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J L Bos

Publications and source records attributed to J L Bos.

At least 127 records · Page 7Linked to original sources
PubMed1989

Activated oncogenes in human skin tumors from a repair-deficient syndrome, xeroderma pigmentosum.

The recessive autosomal hereditary disease, xeroderma pigmentosum (XP), is characterized by a high incidence of tumors in sun-exposed skin. The defect in early steps of excision repair of XP cells leads to hypermutability towards UV-mimicking agents. DNA from eight XP tumors were screened for activated transforming genes using 3T3 transfection. In two skin tumors isolated from a XP child, an activated N-ras oncogene was detected. Synthetic oligonucleotide probes were used to characterize the mutation in the ras gene. Both tumors were found to be mutated in the 61st N-ras codon from gln to his. The mutation was accompanied by an increase in the level of N-ras specific mRNA and in one transformant, by the alteration of the p21 protein. In the same tumors, c-myc amplification and over transcription, and Ha-ras gene rearrangement and amplification were also detected. Analysis of other XP tumors with eleven different oncogene probes revealed an amplification of the Ha-ras gene in 6 out of 10 cases. The normal skin fibroblasts from XP patients show normal pattern levels of N-ras, c-myc and Ha-ras sequences. The hypothesis is proposed that the presence of several oncogene alterations in the same tumor could be due to the high amount of UV-induced DNA lesions found in the exposed skin cells, in the absence of efficient repair.

DNA↗
PubMed1989

Establishment and characterization of a melanoma cell line from a xeroderma pigmentosum patient: activation of N-ras at a potential pyrimidine dimer site.

Patients suffering from the genetic disorder xeroderma pigmentosum (XP) display an extreme sensitivity of their skin to sun (UV) exposure and predisposition to skin cancer due to deficiencies in the excision DNA repair pathway. Here we describe the establishment and characterization of the first tumor cell line derived from an XP patient (belonging to complementation group C). The melanoma cell line designated XP44RO(Mel) has retained its tumorigenic and XP phenotype (UV sensitivity, reduced unscheduled DNA synthesis) and showed karyotypic abnormalities characteristic of melanomas. Transfection of XP44RO(Mel) DNA to NIH3T3 cells and oligonucleotide hybridization revealed that the N-ras oncogene was activated by an A.T to T.A or C.G transversion at the third position of codon 61. This mutation occurs at a dipyrimidine site. It is likely initiated by a UV-induced pyrimidine dimer and is of a type rarely observed in mammalian shuttle vector systems and endogenous genes after UV irradiation.

Animals↗
PubMed1989

Detection of ras gene alterations and ras proteins in colorectal cancer.

DNA extracted from 31 primary colorectal carcinomas was analyzed for the presence of ras gene amplification and mutations. Nine carcinomas had Ha-ras amplification and seven Ki-ras amplification. Nine carcinomas had codon 12 Ki-ras mutations. Immunohistochemical staining for ras proteins revealed a normal membrane association in normal mucosa and benign polyps but an abnormal cytoplasmic distribution in carcinomas. Amplification, mutations, and immunohistochemical staining were independent of histologic differentiation, Dukes' stage, or DNA ploidy status. This study demonstrates that abnormalities of ras genes are a common finding in colorectal carcinomas. They are potentially important biologic changes associated with malignancy, although they do not appear to be related to clinical behavior.

Adult↗
PubMed1989

Adenovirus E1A represses transcription of the cellular JE gene.

The expression of the growth factor-inducible JE gene was severely reduced in cells expressing region E1A of human adenoviruses. This reduction was not caused by a decreased stability of JE mRNA but by a reduced transcription rate as determined by run-on transcription experiments. Nevertheless, JE mRNA could still be induced by growth factors, suggesting that intracellular signaling is not blocked but rather that the basal level of JE transcription is repressed by E1A.

Adenovirus Early Proteins↗
PubMed1989

Adenovirus type 12 E1A down regulates expression of a transgene under control of a major histocompatibility complex class I promoter: evidence for transcriptional control.

The E1 region of human adenovirus type 12 (Ad12 E1) represses the expression of major histocompatibility complex (MHC) class I genes in transformed primary rodent cells. Conflicting results have been reported as to whether this E1A-mediated repression occurs at a transcriptional or a posttranscriptional level. In the present study, we show that in Ad12 E1-transformed primary baby mouse kidney cells from transgenic mice harboring the human growth hormone gene under control of an H-2K promoter both the expression of the endogenous MHC class I genes and the expression of the transgene are repressed. This experiment, as well as nuclear run-on analyses performed with single-stranded probes, revealed that Ad12 E1A inhibits MHC class I gene expression by repressing its promoter.

