Muscarinic receptor agonist-induced ßPix binding to ß-catenin promotes colon neoplasia.

M3 muscarinic receptors (M3R) modulate ß-catenin signaling and colon neoplasia. CDC42/RAC guanine nucleotide exchange factor, ßPix, binds to ß-catenin in colon cancer cells, augmenting ß-catenin transcriptional activity. Using in silico, in vitro, and in vivo approaches, we explored whether these actions are regulated by M3R. At the invasive fronts of murine and human colon cancers, we detected co-localized nuclear expression of ßPix and ß-catenin in stem cells overexpressing M3R. Using immunohistochemistry, immunoprecipitation, proximity ligand, and fluorescent cell sorting assays in human tissues and established and primary human colon cancer cell cultures, we detected time-dependent M3R agonist-induced cytoplasmic and nuclear association of ßPix with ß-catenin. ßPix knockdown attenuated M3R agonist-induced human colon cancer cell proliferation, migration, invasion, and expression of PTGS2, the gene encoding cyclooxygenase-2, a key player in colon neoplasia. Overexpressing ßPix dose-dependently augmented ß-catenin binding to the transcription factor TCF4. In a murine model of sporadic colon cancer, advanced neoplasia was attenuated in conditional knockout mice with intestinal epithelial cell deficiency of ßPix. Expression levels of ß-catenin target genes and proteins relevant to colon neoplasia, including c-Myc and Ptgs2, were reduced in colon tumors from ßPix-deficient conditional knockout mice. Targeting the M3R/ßPix/ß-catenin axis may have therapeutic potential.

Potential Role for Combined Subtype-Selective Targeting of M1 and M3 Muscarinic Receptors in Gastrointestinal and Liver Diseases.

Despite structural similarity, the five subtypes comprising the cholinergic muscarinic family of G protein-coupled receptors regulate remarkably diverse biological functions. This mini review focuses on the closely related and commonly co-expressed M1R and M3R muscarinic acetylcholine receptor subtypes encoded respectively by CHRM1 and CHRM3. Activated M1R and M3R signal via Gq and downstream initiate phospholipid turnover, changes in cell calcium levels, and activation of protein kinases that alter gene transcription and ultimately cell function. The unexpectedly divergent effects of M1R and M3R activation, despite similar receptor structure, distribution, and signaling, are puzzling. To explore this conundrum, we focus on the gastrointestinal (GI) tract and liver because abundant data identify opposing effects of M1R and M3R activation on the progression of gastric, pancreatic, and colon cancer, and liver injury and fibrosis. Whereas M3R activation promotes GI neoplasia, M1R activation appears protective. In contrast, in murine liver injury models, M3R activation promotes and M1R activation mitigates liver fibrosis. We analyze these findings critically, consider their therapeutic implications, and review the pharmacology and availability for research and therapeutics of M1R and M3R-selective agonists and antagonists. We conclude by considering gaps in knowledge and other factors that hinder the application of these drugs and the development of new agents to treat GI and liver diseases.

Targeted intestinal deletion of Rho guanine nucleotide exchange factor 7, ßPIX, impairs enterocyte proliferation, villus maturation, and mucosal defenses in mice.

Rho guanine nucleotide exchange factors (RhoGEFs) regulate Rho GTPase activity and cytoskeletal and cell adhesion dynamics. ßPix, a CDC42/RAC family RhoGEF encoded by ARHGEF7, is reported to modulate human colon cancer cell proliferation and postwounding restitution of rat intestinal epithelial monolayers. We hypothesized that ßPix plays a role in maintaining intestinal epithelial homeostasis. To test this hypothesis, we examined ßPix distribution in the human and murine intestine and created mice with intestinal epithelial-selective ßPix deletion [ßPixflox/flox/Tg(villin-Cre); Arhgef7 CKO mice]. Using Arhgef7 conditional knockout (CKO) and control mice, we investigated the consequences of ßPix deficiency in vivo on intestinal epithelial and enteroid development, dextran sodium sulfate-induced mucosal injury, and gut permeability. In normal human and murine intestines, we observed diffuse cytoplasmic and moderate nuclear ßPix immunostaining in enterocytes. Arhgef7 CKO mice were viable and fertile, with normal gross intestinal architecture but reduced small intestinal villus height, villus-to-crypt ratio, and goblet cells; small intestinal crypt cells had reduced Ki67 staining, compatible with impaired cell proliferation. Enteroids derived from control mouse small intestine were viable for more than 20 passages, but those from Arhgef7 CKO mice did not survive beyond 24 h despite addition of Wnt proteins or conditioned media from normal enteroids. Adding a Rho kinase (ROCK) inhibitor partially rescued CKO enteroid development. Compared with littermate control mice, dextran sodium sulfate-treated ßPix-deficient mice lost more weight and had greater impairment of intestinal barrier function, and more severe colonic mucosal injury. These findings reveal ßPix expression is important for enterocyte development, intestinal homeostasis, and resistance to toxic injury.NEW & NOTEWORTHY To explore the role of ßPix, a guanine nucleotide exchange factor encoded by ARHGEF7, in intestinal development and physiology, we created mice with intestinal epithelial cell Arhgef7/ßPix deficiency. We found ßPix essential for normal small intestinal epithelial cell proliferation, villus development, and mucosal resistance to injury. Moreover, Rho kinase signaling mediated developmental arrest observed in enteroids derived from ßPix-deficient small intestinal crypts. Our studies provide insights into the role Arhgef7/ßPix plays in intestinal epithelial homeostasis.

