Comparison of aluminium (III) phthalocyanine tetrasulfonate- and meta-tetrahydroxyphenylchlorin-monoclonal antibody conjugates for their efficacy in photodynamic therapy in vitro

A challenge in photodynamic therapy (PDT) is to improve the tumour selectivity of the photosensitizers by using monoclonal antibodies (MAbs). With this aim, we developed MAb-conjugates with the hydrophobic photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC) and with the hydrophilic sensitizer aluminium (III) phthalocyanine tetrasulfonate (AlPcS(4)). The capacity of these photoimmunoconjugates for selective targeting of squamous cell carcinoma (SCC) in vivo was demonstrated previously in SCC-bearing nude mice. Preliminary in vitro PDT studies with the vulvar SCC cell line A431 showed promising phototoxicity with both sensitizers when coupled to the internalizing MAb 425. To rank the photosensitizers for their potential in photoimmunotherapy, we herein describe an extensive in vitro evaluation of mTHPC-MAb and AlPcS(4)-MAb conjugates. Both classes of conjugates were directly compared using 5 different SCC cell lines as target and 3 different MAbs (BIWA 4, E48 and 425) for tumour cell targeting. In contrast to free AlPcS(4) (IC(50) > or = 700 nM), MAb-conjugated AlPcS(4) was found to be highly phototoxic in PDT in all 5 cell lines. AlPcS(4)-BIWA 4 was most consistently effective with IC(50) values ranging from 0.06-5.4 nM. mTHPC-MAb conjugates were in general hardly effective. Phototoxicity (log IC(50)) of the AlPcS(4)-MAb conjugates was found to be strongly correlated with their total cell binding capacity (internalized and surface bound) and to be less correlated with their internalization capacity. In conclusion, these data show a high potential of AlPcS(4)-MAb conjugates in comparison to mTHPC-MAb conjugates for use in PDT.     

Targeting of aluminum (III) phthalocyanine tetrasulfonate by use of internalizing monoclonal antibodies: improved efficacy in photodynamic therapy

The use of monoclonal antibodies (MAbs) directed against tumor-associated antigens for targeting of photosensitizers is an interesting option to improve the selectivity of photodynamic therapy (PDT). Hydrophilic photosensitizers are most suitable for conjugation to MAbs because of their water solubility. The photosensitizer aluminum (III) phthalocyanine tetrasulfonate [AlPc(SO3H)4] has many ideal photochemical properties; however, because of its hydrophilicity, the free form of this sensitizer does not readily reach the critical intracellular target and, therefore, is ineffective in PDT. On the basis of our previous studies, we hypothesized that AlPc(SO3H)4 might be suitable for PDT when coupled to internalizing tumor-selective MAbs. In this study, a reproducible procedure is presented for coupling of AlPc(SO3H)4 to MAbs via the tetra-glycine derivative AlPc(SO2Ngly)4. Conjugation was performed to chimeric MAb (cMAb) U36 and murine MAbs (mMAb) E48 and 425 using a labile ester. Conjugates showed preservation of integrity and immunoreactivity and full stability in serum in vitro. At molar ratios >4, the solubility of the conjugates decreased. Data on the in vitro efficacy of PDT showed that in the chosen experimental setup the internalizing AlPc(SO2Ngly)4-mMAb 425 conjugate was about 7500 times more toxic to A431 cells than the free sensitizer (IC50s, 0.12 nM versus 900 nM). The AlPc(SO2Ngly)4-mMAb 425 conjugate was also more toxic than meta-tetrahydroxyphenylchlorin-mMAb 425 conjugates and free meta-tetrahydroxyphenylchlorin that had been tested previously (M. B. Vrouenraets et al., Cancer Res., 59: 1505-1513, 1999) in the same system (IC50s, 7.3 nm and 2.0 nM, respectively). Biodistribution analysis of AlPc(SO2Ngly)4-125I-labeled cMAb U36 conjugates with different sensitizer:MAb ratios in squamous cell carcinoma-bearing nude mice revealed selective accumulation in the tumor, although to a lesser extent than for the unconjugated 125I-labeled cMAb U36, whereas tumor:blood ratios were similar. These findings indicate that AlPc(SO3H)4 has high potential for use in PDT when coupled to internalizing tumor-selective MAbs.     

