Immunoglobulin light chain, Blimp-1 and cytochrome P4501B1 peptides as potential vaccines for AL amyloidosis.

Amyloid light chain (AL) amyloidosis is a lethal disorder characterized by the pathologic deposition of clonal plasma cell-derived, fibrillogenic immunoglobulin light chains in vital organs. Current chemotherapeutic regimens are problematic in patients with compromised organ function and are not effective for all patients. Here, a platform of computer-based prediction and preclinical mouse modeling was used to begin development of a complementary, immunotherapeutic approach for AL amyloidosis. Three peptide/MHC I-binding algorithms identified immunogenic peptides from three AL plasma cell-associated proteins: (1) amyloidogenic λ6 light chains, (2) CYP1B1, a universal tumor antigen hyper-expressed in AL plasma cells and (3) B lymphocyte-induced maturation protein 1 (Blimp-1), a transcription factor required for plasma cell differentiation. The algorithms correctly predicted HLA-A(*)0201-binding native and heteroclitic peptides. In HLA-A2 transgenic mice, these peptides, given individually or in combination, induced potent CTL which kill peptide-loaded human lymphoma cells and/or lymphoma cells producing target protein. Blimp-1 peptide-immunized mice exhibited a reduced percentage of splenic, lymph node and bone marrow plasma cells and a decrease in the absolute number of splenic plasma cells demonstrating (1) presentation of target peptide by endogenous plasma cells and (2) appropriate CTL homing to lymphoid organs followed by killing of target plasma cells. These studies suggest that AL amyloidosis, with its relatively low tumor cell burden, may be an attractive target for peptide-based multivalent vaccines.

Dysregulation of miRNAs in AL amyloidosis.

Bone marrow plasma cells (BMPCs) were purified using anti-CD138 immunomagnetic beads, from aspirates obtained with permission of the Boston University Medical Campus Institutional Review Board, from patients with immunoglobulin light chain (AL) amyloidosis and from controls. Expression levels of MicroRNAs (miRNAs) were compared by microarray; 10 were found to be increased more than 1.5-fold. These results were confirmed using stem-loop RT-qPCR for the most highly upregulated miRNAs, miR-148a, miR-26a, and miR-16. miR-16, a micro-RNA linked to other hematopoietic diseases, was significantly increased in the AL group at diagnosis, and also in treated patients with persistent monoclonal plasma cells in the bone marrow, but not in patients who achieved a hematologic remission after therapy. miR-16 can be derived from the miR-16-1/mirR-15, a cluster on chromosome 13 or the miR-16-2/miR-15b cluster on chromosome 3. The expression of miR-15b was much higher than miR-15a in both AL and control BMPC, suggesting that miR-16 in plasma cells is mainly derived from miR-16-2/miR-15b. The anti-apoptosis gene BCL-2, a putative target mRNA that can be downregulated by miR-16, was expressed in BMPCs from AL patients, despite elevated levels of miR-16. Our data suggests that miRNAs are dysregulated in clonal plasma cells in AL amyloidosis and may be potentially useful as biomarkers of disease.

PTEN blocks insulin-mediated ETS-2 phosphorylation through MAP kinase, independently of the phosphoinositide 3-kinase pathway.

The tumor suppressor PTEN possesses lipid and protein phosphatase activities. It has been well established that the lipid phosphatase activity is essential for its tumor-suppressive function via the phosphoinositide 3-kinase (PI3K) and Akt pathways. The precise role of the protein phosphatase activity is still unclear. In the current study, we demonstrate that overexpression of wild-type PTEN in the MCF-7 breast cancer line results in phosphatase activity-dependent decreases in the phosphorylation of ETS-2, which is a transcription factor whose DNA-binding ability is controlled by phosphorylation. Exposure of MCF-7 cells to insulin, insulin-like growth factor 1 (IGF-1) or epidermal growth factor (EGF) can lead to the phosphorylation of ETS-2, Akt and ERK1/2. The MEK inhibitor PD590089 abrogates insulin-stimulated phosphorylation of ETS-2. In contrast, the PI3K inhibitor LY492002 has no effect on insulin-stimulated phosphorylation of ETS-2, despite the fact that it diminishes insulin-stimulated phosphorylation of Akt. Interestingly, overexpression of PTEN in MCF-7 leads to blockade of insulin-stimulated, but not EGF-stimulated, phosphorylation of ERK, accompanied by dramatic decreases in ETS-2 phosphorylation. We further show that the relationship of PTEN and ETS-2 has functional significance by demonstrating that PTEN abrogates activation of the uPA Ras-responsive enhancer, a target of ETS-2 action, in a phosphatase-dependent manner, irrespective of the presence or absence of insulin. Our observations, therefore, suggest that PTEN blocks insulin-stimulated ETS-2 phosphorylation through inhibition of the ERK members of the MAP kinase family independently of PI3K, and that the PTEN effect on the phosphorylation status of ETS-2 may be mediated through PTEN's protein phosphatase activity.