Flow cytometry of p53 protein expression in some hematological malignancies

p53 is a armor suppressor gene encoding a nuclear phosphoprotein that plays an important role in the control of normal cell proliferation. We have tri ed to establish the value of the p53 protein expression in peripheral blood (PB) and/or bone marrow (BM) cells of patients with some hematological mal ignancies. A recently developed fixation/permeabilization method was modifi ed for flow cytometric assessment of p53 protein expression using two anti- pS3 monoclonal antibodies. p53 quantitation expressed as molecules of equiv alent soluble fluorochrome per cell (MESF) providing valuable data contribu ting to a more precise definition of leukemic cells, was also applied. Our findings showed higher percentage of p53 expression in cells of AML pat ients at the time of diagnosis opposite to the controls. These data, in ass ociation with immophenotype of cells, accompanied diagnosis of relapse or d efinition of remission after allogeneic BM transplantation. We observed als o elevated levels of p53 protein at initial diagnosis diagnosis fearly B-AL L. According to our results quantitation of p53 protein allows better chara cterization of selected population of BM cells and should be used for the m onitoring of blast persistence during and after therapy and might also be o ne of the methods to indicate early relapse. Percentage of p53 protein posi tivity varied in our group of B-CLL patients tested in connection with prog ression of disease. We documented also one case of Burkitt's lymphoma with high percentage of p53 positivity. Measurement of p53 protein expression by flow cytometry may be of clinical importance by indicating levels of positivity. Our results suggest, that p5 3 alteration is frequently involved at initial diagnosis of AML, in some T- cell disorders and on the contrary more frequently during early B-ALL relap se, in advanced stages of B-CLL and in Burkitt's lymphoma. p53 protein quan titation is of value to ascertain malignancy and provides additional parame ter suitable for the evaluation of residual disease: and for the monitoring of therapy.