Prevention of Interleukin-2 Withdrawal-Induced Apoptosis in Lymphocytes Retrovirally Cotransduced With Genes Encoding an Antitumor T-cell Receptor and an Antiapoptotic Protein

Adoptive cell transfer using autologous tumor infiltrating lymphocytes or lymphocytes transduced with antitumor T-cell receptor (TCR) is an effective therapy for patients with metastatic melanoma. A limiting factor in the effectiveness of this treatment is the apoptosis of the transferred cells when Interleukin-2 (IL-2) administration is withdrawn. In an attempt to improve persistence of the transferred lymphocytes, we cotransduced human peripheral blood lymphocytes with retroviruses encoding Bcl-2 or Bcl-xL, antiapoptotic genes of the BCL2 family, and the MART-1 melanoma tumor antigen-specific TCR, DMF5. Lymphocytes were cotransduced with 38% to 64% cotransduction efficiency, and exhibited a marked delay in apoptosis after IL-2 withdrawal. Cotransduction with Bcl-2 or Bcl-xL did not affect cytokine secretion or lytic ability of the DMF5-transduced lymphocytes. After 5 days of IL-2 withdrawal, cotransduced lymphocytes produced similar levels of IFN-γ per cell as DMF5-alone transduced lymphocytes in response to tumor cells. Cotransduction did not alter the phenotype of lymphocytes with respect to a panel of T-cell differentiation markers. In a mouse model of melanoma, adoptively transferred T cells transduced with Bcl-2 persisted better in vivo at the site of tumor, 13 and 21 days after adoptive transfer (P=0.0064 and 0.041, respectively), with evidence of enrichment of the Bcl-2-transduced population over time (P<0.0001). Thus, by coexpressing Bcl-2 or Bcl-xL with a tumor-specific TCR, we have engineered a lymphocyte that resists apoptosis owing to IL-2 withdrawal without altering its tumor-specific function or phenotype, and thus may show improved antitumor effectiveness in vivo after cell transfer.