Organ-specific distribution of AP-1 in AP-1 luciferase transgenic mice during the maturation process

Inhibition of UV-Induced Stress Signaling and Inflammatory Responses in SKH-1 Mouse Skin by Topical Small-Molecule PD-L1 Blockade

The immune checkpoint ligand PD-L1 has emerged as a molecular target for skin cancer therapy and might also hold promise for preventive intervention targeting solar UV light-induced skin damage. In this study, we have explored the role of PD-L1 in acute keratinocytic photodamage testing the effects of small-molecule pharmacological inhibition. Epidermal PD-L1 upregulation in response to chronic photodamage was established using immunohistochemical and proteomic analyses of a human skin cohort, consistent with earlier observations that PD-L1 is upregulated in cutaneous squamous cell carcinoma. Topical application of the small-molecule PD-L1 inhibitor BMS-202 significantly attenuated UV-induced activator protein-1 transcriptional activity in SKH-1 bioluminescent reporter mouse skin, also confirmed in human HaCaT reporter keratinocytes. RT-qPCR analysis revealed that BMS-202 antagonized UV induction of inflammatory gene expression. Likewise, UV-induced cleavage of procaspase-3, a hallmark of acute skin photodamage, was attenuated by topical BMS-202. NanoString nCounter transcriptomic analysis confirmed downregulation of cutaneous innate immunity- and inflammation-related responses, together with upregulation of immune response pathway gene expression. Further mechanistic analysis confirmed that BMS-202 antagonizes UV-induced PD-L1 expression both at the mRNA and protein levels in SKH-1 epidermis. These data suggest that topical pharmacological PD-L1 antagonism using BMS-202 shows promise for skin protection against photodamage.

Spotlight on the role of COP1 in tumorigenesis

COP1 is an E3 ubiquitin ligase that is involved in the ubiquitylation of various protein substrates to trigger their proteasomal degradation. Although originally identified in a light signalling pathway in plants, biochemical studies have identified putative targets of mammalian COP1 with relevant roles in tumorigenesis, including the oncoproteins JUN and ETV family members, as well as the p53 tumour suppressor. Recent genetic studies have shown that COP1 deficiency leads to spontaneous tumour formation in mice, and have identified mutations in COP1 and its substrates in various human cancers. These findings add to our growing appreciation of the roles for E3 ligases in cancer.

Active transport of bile acids decreases mucin 2 in neonatal ileum: implications for development of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency of premature infants, but its etiology remains unclear. We have previously shown that mucin 2 (Muc2) positive goblet cells are significantly decreased in NEC. We have also shown that ileal bile acids (BAs) are significantly increased during the development of this disease. Because BAs can affect mucins, we hypothesized that elevated ileal BAs contribute to decreased Muc2 in experimental NEC. The role of Muc2 in NEC was evaluated in Winnie +/+ mice, a strain that produces aberrant Muc2. Muc2 and trefoil factor 3 (Tff3) were assessed in neonatal rats subjected to the NEC protocol when bile acids were removed, and in ileal explants from newborn and older rats cultured with and without BAs. Further, the role of active transport of BAs was determined using neonatal rats given the apical sodium dependent bile acid transporter (Asbt) inhibitor SC-435 and in neonatal Asbt knockout mice subjected to the NEC protocol. Mice with aberrant Muc2 had significantly greater incidence and severity of NEC. Using both in vivo and ex vivo techniques, we determined that BAs decrease Muc2 positive cells in neonatal but not older ileum. However, Tff3 positive cells are not decreased by BAs. In addition, active transport of BAs is required for BAs to decrease Muc2 in immature ileum. These data show that functional Muc2 plays a critical role in the prevention of NEC and BAs can potentiate the decreased Muc2 in disease development. Further, BAs have a more profound effect on Muc2 in immature versus older ileum, which may explain at least in part why NEC occurs almost exclusively in premature infants.

Cop1 constitutively regulates c-Jun protein stability and functions as a tumor suppressor in mice

Biochemical studies have suggested conflicting roles for the E3 ubiquitin ligase constitutive photomorphogenesis protein 1 (Cop1; also known as Rfwd2) in tumorigenesis, providing evidence for both the oncoprotein c-Jun and the tumor suppressor p53 as its targets. Here we present what we believe to be the first in vivo investigation of the role of Cop1 in cancer etiology. Using an innovative genetic approach to generate an allelic series of Cop1, we found that Cop1 hypomorphic mice spontaneously developed malignancy at a high frequency in the first year of life and were highly susceptible to radiation-induced lymphomagenesis. Further analysis revealed that c-Jun was a key physiological target for Cop1 and that Cop1 constitutively kept c-Jun at low levels in vivo and thereby modulated c-Jun/AP-1 transcriptional activity. Importantly, Cop1 deficiency stimulated cell proliferation in a c-Jun-dependent manner. Focal deletions of COP1 were observed at significant frequency across several cancer types, and COP1 loss was determined to be one of the mechanisms leading to c-Jun upregulation in human cancer. We therefore conclude that Cop1 is a tumor suppressor that functions, at least in part, by antagonizing c-Jun oncogenic activity. In the absence of evidence for a genetic interaction between Cop1 and p53, our data strongly argue against the use of Cop1-inhibitory drugs for cancer therapy.

