Cytogenetic changes during tumor progression towards invasion, metastasis and immune escape in the Eb/ESb model system

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Abstract
Related tumor lines which represent different stages in their progression towards metastatic capacity were investigated and compared at the chromosomal level. The parental low‐metastatic tumor line (L5178Y/Eb) was derived from a long‐term transplanted, chemically induced T‐cell lymphoma of the DBA/2 mouse. The cytogenetic analysis included this Eb line, a spontaneous high metastatic variant thereof which expressed a distinct tumor‐associated transplantation antigen (ESb TATA+), and an immunoresistant TATA‐negative variant of the latter (ESb TATA−). All three cell lines were characterized by a near‐diploid chromosome count and by some common chromosomal markers derived from Nos. 6, 13 and 16 Large‐scale chromosomal rearrangments resulted in the formation of eight marker chromosomes in Eb cells, 16 in ESb TATA+ cells and 18 in ESb TATA− cells. Tumor progression in this system showed a tendency to monosomies, which could bring the corresponding genes to a hemizygous state and possibly to a release from repression. Chromosome 15 was trisomic in Eb cells, monosomic in ESb TATA+ cells and hardly detectable in ESb TATA− cells. The Ig heavy‐chain gene‐carrying region of both chromosomes No. 12 was found in translocation with chromosomes Nos. 5, 13 and 14 (Eb cells) and with Nos. 1 and 17 (ESb cells). ESb TATA− cells differed from ESb TATA+ cells at four different chromosomes (Nos. 5, 8, 14 and 15).