Adenovirus Early Proteins↗
PubMed1989

Possible involvement of normal p21 H-ras in the insulin/insulinlike growth factor 1 signal transduction pathway.

Expression of a mutant H-ras gene confers a transformed phenotype to rat-1 fibroblasts which is basically independent of exogenous growth factors (GFs). Rat-1 cells induced to express high levels of the normal H-ras gene were also found to display a transformed phenotype. In contrast to cells expressing mutant H-ras, these cells were dependent on GFs. We used this difference in GF dependence to analyze a possible involvement of exogenous GFs in H-ras function. Compared with untransformed rat-1 cells, cells overexpressing normal H-ras displayed an elevated response toward insulinlike growth factor 1 (IGF-1), insulin, and bombesin and an increased sensitivity toward phosphatidic acids. It was found that 8-bromo-cyclic AMP inhibited the responses to all GFs in rat-1 cells but had no effect on mutant-H-ras-transformed cells. In cells overexpressing normal H-ras, 8-bromo-cyclic AMP inhibited the responses to all GFs except those to insulin and IGF-1. This implies that overexpression of normal H-ras in the presence of insulin/IGF-1 is functionally similar to the expression of mutant H-ras, since mutant H-ras can circumvent this block by itself. These and other results strongly suggest a functional linkage between insulin/IGF-1 and normal p21 H-ras.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1989

N-ras mutations in human cutaneous melanoma from sun-exposed body sites.

In 7 of 37 patients with cutaneous melanoma, mutations in the N-ras gene were found. The primary tumors of these seven patients were exclusively localized on body sites continuously exposed to sunlight. Moreover, the ras mutations were all at or near dipyrimidine sites known to be targets of UV damage. Two primary tumors were biclonal with respect to ras mutation. An active role for UV irradiation in induction of the mutations is suggested.

DNA, Neoplasm↗
PubMed1989

The repression of the growth factor-inducible genes JE, c-myc and stromelysin by adenovirus E1A is mediated by conserved region 1.

The growth factor-inducible cellular genes JE, c-myc and stromelysin (sml) are strongly repressed upon transformation by adenovirus E1A. As E1A proteins are multifunctional and apparently contain distinct domains (conserved regions 1, 2 and 3), each with a specific effect on gene regulation and cell-transformation, we have investigated which of the three conserved regions are responsible for the reduced expression of these genes. To this end, we monitored the expression of the JE, sml and c-myc genes in a panel of normal rat kidney (NRK) cells expressing different mutant E1A genes. Only CR1, and not CR2 or CR3 were found to be essential for the repression of the genes, indicating that CR1, one of the regions essential for cell transformation, represents an autonomous gene regulatory function that can operate in the absence of CR2. We also show that the association of E1A proteins to a 300 kD cellular protein in NRK cells coincides with the ability to repress these genes.

Adenovirus Early Proteins↗
PubMed1989

Mechanisms of ras mutation in myelodysplastic syndrome.

Using synthetic oligonucleotide hybridization, we have found a ras mutation in 11 of 27 patients (41%) with primary or non-therapy related myelodysplastic syndrome (MDS). This high incidence of mutation, mainly of the N-ras oncogene, was generally found in patients with disease progression to acute leukemia (8 of 11 patients = 73%). Two general mechanisms of ras mutation were found. In five patients the ras mutation was present in only a fraction of the cells; sometimes appearing in late stages of the disease, suggesting that it can occur in a differentiated cell clone. In six other patients, the ras mutation was present in the great majority of bone marrow or blood cells. The mutation was detected in mature normal lymphocytes and persisted following a complete clinical remission in two of these patients, implying that the ras mutation can occur in an early stage of cell differentiation or stem cell. Patients with a ras mutation had a median survival of nine months (all patients dead) compared to 16 patients without a ras mutation that had a median follow-up of 16 months (10 patients alive; P less than 0.005). Since 9 of the 11 patients (82%) with a ras mutation were found to have an abnormal monocytic component at diagnosis or during disease evolution, it is possible that in myeloid disorders a ras mutation is preferentially associated with myelomonocytic cell differentiation.

Aged↗
PubMed1989

Activated ras genes in human seminoma: evidence for tumor heterogeneity.

The incidence of mutations in cellular ras genes was determined in human seminoma, a germ cell tumor of the testis, with the aid of specific oligonucleotide probe hybridization. To eliminate the large number of nonneoplastic cells present in seminomas, aneuploid tumor cell nuclei were isolated from the tumor tissue by flow sorting. Mutations were detected in 40% of the seminomas at codons 12 or 61 of either the Ki-ras or the N-ras gene. No correlation was found with histopathological or clinical features. In some seminomas the mutant gene was present in only a fraction of the tumor cell population, suggesting tumor heterogeneity for ras gene mutations. Yet, flow cytometric measurement of nuclear DNA contents and histological examination of tumor tissue did not reveal two different tumor cell populations. We conclude from these observations that ras mutation is probably not the initial genetic event in the development of seminoma.

