Quantitative Measurement of the mRNA Expression of the Tumor-Associated Antigen PRAME n
[4,6]. PRAME-specific cytotoxic T lymphocytes (CTL) could be generated. The
PRAME-specific CTL clone 17 (anti-LB33-E) recognizes a 9-mer peptide presented by HLA-A24 [4]. Recently, four different antigen epitopes of PRAME were
characterized. They were presented on HLA-A0201 and induced specific CTL
clones [12], thus indicating the immunogenic potential of PRAME. Therefore,
leukemia patients with high mRNA expression of PRAME are potential candidates for PRAME-specific cellular immunotherapy. No mRNA expression was
detected in peripheral mononuclear blood cells of healthy volunteers and in
CD34-positive cells of early hematopoiesis of healthy volunteers [6,7]. This characteristic of PRAME is of crucial importance for a PRAME-directed specific
immunotherapy. Immunotherapy should not damage other tissues or suppress
normal hematopoiesis in bone-marrow. Another potential target for immunotherapy in AML patients is the Wilms tumor antigen (Wt-l). Wt-l is a gene expressed
during embryonal cell differentiation and is correlated with a poor clinical prognosis in AML [13]. Wt -1 expression was described in 77% of AML patients but also
in CD34-positive selected cell samples [14]. CD34+ separated cell samples also
expressed Wt-l at high or moderate levels, so immunotherapy using Wt-l might
suppress hematopoiesis in these cases. Therefore, PRAME is the most interesting
target structure for immunotherapy in AML patients. Real-time RT -PCR using the
LightCycler SYBR Green I technology allows accurate quantification of PRAME
mRNA expression. The mRNA expression levels were correlated to the mRNA
expression of the house-keeping genes TBP and p-actin. TBP was expressed at a
more constant level than p-actin in samples of both healthy volunteers and tumor
patients. In this study, real-time RT-PCR analysis showed a sensitivity of PRAME
detection of one PRAME-positive AML cell in lxl0 5 normal PRAME-negative
mononuclear cells. Minimal residual disease of PRAME-positive malignant cells
of AML patients can be evaluated with LightCycler real-time RT-PCR during therapy like polychemotherapy or hematopoietic stem cell transplantation. In summary, PRAME may be a marker for minimal residual disease and a target for specific cellular immunotherapy in AML, providing both a diagnostic and a therapeutic tool.
References
1. Viola A, Lanzavecchia A (1996) T cell activation determined by T cell receptor number and
tunable thresholds. Science 273:104-106
2. Coulie PG, Lehmann F, Lethe B, Hermann J, Lurquin C,Andrawiss M, Boon T (1995) A mutated intron sequence codes for an antigenic peptide recognized by cytolytic T lymphocytes on
a human melanoma. Proc Natl Acad Sci 92:7976-7980
3. Chen YT, Scanlan MJ, Sahin U, Tiireci 0, Gure AO, Tsang S, Williamson B, Stockert E, Pfreundschuh M, Old LJ (1997) A testicular antigen aberrantly expressed in human cancers detected
by autologous antibody screening. Proc Natl Acad Sci 94:1914-1918
4. Ikeda H, Lethe B, Lehmann F, Van Baren N, Baurain JF, De Smet C, Chambost H, Vitale M, Moretta A, Boon T, Coulie PG (1997) Characterization of an antigen that is recognized on a melanoma
showing partial HLA loss by CTL expressing an NK inhibitory receptor. Immunity 6:199-208
5. Neumann E, Engelsberg A, Decker J, Stiirkel S, Jager E, Huber C, Seliger B (1998) Heterogeneous expression of the tumor-associated antigens RAGE-I, PRAME, and glycoprotein 7S in
[4,6]. PRAME-specific cytotoxic T lymphocytes (CTL) could be generated. The
PRAME-specific CTL clone 17 (anti-LB33-E) recognizes a 9-mer peptide presented by HLA-A24 [4]. Recently, four different antigen epitopes of PRAME were
characterized. They were presented on HLA-A0201 and induced specific CTL
clones [12], thus indicating the immunogenic potential of PRAME. Therefore,
leukemia patients with high mRNA expression of PRAME are potential candidates for PRAME-specific cellular immunotherapy. No mRNA expression was
detected in peripheral mononuclear blood cells of healthy volunteers and in
CD34-positive cells of early hematopoiesis of healthy volunteers [6,7]. This characteristic of PRAME is of crucial importance for a PRAME-directed specific
immunotherapy. Immunotherapy should not damage other tissues or suppress
normal hematopoiesis in bone-marrow. Another potential target for immunotherapy in AML patients is the Wilms tumor antigen (Wt-l). Wt-l is a gene expressed
during embryonal cell differentiation and is correlated with a poor clinical prognosis in AML [13]. Wt -1 expression was described in 77% of AML patients but also
in CD34-positive selected cell samples [14]. CD34+ separated cell samples also
expressed Wt-l at high or moderate levels, so immunotherapy using Wt-l might
suppress hematopoiesis in these cases. Therefore, PRAME is the most interesting
target structure for immunotherapy in AML patients. Real-time RT -PCR using the
LightCycler SYBR Green I technology allows accurate quantification of PRAME
mRNA expression. The mRNA expression levels were correlated to the mRNA
expression of the house-keeping genes TBP and p-actin. TBP was expressed at a
more constant level than p-actin in samples of both healthy volunteers and tumor
patients. In this study, real-time RT-PCR analysis showed a sensitivity of PRAME
detection of one PRAME-positive AML cell in lxl0 5 normal PRAME-negative
mononuclear cells. Minimal residual disease of PRAME-positive malignant cells
of AML patients can be evaluated with LightCycler real-time RT-PCR during therapy like polychemotherapy or hematopoietic stem cell transplantation. In summary, PRAME may be a marker for minimal residual disease and a target for specific cellular immunotherapy in AML, providing both a diagnostic and a therapeutic tool.
References
1. Viola A, Lanzavecchia A (1996) T cell activation determined by T cell receptor number and
tunable thresholds. Science 273:104-106
2. Coulie PG, Lehmann F, Lethe B, Hermann J, Lurquin C,Andrawiss M, Boon T (1995) A mutated intron sequence codes for an antigenic peptide recognized by cytolytic T lymphocytes on
a human melanoma. Proc Natl Acad Sci 92:7976-7980
3. Chen YT, Scanlan MJ, Sahin U, Tiireci 0, Gure AO, Tsang S, Williamson B, Stockert E, Pfreundschuh M, Old LJ (1997) A testicular antigen aberrantly expressed in human cancers detected
by autologous antibody screening. Proc Natl Acad Sci 94:1914-1918
4. Ikeda H, Lethe B, Lehmann F, Van Baren N, Baurain JF, De Smet C, Chambost H, Vitale M, Moretta A, Boon T, Coulie PG (1997) Characterization of an antigen that is recognized on a melanoma
showing partial HLA loss by CTL expressing an NK inhibitory receptor. Immunity 6:199-208
5. Neumann E, Engelsberg A, Decker J, Stiirkel S, Jager E, Huber C, Seliger B (1998) Heterogeneous expression of the tumor-associated antigens RAGE-I, PRAME, and glycoprotein 7S in