A novel CD44v6 targeting antibody fragment with improved tumor-to-blood ratio

The chimeric monoclonal antibody U36 (cMAb U36) recognizes the CD44v6 antigen. Its potential as a radioimmunotargeting agent, as well as its safety, has been shown in previous studies in head and neck cancer patients. However, intact MAbs have long circulation time in the blood and tumor targeting may also be hampered due to the slow and incomplete diffusion into solid tumors. In comparison, smaller monovalent Fab' and divalent F(ab')2 fragments are expected to exhibit shorter circulating half-lives, better tumor penetration and are thus more likely to yield better imaging results. In this study, novel F(ab')2 and Fab' fragments from cMAb U36 were radiolabeled with 125I and the characteristics of the conjugates in?vitro were examined. The biodistribution of the conjugates were then evaluated in nude mice bearing CD44v6-expressing xenograft tumors. Furthermore, the penetration depth and distribution in tumor tissue was assessed by autoradiography in selected tumor samples. The in?vitro experiments showed that the conjugates were stable and had intact affinity to CD44v6. The biodistribution study demonstrated superior tumor-to-blood ratio for the novel cMAb U36 fragment 125I-F(ab')2 compared with both the intact MAb and the monovalent fragment form. Autoradiography also revealed better tumor penetration for 125I-F(ab')2. This study demonstrates that the use of antibody fragments may improve radioimmunotargeting and possibly improve the management of head and neck malignancies.     

Selection of monoclonal antibody E48 IgG or U36 IgG for adjuvant radioimmunotherapy in head and neck cancer patients.

Preliminary data from recent clinical radioimmunoscintigraphy studies indicate that 99mTc-labelled murine monoclonal antibodies (MAbs) E48 and U36 have a similar ability to target squamous cell carcinoma of the head and neck (HNSCC) selectively. In the present study we describe additional aspects of murine and chimeric MAb (mMAb and cMAb) E48 and U36, which might influence the selection of one MAb for adjuvant radioimmunotherapy. To make direct comparison possible, ten patients received 11.2 +/- 0.3 and 11.1 +/- 0.2 mg (n = 5) or 51.1 +/- 0.1 and 51.0 +/- 0.4 mg (n = 5) of both mE48 IgG and mU36 IgG labelled with 131I and 125I simultaneously and underwent surgery 7-8 days after injection. The mean uptake of iodine-labelled mE48 IgG and mU36 was highest in tumour tissue, 8.9 +/- 8.9 and 8.2 +/- 4.4 %ID kg(-1) respectively. Tumour to non-tumour ratios for oral mucosa, skin, muscle, blood and bone marrow aspirate were 2.5, 5.5, 25.2, 4.7 and 4.0 respectively in the case of mE48 IgG and 2.3, 4.1, 21.0, 5.8 and 5.8 respectively in the case of mU36 IgG. The distribution of mMAbs E48 and U36 throughout tumours that had been collected in previous studies was heterogeneous when administered at a dose of 1 or 12 mg, and homogeneous when administered at a dose of 52 mg. Administration of mE48 IgG (1-52 mg) resulted in a human anti-mouse antibody response in 12 out of 28 patients, while for mU36 IgG (1-52 mg), this figure was three out of 18 patients. cMAb E48 was shown to be highly effective in mediating antibody-dependent cellular cytotoxicity in vitro, while cMAb U36 and mMAbs E48 and U36 were not effective at all. Rationales are provided that give priority to the start of adjuvant radioimmunotherapy trials with 186Re-labelled cMAb U36 IgG in head and neck cancer patients who are at high risk for the development of locoregional recurrences and distant metastases.     

Targeting of a hydrophilic photosensitizer by use of internalizing monoclonal antibodies: A new possibility for use in photodynamic therapy

Coupling of photosensitizers to tumor-selective monoclonal antibodies (MAbs) is an attractive option for improving the selectivity of photodynamic therapy (PDT). For this purpose, hydrophilic sensitizers would be most suitable because of their solubility in water. However, such sensitizers are known to be ineffective in PDT, probably because they cannot readily pass the cell membrane and reach the critical intracellular target. We used the model compound TrisMPyP-PhiCO(2)H, a hydrophilic porphyrin derivative, to test the hypothesis that hydrophilic photosensitizers might become of therapeutic value when directed into the tumor cell by use of internalizing MAbs. TrisMPyP-PhiCO(2)H was conjugated using a labile ester. Conjugates showed no impairment of integrity on SDS-PAGE, full stability in serum in vitro, and optimal immunoreactivity when the sensitizer:MAb ratio was 相似文献   

Radioimmunotherapy of human head and neck squamous cell carcinoma xenografts with 131I-labelled monoclonal antibody E48 IgG.

