Silencing the GUCA2A-GUCY2C tumor suppressor axis in CIN, serrated, and MSI colorectal neoplasia.

Colorectal cancers (CRCs) initiate through distinct mutations, including in APC pathway components leading to tubular adenomas (TAs); in BRAF, with epigenetic silencing of CDX2, leading to serrated adenomas (SAs); and in the DNA mismatch repair machinery driving microsatellite instability (MSI). Transformation through the APC pathway involves loss of the hormone GUCA2A that silences the tumor-suppressing receptor GUCY2C. Indeed, oral hormone replacement is an emerging strategy to reactivate GUCY2C and prevent CRC initiation and progression. Moreover, retained expression by tumors arising from TAs has established GUCY2C as a diagnostic and therapeutic target to prevent and treat metastatic CRC. Here, we defined the potential role of the GUCA2A-GUCY2C axis and its suitability as a target in tumors arising through the SA and MSI pathways. GUCA2A hormone expression was eliminated in TAs, SAs, and MSI tumors compared to their corresponding normal adjacent tissues. In contrast to the hormone, the tumor-suppressing receptor GUCY2C was retained in TA and MSI tumors. Surprisingly, GUCY2C expression was nearly eliminated in SAs, reflecting loss of the transcription factor CDX2. Changes in the GUCA2A-GUCY2C axis in human SAs and MSI tumors were precisely recapitulated in genetic mouse models. These data reveal the possibility of GUCA2A loss silencing GUCY2C in the pathophysiology of, and oral hormone replacement to restore GUCY2C signaling to prevent, MSI tumors. Also, they highlight the potential for targeting GUCY2C to prevent and treat metastases arising from TA and MSI tumors. In contrast, loss of GUCY2C excludes patients with SAs as candidates for GUCY2C-based prevention and therapy

Discordant Responses Between Primary Head and Neck Tumors and Nodal Metastases Treated With Neoadjuvant Nivolumab: Correlation of Radiographic and Pathologic Treatment Effect.

PD-1 blockade represents a promising treatment in patients with head and neck squamous cell carcinoma (HNSCC). We analyzed results of a neoadjuvant randomized window-of-opportunity trial of nivolumab plus/minus tadalafil to investigate whether immunotherapy-mediated treatment effects vary by site of involvement (primary tumor, lymph nodes) and determine how radiographic tumor shrinkage correlates with pathologic treatment effect. Patients and Methods: Forty-four patients enrolled in trial NCT03238365 were treated with nivolumab 240 mg intravenously on days 1 and 15 with or without oral tadalafil, as determined by random assignment, followed by surgery on day 31. Radiographic volumetric response (RVR) was defined as percent change in tumor volume from pretreatment to posttreatment CT scan. Responders were defined as those with a 10% reduction in the volume of the primary tumor or lymph nodes (LN). Pathologic treatment effect (PTE) was defined as the area showing fibrosis or lymphohistiocytic inflammation divided by total tumor area. Results: Sixteen of 32 patients (50%) with pathologic evidence of LN involvement exhibited discordant PTE between primary sites and LN. In four patients with widely discordant adjacent LN, increased PTE was associated with increased infiltration of tumor CD8+ T cells and CD163+ macrophages, whereas stromal regulatory T cells were associated with low nodal PTE. RVR correlated with PTE at both primary tumor (slope = 0.55, p \u3c 0.001) and in LN (slope = 0.62, p \u3c 0.05). 89% (16/18) of radiographic non-responders with T1-T3 primary sites had no (n = 7) or minimal PTE (n = 9), whereas 15/17 (88%) of radiographic responders had moderate (n = 12) or complete (n = 3) PTE. Conclusion: Nivolumab often induces discordant treatment effects between primary tumor sites and metastatic lymph nodes within subjects. This treatment discordance was also demonstrated in adjacent lymph nodes, which may correlate with local immune cell makeup. Finally, although these data were generated by a relatively small population size, our data support the use of early radiographic response to assess immunotherapy treatment effect in HNSCC

Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications

This work was supported by a restricted research grant of Bayer AG

Two Distinct GUCY2C Neuronal Pathways in the Hypothalamus and Midbrain

Obesity is a global pandemic with accelerating trends in morbidity, mortality, and medical expenditures. Treatments have been limited in efficacy, or burdened with safety concerns. In the context of this unmet clinical need for more effective and safe anti-obesity therapies, the recent discovery of a new gut-brain endocrine axis regulating appetite and metabolism offers a unique opportunity to advance treatment and prevention for this disease. The transmembrane receptor guanylate cyclase C (GUCY2C) recently was characterized in dopaminergic neurons of the ventral midbrain, and identified in the hypothalamus. The GUCY2C ligand uroguanylin, made in the intestine, induces satiety, and impaired GUCY2C signaling is associated with hyperphagia and obesity. Moreover, obesity is associated with reduced uroguanylin expression, suggesting a pathophysiological positive feedback loop whereby chronic overnutrition disrupts satiety signaling, leading to further increases in food intake. The following work describes advances in the understanding of the uroguanylin-GUCY2C gut-brain neuroendocrine axis, both in normal physiology as well as in the context of obesity. In chapter 2, we reveal that chronic overnutrition is associated with endoplasmic reticulum (ER) stress in the intestine, and that this ER stress underlies the loss of intestinal uroguanylin expression in obesity. Moreover, we reveal that intestinal uroguanylin loss is reversible if ER stress is alleviated, either pharmacologically or via caloric restriction. Finally, we demonstrate that GUCY2C is present in multiple hypothalamic nuclei, is upregulated and hyper-responsive in obesity, and can be targeted by GUCY2C ligand to reduce weight gain in mice exposed to high fat diet. Together, these findings demonstrate that GUCY2C may serve as a valuable therapeutic target in the treatment of obesity, particularly in patients with reduced circulating uroguanylin. Chapter 3 further investigates the normal physiology of GUCY2C in the central nervous system, mapping GUCY2C expression throughout the brain. This work demonstrates that two discrete pools of neurons in the brain are responsible for widespread GUCY2C protein expression throughout the brain, including the striatum, amygdala, and septal nuclei, as well as numerous hypothalamic nuclei. These two neuronal populations are comprised of GUCY2C+, TH+ dopaminergic neurons of the ventral midbrain, and GUCY2C+, TH–, neurons in the ventral premammillary nucleus (PMV) of the hypothalamus, some of which are also LepR+. Moreover, GUCY2C protein is expressed in distal neuronal projections and presynaptic terminals, suggesting a potential role for GUCY2C in modulation of neurotransmission. Finally, this work reveals that GUCY2C is also expressed in the human hypothalamus and midbrain, with patterns of expression similar to mice, suggesting that GUCY2C neurobiology is conserved across species. Together, these studies provide insight into the uroguanylin-GUCY2C gut-brain neuroendocrine axis, and suggest a potential role for GUCY2C in integrating acute intestinal signaling in both homeostatic and hedonic feeding regulation.

Gut-Brain Endocrine Axes in Weight Regulation and Obesity Pharmacotherapy

In recent years, the obesity epidemic has developed into a major health crisis both in the United States as well as throughout the developed world. With current treatments limited to expensive, high-risk surgery and minimally efficacious pharmacotherapy, new therapeutic options are urgently needed to combat this alarming trend. This review focuses on the endogenous gut-brain signaling axes that regulate appetite under physiological conditions, and discusses their clinical relevance by summarizing the clinical and preclinical studies that have investigated manipulation of these pathways to treat obesity