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Biomedical subjects

R Hamelin

Publications and source records attributed to R Hamelin.

85 records · Page 5Linked to original sources
PubMed1975

Search for nucleic acid sequences complementary to a murine oncornaviral genome in poly(A)-rich RNA of human leukemic cells.

The presence of viral-like sequences in the RNA of various types of leukemic cells was investigated by hybridizing cellular poly(A)-containing RNA with cDNA synthesized in an endogenous system of purified Moloney murine sarcoma virus [M-MSV-(MLV)]. Poly(A)-RNA-cDNA hybrids were detected by assaying their resistance to S1 nuclease. Hybrids were found in 22 out of the 46 leukemias that were tested. None of the controls, including material obtained from buffy coats, bone marrow cells, and a continuous human cell line, was positive. Positive cases were found in all the different categories of leukemias with the exception of chronic myelogenous leukemias. There was no definite corelation between the category of leukemia and positivity. A few cases contained a very high proportion of poly(A)-RNA-cDNA hybrid.

Base Sequence↗
PubMed1974

Extent of transcription of mouse sarcoma-leukemia virus by RNA-directed DNA polymerase.

The DNA product obtained from the endogenous RNA-directed DNA polymerase (deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7) reaction of the Moloney sarcoma:leukemia viruses produced by the 78 A-1 cell line was analyzed and characterized. The extent of transcription of viral 70S RNA was measured by RNA.DNA hybridization ((32)P-viral RNA-(3)H product DNA). No double-stranded DNA was obtained. The product consisted of 95-99% single-stranded DNA with an average length of 200 nucleotides. In contrast to the results reported with avian and other RNA oncogenic viruses, it was found that the entire 70S viral RNA genome was transcribed into DNA pieces and that a small excess of the product DNA was sufficient to anneal the 70S RNA and render it totally resistant to single-stranded-specific enzyme digestion.

Animals↗
PubMedDate not supplied

Response to 5-fluorouracil of orthotopically xenografted human colon cancers with a microsatellite instability: influence of P53 status.

Response to 5-FU of 5 different human colon cancers (hCC) with a DNA microsatellite instability (MSI), xenografted into nude mice, was analysed according to their p53 status. Two hCC (TC82 and TC71) had a mutated p53 (mutp53), while two others (TC33 and LoVo) had a wild type p53 (wtp53); the fifth tumour (X17LoVo) originated from the stable transfection of LoVo cells with a dominant mutp53 (273his) vector. All tumours were implanted onto the caecum of nude mice to induce orthotopic growth of hCC. 5-FU was administered at 40 mg/kg per day for 5 consecutive days. A significant growth inhibition of TC82 and TC71 tumours (of 68 and 60%, p < 0.05 and < 0.01 respectively) was observed, whereas 5-FU had no effect on TC33 and LoVo. Moreover, the mutp53 transfected tumour, X17LoVo, displayed significant sensitivity to 5-FU (p < 0.05). This suggests that distinct genetic alterations influence differently the response of hCC to this antimetabolite.

Adenocarcinoma↗
PubMedDate not supplied

Characterization of lactotransferrin receptor in epithelial cell lines from non-malignant human breast, benign mastopathies and breast carcinomas.

The aim of this study was to investigate the presence of lactotransferrin receptor on breast non-malignant SV-40 immortalized cells (HBL100 and NB54T), benign mastopathy immortalized cells (NPM14T and NPM21T1), hst oncogene transformed HBL100 cell line (tumorigenic HH9 cells) and breast carcinoma cells (T47D, MCF7, VHB1, BT20 and MDA-MB 231). Flow cytometry analyses of the reversible binding of lactotransferrin labeled on its glycan moiety with fluorescein indicate, for the first time, that all these epithelial breast cell lines, express a specific lactotransferrin receptor. The binding parameters of [125I]-lactotransferrin to non-malignant cells, hst oncogene transformed cells and benign mastopathy cells are of the same order of magnitude as those determined for activated lymphocytes and for cancerous breast cell lines, except for MDA-MB 231 cells. MDA-MB 231 cells bind lactotransferrin with the lowest affinity and, in contrast to other analyzed breast cells, are not recognized by antibodies directed against lymphocyte lactotransferrin receptor. These results suggest that MDA-MB 231 lactotransferrin receptor is different from that characterized at the cell surface of other breast cells. In conclusion, since the lactotransferrin receptor expression was not enhanced at the surface of cancerous cell lines and was not altered by the oncogene transformation of a normal cell (HBL100) to a tumorigenic cell (HH9), the lactotransferrin receptor cannot be considered as a marker of tumor progression.

Breast↗
PubMedDate not supplied

Steroid hormone receptors and tumorigenicity of sublines from breast tumor metastatic MDA-MB 231 cell line.

