[Value of rhodamine 123 in the detection of minor amounts of multidrug resistant cells]. / Intérêt de la rhodamine 123 pour la détection de faibles proportions de cellules multichimiorésistantes.

The neoplasias resistance to chemotherapy is mainly due to multidrug resistance phenomenon (MDR) mediated by an ATP-dependent efflux pump called P-glycoprotein. This function can be reversed by many multidrug reversing agents so numerous chemotherapy regimens have been initiated in malignancies. To make sure the success of these protocols it is necessary to detect as soon and as certain as possible the presence of resistant cells among malignant population. We have chosen to evaluate functional test using rhodamine 123 in this aim in view. We have made various mixtures of resistant ans sensitive cells of three cell lines. Rhodamine 123 allows to detect 1% of resistant cells among sensitive cells. Influence of dead cells on the interpretation is discussed.

Immunophenotype of a transient myeloproliferative disorder in a newborn with trisomy 21.

Cytologic, immunologic, and cytogenetic studies were performed on the blast cells of a newborn with Down syndrome and transient myeloproliferative disease. This hematologic disorder is uncommon, and occurs primarily in infants with Down syndrome. This boy presented with a high white blood cell count and a high percentage of blast cells, without anemia or thrombocytopenia. Chromosome analysis showed a constitutional trisomy 21 without any other clonal abnormality. A three-color flow cytometric analysis was performed and revealed two different CD45 dim, CD34(+), CD117(+), CD56(+) immature subpopulations: the normal immature myeloid precursor and an immature blast cell population that expressed CD41, CD42, CD61, CD36, CD13, CD1a, and CD2. We postulate that this population could be the leukemic precursor involved in the acute megakaryoblastic leukemia frequently observed in children with Down syndrome.