Antibody-indocyanin conjugates for immunophotodetection of human squamous cell carcinoma in nude mice.

We have recently shown that immunophotodetection of human colon carcinomas in nude mice and in patients is possible by using anti-carcinoembryonic antigen monoclonal antibodies (MAb) coupled to fluorescein. The most common clinical application of photodiagnosis has been for the detection of squamous cell carcinomas (SCC) in the upper respiratory tract, but the free dyes used have a poor tumor selectivity. We selected the known MAb E48 directed against SCC and coupled it to a fluorescent dye: indopentamethinecyanin (indocyanin). This dye has an advantage over fluorescein in that it emits a more penetrating fluorescent red signal at 667 nm after excitation with a laser ray of 640 nm. In vitro, an conjugate with an indocyanin:MAb molar ratio of 2, and an additional trace labeling with 125I, showed more than 80% of binding to cells from the SCC line A431. In vivo, when injected i.v. into nude mice bearing xenografts of the same carcinoma line, the MAb E48-(indocyanin)2 conjugate was almost as efficient as the unconjugated MAb E48 in terms of specific tumor localization: 15% of the injected dose per g of tumor at 24 h after injection and a tumor:overall normal tissue ratio of 6-8. There was no selective tumor localization of an irrelevant IgG1-(indocyanin)2 conjugate. Immunophotodetection of the s.c. SCC xenografts on mice given injections of 100 micrograms of MAb E48-(indocyanin), conjugate (representing 1 microgram of indocyanin) was performed at 24 h. Upon laser irradiation, clearly detectable red fluorescence from the indocyanin-MAb conjugate was observed specifically in the SCC xenografts across the mouse skin. In comparison, injection of 100 micrograms of a MAb E48 coupled to 2 micrograms of fluorescein gave a specific green fluorescence signal in the tumor xenografts, which was detectable, however, only after removing the mouse skin. Injection i.v. of a 15 times higher amount of free indocyanin (15 micrograms) gave a diffuse red fluorescence signal all over the mouse body with no definite increase in intensity in the tumor, indicating a lack of tumor selectivity of the free dye. The results demonstrate the possibility of broadening and improving the efficiency of tumor immunophotodiagnosis by coupling to a MAb directed against SCC, a fluorescent dye absorbing and emitting at higher wavelength than fluorescein, and thus having deeper tissue penetration and lower tissue autofluorescence. Such a demonstration opens the way to a new form of clinical immunophotodiagnosis and possibly to the development of a more specific approach to phototherapy of early bronchial carcinomas.

Neoadjuvant and adjuvant strategies in renal cell carcinoma: more questions than answers.

The current standard treatment for early stage (I-III) renal cell cancer (RCC) is surgery. While the prognosis of stage I tumors is excellent, stage II and particularly stage III have a high risk of relapse. The adjuvant treatment of patients with RCC remains an area of investigation, with patient selection being a key aspect. There are currently two prognostic nomograms to establish the risk of relapse in patients with resected RCC. The results of earlier studies of adjuvant therapy, including the use chemotherapy and/or immunotherapy after nephrectomy have failed to show any benefit in the outcome of patients at risk of developing local recurrence or distant metastases. Two recent phase III trials with vaccines (autologous tumor cell vaccine and autologous tumor-derived heat shock protein peptide complex-96) have shown promising, albeit still preliminary, results. In the metastatic RCC setting, recent advances in the molecular understanding of oncogenic pathways have led to the development of new therapeutic strategies with the use of targeted therapies in the adjuvant setting. Neoadjuvant treatment is another treatment modality currently being evaluated for patients with early disease and in patients with metastatic RCC with inoperable primary tumors. The questions that remain unanswered include activity of these agents in early stages of the disease, patient selection, optimal start time of the adjuvant treatment, and finally, the optimal length of treatment.

Radioimmunotherapy of human colon carcinoma by 131I-labelled monoclonal anti-CEA antibodies in a nude mouse model.

