REVIEW: Differentiation Mechanisms and Malignancy
G. I. Abelev
Institute of Carcinogenesis, Blokhin Cancer Research Center, Russian
Academy of Medical Sciences, Kashirskoe Shosse 24, Moscow, 115478
Russia; fax: (7-095) 324-1205; E-mail:
abelev@mx.iki.rssi.ru
Received September 17, 1999
This review considers the relationship between differentiation
mechanisms and the genesis and maintenance of tumor phenotype. To a
certain extent, carcinomas preserve differentiation markers of normal
tissue, and hemoblastoses precisely reflect the direction and
differentiation level of their precursor cells. Both tumor types retain
the ability to differentiate. Mechanisms of T and B cell
differentiation are reviewed considering the activation of
protooncogenes by translocation to the region of tissue-specific genes
including the immunoglobulin (Ig) and T cell receptor (TCR) genes.
Apart from the classical oncogenes (MYC, PRAD, BCL-2), heterologous
differentiation of trans-factors can be activated in a similar
manner. Their activation at inappropriate time and place induces
oncogenic transformation in a number of hemoblastoses. Chimeric genes
and fused proteins are analyzed, including their genesis by specific
translocation resulting in transformation and their role in
differentiation and maintenance of the tumor phenotype. Induction of
terminal differentiation in leukemia can have significant therapeutic
effect. These hemoblastoses include hairy cell leukemia, promyelocytic
leukemia, and in part chronic myeloid leukemia. Specific attention is
given to the role of intercellular interactions in the control of tumor
growth and maintenance of a differentiated state of the cells. It is
suggested that alterations in these interactions during tumor
progression simultaneously stimulate malignant growth and decrease
differentiation level, thus inducing re-expression of embryonic
antigens in the tumors.
KEY WORDS: differentiation in tumors, translocation in
hemoblastoses, tumor progression, extracellular matrix, re-expression
of alpha-fetoprotein in hepatomas