Small molecular weight epigenetic inhibitors modulate the extracellular matrix during pancreatic acinar ductal metaplasia.

The pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment is distinguished by a high degree of fibrosis and inflammation, known as desmoplasia. Desmoplasia increases the stromal deposition and extracellular matrix (ECM) stiffness observed in the tumor microenvironment, contributing to the dampened penetration of pharmacological agents. The molecular and biophysical composition of the ECM during the earliest cellular changes in the development of PDAC, i.e. acinar ductal metaplasia (ADM), has not been extensively explored. We report that the mRNA expression of key protein components of the ECM increases during ADM in p48Cre/+;LSL-KrasG12D (KC) mouse acinar organoids cultured in Matrigel. Treatment of the organoids with small molecular weight epigenetic modulating compounds that inhibit or reverse ADM (largazole, FK228 and chaetocin) dramatically reduced the tissue mRNA expression of collagens, hyaluronan synthase, laminin and fibronectin. The storage moduli, determined by video tracking of fluorescent nanoparticles embedded into the Matrigel, increased during ADM and was reduced following treatment with the epigenetic modulating compounds. We report that the ECM of mouse organoids stiffens during ADM and is further enhanced by the presence of mutant Kras. Moreover, select HDAC and HMT inhibitors reduced the mRNA expression of ECM components and ECM stiffness during inhibition and reversal of ADM, suggesting that these compounds may be useful as adjuvants to enhance the tumor penetration of agents used to treat PDAC.

Epigenetic small-molecule screen for inhibition and reversal of acinar ductal metaplasia in mouse pancreatic organoids.

Background: Acinar ductal metaplasia (ADM) is among the earliest initiating events in pancreatic ductal adenocarcinoma (PDAC) development. Methods: We developed a novel morphology-based screen using organoids from wildtype and p48Cre/+ (Cre) mice to discover epigenetic modulators that inhibit or reverse pancreatic ADM more effectively than the broad-spectrum HDAC inhibitor trichostatin A (TSA). Results: Of the 144 compounds screened, nine hits and two additional natural product HDAC inhibitors were validated by dose-response analysis. The class I HDAC inhibitors apicidin and FK228, and the histone methyltransferase inhibitor chaetocin demonstrated pronounced ADM inhibition and reversal without inducing significant cytotoxicity at 1 µM. Thioester prodrug class I HDAC inhibitor largazole attenuated ADM while its disulfide homodimer was effective in both ADM inhibition and reversal. Prioritized compounds were validated for ADM reversal in p48Cre/+; LSL-KrasG12D/+ (KC) mouse organoids using both morphological and molecular endpoints. Molecular index analysis of ADM reversal in KC mouse organoids demonstrated improved activity compared to TSA. Improved prodrug stability translated into a stronger phenotypic and molecular response. RNA-sequencing indicated that angiotensinogen was the top inhibited pathway during ADM reversal. Conclusion: Our findings demonstrate a unique epigenetic mechanism and suggest that the phenotypic screen developed here may be applied to discover potential treatments for PDAC.

Epigenetic Small-Molecule Screen for Inhibition and Reversal of Acinar Ductal Metaplasia in Mouse Pancreatic Organoids.

Background: Acinar ductal metaplasia (ADM) is among the earliest initiating events in pancreatic ductal adenocarcinoma (PDAC) development. Methods: We developed a novel morphology-based screen using organoids from wildtype and p48 Cre/+ (Cre) mice to discover epigenetic modulators that inhibit or reverse pancreatic ADM more effectively than the broad-spectrum HDAC inhibitor trichostatin A (TSA). Results: Of the 144 compounds screened, nine hits and two additional natural product HDAC inhibitors were validated by dose-response analysis. The class I HDAC inhibitors apicidin and FK228, and the histone methyltransferase inhibitor chaetocin demonstrated pronounced ADM inhibition and reversal without inducing significant cytotoxicity at 1 µM. Thioester prodrug class I HDAC inhibitor largazole attenuated ADM while its disulfide homodimer was effective in both ADM inhibition and reversal. Prioritized compounds were validated for ADM reversal in p48 Cre/+ ;LSL-Kras G12D/+ (KC) mouse organoids using both morphological and molecular endpoints. Molecular index analysis of ADM reversal in KC mouse organoids demonstrated improved activity compared to TSA. Improved prodrug stability translated into a stronger phenotypic and molecular response. RNA-sequencing indicated that angiotensinogen was the top inhibited pathway during ADM reversal. Conclusion: Our findings demonstrate a unique epigenetic mechanism and suggest that the phenotypic screen developed here may be applied to discover potential treatments for PDAC.

