The use of agonistic anti-CD40 therapy in treatments for cancer

Antitumor effects of anti-CD40/CpG immunotherapy combined with gemcitabine or 5-fluorouracil chemotherapy in the B16 melanoma model

Our previous studies demonstrated that anti-CD40 mAb (anti-CD40) can synergize with CpG oligodeoxynucleotides (CpG) to mediate antitumor effects by activating myeloid cells, such as macrophages in tumor-bearing mice. Separate teams have shown that chemotherapy with gemcitabine (GEM) or 5-fluorouracil (5-FU) can reduce tumor-induced myeloid-derived suppressor cells (MDSC) in mice. In this study we asked if the same chemotherapy regimens with GEM or 5-FU will enhance the antitumor effect of anti-CD40 and CpG. Using the model of B16 melanoma growing intraperitoneally in syngeneic C57BL/6 mice, we show that these GEM or 5-FU treatment regimens reduced MDSC in the peritoneal cavity of tumor-bearing mice. Treatment of mice with GEM or 5-FU did not significantly affect the antitumor function of macrophages as assessed in vitro. In vivo, treatment with these GEM or 5-FU regimens followed by anti-CD40/CpG resulted in antitumor effects similar to those of anti-CD40/CpG in the absence of GEM or 5-FU. Likewise, reduction of MDSC by in vivo anti-Gr-1 mAb treatment did not significantly affect anti-CD40/CpG antitumor responses. Together, the results show that the GEM or 5-FU chemotherapy regimens did not substantially affect the antitumor effects induced by anti-CD40/CpG immunotherapy.

Effects of CD40 ligation combined with chemotherapy drugs on human breast cancer cell lines

OBJECTIVE

To investigate the influence of recombinant human CD40 ligand (rhCD40L) on the biological behaviour of breast cancer cells.

METHODS

MDA-MB-23l and MDA-MB-435 treated with rhCD40L were observed for changes in the cell cycle, in membrane proteins, and in mRNA levels of B cell lymphoma-extra-large (Bcl-xl), Bcl-2 associated X protein (Bax) and regulated upon activation, normal T cell expressed and secreted (RANTES). Effects of rhCD40L on cell proliferation in the presence or absence of interferon (IFN)-γ (500 IU/ml) and/or doxorubicin (20 ng/ml) were also determined.

RESULTS

rhCD40L dose-dependently inhibited cell proliferation. Combination of rhCD40L with IFN-γ or doxorubicin potentiated the inhibitory activity. After treatment, an increase in cells entering the G₁ phase of the cell cycle was observed, with a significant decrease in the number entering the S phase. Levels of several membrane proteins including CD95L and CD120a were also increased. Reverse transcription-polymerase chain reaction revealed an increase in the Bax/Bcl-xl mRNA ratio and an increase in RANTES.

CONCLUSION

rhCD40L treatment of breast cancer cells mediates a variety of anti-tumour effects, not only by direct cytotoxic activity but also by upregulation of adhesion molecules, co-stimulators and cytokines to rectify T cell immunity.

mTOR kinase inhibitors as potential cancer therapeutic drugs

The mammalian target of rapamycin (mTOR) plays a critical role in the positive regulation of cell growth and survival primarily through direct interaction with raptor (forming mTORC complex 1; mTORC1) or rictor (forming mTOR complex 2; mTORC2). The mTOR axis is often activated in many types of cancer and thus has become an attractive cancer therapeutic target. The modest clinical anticancer activity of conventional mTOR allosteric inhibitors, rapamycin and its analogs (rapalogs), which preferentially inhibit mTORC1, in most types of cancer, has encouraged great efforts to develop mTOR kinase inhibitors (TORKinibs) that inhibit both mTORC1 and mTORC2, in the hope of developing a novel generation of mTOR inhibitors with better therapeutic efficacy than rapalogs. Several TORKinibs have been developed and actively studied pre-clinically and clinically. This review will highlight recent advances in the development and research of TORKinibs and discuss some potential issues or challenges in this area.

Targeting of the tumor necrosis factor receptor superfamily for cancer immunotherapy

The tumor necrosis factor (TNF) ligand and cognate TNF receptor superfamilies constitute an important regulatory axis that is pivotal for immune homeostasis and correct execution of immune responses. TNF ligands and receptors are involved in diverse biological processes ranging from the selective induction of cell death in potentially dangerous and superfluous cells to providing costimulatory signals that help mount an effective immune response. This diverse and important regulatory role in immunity has sparked great interest in the development of TNFL/TNFR-targeted cancer immunotherapeutics. In this review, I will discuss the biology of the most prominent proapoptotic and co-stimulatory TNF ligands and review their current status in cancer immunotherapy.

