Antisense therapy in malignant diseases: status quo and quo vadis?

Antisense oligonucleotides-based approaches for the treatment of multiple myeloma

Multiple myeloma (MM), a hematological malignancy which affects the monoclonal plasma cells in the bone marrow, is in rising incidence around the world, accounting for approximately 2 % of newly diagnosed cancer cases in the US, Australia, and Western Europe. Despite the progress made in the last few years in the available therapeutic options (e.g. proteasome inhibitors, immunomodulatory drugs, tumor cell-targeting monoclonal antibodies, autologous stem cell transplantation, etc.), multiple myeloma is still regarded as incurable, and the prognosis for most patients is poor, as the disease becomes refractory to treatment throughout time. Antisense oligonucleotides (ASOs), designed to be complementary to selected messenger RNA (mRNA) sequences of specific genes involved in the pathogenesis of multiple myeloma (e.g. Bcl-2, Mcl-1, STAT3, IRF4, IL6, ILF2, HK2, c-MYC, etc.), represent a promising alternative to conventional treatments, and can be tailored according to the individual requirements of each patient. The main goal of antisense therapy for multiple myeloma consists in silencing the specific genes participating in the proliferation and survival of tumor cells via RNA cleavage or RNA blockage, thus preventing mRNA interactions with ribosomes and altering the process of protein translation. So far, pre-clinical and clinical studies showed promising results when Bcl-2 (Genasense), Mcl-1 (ISIS2048), STAT3 (ISIS345794) and IRF4 (ION251) were targeted using ASOs-based formulations. However, FDA approval has not been obtained yet for these products, mainly due to ethical and financial issues posed by customized therapies and insufficient information regarding their long-term toxicity. This review aims to provide a comprehensive insight into antisense oligonucleotides-based therapies, their potential chemical modifications, the mechanisms involved in ASOs-mediated gene silencing, potential systems for ASOs delivery, and the applications of ASOs in the treatment of multiple myeloma. The relevant genetic targets in ASOs-based MM therapies were described, and the research results obtained in the studies conducted so far were analyzed, with a focus on the ASOs formulations that were already included in clinical trials. In the end, current challenges, and future perspectives of antisense therapy for MM were also discussed.

A novel nonviral gene delivery system: multifunctional envelope-type nano device

In this review we introduce a new concept for developing a nonviral gene delivery system which we call "Programmed Packaging." Based on this concept, we succeeded in developing a multifunctional envelope-type nano device (MEND), which exerts high transfection activities equivalent to those of an adenovirus in a dividing cell. The use of MEND has been extended to in vivo applications. PEG/peptide/DOPE ternary conjugate (PPD)-MEND, a new in vivo gene delivery system for the targeting of tumor cells that dissociates surface-modified PEG in tumor tissue by matrix metalloproteinase (MMP) and exerts significant transfection activities, was developed. In parallel with the development of MEND, a quantitative gene delivery system, Confocal Image-assisted 3-dimensionally integrated quantification (CIDIQ), also was developed. This method identified the rate-limiting step of the nonviral gene delivery system by comparing it with adenoviral-mediated gene delivery. The results of this analysis provide a new direction for the development of rational nonviral gene delivery systems.

Cyproheptadine-induced myeloma cell apoptosis is associated with inhibition of the PI3K/AKT signaling

Recent studies revealed that the anti-allergic cyproheptadine displays anti-blood cancer activity. However, its mechanism is still elusive. In this study, cyproheptadine was found to decrease the expression of anti-apoptotic proteins, including Bcl-2, Mcl-1, and XIAP. More importantly, cyproheptadine-induced apoptosis was accompanied by suppressing AKT activation in myeloma cells. In the subsequent study, cyproheptadine was found to inhibit insulin-like growth factor 1-triggered AKT activation in a time- and concentration-dependent manner. Specifically, cyproheptadine blocked AKT translocation from nuclei for phosphorylation. This inhibition led to suppressed activation of p70S6K and 4EBP1, two key downstream signaling proteins in the PI3K/AKT pathway. However, cyproheptadine did not display inhibition on activation of IGF-1R or STAT3, possible upstream signals of AKT activation. These results further demonstrated that cyproheptadine suppresses the PI3K/AKT signaling pathway, which is probably critical for cyproheptadine-induced MM cell apoptosis.

