Monitoring of immunosuppressive therapy in renal transplanted patients

Immunological aspects and therapeutic significance of an autoantibody against histone H1 in a rat model of concanavalin A-induced hepatitis

We previously demonstrated the immunosuppressive activity of anti-histone H1 autoantibody induced in experimental and clinical liver allograft tolerance. This study aimed to explore the immunological aspects of anti-histone H1 autoantibody in liver injury induced by concanavalin A (Con A). To establish a Con A-hepatitis model, 20 mg/kg Con A was intravenously injected into rats, after which liver function and histopathological analyses were performed. In this model, anti-histone H1 autoantibody was transiently induced in the sera during the natural recovery stage, 3-7 days after Con A injection. To evaluate the therapeutic significance of anti-histone H1 autoantibody, a polyclonal antibody against histone H1 was intraperitoneally injected immediately after Con A injection. We found that injection of anti-histone H1 antibody could reduce Con A-induced liver damage. Further mechanical analyses revealed that anti-histone H1 antibody altered the intracellular activation of mitogen-activated protein kinase, nuclear factor-kappaB and calcineurin via T-cell receptor signalling, suggesting that anti-histone H1 antibody may protect the liver from Con A-induced injury by inhibiting activation of effector T cells. These findings suggest that anti-histone H1 autoantibody may be a natural immune regulatory factor that protects inflamed livers suffering from autoimmune hepatitis and may lead to T-cell unresponsiveness through the selective regulation of mitogen-activated protein kinase/nuclear factor-kappaB and calcineurin signalling.

Apoptosis of CD4(+)CD25(high) T cells in response to Sirolimus requires activation of T cell receptor and is modulated by IL-2

Targeted molecular therapies inhibit proliferation and survival of cancer cells but may also affect immune cells. We have evaluated the effects of Sirolimus and Sorafenib on proliferation and survival of lymphoid cell subsets. Both drugs were cytotoxic to CD4(+)CD25(high) T cells, and were growth inhibitory for CD4(+) and CD8(+) T cells. Cytotoxicity depended on CD3/CD28 stimulation and was detectable within 12 h, with 80-90% of CD4(+)CD25(high) cells killed by 72 h. Cell death was due to apoptosis, based on Annexin V and 7AAD staining. Addition of IL-2 prevented the apoptotic response to Sirolimus, potentially accounting for reports that Sirolimus can enhance proliferation of CD4(+)CD25(high) cells. These results predict that Sirolimus or Sorafenib would reduce CD4(+)CD25(high) cells if administered prior to antigenic stimulation in an immunotherapy protocol. However, administration of IL-2 protects CD4(+)CD25(high) T cells from cytotoxic effects of Sirolimus, a response that may be considered in design of therapeutic protocols.

Synergistic inhibition of human melanoma proliferation by combination treatment with B-Raf inhibitor BAY43-9006 and mTOR inhibitor Rapamycin

BACKGROUND

Targeted inhibition of protein kinases is now acknowledged as an effective approach for cancer therapy. However, targeted therapies probably have limited success because cancer cells have alternate pathways for survival and proliferation thereby avoiding inhibition. We tested the hypothesis that combination of targeted agents would be more effective than single agents in arresting melanoma cell proliferation.

METHODS

We evaluated whether BAY43-9006, an inhibitor of the B-Raf kinase, and rapamycin, an inhibitor of the mTOR kinase, would inhibit serum-stimulated proliferation of human melanoma cell lines, either alone or in combination. Proliferation was measured by quantitating melanoma cell numbers with a luciferase for ATP. Phosphorylation of proteins downstream of targeted kinase(s) was assayed by immunoblots. Statistical significance was determined with the Student-T test. Isobologram analysis was performed to distinguish additive versus synergistic effects of combinations of drugs.

RESULTS

Serum-stimulated proliferation of multiple human melanoma cell lines was inhibited by BAY43-9006 and by rapamycin. Melanoma cells containing the B-Raf mutation V599E were more sensitive than cells with wild-type B-raf to 10 nM doses of both BAY43-9006 and rapamycin. Regardless of B-Raf mutational status, the combination of low dose rapamycin and BAY43-9006 synergistically inhibited melanoma cell proliferation. As expected, rapamycin inhibited the phosphorylation of mTOR substrates, p70S6K and 4EBP1, and BAY43-9006 inhibited phosphorylation of ERK, which is dependent on B-Raf activity. We also observed unexpected rapamycin inhibition of the phosphorylation of ERK, as well as BAY43-9006 inhibition of the phosphorylation of mTOR substrates, p70S6K and 4EBP1.

CONCLUSION

There was synergistic inhibition of melanoma cell proliferation by the combination of rapamycin and BAY 43-9006, and unexpected inhibition of two signaling pathways by agents thought to target only one of those pathways. These results indicate that combinations of inhibitors of mTOR and of the B-raf signaling pathways may be more effective as a treatment for melanoma than use of either agent alone.