Biomedical subjects

Anne Hansen Ree

Publications and source records attributed to Anne Hansen Ree.

11 recordsLinked to original sources

PubMed2006

Radiosensitization of colorectal carcinoma cell lines by histone deacetylase inhibition.

BACKGROUND: The tumor response to preoperative radiotherapy of locally advanced rectal cancer varies greatly, warranting the use of experimental models to assay the efficacy of molecular targeting agents in rectal cancer radiosensitization. Histone deacetylase (HDAC) inhibitors, agents that cause hyperacetylation of histone proteins and thereby remodeling of chromatin structure, may override cell cycle checkpoint responses to DNA damage and amplify radiation-induced tumor cell death. METHODS: Human colorectal carcinoma cell lines were exposed to ionizing radiation and HDAC inhibitors, and cell cycle profiles and regulatory factors, as well as clonogenicity, were analyzed. RESULTS: In addition to G(2)/M phase arrest following irradiation, the cell lines displayed cell cycle responses typical for either intact or defective p53 function (the presence or absence, respectively, of radiation-induced expression of the cell cycle inhibitor p21 and subsequent accumulation of G(1) phase cells). In contrast, histone acetylation was associated with complete depletion of the G1 population of cells with functional p53 but accumulation of both G(1) and G(2)/M populations of cells with defective p53. The cellular phenotypes upon HDAC inhibition were consistent with the observed repression of Polo-like kinase-1, a regulatory G(2)/M phase kinase. Following pre-treatment with HDAC inhibitors currently undergoing clinical investigation, the inhibitory effect of ionizing radiation on clonogenicity was significantly amplified. CONCLUSION: In these experimental models, HDAC inhibition sensitized the tumor cells to ionizing radiation, which is in accordance with the concept of increased probability of tumor cell death when chromatin structure is modified.

Cell Cycle↗

PubMed2006

A complex case of rectal neuroendocrine carcinoma with terminal delirium.

BACKGROUND: A 62-year-old white male presented to our department in December 2004 with a 1-month history of intermittent, voluminous bleedings per rectum. His medical history was unremarkable apart from a single, short-lasting syncope shortly before the first bleeding episode. INVESTIGATIONS: Physical examination, colonoscopy, rectal tumor biopsy and immunohistochemistry, pelvic MRI, abdominal and chest CT scans, ultrasound-directed puncture cytology, octreotide scintigraphy, biochemical analysis of tumor markers, and conventional laboratory tests. DIAGNOSIS: Locally advanced rectal neuroendocrine carcinoma with liver metastases. MANAGEMENT: Chemotherapy, CT-planned radiotherapy, antihypercalcemic therapy, terminal supportive care.

Combined Modality Therapy↗

PubMed2005

Cell cycle checkpoint signaling involved in histone deacetylase inhibition and radiation-induced cell death.

In breast cancer, radiation has a central role in the treatment of brain metastasis, although tumor sensitivity might be limited. The tumor cell defense response to ionizing radiation involves activation of cell cycle checkpoint signaling. Histone deacetylase (HDAC) inhibitors, agents that cause hyperacetylation of histone proteins and thereby aberrations in the chromatin structure, may also override the DNA damage defense response and facilitate the radiation-induced mitotic cell death. In experimental metastasis models, the human breast carcinoma cell line MA-11 invariably disseminates to the central nervous system. We compared profiles of in vitro MA-11 cell cycle response to ionizing radiation and HDAC inhibition. After radiation exposure, the G2-M phase accumulation and the preceding repression of the G2 phase regulatory factors Polo-like kinase-1 and cyclin B1 required intact G2 checkpoint signaling through the checkpoint kinase CHK1, whereas the similar phenotypic changes observed with HDAC inhibition did not. MA-11 cells did not show radiation-induced expression of the G1 cell cycle inhibitor p21, indicative of a defective G1 checkpoint and consistent with a point mutation detected in the tumor suppressor TP53 gene. Increase in the p21 level, however, was observed with HDAC inhibition. Following pretreatment with the HDAC inhibitor, the efficiency of clonogenic regrowth after irradiation was reduced, which is in accordance with the concept of increased probability of mitotic cell death when the chromatin structure is disrupted. Among molecular cell cycle-targeted drugs currently in the pipeline for testing in early-phase clinical trials, HDAC inhibitors may have therapeutic potential as radiosensitizers.

