T cells targeting carcinoembryonic antigen can mediate regression of metastatic colorectal cancer but induce severe transient colitis

Abstract

Autologous T lymphocytes genetically engineered to express a murine T cell receptor (TCR) against human carcinoembryonic antigen (CEA) were administered to three patients with metastatic colorectal cancer refractory to standard treatments. All patients experienced profound decreases in serum CEA levels (74-99%), and one patient had an objective regression of cancer metastatic to the lung and liver. However, a severe transient inflammatory colitis that represented a dose limiting toxicity was induced in all three patients. This report represents the first example of objective regression of metastatic colorectal cancer mediated by adoptive T cell transfer and illustrates the successful use of a TCR, raised in human leukocyte antigen (HLA) transgenic mice, against a human tumor associated antigen. It also emphasizes the destructive power of small numbers of highly avid T cells and the limitations of using CEA as a target for cancer immunotherapy.

Figure 1

Cancer-related responses to treatment. (a) Carcinoembryonic antigen (CEA) protein levels in sequential serum samples from each patient. Levels are expressed as the percent of the pretreatment concentrations shown in Table 1, and values in parentheses are the lowest concentrations achieved in each patient in µg/l. (b) Computed tomography scans for patient 3 prior to treatment and 4 months post-treatment. Arrows represent locations of colorectal cancer metastases, and the asterisk indicates a liver defect at a site of liver metastasis previously treated with radiofrequency ablation (RFA). Top and middle rows: patient 3 liver. Bottom row: patient 3 paraaortic lymph nodes.

Figure 2

Sequential colonoscopy findings for patient 2 during treatment. Top row: sequential images from colonoscopies performed prior to treatment (d-10) as well as 7, 10, and 17 days post-treatment. Middle row: hematoxylin and eosin staining of consecutive colon biopsies obtained prior to treatment (d-10) as well as 7 and 17 days post-treatment. The inset in the first panel shows staining of the pretreatment biopsy with a monoclonal antibody against carcinoembryonic antigen, and arrows indicate positive expression. Bottom row: staining of consecutive colon biopsies obtained prior to treatment (d-10) as well as 7 and 17 days post-treatment with a monoclonal antibody against human CD3.

Figure 3

Analyses of sequential biopsies and peripheral blood samples during treatment. (a) Biopsies from each patient were obtained during colonoscopy and endoscopy procedures at the indicated time points after adoptive transfer of autologous peripheral blood lymphocytes (PBL) transduced to express a carcinoembryonic antigen (CEA) reactive T cell receptor (TCR). DNA was extracted from these specimens, and quantitative PCR was then performed to determine the amount of retroviral DNA present in biopsy specimens. The number of retroviral DNA sequences present in each sample was normalized to the amount of β-actin DNA and expressed as a percent relative to that present in the adoptively transferred PBL using the comparative C_T method. In addition, nonquantitative PCR was also performed on samples from patient 1 using specific distal 5′ (α chain V region) and 3′ (β chain C region) primers to amplify the full-length TCR αβ construct encoding the murine CEA-reactive TCR. The PCR products were then separated using a precast 2% agarose ethidium bromide gel (Invitrogen) (top panel inset). Txd, transduced; UT, untransduced; Esoph, esophagus; Stom, stomach; Duod, duodenum. (b) Biopsies from patient 3 were obtained during colonoscopy and endoscopy procedures 7 days after adoptive transfer of autologous PBL transduced to express the CEA reactive TCR. Biopsy specimens were disrupted using a BD Medimachine and/or passage through a 40 µm nylon filter to obtain single cell suspensions. These were then stained with anti-CD3, -CD8, -CD4, and –murine TCR β chain constant region antibodies and analyzed by fluorescence-activated cell sorting. The results shown were gated on CD3+ T cells, and the numbers indicate the percentages of cells in each quadrant. (c) Interferon (IFN)-γ protein levels in consecutive serum samples from each patient were determined by enzyme-linked immunosorbent assay. APC, antigen presenting cells; FITC, fluorescein isothiocyanate.