Distinct karyotypes in three breast cancer cell lines — 21PTCi, 21NTCi, and 21MT-1 — derived from the same patient and representing different stages of tumor progression

Three breast carcinoma cell lines — 21PTCi, 21NTCi, and 21MT-1 — all originating from a 36-year-old woman with metastatic breast cancer, have been characterized previously as stably representing different stages of progression: (nontumorigenic [21PTCi]; tumorigenic, nonmetastatic [21NTCi]; and tumorigenic, weakly metastatic [21MT-1]). These cell lines were investigated for cytogenetic characteristics using G-banding and spectral karyotyping. All three cell lines have multiple chromosome aberrations, but they differ in the types of rearrangements and breakpoints. 21PTCi cells have a modal number (mn) of 56, with 55 types of aberrations, including 16 numeric and 39 structural. 21NTCi cells have a mn of 56, with 70 types of aberrations, including 19 numerical and 51 structural. Finally, 21MT-1 cells have a mn of 54, with 43 types of aberrations, including 14 numerical and 29 structural. The most common rearrangements differ in each cell line [i.e., der(X)t(X;3), der(4)t(1;4), del(6q) and der(19)t(17;19)(q11.2;q13.4) in 21PTCi; der(4)t(1;4), der(12)t(12;15) and –16 in 21NTCi; and der(1)t(1;10), +5, der(6)t(6;7), der(11)t(11;13), –20, and der(20)t(20;21) in 21MT-1]. This cytogenetic result is consistent with previous findings in that the three cell lines represent different stages of tumor progression. We hypothesize that the cytogenetic changes in these cell lines may be related to their distinct biologic characteristics. These three cell lines, with their different karyotypes and biologic characteristics, provide a vital tool for further study of the genetic and epigenetic events involved in transitions between premalignant and malignant phenotypes.