Acetylation↗

PubMed2004

[Cell cycle-targeted therapy].

BACKGROUND: The cell cycle defines sequential molecular processes that ensure orderly cell division. The progression throughout the cell cycle is governed by cyclin-dependent kinases, each of which is enzymatically active solely upon binding to its specific cyclin. The cell cycle harbours two checkpoints, or surveillance posts, which are activated when DNA is damaged. The response to the DNA damage involves a temporary cell cycle arrest, mediated by cell cycle inhibitors or other enzyme proteins, ultimately leading to the outcome of cell survival if the DNA is properly repaired, or cell death. The cell cycle checkpoints may also be biological targets for new therapeutic strategies in cancer intervention. MATERIAL AND METHODS: We compared the effect of ionising radiation on tumour cells with intact or defective functions of the cell cycle checkpoint that governs cell division. RESULTS: The tumour cells responded to radiation-induced DNA damage by cell cycle arrest that required intact checkpoint function. This defence response was overridden upon treatment of the tumour cells with a checkpoint signalling inhibitor. INTERPRETATION: Several pharmacological compounds designed to experimentally target the cell cycle are currently in the pipeline for testing in early-phase clinical trials and may have therapeutic potential as radiosensitizers.

Cell Cycle↗

PubMed2004

Inhibitory targeting of checkpoint kinase signaling overrides radiation-induced cell cycle gene regulation: a therapeutic strategy in tumor cell radiosensitization?

BACKGROUND AND PURPOSE: The tumor cell defense response to ionizing radiation involves a temporary arrest at the cell cycle G(2) checkpoint, which is activated by a signaling cascade initiated by the ATM kinase response to DNA damage, ultimately leading to the outcome of further cell survival if the DNA is properly repaired. The inhibitory targeting of the checkpoint kinase signaling elicited by ATM may define a biologically based strategy to override the G(2) phase delay that prevents mitotic entry after DNA damage, thereby increasing the probability of mitotic cell death following exposure to ionizing radiation. MATERIALS AND METHODS: Breast carcinoma cell lines with intact or defective function of the tumor-suppressor protein BRCA1 were exposed to ionizing radiation in the absence or presence of a specific inhibitor (UCN-01) of the checkpoint kinase CHK1, and the response profiles of cell cycle distribution and G(2) phase regulatory factors, as well as the efficiency of clonogenic regrowth, were analyzed. RESULTS: The radiation-induced G(2) phase accumulation was preceded by a transient down-regulation of the G(2) phase-specific polo-like kinase-1 and cyclin B1, which required intact function of both BRCA1 and CHK1. The concomitant treatment with UCN-01 seemed to amplify the cytotoxic effect of ionizing radiation on clonogenic regrowth. CONCLUSION: The effector mechanism of DNA damage on cell cycle gene regulation signals through the checkpoint kinase network. Among molecular cell cycle-targeted drugs currently in pipeline for testing in early phase clinical trials, CHK1 inhibitors may have therapeutic potential as radiosensitizers.

Animals↗

PubMed2003

Repression of mRNA for the PLK cell cycle gene after DNA damage requires BRCA1.

DNA damage activates the G2 cell cycle checkpoint to allow time for DNA repair before mitotic entry. The mechanism involves inhibition of the enzymatic activity for polo-like kinase 1 (Plk1), rendering Cdc25C with a basal phosphatase activity that is insufficient for converting Cdc2 to the fully active G2/M transition kinase. We found that cell cycle arrest at the G2/M boundary after ionizing radiation (IR) of breast carcinoma cells may involve repression of the gene for Plk1, PLK, mediated by the tumor-suppressor protein BRCA1. The p53-defective MT-1 cell line had an apparent accumulation of G2/M phase cells 12 h after irradiation. This response was preceded by a transient downregulation of PLK mRNA expression with a barely detectable level 6 h after exposure to IR but recovered after 12 h. A significantly lower fraction of irradiated BRCA1(-/-) HCC1937 cells arrested in the G2/M phase after 12 h, and the transient response of PLK mRNA was also considerably impaired. After reconstitution of wild-type BRCA1 in the HCC1937 cells however, downregulation of PLK mRNA as well as Plk1 protein expression after IR was restored. Moreover, the suppression of PLK mRNA expression 6 h after irradiation was completely abolished by the specific CHEK1 kinase inhibitor UCN-01, further indicating that the effector mechanism of DNA damage on PLK signals through BRCA1 and its downstream CHEK1. Our observations provide new information about the diversity of regulatory mechanisms governed by BRCA1 in DNA damage checkpoint control.

