling strength in BCR-ABL1 and NRAS-driven ALL. Deficiency of ITIM-receptor signaling can be rescued by overexpression of the PTPN6 phosphatase. These findings are of particular relevance, because they identify ITIM-receptors and inhibitory phosphatases as members of a fundamentally novel class of therapeutic targets. The concept of pharmacological perturbance of oncogenic signaling equilibrium in leukemia cells by inhibition (e.g. TKI-treatment) or exaggeration of signaling strength (e.g. blockade of ITIM-receptors) may lead to the discovery of multiple additional therapeutic targets and broaden our repertoire of currently available pathways for therapeutic intervention. Disclosures:No relevant conflicts of interest to declare.

ROR1 and ROR2 in Human Malignancies: Potentials for Targeted Therapy

Targeted therapies require cellular protein expression that meets specific requirements that will maximize effectiveness, minimize off-target toxicities, and provide an opportunity for a therapeutic effect. The receptor tyrosine kinase-like orphan receptors (ROR) are possible targets for therapy that may meet such requirements. RORs are transmembrane proteins that are part of the receptor tyrosine kinase (RTK) family. The RORs have been shown to play a role in tumor-like behavior, such as cell migration and cell invasiveness and are normally not expressed in normal adult tissue. As part of the large effort in target discovery, ROR proteins have recently been found to be expressed in human cancers. Their unique expression profiles may provide a novel class of therapeutic targets for small molecules against the kinase or for antibody-based therapies against these receptors. Being restricted on tumor cells and not on most normal tissues, RORs are excellent targets for the treatment of minimal residual disease, the final hurdle in the curative approach to many cancers, including solid tumors such as neuroblastoma. In this review, we summarize the biology of RORs as they relate to human cancer, and highlight the therapeutic approaches directed toward them.

Little things on which happiness depends: microRNAs as novel therapeutic targets for the treatment of anxiety and depression

Anxiety and depression are devastating mental illnesses that are a significant public health concern. Selective serotonin-reuptake inhibitors are the first-line treatment strategy for these disorders, which despite being a significant advantage over older treatments, are hampered by a limited efficacy in a significant subset of patients, delayed onset of action and side effects that affect compliance. Thus, there is much impetus to develop novel therapeutic strategies. However, this goal can only be rationally realised with a better understanding of the molecular pathophysiology of these disorders. MicroRNAs (miRNAs) are a newly discovered class of gene-expression regulators that may represent a novel class of therapeutic targets to treat a variety of disorders including psychiatric diseases. miRNAs are heavily involved in regulating many physiological processes including those fundamental to the functioning of the central nervous system. Evidence collected to date has already demonstrated that miRNA-expression levels are altered in patients suffering from depression and anxiety and in pre-clinical models of psychological stress. Furthermore, increasing evidence suggests that psychoactive agents including antidepressants and mood stabilisers utilise miRNAs as downstream effectors. Altering miRNA levels has been shown to alter behaviour in a therapeutically desirable manner in pre-clinical models. This review aims to outline the evidence collected to date demonstrating miRNAs role in anxiety and depression, the potential advantages of targeting these small RNA molecules as well as some of the hurdles that will have to be overcome to fully exploit their therapeutic potential.

Enzymatic Characterisation of USP7 Deubiquitinating activity and Inhibition

USP7 (HAUSP) is a deubiquitinating enzyme, which plays a crucial role in regulating the levels of the p53 tumour suppressor protein, through its ability to prevent the proteasomal degradation of the Ubiquitin ligase for p53, Hdm2. Supporting evidence suggests that an inhibitor of USP7 would act to abrogate the action of Hdm2, and thereby elevate levels of the p53 protein, with associated therapeutic benefits in cancer and potentially other diseases. In this article, we describe the characterisation of differential enzyme activity of both the full length and putative catalytic domain of human USP7 expressed in both bacterial and insect cell expression systems. We also demonstrate the way in which variations in the reducing environment surrounding the enzyme can dramatically affect both the stability of the enzyme and the range of small molecules able to inhibit the catalytic activity of the enzyme. Furthermore, we describe the validation and use of this assay for a high-throughput screening approach, again highlighting the critical nature of the enzyme's environment. Taken together, these findings not only increase our understanding of the enzymatic activity of deubiquitinating enzymes, but also highlight several key considerations of importance in the development of therapeutic agents against this novel class of therapeutic targets.

MicroRNA in central nervous system trauma and degenerative disorders

MicroRNAs (miRNAs) are a novel class of small noncoding RNAs that negatively regulate gene expression at the posttranscriptional level by binding to the 3'-untranslated region of target mRNAs leading to their translational inhibition or sometimes degradation. MiRNAs are predicted to control the activity of at least 20-30% of human protein-coding genes. Recent studies have demonstrated that miRNAs are highly expressed in the central nervous system (CNS) including the brain and spinal cord. Although we are currently in the initial stages of understanding how this novel class of gene regulators is involved in neurological biological functions, a growing body of exciting evidence suggests that miRNAs are important regulators of diverse biological processes such as cell differentiation, growth, proliferation, and apoptosis. Moreover, miRNAs are key modulators of both CNS development and plasticity. Some miRNAs have been implicated in several neurological disorders such as traumatic CNS injuries and neurodegenerative diseases. Recently, several studies suggested the possibility of miRNA involvement in neurodegeneration. Identifying the roles of miRNAs and their target genes and signaling pathways in neurological disorders will be critical for future research. miRNAs may represent a new layer of regulators for neurobiology and a novel class of therapeutic targets for neurological diseases.