Use of RNA in drug design

This is a review of RNA as a target for small molecules (ribosomes, riboswitches, regulatory RNAs) and RNA-derived oligonucleotides as tools (antisense/small interfering RNA, ribozymes, aptamers/decoy RNA and microRNA). This review highlights the present state of research using RNA as a drug target or as a potential drug candidate and explains at which stage and to what extent rational design could eventually be involved. Special attention has been paid to the recent potential clinical applications of RNA either as drugs or drug targets. The review deals mainly with mechanistic approaches rather than with physicochemical or computational aspects of RNA-based drug design.

Targeting inhibitor of apoptosis proteins for therapeutic intervention

The inhibitors of apoptosis (IAP) proteins have emerged over the last decade as important targets for therapeutic intervention in human malignancies. Overexpression of IAPs has been implicated in cell survival and resistance against stress-induced apoptosis brought on by radiation and/or chemotherapeutics (currently the standard-of-care in a variety of different cancer diseases). In addition, evasion from death receptor-mediated apoptosis and regulation of NF-κB pathways and cell division have also been associated with IAP proteins. Efforts to target IAP proteins in tumors have focused mainly on designing small molecules that mimic the IAP-binding motif of the endogenous IAP antagonist, second mitochondrial activator of caspases. In addition, several other IAP-targeting strategies, including antisense oligonucleotides and transcriptional repression, have also been initiated, with the hope of providing therapeutic benefit to cancer patients.

Biodistribution of antisense nanoparticles in mammary carcinoma rat model

Efficient and specific delivery of antisenses (ASs) and protection of the sequences from degradation are critical factors for effective therapy. Sustained release nanoparticles (NP) offer increased resistance to nuclease degradation, increased amounts of AS uptake, and the possibility of control in dosing and sustained duration of AS administration. The biodegradable and biocompatible poly(D,L-lactic-co-glycolic acid) copolymer (PLGA) was utilized to encapsulate AS directed against osteopontin (OPN), which is a promising therapeutic target in mammary carcinoma. Whole body biodistribution of OPN AS NP was evaluated in comparison to naked AS, in intact and mammary carcinoma metastasis model bearing rats. Naked and NP encapsulated AS exhibited different biodistribution profiles. AS NP, in contrast to naked AS, tended to accumulate mostly in the spleen, liver, and at the tumor inoculation site. Drug levels in intact organs were negligible. The elimination of naked AS was faster, due to rapid degradation of the unprotected sequence. It is concluded that AS NP protect the AS from degradation, provide efficient AS delivery to the tumor tissue, and minimize AS accumulation in intact organs due to the AS sustained release profile as well as the favorable NP physicochemical properties.

Transferrin receptor-targeted liposomes encapsulating anti-BCR-ABL siRNA or asODN for chronic myeloid leukemia treatment

The present work aimed at the development and application of transferrin receptor (TrfR)-targeted sterically stabilized liposomes encapsulating anti-BCR-ABL siRNA or asODN. Transferrin was coupled to the surface of liposomes encapsulating siRNA or asODN through the postinsertion method. Cell association and internalization were assessed by flow cytometry and confocal microscopy, respectively. BCR-ABL mRNA and Bcr-Abl protein levels were evaluated by qRT-PCR and Western blot, respectively. Cell viability was assessed using the resazurin reduction method. The amount of coupled transferrin and the size and stability over time of the liposomes were very satisfactory and reproducible. The siRNA encapsulation yield was dependent on the concentration of the encapsulation buffer used (20 or 300 mM), as opposed to asODN encapsulation yield which was high for both concentrations tested. Cell association and internalization studies were performed in leukemia cell lines treated with liposomes coupled to Trf (Trf-liposomes) or albumin (BSA-liposomes) or with nontargeted liposomes (NT-liposomes) encapsulating fluorescently labeled siRNA (Cy3-siRNA). These experiments clearly indicated that BSA- and NT-liposomes have no ability to promote the delivery of the encapsulated nucleic acids and that the Trf-liposomes deliver the nucleic acids by a Trf receptor-dependent mechanism. The Trf-liposomes encapsulating siRNA or asODN promote sequence-specific down-regulation of the BCR-ABL mRNA, although a certain extent of nonspecific sequence effects at the protein and cell viability level were observed. Overall, our results indicate that Trf-liposomes encapsulating gene silencing tools allow combining molecular and cellular targeting, which is a valuable approach for cancer treatment.

