bryostatin-1 and Burkitt-Lymphoma

Strategies to circumvent or lessen the myelotoxicity associated with combination chemotherapy may improve the overall outcome of the management of patients particularly in resource poor settings.. To develop effective non-myelotoxic therapies for Burkitt's Lymphoma (BL) and AIDS-related non-Hodgkin's lymphoma.. Publications, original and review articles, conference abstracts searched mainly on Pubmed indexed for medline.. A systematic review of the clinical problem of combination chemotherapy. Identification of clinical strategies that circumvent or lessen the myelotoxicity of combination cytotoxic chemotherapy. Length of survival, lack of clinically significant (> grade 3) myelosuppression and weight loss were used as markers of myelotoxicity.. Review of published experience with some of these strategies including dose-modification of multi-agent chemotherapy; rationale for targeted therapies, and the preclinical development of a mouse model exploring the role of metronomic scheduling substantiate pragmatism and feasibility of these approaches.. Myelotoxic death rates using multi-agent induction chemotherapy approach 25% for endemic Burkitt's lymphoma and range between 20% to 60% for AIDS-related malignancy. This is mostly explained by the paucity of supportive care compounded by wasting and inanition attributable to advanced cancer and HIV infection making patients more susceptible to myelosuppressive side effects of cytotoxic chemotherapy. Investigations and alternative approaches that lessen or circumvent myelotoxicity of traditional cytotoxic chemotherapy for the management of Burkitt's lymphoma and AIDS-related non-Hodgkin's lymphoma in the resource-constrained setting are warranted. Pertinent pre-clinical and clinical data are emerging to support the need for abrograting the myelosuppressive effects of traditional cytotoxic chemotherapy. This can be achieved by developing targeted anti-viral and other strategies, such as the use of bryostatin 1 and vincristine, and by developing a preclinical mouse model to frame the clinical rationale for a pilot trial of metronomic therapy for the treatment of Burkitt's and AIDS-related lymphoma. Implementation of these investigational approaches must be encouraged as viable anti-cancer therapeutic strategies particularly in the resource-constrained settings.

Topics: Antineoplastic Agents; Bryostatins; Burkitt Lymphoma; Drug Therapy, Combination; Humans; Lymphoma, AIDS-Related; Macrolides; Vincristine

While the defects in HLA class I-mediated Ag presentation by Burkitt lymphoma (BL) have been well documented, CD4+ T-cells are also poorly stimulated by HLA class II Ag presentation, and the reasons underlying this defect(s) have not yet been fully resolved. Here, we show that BL cells are deficient in their ability to optimally stimulate CD4+ T cells via the HLA class II pathway. The observed defect was not associated with low levels of BL-expressed costimulatory molecules, as addition of external co-stimulation failed to result in BL-mediated CD4+ T-cell activation. We further demonstrate that BL cells express the components of the class II pathway, and the defect was not caused by faulty Ag/class II interaction, because antigenic peptides bound with measurable affinity to BL-associated class II molecules. Treatment of BL with broystatin-1, a potent modulator of protein kinase C, led to significant improvement of functional class II Ag presentation in BL. The restoration of immune recognition appeared to be linked with an increased expression of a 17 kDa peptidylprolyl-like protein. These results demonstrate the presence of a specific defect in HLA class II-mediated Ag presentation in BL and reveal that treatment with bryostatin-1 could lead to enhanced immunogenicity.

Topics: Antigen Presentation; Antineoplastic Agents; Bryostatins; Burkitt Lymphoma; CD4-Positive T-Lymphocytes; Cell Line, Tumor; HLA-D Antigens; Humans; Interleukin-2; Lymphocyte Activation; Signal Transduction

The ratio of Bax to Bcl-2 protein can determine whether cells will die via apoptosis or be protected from it. Reh was found to express a high basal level of Bcl-2 but was lacking of Bax protein expression. Treatment with bryostatin 1 induced a down-regulation in Bcl-2 protein that was not accompanied by an obvious Bax protein induction or apoptosis. These results suggest that a decreased level of Bcl-2 alone in this cell line is not sufficient for apoptosis induction. In an effort to identify the mechanism whereby apoptosis could be induced in this ALL model, we treated Reh cells with three microtubule inhibitors: dolastatin 10, auristatin PE and vincristine, in the presence and absence of bryostatin 1. When used alone, only dolastatin 10 induced apoptosis that was detected morphologically, and by flow cytometry. Western blots revealed that dolastatin 10-induced apoptosis was accompanied by the induction of Bax protein and the reduction in Bcl-2 protein. Auristatin PE and vincristine induced both Bax and Bcl-2 protein, leaving the Bax:Bcl-2 ratio constant. Reh cells pretreated for 24 h with bryostatin 1 followed by dolastatin 10, auristatin PE or vincristine showed significant apoptosis which was accompanied by Bcl-2 protein down regulation and Bax protein up regulation. We conclude that: (1) expression of bax is necessary for apoptosis-induction in this model; (2) a decrease in Bcl-2 level alone is not sufficient and might not be necessary for apoptosis-induction; and (3) the ratio of Bax:Bcl-2 plays a critical role in susceptibility to apoptosis in Reh cells. The results from this study should prove useful in guiding the clinical application of these novel agents in the treatment of acute lymphoblastic leukemia.

Topics: Antineoplastic Agents; Apoptosis; bcl-2-Associated X Protein; Bryostatins; Burkitt Lymphoma; Humans; Lactones; Macrolides; Oligopeptides; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Tumor Cells, Cultured; Vincristine