BRCA1 Protein↗

PubMed2003

The metalloproteinase inhibitor TIMP-2 is down-regulated by androgens in LNCaP prostate carcinoma cells.

Tissue inhibitors of metalloproteinases (TIMPs) have been shown to perform several biological functions in tumor promotion, principally by their action of inhibiting matrix metalloproteinases (MMPs) at different steps of the metastatic process. In particular, TIMP-2 is involved in a functional complex with the membrane-type 1 (MT1) MMP to convert the secreted MMP-2 progelatinase into the fully active proteolytic enzyme. We used the human, androgen-sensitive prostate carcinoma cell line LNCaP in coculture with the human osteosarcoma cell line OHS to experimentally address the possibility of androgen-dependent regulatory effects on the functional MT1-MMP/TIMP-2/MMP-2 complex upon interaction between prostate carcinoma and osteoblastic cells in metastasis of prostate cancer to bone. In the LNCaP cells a gradual, time-dependent decline in TIMP-2 mRNA expression was observed in the presence of the synthetic androgen analogue R1881 (100 nM), reaching approximately 25% of the control level after 48 h of incubation. Consistent with this, the accumulation of secreted TIMP-2 in media from R1881-treated cells was significantly inhibited already after 3 h. Neither MMP-2 gelatinolytic activity nor expression of MT1-MMP was detected in LNCaP cells. In contrast, the OHS cells showed membrane-associated MT1-MMP expression as well as MMP-2 secretion. However, R1881 treatment of the LNCaP/OHS coculture model did not seem to change the overall proteolytic activity of the MT1 -MMP/TIMP-2/MMP-2 complex. Hormonal control of TIMP-2 expression in prostate carcinoma cells has not been previously reported, but whether such regulation has any functional role in the development of osteoblastic metastases in prostate cancer is still unclear.

Androgens↗

PubMed2002

Differential display analysis of breast carcinoma cells enriched by immunomagnetic target cell selection: gene expression profiles in bone marrow target cells.

The red bone marrow (BM) is an important indicator organ of hematogenous micrometastatic spread of carcinomas. Characterization of biological properties specific for BM micrometastatic cells, however, is technically challenging due to the limited number of target cells usually available for the purpose. This report provides referrals to qualitative gene expression profiling of BM micrometastatic cells enriched by immunomagnetic selection. First, an experimental strategy was used to study regulatory mechanisms involved when BM micrometastatic cells colonize distant organs. The MA-11 cells, originating from BM micrometastases in a breast cancer patient clinically devoid of overt metastatic disease, were injected into immunodeficient rats. Metastatic MA-11 cells were subsequently immunoselected from the resulting in vivo lesions. The selected cell populations were compared to the injected cells by differential display analysis, and several genes possibly involved in tumor cell invasion and proliferation were confirmed as differentially expressed among the various MA-11 cell populations. A direct approach to qualitative gene expression profiling of BM micrometastatic cells was also explored. Carcinoma cells were immunoselected from BM and axillary lymph nodes obtained from breast cancer patients, and the isolated cell populations were compared by differential display analysis. Two candidate genes, identified as factors involved in cellular growth control, appeared as differentially expressed by the target cells from BM. Our study provides detailed information on how to combine an immunomagnetic selection procedure and differential display analysis to reveal gene expression profiles that may characterize BM micrometastatic cells.

Animals↗

PubMedDate not supplied

Clinical and cell line specific expression profiles of a human gene identified in experimental central nervous system metastases.

