The ability of allogeneic lymphocytes to target and eradicate leukemia cells has been established as a true biological entity over the past ten (20) years. Whether such effects can be generated against non-hematological """"""""solid"""""""" malignancies remains unexplored. We initiated a clinical trail using a non-myeloablative approach of allogeneic stem cell transplantation in patients with treatment refractory metastatic renal cell carcinoma (RCC). Definitive evidence for an allogeneic graft-versus-RCC effect has been demonstrated with complete regression of large metastasis observed in some patients. Recently we demonstrated a similar effect to have occurred in a patient with colon carcinoma and prostate cancer. We have subsequently initiated studies investigating immune reconstitution in those demonstrating an anti-RCC effect in attempts to identify both the effector cell populations mediating these regressions as well as their target antigens. Our laboratory has confirmed the expression of minor histocompatibility antigens on the surface of kidney cancer cells. We demonstrated that cytotoxic T-cell clones with specificity for minor antigens are capable of killing RCC cells in patients having a GVT effect post transplant. We also were able to expand T-cell clones in two responding patients that recognized either tumor cells specifically or broadly expressed antigens present on both patient hematopoietic cells and RCC cells. These observations provide the first insight into the immune mechanisms mediating the regression of metastatic cancer following non-myeloablative allogeneic transplantation. Using c-DNA expression cloning, we have recently identified a novel tumor antigen derived from a human endogenous retrovirus over expressed on RCC cells called CT-RCC. This antigen is not expressed on normal tissues and therefore could potentially serve as a target for a future kidney cancer vaccine. We are currently attempting to identify factors regulating expression of this newly identified tumor antigen. ? Recently we have developed a murine model of allogeneic SCT in hosts bearing metastatic RCC, in which reproducible GVT effects occur extending animal survival compared to recipients of autologous transplants. Post transplant tumor vaccination studies are being conducted in this model, as well as investigations into the impact of inhibiting angiogenesis in the first few months of transplantation using PDGF, VEGF, and EGF-R tyrosine kinase inhibitors. Our group has recently shown that KIR incompatible NK cells are cytotoxic to solid tumor cells in vitro. Using the above mentioned animal model, we have shown that a single infusion of alloreactive NK cells can significantly reduce GVHD and prolong survival in mice with RCC undergoing allogeneic HCT. Based on these findings, we plan to evaluate whether GVT effects aginanst RCC can be enhanced after allogeneic HCT by adoptively infusing escalating doses of donor NK cells. ? We are also exploring methods to sensitize solid tumors to NK cell attack by altering the phenotype of tumor cells through targeted gene induction. Recently we showed that bortezomib and depsipeptide sensitize tumors to NK cell cytotoxity by enhancing NK-cell mediated TRAIL killing. This sensitization appears to overcome NK inhibition that is mediated through KIR-KIR ligand interactions. We have also developed a method to expand by > 4 logs NK cells from healthy donors for adoptive infusion in future NK-Cell based adoptive immunotherapy trials. Based on these findings, this year we were awarded a 2 year bench to bedside award to scale up our NK cell expansions to test whether bortezomib could be used to sensitize patient's tumors to adoptive autologous NK cell infusions. ? Our group continues to explore the use of allogeneic SCT in patients with nonmalignant diseases such as PNH or ATGF-Refractory severe aplastic anemia. We have also recently shown that PNH can be cured following nonmyeloablative stem cell transplantation. In vitro studies conducted in our laboratory have shown PNH cells are equally sensitive to allogeneic immune attack as normal GPI-positive immune cells. At present, 29 patients with SAA/PNH have been transplanted with a day 100 TRM of 0%.
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