Defective Hippo/YAP signaling in the liver results in tissue overgrowth and development of hepatocellular carcinoma (HCC). Here, we uncover mechanisms of YAP-mediated hepatocyte reprogramming and HCC ...pathogenesis. YAP functions as a rheostat in maintaining metabolic specialization, differentiation, and quiescence within the hepatocyte compartment. Increased or decreased YAP activity reprograms subsets of hepatocytes to different fates associated with deregulation of the HNF4A, CTNNB1, and E2F transcriptional programs that control hepatocyte quiescence and differentiation. Importantly, treatment with small interfering RNA-lipid nanoparticles (siRNA-LNPs) targeting YAP restores hepatocyte differentiation and causes pronounced tumor regression in a genetically engineered mouse HCC model. Furthermore, YAP targets are enriched in an aggressive human HCC subtype characterized by a proliferative signature and absence of CTNNB1 mutations. Thus, our work reveals Hippo signaling as a key regulator of the positional identity of hepatocytes, supports targeting of YAP using siRNA-LNPs as a paradigm of differentiation-based therapy, and identifies an HCC subtype that is potentially responsive to this approach.
Display omitted
•Yap is a rheostat for positional identity and metabolic zonation of hepatocytes•Activated Yap subverts the HNF4α and β-catenin hepatocyte differentiation programs•siYap-LNPs cause advanced HCC to regress and undergo hepatocyte differentiation•An aggressive human HCC subtype with WT CTNNB1 exhibits a Yap activity signature
Fitamant et al. show that the identity of specialized subpopulations of hepatocytes is controlled by Yap levels and that aberrant Yap activation overrides hepatocyte differentiation to initiate and maintain hepatocellular carcinoma (HCC) growth. In advanced HCC, Yap inhibition restores hepatocyte differentiation, supporting the concept of differentiation therapy against epithelial cancers.
Pancreatic ductal adenocarcinoma (PDA) is the most lethal of common human malignancies, with no truly effective therapies for advanced disease. Preclinical studies have suggested a therapeutic ...benefit of targeting the Hedgehog (Hh) signaling pathway, which is activated throughout the course of PDA progression by expression of Hh ligands in the neoplastic epithelium and paracrine response in the stromal fibroblasts. Clinical trials to test this possibility, however, have yielded disappointing results. To further investigate the role of Hh signaling in the formation of PDA and its precursor lesion, pancreatic intraepithelial neoplasia (PanIN), we examined the effects of genetic or pharmacologic inhibition of Hh pathway activity in three distinct genetically engineered mouse models and found that Hh pathway inhibition accelerates rather than delays progression of oncogenic Kras-driven disease. Notably, pharmacologic inhibition of Hh pathway activity affected the balance between epithelial and stromal elements, suppressing stromal desmoplasia but also causing accelerated growth of the PanIN epithelium. In striking contrast, pathway activation using a small molecule agonist caused stromal hyperplasia and reduced epithelial proliferation. These results indicate that stromal response to Hh signaling is protective against PDA and that pharmacologic activation of pathway response can slow tumorigenesis. Our results provide evidence for a restraining role of stroma in PDA progression, suggesting an explanation for the failure of Hh inhibitors in clinical trials and pointing to the possibility of a novel type of therapeutic intervention.
Intermediary metabolism generates substrates for chromatin modification, enabling the potential coupling of metabolic and epigenetic states. Here we identify a network linking metabolic and ...epigenetic alterations that is central to oncogenic transformation downstream of the liver kinase B1 (LKB1, also known as STK11) tumour suppressor, an integrator of nutrient availability, metabolism and growth. By developing genetically engineered mouse models and primary pancreatic epithelial cells, and employing transcriptional, proteomics, and metabolic analyses, we find that oncogenic cooperation between LKB1 loss and KRAS activation is fuelled by pronounced mTOR-dependent induction of the serine-glycine-one-carbon pathway coupled to S-adenosylmethionine generation. At the same time, DNA methyltransferases are upregulated, leading to elevation in DNA methylation with particular enrichment at retrotransposon elements associated with their transcriptional silencing. Correspondingly, LKB1 deficiency sensitizes cells and tumours to inhibition of serine biosynthesis and DNA methylation. Thus, we define a hypermetabolic state that incites changes in the epigenetic landscape to support tumorigenic growth of LKB1-mutant cells, while resulting in potential therapeutic vulnerabilities.
