The hallmarks of cancer.

Human blastocyst-derived, pluripotent cell lines are described that have normal karyotypes, express high levels of telomerase activity, and express cell surface markers that characterize primate embryonic stem cells but do not characterize other early lineages. After undifferentiated proliferation in vitro for 4 to 5 months, these cells still maintained the developmental potential to form trophoblast and derivatives of all three embryonic germ layers, including gut epithelium (endoderm); cartilage, bone, smooth muscle, and striated muscle (mesoderm); and neural epithelium, embryonic ganglia, and stratified squamous epithelium (ectoderm). These cell lines should be useful in human developmental biology, drug discovery, and transplantation medicine.

Embryonic Stem Cell Lines Derived from Human Blastocysts

http://www.klinikaikozpont.u-szeged.hu/pedia/images/pdf/CME_TEL/Full-Text/25.pdf

The Hallmarks of Aging

NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Sixty-third Session, Supplement No. 46. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. Scientific Annexes Annex A. Medical radiation exposures Annex B. Exposures of the public and workers from various sources of radiation INTROdUCTION 1. In the course of the research and development for and the application of atomic energy and nuclear technologies, a number of radiation accidents have occurred. Some of these accidents have resulted in significant health effects and occasionally in fatal outcomes. The application of technologies that make use of radiation is increasingly widespread around the world. Millions of people have occupations related to the use of radiation, and hundreds of millions of individuals benefit from these uses. Facilities using intense radiation sources for energy production and for purposes such as radiotherapy, sterilization of products, preservation of foodstuffs and gamma radiography require special care in the design and operation of equipment to avoid radiation injury to workers or to the public. Experience has shown that such technology is generally used safely, but on occasion controls have been circumvented and serious radiation accidents have ensued. 2. Reviews of radiation exposures from accidents have been presented in previous UNSCEAR reports. The last report containing an exclusive chapter on exposures from accidents was the UNSCEAR 1993 Report [U6]. 3. This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices. Its conclusions are to be seen in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation. 4. The Committee's evaluations of public, occupational and medical diagnostic exposures are mostly concerned with chronic exposures of …

sources and effects of ionizing radiation

Cells continually experience stress and damage from exogenous and endogenous sources, and their responses range from complete recovery to cell death. Proliferating cells can initiate an additional response by adopting a state of permanent cell-cycle arrest that is termed cellular senescence. Understanding the causes and consequences of cellular senescence has provided novel insights into how cells react to stress, especially genotoxic stress, and how this cellular response can affect complex organismal processes such as the development of cancer and ageing.

Cellular senescence: when bad things happen to good cells

Normal human cells undergo a finite number of cell divisions and ultimately enter a nondividing state called replicative senescence. It has been proposed that telomere shortening is the molecular clock that triggers senescence. To test this hypothesis, two telomerase-negative normal human cell types, retinal pigment epithelial cells and foreskin fibroblasts, were transfected with vectors encoding the human telomerase catalytic subunit. In contrast to telomerase-negative control clones, which exhibited telomere shortening and senescence, telomerase-expressing clones had elongated telomeres, divided vigorously, and showed reduced staining for β-galactosidase, a biomarker for senescence. Notably, the telomerase-expressing clones have a normal karyotype and have already exceeded their normal life-span by at least 20 doublings, thus establishing a causal relationship between telomere shortening and in vitro cellular senescence. The ability to maintain normal human cells in a phenotypically youthful state could have important applications in research and medicine.