Monoclonal antibody (MAb) E48 reacts with a 22 kD antigen exclusively expressed in squamous and transitional epithelia and their neoplastic counterparts. Radiolabelled with 99mTc, MAb E48 is capable of targeting metastatic and recurrent disease in patients with head and neck cancer. In this study, the capacity of 131I-labelled MAb E48 to eradicate xenografts of human squamous cell carcinoma of the head and neck (HNSCC) in nude mice was examined. Experimental groups received a single i.v. bolus injection of 400 microCi MAb E48 IgG (number of mice (n = 6, number of tumours (t) = 9) or 800 microCi MAb E48 IgG (n) = 5,t = 7), whereas control groups received either diluent (n = 3,t = 5), unlabelled MAb E48 IgG (n = 4,t = 5) or 800 microCi 131I-labelled isotype-matched control MAb (n = 6,t = 9). A 4.1-fold increase in the median tumour volume doubling time and regression of two out of ten tumours (20%) was observed in mice treated with 400 microCi. In mice treated with 800 microCi. In mice treated with 800 microCi, two out of seven tumours (29%) showed complete remission without regrowth during follow-up (greater than 3 months). Median tumour volume doubling time in the remaining five tumours was increased 7.8-fold. No antitumour effects were observed in mice injected with diluent, unlabelled MAb E48 or 131I-labelled control MAb. In the same xenograft model, chemotherapy with doxorubicin, 5-fluorouracil, cisplatin, bleomycin, methotrexate or 2',2'-difluorodeoxycytidine yielded a less profound effect on tumour volume doubling time. Increases in tumour volume doubling time with these chemotherapeutic agents were 4, 2.2, 2.1, 1.7, 0, and 2.6 respectively. Moreover, no cures were observed with any of these chemotherapeutic agents. From the tissue distribution of 800 microCi MAb E48, the absorbed cumulative radiation doses of tumour and various organs were calculated using the trapezoid integration method for the area under the curve. To tumour xenografts, 12,170 cGy was delivered, blood received 2,984 cGy, whereas in every other tissue the accumulated dose was less than 6% of the dose delivered to tumour. These data, describing the first radiolabelled MAb with therapeutic efficacy against HNSCC, suggest radioimmunotherapy with MAb E48 to be a potential therapeutic modality for the treatment of head and neck cancer.     

The development and characterisation of porphyrin isothiocyanate-monoclonal antibody conjugates for photoimmunotherapy

A promising approach to increase the specificity of photosensitizers used in photodynamic therapy has been through conjugation to monoclonal antibodies (MAb) directed against tumour-associated antigens. Many of the conjugations performed to date have relied on the activated ester method, which can lead to impure conjugate preparations and antibody crosslinking. Here, we report the development of photosensitizer-MAb conjugates utilising two porphyrin isothiocyanates. The presence of a single reactive isothiocyanate allowed facile conjugation to MAb FSP 77 and 17.1A directed against internalizing antigens, and MAb 35A7 that binds to a non-internalizing antigen. The photosensitizer-MAb conjugates substituted with 1-3 mol of photosensitizer were characterised in vitro. No appreciable loss of immunoreactivity was observed and binding specificity was comparable to that of the unconjugated MAb. Substitution with photosensitizer had a minimal effect on antibody biodistribution in vivo for the majority of the conjugates, although a decreased serum half-life was observed using a cationic photosensitizer at the higher loading ratios. Tumour-to-normal tissue ratios as high as 33.5 were observed using MAb 35A7 conjugates. The internalizing conjugate showed a higher level of phototoxicity as compared with the non-internalizing reagent, using a cell line engineered to express both target antigens. These data demonstrate the applicability of the isothiocyanate group for the development of high-quality conjugates, and the use of internalizing MAb to significantly increase the photodynamic efficiency of conjugates during photoimmunotherapy.     

Tumor reactive cis-aconitylated monoclonal antibodies coupled to daunorubicin through a peptide spacer are unable to kill tumor cells

Antibody-drug conjugates containing a linkage susceptible to lysosomal hydrolases were constructed by coupling peptide-daunorubicin (DNR) derivatives to MAb. Using a modification in the method of Trouet et al, peptide derivatives of DNR containing the sequences Ala-Leu and Ala-Leu-Ala-Leu linked to drug via their carboxy terminus were prepared. Cleavage of these derivatives by lysosomal enzymes resulting in the release of free DNR was demonstrated. Human antitumor MAb were derivatized with either succinic anhydride or cis-aconitic anhydride to introduce spacer arms for coupling. Binding studies showed that MAb with a decrease of 12-20 amino groups retained greater than 70% of their immunoreactivity, a level deemed acceptable for constructing conjugates. Derivatized and native MAb were conjugated to peptide-DNR via a carbodiimide mediated reaction. None of the conjugates displayed cytotoxicity toward target tumor cell lines in vitro.     

