Peptides in Receptor-Mediated Radiotherapy: From Design to the Clinical Application in Cancers

Short peptides can show high affinity for specific receptors overexpressed on tumor cells. Some of these are already used in cancerology as diagnostic tools and others are in clinical trials for therapeutic applications. Therefore, peptides exhibit great potential as a diagnostic tool but also as an alternative or an additional antitumoral approach upon the covalent attachment of a therapeutic moiety such as a radionuclide or a cytotoxic drug. The chemistry offers flexibility to graft onto the targeting-peptide either fluorine or iodine directly, or metallic radionuclides through appropriate chelating agent. Since short peptides are straightforward to synthesize, there is an opportunity to further improve existing peptides or to design new ones for clinical applications. However, several considerations have to be taken into account to optimize the recognition properties of the targeting-peptide to its receptor, to improve its stability in the biological fluids and its residence in the body, or to increase its overall therapeutic effect. In this review, we highlight the different aspects which need to be considered for the development of an efficient peptide receptor-mediated radionuclide therapy in different neoplasms

Redirecting NK cells mediated tumor cell lysis by a new recombinant bifunctional protein

Natural killer (NK) cells are at the crossroad between innate and adaptive immunity and play a major role in cancer immunosurveillance. NK cell stimulation depends on a balance between inhibitory and activating receptors, such as the stimulatory lectin-like receptor NKG2D. To redirect NK cells against tumor cells, we designed bifunctional proteins able to specifically bind tumor cells and to induce their lysis by NK cells, after NKG2D engagement. To this aim, we used the ‘knob into hole' heterodimerization strategy, in which ‘knob' and ‘hole' variants were generated by directed mutagenesis within the CH3 domain of human IgG1 Fc fragments fused to an anti-CEA or anti-HER2 scFv or to the H60 murine ligand of NKG2D, respectively. We demonstrated the capacity of the bifunctional proteins produced to specifically coat tumor cells surface with H60 ligand. Most importantly, we demonstrated that these bifunctional proteins were able to induce an NKG2D-dependent and antibody-specific tumor cell lysis by murine NK cells. Overall, the results show the possibility to redirect NK cytotoxicity to tumor cells by a new format of recombinant bispecific antibody, opening the way of potential NK cell-based cancer immunotherapies by specific activation of the NKG2D receptor at the tumor sit

A Polymerase-chain-reaction Assay for the Specific Identification of Transcripts Encoded by Individual Carcinoembryonic Antigen (CEA)-gene-family Members

Carcinoembryonic antigen (CEA) is a tumor marker that belongs to a family of closely related molecules with variable expression patterns. We have developed sets of oligonucleotide primers for the specific amplification of transcripts from individual CEA-family members using the reverse transcriptase/ polymerase chain reaction (RT/PCR). Specific primer sets were designed for CEA, non-specific cross-reacting antigen (NCA), biliary glycoprotein (BGP), carcinoembryonic antigen gene-family members 1, 6 and 7 (CGMI, CGM6 and CGM7), and one set for all pregnancy-specific glycoprotein (PSG) transcripts. Primers were first tested for their specificity against individual cDNA clones and product-hybridization with internal, transcript-specific oligonucleotides. Total RNA from 12 brain and 63 gynecological tumors were then tested for expression of CEA-related transcripts. None were found in tumors located in the brain, including various mesenchymal and neuro-epithelial tumors. CEA and NCA transcripts were, however, present in an adenocarcinoma located in the nasal sinuses. In ovarian mucinous adenocarcinomas, we always found co-expression of CEA and NCA transcripts, and occasionally BGP mRNA. CEA-related transcripts were also found in some serous, endometrioid and clear-cell ovarian carcinomas. CEA, NCA and BGP transcripts were present in endometrial carcinomas of the uterus and cervical carcinomas, whereas uterine leiomyomas were completely negative. No transcripts were found from CGM 1, CGM6, CGM7 or from PSG genes in any of the tumors tested. The PCR data were compared with immunohistochemical investigations of ovarian tumors at the protein level using CEA (26/3/13)-, NCA-50/90 (9A6FR) and NCA-95 (80H3)-specific monoclonal antibodies

