Circulating pEGFR Is a Candidate Response Biomarker of Cetuximab Therapy in Colorectal Cancer

Abstract

Purpose: The lack of secreted biomarkers measurable by noninvasive tests hampers the development of effective targeted therapies against cancer. Our hypothesis is that cetuximab (an anti-EGFR mAb) induces a specific secretome in colorectal cancer cells that could be exploited for biomarker discovery.Experimental Design: Considering the strong correlation between mutated KRAS and a lack of response to cetuximab therapy, we addressed whether performing secretome-based proteomics on isogenic colorectal cancer cells sharing the KRAS mutations found on patients would yield candidate-secreted biomarkers useful in the clinical setting. Because 2D culture did not optimally model the sensitivity/resistance to cetuximab observed in colorectal cancer patients, we moved to 3D spheroids, developing a methodology for both cell-based assays and quantitative proteomics.Results: A large comparative quantitative proteomic analysis of the 3D secretomes of colorectal cancer isogenic cells treated with cetuximab uncovered an EGFR pathway-centric secretome found only when cells grow in 3D. The validation of the secretome findings in plasma of colorectal cancer patients, suggests that phosphorylated-EGFR (pEGFR) is a candidate-secreted biomarker of response to cetuximab.Conclusions: We have proved that 3D spheroids from colorectal cancer cells generate secretomes with a drug-sensitivity profile that correlates well with patients with colorectal cancer, illustrating molecular connections between intracellular and extracellular signaling. Furthermore, we show how the secretion of pEGFR is associated with the sensitivity of colorectal cancer cells to cetuximab and the response of patients with colorectal cancer to the drug. Our work could allow the noninvasive monitoring of anti-EGFR treatment in patients with colorectal cancer. Clin Cancer Res; 20(24); 6346-56. Ó2014 AACR.

Extracellular HMGA1 Promotes Tumor Invasion and Metastasis in Triple-Negative Breast Cancer

“…Some of these unconventionally secreted proteins have a welldefined intracellular function (6). We have previously shown that the unconventional secretion of the EGFR correlates with the response of colorectal cancer patients to the therapeutic antibody cetuximab (8). Agreeing with our observations, proteins classically located intracellularly such as HSP90, tRNA synthetases, and HMGB1 have recently been identified in the extracellular space performing alternative functions related to cancer (9)(10)(11).…”

Enhancing the evaluation of PI3K inhibitors through 3D melanoma models

“…Interestingly, we observed that two compounds with limited effects in 2D culture displayed enhanced activity in the 3D setting (PX‐866 and AZD6482); this raises the possibility that certain PI3K inhibitors may be underestimated based on adherent culture results alone. This needs careful exploration given that 3D disease models can be more reflective of the drug sensitivity profile found in patients (Katsila et al., ).…”

Clinical Proteomics in Colorectal Cancer, a Promising Tool for Improving Personalised Medicine

“…They noted that during cetuximab treatment, pEGFR levels increased in patients who responded well to treatment, did not evolve in patients with stabilisation of the disease, and decreased in patients with disease progression. The authors subsequently validated this hypothesis by measuring the secretome in 3D cultures obtained from several lines of SW48 colorectal cancer cells with different sensitivities to cetuximab [60]. This latter study is a good example of a proteomic study performed on human samples and validated by in vitro cell models, hence promoting the use of 3D cell cultures obtained directly from patient samples to pre-test the treatment.…”