Exploring novel immunotherapy biomarker candidates induced by cancer deformation.

Triple-negative breast cancer (TNBC) demands urgent attention for the development of effective treatment strategies due to its aggressiveness and limited therapeutic options [1]. This research is primarily focused on identifying new biomarkers vital for immunotherapy, with the aim of developing tailored treatments specifically for TNBC, such as those targeting the PD-1/PD-L1 pathway. To achieve this, the study places a strong emphasis on investigating Ig genes, a characteristic of immune checkpoint inhibitors, particularly genes expressing Ig-like domains with altered expression levels induced by "cancer deformation," a condition associated with cancer malignancy. Human cells can express approximately 800 Ig family genes, yet only a few Ig genes, including PD-1 and PD-L1, have been developed into immunotherapy drugs thus far. Therefore, we investigated the Ig genes that were either upregulated or downregulated by the artificial metastatic environment in TNBC cell line. As a result, we confirmed the upregulation of approximately 13 Ig genes and validated them using qPCR. In summary, our study proposes an approach for identifying new biomarkers applicable to future immunotherapies aimed at addressing challenging cases of TNBC where conventional treatments fall short.

Independent Skeletal Actions of Pituitary Hormones.

Over the past years, pituitary hormones and their receptors have been shown to have non-traditional actions that allow them to bypass the hypothalamus-pituitary-effector glands axis. Bone cells-osteoblasts and osteoclasts-express receptors for growth hormone, follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), prolactin, oxytocin, and vasopressin. Independent skeletal actions of pituitary hormones on bone have been studied using genetically modified mice with haploinsufficiency and by activating or inactivating the receptors pharmacologically, without altering systemic effector hormone levels. On another front, the discovery of a TSH variant (TSH-ßv) in immune cells in the bone marrow and skeletal action of FSHß through tumor necrosis factor α provides new insights underscoring the integrated physiology of bone-immune-endocrine axis. Here we discuss the interaction of each pituitary hormone with bone and the potential it holds in understanding bone physiology and as a therapeutic target.

Bone-modifying agents for bone loss in patients with prostate cancer receiving androgen deprivation therapy; insights from a network meta-analysis.

BACKGROUND: The data of head-to-head comparisons of the effect of bone-modifying agents (BMAs) in patients with androgen deprivation therapy (ADT) for prostate cancer without skeletal metastasis is limited. Thus, we conducted a network meta-analysis to compare each BMA for the efficacy of bone mineral densities (BMDs) and the risk of fracture. METHODS: We performed a network meta-analysis to compare the change of BMDs and the risk of vertebral fracture in the studies included using a random-effect model. The primary outcomes are the change of BMD of the lumbar spine (LS) and the total hip (TH) from the baseline at 1 year from the initiation of the BMA and the risk of vertebral fracture. RESULTS: We identified and included 15 studies in this analysis. All BMAs except risedronate showed a significant increase of BMD of the LS compared with groups without BMA, among which zoledronate showed the most BMD gain. At TH, bisphosphonates (alendronate, pamidronate, and zoledronate) and denosumab showed significant elevation compared with the no-BMA group. Denosumab was associated with the most BMD gain at the TH. Only denosumab reduced the risk of vertebral fracture (relative risk [95% confidence interval]: 0.40 [0.20-0.81]). Although zoledronate showed the highest BMD gain at the LS, it did not reduce the risk of vertebral fracture in this analysis. CONCLUSION: Most bisphosphonates and denosumab significantly increased BMD at the LS and the TH in patients receiving ADT for prostate cancer without skeletal metastasis. In particular, zoledronate and denosumab were the most potent BMAs in terms of BMD increment at the LS and the TH, respectively. However, denosumab, not zoledronate, was the only BMA that showed a significant risk reduction of vertebral fracture. We need further studies to examine the change of bone quality and the effect on the risk of non-vertebral and hip fractures.

PLGA Core-Shell Nano/Microparticle Delivery System for Biomedical Application.