Combined cetuximab and trastuzumab are superior to gemcitabine in the treatment of human pancreatic carcinoma xenografts

Background: Pancreatic carcinoma remains a treatment-refractory cancer with a poor prognosis. Here, we compared anti-epidermal growth factor receptor (EGFR) and anti-HER2 monoclonal antibodies (2mAbs) injections with standard gemcitabine treatment on human pancreatic carcinoma xenografts. Materials and methods: Nude mice, bearing human pancreatic carcinoma xenografts, were treated with either combined anti-EGFR (cetuximab) and anti-HER2 (trastuzumab) or gemcitabine, and tumor growth was observed. Results and conclusion: In first-line therapy, mice survival was significantly longer in the 2mAbs group compared with gemcitabine (P < 0.0001 for BxPC-3, P = 0.0679 for MiaPaCa-2 and P = 0.0019 for Capan-1) and with controls (P < 0.0001). In second-line therapy, tumor regressions were observed after replacing gemcitabine by 2mAbs treatment, resulting in significantly longer animal survival compared with mice receiving continuous gemcitabine injections (P = 0.008 for BxPC-3, P = 0.05 for MiaPaCa-2 and P < 0.001 for Capan-1). Therapeutic benefit of 2mAbs was observed despite K-Ras mutation. Interestingly, concerning the mechanism of action, coinjection of F(ab′)2 fragments from 2mAbs induced significant tumor growth inhibition, compared with controls (P = 0.001), indicating that the 2mAbs had an Fc fragment-independent direct action on tumor cells. This preclinical study demonstrated a significant improvement of survival and tumor regression in mice treated with anti-EGFR/anti-HER2 2mAbs in first- and second-line treatments, compared with gemcitabine, independently of the K-Ras statu

HER3 as biomarker and therapeutic target in pancreatic cancer: new insights in pertuzumab therapy in preclinical models.

International audienceThe anti-HER2 antibody pertuzumab inhibits HER2 dimerization and affects HER2/HER3 dimer formation and signaling. As HER3 and its ligand neuregulin are implicated in pancreatic tumorigenesis, we investigated whether HER3 expression could be a predictive biomarker of pertuzumab efficacy in HER2low-expressing pancreatic cancer. We correlated in vitro and in vivo HER3 expression and neuregulin dependency with the inhibitory effect of pertuzumab on cell viability and tumor progression. HER3 knockdown in BxPC-3 cells led to resistance to pertuzumab therapy. Pertuzumab treatment of HER3-expressing pancreatic cancer cells increased HER3 at the cell membrane, whereas the anti-HER3 monoclonal antibody 9F7-F11 down-regulated it. Both antibodies blocked HER3 and AKT phosphorylation and inhibited HER2/HER3 heterodimerization but affected differently HER2 and HER3 homodimers. The pertuzumab/9F7-F11 combination enhanced tumor inhibition and the median survival time in mice xenografted with HER3-expressing pancreatic cancer cells. Finally, HER2 and HER3 were co-expressed in 11% and HER3 alone in 27% of the 45 pancreatic ductal adenocarcinomas analyzed by immunohistochemistry. HER3 is essential for pertuzumab efficacy in HER2low-expressing pancreatic cancer and HER3 expression might be a predictive biomarker of pertuzumab efficacy in such cancers. Further studies in clinical samples are required to confirm these findings and the interest of combining anti-HER2 and anti-HER3 therapeutic antibodies

Direct comparison of a radioiodinated intact chimeric anti-CEA MAb with its F(ab')2 fragment in nude mice bearing different human colon cancer xenografts.

