Onset of neoplastic phenotype in an epithelial cell strain from adult BALB/c mouse lung alveolus.

Prolonged culture of NAL1A in 1 microM dexamethasone (CAS: 50-02-2) at low passage numbers resulted in the emergence of a morphologically altered and malignant cell strain, NAL1AM. (NAL1A was derived from lungs of normal adult female inbred BALB/c mice and exhibits several characteristics of epithelial cells.) A clone of NAL1A, B5, was shown to undergo a spontaneous morphologic alteration during culture in normal medium to resemble NAL1AM and cells of NUL1, a strain cultured directly from urethane (CAS: 51-79-6)-induced adenomas of mouse lung. Whereas NAL1A did not form colonies in soft agar, the clone B5 of NAL1A as well as NAL1AM and NUL1 showed quite high anchorage-independent growth (colony-forming efficiency, 6.3-7.8%). Compared with NAL1A cells, clone B5, NAL1AM, and NUL1 each exhibited a ninefold-reduced level of cellular binding of epidermal growth factor.