Radiosensitisation of U87MG brain tumours by anti-epidermal growth factor receptor monoclonal antibodies

Abstract

As epidermal growth factor receptor (EGFR) has been reported to be a radiation response modulator, HER inhibitors are regarded to act as potential radiosensitisers. Our study examined the role of nimotuzumab and cetuximab both, the two monoclonal antibodies (mAbs) to EGFR, as radiosensitisers in a murine glioma model in vivo. Co-administration of both the antibodies with radiation increased the radiosensitivity of U87MG, resulting in a significant delay of subcutaneous (s.c.) tumour growth. Furthermore, the addition of antibodies to the radiation decreased brain tumour sizes and is inhibited by 40 -80% the increased tumour cell invasion provoked by radiotherapy, although promoted tumour cell apoptosis. Whereas nimotuzumab led to a reduction in the size of tumour blood vessels and proliferating cells in s.c. tumours, cetuximab had no significant antiangiogenic nor antiproliferative activity. In contrast, cetuximab induced a more marked inhibition of EGFR downstream signalling compared with nimotuzumab. Moreover, both antibodies reduced the total number of radioresistant CD133 þ cancer stem cells (CSCs). These results were encouraging, and showed the superiority of combined treatment of mAbs to EGFR and radiation over each single therapy against glioblastoma multiforme (GBM), confirming the role of these drugs as radiosensitisers in human GBM. In addition, we first showed the ability of mAb specifics against EGFR to target radioresistant glioma CSC, supporting the potential use in patients.

Nimotuzumab, a novel monoclonal antibody to the epidermal growth factor receptor, in the treatment of non-small cell lung cancer

“…28 Consistent with our results, coadministration of nimotuzumab increased the radiosensitivity of subcutaneous U87MG tumors, resulting in a significant delay in tumor growth. Furthermore, the addition of nimotuzumab to radiation reduced the size of tumors formed by U87MG cells in the brain to a greater extent than did radiation alone, and it inhibited by 40%-80% the increased tumor cell invasion provoked by radiotherapy as well as promoted tumor cell apoptosis.…”

Preclinical Efficacy of Nimotuzumab, an Anti-Egfr Monoclonal Antibody as a Single Agent Therapy in Human GBM u87mg Xenografts

“…Temozolomide was purchased from Schering-Plough (stock solution 150 mmol/L in DMSO). The humanized anti-EGFR mAb nimotuzumab was generated at the Center of Molecular Immunology [11,12]. All the primary and secondary antibodies were purchased from commercial sources as listed: rabbit polyclonal EGFR antibody to total EGFR (Santa Cruz Biotechnology), mouse monoclonal antibody MIB-1 to Ki-67 (DakoCytomation), rat monoclonal anti CD31/ PECAM-1 antibody (BD Pharmingen), mouse monoclonal antibody to CD133/1 (AC133) (Miltenyi Biotec).…”

“…For immunohistochemistry, tissue sections (thickness of 8 µm) were immunostained according to standard protocols. To analyze the proliferative activity of the tumor cells, sections were stained with the MIB-1 antibody (1:50) against the Ki-67 as described previously [11]. The percentage of MIB-1-positive nuclei was determined by counting immunoreactive tumor cell nuclei in at least 5 high-power fields in the most actively proliferating tumor area.…”

“…Vessel density was determined by counting the number of stained vessels in three to five high-power fields (0.031 mm 2 ) in the most densely vascularized areas. To detect CD133 positive cells, tumor sections were stained with the anti-human CD133/1 (AC133) (1:10) as described [11]. To determine EGFR expression tumor sections were stained as described [11].…”

Nimotuzumab in combination with radiotherapy in high grade glioma patients

“…18 It has been suggested that brain tumor growth is dependent on the presence of a cancer stem cell niche, and, consequently, the ability to target cancer stem cells may represent an essential property of nimotuzumab. 18 The antibody has also been extensively evaluated in the clinical setting in patients bearing advanced head and neck, glioma, lung, esophageal, pancreatic, and gastric cancer, among others. 19,20 Nimotuzumab currently has marketing approval for the treatment of advanced head and neck, glioma, and esophageal cancer patients in combination with irradiation or chemo-radiotherapy.…”