Chromosome aberrations and oncogene alterations in two new breast tumor cell lines

Three novel hormone-responsive cell lines derived from primary human breast carcinomas: functional characterization

Human breast cancer primary cultures are useful tools for the study of several aspects of cancer biology, including the effects of chemotherapy and acute gene expression in response to different hormonal/chemotherapy treatments. The present study reports the conditions for primary culture of breast cancer samples from untreated patients and the most effective collagenization method to dissociate human samples consisting in an overnight incubation with 1 mg/ml types II or IV collagenase and further incubation in DMEM:F12 (1:1) medium supplemented with glutamine, bovine insulin, penicillin-streptomycin, HEPES, estradiol, cortisol (F), tri-iodothyronine (T(3)), transferrine (TR), and 10% fetal calf serum (FCS). These conditions proved to be appropriate for both primary culture and the development of stable cell lines. Of the seven cell lines obtained, three fast growing and estrogen receptor (ER)+/progesterone receptor (PgR)+/EGF receptor (EGFR)+ have been characterized. The cells are able to grow both in soft agar and in nude mice, and express cytokeratins, all parameters characteristic of malignant epithelial cell lines. The cells also exhibit an increased proliferation rate in the presence of estradiol, progesterone, and EGF, suggesting the presence of the corresponding receptors. The mRNA expression of type alpha- and beta-ER as well as EGFR, was confirmed by RT-PCR. In conclusion, the novel cell lines described, arose from primary tumors and are sensitive to estradiol, progesterone, and EGF. This not only expands the repertoire of breast cancer cells available as potentially useful tools for examining most parameters in breast cancer "in vitro", but also provides unique new models to explore the complex regulation by steroids as well as growth factors in such cells.

Genomic structure and expression profile of LPHH1, a 7TM gene variably expressed in breast cancer cell lines

Gene identification studies, centred on a region of overlapping loss of heterozygosity in breast tumours within band 1p31.1, lead to the characterisation of LPHH1, a novel human 7TM gene. The coding sequence of LPHH1 extends over a 60 kb region and comprises in excess of 28 exons. Alternative splicing occurs minimally at five positions, four of which are within the coding sequence. The fifth region of alternative splicing occurs at the extreme 5' end of the transcript. A clear tissue specific bias in alternative exon selection is observed to some degree at all five positions, including the extreme 5' region, which raises the possibility of multiple and perhaps tissue specific promoters. One such putative promoter region, which appears to be utilised predominantly in breast cancer cells, has been identified. LPHH1 is highly evolutionarily conserved, with the simplest (19 exon) gene product being 95% identical between human and rat. Comparison of the alternatively spliced exons between three species, where data are available, has so far revealed 100% identity in the encoded peptide sequences, suggesting conservation of a functional aspect of this splicing. Gene expression has been observed in all tissues and cell lines tested, with the exception of lymphoblastoid and multiple myeloma lines, where there appears to be only a very low level of transcription. LPHH1 also appears to be downregulated in human bone marrow. These data are consistent with a role for the gene products in adhesion-mediated signalling. Analysis of a panel of breast tumour cell lines revealed that a number apparently overexpressed the gene whilst others showed very low levels of transcription. In one case, the overexpression correlated with a low level increase in gene copy number in the tumour line. In addition to differences in the overall levels of expression, LPHH1 mRNAs were alternatively spliced to varying degrees with shifts in the major gene product to truncated or altered forms in some lines. No somatic LPHH1 mutations were detected through sequence analysis of four primary breast tumours that showed loss of the adjacent 1p31.1 marker D1S207.

Differential characteristics of two new tumorigenic cell lines of human breast carcinoma origin

Permanent human tumor cell lines are an important tool for the study of breast cancer. Two new breast cancer cell lines (BrCa-MZ-01 and BrCa-MZ-02) were isolated from a solid tumor and a pleural effusion, respectively. One cell line was established from a medullary carcinoma, the other from a ductal carcinoma. These cells exhibit ultrastructural and immunohistochemical features of epithelial cells of mammary origin. Intermediate filament and cytokeratin typing showed a clear predominance of the simple-epithelial cytokeratins CK 8, CK 18 and CK 19, although the expression was reduced in comparison to the hormone receptor-positive reference cell lines MCF-7 and ZR-75-1. Both cell lines produced slow-growing tumors after subcutaneous (s.c.) transplantation of 1 x 10(7) viable tumor cells into nude mice. The cell line BrCa-MZ-01 expresses the estrogen and progesterone receptor, whereas the cell line BrCa-MZ-02 remains negative. Both cell lines are positive for secretion of platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta), whereas interleukin-6 (IL-6) is only secreted by the cell line BrCa-MZ-02.