Core-shell particles are very well known for their unique features. Their distinctive inner core and outer shell structure allowed promising biomedical applications at both nanometer and micrometer scales. The primary role of core-shell particles is to deliver the loaded drugs as they are capable of sequence-controlled release and provide protection of drugs. Among other biomedical polymers, poly (lactic-co-glycolic acid) (PLGA), a food and drug administration (FDA)-approved polymer, has been recognized for the vehicle material. This review introduces PLGA core-shell nano/microparticles and summarizes various drug-delivery systems based on these particles for cancer therapy and tissue regeneration. Tissue regeneration mainly includes bone, cartilage, and periodontal regeneration.

Thyrotropin, Hyperthyroidism, and Bone Mass.

Thyrotropin (TSH), traditionally seen as a pituitary hormone that regulates thyroid glands, has additional roles in physiology including skeletal remodeling. Population-based observations in people with euthyroidism or subclinical hyperthyroidism indicated a negative association between bone mass and low-normal TSH. The findings of correlative studies were supported by small intervention trials using recombinant human TSH (rhTSH) injection, and genetic and case-based evidence. Genetically modified mouse models, which disrupt the reciprocal relationship between TSH and thyroid hormone, have allowed us to examine an independent role of TSH. Since the first description of osteoporotic phenotype in haploinsufficient Tshr +/- mice with normal thyroid hormone levels, the antiosteoclastic effect of TSH has been documented in both in vitro and in vivo studies. Further studies showed that increased osteoclastogenesis in Tshr-deficient mice was mediated by tumor necrosis factor α. Low TSH not only increased osteoclastogenesis, but also decreased osteoblastogenesis in bone marrow-derived primary osteoblast cultures. However, later in vivo studies using small and intermittent doses of rhTSH showed a proanabolic effect, which suggests that its action might be dose and frequency dependent. TSHR was shown to interact with insulin-like growth factor 1 receptor, and vascular endothelial growth factor and Wnt pathway might play a role in TSH's effect on osteoblasts. The expression and direct skeletal effect of a biologically active splice variant of the TSHß subunit (TSHßv) in bone marrow-derived macrophage and other immune cells suggest a local skeletal effect of TSHR. Further studies of how locally secreted TSHßv and systemic TSHß interact in skeletal remodeling through the endocrine, immune, and skeletal systems will help us better understand the hyperthyroidism-induced bone disease.

The hepcidin regulator erythroferrone is a new member of the erythropoiesis-iron-bone circuitry.

Background: Erythroblast erythroferrone (ERFE) secretion inhibits hepcidin expression by sequestering several bone morphogenetic protein (BMP) family members to increase iron availability for erythropoiesis. Methods: To address whether ERFE functions also in bone and whether the mechanism of ERFE action in bone involves BMPs, we utilize the Erfe-/- mouse model as well as ß-thalassemic (Hbbth3/+) mice with systemic loss of ERFE expression. In additional, we employ comprehensive skeletal phenotyping analyses as well as functional assays in vitro to address mechanistically the function of ERFE in bone. Results: We report that ERFE expression in osteoblasts is higher compared with erythroblasts, is independent of erythropoietin, and functional in suppressing hepatocyte hepcidin expression. Erfe-/- mice display low-bone-mass arising from increased bone resorption despite a concomitant increase in bone formation. Consistently, Erfe-/- osteoblasts exhibit enhanced mineralization, Sost and Rankl expression, and BMP-mediated signaling ex vivo. The ERFE effect on osteoclasts is mediated through increased osteoblastic RANKL and sclerostin expression, increasing osteoclastogenesis in Erfe-/- mice. Importantly, Erfe loss in Hbbth3/+mice, a disease model with increased ERFE expression, triggers profound osteoclastic bone resorption and bone loss. Conclusions: Together, ERFE exerts an osteoprotective effect by modulating BMP signaling in osteoblasts, decreasing RANKL production to limit osteoclastogenesis, and prevents excessive bone loss during expanded erythropoiesis in ß-thalassemia. Funding: YZG acknowledges the support of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (R01 DK107670 to YZG and DK095112 to RF, SR, and YZG). MZ acknowledges the support of the National Institute on Aging (U19 AG60917) and NIDDK (R01 DK113627). TY acknowledges the support of the National Institute on Aging (R01 AG71870). SR acknowledges the support of NIDDK (R01 DK090554) and Commonwealth Universal Research Enhancement (CURE) Program Pennsylvania.

