The majority of ovarian cancer patients are treated with platinum-based chemotherapy, but the emergence of resistance to such chemotherapy severely limits its overall effectiveness. We have shown that development of resistance to this treatment can modify cell signaling responses in a model system wherein cisplatin treatment has altered cell responsiveness to ligands of the erbB receptor family. A cisplatinresistant ovarian carcinoma cell line PE01 CDDP was derived from the parent PE01 line by exposure to increasing concentrations of cisplatin, eventually obtaining a 20-fold level of resistance. Whereas PE01 cells were growth stimulated by the erbB receptor-activating ligands, such as transforming growth factor-A (TGFA), NRG1A, and NRG1B, the PE01 CDDP line was growth inhibited by TGFA and NRG1B but unaffected by NRG1A. TGFA increased apoptosis in PE01 CDDP cells but decreased apoptosis in PE01 cells. Differences in extracellular signal-regulated kinase and phosphatidylinositol 3-kinase signaling were also found, which may be implicated in the altered cell response to ligands. Microarray analysis revealed 51 genes whose mRNA increased by at least 2-fold in PE01 CDDP cells relative to PE01 (including FRA1, ETV4, MCM2, AXL, MT3, TRAP1, and FANCG), whereas 36 genes (including IGFBP3, TRAM1, and KRT4 and KRT19) decreased by a similar amount. Differential display reverse transcriptase-PCR identified altered mRNA expression for TCP1, SLP1, proliferating cell nuclear antigen, and ZXDA. Small interfering RNA inhibition of FRA1, TCP1, and MCM2 expression was associated with reduced growth and FRA1 inhibition with enhanced cisplatin sensitivity. Altered expression of these genes by cytotoxic exposure may provide survival advantages to cells including deregulation of signaling pathways, which may be critical in the development of drug resistance. (Cancer Res 2005; 65(15): 6789-800)

Two ovarian cell lines were derived from the ascites of a patient before and after the onset of resistance to chemotherapy involving cis-platinum, chlorambucil and 5-fluorouracil. Characterization of these lines shows them to have various features in common and some significant differences. Cytologically the lines cannot be distinguished and they both contain high concentrations of oestrogen receptor. However, they do differ with respect to their growth characteristics, karyotype, glutathione content and sensitivity to cis-platinum. The karyotypes of the 2 lines show several marker chromosomes in common but the resistant line contained a chromosome 8 and a 17 which were absent from the earlier sensitive line. This suggests a clonal origin with subsequent divergence to a heterogeneous population.

Human tumor cell lines have provided valuable model systems to study a wide variety of tumor characteristics including the cell biology, genetics, and chemosensitivity profiles of disease. A large number of ovarian cancer cell lines have now been established and are in widespread use Table 1) (1-15). Many of these have been selected to reflect specific situations, e.g., pre- and postchemotherapy models or different histo- logical subtypes. Table 1 Properties of Established Ovarian Carcinoma Cell Lines Prior Cell Line Histology Source Treatment Ref. PE01 P.D. Serous adenoca Ascites P/FU/CHL 1 PE04 P.D. Serous adenoca Ascites P/FU/CHL 1 PE06 P.D. Serous adenoca Ascites P/FU/CHL 2 PEA1 P.D. Adenoca Pleural None 2 PEA2 P.D. Adenoca Ascites P/Pred 2 PE016 P.D. Serous adenoca Ascites Radioth 2 PE014 W.D.Serous adenoca Ascites None 2 T014 W.D.Serous adenoca Sol. Met None 2 PE023 W.D.Serous adenoca Ascites P/CHL 2 SKOV-3 Adenoca Ascites T 3 SW626 Adenoca - - 3 OVCAR-2 Adenoca Ascites P/Cy 4 OVCAR-3 P.D. papillary adenoca Ascites P/Cy/Adr 5 OVCAR-4 Adenoca Ascites P/Cy/Adr 6 OVCAR-5 Adenoca Ascites None 7 OAW 28 Adenoca Ascites P / Mel 8 OAW 42 Serous adenoca Ascites P 8 41M Adenoca Ascites None 9 59M Endometr adenoca Ascites None 8 CH1 Papillary adenoca Ascites P/ JM8 8 138D Serous adenoca Ascites Carb 9 180D Adenoca Ascites P 9 200D Serous adenoca Solid None 9 253D Serous adenoca Ascites Cy/MPA 9 HOC-1 W.D. Serous adenoca Ascites None 10 HOC-7 W.D. Serous adenoca Ascites None 10 CAOV-3 Adenoca Tumour Cy/Adr/FU 10 COLO 110 Serous adenoca Sol. Met None 11 COLO 316 Serous adenoca Pleural None 11 COLO 319 Serous adenoca Ascites None 11 COLO 330 Serous adenoca Ascites Mel/Radiother 11 IGROV1 Adenoca Primary None 12 HTOA W.D. serous adenoca Primary None 13 OV-1063 Papillary adenoca Ascites Cy/Adr/P/HMM 14 DO-s W.D. mucinous adenoca Ascites - 15 P.D. = Poorly differentiated; W.D. = Well differentiated; adenoca = adenocarcinoma; pleural = pleural effusion; Sol.met. = solid metastasis; P = cisplatin; FU = 5-fluorouracil; CHL = chlorambucil; Pred = prednimustine; Radioth = radiotherapy; T = thiotepa; Cy = cyclophosphamide; Adr = adriamycin; Mel = melphalan; Carb = carboplatin; MPA = medroxyprogesterone actetate; HMM = examethylmelamine.

A sequence derived by ECoRI restriction of human satellite DNA III has been cloned in λgt WES. The cloned DNA was used as a template for in vitro synthesis of cRNA, which was hybridized in situ to preparations of human metaphase chromosomes with a range of heterochromatic polymorphisms. Most of the hybridization was found on chromosome 1, and the amount of hybridization was related to the size of the C-band on this chromosome. Hybridization to other chromosomes was not related to the C-band size, although hybridization of total satellite DNA is proportional to C-band size. Total satellite DNAs contain a mixture of sequences, some of which are predominantly located on only one pair of chromosomes. Hybridization in situ is able to discriminate between such chromosome-specific sequences and the bulk of satellite DNA. Further analysis of satellite DNAs may identify sequences specific for every chromosome pair.

In a family with a stable dicentric 13:14 translocation chromosome, the distribution of DNA sequences complementary to satellite DNAs I, II and III and ribosomal RNA were studied. The translocation chromosome showed a loss of sequences complementary to all three satellite DNAs, located in the short arms of the acrocentric chromosomes, but slightly more of the sequences complementary to satellite I were retained than of the other two satellite DNAs. The fact that material was lost from all three satellites indicates that they are not present as single discrete blocks in these chromosomes, when we would expect to find the distal sequences lost and the proximal ones retained, but consist of interspersed blocks with each sequence represented by more than one, and probably several blocks. There was a total loss of ribosomal DNA from the nucleolar organiser regions of the chromosomes involved in the 13:14 translocation, but an interesting finding was the presence of extra ribosomal DNA and satellite DNAs I, II and III in one chromosome 22 which was found in seven out of nine individuals of the family with the 13:14 translocation, and in only one of five individuals without the translocation. There may be a compensatory mechanism present when certain sequences are elminated during chromosomal rearrangements. The relationship of such mechanisms to reproductive fitness is discussed.