Benign and invasive tumors induced in Drosophila by an inherited tumor-inducing factor.

The injection of the tu-e (spontaneous tumor strain) tumor-inducing factor into the wild 51-52 (genetically tumor-free strain) hosts induces the formation of melanotic tumors (4, 8). The induced wild 51-52 and the spontaneous tu-e tumors are histologically similar (4). The spindle-shaped tu mor cells and tumors have never been observed in histological sections of wild 51-52 animals unless they have been injected with the tumor-inducing factor (2, 4). In an earlier investigation, possible differences between tumors induced by the tumor-inducing factor in crude and purified preparations were ob served (2). This communication elucidates some aspects of these differences.