First-in-human phase 1 study of ETC-159 an oral PORCN inhbitor in patients with advanced solid tumours

2584

Background: The Wnt signalling pathway is involved in cellular proliferation, differentiation, migration and implicated in stem cell function in several cancers. ETC-159 is a selective small molecule inhibitor of porcupine, an enzyme required for palmitoylation and secretion of all Wnt ligands. In preclinical studies, ETC-159 induced tumour regression in patient-derived xenograft models. Methods: Open-label, multi-centre study to determine safety, maximum tolerated dose, pharmacokinetics, pharmacodynamics (PD) of ETC-159 given orally, once every other day in a 28d cycle. PD was evaluated by AXIN2 mRNA levels in whole blood and hair follicles and bone turnover by radiological and serum markers. Dose escalation was by ordinal continual reassessment method with a dose-limiting toxicity (DLT) period of 28d. Results: As of 18 Jan 2017, 16 patients (pts) were treated in 6 cohorts at 1 mg (2pts), 2 mg (2pts), 4 mg (3pts), 8 mg (4pts); 16 mg (3pts), and 30 mg (2pts). 80% were male, median age (range) was 55yr (19-68). One DLT was seen at 16 mg due to hyperbilirubinaemia. Adverse events (≥ 20%) were vomiting (32%); anorexia and fatigue (31%); dysgeusia and constipation (25%). ETC-159 Cmax increased with dose with a mean t1/2 of 14 hr. Plasma levels of ETC-159 that inhibited colony formation in vitro were attained from 4 mg onwards. Reduction of whole blood and hair follicle AXIN2 mRNA levels and doubling of serum β-CTX levels was first observed at 4 mg and at C1D15 in some patients. PD modulation increased with dose, consistent with on-target modulation of Wnt signalling. Two pts had β-CTX rise > 1000 pg/mL (reference limit) and a ≥ 5% reduction in bone density by C3D1. Both took vitamin D and calcium supplements and were given i.v. bisphosphonates. No responses were seen but 2 pts (2 mg: colorectal and 4 mg: peritoneal carcinoma) had stable disease for 6 and 8 cycles respectively. Dose-escalation is ongoing at 30 mg. Conclusions: ETC-159 inhibits Wnt signalling at doses that are well tolerated. β-CTX levels increased early on, and in two pts were associated with reduced bone mineral density. Early and regular monitoring of bone turnover is indicated. This study was sponsored by D3 which is funded by NMRC, NRF and BMRC Singapore. Clinical trial information: NCT02521844.

Wnt inhibition enhances browning of mouse primary white adipocytes

The global epidemic in obesity and metabolic syndrome requires novel approaches to tackle. White adipose tissue, traditionally seen as a passive energy-storage organ, can be induced to take on certain characteristics of brown fat in a process called browning. The “browned” white adipose tissue, or beige fat, is a potential anti-obesity target. Various signaling pathways can enhance browning. Wnt is a key regulator of adipocyte biology, but its role in browning has not been explored. In this study, we found that in primary mouse adipocytes derived from the inguinal depot, Wnt inhibition by both chemical and genetic methods significantly enhanced browning. The effect of Wnt inhibition on browning most likely targets the beige precursor cells in selected adipose depots.

Abstract A30: Frizzled-7 (FZD7)-mediated non-canonical Wnt-Planar Cell Polarity (PCP) signalling pathway as a novel molecular driver for the C5/Proliferative/Stem-A molecular subtype of ovarian cancer