Overcoming Obstacles to Targeting Muscarinic Receptor Signaling in Colorectal Cancer.

Despite great advances in our understanding of the pathobiology of colorectal cancer and the genetic and environmental factors that mitigate its onset and progression, a paucity of effective treatments persists. The five-year survival for advanced, stage IV disease remains substantially less than 20%. This review examines a relatively untapped reservoir of potential therapies to target muscarinic receptor expression, activation, and signaling in colorectal cancer. Most colorectal cancers overexpress M3 muscarinic receptors (M3R), and both in vitro and in vivo studies have shown that activating these receptors stimulates cellular programs that result in colon cancer growth, survival, and spread. In vivo studies using mouse models of intestinal neoplasia have shown that using either genetic or pharmacological approaches to block M3R expression and activation, respectively, attenuates the development and progression of colon cancer. Moreover, both in vitro and in vivo studies have shown that blocking the activity of matrix metalloproteinases (MMPs) that are induced selectively by M3R activation, i.e., MMP1 and MMP7, also impedes colon cancer growth and progression. Nonetheless, the widespread expression of muscarinic receptors and MMPs and their importance for many cellular functions raises important concerns about off-target effects and the safety of employing similar strategies in humans. As we highlight in this review, highly selective approaches can overcome these obstacles and permit clinicians to exploit the reliance of colon cancer cells on muscarinic receptors and their downstream signal transduction pathways for therapeutic purposes.

Proactive Drug Monitoring Is Associated With Higher Persistence to Infliximab and Adalimumab Treatment and Lower Healthcare Utilization Compared With Reactive and Clinical Monitoring.

BACKGROUND: Serum drug-level assays for infliximab (IFX) and adalimumab (ADA) are widely available and are most often obtained reactively, to determine the next steps in patients with loss of response. Studies done thus far on the use of these assays proactively, or during symptom remission, have had mixed results. Here we investigate persistence on therapy and healthcare utilization in patients on 3 drug-level monitoring strategies. METHODS: We conducted a retrospective chart review of 235 patients treated for both Crohn disease and ulcerative colitis on either IFX or ADA. Monitoring strategy was defined as proactive if patients underwent testing at predefined time points regardless of symptoms or signs of disease, reactive if done during relapse, or control if no drug levels were obtained. Groups were compared on persistence on original therapeutic at 1 and 2 years as well as on various measures of healthcare utilization during the 2-year follow-up period. RESULTS: Proactive drug monitoring was associated with a higher likelihood of persistence on therapy at 1 year when compared with the control (odds ratio [OR] = 4.76, 95% confidence interval [CI] = 1.65, 13.67) and reactive groups (OR = 6.10, CI = 2.19, 17.02). Similarly, at 2 years, proactive monitoring was superior to the control (OR = 5.41, CI = 2.26, 12.94) and reactive groups (OR = 4.51, CI = 1.88, 10.80). Proactive monitoring was also associated with lower healthcare utilization across almost all measures related to inflammatory bowel disease. CONCLUSIONS: Proactive drug monitoring increases persistence on IFX and ADA in patients with ulcerative colitis or Crohn disease and decreases overall healthcare utilization in these patients.

The Role of M3 Muscarinic Receptor Ligand-Induced Kinase Signaling in Colon Cancer Progression.

Despite a reduction in incidence over the past decade, colon cancer remains the second most common cause of cancer death in the United States; recent demographics suggest this disease is now afflicting younger persons. M3 muscarinic receptor (M3R) mRNA and protein are over-expressed in colon cancer, and M3R can be activated by both traditional (e.g., acetylcholine) and non-traditional (e.g., bile acids) muscarinic ligands. In this review, we weigh the data supporting a prominent role for key protein kinases downstream of M3R activation in promoting colon cancer progression and dissemination. Specifically, we explore the roles that downstream activation of the mitogen activated protein kinase/extracellular signal-related kinase (MAPK/ERK), protein kinase C, p38 MAPK, and phosphatidylinositol 3-kinase/Akt (PI3K/Akt) pathways play in mediating colon cancer cell proliferation, survival, migration and invasion. We assess the impact of M3R-stimulated induction of selected matrix metalloproteinases germane to these hallmarks of colon cancer progression. In this context, we also critically review the reproducibility of findings derived from a variety of in vivo and in vitro colon cancer models, and their fidelity to human disease. Finally, we summarize the therapeutic potential of targeting various steps from ligand-M3R interaction to the activation of key downstream molecules.