/pdf/extension-of-life-span-by-introduction-of-telomerase-into-4ucjiz7vl1.pdf

Extension of life-span by introduction of telomerase into normal human cells

Expression of the human telomerase catalytic component, hTERT, in normal human somatic cells can reconstitute telomerase activity and extend their replicative lifespan We report here that at twice the normal number of population doublings, telomerase-expressing human skin fibroblasts (BJ-hTERT) and retinal pigment epithelial cells (RPE-hTERT) retain normal growth control in response to serum deprivation, high cell density, G1 or G2 phase blockers and spindle inhibitors In addition, we observed no cell growth in soft agar and detected no tumour formation in vivo Thus, we find that telomerase expression in normal cells does not appear to induce changes associated with a malignant phenotype

Telomerase expression in human somatic cells does not induce changes associated with a transformed phenotype

Human telomerase reverse transcriptase (hTERT) is the catalytic component of a functional telomerase complex, which is important in maintaining cell immortality. In most normal human adult cells, the expression of telomerase is very low and/or transient. In contrast, almost 90% of human tumors express a relatively high level of telomerase implying the possibility of using hTERT as a universal candidate tumor antigen. In this study, we show that human monocyte-derived dendritic cells (DCs) lack telomerase activity. Similar to other normal somatic cells, DCs express the RNA (hTR) component but not the catalytic component, hTERT. We also show that telomerase activity could be reconstituted using either lipid-mediated transfection of the hTERT plasmid DNA or transduction with an E1-, E3-deleted adenoviral vector containing the hTERT gene. However, relative to plasmid transfection, adenoviral gene transfer produced higher levels of hTERT expression. Nine of 10 AdhTERT-transduced DCs were able to generate CTL responses, while only three of nine plasmid-transfected DCs did. CTLs primed against hTERT exhibited killing of telomerase positive but not telomerase negative tumor lines of diverse tissue origins. Antigenic specificity of these T cells to telomerase was further determined by introducing hTERT gene into a telomerase negative cell line, U2OS, by adenoviral transduction. Although some antigenic specificity was directed against adenoviral epitopes, the majority of CTLs were targeted against telomerase-derived antigen(s). Thus, the hTERT gene, particularly as delivered via the recombinant adenovirus, may be useful as vaccine to induce specific T-cell-mediated tumor immunity in cancer patients. In addition, our results suggest that telomerase activity and/or telomerase expression after hTERT gene transfer have a predictive value in the success of hTERT/DC-based cancer vaccination.

Dendritic cells reconstituted with human telomerase gene induce potent cytotoxic T-cell response against different types of tumors.

It has been discovered that a robust and therapeutic anti-cancer response can be generated by immunizing with a xenogeneic form of the enzyme telomerase reverse transcriptase (TERT). Cancer subjects are multiply immunized with TERT from another species—either in protein form, or with a TERT expression vector. Presence of the xenogeneic components apparently overcomes natural immunotolerance to self-antigen. The response can be focused by simultaneous or subsequent immunization with isogenic TERT. As a result, the immune system generates T lymphocytes that are cytotoxic for virtually any cancer cell, by virtue of TERT expressed due to malignant transformation. The anti-tumor response causes a substantial inhibition of tumor cell growth, demonstrating the therapeutic benefit of this invention.

Cancer vaccines containing xenogeneic epitopes of telomerase reverse transcriptase

It has been discovered that a robust and therapeutic anti-cancer response can be generated by immunizing with a xenogeneic form of the enzyme telomerase reverse transcriptase (TERT). Cancer subjects are multiply immunized with TERT from another species-either in protein form, or with a TERT expression vector. Presence of the xenogeneic components apparently overcomes natural immunotolerance to self-antigen. The response can be focused by simultaneous or subsequent immunization with isogenic TERT. As a result, the immune system generates T lymphocytes that are cytotoxic for virtually any cancer cell, by virtue of TERT expressed due to malignant transformation. The anti-tumor response causes a substantial inhibition of tumor cell growth, demonstrating the therapeutic benefit of this invention.

Maria Frolkis

Papers

Extension of life-span by introduction of telomerase into normal human cells

Telomerase expression in human somatic cells does not induce changes associated with a transformed phenotype

Dendritic cells reconstituted with human telomerase gene induce potent cytotoxic T-cell response against different types of tumors.

Cancer vaccines containing xenogeneic epitopes of telomerase reverse transcriptase

Cancer vaccine containing cross-species epitopes of telomerase reverse transcriptase