Correction to "Rapamycin Inhibits Osteoclastogenesis and Prevents LPS-Induced Alveolar Bone Loss by Oxidative Stress Suppression".

[This corrects the article DOI: 10.1021/acsomega.3c01289.].

Rapamycin Inhibits Osteoclastogenesis and Prevents LPS-Induced Alveolar Bone Loss by Oxidative Stress Suppression.

Periodontitis is a progressive inflammatory skeletal disease characterized by periodontal tissue destruction, alveolar bone resorption, and tooth loss. Chronic inflammatory response and excessive osteoclastogenesis play essential roles in periodontitis progression. Unfortunately, the pathogenesis that contributes to periodontitis remains unclear. As a specific inhibitor of the mTOR (mammalian/mechanistic target of rapamycin) signaling pathway and the most common autophagy activator, rapamycin plays a vital role in regulating various cellular processes. The present study investigated the effects of rapamycin on osteoclast (OC) formation in vitro and its effects on the rat periodontitis model. The results showed that rapamycin inhibited OC formation in a dose-dependent manner by up-regulating the Nrf2/GCLC signaling pathway, thus suppressing the intracellular redox status, as measured by 2',7'-dichlorofluorescein diacetate and MitoSOX. In addition, rather than simply increasing the autophagosome formation, rapamycin increased the autophagy flux during OC formation. Importantly, the anti-oxidative effect of rapamycin was regulated by an increase in autophagy flux, which could be attenuated by blocking autophagy with bafilomycin A1. In line with the in vitro results, rapamycin treatment attenuated alveolar bone resorption in rats with lipopolysaccharide-induced periodontitis in a dose-dependent manner, as assessed by micro-computed tomography, hematoxylin-eosin staining, and tartrate-resistant acid phosphatase staining. Besides, high-dose rapamycin treatment could reduce the serum levels of proinflammatory factors and oxidative stress in periodontitis rats. In conclusion, this study expanded our understanding of rapamycin's role in OC formation and protection from inflammatory bone diseases.

Tamoxifen represses miR-200 microRNAs and promotes epithelial-to-mesenchymal transition by up-regulating c-Myc in endometrial carcinoma cell lines.

Although tamoxifen (TAM), a selective estrogen receptor modulator, has been widely used in the treatment of hormone-responsive breast cancer, its estrogen-like effect increases the risk of endometrial cancer. However, the molecular mechanisms of TAM-induced endometrial carcinoma still remain unclear. In this report, we explored the role of microRNAs (miRNAs) in TAM-induced epithelial-mesenchymal transition (EMT) in ECC-1 and Ishikawa endometrial cancer cell lines and found miR-200 is involved in this process via the regulation of c-Myc. When treated with TAM, ECC-1 and Ishikawa cells were characterized by higher invasiveness and motility and underwent EMT. miR-200, a miRNA family with tumor suppressive functions in a wide range of cancers, was found reduced in response to TAM treatment. Consistent with zinc finger E-box binding homeobox 2, which was confirmed as a direct target of miR-200b in endometrial cancer cell lines, some other key factors of EMT such as Snail and N-cadherin increased, whereas E-cadherin decreased in the TAM-treated cells, contributing to TAM-induced EMT in these endometrial cancer cells. In addition, we showed that c-Myc directly binds to and represses the promoter of miR-200 miRNAs, and its up-regulation in TAM-treated endometrial cancer cells leads to the down-regulation of miR-200 and eventually to EMT. Collectively, our data suggest that TAM can repress the miR-200 family and induce EMT via the up-regulation of c-Myc in endometrial cancer cells. These findings describe a possible mechanism of TAM-induced EMT in endometrial cancer and provide a potential new therapeutic strategy for it.

TSA suppresses miR-106b-93-25 cluster expression through downregulation of MYC and inhibits proliferation and induces apoptosis in human EMC.

Histone deacetylase (HDAC) inhibitors are emerging as a novel class of anti-tumor agents and have manifested the ability to decrease proliferation and increase apoptosis in different cancer cells. A significant number of genes have been identified as potential effectors responsible for the anti-tumor function of HDAC inhibitor. However, the molecular mechanisms of these HDAC inhibitors in this process remain largely undefined. In the current study, we searched for microRNAs (miRs) that were affected by HDAC inhibitor trichostatin (TSA) and investigated their effects in endometrial cancer (EMC) cells. Our data showed that TSA significantly inhibited the growth of EMC cells and induced their apoptosis. Among the miRNAs that altered in the presence of TSA, the miR-106b-93-25 cluster, together with its host gene MCM7, were obviously down-regulated in EMC cells. p21 and BIM, which were identified as target genes of miR-106b-93-25 cluster, increased in TSA treated tumor cells and were responsible for cell cycle arrest and apoptosis. We further identified MYC as a regulator of miR-106b-93-25 cluster and demonstrated its down-regulation in the presence of TSA resulted in the reduction of miR-106b-93-25 cluster and up-regulation of p21 and BIM. More important, we found miR-106b-93-25 cluster was up-regulated in clinical EMC samples in association with the overexpression of MCM7 and MYC and the down-regulation of p21 and BIM. Thus our studies strongly indicated TSA inhibited EMC cell growth and induced cell apoptosis and cell cycle arrest at least partially through the down-regulation of the miR-106b-93-25 cluster and up-regulation of it's target genes p21 and BIM via MYC.

