Absent expansion of AXIN2+ hepatocytes and altered physiology in Axin2CreERT2 mice challenges the role of pericentral hepatocytes in homeostatic liver regeneration

Background & Aims: Mouse models of lineage tracing have helped to describe the important subpopulations of hepatocytes responsible for liver regeneration. However, conflicting results have been obtained from different models. Herein, we aimed to reconcile these conflicting reports by repeating a key lineage-tracing study from pericentral hepatocytes and characterising this Axin2CreERT2 model in detail. Methods: We performed detailed characterisation of the labelled population in the Axin2CreERT2 model. We lineage traced this cell population, quantifying the labelled population over 1 year and performed in-depth phenotypic comparisons, including transcriptomics, metabolomics and analysis of proteins through immunohistochemistry, of Axin2CreERT2 mice to WT counterparts. Results: We found that after careful definition of a baseline population, there are marked differences in labelling between male and female mice. Upon induced lineage tracing there was no expansion of the labelled hepatocyte population in Axin2CreERT2 mice. We found substantial evidence of disrupted homeostasis in Axin2CreERT2 mice. Offspring are born with sub-Mendelian ratios and adult mice have perturbations of hepatic Wnt/β-catenin signalling and related metabolomic disturbance. Conclusions: We find no evidence of predominant expansion of the pericentral hepatocyte population during liver homeostatic regeneration. Our data highlight the importance of detailed preclinical model characterisation and the pitfalls which may occur when comparing across sexes and backgrounds of mice and the effects of genetic insertion into native loci. Impact and implications: Understanding the source of cells which regenerate the liver is crucial to harness their potential to regrow injured livers. Herein, we show that cells which were previously thought to repopulate the liver play only a limited role in physiological regeneration. Our data helps to reconcile differing conclusions drawn from results from a number of prior studies and highlights methodological challenges which are relevant to preclinical models more generally

In situ growth in early lung adenocarcinoma may represent precursor growth or invasive clone outgrowth-a clinically relevant distinction.

The switch from in situ to invasive tumor growth represents a crucial stage in the evolution of lung adenocarcinoma. However, the biological understanding of this shift is limited, and 'Noguchi Type C' tumors, being early lung adenocarcinomas with mixed in situ and invasive growth, represent those that are highly valuable in advancing our understanding of this process. All Noguchi Type C adenocarcinomas (n = 110) from the LATTICE-A cohort were reviewed and two patterns of in situ tumor growth were identified: those deemed likely to represent a true shift from precursor in situ to invasive disease ('Noguchi C1') and those in which the lepidic component appeared to represent outgrowth of the invasive tumor along existing airspaces ('Noguchi C2'). Overall Ki67 fraction was greater in C2 tumors and only C1 tumors showed significant increasing Ki67 from in situ to invasive disease. P53 positivity was acquired from in situ to invasive disease in C1 tumors but both components were positive in C2 tumors. Likewise, vimentin expression was increased from in situ to invasive tumor in C1 tumors only. Targeted next generation sequencing of 18 C1 tumors identified four mutations private to the invasive regions, including two in TP53, while 6 C2 tumors showed no private mutations. In the full LATTICe-A cohort, Ki67 fraction classified as either less than or greater than 10% within the in situ component of lung adenocarcinoma was identified as a strong predictor of patient outcome. This supports the proposition that tumors of all stages that have 'high grade' in situ components represent those with aggressive lepidic growth of the invasive clone. Overall these data support that the combined growth of Noguchi C tumors can represent two differing biological states and that 'Noguchi C1' tumors represent the genuine biological shift from in situ to invasive disease

MNK inhibition sensitizes KRAS-mutant colorectal cancer to mTORC1 inhibition by reducing eIF4E phosphorylation and c-MYC expression

KRAS-mutant colorectal cancers (CRC) are resistant to therapeutics, presenting a significant problem for ~40% of cases. Rapalogs, which inhibit mTORC1 and thus protein synthesis, are significantly less potent in KRAS-mutant CRC. Using Kras-mutant mouse models and mouse- and patient-derived organoids we demonstrate that KRAS with G12D mutation fundamentally rewires translation to increase both bulk and mRNA-specific translation initiation. This occurs via the MNK/eIF4E pathway culminating in sustained expression of c-MYC. By genetic and small molecule targeting of this pathway, we acutely sensitize KRASG12D models to rapamycin via suppression of c-MYC. We show that 45% of CRCs have high signaling through mTORC1 and the MNKs, with this signature correlating with a 3.5-year shorter cancer-specific survival in a subset of patients. This work provides a c-MYC-dependent co-targeting strategy with remarkable potency in multiple Kras-mutant mouse models and metastatic human organoids and identifies a patient population who may benefit from its clinical application