po 049 egfr blockade induces a paneth cell like phenotype with rewired signalling dependencies in crc tumoursat maximal response

Introduction Anti-EGFR therapies with the monoclonal antibodies cetuximab and panitumumab have improved survival in colorectal cancer (CRC) patients; nevertheless, incomplete mass obliteration and eventual relapse are a common setback, even after a plateau of maximal response. Preclinical data suggest that tumour recurrence may be fueled by a reservoir of so-called 'drug-tolerant persisters' that engage non-mutational routes of adaptation to therapy. Yet, the molecular underpinnings that sustain residual disease, as well as the strategies to oppose it, are largely unexplored. Material and methods The effects of targeted therapies were evaluated in patient-derived xenografts. The biochemical and biological consequences of drug exposure were gauged by immunohistochemistry and morphometric analyses (in vivo), and by time-lapse imaging, Western Blot, Cell Titer-Glo and Caspase-Glo assays (in vitro). Transcriptional perturbations were assessed by microarray analysis and/or RT-qPCR. The activity of transcriptional modulators was measured by reporter assays in vitro. Results and discussions Residual tumours surviving cetuximab treatment exhibited a quiescent, Wnt-high, and secretory/Paneth cell-like state as a distinctive trait. This pattern outlines that of EGFR-inhibited quiescent stem cells of the normal intestine, suggesting that developmental trajectories are somehow coopted by cancer cells to face external insults. Such phenotype was reversible with drug suspension, pointing to non-genetic plasticity as a determinant of cancer cell reprogramming. Residual tumours also displayed lower expression of EGFR-activating ligands, congruent with reduced EGFR dependency, and showed rewired reliance on compensatory HER2/HER3 activity, as well as persistent PI3K signalling. Mechanistically, the acquisition of Paneth cell-like features was mediated, at least partly, by inactivation of YAP – a key driver of intestinal cell regeneration. Therapeutically, combined blockade of EGFR and PI3K/AKT lessened residual disease burden, but did not lead to long-term disease control. However, treatment with panHER, a mixture of antibodies concurrently targeting EGFR, HER2, and HER3, reduced tumour volumes and delayed tumour relapse after therapy cessation. Conclusion Drug tolerance in cetuximab-sensitive CRC models involves a switch towards a Paneth-cell like state typified by sustained HER2/HER3 and PI3K signalling. Treatment with panHER effectively exhausted residual tumour burden and impeded/delayed late relapse

Colorectal cancer residual disease at maximal response to EGFR blockade displays a druggable Paneth cell–like phenotype

Blockade of epidermal growth factor receptor (EGFR) causes tumor regression in some patients with metastatic colorectal cancer (mCRC). However, residual disease reservoirs typically remain even after maximal response to therapy, leading to relapse. Using patient-derived xenografts (PDXs), we observed that mCRC cells surviving EGFR inhibition exhibited gene expression patterns similar to those of a quiescent subpopulation of normal intestinal secretory precursors with Paneth cell characteristics. Compared with untreated tumors, these pseudodifferentiated tumor remnants had reduced expression of genes encoding EGFR-activating ligands, enhanced activity of human epidermal growth factor receptor 2 (HER2) and HER3, and persistent signaling along the phosphatidylinositol 3-kinase (PI3K) pathway. Clinically, properties of residual disease cells from the PDX models were detected in lingering tumors of responsive patients and in tumors of individuals who had experienced early recurrence. Mechanistically, residual tumor reprogramming after EGFR neutralization was mediated by inactivation of Yes-associated protein (YAP), a master regulator of intestinal epithelium recovery from injury. In preclinical trials, Pan-HER antibodies minimized residual disease, blunted PI3K signaling, and induced long-term tumor control after treatment discontinuation. We found that tolerance to EGFR inhibition is characterized by inactivation of an intrinsic lineage program that drives both regenerative signaling during intestinal repair and EGFR-dependent tumorigenesis. Thus, our results shed light on CRC lineage plasticity as an adaptive escape mechanism from EGFR-targeted therapy and suggest opportunities to preemptively target residual disease

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

Molecular dissection of colorectal cancer in pre-clinical models identifies biomarkers predicting sensitivity to EGFR inhibitors.

Colorectal carcinoma represents a heterogeneous entity, with only a fraction of the tumours responding to available therapies, requiring a better molecular understanding of the disease in precision oncology. To address this challenge, the OncoTrack consortium recruited 106 CRC patients (stages I-IV) and developed a pre-clinical platform generating a compendium of drug sensitivity data totalling >4,000 assays testing 16 clinical drugs on patient-derived in vivo and in vitro models. This large biobank of 106 tumours, 35 organoids and 59 xenografts, with extensive omics data comparing donor tumours and derived models provides a resource for advancing our understanding of CRC. Models recapitulate many of the genetic and transcriptomic features of the donors, but defined less complex molecular sub-groups because of the loss of human stroma. Linking molecular profiles with drug sensitivity patterns identifies novel biomarkers, including a signature outperforming RAS/RAF mutations in predicting sensitivity to the EGFR inhibitor cetuximab