Uptake and localisation of mTHPC (Foscan) and its 14C-labelled form in normal and tumour tissues of the hamster squamous cell carcinoma model: a comparative study

The aim of this study was to evaluate the pharmacokinetics of meta(tetrahydroxyphenyl)chlorin (mTHPC) on different tissues of interest in a hamster tumour model and to confirm our earlier animal studies on semi-quantitative fluorescence microscopy. The results obtained by three different evaluation methods were compared: in vivo spectrofluorometry, ex vivo fluorescence microscopy and chemical extraction of (14)C-labelled mTHPC. Following intracardiac injection of 0.5 mg kg(-1) mTHPC, groups of five tumour-bearing animals were used for in situ light-induced fluorescence spectroscopy. Afterwards, the biopsies were taken and snap frozen for fluorescence microscopy. The presence of radioactivity in serum and tissues was determined after chemical digestion in scintillation fluid using a scintillation counter. For each analysed tissue, a good correlation was observed between the three evaluation methods. The highest fluorescence intensity and quantities of mTHPC were observed between 12 and 24 h in liver, kidney, serum, vascular endothelium and advanced neoplasia. The majority of mTHPC was found at around 48 h in smooth muscle and at 96 h in healthy cheek pouch mucosa and early malignant lesions. The lowest level of mTHPC was noted in striated muscle at all times. No selectivity in dye localisation was observed between early squamous cell carcinoma and healthy mucosa. Soon after the injection, a significant selectivity was noted for advanced squamous cell carcinoma as compared to healthy cheek pouch mucosa or striated muscle. A significant difference in mTHPC localisation and quantity was also observed between striated and smooth muscle during the first 48 h following the injection. Finally, this study demonstrated the usefulness of non-invasive in situ spectroscopic measurements to be performed systematically prior to photodynamic therapy as a real-time monitoring for each treated patient in order to individualise and adapt the light dosimetry and avoid over or under treatments.     

Long-lived positron emitters zirconium-89 and iodine-124 for scouting of therapeutic radioimmunoconjugates with PET

Antibody-PET imaging might be of value for the selection of radioimmunotherapy (RIT) candidates to confirm tumor targeting and to estimate radiation doses to tumor and normal tissues. One of the requirements to be set for such a scouting procedure is that the biodistributions of the diagnostic and therapeutic radioimmunoconjugates should be similar. In the present study we evaluated the potential of the positron emitters zirconium-89 ((89)Zr) and iodine-124 ((124)I) for this approach, as these radionuclides have a relatively long half-life that matches with the kinetics of MAbs in vivo (t(1/2) 3.27 and 4.18 days, respectively). After radiolabeling of the head and neck squamous cell carcinoma (HNSCC)-selective chimeric antibody (cMAb) U36, the biodistribution of two diagnostic (cMAb U36-N-sucDf-(89)Zr and cMAb U36-(124)I) and three therapeutic radioimmunoconjugates (cMAb U36-p-SCN-Bz-DOTA-(88)Y-with (88)Y being substitute for (90)Y, cMAb U36-(131)I, and cMAb U36-MAG3-(186)Re) was assessed in mice with HNSCC-xenografts, at 24, 48, and 72 hours after injection. Two patterns of biodistribution were observed, one pattern matching for (89)Zr- and (88)Y-labeled cMAb U36 and one pattern matching for (124)I-, (131)I-, and (186)Re-cMAb U36. The most remarkable differences between both patterns were observed for uptake in tumor and liver. Tumor uptake levels were 23.2 +/- 0.5 and 24.1 +/- 0.7%ID/g for the (89)Zr- and (88)Y-cMAb U36 and 16.0 +/- 0.8, 15.7 +/- 0.79 and 17.1 +/- 1.6%ID/g for (124)I-, (131)I-, and (186)Re-cMAb U36-conjugates, respectively, at 72 hours after injection. For liver these values were 6.9 +/- 0.8 ((89)Zr), 6.2 +/- 0.8 ((88)Y), 1.7 +/- 0.1 ((124)I), 1.6 +/- 0.1 ((131)I), and 2.3 +/- 0.1 ((186)Re), respectively. These preliminary data justify the further development of antibody-PET with (89)Zr-labeled MAbs for scouting of therapeutic doses of (90)Y-labeled MAbs. In such approach (124)I-labeled MAbs are most suitable for scouting of (131)I- and (186)Re-labeled MAbs.     

