Ronald M. Bukowski

Multicenter, Randomized, Phase III Trial of CD8+ Tumor-Infiltrating Lymphocytes in Combination With Recombinant Interleukin-2 in Metastatic Renal Cell Carcinoma

PURPOSEnTo prospectively evaluate in a multicenter randomized trial the antitumor activity of CD8(+) tumor-infiltrating lymphocytes (TILs) in combination with low-dose recombinant interleukin-2 (rIL-2), compared with rIL-2 alone, after radical nephrectomy in metastatic renal cell carcinoma patients.nnnPATIENTS AND METHODSnBetween December 1994 and March 1997, 178 patients with resectable primary tumors were enrolled at 29 centers in the United States and Europe. Patients underwent total nephrectomy, recovered, and were randomized to receive either CD8(+) TILs (5 x 10(7) to 3 x 10(10) cells intravenously, day 1) plus rIL-2 (one to four cycles: 5 x 10(6) IU/m(2) by continuous infusion daily for 4 days per week for 4 weeks) (TIL/rIL-2 group) or placebo cell infusion plus rIL-2 (identical regimen) (rIL-2 control group). Primary tumor specimens were cultured at a central cell-processing center in serum-free medium containing rIL-2 to generate TILs.nnnRESULTSnOf 178 enrolled patients, 160 were randomized (TIL/rIL-2 group, n = 81; rIL-2 control group, n = 79). Twenty randomized patients received no treatment after nephrectomy because of surgical complications (four patients), operative mortality (two patients), or ineligibility for rIL-2 therapy (14 patients). Among 72 patients eligible for TIL/rIL-2 therapy, 33 (41%) received no TIL therapy because of an insufficient number of viable cells. Intent-to-treat analysis demonstrated objective response rates of 9.9% v 11.4% and 1-year survival rates of 55% v 47% in the TIL/rIL-2 and rIL-2 control groups, respectively. The study was terminated early for lack of efficacy as determined by the Data Safety Monitoring Board.nnnCONCLUSIONnTreatment with CD8(+) TILs did not improve response rate or survival in patients treated with low-dose rIL-2 after nephrectomy.

Molecular Mechanisms of Immune Dysfunction in Renal Cell Carcinoma

The development of an effective host immune response against neoplastic cells requires activation of T cells following recognition of tumor-associated antigens expressed on the appropriate antigen presenting cells (1). The generation of a cell-mediated cellular response typically involves CD8+ T cells that recognize peptides presented by MHC class I whereas CD4+ T cells recognize peptides presented by major histocompatibility complex (MHC) class II along with the appropriate costimulatory molecules (B7.1 and B7.2). Activation of the Th1 CD4+ cells leads to the production of cytokines such as interleukin-2 (IL-2) that provides a critical signal for clonal expansion of antigen activated lymphocytes. IL-2 signaling also upregulates expression of effector molecules (granzyme B and pore forming protein) requisite for the cytolytic function of CD8+ T cells. Another critical cytokine is gamma-interferon (IFNγ), produced by both Th1 CD4+ and a subset of CD8+ T cells, that further promotes the development of a cellular response by enhancing MHC and costimulatory molecule expression as well as by activating macrophages. Activation of T-cell immunity is dependent on normal intracellular signaling through the T-cell receptor and subsequent downstream induction of a variety of transcriptional factors that regulate gene expression of cytokines, chemokines, and receptors involved in T-cell responses (1, 2).

CD4+ T-Cell-Mediated Immunity to Cancer

A major clinical focus has been dedicated to the design and application of immunotherapies for the promotion of antitumor cytotoxic T lymphocyte (CTL) responses (1,2). In their purest form, such strategies take the form of adoptively transferred, enriched populations of tumor-reactive CD8+ T cells. These approaches have occasionally been shown to be capable of mediating the regression of lesions in cancer patients (3). However, more often, high circulating frequencies of such cancer-specific CD8+ T cells fail to provide any demonstrable clinical benefit, despite the co-application of supportive biologic response modifiers, such as interleukin-2 (IL-2) (4,5). Although it is not the purpose of this chapter to survey all of the potential mechanisms that may underlie the ineffectiveness of such immune effector cells in situ, one must consider deviation in the functional antitumor CD4+ T “helper” compartment as a major confounding variable.

Alterations in T-Cell Signaling Pathways and Increased Sensitivity to Apoptosis

Despite the presence of antigens on tumors, studies suggest that that the antitumor immune response is attenuated. Well-recognized immune dysfunction in T cells of tumor-bearing hosts is most pronounced in tumor-infiltrating lymphocytes (TIL), and is characterized by impaired proliferation and reduced cytotoxic effector function (1). Some in vivo gene expression studies suggest that in the tumor microenvironment, there is minimal induction of inflammatory responses involving the expression of IFN-γ and IL-2 mRNA,(2,3) In a subset of patients, diminished T-cell function has also been observed in the peripheral blood, which is mostly associated with reduced production of TH1 type cytokines (e.g., IFN-γ) following stimulation of peripheral-blood T cells with mitogens or anti-CD3 antibody (4).