Durable remission of renal cell carcinoma in conjuncture with graft versus host disease following allogeneic stem cell transplantation and donor lymphocyte infusion: rule or exception?

Allogeneic stem cell transplantation (alloSCT) followed by donor lymphocyte infusion (DLI) can be applied as immunotherapeutic intervention to treat malignant diseases. Here, we describe a patient with progressive metastatic clear cell renal cell carcinoma (RCC) who was treated with T cell depleted non-myeloablative alloSCT and DLI resulting in disease regression accompanied by extensive graft versus host disease (GVHD). We characterized the specificity of this immune response, and detected a dominant T cell population recognizing a novel minor histocompatibility antigen (MiHA) designated LB-FUCA2-1V. T cells specific for LB-FUCA2-1V were shown to recognize RCC cell lines, supporting a dominant role in the graft versus tumor (GVT) reaction. However, coinciding with the gradual disappearance of chronic GVHD, the anti-tumor effect declined and 3 years after alloSCT the metastases became progressive again. To re-initiate the GVT reaction, escalating doses of DLI were given, but no immune response could be induced and the patient died of progressive disease 8.5 years after alloSCT. Gene expression studies illustrated that only a minimal number of genes shared expression between RCC and professional antigen presenting cells but were not expressed by non-malignant healthy tissues, indicating that in patients suffering from RCC, GVT reactivity after alloSCT may be unavoidably linked to GVHD.

Detection of CEBPA double mutants in acute myeloid leukemia using a custom gene expression array.

Double (bi-allelic) mutations in the gene encoding the CCAAT/enhancer-binding protein-alpha (CEBPA) transcription factor have a favorable prognostic impact in acute myeloid leukemia (AML). Double mutations in CEBPA can be detected using various techniques, but it is a notoriously difficult gene to sequence due to its high GC-content. Here we developed a two-step gene expression classifier for accurate and standardized detection of CEBPA double mutations. The key feature of the two-step classifier is that it explicitly removes cases with low CEBPA expression, thereby excluding CEBPA hypermethylated cases that have similar gene expression profiles as a CEBPA double mutant, which would result in false-positive predictions. In the second step, we have developed a 55 gene signature to identity the true CEBPA double-mutation cases. This two-step classifier was tested on a cohort of 505 unselected AML cases, including 26 CEBPA double mutants, 12 CEBPA single mutants, and seven CEBPA promoter hypermethylated cases, on which its performance was estimated by a double-loop cross-validation protocol. The two-step classifier achieves a sensitivity of 96.2% (95% confidence interval [CI] 81.1 to 99.3) and specificity of 100.0% (95% CI 99.2 to 100.0). There are no false-positive detections. This two-step CEBPA double-mutation classifier has been incorporated on a microarray platform that can simultaneously detect other relevant molecular biomarkers, which allows for a standardized comprehensive diagnostic assay. In conclusion, gene expression profiling provides a reliable method for CEBPA double-mutation detection in patients with AML for clinical use.

Self-tolerance does not restrict the CD4+ T-helper response against the p53 tumor antigen.

Tumorigenesis is frequently associated with mutation and overexpression of p53, which makes it an attractive target antigen for T cell-mediated immunotherapy of cancer. However, the magnitude and breadth of the p53-specific T-cell repertoire may be restricted due to the ubiquitous expression of wild-type p53 in normal somatic tissues. In view of the importance of the CD4+ T-helper cell responses in effective antitumor immunity, we have analyzed and compared the p53-specific reactivity of this T cell subset in p53+/+ and p53-/- C57Bl/6 mice. This response was found to be directed against the same three immunodominant epitopes in both mouse types. Fine-specificity, magnitude, and avidity were not affected by self-tolerance. Immunization of p53-/- and p53+/+ mice with synthetic peptide vaccines comprising the identified epitopes induced equal levels of Th1 immunity. Our findings imply that the p53-specific CD4+ T-cell repertoire is not restricted by self-tolerance and is fully available for the targeting of cancer.