Ovarian cancer (OC), in particular high grade serous carcinoma (HGSC), has been shown to exhibit diverse molecular heterogeneity based on gene expression profiling by the Australian and the TCGA cohorts. This molecular heterogeneity has been demonstrated to be very robust and reproducible by a large-scale meta-analysis study consisting of 1,538 samples from our group. At least 5 distinct gene-expression based molecular subtypes (GEMS) of EOC have been identified. The C5 subtype from the Tothill dataset corresponds to the Proliferative subtype from the TCGA dataset and the Stem-A subtype from the 1,538 meta-analysis dataset. These GEMS have been correlated with patient survival. The C5/Proliferative/Stem-A GEMS is associated with poorer survival outcomes. From our own study, Stem-A OC cells tend to display preferential chemosensitivity towards microtubule depolymerizing agents affecting the plus-end dynamics of microtubule such as vincristine and vinorelbine. Interestingly, Stem-A as well as non-Stem-A cells are equally sensitive to microtubule stabilizing agents such as paclitaxel. The biology of this C5/Proliferative/Stem-A-subtyped OC is still elusive and requires in-depth study. Here, we demonstrate that a Wnt receptor Frizzled-7 (FZD7) is crucial for the aggressiveness of the C5/Proliferative/Stem-A GEMS. Silencing FZD7 in the Stem-A-subtyped OC induces decrease in cell proliferation and cell cycle arrest. Silencing FZD7 also induced compaction of OC cell colony and strengthening of actin cytoskeleton at cell-cell junctions. Stable FZD7 knockdown clones further demonstrate significant decrease in anoikis resistance, spheroid forming ability, and tumorigenesis in xenografts. We further show that these functional changes acts via the Wnt-planar cell polarity (PCP) pathway downstream of FZD7. A subset of PCP pathway genes is also enriched in Stem-A tumors. Transient silencing of three downstream PCP pathway genes, CELSR3, PRICKLE4, PTK7, gave rise to similar functional phenotypes as silencing FZD7. These FZD7-PCP silenced Stem-A OC cells also demonstrate enhanced sensitivity to the microtubule depolymerizing agent vinorelbine. We conclude that the FZD7-PCP pathway drives the aggressiveness of the C5/Proliferative/Stem-A-subtyped OC and can be potentially utilized as the marker to identify the Stem-A subgroup. Molecularly stratifying OC patients and targeting C5/Proliferative/Stem-A subtype with therapeutics against FZD7-PCP pathway would be a novel strategy for OC.

Citation Format: Mohammad Asad, Meng Kang Wong, Tuan Zea Tan, David Virshup, Jean Paul Thiery, Ruby Yun-Ju Huang. Frizzled-7 (FZD7)-mediated non-canonical Wnt-Planar Cell Polarity (PCP) signalling pathway as a novel molecular driver for the C5/Proliferative/Stem-A molecular subtype of ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr A30.

Abstract 5278: Superoxide mediated selective tyrosine nitration of protein phosphatase 2A-B56δ stabilizes Bcl-2 phosphorylation and its anti-apoptotic activity

Our work over the years has provided strong evidence that an increase in intracellular superoxide anion provides cancer cells with a survival advantage and promotes tumor chemoresistance. The mechanisms underlying superoxide-mediated pro-survival signaling are poorly understood. Here we report that an increase in intracellular superoxide stabilizes the anti-apoptotic activity of Bcl-2 by mechanisms that involve sustained phosphorylation of Bcl-2 at serine 70. Of note, this effect on Bcl-2 S70 phosphorylation is a function of redox-dependent inactivation of Protein Phosphatase 2A (PP2A), which is targeted to Bcl-2 via its B56 subunit; superoxide induces the release of PP2A-AC catalytic core from Bcl-2-bound B56δ, resulting in sustained phosphorylation of Bcl-2 at S70. Dissociation of the PP2A heterotrimer results from the selective nitration (by peroxynitrite derived from the reaction of superoxide with NO) of a conserved tyrosine residue, which we identify as Y289 of B56δ (B56 δY289). Inhibition of B56δY289 nitration blocked the pro-survival effects of superoxide. Furthermore, we provide evidence for clinical relevance of these findings using primary tissue derived from human lymphoma biopsies. Taken together, these data provide evidence for a novel mechanism in which an increase in intracellular superoxide regulates PP2A function via specific B56 subunit tyrosine nitration, and that PP2A-B56 nitration may be a general mechanism for redox-regulated cellular signaling.

Citation Format: Ivan C. C. Low, Thomas Loh, David Virshup, Shazib Pervaiz. Superoxide mediated selective tyrosine nitration of protein phosphatase 2A-B56δ stabilizes Bcl-2 phosphorylation and its anti-apoptotic activity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5278. doi:10.1158/1538-7445.AM2014-5278

FZD7 drives in vitro aggressiveness in Stem-A subtype of ovarian cancer via regulation of non-canonical Wnt/PCP pathway