Estrogen-induced dimerization and activation of ERα-fused caspase-8: artificial reversal of the estrogenic hormone effect in carcinogenesis.

The cascade of caspase processing and activation is the core of apoptotic cell signaling. Initiator caspases are activated by adaptor-mediated clustering, which allows the intermolecular autoprocessing of the zymogens in close proximity. Caspase-8, the prototypical initiator critically involved in apoptosis induced by varied extrinsic stimuli, is physiologically recruited via a classical FasL/Fas/FADD pathway. Meanwhile, artificial models of caspase-8 activation have been proposed via inducible dimerization of a heterologous domain fused to the zymogen. Here, we describe the generation of a chimeric protein of caspase-8 and the ligand-binding domain (LBD) of estrogen receptor α (ERα), which dimerizes and undergoes autocleavage upon engagement by the ligand, estradiol. Breast cancer cells expressing this fusion protein exhibit apoptotic cell death in vitro and suppressed tumor growth in xenograft nude mice models in response to the administration of estrogen. Thus, the suicidal caspase-8/ERα-LBD protein, which reverses the mitogenic effects of estrogens, has potential to provide novel approaches to treating estrogen-dependent and -independent breast cancers.

Ibandronate promotes osteogenic differentiation of periodontal ligament stem cells by regulating the expression of microRNAs.

Bisphosphonates (BPs) have a profound effect on bone resorption and are widely used to treat osteoclast-mediated bone diseases. They suppress bone resorption by inhibiting the activity of mature osteoclasts and/or the formation of new osteoclasts. Osteoblasts may be an alternative target for BPs. Periodontal ligament stem cells (PDLSCs) exhibit osteoblast-like features and are capable of differentiating into osteoblasts or cementoblasts. This study aimed to determine the effects of ibandronate, a nitrogen-containing BP, on the proliferation and the differentiation of PDLSCs and to identify the microRNAs (miRNAs) that mediate these effects. The PDLSCs were treated with ibandronate, and cell proliferation was measured using the MTT (3-dimethylthiazol-2,5-diphenyltetrazolium bromide) assay. The expression of genes and miRNAs involved in osteoblastic differentiation was assayed using quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR). Ibandronate promoted the proliferation of PDLSCs and enhanced the expression of alkaline phosphatase (ALP), type I collagen (COL-1), osteoprotegerin (OPG), osteocalcin (OCN), and Runx2. The expression of miRNAs, including miR-18a, miR-133a, miR-141 and miR-19a, was significantly altered in the PDLSCs cultured with ibandronate. In PDLSCs, ibandronate regulates the expression of diverse bone formation-related genes via miRNAs. The exact mechanism underlying the role of ibandronate in osteoblasts has not been completely understood. Ibandronate may suppress the activity of osteoclasts while promoting the proliferation of osteoblasts by regulating the expression of miRNAs.

[Expression of a chimeric gene containing poly-arginine as the protein transduction domain and its killing activity against HER2 positive gastric cancer SGC-7901 cells].

AIM: To construct a eukaryotic expression vector for chimeric gene containing poly-arginine as the protein transduction domain(PTD) and transiently transfect this vector into HER2 positive SGC-7901 cells and HER2 negative HeLa cells to examine its effect on cell growth. METHODS: PCR amplication was used to obtain the gene of active form caspase-3 fused with nonaarginine, and then fusion gene was cloned into eukaryotic expression vector containing e23sFv DNA fragment. After this chimeric gene transfected into SGC-7901 cells and HeLa cells by Lipofectamine 2000™; reagent, indirect immunofluorescence and cell counting were used to examine the expression in these two cells and the effect on cell growth. RESULTS: The eukaryotic expression vector, named pCMV-e23sFv-R9;-casp3, encoding e23sFv/caspase-3 containing nonaarginine as the PTD was successfully constructed. e23sFv- R9;-casp3 protein was expressed in a secretary manner in both SGC-7901 cells and HeLa cells. Transfected SGC-7901 cells were found obvious growth inhibitory, morphology change and condensed nucleus, whereas neither growth inhibitory nor apparent morphology change was detected in transfected HeLa cells. CONCLUSION: Of the secretary expressed chimeric protein, the antibody moiety against HER2 can mediate targeted recognition, the nonaarginine translocating peptide can promote activation and translocation of the effector molecule, and the active caspase-3 can effectively induce cell killing.