Monoclonal antibody 44-3A6 doxorubicin immunoconjugates: comparative in vitro anti-tumor efficacy of different conjugation methods.

Doxorubicin (Dox) was coupled by four published methods to a murine monoclonal antibody (MAb) developed against human pulmonary adenocarcinoma. Dox immunoconjugates made with this murine IgG1 MAb, 44-3A6, were evaluated for anti-tumor activity against the human lung cancer cell line, A549. Dox was attached to the MAb (1) by an oxidized dextran T40 intermediate, (2) using dilute glutaraldehyde cross-linking, (3) with an acid-sensitive linker using cis-aconitic anhydride and EDCI, a water-soluble carbodiimide, and (4) using EDCI alone. The biological activity of the different conjugates was compared in vitro by antigen binding (whole-cell RIA) versus serial dilutions of unconjugated MAb cytotoxicity (dye exclusion/viability) versus long dilutions of the various Dox conjugates, Dox and mixtures of Dox and MAb. Preincubation of antigen-expressing tumor cells (A549) for 2 h with excess (250 micrograms/ml) unconjugated MAb prior to conjugate exposure was attempted in order to block the cytotoxic effect. The number of Dox molecules conjugated to 44-3A6 (molar incorporation ratio or MIR) ranged from 3 to 10/1 for carbodiimide linkage and up to 63/1 using the dextran intermediate. Cis-aconityl-derivatized Dox conjugates contained an average of 22 mol Dox/mol immunoglobulin, but drug incorporation was quite variable from experiment to experiment. Dilute glutaraldehyde cross-linking produced an average MIR of 10/1. After repeated attempts to minimize drug and/or MAb precipitation, the percentage decrease (versus MAb) in immunoreactivity of the drug conjugates ranged from 2 to 42% and was dependent on the coupling method and extent of aggregate formation in the preparation. Loss of biological activity (antigen binding and cytotoxicity) was significant when aggregation and precipitation occurred. There were additional losses (17-25%) after sterile filtration through low protein-binding (0.22 microns) filters. Immunoconjugates produced by glutaraldehyde cross-linking were reproducibly 5-10 times more potent against antigen-bearing tumor cells than Dox, and showed selectivity for inhibiting the viability of antigen-positive A549 cell line. Noncovalent mixtures of 44-3A6 and Dox were slightly more potent than Dox. Immunoconjugates produced by the aconityl method and the dextran intermediates were less effective than Dox, the glutaraldehyde-mediated conjugates or Dox and 44-3A6 mixtures. The unconjugated MAb was not cytotoxic when tested at concentrations up to 500 micrograms/ml. Blocking studies using 'cold', unlabeled MAb were of limited success.(ABSTRACT TRUNCATED AT 400 WORDS)     

Interstitial photodynamic therapy as salvage treatment for recurrent head and neck cancer

Interstitial photodynamic therapy (IPDT) is a technique for applying photodynamic therapy (PDT) to internal tumours using light delivered via fibres inserted percutaneously. This phase I-II study assessed the safety and efficacy of IPDT for patients with persistent or recurrent head and neck cancer unsuitable for further treatment with surgery, radiotherapy or chemotherapy, recruited for 'last hope' salvage treatment. Patients were sensitised with 0.15 mg kg(-1) mTHPC (meso-tetrahydroxyphenyl chlorin) 4 days prior to light delivery from fibres inserted directly into the target tumour (20 J per site at 652 nm) under image guidance. In all, 45 patients were treated. Nine achieved a complete response. Five are alive and free of disease 10-60 months later. Symptomatic relief (mainly for bleeding, pain or tumour debulking) was achieved in a further 24. The median survival (Kaplan-Meier) was 16 months for the 33 responders, but only 2 months for the 12 nonresponders. The only serious complication was a carotid blow out 2 weeks after PDT. No loss of function was detected in nerves encased by treated tumours. Interstitial photodynamic therapy provides worthwhile palliation with few complications and occasional long-term survivors for otherwise untreatable advanced head and neck cancers. It is a treatment option worth adding to those available to integrated head and neck oncology teams.     