Transient receptor potential type vanilloid 1 suppresses skin carcinogenesis

Blockade of the transient receptor potential channel vanilloid subfamily 1 (TRPV1) is suggested as a therapeutic approach to pain relief. However, TRPV1 is a widely expressed protein whose function might be critical in various nonneuronal physiologic conditions. The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is overexpressed in many human epithelial cancers and is a potential target for anticancer drugs. Here, we show that TRPV1 interacts with EGFR, leading to EGFR degradation. Notably, the absence of TRPV1 in mice results in a striking increase in skin carcinogenesis. The TRPV1 is the first membrane receptor shown to have a tumor-suppressing effect associated with the down-regulation of another membrane receptor. The data suggest that, although a great deal of interest has focused on TRPV1 as a target for pain relief, the chronic blockade of this pain receptor might increase the risk for cancer development.

The anti-apoptotic and growth stimulatory actions of leptin in human colon cancer cells involves activation of JNK mitogen activated protein kinase, JAK2 and PI3 kinase/Akt

BACKGROUND AND AIMS

Obesity is a major risk factor for the development of colon cancer. Secretion of the hormone leptin from adipocytes is increased in obesity, and serum levels are proportional to body fat mass. Serum leptin levels are an independent risk factor for colon cancer. Leptin receptors are expressed in normal, premalignant and malignant colonic epithelia. We have investigated the effects of leptin on proliferation and apoptosis of colonic cancer cells and the early signalling events involved.

METHODS

Proliferation of HT-29 colon cancer cells in response to leptin was assessed by 3-[4, 5-dimethylthiazol-2-y-l]-2, 5-diphenyltetrazolium bromide (MTT) assay, and apoptosis was quantified by enzyme-linked immunosorbent assay (ELISA) for intracellular nucleosomes. Signalling pathways involved were determined by using specific inhibitors, quantification of phosphorylated active intermediates and ELISA of active nuclear-translocated transcription factors.

RESULTS

Leptin stimulated HT-29 cell proliferation and inhibited both serum-starvation and celecoxib-induced apoptosis. The proliferative and anti-apoptotic effects of leptin were abolished by inhibition of JAK2 with AG490, phosphatidylinositol 3'-kinase (PI3 kinase) with LY294002 and c-Jun NH(2)-terminal kinase (JNK) with SP600125. Stimulation of HT-29 cells with leptin increased phosphorylation of JAK2, Akt and JNK. Activation of JAK2 was upstream of PI3 kinase/Akt but not of JNK. Activation of JAK2 was followed by activation and nuclear translocation of STAT3 and JNK activation led to increased activator protein 1 (AP-1) transcriptional activity.

CONCLUSIONS

Leptin stimulates proliferation and inhibits apoptosis in human colon cancer cells and may be an important factor in the increased incidence of colon cancer in obesity. This effect involves JAK2, PI3 kinase and JNK and activation of the oncogenic transcription factors signal transducer and activator of transcription (STAT)3 and AP-1.

Precision-cut tissue slices from transgenic mice as an in vitro toxicology system

In these experiments precision-cut tissue slices from two existing transgenic mouse strains, with transgenes that couple promoting or binding elements to a reporter protein, were used for determination of reporter induction. This approach combines the power of transgenic animals with the practicality of in vitro systems to investigate the biological impact of xenobiotics. Additionally, the normal cellular architecture and heterogeneity is retained in precision-cut tissue slices. Two transgenic mouse strains, one of which couples the promoting region of CYP 1A1 to beta-galactosidase, and another which couples two forward and two backward 12-O-tetradecanoyl phorbol-13-acetate (TPA) repeat elements (TRE) to luciferase (termed AP-1/luciferase), were used to determine the feasibility of this approach. Precision-cut kidney and liver slices from both transgenic strains remain viable as determined by slice K(+) ion content and LDH enzyme release. Liver slices harvested from the CYP 1A1/beta-galactosidase transgenic mice exhibit a 14-fold increase in beta-galactosidase activity when incubated with beta-napthoflavone for 24 h. Kidney and liver slices obtained from the AP-1/luciferase transgenic mice demonstrate induction of luciferase (up to 2.5-fold) when incubated with phorbol myristate acetate (PMA or TPA) up to 4 h. These data indicate that precision-cut tissue slices from transgenic mice offer a novel in vitro method for toxicity evaluation while maintaining normal cell heterogeneity.