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Cetuximab PET delineated changes in cellular distribution of EGFR upon dasatinib treatment in triple negative breast cancer.
ABSTRACT: BACKGROUND:At least 50% of triple negative breast cancer (TNBC) overexpress the epidermal growth factor receptor, EGFR, which paved the way for clinical trials investigating its blockade. Outcomes remained dismal stemming from mechanisms of resistance particularly the nuclear cycling of EGFR, which is enhanced by Src activation. Attenuation of Src reversed nuclear translocation, restoring EGFR to the cell surface. Herein, we hypothesize that changes in cellular distribution of EGFR upon Src inhibition with dasatinib can be annotated through the EGFR immunopositron emission tomography (immunoPET) radiotracer, [89Zr]Zr-cetuximab. METHODS:Nuclear and non-nuclear EGFR levels of dasatinib-treated vs. untreated MDA-MB-231 and MDA-MB-468 cells were analyzed via immunoblots. Both treated and untreated cells were exposed to [89Zr]Zr-cetuximab to assess binding at 4?°C and 37?°C. EGFR-positive MDA-MB-231, MDA-MB-468, and a patient-derived xenograft were treated with dasatinib or vehicle followed by cetuximab PET imaging to compare EGFR levels. After imaging, the treated mice were separated into two groups: one cohort continued with dasatinib with the addition of cetuximab while the other cohort received dasatinib alone. Correlations between the radiotracer uptake vs. changes in tumor growth and EGFR expression from immunoblots were analyzed. RESULTS:Treated cells displayed higher binding of [89Zr]Zr-cetuximab to the cell membrane at 4?°C and with greater internalized activity at 37?°C vs. untreated cells. In all tumor models, higher accumulation of the radiotracer in dasatinib-treated groups was observed compared to untreated tumors. Treated tumors displayed significantly decreased pSrc (Y416) with retained total Src levels compared to control. In MDA-MB-468 and PDX tumors, the analysis of cetuximab PET vs. changes in tumor volume showed an inverse relationship where high tracer uptake in the tumor demonstrated minimal tumor volume progression. Furthermore, combined cetuximab and dasatinib treatment showed better tumor regression compared to control and dasatinib-only-treated groups. No benefit was achieved in MDA-MB-231 xenografts with the addition of cetuximab, likely due to its KRAS-mutated status. CONCLUSIONS:Cetuximab PET can monitor effects of dasatinib on EGFR cellular distribution and potentially inform treatment response in wild-type KRAS TNBC.
Project description:PURPOSE:One-third of patients with RAS wild-type mCRC do not benefit from anti-EGFR monoclonal antibodies. This might be a result of variable pharmacokinetics and insufficient tumor targeting. We evaluated cetuximab tumor accumulation on [89Zr]Zr-cetuximab PET/CT as a potential predictive biomarker and determinant for an escalating dosing strategy. PATIENTS AND METHODS:PET/CT imaging of [89Zr]Zr-cetuximab (37 MBq/10 mg) after a therapeutic pre-dose (500 mg/m2 ? 2 h) cetuximab was performed at the start of treatment. Patients without visual tumor uptake underwent dose escalation and a subsequent [89Zr]Zr-cetuximab PET/CT. Treatment benefit was defined as stable disease or response on CT scan evaluation after 8 weeks. RESULTS:Visual tumor uptake on [89Zr]Zr-cetuximab PET/CT was observed in 66% of 35 patients. There was no relationship between PET positivity and treatment benefit (52% versus 80% for PET-negative, P = 0.16), progression-free survival (3.6 versus 5.7 months, P = 0.15), or overall survival (7.1 versus 9.4 months, P = 0.29). However, in 67% of PET-negative patients, cetuximab dose escalation (750-1250 mg/m2) was applied, potentially influencing outcome in this group. None of the second [89Zr]Zr-cetuximab PET/CT was positive. Eighty percent of patients without visual tumor uptake had treatment benefit, making [89Zr]Zr-cetuximab PET/CT unsuitable as a predictive biomarker. Tumor SUVpeak did not correlate to changes in tumor size on CT (P = 0.23), treatment benefit, nor progression-free survival. Cetuximab pharmacokinetics were not related to treatment benefit. BRAF mutations, right-sidedness, and low sEGFR were correlated with intrinsic resistance to cetuximab. CONCLUSION:Tumor uptake on [89Zr]Zr-cetuximab PET/CT failed to predict treatment benefit in patients with RAS wild-type mCRC receiving cetuximab monotherapy. BRAF mutations, right-sidedness, and low sEGFR correlated with intrinsic resistance to cetuximab.