The NO-cGMP-PKG pathway in skeletal remodeling.

The nitric oxide (NO)-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway plays a critical role in skeletal homeostasis. Preclinical data using NO and its donors and genetically modified mice demonstrated that NO was required in bone remodeling and partly mediated the anabolic effects of mechanical stimuli and estrogen. However, the off-target effects and tachyphylaxis of NO limit its long-term use, and previous clinical trials using organic nitrates for osteoporosis have been disappointing. Among the other components in the downstream pathway, targeting cGMP-specific phosphodiesterase to promote the NO-cGMP-PKG signal is a viable option. There are growing in vitro and in vivo data that, among many other PDE families, PDE5A is highly expressed in skeletal tissue, and inhibiting PDE5A using currently available PDE5A inhibitors might increase the osteoanabolic signal and protect the skeleton. These preclinical data open the possibility of repurposing PDE5A inhibitors for treating osteoporosis. Further research is needed to address the primary target bone cell of PDE5A inhibition, the contribution of direct and indirect effects of PDE5A inhibition, and the pathophysiological changes in skeletal PDE5A expression in aging and hypogonadal animal models.

First-in-class humanized FSH blocking antibody targets bone and fat.

Blocking the action of FSH genetically or pharmacologically in mice reduces body fat, lowers serum cholesterol, and increases bone mass, making an anti-FSH agent a potential therapeutic for three global epidemics: obesity, osteoporosis, and hypercholesterolemia. Here, we report the generation, structure, and function of a first-in-class, fully humanized, epitope-specific FSH blocking antibody with a KD of 7 nM. Protein thermal shift, molecular dynamics, and fine mapping of the FSH-FSH receptor interface confirm stable binding of the Fab domain to two of five receptor-interacting residues of the FSHß subunit, which is sufficient to block its interaction with the FSH receptor. In doing so, the humanized antibody profoundly inhibited FSH action in cell-based assays, a prelude to further preclinical and clinical testing.

Beyond bone biology: Lessons from team science.

Today, research in biomedicine often requires the knowledge and technologies in diverse fields. Therefore, there is an increasing need for collaborative team science that crosses traditional disciplines. Here, we discuss our own lessons from both interdisciplinary and transdisciplinary teams, which ultimately ushered us to expand our research realm beyond bone biology.

Bone modifying agents for bone loss in patients with aromatase inhibitor as adjuvant treatment for breast cancer; insights from a network meta-analysis.

PURPOSE: The data of head-to-head comparisons of the anti-fracture efficacy of bone modifying agents (BMAs) in patients with hormone receptor-positive breast cancer receiving aromatase inhibitor (AI) are not available. Therefore, we conducted a network meta-analysis to compare the efficacy of different BMAs in patients with breast cancer receiving adjuvant AI. METHODS: We performed a network meta-analysis to compare the change of bone mineral densities (BMDs) and the risk of fracture in the selected studies using a random effect model. The primary outcomes are the change of BMD of lumbar spine (LS) and total hip (TH) from the baseline (ΔBMD, %) at 1 and 2 years and the risk of fracture. RESULTS: We identified and included a total of 16 randomized controlled trials for this analysis. All BMAs included (risedronate, zoledronate, and denosumab) were associated with a significant increase in BMD of LS and TH at 1 and 2 years compared with no upfront treatment group. Among BMAs, zoledronate and denosumab use resulted in significantly higher BMD of LS and TH at 1 and 2 years compared with risedronate. The risk of fracture was significantly lower in the patients who received denosumab or risedronate compared with the patients without upfront treatment (Relative risk (RR) [95% CI] 0.51 [0.38-0.67] and 0.54 [0.35-0.83], respectively). CONCLUSION: Among the bisphosphonates, zoledronate increased BMD the most, but risedronate, not zoledronate, use was associated with lower risk of fracture. Denosumab increased BMD not only of LS but also of the cortical-bone-rich hip, and showed a significant reduction of fracture risk.

