Analysis of ribosyl-modified, mixed backbone analogs of a bcl-2/bcl-xL antisense oligonucleotide

Neuroprotective effects of galectin‑1 on cerebral ischemia/reperfusion injury by regulating oxidative stress

Oxidative stress contributes to the pathology of cerebral ischemia/reperfusion (I/R) injury. Galectin-1 has shown an anti-oxidative stress effect. The present study investigated whether this anti-oxidative stress effect can account for the neuroprotective actions of galectin-1 induced by cerebral I/R injury. A cerebral I/R injury model was created in C57Bl/6 mice by transient occlusion of the middle cerebral artery, after which the mice were treated with galectin-1 for 3 days. Infarct volumes were measured. A rotarod test and neurological deficit score assessment was performed to evaluate the neurological deficits. Oxidative stress was evaluated by measuring the levels of reactive oxygen species (ROS) and lipid peroxidation malondialdehyde (MDA), while the anti-oxidative stress status was assessed by measuring molecules such as catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidation enzyme (GSH-Px) in the ischemic cerebral hemisphere of mice. The inflammatory cytokines, including Interleukin 1 (IL-1), IL-6 and tumor necrosis factor alpha (TNF-α) were measured, and the expression of microglia was evaluated by immunohistochemistry in the ischemic cerebral hemisphere of mice. Galectin-1 treatment ameliorated neurological deficits and reduced infarct volumes in the mice model with cerebral I/R injury. Moreover, it was demonstrated that galectin-1 can significantly alleviate cerebral I/R injury in the ischemic cerebral hemisphere by decreasing the production of ROS and MDA, but increasing the production of CAT, SOD and GSH-Px. Galectin-1 treatment decreased microglia expression, and IL-1, IL-6 and TNF-α levels in the ischemic cerebral hemisphere of mice. Galectin-1 could improve the outcome of cerebral I/R injury by alleviating oxidative stress. Moreover, the neuroprotective effect of galectin-1 in cerebral ischemia could be related to its anti-oxidative stress effect.

Targeting the Bcl-2-regulated apoptosis pathway by BH3 mimetics: a breakthrough in anticancer therapy?

Induction of apoptosis in tumor cells by direct activation of the Bcl-2-regulated apoptosis pathway by small molecule drugs carries high hopes to overcome the shortcomings of current anticancer therapies. This novel therapy concept builds on emerging insights into how Bcl-2-like molecules maintain mitochondrial integrity and how pro-apoptotic BH3-only proteins lead to its disruption. Means to unleash the pro-apoptotic potential of BH3-only proteins in tumor cells, or to bypass the need for BH3-only proteins by directly blocking possible interactions of Bcl-2-like pro-survival molecules with Bax and/or Bak, constitute interesting options for the design of novel anticancer therapies. For the optimization and clinical implementation of these novel anticancer strategies, a detailed understanding of the role of individual BH3-only proteins in cell death signaling in healthy cells and during tumor suppression is required. In this review, we will touch on the latest findings on BH3-only protein function and attempts to define the molecular properties of the so-called 'BH3 mimetics,' a novel class of anticancer agents, able to prompt apoptosis in tumor cells, regardless of their p53 or Bcl-2 status.

Antisense inhibition at the beta-secretase-site of beta-amyloid precursor protein reduces cerebral amyloid and acetyl cholinesterase activity in Tg2576

