Normal growth and differentiation in a spontaneously immortalized near-diploid human keratinocyte cell line, NIKS

We report the isolation and characterization of a spontaneously immortalize d human keratinocyte cell line, NIKS. The cell line is not tumorigenic in a thymic nude mice and maintains cell-type-specific requirements for growth i n vitro. NIKS cells express steady-state levels of transforming growth fact or-alpha, transforming growth factor-beta 1, epidermal growth factor recept or, c-myc, and keratin 14 mRNAs comparable with the parental BC-1-Ep kerati nocyte strain. BC-1-Ep and NIKS keratinocytes produce similar levels of cor nified envelopes and nucleosomal fragmentation in response to loss of subst rata attachment. DNA fingerprinting results confirm that the NIKS cells ori ginated from the parental BC-1-Ep keratinocytes. NIKS cells contain 47 chro mosomes due to an extra isochromosome of the long arm of chromosome 8, and the near-diploid karyotype appears to be stable with repeated passage. A fu lly stratified squamous epithelium is formed by the NIKS keratinocytes in o rganotypic culture. Ultrastructural analysis of both the parental and immor talized keratinocytes reveals abundant desmosomes, hemidesmosomes, and the production of a basal lamina. Our findings with the NIKS cells support the observation that spontaneous immortalization is not linked to alterations i n squamous differentiation or the ability to undergo apoptosis. The NIKS hu man keratinocyte cell line is an important new tool for the study of growth and differentiation in stratified squamous epithelia.