Ovarian cancer (OC) can be classified into five biologically distinct molecular subgroups: epithelial-A (Epi-A), Epi-B, mesenchymal (Mes), Stem-A and Stem-B. Among them, Stem-A expresses genes relating to stemness and is correlated with poor clinical prognosis. In this study, we show that frizzled family receptor 7 (FZD7), a receptor for Wnt signalling, is overexpressed in the Stem-A subgroup. To elucidate the functional roles of FZD7, we used an RNA interference gene knockdown approach in three Stem-A cell lines: CH1, PA1 and OV-17R. Si-FZD7 OC cells showed reduced cell proliferation with an increase in the G0/G1 sub-population, with no effect on apoptosis. The cells also displayed a distinctive morphologic change by colony compaction to become more epithelial-like and polarised with smaller internuclear distances and increased z-axis height. Immunofluorescence (IF) staining patterns of pan-cadherin and β-catenin suggested an increase in cadherin-based cell–cell adhesion in si-FZD7 cells. We also observed a significant rearrangement in the actin cytoskeleton and an increase in tensile contractility in si-FZD7 OC cells, as evident by the loss of stress fibres and the redistribution of phospho-myosin light chain (pMLC) from the sites of cell–cell contacts to the periphery of cell colonies. Furthermore, there was reciprocal regulation of RhoA (Ras homolog family member A) and Rac1 (Ras-related C3 botulinum toxin substrate 1 (Rho family, small GTP-binding protein Rac1)) activities upon FZD7 knockdown, with a significant reduction in RhoA activity and a concomitant upregulation in Rac1 activity. These changes in pMLC and RhoA, as well as the increased TopFlash reporter activities in si-FZD7 cells, suggested involvement of the non-canonical Wnt/planar cell polarity (PCP) pathway. Selected PCP pathway genes (cadherin EGF LAG seven-pass G-type receptor 3 (CELSR3), prickle homolog 4 (Drosophila) (PRICKLE4), dishevelled-associated activator of morphogenesis 1 (DAAM1), profilin 2 (PFN2), protocadherin 9 (PCDH9), protocadherin α1 (PCDHA1), protocadherin β17 pseudogene (PCDHB17), protocadherin β3 (PCDHB3), sprouty homolog 1 (SPRY1) and protein tyrosine kinase 7 (PTK7)) were found to be more highly expressed in Stem-A than non Stem-A subgroup of OC. Taken together, our results suggest that FZD7 might drive aggressiveness in Stem-A OC by regulating cell proliferation, cell cycle progression, maintenance of the Mes phenotype and cell migration via casein kinase 1ɛ-mediated non-canonical Wnt/PCP pathway.

Protein phosphatase 2A regulates self-renewal of Drosophilaneural stem cells

Drosophila larval brain neural stem cells, also known as neuroblasts, divide asymmetrically to generate a self-renewing neuroblast and a ganglion mother cell (GMC) that divides terminally to produce two differentiated neurons or glia. Failure of asymmetric cell division can result in hyperproliferation of neuroblasts, a phenotype resembling brain tumors. Here we have identified Drosophila Protein phosphatase 2A (PP2A) as a brain tumor-suppressor that can inhibit self-renewal of neuroblasts. Supernumerary larval brain neuroblasts are generated at the expense of differentiated neurons in PP2A mutants. Neuroblast overgrowth was observed in both dorsomedial (DM)/posterior Asense-negative (PAN) neuroblast lineages and non-DM neuroblast lineages. The PP2A heterotrimeric complex,composed of the catalytic subunit (Mts), scaffold subunit (PP2A-29B) and a B-regulatory subunit (Tws), is required for the asymmetric cell division of neuroblasts. The PP2A complex regulates asymmetric localization of Numb, Pon and Atypical protein kinase C, as well as proper mitotic spindle orientation. Interestingly, PP2A and Polo kinase enhance Numb and Pon phosphorylation. PP2A, like Polo, acts to prevent excess neuroblast self-renewal primarily by regulating asymmetric localization and activation of Numb. Reduction of PP2A function in larval brains or S2 cells causes a marked decrease in Polo transcript and protein abundance. Overexpression of Polo or Numb significantly suppresses neuroblast overgrowth in PP2A mutants, suggesting that PP2A inhibits excess neuroblast self-renewal in the Polo/Numb pathway.

Beyond intuitive modeling: combining biophysical models with innovative experiments to move the circadian clock field forward

Two major approaches have been used to model circadian clocks. Qualitative modeling, used prior to the recent wealth of detailed molecular knowledge, makes general predictions but cannot provide detailed mechanistic insights. The more recent biophysical approach, on the other hand, incorporates the biochemical events that drive the clock and can make detailed and testable molecular predictions. These predictions are being tested using new experimental techniques that measure reaction kinetics and the behavior of individual cells. A joint modeling and experimental approach has recently been used to understand how mutations affecting phosphorylation can lead to a short circadian period in tau mutant hamsters and in humans with familial advanced sleep phase syndrome (FASPS). Another recent study has revealed novel single-cell phenotypes of clock gene mutations, demanding revision of current biophysical models yet validating certain model predictions that were previously overlooked. A new paradigm for clock research is emerging in which modeling inspires new experimental efforts, experimental data inspire new modeling efforts, and joint modeling/experimental studies lead to a deeper understanding of mammalian circadian rhythms.

