Stepwise genetic changes associated with progression of nontumorigenic HPV-18 immortalized human prostate cancer-derived cell line to a malignant phenotype

Cytogenetics, fluorescence in situ hybridization (FISH), and comparative ge nomic hybridization (CGH) were used to identify genes that are involved in the development and progression of prostate cancer. For that purpose, we ch ose a cell line established in vitro from a prostatic adenocarcinoma which was nontumorigenic in nude mice and followed its progression to a tumorigen ic cell line. Stepwise changes were observed in the cell line as it became tumorigenic. The composite karyotype at the nontumorigenic stage (CA-HPV-10 ) was 68 similar to 77,XXY, -(1, 9, 13, 14, 19, 22),+(4, 5, 11, 18, 20, 21) ,+ (del(1) (q23q31)=M1 (two copies), + der(9)t(1;9)(q24 similar to q31;p23) = M5(two copies),der(14)t(14;?)(q10;?) = M17 in the majority of metaphases . These two derivative chromosomes were also observed a previous study. Our CGH analysis clearly showed that this deleted region in M1 is, in fact, tr anslocated with derivative M5 and, in reality, is amplified. The cell line established from nodule (SCID 5029 p11, showed a number of new changes, as described; however, the most significant change was amplification of the 8q 23 similar to qter region, harboring c-myc. This region was translocated wi th chromosomes 2, 4, and 16 as der(2) t(2;8)(q33;q23)=M12, der(4)t(4;8)(q34 ;q23)=M11, and der(16)t(8;16)(q24;q21)=M9. We deduce from our study that am plification of c-myc and other genes in the 8q23 similar to qter region wer e important in progression but did not lead to tumorigenicity. The populati on that became tumorigenic (SCID 5019 II) showed almost all of the same cha nges in the karyotype as observed in the nodular cell line; the only signif icant change was the appearance of der(11)t(4;11)(q32;q22)=M7 and the addit ion of another copy of t(3q;7p)=M2. These new changes lead to loss of chrom osomes 3p, 4pter similar to q34, 6, 7q21 similar to qter, 11q22 similar to qter, and 18q, and gain of 3q, 7p, 8q23 similar to qter, and 11pter similar to q22, before the cell line became tumorigenic. The clonal selection of t he population is proven by the presence of a number of the same derivative chromosomes in both the nodular and tumorigenic cell line. As it progressed to tumorigenicity, some of the same changes observed in the original study re-appear at different stages of malignancy, although it was absent in the nontumorigenic cell line. These are: der(16)t(8;1 6)(q24;q21)=M9 in the no dular cell line and der(11)t(4;11)(q32;q22)=M7 in the tumorigenic cell line . In our system, amplificafion of c-myc and other genes in der(2)t(2;8)(q33 ;q23) =M12, der(4) t(4;8)(q34;q23= M11 together with the presence of der(16 )t(8;16)(q24;q21)=M9 and der(11)t(4;11)(q32;q22)=M5 makes the cell line tum origenic. It is either nontumorigenic, with the presence of a marker equiva lent to der(16)=M9 and der(11)=M7 observed in the original study, and only nodular (SCIL) 5019 p11, present study), with the presence of number of mar kers with c-myc amplification (M9, M11, and M12). There is accumulation of all the above-mentioned changes in the same cell before it becomes tumorige nic. (C) 2000 Elsevier Science Inc. All rights reserved.