Biology subjects

Frankel, T.

Publications and source records attributed to Frankel, T..

3 recordsLinked to original sources

bioRxiv2025

EGFR activation in cholangiocytes promotes extrahepatic bile duct regeneration after injury

Background & AimsThe epidermal growth factor (EGF) receptor family of tyrosine kinases regulates development and homeostasis of digestive organs including the liver and bile ducts. It consists of four receptors, EGF receptor (EGFR) and erythroblastoma oncogene B 2-4 (ERBB2-4), and their corresponding ligands. EGF signaling promotes intrahepatic cholangiocyte proliferation, bipotent cell transdifferentiation into cholangiocytes, bile duct branching, and cholangiocarcinoma (CCA) aggressiveness. The EGF family signaling contribution to extrahepatic bile duct (EHBD) regeneration is not well defined. This work is aimed at determining the fundamental role of the EGF signaling network in the biliary proliferative response to EHBD obstruction. ApproachWe used mouse bile duct ligation to model obstructive EHBD injury, and human and mouse EHBD organoids for in vitro studies. We tested activating and inhibitory paradigms with recombinant EGF family ligands and receptor antagonists. Transcriptomic and immunohistochemistry analyses informed EGF signaling changes and cellular localization at homeostasis and after obstruction. ResultsAt homeostasis, the EHBD expressed EGFR ligands Tgfa, Btc, Hb-egf and Nrg4 in cholangiocytes, and Egf in stromal cells. Erbb2 and Erbb3 were predominant receptors expressed in cholangiocytes and Egfr in stromal cells at baseline. After EHBD obstruction, injury-induced biliary hyperproliferation was associated with increased abundance of Areg, Hb-egf, Tgf and Btc ligands and Egfr receptor in cholangiocytes with resulting epithelial EGFR activation. In biliary organoids, EGFR ligands induced organoid growth, and inhibition of EGFR, but not ERBB2, dampened cholangiocyte proliferation. Accordingly, EGFR inhibition in mice led to a decrease in the biliary proliferative response after EHBD obstruction. ConclusionThe obstruction-induced biliary proliferation is an EGFR-mediated response suggesting context-and receptor-specific EGF signaling network involvement in EHBD regeneration after injury.

physiology↗

bioRxiv2024

Isolation and characterization of microbiota from human pancreatic tumors and small intestine

Pancreatic ductal adenocarcinoma has a unique tumor microbiome and the systemic depletion of bacteria or fungi using antibiotic/antifungal cocktails leads to a decrease in pancreatic tumor burden in mice. However, functional studies remain rare due to the limited availability of clinically relevant microbiota. Here, we describe in detail the isolation of bacteria and fungi from the small intestine and tumor of pancreatic cancer patients at the Rogel Cancer Center. We then further characterized the impact of a newly isolated Klebsiella oxytoca strain (UMKO1) on the pancreatic tumor microenvironment using bacterial genome sequencing, untargeted and targeted metabolomics, as well as an ex vivo tumor transplant system. We found that UMKO1 possesses a gene for the long form of cytidine deaminase, which can inactivate the standard PDAC chemotherapeutic agent gemcitabine. In addition, we found that UMKO1 can produce several indoles when grown in tumor-like conditions, metabolites that can lead to an immune suppressive environment and interfere with therapy outcome. To test this in detail, we assessed changes in immune populations in pancreatic tumor explants upon exposure to the supernatant of UMKO1 and other isolated bacteria grown in tumor Interstitial fluid media (TIFM). We found that while none of the bacterial supernatants changed the abundance of CD8 T cells, granzyme B positive CD8 T cells were the lowest in tumor explants exposed to UMKO1, and not other isolated Klebsiella species or the non-pathogenic laboratory strain E. coli K12. In summary, the isolated collection of bacteria and fungi from this study are a valuable toolbox to study the impact of microbiota on pancreatic cancer.

cancer biology↗

bioRxiv2023

KRASG12D-mediated PanIN progression in mice is affected by gene driving cre recombinase expression

The fundamental biology of pancreatic ductal adenocarcinoma has been greatly impacted by the characterization of genetically modified mouse models that allow temporal and spatial activation of oncogenic KRAS (KRASG12D). The most commonly used model involves targeted insertion of a cre recombinase into the Ptf1a gene. However, this approach disrupts the Ptf1a gene, resulting in haploinsufficiency that likely affects sensitivity to oncogenic KRAS (KRASG12D). The goal of this study was to determine if Ptf1a haploinsufficiency affected the acinar cell response to KRASG12D before and after induction of pancreatic injury. We performed morphological and molecular analysis of three mouse lines that express a tamoxifen-inducible cre recombinase to activate KRASG12D in acinar cells of the pancreas. The cre-recombinase was targeted to the acinar-specific transcription factor genes, Ptf1a and Mist1/Bhlha15, or expressed within a BAC-derived Elastase transgene. Up to two months after tamoxifen induction of KRASG12D, morphological changes were negligible. However, induction of pancreatic injury by cerulein resulted in stark differences in tissue morphology between lines within seven days, which were maintained for at least five weeks after injury. Ptf1acreERT pancreata showed widespread PanIN lesions and fibrosis, while the Mist1creERT and Ela-creERT models showed reduced amounts of pre-neoplastic lesions. RNA-seq analysis prior to inducing injury suggested Ptf1acreERT and Mist1creERT lines have unique profiles of gene expression that predict a differential response to injury. Multiplex analysis of pancreatic tissue confirmed different inflammatory responses between the lines. These findings suggest understanding the mechanisms underlying the differential response to KRASG12D will help in further defining the intrinsic KRAS-driven mechanisms of neoplasia initiation.

cancer biology↗