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

Precipitation of I-CEA with MAbs VG-IgG2κ (■), VG-IgM (▲), and X4 (●) following incubation in a soluble phase assay

<p><b>Copyright information:</b></p><p>Taken from "Fully human IgG and IgM antibodies directed against the carcinoembryonic antigen (CEA) Gold 4 epitope and designed for radioimmunotherapy (RIT) of colorectal cancers"</p><p>BMC Cancer 2004;4():75-75.</p><p>Published online 15 Oct 2004</p><p>PMCID:PMC526287.</p><p>Copyright © 2004 Garambois et al; licensee BioMed Central Ltd.</p

Flow cytometry analysis of MAbs VG-IgG2κ, VG-IgM, and X4 reactivity against the CEA-expressing CO115-5F12 human colon carcinoma cell line (A) and NCA-expressing human granulocytes (B)

<p><b>Copyright information:</b></p><p>Taken from "Fully human IgG and IgM antibodies directed against the carcinoembryonic antigen (CEA) Gold 4 epitope and designed for radioimmunotherapy (RIT) of colorectal cancers"</p><p>BMC Cancer 2004;4():75-75.</p><p>Published online 15 Oct 2004</p><p>PMCID:PMC526287.</p><p>Copyright © 2004 Garambois et al; licensee BioMed Central Ltd.</p> 12A11 and 16B10 are two human anti-CEA MAbs that cross-react with NCA. 192 is a murine anti-CEA MAb that cross-reacts with NCA. Binding of the different primary antibodies was detected using either anti-human κ chain, anti-human μ chain, or anti-mouse γ chain as indicated

Biodistribution study of I-VG-IgG2κ (■) as compared with I-X4 (○) in LS174T tumor bearing nude mice dissected 24 and 72 h after i

<p><b>Copyright information:</b></p><p>Taken from "Fully human IgG and IgM antibodies directed against the carcinoembryonic antigen (CEA) Gold 4 epitope and designed for radioimmunotherapy (RIT) of colorectal cancers"</p><p>BMC Cancer 2004;4():75-75.</p><p>Published online 15 Oct 2004</p><p>PMCID:PMC526287.</p><p>Copyright © 2004 Garambois et al; licensee BioMed Central Ltd.</p>v. co-injection. The tissues shown are (from left to right) tumor, liver, kidneys, lung, spleen, heart, muscle, bone, skin, stomach, low bowel, colon, carcass and blood. Results are expressed in terms of %ID/g ± SD

Potentiation of radiation-induced growth inhibition by letrozole measured by cell-count assay

<p><b>Copyright information:</b></p><p>Taken from "Letrozole sensitizes breast cancer cells to ionizing radiation"</p><p>Breast Cancer Research 2004;7(1):R156-R163.</p><p>Published online 7 Dec 2004</p><p>PMCID:PMC1064115.</p><p>Copyright © 2004 Azria et al., licensee BioMed Central Ltd.</p> Growth of MCF-7CA cells, measured for 18 days after treatment, was inhibited to a 76% greater extent with letrozole plus 4 Gy radiation after 12 days, and to an 85% greater extent after 18 days, compared with radiation alone. Solid lines, ■ and ◆ represent radiation alone at 2 Gy and 4 Gy, respectively; dotted lines, ■ and ◆ represent combination of radiation plus letrozole (0.7 μM) at 2 Gy and 4 Gy, respectively

Potentiation of radiation-induced growth inhibition by letrozole measured by the MTT assay

<p><b>Copyright information:</b></p><p>Taken from "Letrozole sensitizes breast cancer cells to ionizing radiation"</p><p>Breast Cancer Research 2004;7(1):R156-R163.</p><p>Published online 7 Dec 2004</p><p>PMCID:PMC1064115.</p><p>Copyright © 2004 Azria et al., licensee BioMed Central Ltd.</p> Growth of MCF-7CA cells, measured 6 days after treatment, was inhibited to a 40% greater extent with letrozole plus 2 Gy radiation, and to a 76% greater extent with letrozole plus 4 Gy radiation, compared with radiation alone

Potentiation of radiation-induced growth inhibition by letrozole measured by clonogenic assay

<p><b>Copyright information:</b></p><p>Taken from "Letrozole sensitizes breast cancer cells to ionizing radiation"</p><p>Breast Cancer Research 2004;7(1):R156-R163.</p><p>Published online 7 Dec 2004</p><p>PMCID:PMC1064115.</p><p>Copyright © 2004 Azria et al., licensee BioMed Central Ltd.</p> With radiation alone the MCF-7CA cell survival fraction decreased in a dose-dependent manner, which was significantly potentiated by the addition of 0.7 μM letrozole. For 2 Gy radiation, the surviving fraction was 0.66 with radiation alone and was 0.46 with the addition of letrozole (= 0.02). For 3 Gy radiation, the corresponding surviving fractions were 0.4 and 0.18, respectively (= 0.02)

A recycling anti-transferrin receptor-1 monoclonal antibody as an efficient therapy for erythroleukemia through target up-regulation and antibody-dependent cytotoxic effector functions

International audienceTargeting transferrin receptor 1 (TfR1) with monoclonal antibodies is a promising therapeutic strategy in cancer as tumor cells often overexpress TfR1 and show increased iron needs. We have re-engineered six anti-human TfR1 single-chain variable fragment (scFv) antibodies into fully human scFv2-Fcγ1 and IgG1 antibodies. We selected the more promising candidate (H7), based on its ability to inhibit TfR1-mediated iron-loaded transferrin internalization in Raji cells (B-cell lymphoma). The H7 antibody displayed nanomolar affinity for its target in both formats (scFv2-Fcγ1 and IgG1), but cross-reacted with mouse TfR1 only in the scFv2-Fc format. H7 reduced the intracellular labile iron pool and, contrary to what has been observed with previously described anti-TfR1 antibodies, upregulated TfR1 level in Raji cells. H7 scFv2-Fc format elimination half-life was similar in FcRn knock-out and wild type mice, suggesting that TfR1 recycling contributes to prevent H7 elimination in vivo. In vitro, H7 inhibited the growth of erythroleukemia and B-cell lymphoma cell lines (IC50 0.1 µg/mL) and induced their apoptosis. Moreover, the Im9 B-cell lymphoma cell line, which is resistant to apoptosis induced by rituximab (anti-CD20 antibody), was sensitive to H7. In vivo, tumor regression was observed in nude mice bearing ERY-1 erythroleukemia cell xenografts treated with H7 through a mechanism that involved iron deprivation and antibody-dependent cytotoxic effector functions. Therefore, targeting TfR1 using the fully human anti-TfR1 H7 is a promising tool for the treatment of leukemia and lymphoma