Inhibition of metastasis development by daily administration of ultralow doses of RNase A and DNase I

Recent data on the involvement of miRNA and circulating tumor-derived DNA in regulation of tumorigenesis showed a great prospect for these molecules as a novel class of therapeutic targets and gave a new start for the study of enzymes cleaving nucleic acids as potential antitumor and antimetastatic agents. In the present paper using two murine tumor models with pulmonary or liver metastases we studied the antimetastatic potential of RNase A and DNase I and performed a search for possible molecular targets of the enzymes. Herein, we show for the first time that daily administration of ultralow doses of RNase A (0.5–50 μg/kg) and DNase I (0.02–2.3 mg/kg) inhibits the development of metastasis to 60–90% and RNase A exerts 30% retardation of tumor growth. Remarkably, the increase in RNase A dose from 50 μg/kg to 10 mg/kg leads to a disappearance of antitumor and antimetastatic effects. Simultaneous treatment of tumor-bearing animals with RNase A and DNase I leads to an additive effect and results in almost total absence of metastases. The use of RNase A as an adjuvant in conjunction with conventional cytostatic cyclophosphamide results in a reliable enhancement of antitumor and antimetastatic effect of the therapy compared with the use of these agents individually. The search for possible molecular mechanism of antimetastatic effect of nucleases showed that daily administration of the enzymes reduced the pathologically increased level of extracellular nucleic acids and increased nuclease activity of the blood plasma of tumor-bearing mice back to the level of healthy animals. Thus, we unequivocally show that the proposed protocol of treatment of tumor-bearing animals with RNase A and DNase I has a general systemic and immunomodulatory effect, leads to a drastic suppression of metastasis development, and in perspective may become an effective component of intensive complex therapy of cancer.

MicroRNAs in colorectal cancer: translation of molecular biology into clinical application

MicroRNAs (miRNAs) are small non-coding RNAs 18-25 nucleotides in length that downregulate gene expression during various crucial cell processes such as apoptosis, differentiation and development. Changes in the expression profiles of miRNAs have been observed in a variety of human tumors, including colorectal cancer (CRC). Functional studies indicate that miRNAs act as tumor suppressors and oncogenes. These findings significantly extend Vogelstein's model of CRC pathogenesis and have shown great potential for miRNAs as a novel class of therapeutic targets. Several investigations have also described the ability of miRNA expression profiles to predict prognosis and response to selected treatments in CRC patients, and support diagnosis of CRC among cancer of unknown primary site. miRNAs' occurrence has been repeatedly observed also in serum and plasma, and miRNAs as novel minimally invasive biomarkers have indicated reasonable sensitivity for CRC detection and compare favorably with the fecal occult blood test. In this review, we summarize the knowledge regarding miRNAs' functioning in CRC while emphasizing their significance in pathogenetic signaling pathways and their potential to serve as disease biomarkers and novel therapeutic targets.

MicroRNA: An emerging therapeutic target and intervention tool.

MicroRNAs (miRNAs) are a class of short non-coding RNAs with posttranscriptional regulatory functions. To date, more than 600 human miRNAs have been experimentally identified, and estimated to regulate more than one third of cellular messenger RNAs. Accumulating evidence has linked the dysregulated expression patterns of miRNAs to a variety of diseases, such as cancer, neurodegenerative diseases, cardiovascular diseases and viral infections. MiRNAs provide its particular layer of network for gene regulation, thus possessing the great potential both as a novel class of therapeutic targets and as a powerful intervention tool. In this regard, synthetic RNAs that contain the binding sites of miRNA have been shown to work as a “decoy” or “miRNA sponge” to inhibit the function of specific miRNAs. On the other hand, miRNA expression vectors have been used to restore or overexpress specific miRNAs to achieve a long-term effect. Further, double-stranded miRNA mimetics for transient replacement have been experimentally validated. Endogenous precursor miRNAs have also been used as scaffolds for the induction of RNA interference. This article reviews the recent progress on this emerging technology as a powerful tool for gene regulation studies and particularly as a rationale strategy for design of therapeutics.

MicroRNAs: role in cardiovascular biology and disease

miRNAs (microRNAs) comprise a novel class of endogenous, small, non-coding RNAs that negatively regulate gene expression via degradation or translational inhibition of their target mRNAs. Recent studies have demonstrated that miRNAs are highly expressed in the cardiovascular system. Although we are currently in the initial stages of understanding how this novel class of gene regulators is involved in cardiovascular biological functions, a growing body of exciting evidence suggests that miRNAs are important regulators of cardiovascular cell differentiation, growth, proliferation and apoptosis. Moreover, miRNAs are key modulators of both cardiovascular development and angiogenesis. Consequently, dysregulation of miRNA function may lead to cardiovascular diseases. Indeed, several recent reports have demonstrated that miRNAs are aberrantly expressed in diseased hearts and vessels. Modulating these aberrantly expressed miRNAs has significant effects on cardiac hypertrophy, vascular neointimal lesion formation and cardiac arrhythmias. Identifying the roles of miRNAs and their target genes and signalling pathways in cardiovascular disease will be critical for future research. miRNAs may represent a new layer of regulators for cardiovascular biology and a novel class of therapeutic targets for cardiovascular diseases.