Project description:Many solid tumors, including breast cancer, show increased activation of several growth factor receptors, specifically epidermal growth factor receptor (EGFR) and its family members as well as c-Src, a nonreceptor tyrosine kinase that promotes proliferation, inhibits apoptosis, and induces metastasis. We hypothesize that inhibition of c-Src and EGFRs will be an effective therapeutic strategy for triple-negative breast cancer. To test our hypothesis, we used a c-Src-specific inhibitor dasatinib (BMS-354825; Bristol-Myers Squibb) and our newly developed ErbB-inhibitory protein (EBIP), a potential pan-ErbB inhibitor, in breast cancer cells. EBIP is composed of 1 to 448 amino acids of the ectodomain of human EGFR to which the 30-amino acid epitope (known as "U" region) of rat EGFR-related protein is fused at the COOH-terminal end. The combination of dasatinib and EBIP was found to be highly effective in inhibiting the growth of four different breast cancer cells (MDA-MB-468, SKBr-3, MDA-MB-453, and MDA-MB-231) that express different levels of EGFRs. In EGFR-overexpressing MDA-MB-468 cells, the combination, but not monotherapy, markedly stimulated apoptosis mediated by caspase-9 and caspase-8 and attenuated activation of EGFR and Src as well as tyrosine kinase activity. EBIP also inhibited heregulin-induced activation of HER-2 and HER-3 in MDA-MB-453 breast cancer cells. The combination therapy was highly effective in suppressing tumor growth ( approximately 90% inhibition) in MDA-MB-468-derived xenografts in severe combined immunodeficient mice. The latter could be attributed to induction of apoptosis. We conclude that combining dasatinib and EBIP could be an effective therapeutic strategy for breast cancer by targeting EGFRs and Src signaling.
Project description:BACKGROUND: Cetuximab is often combined with radiotherapy in advanced SCCHN. Alternative routes bypassing inhibition of EGFR with cetuximab may overshadow the efficacy of this combination. We undertook this study to investigate a possible role of dasatinib in this scenario. METHODS: The SCC5, SCC25, SCC29, FaDu and A431 cell lines were assessed in vitro for cell proliferation under cetuximab and dasatinib treatments. In FaDu and A431 cells, dasatinib plus cetuximab resulted in higher proliferation than cetuximab alone. Then, FaDu and A431 cells were implanted into subcutaneous tissue of athymic mice that were irradiated with 30?Gy in 10 fractions over 2 weeks, and treated with cetuximab and dasatinib. Tumour growth, DNA synthesis and angiogenesis were determined. The EGFR, RAS-GTP activity, phosphorylated AKT, ERK1/2, SRC protein levels and VEGF secretion were determined in vitro. RESULTS: The addition of dasatinib to cetuximab and radiotherapy increased tumour growth, DNA synthesis and angiogenesis that were associated with RAS, AKT and ERK1/2 activation, and SRC inhibition in FaDu and A431 cells. CONCLUSIONS: In xenografts derived from these two cell lines, dasatinib did not improve the efficacy of cetuximab combined with radiotherapy. On the contrary, it worsened tumour control achieved by the combination of these two treatments.
Project description:Monoclonal antibodies (mAbs) against the epidermal growth factor receptor (EGFR) are used in the treatment of advanced colorectal cancer (mCRC). Approximately 50% of patients benefit despite patient selection for RAS wild type (wt) tumors. Based on the hypothesis that tumor targeting is required for clinical benefit of anti-EGFR treatment, biodistribution and tumor uptake of (89)Zr-cetuximab by Positron Emission Tomography (PET), combining the sensitivity of PET with the specificity of cetuximab for EGFR was evaluated. Ten patients with wt K-RAS mCRC received 37 ± 1 MBq (89)Zr-cetuximab directly (<2 h) after the first therapeutic dose of cetuximab. PET-scans were performed from 1 hour to 10 days post injection (p.i.). Biodistribution was determined for blood and organs. Uptake in tumor lesions was quantified by Standardized Uptake Value (SUV) and related to response. In 6 of 10 patients (89)Zr-cetuximab uptake in tumor lesions was detected. Four of 6 patients with (89)Zr-cetuximab uptake had clinical benefit, while progressive disease was observed in 3 of 4 patients without (89)Zr-cetuximab uptake. Taken together, tumor uptake of 89Zr-cetuximab can be visualized by PET imaging. The strong relation between uptake and response warrants further clinical validation as an innovative selection method for cetuximab treatment in patients with wt RAS mCRC.
