Creation of human tumour cells with defined genetic elements

During malignant transformation, cancer cells acquire genetic mutations tha t override the normal mechanisms controlling: cellular proliferation. Prima ry rodent cells are efficiently converted into tumorigenic cells by the coe xpression of cooperating oncogenes(1,2). However, similar experiments with human cells have consistently failed to yield tumorigenic transformants(3-5 ), indicating a fundamental difference in the biology of human and rodent c ells. The few reported successes in the creation of human tumour cells have depended on the use of chemical or physical agents to achieve immortalizat ion(6), the selection of rare, spontaneously arising immortalized cells(7-1 0), or the use of an entire viral genome(11). We show here that the ectopic expression of the telomerase catalytic subunit (hTERT)(12) in combination with two oncogenes (the simian virus 40 large-T oncoprotein and an oncogeni c 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 telo merase suffices to create a human tumor cell.