Misprocessing of beta-amyloid precursor protein (APP) leading to the formation of elevated quantities of beta-amyloid peptide (Abeta), derived by a cleavage at the beta-secretase site (N-671/673aa) and by a cleavage at the gamma-secretase site (C-711/713aa) of APP, is considered a key event in the pathogenesis of Alzheimer disease (AD). Point mutations near the beta-secretase site in the human gene for APP, such as in the Swedish mutation-KM670/671NL, lead to a form of dominantly inherited AD. These mutations are known to promote beta-site cleavage and to increase levels of Abeta. Abeta has been shown previously to increase acetyl cholinesterase (AChE) activity in vitro. We wished to test whether translational blocking of APP-mRNA at the mutated beta-site by antisense (AS) oligodeoxynucleotides (ODNs) directed to the mutated site will reduce cerebral amyloid in the Swedish transgenic mouse model (Tg2576). Mice were injected i.c.v. with AS-ODNs directed at the mutated beta-site (AS-beta site) or with AS-ODNs directed at the normal gamma-site (AS-gamma site) of human APP-mRNA, and compared with procedural controls that received i.c.v. injections of sense ODNs at the beta-site (S-beta site), sense ODNs at the gamma-site (S-gamma site) or mismatched ODNs, and with untreated littermates (Lt) and untreated transgenic mice (Tgs). ODNs were injected into the 3rd ventricle once a week for 4 weeks. Brains were processed for enzyme-linked immunosorbent assay analysis of beta- and gamma-cleaved soluble Abeta40 (sAbeta40), beta- and gamma-cleaved soluble Abeta42 (sAbeta42) and alpha-cleaved soluble beta-amyloid precursor protein (sAPPalpha). The physiological relevance of AS ODNs was tested by evaluating the cerebral distribution of AChE before and after the treatment. AChE was found increased about fivefold in Tg cortex as compared with control brain. Results show that compared with untreated and procedural controls, AS-beta increased cerebral levels of sAPPalpha by 43% and reduced sAbeta40/42 by approximately 39%; while simultaneously reducing the cortical density of AChE by approximately fourfold in the treated Tg animals, almost to the level found in the control brain (all values P<0.0001, analysis of variance, unpaired two-tailed Student's t-test), while AS-gamma did not have any effect. These results indicate that AS directed to the mutated beta-site may be an effective approach to treat familial AD.

Preadministration of high-dose salicylates, suppressors of NF-kappaB activation, may increase the chemosensitivity of many cancers: an example of proapoptotic signal modulation therapy

NF-kappaB activity is elevated in a high proportion of cancers, particularly advanced cancers that have been treated previously. Cytotoxic treatment selects for such up-regulation inasmuch as NF-kappaB promotes transcription of a large number of proteins that inhibit both the intrinsic and extrinsic pathways of apoptosis; NF-kappaB also boosts expression of mdr1, which expels many drugs from cells. Indeed, high NF-kappaB activity appears to be largely responsible for the chemo- and radioresistance of many cancers. Thus, agents that suppress NF-kappaB activity should be useful as adjuvants to cytotoxic cancer therapy. Of the compounds that are known to be NF-kappaB antagonists, the most practical for current use may be the nonsteroidal anti-inflammatory drugs aspirin, salicylic acid, and sulindac, each of which binds to and inhibits Ikappa kinase- beta, a central mediator of NF-kappa activation; the low millimolar plasma concentrations of salicylate required for effective inhibition of this kinase in vivo can be achieved with high-dose regimens traditionally used to manage rheumatic disorders. The gastrointestinal toxicity of such regimens could be minimized by using salsalate or enteric-coated sodium salicy-late or by administering misoprostol in conjunction with aspirin therapy. Presumably, best results would be seen if these agents were administered for several days prior to a course of chemo- or radiotherapy, continuing throughout the course. This concept should first be tested in nude mice bearing xenografts of chemoresistant human tumors known to have elevated NF-kappa activity. Ultimately, more complex adjuvant regimens can be envisioned in which salicylates are used in conjunction with other NF-kappa antagonists and/or agents that target other mediators of down-regulated apoptosis in cancer, such as Stat3; coadministration of salicylate and organic selenium may have intriguing potential in this regard. These strategies may also have potential as adjuvants to metronomic chemotherapy, which seeks to suppress angio-genesis by targeting cycling endothelial cells in tumors.

A functionally improved locked nucleic acid antisense oligonucleotide inhibits Bcl-2 and Bcl-xL expression and facilitates tumor cell apoptosis

We previously reported the Bcl-2/Bcl-xL-bispecific activity of the 2'-O-(2-methoxy)ethyl (2'-MOE)-modified gapmer antisense oligonucleotide 4625. This oligonucleotide has 100% complementarity to Bcl-2 and three mismatches to Bcl-xL. In the present study, the isosequential locked nucleic acid (LNA)-modified oligonucleotide 5005 was generated, and its ability to further improve the downregulation of the two antiapoptotic targets in tumor cells was examined. We demonstrate that compared with 4625, 5005 more effectively decreased the expression of the mismatching Bcl-xL target gene in MDA-MB-231 breast and H125 lung cancer cells. In both cell lines, antisense activity caused decreased cell viability by induction of apoptosis. Moreover, in combination with various anticancer agents, 5005 reduced tumor cell viability more effectively than 4625. We describe for the first time the functional comparison of isosequential Bcl-2/Bcl-xL-bispecific 2'-MOE and LNA-modified antisense oligonucleotides and report that the LNA analog more effectively downregulated the two apoptosis inhibitors overexpressed in human tumors. Our data underscore the ability of LNA modifications to enhance the efficacy and favorably modulate the target specificity of antisense oligonucleotides.

