Bcl-2 reduces lymphomagenesis in deltaV-TCRbeta transgenic mice

B-cell receptors and heavy chain diseases: guilty by association?

Heavy chain diseases (HCDs) are B-cell proliferative disorders characterized by the production of monoclonal, incomplete, immunoglobulin (Ig) heavy chains (HCs) without associated light chains (LCs). These abnormal HCs are produced as a consequence of HC gene alterations in the neoplastic B cells. HC gene alterations will also impact on surface HC, which is part of the B-cell receptor (BCR), a crucial player in lymphocyte activation by antigen. The selective advantage conferred to mutant cells by abnormal BCR without an antigen-binding domain may be explained by activation of ligand-independent signaling, in analogy to what has been shown for mutated oncogenic growth factor receptors. Here we review data obtained from mouse models showing abnormal, constitutive activity of HCD-BCR, and we discuss the possible mechanism involved, namely, aberrant spontaneous self-aggregation. This self-aggregation might occur as a consequence of escape from the chaperone immunoglobulin binding protein (BiP) and from the anti-aggregation effect of LC association. The concept of misfolding-induced signaling elaborated here may extend to other pathologies termed conformational diseases.

Bcl-2 overexpression enhances tumor-specific T-cell survival

Although immunotherapy based on the adoptive transfer of tumor-specific T lymphocytes has been shown to result in dramatic clinical responses in some patients, the relatively low levels of engraftment and persistence of the adoptively transferred cells may limit these responses in many patients. In an attempt to develop strategies for prolonging the survival of adoptively transferred T cells, we have carried out studies in which T cells obtained from healthy donors as well as tumor-specific T cells were transduced with a retrovirus expressing the human Bcl-2 gene. Our results indicate that these transduced T cells overexpress Bcl-2, are resistant to death, and have a survival advantage following interleukin-2 withdrawal compared with control T cells transduced with a retrovirus expressing green fluorescent protein. Tumor-specific T cells overexpressing Bcl-2 maintained their ability to specifically recognize and respond to target cells. Furthermore, we show that adoptive immunotherapy of an established B16 tumor can be significantly enhanced by overexpressing Bcl-2 in melanoma-specific T-cell receptor transgenic T cells. Our data suggest that adoptive immunotherapy approaches to the treatment of cancer patients may be enhanced using Bcl-2-modified tumor-reactive T cells.

Black tea protects immunocytes from tumor-induced apoptosis by changing Bcl-2/Bax ratio

It is known that cancer is associated with altered immune function. We demonstrated earlier that black tea inhibits tumor growth in a dose-dependent manner. Here, we report that apoptosis was the cause of immunocyte death in Ehrlich's ascites carcinoma (EAC)-bearing mice and anti-tumor dose of black tea restored EAC-induced immunosuppression by inhibiting apoptosis. A search for the molecular mechanism revealed that EAC burden increased the expression of the pro-apoptotic proteins p53 and Bax in splenic lymphocytes although did not change the level of pro-proliferative protein Bcl-2. Interestingly, anti-tumor dose of black tea down-regulated p53, decreased Bax while augmenting Bcl-2 in these cells. As a result, Bcl-2/Bax ratio was increased and the immunocytes were protected from tumor-induced apoptosis. Thus, unlike many other anti-cancer agents, black tea is not only devoid of immunosuppressive effect but also acts as immuno-restorer in tumor-bearing host. These results, thus, raise the possibility of inclusion of black tea in successful therapeutic regimen against cancer.

Transgenic Mice as an In Vivo Model of Lymphomagenesis

This review covers multiple data obtained on genetically modified mice that help to elucidate various intricate molecular mechanisms of lymphomagenesis in humans. We are in a "golden age" of mouse genetics. The mouse is by far the most accessible mammalian system physiologically similar to humans. Transgenic mouse models have illuminated how different genes contribute to human lymphomagenesis. Multiple experiments with transgenic mice have not only confirmed the data obtained for human lymphomas but also gave additional evidence for the role of some genes and cooperative participation of their products in the development of human lymphomas. Genes and gene networks detected on transgenic mice can successfully serve as molecular targets for tumor therapy. This review demonstrates the extraordinary possibilities of transgenic technology, which is presently one of the readily available, efficient, and accurate tools to solve the problem of cancer.

The role of apoptosis in regulating hematopoiesis and hematopoietic stem cells

Apoptosis, or the ability of cells to die in an orderly and highly regulated manner, is essential for normal development and homeostasis of multicellular organisms. Diseases in which deregulation of this process is implicated include autoimmune diseases, cancer and Alzheimer's disease. The importance of apoptosis for the development and function of lymphoid cells has been extensively investigated. Less clear is the role apoptosis plays in regulating early progenitor and stem cell compartments. This question is being investigated using a transgenic mouse model, H2K-BCL-2, in which all hematopoietic cells have an increased resistance to apoptosis. The same transgenic model is also being used to address the question whether protection against apoptosis can increase system-wide resistance to lethal challenges such as irradiation and chemotherapeutic agents.

Apoptosis and cell proliferation capacity in AKR lymphoma malignancy variants

Dysregulation in apoptotic cell death has recently emerged as a factor in tumorigenesis, but its effect in tumor progression is not yet established. In the present study we evaluated the levels of proliferative and apoptotic cell fractions in a T-cell lymphoma tumor progression model. We compared these features and the expression of apoptosis-related genes in primary tumors of several AKR lymphoma malignancy variants. According to DNA flow cytometry, a considerable proportion of cells (35-40%) was in the proliferative (S + G2/M) phase in all variants, but a slight augmentation with increasing malignancy was noted. Apoptotic cell content was, unexpectedly, the lowest in the less malignant variant. This might be due to the higher content in macrophages observed in this variant, which possibly partly eliminated apoptotic bodies. We found an increase in bcl-2 level with increasing malignancy that was probably counterbalanced by the simultaneous increase observed in the Fas receptor.

Release from apoptosis correlates with tumor progression in the AKR lymphoma

Disturbance of apoptosis is an established factor in tumorigenesis. The role of apoptosis in tumor progression is not yet clear. In the present study we compared the tendency to spontaneous apoptosis (and the proliferative capacity) of tumor cells derived from primary (PT) and metastatic tumor (MT) cells of several AKR lymphoma variants. Apoptosis-related gene expression was also compared. Our results indicate that release from apoptosis has a role in the tumor progression of this T cell lymphoma. At the cellular level, a markedly lower apoptotic tendency was observed in MT than in PT cells. The existence of macrophages only in PT also supports the presence of apoptotic cells in local but not in MTs. By contrast, proliferative capacity does not determine tumor aggressiveness in this system. At the molecular level, we found a higher staining intensity for bcl-2 in MT than in PT cells, suggesting that bcl-2 might be responsible for the reduced apoptosis in MT compared to PT cells. Evidence for p53 overexpression was found in the MT cells of one of the variants but in none of the PT. Comparison of Fas receptor, unexpectedly showed an increased expression in MT versus PT cells, possibly indicating resistance to Fas-induced apoptosis in the MT cells.