A novel B-CLL specific nuclear protein (p44/46)

Changes in leukemic cell nuclei revealed by differential scanning calorimetry

Using differential scanning calorimetry we analyzed the thermal profiles of nuclei from normal and B-cell chronic lymphocytic leukemia mononuclear cells. Intact nuclear fraction of normal mononuclear cells is characterized by four thermal transitions, i.e., at 60, 70, 83 and 103 degrees C. Leukemic nuclear samples revealed the transitions at 67 and 83 degrees C, however, in more aggressive stage of the disease additional thermal peaks at 76 and 93 degrees C were observed. Our very preliminary results revealed that mononuclear cell nuclear fraction from blood of patients responding to the used therapy, i.e., cladribine alone or its combination with mitoxantrone and cyclophosphamide indicates decrease (or even loss) of transition at 93 degrees C concomitant with increase of transition at 76 degrees C. A complementary study showed that in mononuclear cells of patients who appeared to be sensitive to chemotherapy the decrease of antiapoptotic Bcl-2 protein expression and signs of apoptotic morphology were observed.

CD23 is recognized as tumor-associated antigen (TAA) in B-CLL by CD8+ autologous T lymphocytes

OBJECTIVE

CD23 is constitutively and atypically expressed on malignant B cells in patients with chronic lymphocytic leukemia (B-CLL). Here, we investigated whether CD23-derived peptides might function as B-CLL-specific tumor-associated antigen (TAA).

PATIENTS AND METHODS

Using IFN-gamma-ELISPOT assays and HLA-A2/dimer-peptide staining we identified autologous, CD23-specific HLA-A0201-restricted T cells after 4 weeks of in vitro culture.

RESULTS

We were able to expand autologous T cells from 8/11 B-CLL patients by using native and CD40L-activated B-CLL cells as antigen-presenting cells (APCs) in 5 cases whereas for 3 samples an autologous T cell response could only be evoked by use of CD40L-stimulated B-CLL cells as APCs. The number of CD8(+) T cells could be expanded during 4 weeks of in vitro culture with native or CD40L-activated B-CLL cells. We could demonstrate that the expanded T cells were also able to secrete IFN-gamma upon recognition of the antigen using IFN-gamma-ELISPOT assays. Furthermore, these T cells not only recognized HLA-A0201-binding CD23-derived peptides presented by T2 cells, but also CD23-overexpressing autologous B-CLL cells in an MHC-I-restricted manner.

CONCLUSION

In sum, CD23-derived peptides were shown to be naturally processed and presented as TAA in primary B-CLL, enabling the expansion of autologous tumor-specific T cells.

Human Ly9 (CD229) as novel tumor-associated antigen (TAA) in chronic lymphocytic leukemia (B-CLL) recognized by autologous CD8+ T cells

OBJECTIVE

CD229, a cell-surface molecule being involved in cell adhesion, is overexpressed in B-CLL cells. In this study we wanted to explore whether CD229 might function as B-CLL-specific tumor-associated antigen (TAA).

PATIENTS AND METHODS

Autologous, CD229-specific HLA-A2-restricted T cells were identified using IFN-gamma-ELISPOT assays and HLA-A2/dimer-peptide staining after 4 weeks of in vitro culture.

RESULTS

We were able to expand autologous T cells from 9/11 B-CLL patients using native B-CLL cells as antigen presenting cells (APCs) in 5 cases, whereas for 4 samples an autologous T-cell response could only be evoked by use of CD40L-stimulated B-CLL cells as APCs. The number of CD8+ T cells could be expanded during 4 weeks of in vitro culture with native or CD40L-activated B-CLL cells while the amount of specific T cells recognizing CD229 peptides bound to HLA-A2 dimers increased on average 12-fold (native CLL) and 13-fold (CD40L-activated CLL), respectively. Using IFN-gamma-ELISPOT assays we could demonstrate that the expanded T cells were able to secrete IFN-gamma upon recognition of the antigen. These T cells not only recognized HLA-A0201-binding CD229-derived peptides presented by T2 cells, but also CD229-overexpressing autologous B-CLL cells in an MHC-I-restricted manner.

CONCLUSION

In summary, CD229 was shown to be naturally processed and presented as TAA in primary B-CLL cells, enabling the expansion of autologous tumor-specific T cells.

Altered expression of nuclear non-histone protein (p44/46) in different stages of B-chronic lymphocytic leukemia

Our previous data have shown some differences in electrophoretic characteristics of proteins from cellular fractions (nuclear, mitochondrial, microsomal and cytosolic) isolated from peripheral blood mononuclear cells of B-cell chronic lymphocytic leukemia (B-CLL), acute lymphoblastic leukemia (ALL) patients and healthy donors. The main differences were found in electrophoretic patterns of nuclear proteins from normal and leukemia cells, especially in the nuclear mass regions of 36-52, 58-85, and 120-180 kDa. Electrophoretically-specific nuclear non-histone protein in the molecular mass zone 44/46 kDa of cells obtained from the peripheral blood of a B-CLL patient was used to produce rabbit polyclonal antiserum. SDS-polyacrylamide gel electrophoresis as well as immunological techniques (Western blot and immunocytochemistry) indicate that the nuclear protein with a molecular mass of 44/46 kDa is specifically expressed in mononuclear cells from B-CLL patients. The expression of this particular nuclear protein seems to correlate with the progression of the leukemia.