Masking MALT1: the paracaspase's potential for cancer therapy

A key feature of aggressive B cell lymphomas is constitutive NF-κB activation, which requires signals from the CARD11–BCL-10–MALT1 (CMB) complex. The unique enzymatic activity of MALT1 degrades one of its binding partners, BCL-10, as well as the NF-κB inhibitor A20. New data shows that targeting MALT1 protease activity may be a promising therapeutic strategy for treating aggressive B cell lymphomas.

Genomic biomarkers for molecular imaging: predicting the future

Over the past few decades, great strides have been made in anatomical imaging of disease that has led to their diagnosis with minimal invasion. Despite these advances, diseases such as cancer continue to take one human life every minute in the United States. Complimentary approaches that pertain directly to the genesis of the disease might contribute to its early diagnosis and subsequent management. In cancer, an array of molecular abnormalities leading to the modulations in expression of key proteins important in the cellular signaling pathways and cell proliferation has been identified. These specific disease fingerprints, biomarkers, are overexpressed on malignant cell surfaces or within the cytoplasm, and they provide unique targets that are promising for improving cancer diagnosis and therapy. We and others have designed, synthesized, and evaluated some novel probes specific for those oncogenes and oncogene product biomarkers for PET and SPECT molecular imaging of certain types of cancers. This article briefly describes this approach and gives specific examples that depict the ability of molecular imaging to detect occult lesions not detectable by current scintigraphic approaches. The article also outlines a few examples predicting other possible applications of targeting such specific probes not yet used.

Targeted manipulation of apoptosis in cancer treatment

Apoptosis is a fundamental process in the development and maintenance of multicellular organisms and its regulation is commonly disrupted in human cancers. In vitro and in vivo, effective treatment of cancer with radiotherapy or anticancer drugs (or both) is frequently associated with increased markers of apoptosis. However, clinical resistance to treatment is common in many tumours, particularly with increasing lines of therapy. Diminished ability to undergo apoptosis might cause extensive therapeutic cross-resistance in cancer cells. With increased understanding of the regulatory and effector molecules of apoptosis new drugs have been developed that might manipulate the apoptotic balance in cancer cells in favour of cell death. This Review summarises the rationale for direct manipulation of various elements of apoptosis and describes agents that are currently under investigation in early-phase clinical trials in many different cancer types.

Biodistribution of 68Ga-labeled LNA-DNA mixmer antisense oligonucleotides for rat chromogranin-A

In vivo monitoring of gene expression may be accomplished using a most advanced imaging technology such as positron emission tomography (PET). However, a range of methodological and biological hurdles needs exploration. In the present study, 20-mer DNA-LNA (locked nucleic acid) mixmer oligonucleotides specific for rat Chromogranin-A (Chg-A) mRNA were labeled with 68Ga and their biodistribution were investigated in rats; namely, two Antisense (LNA1, LNA2--differing only in the positioning of LNA modification), Mismatched, and Sense sequences. In addition, in vivo and in vitro metabolite analysis of LNA1 and LNA2 was compared, and hybridization in solution was performed to verify the hybridization ability after labeling. Furthermore, semiquantitative polymerase chain reaction was carried out to find organs expressing Chg-A mRNA in the rat. The biodistribution patterns altered according to the sequence and the positioning of LNA modification. The pattern of Mismatched--differing only in two nucleotides from the two Antisenses--was similar to that of Sense, whereas the pattern of LNA1 and LNA2 showed differences. Uptake in the adrenal gland was twofold higher with LNA2 compared to the other three oligonucleotides. Intact LNA2 could be observed in the 60-minute sample in vivo, whereas in vitro, the intact compound of both Antisenses could also be detected after 2 hours. Hybridization in solution revealed that the two Antisenses retained their hybridization abilities after 68Ga-labeling. With decreasing magnitude, Chg-A mRNA was expressed in the adrenal gland, intestine, testis, and pancreas. This study further supported LNA-DNA mixmer to be a favorable modification for antisense targeting approach with respect to hybridization and longer plasma residence; however, the organ uptake was dominated by processes irrelevant to specific hybridization.

