Elevated Protein Kinase A Activity in Stomach Mesenchyme Disrupts Mesenchymal-epithelial Crosstalk and Induces Preneoplasia

BACKGROUND & AIMS

Mesenchymal-epithelial crosstalk (MEC) in the stomach is executed by pathways such as bone morphogenetic protein (BMP) and extracellular signal-regulated kinase (ERK). Mis-regulation of MEC disrupts gastric homeostasis and causes tumorigenesis. Protein Kinase A (PKA) crosstalks with BMP and ERK signaling; however, PKA function(s) in stomach development and homeostasis remains undefined.

METHODS

We generated a novel Six2-Cre^+/-PKAcαR^fl/wt (CA-PKA) mouse in which expression of constitutive-active PKAcαR was induced in gastric mesenchyme progenitors. Lineage tracing determined spatiotemporal activity of Six2-Cre in the stomach. For phenotyping CA-PKA mice histological, co-immunofluorescence, immunoblotting, mRNA sequencing, and bioinformatics analyses were performed.

RESULTS

Lineage tracing showed that Six2-Cre activity in the stomach is restricted to the mesenchymal compartment. CA-PKA mice showed disruption of gastric homeostasis characterized by aberrant mucosal development and epithelial hyperproliferation; ultimately developing multiple features of gastric corpus preneoplasia including decreased parietal cells, mucous cell hyperplasia, spasmolytic peptide expressing metaplasia with intestinal characteristics, and dysplastic and invasive cystic glands. Furthermore, mutant corpus showed marked chronic inflammation characterized by infiltration of lymphocytes and myeloid-derived suppressor cells along with the upregulation of innate and adaptive immune system components. Striking upregulation of inflammatory mediators and STAT3 activation was observed. Mechanistically, we determined there is an activation of ERK1/2 and downregulation of BMP/SMAD signaling characterized by marked upregulation of BMP inhibitor gremlin 1.

CONCLUSIONS

We report a novel role of PKA signaling in gastric MEC execution and show that PKA activation in the gastric mesenchyme drives preneoplasia by creating a proinflammatory and proproliferative microenvironment associated with the downregulation of BMP/SMAD signaling and activation of ERK1/2.

Lessons Learned from ToxMSDT: A Pilot Innovative Toxicology Research Education Pipeline Program Targeting Underrepresented Undergraduate Students to the Field of Toxicology

Toxicology, as a profession, lacks diversity. Undergraduate students, and especially underrepresented students, are not commonly introduced to toxicology at US colleges and universities. The Toxicology Mentoring and Skills Development Training Program (ToxMSDT) seeks to acquaint underrepresented undergraduates enrolled in STEM fields with toxicology fundamentals and skills to aid their entry into graduate programs and, ultimately, careers in toxicology. ToxMSDT is a collaboration among three universities. It is a year-long holistic training and mentoring program comprised of web resources accessible 24/7 and extensive one-to-one mentor-mentee interactions throughout the year. Evaluation of the two-year pilot program shows that students expressed a significant increase in knowledge about toxicology careers, networking with people involved in the field of toxicology, feelings of being part of the toxicology community, and seeing themselves as someone who will study toxicology, compared with their feelings prior to their participation in the ToxMSDT program. Thirty students have completed the ToxMSDT program and all 10 (100%) of those who have graduated have joined graduate school in toxicology or toxicology-related STEM fields. Of the 20 (66.6%) program alumni still enrolled as undergraduates, five (25%) are in the process of applying to graduate programs and medical schools as of August 2019.

Transcriptomic profile analysis of brain inferior colliculus following acute hydrogen sulfide exposure

Hydrogen sulfide (H2S) is a gaseous molecule found naturally in the environment, and as an industrial byproduct, and is known to cause acute death and induces long-term neurological disorders following acute high dose exposures. Currently, there is no drug approved for treatment of acute H2S-induced neurotoxicity and/or neurological sequelae. Lack of a deep understanding of pathogenesis of H2S-induced neurotoxicity has delayed the development of appropriate therapeutic drugs that target H2S-induced neuropathology. RNA sequencing analysis was performed to elucidate the cellular and molecular mechanisms of H2S-induced neurodegeneration, and to identify key molecular elements and pathways that contribute to H2S-induced neurotoxicity. C57BL/6J mice were exposed by whole body inhalation to 700 ppm of H2S for either one day, two consecutive days or 4 consecutive days. Magnetic resonance imaging (MRI) scan analyses showed H2S exposure induced lesions in the inferior colliculus (IC) and thalamus (TH). This mechanistic study focused on the IC. RNA Sequencing analysis revealed that mice exposed once, twice, or 4 times had 283, 193 and 296 differentially expressed genes (DEG), respectively (q-value < 0.05, fold-change> 1.5). Hydrogen sulfide exposure modulated multiple biological pathways including unfolded protein response, neurotransmitters, oxidative stress, hypoxia, calcium signaling, and inflammatory response in the IC. Hydrogen sulfide exposure activated PI3K/Akt and MAPK signaling pathways. Pro-inflammatory cytokines were shown to be potential initiators of the modulated signaling pathways following H2S exposure. Furthermore, microglia were shown to release IL-18 and astrocytes released both IL-1β and IL-18 in response to H2S. This transcriptomic analysis data revealed complex signaling pathways involved in H2S-induced neurotoxicity and may provide important associated mechanistic insights.