光敏剂间-四羟基苯二氢卟酚诱导肿瘤细胞凋亡的研究

目的：探讨体外以间-羟基苯二氢卟酚（mesotetrahydroxyphenylchlorin,mTHPC)为光敏剂的光动力诱导肿瘤细胞死亡的机制。方法：用含1.3umol/LmTHPC(0.8ug/ml)的培养液孵育人骨肉瘤细胞系（HOS-8603）存活率的变化,用共聚焦显微镜检测mTHPC在瘤细胞的分布;用Hoechst33258荧光染色显示瘤细胞的凋亡形态变化,而瘤细胞凋亡DNA片段用琼脂糖电泳检测。结果：mTHPC位于HOS-8603和JCS细胞的胞浆,经光动力治疗后,h为2.1%、2h为62.9%、4h为100.0%,而HOS-8603细胞凋亡率4h为20.2%、8h为65.9%、12h为100.0%。两种细胞在电泳中均出现特征性凋亡条带。结论：mTHPC是一种强光效应的光敏剂,能有效地进入肿瘤细胞胞浆,诱导瘤细胞死亡的方式主要是凋亡,其次是坏死。     

Tumor targeting properties of monoclonal antibodies with different affinity for target antigen CD44V6 in nude mice bearing head-and-neck cancer xenografts

The CD44 protein family consists of isoforms with tissue-specific expression, which are encoded by standard exons and up to 9 alternatively spliced variant exons (v2-v10) of the same gene. The murine MAbs U36 and BIWA-1, directed against overlapping epitopes within the v6 region of CD44, have previously been shown to efficiently target HNSCC. We herein report on the construction of 1 chimeric (BIWA-2) and 2 humanized (BIWA-4 and BIWA-8) derivatives of BIWA-1. Together with U36 and BIWA-1, these new antibodies were evaluated for affinity to the antigen in vitro as well as for biodistribution and efficacy in RIT using nude mice bearing the HNSCC xenograft line HNX-OE. As determined by surface plasmon resonance, the MAbs bound to CD44v6 with an up to 46-fold difference in affinity (K(d) ranging from 1.1 x 10(-8) to 2.4 x 10(-10) M) with the following ranking: mMAb U36 < hMAb BIWA-4 < hMAb BIWA-8 < mMAb BIWA-1 approximately cMAb BIWA-2. To evaluate their in vivo tumor-targeting properties, 2 MAbs with identical murine or human isotype were labeled with either (131)I or (125)I and administered simultaneously (50 microg/10 microCi each) as pairs showing a stepwise decrease in the difference in affinity: U36 vs. BIWA-1 (35.0-fold difference), BIWA-4 vs. BIWA-2 (14.0-fold) and BIWA-4 vs. BIWA-8 (4.0-fold). Biodistribution was assessed at 1, 2, 3 or 4 and 7 days after injection. Remarkably, for all 3 MAb pairs tested, the lower-affinity MAb showed a higher degree and specificity of tumor localization. The difference in tumor localization was more pronounced when the difference in affinity was larger. For example, 3 days after injection, the lower-affinity mMAb U36 showed a 50% higher tumor uptake than the higher-affinity mMAb BIWA-1, while blood levels and uptake in organs were similar. After labeling with (186)Re (300 or 400 microCi), the same MAb pairs showed RIT efficacy consistent with the biodistribution data: (186)Re-U36 was more effective than (186)Re-BIWA-1, (186)Re-BIWA-4 was slightly more effective than (186)Re-BIWA-2 and (186)Re-BIWA-4 and (186)Re-BIWA-8 demonstrated similar efficacy. Based on these data, we conclude that antibodies with markedly lower affinity to a given target antigen (e.g., U36, BIWA-4) may show superior tumor targeting in comparison with higher-affinity versions of these antibodies.     

Epidermal growth factor receptor-targeted immunophotodiagnosis and photoimmunotherapy of oral precancer in vivo

Immunophotodiagnosis uses a fluorescence-labeled monoclonal antibody (MAb) that recognizes a tumor-associated antigen to image the fluorescence emitted from the fluorophore-bound MAb that has localized in the tissue. It may be used to diagnose malignant or precancerous lesions, to delineate the margins for tumor resection, or as a feedback mechanism to assess response to treatment. In oral precancer, the epidermal growth factor receptor (EGFR) is overexpressed and could be used as a marker for early detection or as a target for therapy. The goal of this study was to test an anti-EGFR MAb (C225) coupled to either the near-infrared fluorescent dye N,N'-di-carboxypentyl-indodicarbocyanine-5,5'-disulfonic acid for detection or a photochemically active dye (chlorin(e6)) for therapy of early premalignancy in the hamster cheek pouch carcinogenesis model. Fluorescence levels in the carcinogen-treated tissue correlated with the histological stage of the lesions when the C225-N,N'-di-carboxypentyl-indodicarbocyanine-5,5'-disulfonic acid conjugate was used but did not do so with the irrelevant conjugates. Discrete areas of clinically normal mucosa with high fluorescence (hot spots) were subsequently shown by histology to contain dysplastic areas. The best contrast between normal and carcinogen-treated cheek pouches was found at 4-8 days after injection. To test the potential of immunophotodiagnosis as a feedback modality for therapeutic intervention, experiments were conducted with the same MAb conjugated to chlorin(e6) followed by illumination to reduce expression of the EGFR by a photodynamic effect. Subsequent immunophotodiagnosis showed that this treatment led to a significant reduction in fluorescence in the carcinogen-treated cheek pouch compared with nonilluminated areas. This difference between illuminated and dark areas was not seen in the normal cheek pouch. Taken together, the results demonstrate the potential for development of immunophotodiagnosis as a diagnostic tool and as a method of monitoring response to therapy and that the EGFR may be an appropriate target in head and neck cancer.     