Tumour localisation and tumour to normal tissue ratios of a chimeric anti-carcinoembryonic antigen (CEA) monoclonal antibody (MAb), in intact form and as an F(ab')2 fragment labelled with 125I and 131I, were compared in groups of nude mice bearing four different colon cancer xenografts, T380, Co112 or LoVo, of human origin, or a rat colon cancer transfected with human CEA cDNA, called '3G7'. For each tumour, three to four mice per time point were analysed 6, 12, 24, 48 and 96 h after MAb injection. In the different tumours, maximal localisation of intact MAb was obtained at 24 to 48 h, and of F(ab')2 fragment 12 to 24 h after injection. Among the different tumours, localisation was highest with colon cancer T380, with 64% of the injected dose per gram (% ID/g) for the intact MAb and 57% for its F(ab')2 fragment, while in the three other tumours, maximal localisation ranged from 14 to 22% ID g-1 for the intact MAb and was about 11% for the F(ab')2. Tumour to normal tissue ratios of intact MAb increased rapidly until 24 h after injection and remained stable or showed only a minor increase thereafter. In contrast, for the F(ab')2 fragment, the tumour to normal tissue ratios increased steadily up to 4 days after injection reaching markedly higher values than those obtained with intact MAb. For the four different xenografts, tumour to blood ratios of F(ab')2 were about 2, 3 and 5 to 16 times higher than those of intact antibodies at 12, 24 and 96 h after injection, respectively

Letrozole sensitizes breast cancer cells to ionizing radiation

INTRODUCTION: Radiotherapy (RT) is considered a standard treatment option after surgery for breast cancer. Letrozole, an aromatase inhibitor, is being evaluated in the adjuvant setting. We determined the effects of the combination of RT and letrozole in the aromatase-expressing breast tumour cell line MCF-7CA, stably transfected with the CYP19 gene. METHODS: Irradiations were performed using a cobalt-60 source with doses ranging from 0 to 4 Gy. Cells were incubated with androstenedione in the presence or absence of letrozole. Effects of treatment were evaluated using clonogenic assays, tetrazolium salt colorimetric (MTT) assays, and cell number determinations. Cell-cycle analyses were conducted using flow cytometry. RESULTS: The survival fraction at 2 Gy was 0.66 for RT alone and was 0.44 for RT plus letrozole (P = 0.02). Growth of MCF-7CA cells as measured by the cell number 6 days after radiotherapy (2 and 4 Gy) was decreased by 76% in those cells treated additionally with letrozole (0.7 μM) compared with those receiving radiotherapy alone (P = 0.009). Growth inhibition, assessed either by cell number (P = 0.009) or by the MTT assay (P = 0.02), was increased after 12 days of the combination treatment. Compared with radiation alone, the combination of radiation and letrozole produced a significant decrease in radiation-induced G(2 )phase arrest and a decrease of cells in the S phase, with cell redistribution in the G(1 )phase. CONCLUSIONS: These radiobiological results may form the basis for concurrent use of letrozole and radiation as postsurgical adjuvant therapy for breast cancer

Neutralization of KIT Oncogenic Signaling in Leukemia with Antibodies Targeting KIT Membrane Proximal Domain 5

KIT is a cell surface tyrosine kinase receptor whose ligand stem cell factor (SCF) triggers homodimerization and activation of downstream effector pathways involved in cell survival, proliferation, homing, or differentiation. KIT-activating mutations are major oncogenic drivers in subsets of acute myeloid leukemia (AML), in mast cell leukemia, and in gastrointestinal stromal tumors (GIST). The overexpression of SCF and/or wild-type (WT) KIT is also observed in a number of cancers, including 50% of AML and small cell lung cancer. The use of tyrosine kinase inhibitors (TKI) in these pathologies is, however, hampered by initial or acquired resistance following treatment. Using antibody phage display, we obtained two antibodies (2D1 and 3G1) specific for the most membrane proximal extracellular immunoglobulin domain (D5) of KIT, which is implicated in KIT homodimerization. Produced as single chain variable antibody fragments fused to the Fc fragment of a human IgG1, bivalent 2D1-Fc and 3G1-Fc inhibited KIT-dependent growth of leukemic cell lines expressing WT KIT (UT7/Epo) or constitutively active KIT mutants, including the TKI imatinib-resistant KIT D816V mutant (HMC1.2 cell line). In all models, either expressing WT KIT or mutated KIT, 2D1 and 3G1-Fc induced KIT internalization and sustained surface downregulation. However, interestingly, KIT degradation was only observed in leukemic cell lines with oncogenic KIT, a property likely to limit the toxicity of these antibodies in patients. These fully human antibody formats may represent therapeutic tools to target KIT signaling in leukemia or GIST, and to bypass TKI resistance of certain KIT mutants