Some cancers, particularly malignant melanomas and carcinomas of the breast and lung, metastasize to the central nervous system (CNS) in advanced stages. In order to develop into clinically manifest metastases, hematogenously disseminated tumor cells must respond to trophic factors within the CNS microenvironment. We have previously identified a nuclearfactor, com1, expressed in human breast carcinoma cells upon formation of experimental metastatic tumors in the CNS. In the present study distinct com1 mRNA expression was detected in cerebral metastases from patients with lung carcinomas, whereas the expression level was generally much lower in glioblastomas (primary brain tumors). In tissue specimens from normal brain and lung, as well as in glioma and lung carcinoma cell lines, com1 expression was barely detectable. One potential mechanism involved in the induction of com1 expression was indicated in the metastatic MCF7/LCC2 breast carcinoma cells. Significant increases in the level of com1 mRNA were observed upon activation of receptor tyrosine kinase signaling, which is known to operate during metastatic tumor cell proliferation within the CNS. The observations in this study strengthen the assumption that com1 may be involved in the tumor cell response to regulatory signals upon metastasis formation.

Basic Helix-Loop-Helix Proteins↗

PubMedDate not supplied

Ionizing radiation inhibits the PLK cell cycle gene in a G2 checkpoint-dependent manner.

Tumor cell cycle arrest at the cell cycle G2/M boundary after ionizing radiation involves inhibition of the Polo-like kinase 1 (Plk1). We recently found that the mechanism comprised repression of its gene, PLK, mediated by the tumor-suppressor protein BRCA1. In the present study we examined the regulatory responses on PLK and cell cycle phases in breast carcinoma cell lines exposed to various modes of therapeutic irradiation. The tumor cells, harboring different DNA damage checkpoint defects, were irradiated with either a single dose of 8.0 Gy or fractionated doses accumulating to 8.0 Gy. In the BRCA1-/- HCC1937 cell line both radiation regimens caused moderate repression of PLK mRNA expression, whereas the reconstituted wild-type (wt) BRCA1 genotype of the HCC1937/BRCA1wt cell line was associated with significant down-regulation of PLK mRNA expression after irradiation. In contrast to the HCC1937 cell lines, the MCF7/LCC2 cells displayed the characteristic wt TP53 constitution of persistent, radiation-induced CDKN1A mRNA expression (encoding the G1 cell cycle inhibitor p21(Waf1/Cip1/Sdi1)). The regulatory effects on PLK in the MCF7/LCC2 cells, however, were identical to those in the HCC1937/BRCA1wt cell line. Moreover, whereas neither HCC1937 cell line displayed G1/S cell cycle arrest after irradiation but, instead, an apparent accumulation of G2/M-phase cells, the radiation-induced delay at the G1/S boundary seemed to be superior to arrest at the G2/M transition in the MCF7/LCC2 cell line. Since the down-regulation of PLK mRNA expression by ionizing radiation was identical in the wt TP53 MCF7/LCC2 cell line and the TP53-mutated BRCA1-/- HCC1937 cell line reconstituted with wt BRCA1, we conclude that this regulatory effect solely requires an intact G2 checkpoint effector mechanism.

Breast Neoplasms↗

PubMedDate not supplied

DNA damage responses in cell cycle G2 phase and mitosis--tracking and targeting.

BACKGROUND: In order to determine temporal responses of cell cycle populations to DNA damage, a rational combination of cell cycle analyses is critical. Moreover, the targeting of cell cycle checkpoint responses may modify the cytotoxic effect of DNA damage. MATERIALS AND METHODS: The characteristics of cell cycle populations (DNA content, cell cycle transitioning of S phase cells and size of mitotic cell fraction within the total G2/M phase population) in HeLa cells exposed to ionizing radiation were analyzed using three individual flow cytometry-based assays. The potential radiosensitization from inhibiting DNA damage responses was assessed by the colony formation assay. RESULTS: Irradiation resulted in an initial accumulation of S phase cells in G2 phase, from which the arrested cells were subsequently released to enter mitosis. Upon drug inhibition of G2 checkpoint signaling or mitotic progression, the cytotoxic effect of ionizing radiation on the HeLa cells was amplified. CONCLUSION: DNA damage-induced cell cycle responses, analyzed by selected cytometry assays and modified by specific targeting, might contribute to an understanding of how to improve radiotherapy outcome.

Cell Division↗