Further studies on a hybrid cell-surface antigen associated with human chromosome 11 using a monoclonal antibody

Feline vaccine-associated sarcomagenesis: Is there an inflammation-independent role for aluminium?

Aluminium has been found in feline vaccine-associated sarcomas. In this study, we investigated the potential for aluminium to contribute directly to tumourigenesis. Our results indicated that an aluminium hydroxide adjuvant preparation was cytotoxic and mutagenic in human-Chinese hamster ovary (CHO) hybrid cells in vitro. Moreover, CHO cells deficient in DNA double strand break (DSB), but not single-strand break (SSB), repair, were particularly sensitive to aluminium exposure compared with repair proficient cells, suggesting that aluminium is associated with DSBs. In contrast to CHO cells, primary feline skin fibroblasts were resistant to the cytotoxic effects of aluminium compounds and exposure to an aluminium chloride salt promoted cell growth and cell cycle progression at concentrations much less than those measured in particular feline rabies vaccines. These findings suggest that aluminium exposure may contribute, theoretically, to both initiation and promotion of tumours in the absence of an inflammatory response.

Gamma-ray mutagenesis studies in a new human-hamster hybrid, A(L)CD59(+/-), which has two human chromosomes 11 but is hemizygous for the CD59 gene

Kraemer, S. M., Vannais, D. B., Kronenberg, A., Ueno, A. and Waldren, C. A. Gamma-Ray Mutagenesis Studies in a New Human-Hamster Hybrid, A(L)CD59(+/-), which has Two Human Chromosomes 11 but is Hemizygous for the CD59 Gene. Radiat. Res. 156, 10-19 (2001). We have developed a human-CHO hybrid cell line, named A(L)CD59(+/-), which has two copies of human chromosome 11 but is hemizygous for the CD59 gene and the CD59 cell surface antigen that it encodes. Our previous studies used the A(L) and A(L)C hybrids that respectively contain one or two sets of CHO chromosomes plus a single copy of human chromosome 11. The CD59 gene at 11p13.5 and the CD59 antigen encoded by it are the principal markers used in our mutagenesis studies. The hybrid A(L)CD59(+/-) contains two copies of human chromosome 11, only one of which carries the CD59 gene. The incidence of CD59 (-) mutants (formerly called S1(-)) induced by (137)Cs gamma rays is about fivefold greater in A(L)CD59(+/-) cells than in A(L) cells. Evidence is presented that this increase in mutant yield is due to the increased induction of certain classes of large chromosomal mutations that are lethal to A(L) cells but are tolerated in the A(L)CD59(+/-) hybrid. In addition, significantly more of the CD59 (-) mutants induced by (137)Cs gamma rays in A(L)CD59(+/-) cells display chromosomal instability than in A(L) cells. On the other hand, the yield of gamma-ray-induced CD59 (-) mutants in A(L)CD59(+/-) cells is half that of the A(L)C hybrid, which also tolerates very large mutations but has only one copy of human chromosome 11. We interpret the difference in mutability as evidence that repair processes involving the homologous chromosomes 11 play a role in determining mutant yields. The A(L)CD59(+/-) hybrid provides a useful new tool for quantifying mutagenesis and shedding light on mechanisms of genetic instability and mutagenesis.

EagI and NotI linking clones from human chromosomes 11 and Xp

EagI and NotI linking libraries were prepared in the lambda vector, EMBL5, from the mouse-human somatic cell hybrid 1W1LA4.9, which contains human chromosomes 11 and Xp as the only human component. Individual clones containing human DNA were isolated by their ability to hybridise with total human DNA and digested with SalI and EcoRI to identify the human insert size and single-copy fragments. The mean (+/- SD) insert sizes of the EagI and NotI clones were 18.3 +/- 3.2 kb and 16.6 +/- 3.6 kb, respectively. Regional localisation of 66 clones (52 EagI, 14 NotI) was achieved using a panel of 20 somatic cell hybrids that contained different overlapping deletions of chromosomes 11 or Xp. Thirty-nine clones (36 EagI, 3 NotI) were localised to chromosome 11; 17 of these were clustered in 11q13 and another nine were clustered in 11q14-q23.1. Twenty-seven clones (16 EagI, 11 NotI) were localised to Xp and 10 of these were clustered in Xp11. The 66 clones were assessed for seven different microsatellite repetitive sequences; restriction fragment length polymorphisms for five clones from 11q13 were also identified. These EagI and NotI clones, which supplement those previously mapped to chromosome 11 and Xp, should facilitate the generation of more detailed maps and the identification of genes that are associated with CpG-rich islands.

