Luciferase activities examined 42 hours post-transfection of pSGTax2531 constructs from samples 17-months post-inoculation were not significantly different from background levels generated by the control vector pSGc, confirming the transactivation-deficient phenotype associated with the genetic change observed in the tumor-derived proviral tax. As expected, constructs expressing tax sequences isolated from earlier samples, before the onset of leukemia, were consistently positive (Fig. 1A,B). The gene discussed is CNTN2; the disease is leukemia.