INCREASED EXPRESSION OF C-MYC P67 ONCOPROTEIN IN PATIENTS WITH MYELODYSPLASTIC SYNDROMES IN TRANSFORMATION TO ACUTE-LEUKEMIA

Thirty-five patients, 24 males and 11 females, with myelodysplastic sy ndromes were studied for the expression of c-myc encoded p67 oncoprote in. According to FAB classification, 5 patients had refractory anaemia (RA), 5 refractory anaemia with ringed sideroblasts (RARS), 17 refrac tory anaemia with excess of blasts (RAEB), 4 refractory anaemia with e xcess of blasts in transformation (RAEB-t), and 4 chronic myelomonocyt ic leukaemia (CMML). The mouse anti-human 9E10 derived monoclonal anti body in the standard APAAP technique for immunohistochemical analysis was used. A scoring method similar to that routinely used for endogeno us neutrophil alkaline phosphatase estimation, was applied to obtain p arametrically comparable results. In all but two MDS patients, the obs erved c-myc oncoprotein score values did not differ statistically from those found in the controls. The values did not correlate with periph eral blood or bone marrow blast cell numbers. In two out of 17 patient s with RAEB in whom very high c-myc score values were found, acute non -lymphocytic leukaemia (ANLL) was diagnosed 30 and 45 days later, resp ectively. Furthermore, we found high c-myc score values in three patie nts with RAEB and in two patients with RAEB-t during the ANLL phase wh ich was diagnosed six to ten months after the initial study. Our data suggest that c-myc activation may be seen in all cases of MDS in overt ANLL phase, and also in some RAEB patients a few weeks before diagnos is of overt ANLL. The possible prognostic value of c-myc activation in MDS patients remains to be clarified.