Further Studies on Karyotypes of a Variety of Primary and Transplanted Mouse Polyoma Tumors2

Abstract

Karyologic studies were made on 5 primary and 18 transplanted tumors induced by polyoma virus in mice. Sixteen tumors were characterized by stemlines, which were changed chromosomally and most often different for each neoplasm, while 7 tumors, 1 of which was primary, contained cells with the normal diploid number of 40 as their stemline and did not show any detectable structural modifications. Four diploid tumors, followed through several passages, became aneuploid. On the other hand, aneuploid stemlines generally remained constant during prolonged propagation in vivo. All tumors varied considerably around the stemline chromosome numbers. The results show that such chromosomal changes cytologically detectable in telocentric mouse chromosomes are not prerequisite for the neoplastic transformation by the polyoma virus, but apparently often give the cells selective advantage. No systematic chromosome changes distinguished polyoma tumors from tumors where no viral etiology is known.