Kaiso overexpression promotes intestinal inflammation and potentiates intestinal tumorigenesis in Apc(Min/+) mice

Constitutive Wnt/β-catenin signaling is a key contributor to colorectal cancer (CRC). Although inactivation of the tumor suppressor adenomatous polyposis coli (APC) is recognized as an early event in CRC development, it is the accumulation of multiple subsequent oncogenic insults facilitates malignant transformation. One potential contributor to colorectal carcinogenesis is the POZ-ZF transcription factor Kaiso, whose depletion extends lifespan and delays polyp onset in the widely used Apc(Min/+) mouse model of intestinal cancer. These findings suggested that Kaiso potentiates intestinal tumorigenesis, but this was paradoxical as Kaiso was previously implicated as a negative regulator of Wnt/β-catenin signaling. To resolve Kaiso's role in intestinal tumorigenesis and canonical Wnt signaling, we generated a transgenic mouse model (Kaiso(Tg/+)) expressing an intestinal-specific myc-tagged Kaiso transgene. We then mated Kaiso(Tg/+) and Apc(Min/+) mice to generate Kaiso(Tg/+):Apc(Min/+) mice for further characterization. Kaiso(Tg/+):Apc(Min/+) mice exhibited reduced lifespan and increased polyp multiplicity compared to Apc(Min/+) mice. Consistent with this murine phenotype, we found increased Kaiso expression in human CRC tissue, supporting a role for Kaiso in human CRC. Interestingly, Wnt target gene expression was increased in Kaiso(Tg/+):Apc(Min/+) mice, suggesting that Kaiso's function as a negative regulator of canonical Wnt signaling, as seen in Xenopus, is not maintained in this context. Notably, Kaiso(Tg/+):Apc(Min/+) mice exhibited increased inflammation and activation of NFκB signaling compared to their Apc(Min/+) counterparts. This phenotype was consistent with our previous report that Kaiso(Tg/+) mice exhibit chronic intestinal inflammation. Together our findings highlight a role for Kaiso in promoting Wnt signaling, inflammation and tumorigenesis in the mammalian intestine.

3-(2-Bromoethyl)-indole inhibits the growth of cancer cells and NF-κB activation

Indole-3-carbinol (I3C) and diindolylmethane (DIM), found in cruciferous vegetables, have chemopreventive and anticancer properties. In the present study, 14 substituted indoles were tested for activity against SW480 colon cancer cells. Among these, 3-(2-bromoethyl)-indole, named BEI-9, showed the greatest inhibition. The effects of BEI-9 on cancer cells were analyzed by MTS and CellTiter-Glo assays for effects on cell viability, by microscopy for phenotypic changes, by scratch wound assays for effects on migration, by flow cytometry for changes in the cell cycle, by immunoblotting for cyclin D and A to assess effects on cell cycle regulation, and by NF-κB reporter assays for effects on basal and drug-induced NF-κB activation. BEI-9 inhibited the growth of SW480 and HCT116 colon cancer cells at concentrations of 12.5 and 5 µM, respectively. BEI-9 also inhibited cell motility as determined with scratch wound assays, and reduced the levels of cyclin D1 and A. Furthermore, in reporter cells, BEI-9 (0.8 µM) inhibited basal and induced NF-κB activation and increased cell death when combined with the cytokine TNFα or the drug camptothecin (CPT), both of which activate NF-κB. Preliminary experiments to identify a safe dose range for immunodeficient mice showed that BEI-9, administered intraperitoneally, was tolerable at doses below 10 mg/kg. Thus, BEI-9 and other indole derivatives may be useful in chemoprevention or as chemosensitizers. Since NF-κB activation is implicated in carcinogenesis and in reducing sensitivity to anticancer drugs, BEI-9 should be investigated in combination with drugs such as CPT, which activate NF-κB.

Immunohistochemical Detection of CD34, E-cadherin, Claudin-1, Glucose Transporter 1, Laminin, and Protein Gene Product 9.5 in 28 Canine and 8 Feline Meningiomas

The variation in histologic pattern of meningiomas can make their diagnosis challenging. The immunohistochemical profile of 28 canine and 8 feline meningiomas was examined. Tumor types included anaplastic (6 dogs), angiomatoid (1 cat), fibroblastic (3 dogs, 1 cat), meningothelial (1 dog), microcystic (2 dogs), myxoid (3 dogs), psammomatous (4 cats), and transitional (13 dogs, 2 cats). The authors compared the expression of novel markers (CD34, E-cadherin, claudin-1, glucose transporter 1 [GLUT-1], laminin, and protein gene product [PGP] 9.5) with published markers (cytokeratins, glial fibrillary acidic protein [GFAP], progesterone receptor, S100, and vimentin). Neoplastic cells were immunohistochemically positive for vimentin in 100% of the meningiomas; CD34, 94%; GLUT-1, 86%; E-cadherin, 81%; S100, 75%; laminin, 72%; claudin-1, 60%; PGP 9.5, 55%; progesterone receptor, 44%; pancytokeratins, 39%; cytokeratins 8/18, 17%, and GFAP in 9%. Ki67 index did not correlate well with mitotic index. Based on these results and those in the human literature, immunohistochemistry for vimentin, CD34, and E-cadherin is proposed to support a diagnosis of meningioma. Immunohistochemistry for claudin-1, albeit of only moderate to low sensitivity in canine and feline meningiomas, may help to distinguish meningioma from some mesenchymal neoplasms involving the brain and associated structures, such as schwannomas, which in humans express claudin-1 poorly or not at all. Further studies with CD34, E-cadherin, and claudin-1 in canine and feline tumors that may mimic meningiomas are needed to determine the adequacy of this approach.