Antisense oligonucleotides complementary to immunoglobulin sequences of BCL-2/immunoglobulin fusion transcript induce apoptosis of t(14;18) lymphoma cells

Parametric model of combination therapy for Non-Hodgkin Lymphoma

The development and clinical testing of drug combinations for the treatment of Non-Hodgkin Lymphoma (NHL) and other cancers has recently shown great promise. However, determining the optimum combination and its associated dosages for maximum efficacy and minimum side effects is still a challenge. This paper describes a parametric analysis of the dynamics of malignant B-cells and the effects of an anti-sense oligonucleotide targeted to BCL-2 (as-bcl-2), anti-CD-20 (rituximab) and their combination, for a SCID mouse human lymphoma xenograft model of NHL. Our parametric model is straightforward. Several mechanisms of malignant B-cell birth and death in the nodal micro-environment are simulated. Cell death is accelerated by hypoxia and starvation induced by tumor scale, by modification of anti-apoptosis with as-bcl-2, and by direct kill effects of rituximab (cell kill by cytotoxic immune cells is not included, due to the absence of an immune system in the corresponding experiments). We show that the cell population dynamics in the control animals are primarily determined by K*, the ratio of rate constants for malignant cell death, K(d), and cell birth, K(b). Tumor growth with independent treatments is reproduced by the model, and is used to predict their effect when administered in combination. Malignant cell lifetimes are derived to provide a quantitative comparison of the efficacy of these treatments. Future experimental and clinical applications of the model are discussed.

DNA-damage sensitizers: Potential new therapeutical tools to improve chemotherapy

Agents that induce DNA damage in cells--the so-called genotoxins--have successfully been used for decades to treat patients with tumors. Genotoxins alter the DNA of cells, which is detected by DNA damage sensors and which leads to the activation of p53. Activation of p53 can lead to the death of cancer cells. The efficacy of genotoxins in humans is however limited by their toxicity to normal tissues. Specific sensitization of tumor cells to the action of genotoxins would reduce the efficacious doses of genotoxins to be used in patients, diminishing the detrimental side-effects of the drugs on normal tissues. A series of compounds able to sensitize cancer cells to DNA-damaging drugs have recently been identified that have the potential to increase the efficacy of currently used anti-cancer treatments.

Lymphoproliferative disorders: prospects for gene therapy

The lymphoproliferative disorders represent a large group of diseases with a significant variation in presentation and clinical course. There has been a trend of increasing incidence for some of these disorders, and despite advances in therapies, a significant number of patients either respond poorly or have early relapses. For this reason there is a need to investigate novel therapies to be used either alone or as adjunct treatment in combination with conventional therapies. Gene therapy is a relatively new field that takes advantage of our increased understanding of molecular biology with the aim of treating a variety of diseases including cancer. It is defined as the introduction of genetic material into cells for therapeutic intent. Methods to improve gene delivery efficiency have been the focus of a large amount of research and to date the optimal procedure uses viruses such as oncoretroviruses, lentiviruses, adenoviruses, adeno-associated viruses and herpes simplex viruses. There are four main gene therapy strategies that might be used for the treatment of lymphoproliferative disorders. First, immunotherapy using tumour vaccines or techniques to enhance the function of immune effector cells has been investigated with some success in patients with B-cell malignancies. Second, the introduction of prodrug-activated 'suicide' genes into cells has been explored, in particular in patients with post-transplantation lymphoproliferative disease. Third, direct lysis of tumour cells using viruses shows some early promise, especially in the treatment of B-cell disorders by manipulating the measles virus to target the CD20 antigen. Finally, anti-gene strategies such as anti-sense therapy, ribozymes, and most recently RNA interference, could be used to suppress expression of specific target genes. RNA interference in particular has tremendous potential and has been studied in the context of anaplastic large cell lymphoma as well as Epstein-Barr virus-associated malignancies. Whilst we are still in the early days of this field and to date results have been modest, there is still a significant potential for gene therapy to play a role in the future treatment of these disorders.

