Destruction of conditional insulinoma cell lines in NOD mice: A role for autoimmunity

Abstract

Aims/Hypothesis. βTC-tet (H2 k ) is a conditional insulinoma cell line derived from transgenic mice expressing a tetracycline-regulated oncogene. Transgenic expression of several proteins implicated in the apoptotic pathways increase the resistance of βTC-tet cells in vitro. We tested in vivo the sensitivity of the cells to rejection and the protective effect of genetic alterations in NOD mice. Methods. βTC-tet cells and genetically engineered lines expressing Bcl-2 (CDM3D), a dominant negative mutant of MyD88 or SOCS-1 were transplanted in diabetic female NOD mice or in male NOD mice with diabetes induced by high-dose streptozotocin. Survival of functional cell grafts in NOD-scid mice was also analyzed after transfer of splenocytes from diabetic NOD mice. Autoreactive T-cell hybridomas and splenocytes from diabetic NOD mice were stimulated by βTC-tet cells. Results. βTC-tet cells and genetically engineered cell lines were all similarly rejected in diabetic NOD mice and in NOD-scid mice after splenocyte transfer. In 3-to 6-week-old male NOD mice treated with highdose streptozotocin, the cells temporarily survived, in contrast with C57BL/6 mice treated with high-dose streptozotocin (indefinite survival) and untreated 3-to 6-week-old male NOD mice (rejection). The protective effect of high-dose streptozotocin was lost in older male NOD mice. βTC-tet cells did not stimulate autoreactive T-cell hybridomas, but induced IL-2 secretion by splenocytes from diabetic NOD mice. Conclusion/Interpretation. The autoimmune process seems to play an important role in the destruction of βTC-tet cells in NOD mice. Genetic manipulations intended at increasing the resistance of beta cells were inefficient. Similar approaches should be tested in vivo as well as in vitro. High dose streptozotocin influences immune rejection and should be used with caution. [Diabetologia (2003) 46:504-510]

Diabetes Induces Rapid Suppression of Adaptive Immunity Followed by Homeostatic T‐cell Proliferation

“…Furthermore, we found that a similar degree of hypocellularity (thymus and spleen) can be generated by causing diabetes via removal of the islet transplant. In terms of immune function, our data showed that the previously described reduced ability of STZ‐treated mice to reject allogeneic β TC‐tet tumour cells [2, 3] or in some cases whole islet transplants, can be reversed by curing diabetes with syngeneic islet transplants.…”

Interventional Strategies to Prevent β-Cell Apoptosis in Islet Transplantation

“…Lentiviral-mediated cFLIP overexpression in another murine ␤-cell line (NIT-1) has also been shown to prevent cytokine-mediated ␤-cell death in vitro (40). However, the in vitro benefit of cFLIP overexpression in islet ␤-cells has not been observed in vivo (41). This disappointing observation can most likely be attributed to the recent finding that cFLIP has a dual functionality that depends on expression levels and can, under some circumstances, actually promote apoptosis.…”

“…However, these promising results have been met with mixed outcomes in animal models of transplantation. Adenovirally mediated BCL-2 overexpression in macaque islets reduced the number of islets necessary to reverse diabetes in chemically diabetic nude mice, while ␤TC-Tet cells stably transfected with BCL-2 exhibited no survival advantage in vivo, despite enhanced proliferative capacity (41,48,51). Another antiapoptotic BCL-2 family member, BCL-XL, has proven to be effective in preventing apoptosis triggered by IL-1␤, staurosporine, and serum withdrawal in vitro (52).…”

XIAP Overexpression in Islet β-Cells Enhances Engraftment and Minimizes Hypoxia–Reperfusion Injury

“…The impact of anti‐apoptotic genes in the acute post‐transplant period remains unknown. The mitochondrial apoptotic pathway inhibitors Bcl‐2 and Bcl‐XL have been shown to prevent β‐cell death from hypoxia and/or proinflammatory cytokines in vitro , but have failed to prevent allograft rejection in vivo (11–13). A20, which inhibits NF‐κB activation, has been shown to protect β‐cells from cytokine‐ and Fas‐mediated killing in vitro , and to reduce the β‐cell mass required for syngeneic islet transplantation (14,15).…”