Effect of cetuximab treatment in squamous cell carcinomas

Impact of synthesis methods on the functionality of antibody-conjugated gold nanoparticles for targeted therapy

Gold nanoparticles (GNPs) are emerging as promising modular platforms for antibody-based cancer therapeutics. Their unique physiochemical properties enable efficient binding of multiple antibodies upon a single particle, thereby enhancing therapeutic potential. However, the effect of widely used synthesis techniques on the characteristics and functionality of antibody-GNP platforms has yet to be fully understood. Here, we investigated the effect of key synthesis approaches, namely, covalent binding and physical adsorption, on the properties and anti-cancer functionality of antibody-coated GNPs. By carefully manipulating synthesis variables, including antibody mass in reaction and linker compositions, we revealed a direct impact of these synthesis methods on antibody binding efficiency and anti-cancer functionality. We found that covalent binding of antibodies to GNPs generated a platform with increased cancer cell killing functionality as compared to the adsorption approach. Additionally, a higher antibody mass in the synthesis reaction and a higher polyethylene glycol linker ratio upon covalently bound antibody-GNPs led to increased cell death. Our findings emphasize the critical role of synthesis strategies in determining the functionality of targeted GNPs for effective cancer therapy.

The CDK4/6 inhibitor LY2835219 has potent activity in combination with mTOR inhibitor in head and neck squamous cell carcinoma

Deletion of CDKN2A (p16) or amplification of CCND1 (cyclin D1) occurs commonly in head and neck squamous cell carcinoma (HNSCC) and induces sustained cyclin-dependent kinase (CDK) 4/6 activation. Here, we report the antiproliferative activity of LY2835219, a selective CDK4/6 inhibitor through inhibition of CDK4/6-dependent Ser780 phosphorylation in retinoblastoma (RB) and induction of cell cycle arrest in HNSCC cells. In addition, we demonstrated the antitumor effects of HNSCC xenografts to LY2835219 in vivo. Given the limited effect in HNSCC as a single-agent treatment with LY2835219, a combinational strategy is required to enhance antitumor activity. At the molecular level, we found that LY2835219 inhibited activation of AKT and ERK, but not mTOR. The combination of LY2835219 with mTOR inhibitor was found to be more effective than either drug alone in vitro and in vivo. Taken together, our findings suggest that a combinational treatment with LY2835219 and mTOR inhibitor is a promising therapeutic approach for HNSCC.

Novel Tumor Pretargeting System Based on Complementary l-Configured Oligonucleotides

Unnatural mirror image l-configured oligonucleotides (L-ONs) are a convenient substance class for the application as complementary in vivo recognition system between a tumor specific antibody and a smaller radiolabeled effector molecule in pretargeting approaches. The high hybridization velocity and defined melting conditions are excellent preconditions of the L-ON based methodology. Their high metabolic stability and negligible unspecific binding to endogenous targets are superior characteristics in comparison to their d-configured analogs. In this study, a radiopharmacological evaluation of a new l-ONs based pretargeting system using the epidermal growth factor receptor (EGFR) specific antibody cetuximab (C225) as target-seeking component is presented. An optimized PEGylated 17mer-L-DNA was conjugated with p-SCN-Bn-NOTA (NOTA') to permit radiolabeling with the radionuclide ⁶⁴Cu. C225 was modified with the complementary 17mer-L-DNA (c-L-DNA) strand as well as with NOTA' for radiolabeling and use for positron emission tomography (PET). Two C225 conjugates were coupled with 1.5 and 5.0 c-L-DNA molecules, respectively. In vitro characterization was done with respect to hybridization studies, competition and saturation binding assays in EGFR expressing squamous cell carcinoma cell lines A431 and FaDu. The modified C225 derivatives exhibited high binding affinities in the low nanomolar range to the EGFR. PET and biodistribution experiments on FaDu tumor bearing mice with directly ⁶⁴Cu-labeled NOTA'₃-C225-(c-L-DNA)_1.5 conjugate revealed that a pretargeting interval of 24 h might be a good compromise between tumor accumulation, internalization, blood background, and liver uptake of the antibody. Despite internalization of the antibody in vivo pretargeting experiments showed an adequate hybridization of ⁶⁴Cu-radiolabeled NOTA'-L-DNA to the tumor located antibody and a good tumor-to-muscle ratio of about 11 resulting in a clearly visible image of the tumor after 24 h up to 72 h. Furthermore, low accumulation of radioactivity in organs responsible for metabolism and excretion was determined. The presented results indicate a high potential of complementary L-ONs for the pretargeting approach which can also be applied to therapeutic radionuclides such as ¹⁷⁷Lu, ⁹⁰Y, ¹⁸⁶Re, or ¹⁸⁸Re.

The dual PI3K/mTOR inhibitor PKI-587 enhances sensitivity to cetuximab in EGFR-resistant human head and neck cancer models

BACKGROUND

Cetuximab is the only targeted agent approved for the treatment of head and neck squamous cell carcinomas (HNSCC), but low response rates and disease progression are frequently reported. As the phosphoinositide 3-kinase (PI3K) and the mammalian target of rapamycin (mTOR) pathways have an important role in the pathogenesis of HNSCC, we investigated their involvement in cetuximab resistance.

METHODS

Different human squamous cancer cell lines sensitive or resistant to cetuximab were tested for the dual PI3K/mTOR inhibitor PF-05212384 (PKI-587), alone and in combination, both in vitro and in vivo.

