Functional striated muscle cells from non-myoblast precursors following 5-azacytidine treatment

Abstract

5-AZACYTIDINE (aza-CR)—a s-triazine nucleoside analogue of cytidine—has strong inhibitory effects in various biological systems including neoplasms: it is a powerful bacteriostatic, antitumour and mutagenic agent¹. Aza-CR also exhibits immunosuppressive, antimitotic, radioprotective and virostatic effects¹. The cytostatic effect of aza-CR has primarily been directed against leukaemia² and it has been used to treat human solid tumours³. During a study on the morphological transformation of C3H 10T½ C18 cells by cancer chemotherapeutic agents, it was noted that elongated multinucleated cells arose in cultures exposed to aza-CR⁴. The C3H 10T½ C18 line is a clonal line of mouse embryo cells developed at the McArdle Laboratory for Cancer Research for use in studies on chemical oncogenesis in vitro^5–10. The cells are highly sensitive to post-confluence inhibition of cell division, show a remarkably low rate of spontaneous transformation and grow with a fibroblast-like morphology with long cytoplasmic processes in sparse cultures. When confluent, they form flat even monolayers and appear epithelioid. Scanning electron microscopy has shown the confluent cells to be extremely thin and polygonal with smooth surfaces resembling epithelial cells¹¹. Here we describe experiments showing that the multinucleated tubular cells which arise in C3H 10T½ C18 cells treated with aza-CR are in fact functional myotubes.