Obesity is a risk factor for breast cancer development. A recent hypothesis suggests that the adipokines, adiponectin and leptin, are involved in breast cancer development. This prompted us to investigate the role of adiponectin and leptin in mammary carcinogenesis. Adiponectin receptors (AdipoR1 and AdipoR2) and leptin receptor (Ob-Rt, representing all the isoforms of Ob-R) proteins were detected by immunohistochemistry in in situ ductal carcinoma, invasive ductal malignancy, and healthy adjacent tissue. In addition, mRNA expression of adiponectin, AdipoR1, AdipoR2, leptin, Ob-Rt, and Ob-Rl (the long isoform of Ob-R) was observed in MCF-7 breast cancer cells. Interestingly, leptin mRNA expression was 34.7-fold higher than adiponectin mRNA expression in the MCF-7 cell line. Moreover, adiponectin (10 μg/ml) tended to decrease the mRNA expression of leptin (−36%) and Ob-Rl (−28%) and significantly decreased Ob-Rt mRNA level (−26%). In contrast, leptin treatment (1 μg/ml) significantly decreased AdipoR1 mRNA (−23%). Adiponectin treatment (10 μg/ml) inhibited the proliferation of MCF-7 cells, whereas leptin (1 μg/ml) stimulated the growth of cancer cells. In addition, adiponectin inhibited leptin-induced cell proliferation (both 1 μg/ml). Using microarray analysis, we found that adiponectin reduced the mRNA levels of genes involved in cell cycle regulation (mitogen-activated protein kinase 3 and ATM), apoptosis (BAG1, BAG3, and TP53), and potential diagnosis/prognosis markers (ACADS, CYP19A1, DEGS1, and EVL), whereas leptin induced progesterone receptor mRNA expression. In conclusion, the current study indicates an interaction of leptin- and adiponectin-signaling pathways in MCF-7 cancer cells whose proliferation is stimulated by leptin and suppressed by adiponectin.

The development of in vitro culture systems quantitatively and qualitatively recapitulating normal breast biology is key to the understanding of mammary gland biology. Current three-dimensional mammary culture systems have not demonstrated concurrent proliferation and functional differentiation ex vivo in any system for longer than 2 weeks. Here, we identify conditions including Neuregulin1 and R-spondin 1, allowing maintenance and expansion of mammary organoids for 2.5 months in culture. The organoids comprise distinct basal and luminal compartments complete with functional steroid receptors and stem/progenitor cells able to reconstitute a complete mammary gland in vivo. Alternative conditions are also described that promote enrichment of basal cells organized into multiple layers surrounding a keratinous core, reminiscent of structures observed in MMTV-Wnt1 tumours. These conditions comprise a unique tool that should further understanding of normal mammary gland development, the molecular mechanism of hormone action and signalling events whose deregulation leads to breast tumourigenesis.

Significance: Clostridioides difficile is the most common cause of hospital-acquired diarrhea. It is responsible for more than half of all hospital enteric infections and >90% of mortalities resulting from these infections. Gut damage sustained during C. difficile infection is devastating, inducing epithelial damage deep into the gut tissue, to regions where stem cells responsible for tissue repair reside. Our work has shown that toxin-mediated damage during severe murine C. difficile infection alters the colonic epithelial protective barrier, which promotes colonic stem cell dysfunction, exacerbating disease and perturbing the repair capacity of the host. Furthermore, we have shown that this damage induces a chronically dysfunctional stem cell state, which prevents homeostatic cellular repair, possibly increasing susceptibility to subsequent infections or disease recurrence.

Oncogenic KRAS mutations are major drivers of lung adenocarcinoma (LAC), yet the direct therapeutic targeting of KRAS has been problematic. Here, we reveal an obligate requirement by oncogenic KRAS for the ADAM17 protease in LAC. In genetically engineered and xenograft (human cell line and patient‐derived) Kras^G12D‐driven LAC models, the specific blockade of ADAM17, including with a non‐toxic prodomain inhibitor, suppressed tumor burden by reducing cellular proliferation. The pro‐tumorigenic activity of ADAM17 was dependent upon its threonine phosphorylation by p38 MAPK, along with the preferential shedding of the ADAM17 substrate, IL‐6R, to release soluble IL‐6R that drives IL‐6 trans‐signaling via the ERK1/2 MAPK pathway. The requirement for ADAM17 in Kras^G12D‐driven LAC was independent of bone marrow‐derived immune cells. Furthermore, in KRAS mutant human LAC, there was a significant positive correlation between augmented phospho‐ADAM17 levels, observed primarily in epithelial rather than immune cells, and activation of ERK and p38 MAPK pathways. Collectively, these findings identify ADAM17 as a druggable target for oncogenic KRAS‐driven LAC and provide the rationale to employ ADAM17‐based therapeutic strategies for targeting KRAS mutant cancers. Synopsis Oncogenic KRAS mutations are associated with one‐third of lung adenocarcinoma (LAC) cases, yet the downstream molecular events that facilitate KRAS‐mediated tumorigenesis in the lung remain unresolved. This study reveals an obligate requirement by oncogenic KRAS for the ADAM17 protease in LAC. The specific genetic and therapeutic targeting of ADAM17, the latter with a non‐toxic prodomain inhibitor, suppressed tumour burden by reducing cellular proliferation in genetically‐engineered and xenograft mutant KRAS‐driven LAC models. The pro‐tumorigenic activity of ADAM17 in LAC was dependent upon its threonine phosphorylation by p38 MAPK. ADAM17 preferentially shed the substrate, IL‐6R, during LAC to release soluble IL‐6R that drives IL‐6 trans‐signaling via the ERK1/2 MAPK pathway. The requirement for ADAM17 in mutant KRAS‐driven LAC was independent of bone marrow‐derived hematopoietic immune cells. In KRAS mutant human LAC, augmented phospho‐ADAM17 levels were observed primarily in epithelial rather than immune cells, and significantly and positively correlated with activated p38 and ERK1/2 MAPK pathways.