Genetic evolution in colon cancer KM12 cells and metastatic derivates

Abstract

So far, CRC cell lines have contributed to descriptions of 2 patterns of genetic instability, affecting either microsatellite sequences or chromosome number and structure. Often, these patterns are mutually exclusive; while near-diploid karyotypes usually appear with MSI and chromosomal stability, near-triploid or tetraploid cells display a high degree of CIN and are stable at the microsatellite level. In the present study, we describe the genomic instability pattern of KM12 CRC cells. KM12C and derived cell lines with different metastatic properties were analyzed by conventional cytogenetics, CGH and M-FISH. Results were compared to 5 cell lines usually used as model of MSI and CIN. Concordance between our results and previously published SKY data are also reviewed. Interestingly, the poorly metastatic KM12C cell line displayed a near-diploid karyotype with high levels of structural chromosome instability and microsatellite instability. Most carcinomas show highly complex karyotypes, suggesting that one of the tumor-development events may be related to genomic instability. 1,2 Up to now, MSI has been the only type of genomic instability well characterized in a minority of tumors (about 15% of sporadic CRCs). These tumors show a deficiency in mismatch repair genes with a replication error phenotype and a stable near-diploid karyotype. 3-7 chromosome instability has been described in some CRC cell lines, resulting in numerical changes 8 (CIN) or structural rearrangements. 9 Often, these patterns are mutually exclusive; while near-diploid karyotypes usually appear with MSI and chromosome instability, near-triploid or tetraploid cells display a high degree of CIN and are stable at the microsatellite level.It has been postulated that primary alterations in solid tumors consist of submicroscopic mutations, whereas unbalanced chromosomal rearrangements, whether numerical or structural, are secondary events and most likely associated with selective pressures during tumor progression. 10 A previous report demonstrated clonal chromosomal aberrations in 87% of CRC tumors analyzed. 11 The most frequent numerical changes were, in order of decreasing frequency, ϩ7, -18, -14, ϩ13. Gain of chromosome 8q and loss of 8p, loss of 17p and gain of 17q as well as loss of the entire chromosome 22 are also unbalanced rearrangements that have been reported. 11 Based on cytogenetic alterations, Dutrillaux 12 proposed 3 different evolutionary pathways: monosomic-type tumors undergo structural rearrangements resulting in gains and losses of different chromosome arms and show a relatively high rate of endoreduplication, leading to the formation of hypotetraploid clones that evolve to near-triploid cells; trisomic cells are characterized by tumors with a progressive increase in chromosome number but accompanied by a scarce number of rearrangements; tumors that display a near-normal karyotype and MSI were grouped into the normal type. Unbalanced chromosomal abnormalities would be secondary events and most likely associated with selective pre...

Genetic determinants of methotrexate responsiveness and resistance in colon cancer cells

“…Three cell lines (DLD-1, LoVo and HCT116) showed a neardiploid karyotype with a few structural alterations, in agreement with previous studies (Lengauer et al, 1998;Masramon et al, 2000;Abdel-Rahman et al, 2001;Camps et al, 2004). All three exhibited MSI.…”

“…Another three cell lines (HT-29, SW480 and SK-CO-1) were aneuploid and showed multiple chromosomal reorganizations. The remaining three cell lines (KM12C, KM12SM and KM12L4A) showed a complex karyotype (KM12C showed a near-diploid DNA content and the two derivatives KM12SM and KM12L4A were near-tetraploid) and constitute the first model in which both chromosomal and MSI coexist (Camps et al, 2004). A summary of the main features of each cell line is shown in Table 1.…”

“…Western Blot methods are described in Supplementary Information cells or that other, more efficient, mechanism(s) of drug resistance were available. Interestingly, KM12 cell lines are a rare example of coexistence of chromosomal instability and MSI (Camps et al, 2004). Since all the cell lines displaying MSI developed resistance, it can be hypothesized that this type of instability is a dominant characteristic over the amplification mechanism.…”

CCAT2, a novel noncoding RNA mapping to 8q24, underlies metastatic progression and chromosomal instability in colon cancer

“…2B). To validate the role of CCAT2 in the metastatic phenotype, we used KM12SM cells, a CRC cell line established from the spontaneous liver metastasis of KM12C cells (Camps et al 2004). Knockdown of CCAT2 by siRNA, which reduced the CCAT2 expression by 70%, significantly reduced the invasive ability of KM12SM cells (that express high levels of CCAT2), suggesting the involvement of CCAT2 in metastasis ( Fig.…”

Knockdown of peroxisome proliferator-activated receptor-β induces less differentiation and enhances cell–fibronectin adhesion of colon cancer cells

“…Compared with KM12C, both the number and rate of chromosomal gains and losses increase in KM12SM and KM12L4a cell lines. The KM12L4a cell line, which was established by four selection cycles, has more genetic alterations than does the KM12SM cell line, which was only selected once (Camps et al, 2004). Although the chromosome portion (6p21.1-21.2) encoding PPAR-b is not altered in these cell lines, the activity of the PPAR-b gene may be affected by these genetic changes, which possibly underlies the different degrees of influence of PPAR-b on the three cell lines.…”