Lineage-specific trisomy 21 in a neonate with resolving transient myeloproliferative syndrome

The cellular events that lead to transient myeloproliferative syndrome (TMS) in patients with trisomy 21 mosaicism confined to the hematopoietic system are poorly understood. The authors attempt to define the event that led to the development of TMS in a single patient with clonal trisomy 21. A phenotypically normal neonate with clonal trisomy 21 is described. At the time when his TMS was resolving, fluorescent in situ hybridization analysis was performed on cell populations sorted by flow cytometry to determine what cell populations contained trisomic cells. Trisomy 21 was found in cells of the erythrocytic and monocytic lineages, but not in the stem cells, progenitor compartment, megakaryocytes, lymphocytes, or neutrophils. These results support the hypothesis that, in this neonate, trisomy 21 occurred in a multipotent hematopoietic progenitor, and a subsequent event led to the appearance of the blast population.

Phosphorylation and destabilization of human period I clock protein by human casein kinase I epsilon

Period (PER), a central component of the circadian clock in Drosophila, undergoes daily oscillation in abundance and phosphorylation state. Here we report that human casein kinase I epsilon (hCKI epsilon) can phosphorylate human PER I (hPER I). Purified recombinant hCKI epsilon (but not a kinase negative mutant of hCKI epsilon, hCKI epsilon-K38R) phosphorylated hPER I in vitro. When co-transfected with wild-type hCKI epsilon, in 293T cells, hPER I showed a significant increase in phosphorylation as evidenced by a shift in molecular mass. Furthermore, phosphorylation of hPER I by hCKI epsilon caused a decrease in protein stability in hPER I. Whereas phosphorylated hPER I had a half-life of approximately 12 h, unphosphorylated hPER I remained stable in the cell for > 24 h. hPER I protein could also be co-immunoprecipitated with transfected hCKI epsilon as well as endogenous hCKI epsilon, indicating physical association between hPER I and hCKI epsilon proteins in vivo.

Linkage of familial Wilms' tumor predisposition to chromosome 19 and a two-locus model for the etiology of familial tumors

Familial predisposition to Wilms' tumor (WT), a childhood kidney tumor, is inherited as an autosomal dominant trait. For most WT families studied, the 11p13 gene WT1 and genomic regions implicated in tumorigenesis in a subset of tumors can be ruled out as the site of the familial predisposition gene. Following a genome-wide genetic linkage scan, we have obtained strong evidence (log of the odds ratio = 4.0) in five families for an inherited WT predisposition gene (FWT2) at 19q13.3-q13.4. In addition, we observed loss of heterozygosity at 19q in tumors from individuals from two families in which 19q can be ruled out as the site of the inherited predisposing mutation. From these data, we hypothesize that alterations at two distinct loci are critical rate-limiting steps in the etiology of familial WTs.

Bepridil and cetiedil. Vasodilators which inhibit Ca2+-dependent calmodulin interactions with erythrocyte membranes

Two new vascular smooth muscle relaxants, bepridil and cetiedil, were found to possess specific CaM-inhibitory properties which resembled those of trifluoperazine. Trifluoperazine, bepridil, and cetiedil inhibited Ca2+-dependent 125I-CaM binding to erythrocyte membranes and CaM activation of membrane Ca2+-ATPase with IC50 values of approximately 12, approximately 17, and approximately 40 microM, respectively. This does not appear to be the result of a nonspecific hydrophobic interaction since inhibition was not observed with micromolar concentrations of many other hydrophobic agents. The predominant inhibition of binding and Ca2+-ATPase activation was competitive with respect to CaM. Bepridil and cetiedil bind directly to CaM since these drugs displaced [3H]trifluoperazine from sites on CaM. Inhibition of Ca2+-ATPase and binding by the drugs was not due to interference with the catalytic activity of this enzyme since: (a) neither inhibition of CaM-independent basal Ca2+-ATPase activity nor inhibition of proteolytically-activated Ca2+-ATPase activities were produced by these agents, and (b) no drug-induced inhibition of CaM binding was detected when membranes were preincubated with these agents but washed prior to addition of 125I-CaM. Thus, bepridil and cetiedil competitively inhibit Ca2+-dependent interactions of CaM with erythrocyte membranes, most likely by a direct interaction between these drugs and CaM. The principal clinical actions of these drugs may be explained by their interactions with CaM or CaM-related proteins leading to reduced activation of Ca2+-regulated enzymes in certain other tissues, such as myosin light chain kinase in vascular smooth muscle.