Prospects of combinatorial synthetic peptide vaccine-based immunotherapy against cancer

The insight that the immune system is involved in tumor resistance is gaining momentum and this has led to the development of immunotherapeutic strategies aiming at enhancement of immune-mediated tumor destruction. Although some of these strategies have moderate clinical benefit, most stand-alone therapies fail to significantly affect progressive disease and survival or do so only in a minority of patients. Research on the mechanisms underlying the generation of immune responses against tumors and the immune evasion by tumors has emphasized that various mechanisms simultaneously prevent effective immunity against cancer including inefficient presentation of tumor antigens by dendritic cells and induction of negative immune regulation by regulatory T-cells (Tregs) and myeloid derived suppressor cells (MDSCs). Thus the design of therapies that simultaneously improve effective tumor immunity and counteract immune evasion by tumors seems most desirable for clinical efficacy. As it is unlikely that a single immunotherapeutic strategy addresses all necessary requirements, combinatorial strategies that act synergistically need to be developed. Here we discuss the current knowledge and prospects of treatment with synthetic peptide vaccines that stimulate tumor-specific T-cell responses combined with adjuvants, immune modulating antibodies, cytokines and chemotherapy. We conclude that combinatorial approaches have the best potency to accomplish the most significant tumor destruction but further research is required to optimize such approaches.

Agonistic anti-CD40 induces thyrocyte proliferation and promotes thyroid autoimmunity by increasing CD40 expression on thyroid epithelial cells

CD40 is expressed on cells of the immune system and in some tissues that are targets for autoimmune-mediated damage. It is not known if CD40 expression in target tissues plays a role in the pathology of autoimmune diseases. This study shows that agonistic anti-CD40 induces strong and sustained proliferation of thyroid epithelial cells (TECs), or thyrocytes, in IFN-γ(-/-) autoimmune-prone NOD and NOD.H-2h4 mice. TEC proliferation is accompanied by greatly increased expression of CD40 on TECs, development of fibrosis and hypothyroidism, and increased expression of proinflammatory molecules in thyroids. Bone marrow chimera experiments indicate that TEC expression of CD40 is required for anti-CD40-induced TEC proliferation, but lymphoid cells do not have to express CD40. TEC proliferation is reduced in wild-type mice given anti-CD40, presumably because they produce IFN-γ, which inhibits TEC proliferation. CD40 also increases on TECs during development of an autoimmune thyroid disease characterized by TEC hyperproliferation that develops spontaneously in IFN-γ(-/-) NOD.H-2h4 mice. TEC hyperproliferation development is accelerated in mice given agonistic anti-CD40. These studies provide new information regarding the role of target tissue expression of CD40 in development of autoimmunity and suggest that use of agonistic anti-CD40 for tumor therapy could result in autoimmune disease.

The nature of activatory and tolerogenic dendritic cell-derived signal II

Dendritic cells (DCs) are central in maintaining the intricate balance between immunity and tolerance by orchestrating adaptive immune responses. Being the most potent antigen presenting cells, DCs are capable of educating naïve T cells into a wide variety of effector cells ranging from immunogenic CD4⁺ T helper cells and cytotoxic CD8⁺ T cells to tolerogenic regulatory T cells. This education is based on three fundamental signals. Signal I, which is mediated by antigen/major histocompatibility complexes binding to antigen-specific T cell receptors, guarantees antigen specificity. The co-stimulatory signal II, mediated by B7 family molecules, is crucial for the expansion of the antigen-specific T cells. The final step is T cell polarization by signal III, which is conveyed by DC-derived cytokines and determines the effector functions of the emerging T cell. Although co-stimulation is widely recognized to result from the engagement of T cell-derived CD28 with DC-expressed B7 molecules (CD80/CD86), other co-stimulatory pathways have been identified. These pathways can be divided into two groups based on their impact on primed T cells. Whereas pathways delivering activatory signals to T cells are termed co-stimulatory pathways, pathways delivering tolerogenic signals to T cells are termed co-inhibitory pathways. In this review, we discuss how the nature of DC-derived signal II determines the quality of ensuing T cell responses and eventually promoting either immunity or tolerance. A thorough understanding of this process is instrumental in determining the underlying mechanism of disorders demonstrating distorted immunity/tolerance balance, and would help innovating new therapeutic approaches for such disorders.