Project description:Combined inhibition of epidermal growth factor receptor (EGFR) and Src family kinases (SFK) may lead to improved therapeutic effects. We evaluated the combination of dasatinib, an inhibitor of SFK and other kinases, and cetuximab, an anti-EGFR monoclonal antibody.Patients with advanced solid malignancies received cetuximab intravenously on a standard weekly schedule and dasatinib orally, once daily at 3 dose levels: (1) 100 mg, (2) 150 mg, (3) 200 mg. Pharmacokinetic and pharmacodynamic studies of dasatinib were performed prior to starting cetuximab and following 14 days of treatment.Twenty-five patients (3 dose level 1; 19 dose level 2; 3 dose level 3) were initially treated. Three patients developed dose-limiting toxicities: 1 at dose level 2 (headache) and 2 at dose level 3 (headache, nausea). Grade 3-4 toxicities in more than 2 patients included: dyspnea (4), vomiting (4), nausea (3), hypersensitivity reactions (3), headache (3) and anemia (3). Twenty-one patients developed headache (8 grade 1; 10 grade 2), which occurred after the loading of cetuximab and lasted 1-3 days. Six additional patients were treated with dasatinib starting 3 days after the loading dose of cetuximab; none developed headache after dasatinib. Dasatinib pharmacokinetics and a transient decrease in SFK PY416 levels in peripheral blood mononuclear cells were not altered by cetuximab. Patients with higher plasma TGF-alpha levels had worse progression-free survival.Dasatinib 150 mg once daily plus weekly cetuximab is recommended for phase II studies. Early-onset headache was ameliorated by starting dasatinib after cetuximab.
Project description:PURPOSE:Currently, the most commonly used chelator for labelling antibodies with 89Zr for immunoPET is desferrioxamine B (DFO). However, preclinical studies have shown that the limited in vivo stability of the 89Zr-DFO complex results in release of 89Zr, which accumulates in mineral bone. Here we report a novel chelator DFOcyclo*, a preorganized extended DFO derivative that enables octacoordination of the 89Zr radiometal. The aim was to compare the in vitro and in vivo stability of [89Zr]Zr-DFOcyclo*, [89Zr]Zr-DFO* and [89Zr]Zr-DFO. METHODS:The stability of 89Zr-labelled chelators alone and after conjugation to trastuzumab was evaluated in human plasma and PBS, and in the presence of excess EDTA or DFO. The immunoreactive fraction, IC50, and internalization rate of the conjugates were evaluated using HER2-expressing SKOV-3 cells. The in vivo distribution was investigated in mice with subcutaneous HER2+ SKOV-3 or HER2- MDA-MB-231 xenografts by PET/CT imaging and quantitative ex vivo tissue analyses 7 days after injection. RESULTS:89Zr-labelled DFO, DFO* and DFOcyclo* were stable in human plasma for up to 7 days. In competition with EDTA, DFO* and DFOcyclo* showed higher stability than DFO. In competition with excess DFO, DFOcyclo*-trastuzumab was significantly more stable than the corresponding DFO and DFO* conjugates (p < 0.001). Cell binding and internalization were similar for the three conjugates. In in vivo studies, HER2+ SKOV-3 tumour-bearing mice showed significantly lower bone uptake (p < 0.001) 168 h after injection with [89Zr]Zr-DFOcyclo*-trastuzumab (femur 1.5 ± 0.3%ID/g, knee 2.1 ± 0.4%ID/g) or [89Zr]Zr-DFO*-trastuzumab (femur 2.0 ± 0.3%ID/g, knee 2.68 ± 0.4%ID/g) than after injection with [89Zr]Zr-DFO-trastuzumab (femur 4.5 ± 0.6%ID/g, knee 7.8 ± 0.6%ID/g). Blood levels, tumour uptake and uptake in other organs were not significantly different at 168 h after injection. HER2- MDA-MB-231 tumour-bearing mice showed significantly lower tumour uptake (p < 0.001) after injection with [89Zr]Zr-DFOcyclo*-trastuzumab (16.2 ± 10.1%ID/g) and [89Zr]Zr-DFO-trastuzumab (19.6 ± 3.2%ID/g) than HER2+ SKOV-3 tumour-bearing mice (72.1 ± 14.6%ID/g and 93.1 ± 20.9%ID/g, respectively), while bone uptake was similar. CONCLUSION:89Zr-labelled DFOcyclo* and DFOcyclo*-trastuzumab showed higher in vitro and in vivo stability than the current commonly used 89Zr-DFO-trastuzumab. DFOcyclo* is a promising candidate to become the new clinically used standard chelator for 89Zr immunoPET.
