Adoptive immunotherapy with tumor-infiltrating lymphocytes (TIL) and interleukin-2 (IL-2) has been reported to mediate tumor regression in some human cancers. To define better the biologic characteristics of TIL, especially survival and distribution in vivo, we performed a gene-marker study in patients with advanced malignancies.

We treated five patients with metastatic melanoma or renal cell carcinoma with adoptive immunotherapy. TIL were genetically modified, before their infusion, using a recombinant retroviral vector that contained the marker gene coding for resistance to neomycin (NeoR).

All of the patients tolerated the treatment well and none of the theoretic safety hazards due to the retroviral gene transduction was observed. The presence of the NeoR gene in TIL was detected by Southern blot analysis, with an efficiency of transduction that ranged from 1% to 26%. With polymerase chain reaction (PCR) analysis, we demonstrated that gene-modified TIL can survive for several months after reinjection, since positive blood samples were observed up to day 260 following reinjection. Eight malignant biopsy specimens were obtained from three patients after cell infusion. TIL were detected in only four of these eight tumor deposits on days 7 and 260.

These results confirm the feasibility and safety of using in vitro retroviral gene transduction in human lymphocytes to analyze their in vivo distribution for further therapeutic applications. However, a selective and prolonged retention of TIL at the tumor site was not found in this study.