In vivo and in situ imaging of head and neck squamous cell carcinoma using near-infrared fluorescent quantum dot probes conjugated with epidermal growth factor receptor monoclonal antibodies in mice

In this study, we applied near-infrared fluorescent quantum dots (NIRF-QDs) for non-invasive in vivo and in situ imaging of head and neck squamous cell carcinoma (HNSCC). The U14 squamous cancer cell line with high expression of epidermal growth factor receptor (EGFR) was implanted subcutaneously into the head and neck regions of nude mice to establish HNSCC models. NIRF-QDs with an emission wavelength of 800 nm (NIRF-QD800) were conjugated with EGFR monoclonal antibodies to develop the QD800-EGFR Ab probe. In vivo and in vitro studies demonstrated that the QD800-EGFR Ab probe can specifically bind EGFR expressed on U14 cells. U14 squamous cell carcinoma in the head and neck can be clearly visualized by in vivo imaging after intravenous injection of QD800-EGFR Ab probes. The results suggested that in situ imaging using NIRF-QD-EGFR Ab probes has unique advantages and prospects for the investigation of tumor development, early diagnosis and personalized therapy of HNSCC.     

Reinfusion of unprocessed, granulocyte colony-stimulating factor-stimulated whole blood allows dose escalation of 186Relabeled chimeric monoclonal antibody U36 radioimmunotherapy in a phase I dose escalation study.

PURPOSE: In an earlier Phase I radioimmunotherapy (RIT) study with rhenium-186-labeled chimeric monoclonal antibody (cMAb) U36 in patients with refractory head and neck squamous cell carcinoma, the maximum tolerated activity was established at 1.0 GBq/m2, at which bone marrow doses ranged from 0.7 to 1.1 Gy. In the present study, further dose escalation in RIT was evaluated using a facile method of reinfusion of granulocyte colony-stimulating factor (G-CSF)-stimulated unprocessed whole blood. EXPERIMENTAL DESIGN: Nine patients with recurrent or metastatic head and neck squamous cell carcinoma were treated at radiation dose levels of 1.0, 1.5, and 2.0 GBq/m2. Before RIT, G-CSF (10 microg/kg/day) was administered s.c. at home during 5 days. On day 6, just before administration of 186Relabeled cMAb U36, 1 liter of whole blood was harvested and kept unprocessed at 4 degrees C until reinfusion after 72 h. Blood samples were taken for analysis of pharmacokinetics and bone marrow dosimetry. Patients were evaluated for myelotoxicity and tumor response. RESULTS: Blood harvesting, RIT, and reinfusion of whole blood were well tolerated by all patients. G-CSF stimulation resulted in a mean of 0.41 x 10(6) CD34+ cells/kg (range, 0.15-0.83 x 10(6) CD34+cells/kg) and a mean committed colony-forming units granulocyte macrophage count of 5.62 x 10(4)/kg (range, 0.62-13.37 x 10(4)/kg). The mean biological half-life of 186Relabeled cMAb U36 in blood was 72.6 +/- 16.0 h, and bone marrow doses ranged from 2.1 to 2.8 Gy at the highest dose level. Myelotoxicity exceeding grade 3 was not observed. Stable disease was observed in five of nine patients, ranging from 3 to 5 months, and was still ongoing in one of these patients. CONCLUSIONS: This study indicates that a doubling of the maximum tolerated activity and bone marrow dose of 186Relabeled cMAb U36 can be achieved using reinfusion of G-CSF-stimulated unprocessed whole blood.     