Internalisation enhances photo-induced cytotoxicity of monoclonal antibody-phthalocyanine conjugates

Immunophototherapy of cancer combines the specificity of a monoclonal antibody (MAb) to an overexpressed tumor marker with the phototoxic properties of the conjugated dye. To analyze the potential role of internalisation of the dye on photo-induced cytotoxicity, we compared two target antigens, carcinoembryonic antigen (CEA) that does not internalise and ErbB2 that does. Human ovarian carcinoma SKOv3 cells that express a high level of ErbB2 were transfected with the CEA cDNA. Using FACS analysis, the resulting cell line, SKOv3-CEA-1B9, demonstrated comparable levels of expression of the two target antigens. Aluminium tetrasulfophthalocyanine (AlPcS 4) was covalently coupled to anti-CEA MAb 35A7, anti-ErbB2 MAb FSP77 and a non-specific MAb PX, via a five-carbon sulfonamide spacer chain (A 1) at molar ratios ranging from 6 to 9 moles of AlPcS 4 per mole of MAb. The 35A7-(AlPcS 4 A 1)8 conjugate induced 68% growth inhibition of the SKOv3-CEA-1B9 cell line after a 20 h incubation at 2.50 μg/ml (based on AlPcS 4 A 1 content) following light exposure. However, the FSP77-(AlPcS 4 A 1)6 conjugate gave a 51% growth inhibition for an AlPcS 4 A 1 concentration as low as 0.04 μg/ml after the same incubation time and exposure to the same light dose. At a 1.25 μg/ml AlPcS 4 A 1 concentration, the FSP77-(AlPcS 4 A 1)6 conjugate gave a 67% growth inhibition after an incubation time as short as 1 h, reaching a 96% inhibition after an 8 h incubation time. Using an unique cell line that expresses two different target antigens, we demonstrated a clear advantage of an internalising over a non-internalising MAb-dye conjugate in terms of phototoxic efficacy. In vivo evaluation of the photodynamic properties of the conjugates is in progress. © 2001 Cancer Research Campaign http://www.bjcancer.com © 2001 Cancer Research Campaig

Involvement of circulating CEA in liver metastases from colorectal cancers re-examined in a new experimental model

Both experimental and clinical data show evidence of a correlation between elevated blood levels of carcinoembryonic antigen (CEA) and the development of liver metastases from colorectal carcinomas. However, a cause-effect relationship between these two observations has not been demonstrated. For this reason, we developed a new experimental model to evaluate the possible role of circulating CEA in the facilitation of liver metastases. A CEA-negative subclone from the human colon carcinoma cell line CO115 was transfected either with CEA-cDNA truncated at its 3' end by the deletion of 78 base pairs leading to the synthesis of a secreted form of CEA or with a full-length CEA-cDNA leading to the synthesis of the entire CEA molecule linked to the cell surface by a GPI anchor. Transfectants were selected either for their high CEA secretion (clone CO115-2C2 secreting up to 13 microg CEA per 10(6) cells within 72 h) or for their high CEA membrane expression (clone CO115-5F12 expressing up to 1 x 10(6) CEA molecules per cell). When grafted subcutaneously, CO115-2C2 cells gave rise to circulating CEA levels that were directly related to the tumour volume (from 100 to 1000 ng ml(-1) for tumours ranging from 100 to 1000 mm3), whereas no circulating CEA was detectable in CO115 and CO115-5F12 tumour-bearing mice. Three series of nude mice bearing a subcutaneous xenograft from either clone CO115-2C2 or the CO115-5F12 transfectant, or an untransfected CO115 xenograft, were further challenged for induction of experimental liver metastases by intrasplenic injection of three different CEA-expressing human colorectal carcinoma cell lines (LoVo, LS174T or CO112). The number and size of the liver metastases were shown to be independent of the circulating CEA levels induced by the subcutaneous CEA secreting clone (CO115-2C2), but they were directly related to the metastatic properties of the intrasplenically injected tumour cells