11p deletions and breakpoints in squamous cell carcinoma: association with altered reactivity with the UM-E7 antibody

The UM-E7 monoclonal antibody raised against the UM-SCC-I human squamous cell carcinoma (SCC) cell line identifies a cell surface antigen that is strongly expressed in normal tissues. The locus (MICI) controlling the expression of E7 and related cell surface antigens has been mapped to chromosome band 11p13. This band has been identified as a region of cancer-associated aberrations and as the probable locus of a tumor suppressor gene. Although E7 antigen expression is strong in normal keratinocytes, it varies among squamous carcinoma cell lines. Some SCC lines (12/26) exhibit weak expression of the E7 antigen, whereas other SCC cell lines (14/26) and 21 cell lines from other tumor types express the antigen strongly. On the basis of these observations and of mapping data, we postulated that low E7 antigen expression in a subset of SCC cell lines might be associated with chromosomal rearrangement or deletion involving the E7 locus on 11p. Fully evaluable karyotypes were prepared from 19 SCC cell lines, including 11 with weak and eight with strong E7 expression. Eight of the 11 lines with weak E7 expression had 11p abnormalities. Four of these contained 11p deletions, and four others had a breakpoint in 11p. In contrast, none of the cell lines in the group with strong E7 expression had an 11p deletion, although one had a rearrangement with an 11p breakpoint. In the four tumors with visible 11p deletions, the smallest region of overlap corresponded to the 11p13-p14 region. The mean log10 50% endpoint E7 titer in the group with 11p deletions or breakpoints was nearly two orders of magnitude lower than that of the lines with no 11p abnormality (1.95 +/- 0.53) (P less than 0.02). Our results indicate that the UM-E7 antibody identifies tumors with 11p13-p14 deletions and other 11p rearrangements and that the 11p region is a site of nonrandom chromosome rearrangement in a subset of human squamous cancers. The strong association of loss of antigen expression with visible 11p deletion or rearrangement in some tumors suggests that other tumors with this phenotype may contain submicroscopic lesions of 11p13-p14.

Establishment and characterization of UM-EC-2, a tamoxifen-sensitive, estrogen receptor-negative human endometrial carcinoma cell line

UM-EC-2 was established from a patient with poorly differentiated stage IB endometrial carcinoma. This cell line produces tumors in nude mice that have the same histological features as the patient's tumor. UM-EC-2 cells express b2-microglobulin, the epidermal growth factor receptor (EGF), and the H blood group antigen. This membrane antigen phenotype is consistent with cells of human endometrial origin. The karyotype of UM-EC-2 is fairly complex, with rearrangements affecting all chromosomes except 3, 10, 14, 19, and 20. There were two populations of cells, a hyperdiploid population with a modal number of 53-55 and a hypertetraploid population with a modal number of 109. A postulated sequence of events before and after tetraploidization is suggested based on the number of copies of individual chromosomes and rearrangements. Comparison of the UM-EC-2 karyotype to that of UM-EC-1 (a previously described line from a different patient with endometrial carcinoma) revealed that the two lines share eight very similar chromosome changes, which include loss of most of chromosome 4, breakpoints affecting proximal bands on 8p, loss of most of 9q, a breakpoint at 12q22, loss of 13q, breakpoints in proximal bands on 18q, and a breakpoint at 22p11. These changes may represent nonrandom chromosome abnormalities in poorly differentiated endometrial cancer. Estrogen (ER) and progesterone (PgR) receptors were not detected in either the primary tumor or the cell line. Nevertheless, UM-EC-2 cells were very sensitive to growth inhibition by tamoxifen (TAM) in vitro. One micromolar TAM caused 50% inhibition of cell growth, 2.5 microM caused cytostasis, and 5 microM TAM was cytotoxic, killing all cells after 5-7 days of exposure to the drug. Paradoxically, 100 nM estradiol (E2) caused a moderate increase in the growth of the cells but it did not prevent or reverse growth inhibitory effects of TAM. These findings support the concept that in some tumors TAM causes growth inhibition by an ER-independent mechanism. UM-EC-2 cells were also sensitive to growth regulation by EGF. Thus, these cells provide a new in vitro model of human endometrial cancer in which the roles of both TAM and EGF as growth regulatory substances can be investigated.

Chemoprevention of upper aerodigestive tract cancers: a report of the third Upper Aerodigestive Cancer Task Force workshop

The National Cancer Institute Organ Systems Program-sponsored Upper Aerodigestive Cancer Task Force workshops are specifically designed to enhance interactions between basic science and clinical investigators and between academic institutions and the community, and ultimately will contribute to more expeditious clinical advances. The third workshop in this series focused on the rapidly expanding area of chemoprevention of upper aerodigestive epithelial cancers. The first two sessions were devoted to discussion of in vitro and animal-model data documenting the multistep process of squamous differentiation and carcinogenesis, associated molecular and biochemical alterations, and modulation by chemopreventive agents. Animal-model studies have identified several promising chemopreventive agents and synergistic combinations for clinical trial. The last two sessions reviewed nutritional epidemiology, major methodologic issues of large intervention studies, and the novel concept of biologic markers as intermediate endpoints for chemoprevention trials.