Novel translational strategies in colorectal cancer research

Defining translational research is still a complex task. In oncology, translational research implies using our basic knowledge learnt from in vitro and in vivo experiments to directly improve diagnostic tools and therapeutic approaches in cancer patients. Moreover, the better understanding of human cancer and its use to design more reliable tumor models and more accurate experimental systems also has to be considered a good example of translational research. The identification and characterization of new molecular markers and the discovery of novel targeted therapies are two main goals in colorectal cancer translational research. However, the straightforward translation of basic research findings, specifically into colorectal cancer treatment and vice versa is still underway. In the present paper, a summarized view of some of the new available approaches on colorectal cancer translational research is provided. Pros and cons are discussed for every approach exposed.

Sequence-specific purification of DNA oligomers in hydrophobic interaction chromatography using peptide nucleic acid amphiphiles: extended dynamic range

We present improvements on a previously reported method (Vernille JP, Schneider JW. 2004. Biotechnol Prog 20(6):1776-1782) to purify DNA oligomers by attachment of peptide nucleic acid amphiphiles (PNAA) to particular sequences on the oligomers, followed by their separation from unbound oligomers using hydrophobic interaction chromatography (HIC). Use of alkyl-modified HIC media (butyl and octyl sepharose) over phenyl-modified media (phenyl sepharose) reduced the elution time of unbound DNA while not affecting the elution time of the PNAA/DNA complex. Modifying the alkane tail length for PNAA from C(12) to C(18) increased slightly the retention of PNAA/DNA duplexes. By combining these two refinements, we show that sequence-specific purifications of DNA oligomers 60 bases in length or more can be achieved with high resolution, even when the PNAA alkane is attached to the center of the target strand. The insensitivity of the PNAA/DNA duplex binding to choice of HIC media appears to be due to a surface-induced aggregation phenomenon that does not occur in the case of untagged DNA. We also report on the use of batch HIC as an adequate predictor of elution profiles in linear gradient HIC, and its potential to considerably reduce purification times by applying step gradients.

Technology insight: gene therapy and its potential role in the treatment of medullary thyroid carcinoma

Metastatic medullary thyroid cancer (MTC) responds poorly to conventional treatments with chemotherapy and radiotherapy. Gene therapy--the transfer of genetic material for therapeutic purposes--might have therapeutic potential for patients with progressive metastatic MTC that is incurable by conventional treatments. To date, a number of gene-therapy strategies have been explored, primarily those that use replication-deficient adenovirus vectors to transfer therapeutic genes to tumor cells. Tissue-specific expression of the promoter for calcitonin and calcitonin-related polypeptide alpha has allowed therapeutic genes to be specifically expressed in calcitonin-secreting cells and in the MTC tumors derived from them; such tissue-specific expression contributes to improved safety of gene therapies and has the potential to increase their therapeutic index. In addition, the identification of an MTC-specific peptide ligand raises the possibility of developing an MTC-selective vector. In this article, we have described the exciting area of gene therapy in the management of MTC with a focus on preclinical in vitro and in vivo MTC models.

[Oligonucleotide therapeutics - an emerging novel class of compounds]

Oligonucleotide therapeutics are short, single- or double-stranded DNA or RNA molecules consisting of strands of 10-50 nucleotides. By targeted modulation of gene expression oligonucleotides provide the chance of targeting diseases at their molecular level. Within this novel emerging class of compounds oligonucleotide therapeutics are discriminated by their structure, function and mode of action. While antisense oligonucleotides, ribozymes and siRNAs suppress the expression of a protein by complementary hybridizing with their target mRNA, aptamers bind like antibodies to their target protein and thereby inhibit its function. Immunostimulatory oligonucleotides are due to sequence motifs within their nucleotide sequence able to trigger a therapeutic exploitable immune response. Currently, there are only two oligonucleotide therapeutics approved by the FDA, namely the antisense oligonucleotide Fomivirsen and the aptamer Macugen. In this review the mode of action of the diverse oligonucleotide therapeutics and their current status in clinical development will be discussed.

The Myc oncoprotein as a therapeutic target for human cancer

Myc expression is deregulated in a wide range of human cancers and is often associated with aggressive, poorly differentiated tumors. The Myc protein is a transcription factor that regulates a variety of cellular processes including cell growth and proliferation, cell-cycle progression, transcription, differentiation, apoptosis, and cell motility. Potential strategies that either inhibit the growth promoting effect of Myc and/or activate its pro-apoptotic function are presently being explored. In this review, we give an overview of Myc activation in human tumors and discuss current strategies aimed at targeting Myc for cancer treatment. Such therapies could have potential in combination with mechanistically different cytotoxic drugs to combat and eradicate tumors cells.