A mixture of 3 MAbs directed against 3 different CEA epitopes was radiolabelled with 131I and used for the treatment of a human colon carcinoma transplanted s.c. into nude mice. Intact MAbs and F(ab')2 fragments were mixed because it had been shown by autoradiography that these 2 antibody forms can penetrate into different areas of the tumor nodule. Ten days after transplantation of colon tumor T380 a single dose of 600 microCi of 131I MAbs was injected i.v. The tumor grafts were well established (as evidenced by exponential growth in untreated mice) and their size continued to increase up to 6 days after radiolabelled antibody injection. Tumor shrinking was then observed lasting for 4-12 weeks. In a control group injected with 600 microCi of 131I coupled to irrelevant monoclonal IgG, tumor growth was delayed, but no regression was observed. Tumors of mice injected with the corresponding amount of unlabelled antibodies grew like those of untreated mice. Based on measurements of the effective whole-body half-life of injected 131I, the mean radiation dose received by the animals was calculated to be 382 rads for the antibody group and 478 rads for the normal IgG controls. The genetically immunodeficient animals exhibited no increase in mortality, and only limited bone-marrow toxicity was observed. Direct measurement of radioactivity in mice dissected 1, 3 and 7 days after 131I-MAb injection showed that 25, 7.2 and 2.2% of injected dose were recovered per gram of tumor, the mean radiation dose delivered to the tumor being thus more than 5,000 rads. These experiments show that therapeutic doses of radioactivity can be selectively directed to human colon carcinoma by i.v. injection of 131I-labelled anti-CEA MAbs.

Iodine-131-labeled MAb F(ab')2 fragments are more efficient and less toxic than intact anti-CEA antibodies in radioimmunotherapy of large human colon carcinoma grafted in nude mice.

During one week, beginning 18 days after transplantation, nude mice bearing human colon carcinoma ranging from 115 to 943 mm3 (mean 335 mm3) were treated by repeated intravenous injections of either iodine-131-(131I) labeled intact antibodies or 131I-labeled corresponding F(ab')2 fragments of a pool of four monoclonal antibodies (MAbs) directed against distinct epitopes of carcinoembryonic antigen (CEA). Complete tumor remission was observed in 8 of 10 mice after therapy with F(ab')2 and 6 of the animals survived 10 mo in good health. In contrast, after treatment with intact MAbs, tumors relapsed in 7 of 8 mice after remission periods of 1 to 3.5 mo despite the fact that body weight loss and depression of peripheral white blood cells, symptoms of radiation toxicity, and the calculated radiation doses for liver, spleen, bone, and blood were increased or equal in these animals as compared to mice treated with F(ab')2.

Molecular determinants of vesicular storage and release of the gliotransmitter D-serine from cortical astrocytes

Neuron-astrocyte reciprocal communication at synapses has emerged as a novel signalling pathway in brain function. Astrocytes sense the level of synaptic activity and, in turn, influence its efficacy through the regulated release of 'gliotransmitters' such as glutamate, ATP or D-serine. A calcium-dependent exocytosis is proposed to drive the release of gliotransmitters but its existence is still debated. Over the last years, we have been studying the molecular determinants governing D-serine release from glia using different approaches. Using a novel bioassay for D-serine, we have been able to show that D-serine release occurs mainly through a calcium- and SNARE proteindependent mechanism just supporting the idea that this amino acid is released by exocytosis from glia. We next have pursued our exploration by confocal imaging and tracking of the exocytotic routes for Dserine- mediated gliotransmission and have shown that D-serine releasable pools are confined to synaptobrevin2/cellubrevin-bearing vesicles. To shed light onto the mechanisms controlling the storage and the release of gliotransmitters and namely D-serine, we have developed a new method for the immunoisolation of synaptobrevin 2- positive vesicles from rat cortical astrocytes in culture while preserving their content in gliotransmitters. The purified organelles are clear round shape vesicles of excellent purity with homogeneous size (40 nm) as judged by electron microscopy. Immunoblotting analysis revealed that isolated vesicles contain most of the major proteins already described for neuron-derived vesicles like synaptic vesicle protein 2 (SV2) and the proton pump H?-ATPase. In addition, we have analyzed the content for various amino acids of these vesicles by means of chiral capillary electrophoresis coupled to laser-induced fluorescence detection. The purified vesicles contain large amount of D-serine. We also detect peaks corresponding to unidentified compounds that may correspond to others amino acids. Postembedding immunogold labelling of the rat neocortex further revealed the expression of D-serine in astrocytes processes contacting excitatory synapses. Finally, we have examined the uptake properties for Dserine and glutamate inside the isolated glial vesicles. Our results provide significant support for the existence of an uptake system for D-serine in secretory glial vesicles and for the storage of chemical substances like D-serine and glutamate. 11th International Congress on Amino Acids, Peptides and Proteins 763 123