Most retroviruses require translational recoding of a viral messenger RNA stop codon to maintain a precise ratio of structural (Gag) and enzymatic (Pol) proteins during virus assembly. Pol is ...expressed exclusively as a Gag-Pol fusion either by ribosomal frameshifting or by read-through of the gag stop codon. Both of these mechanisms occur infrequently and only affect 5-10% of translating ribosomes, allowing the virus to maintain the critical Gag to Gag-Pol ratio. Although it is understood that the frequency of the recoding event is regulated by cis RNA motifs, no mechanistic explanation is currently available for how the critical protein ratio is maintained. Here we present the NMR structure of the murine leukaemia virus recoding signal and show that a protonation-dependent switch occurs to induce the active conformation. The equilibrium is such that at physiological pH the active, read-through permissive conformation is populated at approximately 6%: a level that correlates with in vivo protein quantities. The RNA functions by a highly sensitive, chemo-mechanical coupling tuned to ensure an optimal read-through frequency. Similar observations for a frameshifting signal indicate that this novel equilibrium-based mechanism may have a general role in translational recoding.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
5606
Background: The National Comprehensive Cancer Network (NCCN) recommends that patients with endometrial cancer under age 50 undergo germline genetic testing. Despite this recommendation, ...completion rates are suboptimal for patients with gynecologic malignancies. The reasons for failure to complete testing are unknown, but oncology providers may not refer patients to genetic counselors, who frequently order this testing. Best practice advisories (BPAs) in electronic medical records can alert providers of patients who meet guideline-based treatments and testing criteria. It is unknown how oncology providers interact with a BPA indicating patients with endometrial cancer meet NCCN germline testing criteria. The objective of this study is to evaluate genetic counseling referral patterns after implementing a BPA. Methods: Our team developed a BPA to prompt oncology providers to order genetic counseling referrals for patients diagnosed with endometrial or uterine cancer under age 50. We reviewed all provider-BPA interactions between go-live (January 2022) and January 2023. Patient demographic, histopathologic, and cancer treatment data were collected. Provider actions, including BPA cancellation and order placement, were collected. The Chi-Square goodness of fit test was used to identify differences in referral rates by patient or disease characteristics. Results: The BPA displayed 1121 times for 103 patients. Attending physicians received 535 alerts, fellow physicians – 269, and advanced practice providers (APPs) – 317. The median number of alerts per patient was 7 (range 1-87). Of the 103 patients, 23 were excluded from analysis due to no diagnosis of endometrial cancer, patient declined referral, previously completed, or a lack of provider visits within the study period. Of the 80 eligible patients, 36 (45%) received referrals; 18 were placed by attending physicians, 17 by fellows, and one by an APP. Patients under age 40 versus age 40-49 were more likely to be referred (65% vs. 35%; p = 0.011). Patients with active disease were more likely to be referred than those in surveillance (65% vs. 18%; p < 0.001). There were no differences in referral rates by primary language, race, body mass index ≥40, fertility-sparing versus definitive treatment, stage I versus stage II-IV disease, or grade 1-2 versus three tumors. Conclusions: Despite implementing a BPA, only 45% of eligible patients received indicated referrals. Attending and fellow physicians frequently manage patients with active disease and often order referrals; however, APPs frequently manage patients in surveillance and infrequently place referrals, highlighting an opportunity for education. In addition, patients aged 40-49 are less likely to be referred, suggesting a need for new strategies to improve referral rates. Further research is indicated to identify referral barriers for patients undergoing active treatment.
Intermediary metabolism generates substrates for chromatin modification, enabling potential coupling of metabolic and epigenetic states. Here, we identify such a network as a major component of ...oncogenic transformation downstream of the LKB1/STK11 tumour suppressor, an integrator of nutrient availability, metabolism and growth. By developing genetically engineered mouse models and primary pancreatic epithelial cells and employing transcriptional, proteomics, and metabolic analyses, we find that oncogenic cooperation between LKB1 loss and KRAS activation is fueled by pronounced mTOR-dependent induction of the serine-glycine-one carbon pathway coupled to S-adenosylmethionine generation. In concert, DNA methyltransferases are upregulated, leading to elevation in DNA methylation, with particular enrichment at retrotransposon elements associated with their transcriptional silencing. Correspondingly, LKB1 deficiency sensitizes cells and tumours to inhibition of serine biosynthesis and DNA methylation. Thus, we define a hypermetabolic state that incites changes in the epigenetic landscape to support tumourigenic growth of LKB1-mutant cells, while resulting in novel therapeutic vulnerabilities.