Measurement of low levels of x-ray mutagenesis in relation to human disease

We previously demonstrated that conventional methods for measurement of mutagenesis in mammalian cells are subject to serious error that causes underestimation of environmental contributions to cancer and genetic disease. This error has been corrected by use of somatic cell hybrids containing a single human chromosome on which the marker genes are carried and by using doses of mutagenic agents so low that little cell killing occurs. This method permits direct measurement of the effects of low doses of radiation and other mutagens without resort to the controversial extrapolation procedure customarily used to estimate effects of doses in the neighborhood of actual human exposures. The new data demonstrate that the true mutagenesis efficiency at the low doses of ionizing radiation that approximate human exposures is more than 200 times greater than those obtained with conventional methods. This methodology also permits evaluation of localized mutations, large and small chromosomal deletions, and nondisjunctional processes and can be used for mutagens that need metabolic activation as well as for cooperatively acting agents. The two opposing classical views that in mammalian cells extrapolation to low doses of x-radiation is linear, on the one hand, or involves a threshold, on the other, are both demonstrated to be incorrect at least for the conditions here considered. The actual curve exhibits a downward concavity so that the mutational efficiency is maximal at low doses. These data may have important implications for human health.

Expression of human chromosome 11-encoded cell-surface antigens by DNA-mediated transfectants

DNA-mediated transfectants were isolated that expressed two of the cell-surface antigens encoded by human chromosome 11. These tranfectants were used to analyze monoclonal antibodies selected to recognize human cell-surface antigens expressed by a somatic cell hybrid containing 11 as its only human chromosome. Analysis of the transfectants, deletion hybrids, and mutants showed that the monoclonal antibodies recognized at least five different antigens, one of which we had not identified previously. A majority of the monoclonal antibodies recognized the a1 antigen. The use of cells from higher primates demonstrated that the a1-specific monoclonal antibodies recognize at least two epitopes.

Wilms' tumor-aniridia association: segregation of affected chromosome in somatic cell hybrids, identification of cell surface antigen associated with deleted area, and regional mapping of c-Ha-ras-1 oncogene, insulin gene, and beta-globin gene

Fusion of an auxotrophic mutant hamster cell with the skin fibroblasts of a child with the Wilms' tumor-aniridia association produced clones which, on the one hand, contained the child's normal chromosome 11 and, on the other, the chromosome 11 with the 11p13 deletion associated with the syndrome. Both hybrids were positive for human LDH-A by enzymatic assay. Clones containing the normal human chromosome 11 were killed by a cytotoxic monoclonal antibody to a cell surface antigen previously mapped to the 11p13----11pter region of chromosome 11. Clones with the abnormal 11 were not killed. Thus, we have produced hybrids from the same patient distinct from each other on the basis of their chromosome 11. These hybrids have been used to map the locus for a cell surface antigen to the deleted region on chromosome 11 of a patient with the Wilms tumor-aniridia association. The linkage between this antigen and the syndrome should be helpful in further study of the genetics of this disease. In addition, we have found that the c-Ha-ras-1 oncogene is distal to the p13 region of chromosome 11 and the position of insulin and beta-globin on the chromosome. Finally, by producing segregants of the hybrids containing the abnormal chromosome 11, we have provided evidence that chromosome 11-associated c-Ha-ras-1 is syntenic with chromosome 11 and not moved to a different portion of the genome.

Human muscle cell surface antigen 16.3A5 is encoded by a gene on chromosome 11

A monoclonal antibody (McAb), 16.3A5, has been characterized that reacts with a cell surface antigen of human muscle cells and a variety of nonmuscle cells. The gene controlling synthesis of 16.3A5 antigen has been assigned to human chromosome 11 by assessing McAb reactivity on a panel of mouse-human cell hybrids. The 16.3A5 has a novel specificity distinct from other chromosome 11-encoded antigens such as W6/34, F10.44.2, TRA1.10, and 4D12 antigens.

Relationships between genes on human chromosome 11 encoding cell-surface antigens

Genes encoding seven monoclonal antibody-defined cell-surface antigens have been regionally mapped on human chromosome 11, and compared to those of the AL complex defined by polyclonal antibodies using mutational analysis. MIC1, encoding W6/34 antigen, is probably identical to S1, previously mapped to 11pter-p13. MDU1 and MIC8, encoding 4F2 and TRA-1.10 antigens, respectively, are probably identical to S2(a4) and map to 11q13-q22. MIC9, which governs expression of 4D12 and 2E2 antigens, and maps to 11q22-qter, is not related to any of the five AL genes. MIC4 and MIC11, both mapping to 11pter-p13, may have some relationship to S3 and S1, respectively, but identity has not been proven.