CYTOLOGICAL EVIDENCE FOR SINGLE-CELL ORIGIN OF TUMORS INDUCED WITH 3-METHYLCHOLANTHRENE IN FEMALE MICE CARRYING CATTANACH'S TRANSLOCATION

Abstract

Chromosome studies were carried out on 12 tumors induced by subcutaneous injection of 0.005-0.5mg of 3-methylcholanthrene in female mice carrying Cattanach's X-autosome translocation. Using the asynchronously replicating (hence genetically inactive) X chromosome as a marker, we obtained evidence showing that most or all of these tumors were monoclonal in origin. A single case, in which cell fusion occurred early in tumorigenesis, demonstrated that simultaneous expression of two different X chromosomes is not always incompatible with monoclonality.