RESULTS

Treatment with PKI-587 enhances sensitivity to cetuximab in vitro, even in the condition of epidermal growth factor receptor (EGFR) resistance. The combination of the two drugs inhibits cells survival, impairs the activation of signalling pathways and induces apoptosis. Interestingly, although significant inhibition of proliferation is observed in all cell lines treated with PKI-587 in combination with cetuximab, activation of apoptosis is evident in sensitive but not in resistant cell lines, in which autophagy is pre-eminent. In nude mice xenografted with resistant Kyse30 cells, the combined treatment significantly reduces tumour growth and prolongs mice survival.

CONCLUSIONS

Phosphoinositide 3-kinase/mammalian target of rapamycin inhibition has an important role in the rescue of cetuximab resistance. Different mechanisms of cell death are induced by combined treatment depending on basal anti-EGFR responsiveness.

Optical metabolic imaging of treatment response in human head and neck squamous cell carcinoma

Optical metabolic imaging measures fluorescence intensity and lifetimes from metabolic cofactors nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD). These molecular level measurements provide unique biomarkers for early cellular responses to cancer treatments. Head and neck squamous cell carcinoma (HNSCC) is an attractive target for optical imaging because of easy access to the site using fiber optic probes. Two HNSCC cell lines, SCC25 and SCC61, were treated with Cetuximab (anti-EGFR antibody), BGT226 (PI3K/mTOR inhibitor), or cisplatin (chemotherapy) for 24 hours. Results show increased redox ratio, NADH α1 (contribution from free NADH), and FAD α1 (contribution from protein-bound FAD) for malignant cells compared with the nonmalignant cell line OKF6 (p<0.05). In SCC25 and SCC61 cells, the redox ratio is unaffected by cetuximab treatment and decreases with BGT226 and cisplatin treatment (p<0.05), and these results agree with standard measurements of proliferation rates after treatment. For SCC25, NADH α1 is reduced with BGT226 and cisplatin treatment. For SCC61, NADH α1 is reduced with cetuximab, BGT226, and cisplatin treatment. Trends in NADH α1 are statistically similar to changes in standard measurements of glycolytic rates after treatment. FAD α1 is reduced with cisplatin treatment (p<0.05). These shifts in optical endpoints reflect early metabolic changes induced by drug treatment. Overall, these results indicate that optical metabolic imaging has potential to detect early response to cancer treatment in HNSCC, enabling optimal treatment regimens and improved patient outcomes.

Comparative oncology: ErbB-1 and ErbB-2 homologues in canine cancer are susceptible to cetuximab and trastuzumab targeting

To facilitate comparative oncology trials we compared the biological and molecular homologies of canine (dog; Canis lupus familiaris) and human tumor-associated antigens ErbB-1 and -2. Further, we investigated whether they could serve as targets for anti-ErbB-1 (cetuximab) and anti-ErbB-2 antibodies (trastuzumab), which are highly relevant in human clinical oncology.

Immunohistochemistry of canine mammary cancer showed ErbB-1 overexpression in 3/10 patients and ErbB-2 in 4/10. We report 91% amino acid homology for ErbB-1 and 92% for ErbB-2 between canine and human molecules. Modeling of canine on human ErbB-1 revealed that the cetuximab epitope only differs by 4 amino acids: Lys443 is replaced by Arg, Ser468 by Asn, Gly471 by Asp, and Asn473 by Lys in canines. The trastuzumab binding site is identical in human and canine ErbB-2 apart from a single amino acid change (Pro557 to Ser). Binding of cetuximab and trastuzumab to canine mammary carcinoma cells CF33, CF41, Sh1b and P114 was confirmed by flow cytometry. Both antibodies significantly inhibited canine tumor cell proliferation partly due to growth arrest in G₀/G₁ phase. We explain the lower efficiency on the tested canine than on human SKBR3 and A431 cells, by a 2-log lower expression level of the canine ErbB-1 and -2 molecules.

Our results indicate significant homology of human and canine Erb-1 and -2 tumor associated antigens. The fact that the canine homologues express the cetuximab and trastuzumab epitopes may facilitate antibody-based immunotherapy in dogs. Importantly, the striking similarities of ErbB-1 and -2 molecules open up avenues towards comparative strategies for targeted drug development.

Gefitinib induces epidermal growth factor receptor dimers which alters the interaction characteristics with ¹²⁵I-EGF

The tyrosine kinase inhibitor gefitinib inhibits growth in some tumor types by targeting the epidermal growth factor receptor (EGFR). Previous studies show that the affinity of the EGF-EGFR interaction varies between hosting cell line, and that gefitinib increases the affinity for some cell lines. In this paper, we investigate possible mechanisms behind these observations. Real-time interaction analysis in LigandTracer® Grey revealed that the HER2 dimerization preventing antibody pertuzumab clearly modified the binding of ¹²⁵I-EGF to EGFR on HER2 overexpressing SKOV3 cells in the presence of gefitinib. Pertuzumab did not affect the binding on A431 cells, which express low levels of HER2. Cross-linking measurements showed that gefitinib increased the amount of EGFR dimers 3.0-3.8 times in A431 cells in the absence of EGF. In EGF stimulated SKOV3 cells the amount of EGFR dimers increased 1.8-2.2 times by gefitinib, but this effect was cancelled by pertuzumab. Gefitinib treatment did not alter the number of EGFR or HER2 expressed in tumor cell lines A431, U343, SKOV3 and SKBR3. Real-time binding traces were further analyzed in a novel tool, Interaction Map, which deciphered the different components of the measured interaction and supports EGF binding to multiple binding sites. EGFR and HER2 expression affect the levels of EGFR monomers, homodimers and heterodimers and EGF binds to the various monomeric/dimeric forms of EGFR with unique binding properties. Taken together, we conclude that dimerization explains the varying affinity of EGF-EGFR in different cells, and we propose that gefitinib induces EGFR dimmers, which alters the interaction characteristics with ¹²⁵I-EGF.