Oxytocin regulates body composition.

The primitive neurohypophyseal nonapeptide oxytocin (OXT) has established functions in parturition, lactation, appetite, and social behavior. We have shown that OXT has direct actions on the mammalian skeleton, stimulating bone formation by osteoblasts and modulating the genesis and function of bone-resorbing osteoclasts. We deleted OXT receptors (OXTRs) selectively in osteoblasts and osteoclasts using Col2.3Cre and Acp5Cre mice, respectively. Both male and female Col2.3Cre+:Oxtrfl/fl mice recapitulate the low-bone mass phenotype of Oxtr+/- mice, suggesting that OXT has a prominent osteoblastic action in vivo. Furthermore, abolishment of the anabolic effect of estrogen in Col2.3Cre+:Oxtrfl/fl mice suggests that osteoblastic OXTRs are necessary for estrogen action. In addition, the high bone mass in Acp5Cre+:Oxtrfl/fl mice indicates a prominent action of OXT in stimulating osteoclastogenesis. In contrast, we found that in pregnant and lactating Col2.3Cre+:Oxtrfl/fl mice, elevated OXT inhibits bone resorption and rescues the bone loss otherwise noted during pregnancy and lactation. However, OXT does not contribute to ovariectomy-induced bone loss. Finally, we show that OXT acts directly on OXTRs on adipocytes to suppress the white-to-beige transition gene program. Despite this direct antibeiging action, injected OXT reduces total body fat, likely through an action on OXT-ergic neurons. Consistent with an antiobesity action of OXT, Oxt-/- and Oxtr-/- mice display increased total body fat. Overall, the actions of OXT on bone mass and body composition provide the framework for future therapies for osteoporosis and obesity.

FSH-metabolic circuitry and menopause.

FSH has a primary function in procreation, wherein it induces estrogen production in females and regulates spermatogenesis in males. However, in line with our discoveries over the past decade of non-unitary functions of pituitary hormones, we and others have described hitherto uncharacterized functions of FSH. Through high-affinity receptors, some of which are variants of the ovarian FSH receptor (FSHR), FSH regulates bone mass, adipose tissue function, energy metabolism, and cholesterol production in both sexes. These newly described actions of FSH may indeed be relevant to the pathogenesis of bone loss, dysregulated energy homeostasis, and disordered lipid metabolism that accompany the menopause in females and aging in both genders. We are therefore excited about the possibility of modulating circulating FSH levels toward a therapeutic benefit for a host of age-associated diseases, including osteoporosis, obesity and dyslipidemia, among other future possibilities.

FSH Beyond Fertility.

The traditional view of follicle-stimulating hormone (FSH) as a reproductive hormone is changing. It has been shown that FSH receptors (FSHRs) are expressed in various extra-gonadal tissues and mediate the biological effects of FSH at those sites. Molecular, animal, epidemiologic, and clinical data suggest that elevated serum FSH may play a significant role in the evolution of bone loss and obesity, as well as contributing to cardiovascular and cancer risk. This review summarizes recent data on FSH action beyond reproduction.

CUSHING DISEASE MASQUERADING AS GLAUCOMA.

