Upregulation of HAS2 promotes glioma cell proliferation and chemoresistance via c-myc

Glioblastoma multiforme (GBM) is the most common and aggressive primary malignant human brain tumor. Although comprehensive therapies, including chemotherapy and radiotherapy following surgery, have shown promise in prolonging survival, the prognosis for GBM patients remains poor, with an overall survival rate of only 14.6 months. Chemoresistance is a major obstacle to successful treatment and contributes to relapse and poor survival rates in glioma patients. Therefore, there is an urgent need for novel strategies to overcome chemoresistance and improve treatment outcomes for human glioma patients. Recent studies have shown that the tumor microenvironment plays a key role in chemoresistance. Our study demonstrates that upregulation of HAS2 and subsequent hyaluronan secretion promotes glioma cell proliferation, invasion, and chemoresistance in vitro and in vivo through the c-myc pathway. Targeting HAS2 sensitizes glioma cells to chemotherapeutic agents. Additionally, we found that hypoxia-inducible factor HIF1α regulates HAS2 expression. Together, our findings provide insights into the dysregulation of HAS2 and its role in chemoresistance and suggest potential therapeutic strategies for GBM.

Requirement of Hyaluronan Synthase-2 in Craniofacial and Palate Development

Cleft palate is a common major birth defect resulting from disruption of palatal shelf growth, elevation, or fusion during fetal palatogenesis. Whereas the molecular mechanism controlling palatal shelf elevation is not well understood, a prevailing hypothesis is that region-specific accumulation of hyaluronan, a predominant extracellular glycosaminoglycan in developing palatal mesenchyme, plays a major role in palatal shelf elevation. However, direct genetic evidence for a requirement of hyaluronan in palate development is still lacking. In this study, we show that Has2, 1 of 3 hyaluronan synthases in mammals, plays a major role in hyaluronan synthesis in the neural crest-derived craniofacial mesenchyme during palatogenesis in mice. We analyzed developmental defects caused by tissue-specific inactivation of Has2 throughout the cranial neural crest lineage or specifically in developing palatal or mandibular mesenchyme, respectively, using Wnt1-Cre, Osr2-Cre, and Hand2-Cre transgenic mice. Inactivation of Has2 either throughout the neural crest lineage or specifically in the developing palatal mesenchyme caused reduced palatal shelf size and increased palatal mesenchyme cell density prior to the time of normal palatal shelf elevation. Whereas both Has2f/f;Wnt1-Cre and Has2f/f;Osr2-Cre mutant mice exhibit cleft palate at complete penetrance, the Has2f/f; Wnt1-Cre fetuses showed dramatically reduced mandible size and complete failure of palatal shelf elevation, whereas Has2f/f;Osr2-Cre fetuses had normal mandibles and delayed palatal shelf elevation. All Has2f/f;Hand2-Cre pups showed reduced mandible size and about 50% of them had cleft palate with disruption of palatal shelf elevation. Results from explant culture assays indicate that disruption of palatal shelf elevation in Has2f/f;Hand2-Cre mutant fetuses resulted from physical obstruction by the malformed mandible and tongue. Together, these data indicate that hyaluronan plays a crucial intrinsic role in palatal shelf expansion and timely reorientation to the horizontal position above the tongue as well as an important role in mandibular morphogenesis that secondarily affects palatal shelf elevation.

Loss of the transcriptional repressor TGIF1 results in enhanced Kras-driven development of pancreatic cancer

Background

The TG-interacting factor 1 (TGIF1) gene, which encodes a nuclear transcriptional corepressor of the TGFβ1/Smad signaling pathway, has been implicated in the pathogenesis of various types of human cancer; however, its role in pancreatic ductal adenocarcinoma (PDAC) has yet to be elucidated.

Methods

The expression of TGIF1 in human and murine PDAC specimens were detected by IHC analysis. The functions of TGIF1 in in vivo PDAC growth, dissemination, and metastasis were assessed using conditional inactivation of TGIF1 in well-established autochthonous mouse models of PDAC. Primary cells from TGIF1 null or wild type PDAC mice were examined by assays for cell proliferation, migration, invasion, soft agar and xenograft tumorigenesis. Gene expression profiling, pathway analyses, epigenetic changes associated with TGIF1 loss, and in vitro and in vivo effects of 4-MU were assessed.

Results

Conditional deletion of TGIF1 in the mouse pancreas had no discernible effect on pancreatic development or physiology. Notably, TGIF1 loss induced KrasG12D-driven PDAC models exhibited shorter latency and greater propensity for distant metastases. Deciphering the molecular mechanisms highlighted the TGIF1 loss-induced activation of the hyaluronan synthase 2 (HAS2)-CD44 signaling pathway and upregulation of the immune checkpoint regulator PD-L1 to facilitate the epithelial–mesenchymal transition (EMT) and tumor immune suppression. We also founded that TGIF1 might function as an epigenetic regulator and response for aberrant EMT gene expression during PDAC progression.

Conclusions

Our results imply that targeting the HAS2 pathway in TGIF1 loss of PDAC could be a promising therapeutic strategy for improving the clinical efficacy against PDAC metastasis.

