Tankyrase-1 regulates RBP-mediated mRNA turnover to promote muscle fiber formation.

Poly(ADP-ribosylation) (PARylation) is a post-translational modification mediated by a subset of ADP-ribosyl transferases (ARTs). Although PARylation-inhibition based therapies are considered as an avenue to combat debilitating diseases such as cancer and myopathies, the role of this modification in physiological processes such as cell differentiation remains unclear. Here, we show that Tankyrase1 (TNKS1), a PARylating ART, plays a major role in myogenesis, a vital process known to drive muscle fiber formation and regeneration. Although all bona fide PARPs are expressed in muscle cells, experiments using siRNA-mediated knockdown or pharmacological inhibition show that TNKS1 is the enzyme responsible of catalyzing PARylation during myogenesis. Via this activity, TNKS1 controls the turnover of mRNAs encoding myogenic regulatory factors such as nucleophosmin (NPM) and myogenin. TNKS1 mediates these effects by targeting RNA-binding proteins such as Human Antigen R (HuR). HuR harbors a conserved TNKS-binding motif (TBM), the mutation of which not only prevents the association of HuR with TNKS1 and its PARylation, but also precludes HuR from regulating the turnover of NPM and myogenin mRNAs as well as from promoting myogenesis. Therefore, our data uncover a new role for TNKS1 as a key modulator of RBP-mediated post-transcriptional events required for vital processes such as myogenesis.

The anterior gradient homologue 2 (AGR2) co-localises with the glucose-regulated protein 78 (GRP78) in cancer stem cells, and is critical for the survival and drug resistance of recurrent glioblastoma: in situ and in vitro analyses.

BACKGROUND: Glioblastomas (GBs) are characterised as one of the most aggressive primary central nervous system tumours (CNSTs). Single-cell sequencing analysis identified the presence of a highly heterogeneous population of cancer stem cells (CSCs). The proteins anterior gradient homologue 2 (AGR2) and glucose-regulated protein 78 (GRP78) are known to play critical roles in regulating unfolded protein response (UPR) machinery. The UPR machinery influences cell survival, migration, invasion and drug resistance. Hence, we investigated the role of AGR2 in drug-resistant recurrent glioblastoma cells. METHODS: Immunofluorescence, biological assessments and whole exome sequencing analyses were completed under in situ and in vitro conditions. Cells were treated with CNSTs clinical/preclinical drugs taxol, cisplatin, irinotecan, MCK8866, etoposide, and temozolomide, then resistant cells were analysed for the expression of AGR2. AGR2 was repressed using single and double siRNA transfections and combined with either temozolomide or irinotecan. RESULTS: Genomic and biological characterisations of the AGR2-expressed Jed66_GB and Jed41_GB recurrent glioblastoma tissues and cell lines showed features consistent with glioblastoma. Immunofluorescence data indicated that AGR2 co-localised with the UPR marker GRP78 in both the tissue and their corresponding primary cell lines. AGR2 and GRP78 were highly expressed in glioblastoma CSCs. Following treatment with the aforementioned drugs, all drug-surviving cells showed high expression of AGR2. Prolonged siRNA repression of a particular region in AGR2 exon 2 reduced AGR2 protein expression and led to lower cell densities in both cell lines. Co-treatments using AGR2 exon 2B siRNA in conjunction with temozolomide or irinotecan had partially synergistic effects. The slight reduction of AGR2 expression increased nuclear Caspase-3 activation in both cell lines and caused multinucleation in the Jed66_GB cell line. CONCLUSIONS: AGR2 is highly expressed in UPR-active CSCs and drug-resistant GB cells, and its repression leads to apoptosis, via multiple pathways.

A paediatric dysembryoplastic neuroepithelial tumour (DNET) with deregulated stem cell markers: a case report.

Background: Dysembryoplastic neuroepithelial tumours (DNETs) are rare, with only a few reported lethal cases. Currently, there are focused efforts by neuro-oncology professionals to reveal the molecular characterisations of individual central nervous system tumours (CNSTs). Here, we report the status of cancer stem cell (CSC) genes associated with resilience and drug resistance in a paediatric DNET, since the deregulations and variations of CSC genes may prove critical to these tumours' molecular characterisations. Case Description: Immunofluorescence, clonogenic assay and whole exome sequencing (WES) were applied to the patient's tissue and its corresponding cell line. The case is for of a 6-year-old boy with intractable epilepsy and unremarkable physical and neurological examinations. Following magnetic resonance imaging (MRI) and histopathological tests, the patient was diagnosed with DNET. The child underwent a right posterior temporoparietooccipital neuronavigation-assisted craniotomy. Several CSC markers were upregulated in situ, including the metastasis-related protein, anterior gradient 2 (AGR2; 67%), and the Wnt-signalling-related protein, frizzled class receptor 9 (FZD9; 79%). The cell line possessed a similar DNA profile as the original tissue, stained positive for the tumorigenic marker [BMI1 proto-oncogene (BMI)] and CSC markers, and displayed drug resistance. Variants identified in the tissue DNA, which are listed in the catalogue of somatic mutations in cancer (COSMIC) database for genes previously known to be necessary for the development of the embryonic brain, included variants in the cell division cycle 27 (CDC27) gene. Conclusions: we report the in situ and in vitro presence of CSCs in a paediatric DNET.

Colossolactone-G synergizes the anticancer properties of 5-fluorouracil and gemcitabine against colorectal cancer cells.

Several terpenoids were isolated from Ganoderma colossum with potential chemotherapeutic properties against different solid tumor cells. Herein, we further assessed the potential chemomodulatory effects of colossolactone-G to gemcitabine (GCB) and 5-fluorouracil (5-FU) against colorectal cancer cells. Colossolactone-G induced moderate cell killing effects against both HT-29 and HCT-116 cells, with IC50's of 90.5 ± 1.7 µM and 22.3 ± 3.9 µM, respectively. Equitoxic combination demonstrated a synergistic effect between colossolactone-G and GCB, or 5-FU with combination indices ranging from 0.22 to 0.67. Both GCB and 5-FU induced moderate cell cycle arrest at G0/G1-phase and S-phase. Despite colossolactone-G's lack of influence on cell cycle distribution, it significantly potentiated GCB- and 5-FU-induced cell cycle arrest. Similarly, colossolactone-G treatment alone did not induce pronounced apoptosis in both cell lines. However, 5-FU and GCB induced significant apoptosis which was further potentiated via combination with colossolactone-G. Furthermore, colossolactone-G significantly increased autophagic cell death response in both HCT-116 and HT-29 cells and potentiated 5-FU- and GCB-induced autophagic cell death. The influence of colossolactone-G alone or in combination with GCB or 5-FU on the apoptosis and autophagy were confirmed by qPCR analysis for the expression of several key apoptosis and autophagy genes such as, TRAIL, TP53INP1, BNIP3, hp62, ATG5, ATG7, Lamp2A and the golden standard for autophagy (LC3-II). In conclusion, a synergistic effect in terms of anticancer properties was observed when colossolactone-G was combined with 5-FU and GCB, where it influenced both apoptosis and autophagic cell death mechanisms.