Antiproliferative Effects and Mechanisms of Liver X Receptor Ligands in Pancreatic Ductal Adenocarcinoma Cells

<div><p>Pancreatic ductal adenocarcinoma (PDAC) is difficult to detect early and is often resistant to standard chemotherapeutic options, contributing to extremely poor disease outcomes. Members of the nuclear receptor superfamily carry out essential biological functions such as hormone signaling and are successfully targeted in the treatment of endocrine-related malignancies. Liver X receptors (LXRs) are nuclear receptors that regulate cholesterol homeostasis, lipid metabolism, and inflammation, and LXR agonists have been developed to regulate LXR function in these processes. Intriguingly, these compounds also exhibit antiproliferative activity in diverse types of cancer cells. In this study, LXR agonist treatments disrupted proliferation, cell-cycle progression, and colony-formation of PDAC cells. At the molecular level, treatments downregulated expression of proteins involved in cell cycle progression and growth factor signaling. Microarray experiments further revealed changes in expression profiles of multiple gene networks involved in biological processes and pathways essential for cell growth and proliferation following LXR activation. These results establish the antiproliferative effects of LXR agonists and potential mechanisms of action in PDAC cells and provide evidence for their potential application in the prevention and treatment of PDAC.</p></div

GW 3965 downregulates oncogenes involved in cancer progression.

<p>A, GW3965 treatment downregulates SKP2 and EGFR protein levels in BxPC-3 and MIA-PaCa-2 cells. Downregulation of EGFR was concomitant with a downregulation of its own phosphorylation in BxPC-3 and MIA-PaCa-2 at 5 uM GW 3965. ERK1/2 and its phosphorylation were not statistically different in any of the cell lines B, C, D Densitometric quantification of SKP2, EGFR, Phospho-EGFR, ERK1/2, and Phospho-ERK1/2 upon treatment with GW3965. Samples were normalized to actin controls. Asterisks indicated statistically significant changes.</p

LXR agonists block cell proliferation and colony-formation in pancreatic cancer cells.

<p>A, B, C, PDAC cells (BxPC-3, Mia-PaCa-2, and PANC-1 cell lines, respectively) show dose-dependent decreases in cell proliferation upon treatment with increasing GW3965 concentrations. EC50 calculations indicate that BxPC-3 and Mia-PaCa-2 cells are more sensitive to ligand treatment than PANC-1 cells. D, Results from MTS assays, a separate measure of overall cell metabolic rate and indirect measurement of cell proliferation, demonstrate a dose-dependent drop in overall metabolism in cells treated with increasing concentrations of GW3965. E, Colony-formation ability in all three cell lines was blocked by GW3965 treatment. F, Colony formation of GW3965 treated cells was quantified relative to vehicle-treated controls. Asterisks indicated statistically significant changes.</p

Microarray analysis of pancreatic cancer cell lines treated with LXR ligands defines common and cell line-specific effects on gene networks.

<p>A, B, Venn diagrams of up-regulated and down-regulated genes (1.1 fold change cutoff) after treatment with GW 3965 for 72 hours. These cell lines show common and cell-line specific transcriptomic responses to ligand treatment. C, Microarray analysis of up-regulated genes show that all cell lines share up-regulation of lipid metabolic, glucose metabolic, and cell proliferation responses. All cell lines down-regulate pathways that regulate response to viral infection, transmembrane support, as well as viral mRNA transcription. Treatments of BxPC-3 and PANC-1 cells down-regulate the expression of genes involved in cell cycle and DNA replication machinery.</p

Knockdown of LXRβ expression block PDAC cell proliferation and response to LXR ligand treatment.

<p>A, Knockdown of LXRα and LXRβ expression was validated by quantitative PCR. Expression data were normalized to 36B4 ribosomal gene transcript levels. B, The effect of LXR knockdown on PDAC cell proliferation was quantified by cell counts following trypan blue exclusion assays. Asterisks indicated statistically significant changes.</p

COVID-19 Host Genetics Initiative. A first update on mapping the human genetic architecture of COVID-19

The COVID-19 pandemic continues to pose a major public health threat, especially in countries with low vaccination rates. To better understand the biological underpinnings of SARS-CoV-2 infection and COVID-19 severity, we formed the COVID-19 Host Genetics Initiative1. Here we present a genome-wide association study meta-analysis of up to 125,584 cases and over 2.5 million control individuals across 60 studies from 25 countries, adding 11 genome-wide significant loci compared with those previously identified2. Genes at new loci, including SFTPD, MUC5B and ACE2, reveal compelling insights regarding disease susceptibility and severity.</p