Effects of mineralocorticoid and K+ concentration on K+ secretion and ROMK channel expression in a mouse cortical collecting duct cell line.

The cortical collecting duct (CCD) plays a key role in regulated K(+) secretion, which is mediated mainly through renal outer medullary K(+) (ROMK) channels located in the apical membrane. However, the mechanisms of the regulation of urinary K(+) excretion with regard to K(+) balance are not well known. We took advantage of a recently established mouse CCD cell line (mCCD(cl1)) to investigate the regulation of K(+) secretion by mineralocorticoid and K(+) concentration. We show that this cell line expresses ROMK mRNA and a barium-sensitive K(+) conductance in its apical membrane. As this conductance is sensitive to tertiapin-Q, with an apparent affinity of 6 nM, and to intracellular acidification, it is probably mediated by ROMK. Overnight exposure to 100 nM aldosterone did not significantly change the K(+) conductance, while it increased the amiloride-sensitive Na(+) transport. Overnight exposure to a high K(+) (7 mM) concentration produced a small but significant increase in the apical membrane barium-sensitive K(+) conductance. The mRNA levels of all ROMK isoforms measured by qRT-PCR were not changed by altering the basolateral K(+) concentration but were decreased by 15-45% upon treatment with aldosterone (0.3 or 300 nM for 1 and 3 h). The paradoxical response of ROMK expression to aldosterone could possibly work as a preventative mechanism to avoid excessive K(+) loss which would otherwise result from the increased electrogenic Na(+) transport and associated depolarization of the apical membrane in the CCD. In conclusion, mCCD(cl1) cells demonstrate a significant K(+) secretion, probably mediated by ROMK, which is not stimulated by aldosterone but increased by overnight exposure to a high K(+) concentration.

Intraepithelial carcinoma of the oesophagus: endoscopic morphology.

The endoscopic detection of 18 "early" hypopharyngo-oesophageal carcinomas, has allowed us to perform a detailed study of the morphological correlation between endoscopy and histology (in 10 cases). We have thus defined 4 different endoscopic types of intraepithelial carcinomas; their morphology, mapping and evolution are greatly variable. In high risk groups (heavy smoking and alcohol consumption, ENt-cancer) the multicentricity of intraepithelial carcinomas (80%) entails a thorough endoscopic screening of the upper digestive tract (mouth, pharynx, oesophagus) and of the lower respiratory tract (larynx, trachea and bronchi).

Dimeric recombinant IgA directed against carcino-embryonic antigen, a novel tool for carcinoma localization.

Carcinoembryonic antigen (CEA) has been shown to be one of the best markers for in vivo tumor targeting of radiolabeled antibodies, despite the fact that it is localized predominantly at the apical side of human colon carcinoma cells within the fairly closed pseudolumen structures formed by these tumors. Due to this particular histological localization, a large proportion of the CEA molecules may remain inaccessible to the intravenously injected radiolabeled anti-CEA antibodies of IgG isotype, which are widely used in the clinic. In order to improve targeting, we made a recombinant dimeric IgA, which should have the capacity to translocate from the basolateral to the apical side of the pseudolumen formed by colon carcinoma cells after binding to the polyIg receptor (pIgR). A genomic chimeric mouse-human IgA2 construct was made using one of our most specific anti-CEA hybridomas, CE-25. The chimeric IgA (chIgA) was expressed in the Sp2/0 myeloma cell line. The secreted recombinant antibody was found to consist mostly of a dimeric form of IgA with a molecular weight of about 350 kDa. The dimeric chIgA was shown to translocate efficiently in vitro across a monolayer of epithelial cells expressing the pIgR and to retain full CEA binding activity.