Marked differences in the tumor uptake of a 125I-labeled monoclonal antibody (MAb) directed against carcinoembryonic antigen (CEA) were observed in 4 serially transplanted human colorectal carcinomas in nude mice. A comparative study showed that elevated values of measurable tumor vascular parameters, such as permeability, blood flow and blood volume, correlated better with high MAb tumor uptake than the concentration of target antigen in the tumor. In an attempt to modify the vascular parameters and to determine if this could increase antibody uptake by the tumor, rhTNF alpha (TNF) was injected i.t. or i.v. and antibody localization experiments were performed immediately thereafter. Results showed that the permeability of the tumor vessels increased 8 to 10 fold 1 hr after i.t. injection of TNF as compared to control tumors injected with saline. Tumor uptake of 125I-labeled anti-CEA MAb, was 3 times higher 2 hr after i.v. injection and still 27% higher 22 hr later, as compared to results from controls. Intravenous injection of TNF simultaneously with the 125I-labeled anti-CEA MAb also resulted in a 2-fold increase in tumor uptake 4 hr after injection, but the increase was no longer significant 24 hr after injection. Interestingly after i.v. injection of TNF, the MAb concentration in the blood and other normal tissues, such as liver, kidneys, lungs and heart was decreased, resulting in significantly higher ratios of tumor to normal tissue. Taken together the results demonstrate that injection of TNF can increase tumor vascular permeability and improve radio-antibody uptake. This raises the possibility of increasing the radiation dose delivered by antibody to the tumor in the course of radioimmunotherapy.

Based on previous experiments in nude mice, showing that fluoresceinated monoclonal antibodies against carinoembryonic antigen localized specifically in human carcinoma xenografts and could be detected by laser-induced fluorescence, we performed a feaibilit study to determine whether this immunopho method could be applied in the clinic. Six patients, with known primary colorectal carcinoma, received an i.v. injection of 4.5 or 9 mg of mousehuman chimeric anti-carcinoembryonic antigen monoclonal antibody coupled with 0.10-0.28 mg offluorescein (molar ratio 1/10 to 1/14). The monoclonal antibody was also labeled with 0.2-0.4 mCi of 12-I (1 Ci = 37 GBq). Photodetection of the tumor was done ex vivo on surgically resected tissues for the six patients and in vivo by fluorescence rectosigmoidoscopy for the sixth patient. Upon laser irradiation, ciearly detectable heterogeneous green fluorescence from the dye-antibody conjugate was visually observed on all six tumors; almost no such fluorescence was detectable on normal mucosa. The yellowish tissue autofluorescence, which was emitted from both tumor and normal mucosa, could be subtracted by real-time image processing. Radioactivity measurements confirmed the specificity of tumor localization by the conjugate; tissue concentrations of up to 0.059% Injected dose per g of tumor and 10 times les (0.006%) per g of normal mucosa were found. The overall results demonstrate the feasibility of tumor immunophotodiagnosis at the clinical level.chlorins, have been coupled to monoclonal antibodies (mAbs), but these conjugates were studied primarily in vitro (6)(7)(8), and the few experimental immunophototherapy studies did not yield highly significant results (9). The obvious advantage of using mAbs as vectors for tumor localization of dyes is the ability of a mAb to bind specifically to an antigen that is more abundant in tumor than in normal tissue. Furthermore, this technique allows selection of the dye on the basis of its photophysical and spectral properties, independently of its weak tumor-localizing properties.We chose human-mouse chimeric mAb directed against carcinoembryonic antigen (CEA) (10) because anti-CEA antibodies have given the best experimental and clinical results for colorectal carcinoma localization (11, 12) and chimeric mAbs were less immunogenic in patients than their murine counterpart (13). We selected fluorescein as the dye, primarily for its favorable photophysical properties, as shown in the innumerable in vitro applications of mAb-fluorescein conjugates and secondly because it can be injected in large doses into patients without side effects (14).We have previously shown that anti-CEA mAb-fluorescein conjugates injected i.v. in nude mice bearing human colon carcinoma xenografts allow clear immunophotodetection of these tumors (15). The purpose of the present pilot clinical trial was to determine whether such type of tumor immunophotodiagnosis is feasible in patients.Despite major progress in understanding the process of malignant transformation ...

In a model of nude mice bearing a human colon carcinoma xenograft, the biodistribution and tumor localization of meta‐tetrahydroxyphenylchlorin (m‐THPC) coupled to polyethylene glycol (PEG) were compared with those of the free form of this photosensitizer used in photodynamic therapy (PDT). At different times after i.v. injection of both forms of 125I‐labeled photosensitizer, m‐THPC‐PEG gave on average a 2‐fold higher tumor uptake than free m‐THPC. In addition, at early times after injection, m‐THPC‐PEG showed a 2‐fold longer blood circulating half‐life and a 4‐fold lower liver uptake than free m‐THPC. The tumor to normal tissue ratios of radioactivity concentrations were always higher for m‐THPC‐PEG than for free m‐THPC at any time point studied from 2 to 96 hr post‐injection. Significant coefficients of correlation between direct fluorescence measurements and radioactivity counting were obtained within each organ tested. Fluorescence microscopy studies showed that m‐THPC‐PEG was preferentially localized near the tumor vessels, whereas m‐THPC was more diffusely distributed inside the tumor tissue. To verify whether m‐THPC‐PEG conjugate remained phototoxic in vivo, PDT experiments were performed 72 hr after injection and showed that m‐THPC‐PEG was as potent as free m‐THPC in the induction of tumor regression provided that the irradiation dose for m‐THPC‐PEG conjugate was adapted to a well‐tolerated 2‐fold higher level. The overall results demonstrate first the possibility of improving the in vivo tumor localization of a hydrophobic dye used for PDT by coupling it to PEG and second that a photosensitizer conjugated to a macromolecule can remain phototoxic in vivo. Int. J. Cancer 76:842–850, 1998.© 1998 Wiley‐Liss, Inc.

To improve the detectability of tumors by light-induced fluorescence, the use of monoclonal antibodies (MoAb) as carriers of fluorescent molecules was studied. As a model for this approach, the biodistribution of an anticarcinoembryonic antigen (CEA) MoAb coupled to fluorescein was studied in mice bearing a human colon carcinoma xenograft. In vitro, such conjugates with fluorescein-MoAb molar ratios ranging from four to 19, doubly labeled with 125I, showed more than 82% binding to immobilized CEA. In vivo, conjugates with a fluorescein-MoAb molar ratio of ten or less resulted in a tumor uptake of more than 30% of the injected dose of radioactivity per gram tumor at 24 hours. Tumor to liver, kidney, and muscle ratios of 20, 30 and 72, respectively, were obtained 48 hours after injection of the 125I-MoAb-(fluorescein)10 conjugate. The highest fluorescence intensity was always obtained for the tumor with the anti-CEA MoAb conjugate; whereas in control mice injected with fluoresceinated control immunoglobulin G1, no detectable increase in tumor fluorescence was observed. To compare these results with a classically used dye, mice bearing the same xenografts received 60 micrograms of Photofrin II. The intensity of the fluorescence signal of the tumor with this amount of Photofrin II was eight times lower than that obtained after an injection of 442 ng of fluorescein coupled with 20 micrograms of MoAb, which gave an absolute amount of fluorescein localized in the tumor of up to 125 ng/g of tumor. These results illustrate the possibility of improving the specificity of in vivo tumor localization of dyes for laser-induced fluorescence photodetection and phototherapy by coupling them to MoAb directed against tumor markers.