Clonal variation in phenotype and life span of human embryonic fibroblasts(MRC-5) transduced with the catalytic component of telomerase (hTERT)

Expression of telomerase (hTERT) in certain cell types has been shown to ex tend cellular life span without malignant transformation. We studied the ph enotype of 26 telomerase-transduced fibroblast clones (TTFC) generated from a mass culture of hTERT retrovirally transduced MRC-5 cells. About two-thi rds of the transduced clones senesced at the expected time or shortly there after, despite high levels of expression of telomerase and telomere length maintenance. The remaining one-third of the clones were "immortalized" (fol lowed for over 200 cumulative population doublings). All clones maintained a nontransformed phenotype: contact inhibition, anchorage dependency, lack of tumor formation in nude mice, dose dependency to serum and growth factor s, low expression of a matrix metalloproteinase associated with metastatic invasion (MMP-9) and high expression of its inhibitor TIMP-1, and no cytoge netic abnormalities by G-banding. In addition, fibroblast-specific biologic al parameters, such as colony size, production of collagenase, and response to MMC and gamma radiation were tightly regulated at the clonal and subclo nal levels. (C) 2001 Academic Press.