To determine if tumorous FasL expression is required for preferential accumulation of TCR1045/Fas-4-1BBtm T cells, we generated tumor-bearing mice with wild type ID8VEGF or E9 ID8VEGFFasL-/- cells and co-transferred P14 T cells expressing TCR1045 or TCR1045/Fas-4-1BBtm. The gene discussed is FASLG; the disease is neoplasm.