Targeting multiple signaling pathways as a strategy for managing prostate cancer: multifocal signal modulation therapy

The aberrant behavior of cancer reflects upregulation of certain oncogenic signaling pathways that promote proliferation, inhibit apoptosis, and enable the cancer to spread and evoke angiogenesis. Theoretically, it should be feasible to decrease the activity of these pathways-or increase the activity of pathways that oppose them-with noncytotoxic agents. Since multiple pathways are dysfunctional in most cancers, and cancers accumulate new oncogenic mutations as they progress, the greatest and most durable therapeutic benefit will likely be achieved with combination regimens that address several targets. Thus, a multifocal signal modulation therapy (MSMT) of cancer is proposed. This concept has already been documented by researchers who have shown that certain combinations of signal modulators-of limited utility when administered individually-can achieve dramatic suppression of tumor growth in rodent xenograft models. The present essay attempts to guide development of MSMTs for prostate cancer. Androgen ablation is a signal-modulating measure already in standard use in the management of delocalized prostate cancer. The additional molecular targets considered here include the type 1 insulin-like growth factor receptor, the epidermal growth factor receptor, mammalian target of rapamycin, NF-kappaB, hypoxia-inducible factor-1alpha, hsp90, cyclooxygenase-2, protein kinase A type I, vascular endothelial growth factor, 5-lipoxygenase, 12-lipoxygenase, angiotensin II receptor type 1, bradykinin receptor type 1, c-Src, interleukin-6, ras, MDM2, bcl-2/bclxL, vitamin D receptor, estrogen receptor-beta, and PPAR-. Various nutrients and phytochemicals suspected to have potential utility in prostate cancer prevention and therapy, but whose key molecular targets are still unknown, might reasonably be incorporated into MSMTs for prostate cancer; these include lycopene, selenium, green tea polyphenols, genistein, and silibinin. MSMTs can be developed systematically by testing various combinations of signal-modulating agents, in concentrations that can feasibly be achieved and maintained clinically, on human prostate cancer cell lines; combinations that appear promising can then be tested in xenograft models and, ultimately, in the clinic. Some signal modulators can increase response to cytotoxic drugs by upregulating effectors of apoptosis. When MSMTs fail to raise the spontaneous apoptosis rate sufficiently to achieve tumor stasis or regression, incorporation of appropriate cytotoxic agents into the regimen may improve the clinical outcome.

Treatment of melanoma cells with a bcl-2/bcl-xL antisense oligonucleotide induces antiangiogenic activity

We have recently reported that bcl-2 overexpression and hypoxia synergistically interact to modulate vascular endothelial growth factor (VEGF) and in vivo angiogenesis in tumour cells through VEGF mRNA stabilization and hypoxia-inducible factor 1-mediated transcriptional activity. Bcl-2 antisense treatment has shown promising clinical results in patients with malignant melanoma. In the present study, we demonstrated that the bcl-2/bcl-xL bispecific antisense oligonucleotide 4625 inhibits bcl-2 expression and angiogenesis in two bcl-2 overexpressing clones derived from the M14 human melanoma cell line. The antiangiogenic effect was determined in in vitro and in vivo angiogenesis assays. In particular, a reduction of hypoxia-induced VEGF secretion was observed after 4625 treatment, and the conditioned medium (CM) of bcl-2 overexpressing clones treated with 4625 and exposed to hypoxic conditions resulted in decreased endothelial cell proliferation when compared to CM of untreated control cells. In addition, we found that CM of 4625 antisense-treated bcl-2 transfectants inhibited in vivo vessel formation in matrigel plugs implanted subcutaneously in C57/B16 mice. Our findings confirm that bcl-2 plays a crucial role in melanoma angiogenesis and demonstrate for the first time that downregulation of bcl-2 by antisense treatment has potential to inhibit angiogenesis independent of its effect on cell survival. The use of 4625 in cancer therapy is suggested as an approach to facilitate simultaneously tumour cell apoptosis and inhibit tumour angiogenesis.