Animals↗
PubMed1988

Similar effects of adenovirus E1A and glucocorticoid hormones on the expression of the metalloprotease stromelysin.

The stromelysin (sml) gene encodes a secreted protease which degrades components of the extracellular matrix. Transformation of NRK49F cells by the E1A region of adenovirus (Ad) type 5 or 12 reduces sml RNA levels, whereas various growth factors or EJras-mediated transformation stimulate sml gene expression in these cells. Nuclear run-on experiments show that AdE1A, growth factors and EJras act on sml gene expression at the level of transcription. Although the sml gene is strongly suppressed in AdE1A-transformed cells, treatment with growth factors or transfection of EJras still causes a raise in sml mRNA levels, indicating that E1A does not block the induction mechanism itself. The effect of glucocorticoid hormones on sml gene expression is very similar to that of AdE1A, in that mRNA levels are lowered without affecting the induction phenomenon. This similarity may provide a clue to the mechanism by which AdE1A represses cellular gene activity.

Adenoviruses, Human↗
PubMed1988

Incidence and possible clinical significance of K-ras oncogene activation in adenocarcinoma of the human lung.

47 tumor samples, 45 of which were obtained at thoracotomy for non-small cell lung cancer were examined for mutational activation of the oncogenes H-ras, K-ras, and N-ras. A novel, highly sensitive assay based on oligonucleotide hybridization following an in vitro amplification step was employed. ras gene mutations were present in nine of 35 adenocarcinomas of the lung (all K-ras), in two of two lung metastases of colorectal adenocarcinomas (1 x K-ras, 1 x N-ras) and in one adenocarcinoma sample obtained at autopsy (H-ras). All K-ras and H-ras mutations were in either position 1 or 2 of codon 12, while the N-ras mutation was in position 2 of codon 61. The potential clinical significance of K-ras activation was analyzed using the combined results of this and of our earlier study (S. Rodenhuis et al., New Engl. J. Med., 317: 929-935, 1987). Lung adenocarcinomas with K-ras mutations tended to be smaller and were less likely to have spread to regional lymph nodes at presentation. With a median follow up of 10 months, survival data are still immature. None of six adenocarcinomas of nonsmokers had a K-ras mutation and only one of four who had stopped smoking more than 5 years before. We conclude that mutational K-ras activation is present in about a third of adenocarcinomas of the lung and that the mutational event may be a direct result of one or more carcinogenic ingredients of tobacco smoke. Studies involving larger numbers of patients are required to confirm the association of K-ras activation with smoking and the inverse relation with tumor progression.

Adenocarcinoma↗
PubMed1988

Amplification of epidermal growth factor receptor gene but no evidence of ras mutations in primary human esophageal cancers.

Primary esophageal squamous cell carcinomas from 41 patients were analyzed for the presence of proto-oncogene alterations associated with this malignancy. The occurrence of activating ras gene mutations in 25 tumors was determined using oligomer hybridization of target sequences amplified by polymerase chain reaction. We found no evidence for mutations in codons 12 and 61 of the H-ras, K-ras, and N-ras genes, nor in codon 13 of the K-ras and N-ras loci in any of these tumors. The apparent absence of activated ras oncogene in esophageal cancers represents a possible exception to the presence of these mutations found consistently in numerous other types of human malignancies, and is in striking contrast to the 40% prevalence of ras mutations in human colorectal cancers. Southern blot hybridization experiments with DNAs from tumors demonstrated amplification of the epidermal growth factor receptor gene (c-erbB) in two of 25 carcinomas. No amplification of the structurally related c-erbB2 (neu) gene was detected. In three out of 12 carcinomas, the level of epidermal growth factor receptor RNA was significantly higher than in normal esophageal mucosal tissue. Our results suggest that enhanced transcription of the epidermal growth factor receptor gene is associated with the development of some esophageal cancers.

DNA, Neoplasm↗
PubMed1988

Genetic alterations during colorectal-tumor development.