Project description:BACKGROUND:De novo or acquired resistance in breast cancer leads to treatment failures and disease progression. In human epidermal growth factor receptor 2 (HER2)-positive (HER2+) breast cancer, Src, a non-receptor tyrosine kinase, is identified as a major mechanism of trastuzumab resistance, with its activation stabilizing aberrant HER2 signaling, thus making it an attractive target for inhibition. Here, we explored the causal relationship between Src and HER2 by examining the potential of 89Zr-trastuzumab as a surrogate imaging marker of Src activity upon inhibition with dasatinib in HER2+ breast cancer. METHODS:HER2+ primary breast cancer cell lines BT-474 and trastuzumab-resistant JIMT-1 were treated with dasatinib and assessed for expression and localization of HER2, Src, and phosphorylated Src (pSrc) (Y416) through western blots and binding assays. Mice bearing BT-474 or JIMT-1 tumors were treated for 7 or 14 days with dasatinib. At the end of each treatment, tumors were imaged with 89Zr-trastuzumab. The results of 89Zr-trastuzumab positron emission tomography (PET) was compared against tumor uptake of fluorodeoxyglucose (18F-FDG) obtained the day before in the same group of mice. Ex vivo western blots and immunohistochemical staining (IHC) were performed for validation. RESULTS:In BT-474 and JIMT-1 cells, treatment with dasatinib resulted in a decrease in internalized 89Zr-trastuzumab. Confirmation with immunoblots displayed abrogation of pSrc (Y416) signaling; binding assays in both cell lines demonstrated a decrease in cell surface and internalized HER2-bound tracer. In xenograft models, dasatinib treatment for 7 days (BT-474, 11.05?±?2.10 % injected dose per gram of tissue %(ID)/g; JIMT-1, 3.88?±?1.47 %ID/g)) or 14 days (BT-474, 9.20?±?1.85 %ID/g; JIMT-1, 4.45?±?1.23 %ID/g) resulted in a significant decrease in 89Zr-trastuzumab uptake on PET compared to untreated control (BT-474, 17.88?±?2.18 %ID/g; JIMT-1, 8.04?±?1.47 %ID/g). No difference in 18F-FDG uptake was observed between control and treated cohorts. A parallel decrease in membranous HER2 and pSrc (Y416) staining was observed in tumors post treatment on IHC. Immunoblots further validated the 89Zr-trastuzumab-PET readout. Positive correlation was established between 89Zr-trastuzumab tumor uptake versus tumor regression, pSrc and pHER2 expression. CONCLUSIONS:89Zr-trastuzumab can potentially assess tumor response to dasatinib in HER2+ breast cancer and could be used as a surrogate tool to monitor early changes in Src signaling downstream of HER2.