Transcriptional Profile of Human Pancreatic Acinar Ductal Metaplasia.

BACKGROUND AND AIMS: Aberrant acinar to ductal metaplasia (ADM), one of the earliest events involved in exocrine pancreatic cancer development, is typically studied using pancreata from genetically engineered mouse models. METHODS: We used primary, human pancreatic acinar cells from organ donors to evaluate the transcriptional and pathway profiles during the course of ADM. RESULTS: Following 6 days of three-dimensional culture on Matrigel, acinar cells underwent morphological and molecular changes indicative of ADM. mRNA from 14 donors' paired cells (day 0, acinar phenotype and day 6, ductal phenotype) was subjected to whole transcriptome sequencing. Acinar cell specific genes were significantly downregulated in the samples from the day 6 cultures while ductal cell-specific genes were upregulated. Several regulons of ADM were identified including transcription factors with reduced activity (PTF1A, RBPJL, and BHLHA15) and those ductal and progenitor transcription factors with increased activity (HNF1B, SOX11, and SOX4). Cells with the ductal phenotype contained higher expression of genes increased in pancreatic cancer while cells with an acinar phenotype had lower expression of cancer-associated genes. CONCLUSION: Our findings support the relevancy of human in vitro models to study pancreas cancer pathogenesis and exocrine cell plasticity.

Pharmacological inhibition and reversal of pancreatic acinar ductal metaplasia.

Pancreatic acinar cells display a remarkable degree of plasticity and can dedifferentiate into ductal-like progenitor cells by a process known as acinar ductal metaplasia (ADM). ADM is believed to be one of the earliest precursor lesions toward the development of pancreatic ductal adenocarcinoma and maintaining the pancreatic acinar cell phenotype suppresses tumor formation. The effects of a novel pStat3 inhibitor (LLL12B) and the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) were investigated using 3-D cultures from p48Cre/+ and p48Cre/+LSL-KrasG12D/+ (KC) mice. LLL12B and TSA inhibited ADM in both KC and p48Cre/+ mouse pancreatic organoids. Furthermore, treatment with LLL12B or TSA on dedifferentiated acini from p48Cre/+ and KC mice that had undergone ADM produced morphologic and gene expression changes that suggest a reversal of ADM. Validation experiments using qRT-PCR (p48Cre/+ and KC) and RNA sequencing (KC) of the LLL12B and TSA treated cultures showed that the ADM reversal was more robust for the TSA treatments. Pathway analysis showed that TSA inhibited Spink1 and PI3K/AKT signaling during ADM reversal. The ability of TSA to reverse ADM was also observed in primary human acinar cultures. We report that pStat3 and HDAC inhibition can attenuate ADM in vitro and reverse ADM in the context of wild-type Kras. Our findings suggest that pharmacological inhibition or reversal of pancreatic ADM represents a potential therapeutic strategy for blocking aberrant ductal reprogramming of acinar cells.

Enhancing African American Participation in Biospecimens: A Case in Point for Pancreatic Cancer.

Diseases of the pancreas (i.e. chronic pancreatitis, diabetes, and pancreatic cancer) disproportionally affect the African American community. Challenges associated with engaging the African American community in biospecimen research are longstanding. We surveyed a number of pancreas-related biobanks, and data repositories for African American representation. While some of the biobanks and databases surveyed contain biospecimens and data from African American donors at levels that reflect minority representation among the general population, others do not. A number of factors have historically contributed to reduced participation of the African Americans community in biospecimen donation including medical mistrust, lack of transparency, fear, and a poor knowledge and understanding about the use of biospecimens for research. Suggestions for increasing African American participation in organ and biospecimen donation include educational interventions, particularly in community groups, and providing printed and online recruitment materials to patients, patient advocates, and care partners. Increasing awareness of the many benefits of biospecimen donation among African Americans will positively affect health disparities research into pancreatic cancer and other diseases.