Identification of rapid turnover transcripts overexpressed in thyroid tumors and thyroid cancer cell lines: use of a targeted differential RNA display method to select for mRNA subsets

The mRNAs of transiently expressed proteins such as cytokines and proto-oncogenes are commonly subject to rapid transcriptional activation and degradation. Transcript turnover is determined in part by association of certain proteins with consensus AU-rich motifs (AUUUA) in the 3'-untranslated region of the transcripts. Here we report a modification of differential RNA display (DRD) to detect differentially expressed rapid turnover mRNAs containing AU-rich motifs from thyroid cancer tissues and cell lines. RNA of normal and thyroid cancer tissues was differentially displayed using a 3'anchor primer to the poly(A) tail and an arbitrary 5'primer incorporating an AUUUA sequence. The appropriateness of the strategy was established by its ability to display known early response genes, such as c- fos, using partially degenerate primers. To test whether the novel cDNAs isolated coded for transcripts subject to rapid turnover, they were used as probes for Northern blots of RNA from clonal human thyroid carcinoma cell lines treated for varying periods with either cycloheximide or actinomycin D. A number of novel differentially expressed cDNA fragments were isolated from human papillary thyroid carcinoma tissues, among them a cDNA with zinc finger motifs and homology to other zinc finger proteins. Using this fragment to probe a cDNA library, a full-length cDNA (ZnF20) was isolated that was 4333 bp in length and contained an open reading frame of 1029 amino acids. The ZnF20 cDNA hybridized to multiple transcripts in a thyroid cancer cell line (8.0, 4.5 and 2 kb) that increased after cycloheximide treatment and decayed <2 h after addition of actinomycin D. The ZnF20 mRNA was overexpressed in three of six thyroid papillary carcinomas as compared with paired normal thyroid tissue controls. The data presented here support the use of a targeted DRD approach for the isolation of rapid turnover mRNAs, many of which may be interesting candidate oncogenes.

Disease heterogeneity: does it impact our ability to detect dietary associations with breast cancer?

It is generally believed that breast cancer is a multistage process and that multiple and varying genetic events occur on the pathway to disease. We hypothesize that disease heterogeneity has an impact on our ability to identify risk factors. If a genetic alteration occurred in 50% of cases and a risk factor was associated only with that specific alteration, a risk estimate of 1.6 would be detected rather than the true risk estimate of 2.5 if analyses had been limited to those cases with the genetic alteration. Based on the literature we know that many genetic alterations occur in less than 50% of breast tumors. Thus, if environmental factors are related to some, but not all genetic alterations, we are decreasing our ability to identify potentially important risk factors. We therefore hypothesize that identification of dietary factors associated with breast cancer has been hampered by our inability to identify and capture the unique disease pathways which exist and contribute to the heterogeneity of common cancers such as breast cancer.

Critical determination of the frequency of c-erbB-2 amplification in breast cancer

Tissues from 323 methacarn-fixed and paraffin-embedded breast cancers were assessed for c-erbB-2 gene amplification by differential polymerase chain reaction (dPCR). The sensitivity of dPCR was ascertained using cell lines with c-erbB-2 amplification, and the relationship between dPCR ratio value and gene copy number was established. In clinical material the technique was not affected by the DNA contribution of normal tissue elements or by cancer DNA ploidy change. c-erbB-2 gene amplification was detected in 55% of invasive cancers and in 66% of in situ cancers. c-erbB-2 protein overexpression in breast cancer cells, as determined by specific immunohistochemistry, was only detected in 11% of invasive cancers and 43% of in situ cancers. Comparisons show that a substantial number of cancers with c-erbB-2 amplification lack detectable protein overexpression. This illustrates the complex nature of c-erbB-2 gene disregulation in cancer and suggests that multiple combinations of biological events and consequences are possible.

Direct chromosome analysis of 50 primary breast carcinomas

Direct chromosome analyses were performed in 50 cases of primary breast carcinoma. Thirty-six cases had modal chromosome counts in the diploid range; the other 14 cases were polyploid. Of the 22 cases with detailed G-banding analyses, the most frequent structural changes involved chromosome 1 (15 of 22), 3 (13 of 22), and 6 (13 of 22). Deletion of chromosome 1p was noted in nine cases, and both 3p- and 6q- were noted in 10 cases.

New evidence for tandem chromosome fusions in the karyotypic evolution of Asian muntjacs

A clone of highly repetitive DNA, designated C5, was isolated from DNA of female Chinese muntjac cells. The nucleotide sequence of this clone is 80%-85% homologous to that of the satellite IA clone and other highly repetitive DNA clones previously obtained from the Indian muntjac. Using C5 as a probe for in situ hybridizations to chromosome preparations of cells of both the Chinese and Indian muntjacs, we were able to show that these repeated sequences occur in centromeric heterochromatin of the chromosomes of both Chinese and Indian muntjac species. More significantly, non-random clusters of hybridization signals were detected on the arms of chromosomes of the Indian muntjac. These latter hybridization sites are postulated to be regions of interstitial heterochromatin and could be the remnants of centromeric heterochromatin from ancestral Chinese muntjac chromosomes. Our observations provide new supportive evidence for the tandem chromosome fusion theory that has been proposed for the evolution of the Indian muntjac karyotype.