Because most colorectal carcinomas appear to arise from adenomas, studies of different stages of colorectal neoplasia may shed light on the genetic alterations involved in tumor progression. We looked for four genetic alterations (ras-gene mutations and allelic deletions of chromosomes 5, 17, and 18) in 172 colorectal-tumor specimens representing various stages of neoplastic development. The specimens consisted of 40 predominantly early-stage adenomas from 7 patients with familial adenomatous polyposis, 40 adenomas (19 without associated foci of carcinoma and 21 with such foci) from 33 patients without familial polyposis, and 92 carcinomas resected from 89 patients. We found that ras-gene mutations occurred in 58 percent of adenomas larger than 1 cm and in 47 percent of carcinomas. However, ras mutations were found in only 9 percent of adenomas under 1 cm in size. Sequences on chromosome 5 that are linked to the gene for familial adenomatous polyposis were not lost in adenomas from the patients with polyposis but were lost in 29 to 35 percent of adenomas and carcinomas, respectively, from other patients. A specific region of chromosome 18 was deleted frequently in carcinomas (73 percent) and in advanced adenomas (47 percent) but only occasionally in earlier-stage adenomas (11 to 13 percent). Chromosome 17p sequences were usually lost only in carcinomas (75 percent). The four molecular alterations accumulated in a fashion that paralleled the clinical progression of tumors. These results are consistent with a model of colorectal tumorigenesis in which the steps required for the development of cancer often involve the mutational activation of an oncogene coupled with the loss of several genes that normally suppress tumorigenesis.

Adenoma↗
PubMed1988

KRAS codon 12 mutations occur very frequently in pancreatic adenocarcinomas.

DNAs from human pancreatic adenocarcinomas were analyzed for the presence of mutations in codons 12, 13 and 61 of the NRAS, KRAS and HRAS gene. Formalin-fixed and paraffin-embedded tissue was used directly in an in vitro amplification reaction to expand the relevant RAS sequences. The mutations were detected by selective hybridization using mutation-specific synthetic oligonucleotides. In 28 of the 30 patients we found a mutation in codon 12 of the KRAS gene. This result confirms the findings of Almoguera et al. [Cell 53 (1988) 549-554] that KRAS mutations occur frequently in adenocarcinomas of the exocrine pancreas. The mutations are predominantly G-T transversions, in contrast to the KRAS mutations in colon tumors which are mainly G-A transitions. Furthermore, in a portion of the tumors the mutation appears to be homozygous.

Adenocarcinoma↗
PubMed1988

Cells transformed by adenovirus type 12 but not by type 5 are dependent on insulin or insulin-like growth factor I for their proliferation.

We have investigated the responsiveness to growth factors (GFs) of primary baby rat kidney (BRK) cells transformed by the E1 region of adenovirus 5 or 12. The in vitro growth of non-oncogenic adenovirus 5-transformed BRK cells is largely independent of serum GFs, whereas growth of highly oncogenic adenovirus 12-transformed cells is strictly dependent on GFs present in serum. For the growth of adenovirus 12 E1-transformed BRK cells serum can be replaced by insulin or insulin-like growth factor-I but not by epidermal growth factor. To maintain the in vitro growth of adenovirus 12-transformed cells physiological levels of insulin-like growth factor-I, but not of insulin, are sufficient. Similar results have been found with adenovirus-transformed primary murine cells and with transformants of an established rat cell line, NRK 49F. This indicates that the observed GF responsiveness is not dependent of the cell type used but is determined by the serotype of the adenovirus-transforming region. Using hybrid E1 regions consisting of E1A of one serotype and E1B of the other, we show that the pattern of GF-responsiveness correlates with the origin of the E1A region. The differences in the GF-responsiveness of the adenovirus 5-transformed and adenovirus 12-transformed cells will be discussed in terms of the oncogenicity of these cells.

Adenoviridae↗
PubMed1988

The ras gene family and human carcinogenesis.

It has been well established that specific alterations in members of the ras gene family, H-ras, K-ras and N-ras, can convert them into active oncogenes. These alterations are either point mutations occurring in either codon 12, 13 or 61 or, alternatively, a 5- to 50-fold amplification of the wild-type gene. Activated ras oncogenes have been found in a significant proportion of all tumors but the incidence varies considerably with the tumor type: it is relatively frequent (20-40%) in colorectal cancer and acute myeloid leukemia, but absent or present only rarely in, for example, breast tumors and stomach cancer. No correlation has been found, yet, between the presence of absence of an activated ras gene and the clinical or biological features of the malignancy. The activation of ras oncogenes is only one step in the multistep process of tumor formation. The presence of mutated ras genes in benign polyps of the colon indicates that activation can be an early event, possibly even the initiating event. However, it can also occur later in the course of carcinogenesis to initiate for instance the transition of a benign polyp of the colon into a malignant carcinoma or to convert a primary melanoma into a metastatic tumor. Apparently, the activation of ras genes is not an obligatory event but when it occurs it can contribute to both early and advanced stages of human carcinogenesis.

Cell Transformation, Neoplastic↗