Stability of transplanted murine tumour systems after storage of cells at -196 degrees C for up to 13 years.

Two murine lymphomas of spontaneous origin were stored in liquid N2 as cell suspensions in DMSO for 8 and 13 years respectively. Isogenic transplantation assays done some years before freezing and immediately after thawing indicated no measurable loss of clonogenic cells during freezing, storage or thawing; the number of cells required for 50% successful transplantation remained close to unity in both cases. The overall data revealed no evidence of an alteration of the receptivity of the mouse colonies over a period of 13 or 20 years. We attribute this remarkable stability to close supervision of the systems within a single laboratory.