Ten cell sublines the MDA-MB 231 human breast cell line were analyzed for their phenotypic diversity: morphology, karyotype, growth rate, clonogenicity in semisolid medium, tumorigenicity in nude mice, number and affinity of nuclear receptors for oestradiol, progesterone and glucocorticoids. Karyotypic analysis showed different aneuploidies from 50 to 120 chromosomes and variable chromosomal rearrangements in the analyzed subclones. All except two of the ten subclones were tumorigenic when injected subcutaneously or intraperitoneally into nude mice. Although the parental cell line has no receptor, all except two of the tested subclones contained various amounts of high affinity oestradiol and progesterone receptors ranging from 3,000 to 33,000 per cell. Seven subclones contained either high affinity oestradiol or progesterone receptors in nuclei. The diversity found in different subclones derived from one breast carcinoma cell line might represent variabilities acquired and selected continuously in culture.

Aneuploidy↗
PubMedDate not supplied

Phenotypes of human epithelial cell lines immortalized from benign mastopathies.

We have cultured cells from normal and benign mastopathy tissues under conditions favoring epithelial cell proliferation. However, such primary cells rapidly lose their ability to grow in vitro. Immortal lines were established after transfection with SV 40 T gene and several cell clones isolated from Normal Breast Adjacent to a tumor (NBAT 32 T2 to T7) and two benign mastopathies (NPM 21 T1 to T14 and NPM 14 T4). This immortalization of epithelial cells reduced the doubling time of cultured cells and increased the densities of the cultured cell populations. Among there cell lines we have characterized five clones and found differences in a number of aspects. Southern blot analysis showed that the SV 40 T gene was stably integrated in the genome of all the established cell lines. Two of the clones (NPM 21 T2 and NPM 21 T4) were nearly diploid showing a high degree of stability. Two other clones (NPM 14 T4 and NPM 21 T1) had near-tetraploid karyotypes, although quite heterogeneous. Comparison of the ultrastructural phenotypes shows that the two near-diploid cell lines were more differentiated than the two others. Estradiol receptors measured by Scatchard analysis and by transactivation of vitellogenin promotor were absent from all the cell lines. Progesterone receptors measured by Scatchard analysis of hormone binding were present in the NPM 14 T4 and NBAT 32 T4 cell lines. The NPM 21 T1 cell line did not contain such steroid receptors. These cell lines are persistent in long-term culture, thus providing a useful in vitro model system for studying factors involved in the proliferation and the transformation of human mammary epithelial cells.

Breast↗
PubMedDate not supplied

Growth dependency of human colon cancer xenograft on organ environment is related with their original clinical stage.

The ability of cancer cells to metastasize might depend on their reduced dependency on the originating tissue. To test this hypothesis, 10 human colorectal carcinomas (CRC) were implanted either onto nude mouse caecum wall (orthotopic site), or into the subcutaneous tissue (ectopic site), and their growth in these sites compared. Prognostic factors were studied: Astler-Coller modified Dukes's stage, loss of chromosome 17p and/or 18q, and their TP53 gene. Early stage CRC [B2 (n = 3) and C1 (n = 1)] were found to grow 1.7 to 3.6 times (p < 0.05, p < 0.008 respectively) more rapidly in the caecum than in subcutaneous tissue. Metastatic stage CRC [C1 (n = 1), C2 (n = 2) or D (n = 3)] grew similarly in both sites, and more slowly than those of the first group. No relationship was found between growth rates, TP53 mutations or karyotypes. Growth rate of non metastatic cancers was slowed down by implantation in a foreign tissue whereas growth of metastatic tumours was similar in both sites, indicating that they do not recognize or need tissue growth factors.

Animals↗
PubMedDate not supplied

[Analysis of genetic disorders of cancer of the rectum: differences in relation to cancer of the colon].

AIMS AND METHODS: We studied the mechanisms of colon and rectal carcinogenesis by analysing in a series of 83 rectal tumors the prevalence of the two tumor types characteristic of colon cancer, i.e., the LOH+ type, defined by p53 and APC mutations (studied by DGGE and protein truncation assay), and the RER+ type, which is characterized by the instability of some mononucleotide repeat microsatellites (Bat 25 and Bat 26). Additionally, we analyzed the occurrence of Ki-Ras mutations (direct sequencing). RESULTS: Only one tumor turned out to be RER+. Moreover, in 59% of the tumor cases mutations were found in p53, essentially affecting codon 175. The APC and Ki-Ras genes were found to be mutated in 40 and 26% of the rectal tumors, respectively. In 18 tumors (21%) none of the genes studied were mutated. CONCLUSIONS: The RER+ phenotype is rare among rectal tumors, which are essentially LOH+. In these LOH+ tumors the p53 gene is more frequently mutated than in colorectal tumors with the same phenotype. Mutations in the APC and Ki-Ras genes, on the other hand, are less frequent in rectal tumors. Tumors with the RER- and LOH- phenotype may develop as a result of a third carcinogenesis model which must be defined.

Aged↗