Creation of human tumour cells with defined genetic elements

Abstract

During malignant transformation, cancer cells acquire genetic mutations that override the normal mechanisms controlling cellular proliferation. Primary rodent cells are efficiently converted into tumorigenic cells by the coexpression of cooperating oncogenes. However, similar experiments with human cells have consistently failed to yield tumorigenic transformants, indicating a fundamental difference in the biology of human and rodent cells. The few reported successes in the creation of human tumour cells have depended on the use of chemical or physical agents to achieve immortalization, the selection of rare, spontaneously arising immortalized cells, or the use of an entire viral genome. We show here that the ectopic expression of the telomerase catalytic subunit (hTERT) in combination with two oncogenes (the simian virus 40 large-T oncoprotein and an oncogenic allele of H-ras) results in direct tumorigenic conversion of normal human epithelial and fibroblast cells. These results demonstrate that disruption of the intracellular pathways regulated by large-T, oncogenic ras and telomerase suffices to create a human tumor cell.

The ecology of brain tumors: lessons learned from neurofibromatosis-1

“…These include growth signal selfsufficiency, antigrowth signal insensitivity, apoptosis evasion, limitless replicative potential, angiogenesis, and tissue invasion and metastasis (Hanahan and Weinberg, 2000). In their model, the introduction of human telomerase reverse transcriptase, oncogenic H-Ras and simian virus 40 large T-antigen in normal human kidney epithelial and fibroblast cells conferred limitless replicative potential, growth signal self-sufficiency and apoptosis evasion, respectively, and resulted in oncogenic transformation (Hahn et al, 1999). Similarly, this collection of genetic alterations was also shown to be sufficient for the transformation of normal astrocytes to malignant astrocytomas (Sonoda et al, 2001).…”

Regulation of telomerase activity by the p53 family member p73

“…This lack of telomerase activity is considered to be a major obstacle in the transformation of human cells. For example, primary human fibroblasts lack telomerase activity and are resistant to transformation, whereas its hTERT-transfected derivative is readily transformed to tumorigenicity by the simian virus SV40 early region and oncogenic H-rasV12 (Hahn et al, 1999). Inactivation of tumor suppressors that repress telomerase expression (e.g.…”

Mitochondria as therapeutic targets for cancer chemotherapy

“…Multistep tumorigenesis, as recapitulated in vitro, is intrinsically linked to apoptosis resistance (Hahn et al, 1999), progressive dependence on glycolytic energy production and independence from mitochondrial energy production (Ramanathan et al, 2005). On theoretical grounds, there are two mechanisms that can link the Warburg phenomenon to MOMP inhibition.…”