Overcoming acquired resistance to cetuximab by dual targeting HER family receptors with antibody-based therapy

Abstract

BackgroundCetuximab, an anti-EGFR monoclonal antibody, is used to treat several cancers. However, many patients who initially respond to cetuximab acquire resistance. To examine mechanisms of acquired resistance, we developed a series of cetuximab-resistant (CtxR) clones derived from the cetuximab sensitive (CtxS) non-small cell lung cancer (NSCLC) cell line H226. Previous studies characterizing this model revealed that: 1) EGFR was robustly overexpressed in CtxR clones due to decreased EGFR ubiquitination and degradation and 2) CtxR clones expressed increased HER2 and HER3 activation resulting in constitutive activation of the PI3K/AKT signaling axis. These findings suggest that dual targeting HER family receptors would be highly beneficial in the CtxR setting.ResultsSince HER3 has been implicated in resistance to EGFR inhibitors, the efficacy of dually targeting both EGFR and HER3 in CtxR models was evaluated. First, EGFR and HER3 expression were knocked down with siRNAs. Compared to the CtxS parental cell line (HP), all CtxR clones exhibited robust decreases in cell proliferation upon dual knockdown. Analysis of CtxR clones indicated that neuregulin-1 was highly overexpressed compared to HP cells. Incubation of HP cells with neuregulin-1 rendered them resistant to cetuximab. Next, dual treatment of CtxR clones with cetuximab and the HER3 neutralizing monoclonal antibody (mAb) U3-1287 led to potent anti-proliferative effects. Blockade of EGFR with cetuximab resulted in inactivation of MAPK, while blockade of HER3 with U3-1287 resulted in the inactivation of AKT. Treatment with both mAbs resulted in knockdown of both signaling pathways simultaneously. HER2 was also strongly inactivated upon dual mAb therapy, suggesting that this treatment regimen can diminish signaling from three HER family receptors. De novo CtxR H226 mouse xenografts were established to determine if dual therapy could overcome acquired resistance to cetuximab in vivo. Tumors that had acquired resistance to cetuximab were significantly growth delayed upon dual treatment of U3-1287 and cetuximab compared to those continued on cetuximab only. Combinatorial-treated xenograft tumors expressed decreased Ki67 and increased cleaved caspase-3 levels compared to tumors treated with either monotherapy.ConclusionsThese studies demonstrate that dually targeting HER family receptors with antibody-based therapies can overcome acquired resistance to cetuximab.

Targeting the HER family with Pan-HER effectively overcomes resistance to cetuximab

“…Once cetuximab-resistant tumors reached a volume of ~800 mm 3 , mice were grouped according to tumor size at the time of resistance. Cetuximabresistant tumors were observed in 28 of 40 mice (70 %), which is in line with previous studies (14,20,21). Mice were then randomly subdivided into 13 cetuximab-resistant xenograft groups (28 mice in total), nine of which are shown in Figure 5A.…”

Cetuximab Resistance in Squamous Carcinomas of the Upper Aerodigestive Tract Is Driven by Receptor Tyrosine Kinase Plasticity: Potential for mAb Mixtures

“…HER3 is transcriptionally regulated by PI3K/AKT signaling, and inhibition of AKT activity has been shown to induce HER3 transcription in a FOXO-dependent manner (47)(48)(49). Multiple studies have confirmed a role of HER-3 in acquired resistance to EGFR inhibition (35,45,50). Increased IGF1R activity is another well-described mechanism of resistance to EGFR inhibition.…”

Secretome Signature Identifies ADAM17 as Novel Target for Radiosensitization of Non–Small Cell Lung Cancer

“…While EGFR-directed agents, also in combination with radiotherapy, are a promising treatment strategy, many tumors rapidly acquire resistance during the course of treatment. Alternative concepts suggest combination therapies of EGFR inhibition in combination with inhibitors for other HER family receptors (44,45). A major advantage of targeting ADAM17 includes its broad spectrum of downregulated substrates for all different HER family and other RTKs, which might increase the potency of direct ADAM17 targeting as compared with the inhibition of individual receptors.…”