Abstract
The LKB1 tumor suppressor encodes a serine/threonine kinase that serves as a master regulator of energy metabolism. Germline mutations in LKB1 cause the Peutz-Jeghers polyposis and cancer ...syndrome and are associated with a high risk of pancreatic cancer development. Despite being the subject of extensive investigation for more than 15 years, the primary mechanisms of LKB1-mediated tumor suppression remain poorly defined. The best-characterized function of LKB1 in cell physiology is to coordinate adaptation to a drop in ATP stores, shutting down multiple biosynthetic processes and favoring catabolic pathways, thereby restoring cellular energy charge. Since LKB1 has pleiotropic effects on cell polarity, migration, and inflammation in addition to cell metabolism, it remains uncertain to what extent LKB1-mediated tumor suppression involves its roles in metabolic reprogramming. In this regard, LKB1 inactivation renders cells vulnerable to a number of metabolic stress stimuli such as glucose deprivation or reactive oxygen species (ROS), indicating that alterations in metabolic control may decrease, rather than increase, the fitness of LKB1 deficient cells. To resolve these questions, we have conducted comprehensive metabolic profiling and functional studies that revealed that LKB1 inactivation results in greatly improved efficiency of nutrient acquisition and utilization, which fuels accelerated cell growth and tumorigenesis. By using a series of primary epithelial culture systems and genetically engineered mouse models coupled with integrative metabolic profiling and flux analyses, we find that LKB1 loss potentiates glucose uptake and glycolysis, and diverts a significant amount of glycolytic intermediates toward biosynthetic processes. Most notably fatty acid and nucleotide pools are greatly expanded upon LKB1 inactivation. This extensive metabolic reprogramming results in a shift in the nutrient requirements of LKB1 mutant cells including a reduced dependence on select exogenous amino acids and greatly increased need for glutamine and glucose. Collectively, our studies uncover adaptive metabolic changes conferred by LKB1 inactivation and suggest potential targetable vulnerabilities of LKB1 mutant cancers.
Citation Format: Filippos Kottakis, Brandon N. Nicolay, Nagle M. Julia, Marc Liesa, Orian S. Sirihai, Nicholas J. Dyson, Nabeel Bardeesy. Metabolic changes, associated with loss of the tumor suppressor LKB1, promote tumorigenesis. abstract. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr B42.
Total thyroidectomy as part of thyroid cancer treatment results in hypothyroidism requiring lifelong daily thyroid hormone replacement. Unbalanced hormone levels result in persistent complaints such ...as fatigue, constipation, and weight increase. Therefore, we aimed to investigate a patient-derived thyroid organoid model with the potential to regenerate the thyroid gland. Murine and human thyroid-derived cells were cultured as organoids capable of self-renewal and which expressed proliferation and putative stem cell and thyroid characteristics, without a change in the expression of thyroid tumor-related genes. These organoids formed thyroid-tissue-resembling structures in culture. (Xeno-)transplantation of 600,000 dispersed organoid cells underneath the kidney capsule of a hypothyroid mouse model resulted in the generation of hormone-producing thyroid-resembling follicles. This study provides evidence that thyroid-lineage-specific cells can form organoids that are able to self-renew and differentiate into functional thyroid tissue. Subsequent (xeno-)transplantation of these thyroid organoids demonstrates a proof of principle for functional miniature gland formation.
Display omitted
•Thyroid-organoid-derived cells can self-renew and form all tissue lineages•Thyroid organoids express putative stem cell markers and no tumor gene expression•Maturation of these organoids leads to formation of tissue-resembling mini-glands•(Xeno-)transplantation into hypothyroid mice regenerates thyroid-resembling tissue
In this article, Ogundipe and colleagues demonstrate that thyroid gland-derived cells can be cultured as organoids for a prolonged time and differentiate in vitro to form hormone-producing mini-glands. (Xeno-)transplantation of dissociated organoids into hypothyroid mice allows generation of hormone-producing tissue-resembling follicles. These findings indicate that thyroid-lineage-specific cells contain proliferative potential to form thyroid-derived organoids capable of generating functional tissue.
PDF