Pro-apoptotic therapy with the oligonucleotide Genasense (oblimersen sodium) targeting Bcl-2 protein expression enhances the biological anti-tumour activity of rituximab

New strategies have evolved in the treatment of patients with non-Hodgkin's lymphoma (NHL). Anti-sense oligonucleotides (ASO) and monoclonal antibody (mAb) therapy, though proven to be safe and effective, have not demonstrated to be curative when used as single agents. We tested an innovative combination strategy involving various mAbs and ASO against Bcl-2 (G3139) in aggressive preclinical models. G3139, under optimal transfection conditions, decreased the proliferation rate of lymphoma cells by 60-75% when compared with controls. In addition, apoptosis was demonstrated in Raji (25%) and DHL-4 cells (30%) treated with Genasense following downregulation of Bcl-2 protein. Downregulation of Bcl-2 by G3139 was associated with a higher degree of rituximab-associated, complement-mediated cytotoxicity and antibody dependent cellular cytotoxicity when compared with rituximab alone-treated controls. In vivo studies in severe combined immunodeficiency (SCID) mice clearly demonstrated synergistic activity between G3139 and rituximab. Treatment of lymphoma-bearing SCID mice with G3139 for two consecutive days prior to each rituximab dose resulted in better disease control and survival than treatment with either agent alone or controls. Our findings suggest that Bcl-2 downregulation by G3139, followed by the administration of rituximab is an efficient anti-tumour strategy associated with improved survival in lymphoma-bearing SCID mice.

Preclinical evaluation of antisense bcl-2 as a chemosensitizer for patients with gastric carcinoma

BACKGROUND

Because bcl-2 is a critical factor for anticancer drug-induced apoptosis, the authors conducted a preclinical evaluation of antisense (AS) bcl-2 as an enhancer of the chemotherapeutic effect in the treatment of patietns with gastric carcinoma.

METHODS

AS bcl-2 was used with 18-mer phosphorothiated oligonucleotides in the MKN-45 gastric carcinoma cell line. Drug sensitivity in vitro was evaluated using the methyl-thiazoldiphenyl tetrazolium assay, and antitumor effects in vivo were evaluated using the nude mouse xenograft. Apoptosis was determined with the terminal deoxyuridine triphosphate nick-end labeling assay. AS bcl-2 in vitro was treated with lipofectin, whereas it was administered intraperitoneally for 6 consecutive days twice every 2 weeks in vivo. Anticancer drugs were administered intraperitoneally four times per week.

RESULTS

bcl-2 was down-regulated to 60% of its initial value after treatment with 1.0 muM AS bcl-2 compared with the controls of random and mismatched oligonucleotides. Drug sensitivity to doxorubicin, cisplatin, and paclitaxel (TXL) was increased 3-4-fold when used in combination with AS bcl-2, which was determined with 50% inhibitory concentration values, compared with the control group. Increased drug sensitivity was associated with apoptosis, which increased in Bax and poly-adenosine diphosphate (ADP-ribose) polymerase and decreased in phosphorylated Akt (pAkt). The antitumor effect of cisplatin and TXL in vivo was enhanced significantly in combination with AS bcl-2. Down-regulation of bcl-2 was observed on Day 4 after the treatment with AS bcl-2.

CONCLUSIONS

Combination treatment with AS bcl-2 and anticancer drugs, including cisplatin and TXL, may be a new strategy for enhancing chemotherapeutic effects in the treatment of gastric carcinoma.

Enhanced efficacy of therapy with antisense BCL-2 oligonucleotides plus anti-CD20 monoclonal antibody in scid mouse/human lymphoma xenografts

Monoclonal anti-CD20 antibody (rituximab) is active, but not curative, therapy for B-cell non-Hodgkin's lymphoma. BCL-2 is an antiapoptotic protein whose expression is dysregulated in most indolent B-cell malignancies. Antisense oligonucleotides (AS-ODNs) that down-regulate BCL-2 expression induce apoptosis and chemosensitize B-cell lymphoma cells. We hypothesized that BCL-2 down-regulation by AS-ODNs would sensitize cells to rituximab and improve therapeutic results. There is enhanced apoptosis and reduction in cell numbers when DoHH2 cells are treated in vitro with rituximab plus BCL-2 AS-ODNs, compared with either agent alone. There is little in vitro effect on WSU-FSCCL cells by rituximab, AS-ODNs that down-regulate BCL-2 by targeting the immunoglobulin portions of the BCL-2-immunoglobulin fusion molecule, or a combination of the two. The combination is more effective than either agent alone in clearing DoHH2 cells from ascites in scid mice. Combination therapy with AS-BCL-2-ODNs and rituximab significantly prolongs survival in both the DoHH2 and WSU-FSCCL models. With higher and repeated doses, this combination could be curative. We conclude that the combination of rituximab and antisense-mediated down-regulation of BCL-2 has enhanced activity against human lymphoma, prolongs survival, and could cure mice bearing human lymphoma. This merits investigation in clinical trials.