Recent advances in the development of anticancer agents targeting cell death inhibitors in the Bcl-2 protein family

Hematopoietic malignancies frequently are characterized by defects in apoptosis signaling. This renders the malignant cells resistant to endogenous apoptotic stimuli, as well as exogenous stimuli, such as chemotherapy drugs and radiation. The defective apoptosis seen in human cancers often results from overexpression of antiapoptotic proteins in the Bcl-2 protein family, particularly Bcl-2 and Bcl-X(L). A great deal of effort is currently aimed at developing novel agents to inhibit the expression or function of these proteins. Antisense agents directed against Bcl-2 mRNA are showing considerable promise in clinical trials. In addition, detailed knowledge of the structures of Bcl-2 and Bcl-X(L), coupled with high-throughput and computer-assisted screening of chemical libraries, has led to the identification of a number of short peptides and small organic molecules capable of inhibiting Bcl-2 and Bcl-X(L) function. These newly described agents hold considerable promise for enhancing the chemo- and radiation sensitivities of Bcl-2- and Bcl-X(L)-overexpressing cancers. This review will highlight recent advances in the development and testing of agents targeting cell death inhibitors in the Bcl-2 protein family.

Bcl-2/bcl-xL bispecific antisense treatment sensitizes breast carcinoma cells to doxorubicin, paclitaxel and cyclophosphamide

Overexpression of the anti-apoptotic proteins bcl-2 and bcl-xL is implicated in breast cancer development, tumor progression and drug resistance. Here we describe the use of the bcl-2/bcl-xL bispecific antisense oligonucleotide 4625 to sensitize breast carcinoma cells to anti-cancer drugs routinely used in breast cancer therapy. MCF7 cells were treated with oligonucleotide 4625, doxorubicin, paclitaxel or cyclophosphamide alone, or with combinations of oligonucleotide and the anti-cancer drugs. As measured in cell viability assays, treatment with the various combinations reduced the number of viable MCF7 cells more effectively than treatment with the single drugs alone. Treatment with a sequence control oligonucleotide did not affect cell viability. All combination treatments induced apoptosis as demonstrated by the appearance of massive nuclear condensation in a high proportion of the cells. To further characterize the interaction between 4625 and doxorubicin, paclitaxel or cyclophosphamide, the median-effect method was used. In MCF7 cells all combinations resulted in potent synergistic effects over a broad range of toxicity with combination indices ranging from 0.8 to 0.1. Similarly, strong synergistic interactions between oligonucleotide 4625 and the anti-cancer drugs were also observed in cultures of the breast carcinoma cell line MDA-MB-231. Our data suggest the use of 4625 as a potent adjuvant in breast cancer chemotherapy.

Trafficking of intracerebroventricularly injected antisense oligonucleotides in the mouse brain

Intracerebroventricular (icv) delivery of therapeutic molecules directly into the brain parenchyma has attracted considerable attention because of the advantage of bypassing the blood-brain barrier. Exogenous icv administration of antisense oligodeoxynucleotides (AS-ODNs) has been implicated in modifying gene expression within the targeted brain area. The biodistribution, tissue penetration, and stability of exogenously administered AS-ODNs are the major determinants with regard to their potential utility as agents for modifying gene expression. This report examined the distribution and clearance of labeled AS-ODNs with the aim of exploring the feasibility of icv administration of AS-ODNs as a targeted treatment approach to Alzheimer's disease. A single icv injection of fluorescein-labeled 2'-O-(methoxy) ethyl (2'MOE) ribosyl-modified AS-ODNs directed at the beta-secretase cleavage site of beta-amyloid precursor protein (APP) mRNA into the mouse brain showed rapid uptake by 15 minutes, overall gradual spread and retention by 30 minutes to 3 hours, and complete clearance by 8 hours postinjection. Labeled AS-ODNs were observed to penetrate across the cell membrane and accumulate in both nuclear and cytoplasmic compartments of neuronal and nonneuronal cell populations. Current study provides a basic pattern of uptake, distribution, and stability of AS-ODNs in the mouse brain.