Electronic supplementary material

The online version of this article (10.1186/s12943-019-1023-1) contains supplementary material, which is available to authorized users.

Mediator complex subunit Med12 regulates cardiac jelly development and AV valve formation in zebrafish

The molecular mechanism essential for the formation of heart valves involves complex interactions of signaling molecules and transcription factors. The Mediator Complex (MC) functions as multi-subunit machinery to orchestrate gene transcription, especially for tissue-specific fine-tuning of transcriptional processes during development, also in the heart. Here, we analyzed the role of the MC subunit Med12 during atrioventricular canal (AVC) development and endocardial cushion formation, using the Med12-deficient zebrafish mutant trapped (tpd). Whereas primary heart formation was only slightly affected in tpd, we identified defects in AVC development and cardiac jelly formation. We found that although misexpression of bmp4 and versican in tpd hearts can be restored by overexpression of a modified version of the Sox9b transcription factor (harboring VP16 transactivation domain) that functions independent of its co-activator Med12, endocardial cushion development in tpd was not reconstituted. Interestingly, expression of tbx2b and its target hyaluronan synthase 2 (has2) - the synthase of hyaluronan (HA) in the heart - was absent in both uninjected and Sox9b-VP16 overexpressing tpd hearts. HA is a major ECM component of the cardiac jelly and required for endocardial cushion formation. Furthermore, we found secreted phosphoprotein 1 (spp1), an endocardial marker of activated AV endocardial cells, completely absent in tpd hearts, suggesting that crucial steps of the transformation of AV endocardial cells into endocardial cushions is blocked. We demonstrate that Med12 controls cardiac jelly formation Sox9-independently by regulating tbx2b and has2 expression and therefore the production of the glycosaminoglycan HA at the AVC to guarantee proper endocardial cushion development.

Lubricin is Required for the Structural Integrity and Post-natal Maintenance of TMJ

The Proteoglycan 4 (Prg4) product lubricin plays essential roles in boundary lubrication and movement in limb synovial joints, but its roles in temporomandibular joint (TMJ) are unclear. Thus, we characterized the TMJ phenotype in wild-type and Prg4(-/-) mouse littermates over age. As early as 2 weeks of age, mutant mice exhibited hyperplasia in the glenoid fossa articular cartilage, articular disc, and synovial membrane. By 1 month of age, there were fewer condylar superficial tenascin-C/Col1-positive cells and more numerous apoptotic condylar apical cells, while chondroprogenitors displayed higher mitotic activity, and Sox9-, Col2-, and ColX-expressing chondrocyte zones were significantly expanded. Mutant subchondral bone contained numerous Catepsin K-expressing osteoclasts at the chondro-osseous junction, increased invasive marrow cavities, and suboptimal subchondral bone. Mutant glenoid fossa, disc, synovial cells, and condyles displayed higher Hyaluronan synthase 2 expression. Mutant discs also lost their characteristic concave shape, exhibited ectopic chondrocyte differentiation, and occasionally adhered to condylar surfaces. A fibrinoid substance of unclear origin often covered the condylar surface. By 6 months of age, mutant condyles displayed osteoarthritic degradation with apical/mid-zone separation. In sum, lubricin exerts multiple essential direct and indirect roles to preserve TMJ structural and cellular integrity over post-natal life.

Knockdown of TrkA in cumulus oocyte complexes (COCs) inhibits EGF-induced cumulus expansion by down-regulation of IL-6

Tyrosine kinase receptor A (TrkA), the high-affinity receptor of nerve growth factor (NGF), is known to play key roles in ovarian follicular development, such as assembly of early follicles and follicular ovulation. However, little is known about the roles of TrkA in cumulus oocyte complex (COC) expansion. In this study, we found that TrkA was abundant in large antral follicles and knockdown of TrkA in COCs attenuated epidermal growth factor (EGF)-induced COC expansion and further decreased the ovulation rate. The effect of TrkA on COC expansion was not mediated through downstream EGF effectors, phosphorylation of extracellular regulated protein kinases 1/2 (ERK1/2) or drosophila mothers against decapentaplegic protein (SMAD), or through up-regulation of COC expansion-related transcripts such as prostaglandin-endoperoxide synthase 2 (Ptgs2), hyaluronan synthase 2 (Has2), TNF-induced protein 6 (Tnfaip6) or pentraxin 3 (Ptx3). However, pharmacological blockade of TrkA transducing activity (K252α) in COCs decreased the mRNA expression and protein secretion of interleukin-6 (IL-6), identified from mRNA microarray of K252α-treated COCs. Meanwhile, knockdown of IL-6 attenuated EGF-induced COC expansion. In addition, IL-6 rescued the inhibitory effect of K252α on EGF-induced cumulus expansion. Therefore, IL-6 may act as a new potential cumulus expansion-related transcript, which may be involved in the integration of TrkA and EGF signaling in affecting COC expansion. Here, we provide mechanistic insights into the roles of TrkA in EGF-induced cumulus expansion. Understanding potential cross-points between TrkA and EGF affecting cumulus expansion will help in the discovery of new therapeutic targets in ovulation-related diseases.