Project description:While radiolabelled antibodies have found great utility as PET and SPECT imaging agents in oncological investigations, a notable shortcoming of these agents is their propensity to accumulate non-specifically within tumour tissue. The degree of this non-specific contribution to overall tumour uptake is highly variable and can ultimately lead to false conclusions. Therefore, in an effort to obtain a reliable measure of inter-individual differences in non-specific tumour uptake of radiolabelled antibodies, we demonstrate that the use of dual-isotope imaging overcomes this issue, enables true quantification of epitope expression levels, and allows non-invasive in vivo immunohistochemistry. The approach involves co-administration of (i) an antigen-targeting antibody labelled with zirconium-89 (89Zr), and (ii) an isotype-matched non-specific control IgG antibody labelled with indium-111 (111In). As an example, the anti-HER2 antibody trastuzumab was radiolabelled with 89Zr, and co-administered intravenously together with its 111In-labelled non-specific counterpart to mice bearing human breast cancer xenografts with differing HER2 expression levels (MDA-MB-468 [HER2-negative], MDA-MB-231 [low-HER2], MDA-MB-231/H2N [medium-HER2], and SKBR3 [high-HER2]). Simultaneous PET/SPECT imaging using a MILabs Vector4 small animal scanner revealed stark differences in the intratumoural distribution of [89Zr]Zr-trastuzumab and [111In]In-IgG, highlighting regions of HER2-mediated uptake and non-specific uptake, respectively. Normalisation of the tumour uptake values and tumour-to-blood ratios obtained with [89Zr]Zr-trastuzumab against those obtained with [111In]In-IgG yielded values which were most strongly correlated (R?=?0.94; P?=?0.02) with HER2 expression levels for each breast cancer type determined by Western blot and in vitro saturation binding assays, but not non-normalised uptake values. Normalised intratumoural distribution of [89Zr]Zr-trastuzumab correlated well with intratumoural heterogeneity HER2 expression.
Project description:In pre-clinical studies, triple-negative breast cancer (TNBC) cells have demonstrated sensitivity to the multi-targeted kinase inhibitor dasatinib; however, clinical trials with single-agent dasatinib showed limited efficacy in unselected populations of breast cancer, including TNBC. To study potential mechanisms of resistance to dasatinib in TNBC, we established a cell line model of acquired dasatinib resistance (231-DasB). Following an approximately three-month exposure to incrementally increasing concentrations of dasatinib (200 nM to 500 nM) dasatinib, 231-DasB cells were resistant to the agent with a dasatinib IC50 value greater than 5 ?M compared to 0.04 ± 0.001 µM in the parental MDA-MB-231 cells. 231-DasB cells also showed resistance (2.2-fold) to the Src kinase inhibitor PD180970. Treatment of 231-DasB cells with dasatinib did not inhibit phosphorylation of Src kinase. The 231-DasB cells also had significantly increased levels of p-Met compared to the parental MDA-MB-231 cells, as measured by luminex, and resistant cells demonstrated a significant increase in sensitivity to the c-Met inhibitor, CpdA, with an IC50 value of 1.4 ± 0.5 µM compared to an IC50 of 6.8 ± 0.2 µM in the parental MDA-MB-231 cells. Treatment with CpdA decreased p-Met and p-Src in both 231-DasB and MDA-MB-231 cells. Combined treatment with dasatinib and CpdA significantly inhibited the growth of MDA-MB-231 parental cells and prevented the emergence of dasatinib resistance. If these in vitro findings can be extrapolated to human cancer treatment, combined treatment with dasatinib and a c-Met inhibitor may block the development of acquired resistance and improve response rates to dasatinib treatment in TNBC.
Project description:Epidermal growth factor receptor - tyrosine kinase inhibitor (EGFR-TKI) is the first choice of treatment for advanced non-small cell lung cancer (NSCLC) patients harbouring activating EGFR mutations. However, single agent usually has limited efficacy due to heterogeneous resistant mechanisms of cancer cells. Thus drug combination therapy would offer more benefits by synergistic interactions and avoidance of resistance emergence. In this study, we selected 8 NSCLC cell lines with different genetic characteristics as research models to investigate the efficacy of 4 agents (gefitinib, cetuximab, afatinib and dasatinib) and their combinations. As a single agent, both afatinib and dasatinib showed more inhibition against cell proliferation than gefitinib and cetuximab. Afatinib combined with dasatinib demonstrated significantly high efficacy against 7 gefitinib-resistant NSCLC cell lines. Moreover, it reversed the resistance to the 4 studied single agents in PTEN mutated NSCLC cells. By studying the activity of EGFR, Src and their downstream signalling pathways including PI3K/PTEN/Akt, Ras/Raf/MEK/ERK, Src/FAK and JAK/Stat, we demonstrated the synergistic interaction between afatinib and dasatinib was not only due to their blockage of different signalling pathways but also the complemental inhibition of the related signalling molecules such as Stat3. We also found that the level of Src, Stat3, and MAPK may be useful biomarkers predicating synergism between afatinib and dasatinib for the treatment of gefitinib-resistant NSCLC cells.