Photosensitizing effects of m-tetrahydroxyphenylchlorin on human tumor xenografts: Correlation with sensitizer uptake,tumor doubling time and tumor histology

The photodynamic effects of m-tetrahydroxyphenylchlorin (mTHPC) were assessed on human malignant mesothelioma, squamous cell carcinoma and adenocarcinoma xenografts grown in nude mice and were correlated with mTHPC uptake, histology and doubling time of the tumors. Non-thermal laser light was delivered to the tumor as surface radiation 4 days after intraperitoneal administration of 0.1 and 0.3 mg mTHPC/kg body weight, respectively. The extent of tumor necrosis was measured by histomorphometry. The mTHPC concentration in non-irradiated tumors was assessed by high-performance liquid chromatography (HPLC). The tumors were graded according to their doubling time and their vascular architecture as assessed by histology. The 0.1 mg/kg dose of mTHPC resulted in an equal uptake for all 3 tumor types but revealed a larger extent of photosensitized necrosis for adenocarcinoma, which displayed a delicate tumor stroma with numerous small capillary vessels, than for mesothelioma and squamous cell carcinoma, which were both poor in stroma and vessels. The 0.3 mg/kg dose of mTHPC resulted in a 2-fold higher tumor uptake for all 3 tumor types and in a larger extent of necrosis for mesothelioma and squamous cell carcinoma, but not for adenocarcinoma xenografts, compared with the lower drug dose. Our results demonstrate that different tumor xenografts respond differently to mTHPC-PDT for a given drug-light condition. In this setting, the photosensitizing effect was more closely related to the vascular architecture of the tumors than to the sensitizer uptake and doubling time of the different tumors. Int. J. Cancer 76:872–874, 1998.© 1998 Wiley-Liss, Inc.     

Characterization of a novel monoclonal antibody, 3H-1, reactive with squamoproliferative lesions and squamous-cell cancers.

Immunization of mice with membranes from a virus-transformed human keratinocyte cell line (KJD-I/SV40) yielded an IgM monoclonal antibody (MAb 3H-I) which reacted with the membrane and cytoplasm of KJD-I/SV40 cells and in the perinuclear region of a squamous-cell carcinoma line (Colo-16). Immunohistochemistry of formalin-fixed, paraffin-embedded sections using MAb 3H-I gave intense staining of proliferating squamous epithelium in several characteristic patterns. Acanthotic squamous epithelium and well-differentiated squamous-cell carcinomas (SCC) demonstrated a membranous staining pattern whereas psoriatic skin and undifferentiated SCC of the head and neck exhibited diffuse cytoplasmic, focal cytoplasmic or, in some tumours, no staining. Simple squamous epithelium was unreactive. Western blotting revealed an antigen of 55 kDa. The epitope recognized by MAb 3H-I may be a marker for particular stages of squamous proliferation and differentiation.     

Progress in radioimmunotherapy of head and neck-cancer (review)

There is an urgent need for an effective adjuvant systemic therapy for the treatment of patients with advanced head and neck cancer. This study shows that therapy based on the use of monoclonal antibodies (MAbs) is developing to a realistic option. A few years ago the first MAbs with specificity for squamous cell carcinoma of the head and neck (HNSCC) were produced, among which was MAb E48. In animal and patient studies, in which localization of radiolabelled MAb E48 was analysed qualitatively and quantitatively, it was demonstrated that a high percentage of the injected dose accumulated selectively in the tumour. These targeting properties, when exploited for delivery of toxic agents to the tumour, give MAb E48 potential for tumour therapy. Especially the application of MAb E48 in radioimmunotherapy (RIT) seems to be attractive due to the intrinsic radiosensitivity of HNSCC. Armed with 186-Rhenium, a radionuclide recently introduced in the field of RIT, MAb E48 IgG was shown to be highly capable of eradicating established HNSCC tumours in nude mice. Complete ablation of small HNSCC was observed in this animal model by a single bolus injection. In an effort to make MAb E48 less antigenic for human application a chimeric human/mouse MAb (cMAb) has been constructed by use of recombinant DNA techniques. This modification strongly improved the capacity of MAb E48 for mediating antibody-dependent cellular cytotoxicity (ADCC). When using this cMAb E48 for RIT of minimal residual disease it can be anticipated that ADCC activity may be supportive to irradiation, especially in the ablation of single disseminated cells or small cell aggregates. Extrapolating results obtained in nude mice to patients and taking into account the good targeting in patients, RIT with E48 IgG seems to have potential for the elimination of minimal residual disease. Based on this encouraging progress, preparations are being made to evaluate the efficacy of Re-186-labelled cMAb E48 as an adjuvant in a phase III study for the treatment of patients who are at high risk for developing distant metastases.