RESUMEN
The long-term efficacy of the Epidermal Growth Factor Receptor (EGFR)-targeted antibody cetuximab in advanced colorectal cancer (CRC) patients is limited by the emergence of drug-resistant (persister) cells. Recent studies in other cancer types have shown that cells surviving initial treatment with targeted agents are often vulnerable to alterations in cell metabolism including oxidative stress. Vitamin C (VitC) is an antioxidant agent which can paradoxically trigger oxidative stress at pharmacological dose. Here we tested the hypothesis that VitC in combination with cetuximab could restrain the emergence of secondary resistance to EGFR blockade in CRC RAS/BRAF wild-type models. We found that addition of VitC to cetuximab impairs the emergence of drug persisters, limits the growth of CRC organoids, and significantly delays acquired resistance in CRC patient-derived xenografts. Mechanistically, proteomic and metabolic flux analysis shows that cetuximab blunts carbohydrate metabolism by blocking glucose uptake and glycolysis, beyond promoting slow but progressive ROS production. In parallel, VitC disrupts iron homeostasis and further increases ROS levels ultimately leading to ferroptosis. Combination of VitC and cetuximab orchestrates a synthetic lethal metabolic cell death program triggered by ATP depletion and oxidative stress, which effectively limits the emergence of acquired resistance to anti-EGFR antibodies. Considering that high-dose VitC is known to be safe in cancer patients, our findings might have clinical impact on CRC patients treated with anti-EGFR therapies.
RESUMEN
Cell multiplication in the absence of integrin-derived adhesive signals (anchorage-independent growth) is the phenotypic hallmark of neoplastic transformation. Therefore, the frequently observed up-regulation of some integrins in tumors has been interpreted as an epiphenomenon and not as a causative factor of oncogenic conversion. beta4 integrin stimulates proliferation and survival of epithelial cells and is overexpressed in human carcinomas, often in concomitance with up-regulation of the Met tyrosine kinase receptor for hepatocyte growth factor. Met is not endowed with transforming ability but can exploit the beta4 cytoplasmic tail as a substrate/adaptor for amplification of mitogenic and antiapoptotic responses, independently of cell adhesion. Here, we show that overexpression of beta4 is sufficient to transform rodent fibroblasts, enhances anchorage-independent growth of breast carcinoma cells, and induces tumorigenesis in nude mice; conversely, RNA interference-mediated depletion abrogates the transformed phenotype of neoplastic cells. These autonomous oncogenic properties are dramatically exacerbated upon Met coexpression, suggesting that the integrin can instigate the latent tumorigenic potential of the kinase. A beta4 nonadhesive variant still cooperates with Met for cellular transformation, confirming the adhesion-independent function of beta4 in magnification of Met biological effects. Conversely, a beta4 signaling-incompetent mutant that cannot be efficiently tyrosine phosphorylated by Met and displays reduced ability to activate phosphatidylinositol 3-kinase-dependent and Ras-dependent pathways aborts transformation. Our findings define beta4 as a signaling accomplice (a "servo-oncogene") of tyrosine kinase proto-oncogenes in primary carcinogenesis, evoke an unorthodox function for a prototypic adhesion molecule in the positive regulation of anchorage-independent growth, and suggest the use of beta4 as a target for anticancer therapy.