OBJECTIVE: Glaucoma is a well-recognized side effect of corticosteroids. However, steroid-induced glaucoma typically refers to that caused by exogenous corticosteroid administration. Glaucoma secondary to endogenous overproduction of corticosteroids has only been reported in a few case reports. We aim to bring attention to glaucoma as a rare but important manifestation of endogenous hypercortisolism. METHODS: Patient history, physical exam, laboratory results, and imaging studies were reviewed. RESULTS: We report a case of glaucoma as the initial presentation of Cushing disease (CD). The patient was diagnosed with glaucoma 16 months prior to his endocrinology evaluation. At our initial encounter, the patient had a cushingoid appearance. Levels of 24-hour urinary cortisol and late-night salivary cortisol were elevated. Serum cortisol was not suppressed by 1 mg of dexamethasone overnight, but it was suppressed by 8 mg of dexamethasone. Adrenocorticotropic hormone was also elevated. All other pituitary hormone axes were unremarkable (thyroid-stimulating hormone, free thyroxine, follicle-stimulating hormone, luteinizing hormone, growth hormone, prolactin, and insulin-like growth factor). Pituitary magnetic resonance imaging suggested a small adenoma (2 to 3 mm); therefore, the patient underwent inferior petrosal sinus sampling. The results were consistent with CD. Transsphenoidal resection was performed and final pathology confirmed an adrenocorticotropic hormone-positive adenoma. Hypercortisolism and intraocular pressures improved after the surgery. CONCLUSION: Glaucoma can lead to irreversible blindness if left untreated or uncontrolled. However, endogenous hypercortisolism-induced glaucoma can be reversed with treatment of the underlying CD. Thus, heightened awareness of extraocular manifestations of secondary causes of glaucoma such as endogenous hypercortisolism is necessary in order to promote prompt evaluation and treatment.

Anti-inflammatory and Osteogenic Effects of Calcium Silicate-based Root Canal Sealers.

INTRODUCTION: An ideal root canal sealer creates a bacteria-resistant seal and exhibits antimicrobial activity, biocompatibility, and osteoconductivity. The aim of this study was to assess the effects of 3 root canal sealers on cell viability, inflammatory response, and osteogenic potential in MC3T3-E1 cells. METHODS: AH Plus (Dentsply Caulk, Milford, DE), MTA Fillapex (Angelus Solucxoes Odontologicas, Londrina, Brazil), and EndoSequence BC (Brasseler, Savannah, GA) were mixed according to the manufacturer's instructions, and samples were prepared as extraction media (final dilution: 1/10). Lipopolysaccharide (LPS) (100 ng/mL) treatment was used to induce an inflammatory response in this study. Cell viability was evaluated using the Water soluble tetrazolium-1 (WST-1) assay. The levels of inflammatory mediators (interleukin 6 and tumor necrosis factor alpha) and osteogenic marker genes (ALP and OCN) were measured by reverse-transcription polymerase chain reaction and real-time polymerase chain reaction. Osteogenic potential was evaluated by alkaline phosphatase staining and alizarin red staining. RESULTS: Calcium silicate-based sealers such as MTA Fillapex and EndoSequence BC showed strong cell viability compared with AH Plus. AH Plus, MTA Fillapex, and EndoSequence BC decreased the levels of LPS-induced inflammatory mediators (P < .05). The expression of osteogenic marker genes, alkaline phosphatase activity, and mineralized nodule formation decreased with LPS treatment. However, AH Plus and calcium silicate-based sealers increased the osteogenic potential reduced by LPS treatment (P < .05). CONCLUSIONS: Calcium silicate-based sealers exhibit anti-inflammatory effects and induce osteogenic differentiation in MC3T3-E1 cells.

FSIP1 regulates autophagy in breast cancer.

Fibrous sheath interacting protein 1 (FSIP1) is a cancer antigen expressed in the majority of breast cancer tissues and is associated with poor prognosis. However, the role of FSIP1 in the progression and drug sensitivity of triple-negative breast cancer (TNBC) has not been explored. Here, we show that FSIP1 deficiency by shRNA-mediated knockdown or CRISPR-Cas9-mediated knockout significantly inhibits the proliferation and invasion of TNBC cells and impairs chemotherapy-induced growth inhibition in vivo. Computational modeling predicted that FSIP1 binds to ULK1, and this was established by coimmunoprecipitation. FSIP1 deficiency promoted autophagy, enhanced AMP-activated protein kinase (AMPK) signaling, and decreased mechanistic target of rapamycin (mTOR) and Wnt/ß-catenin activity. In contrast, knockdown of AMPK or inhibition of autophagy restored the sensitivity to chemotherapy drugs in TNBC cells. Our findings uncover a role of FSIP1 as well as mechanisms underlying FSIP1 action in drug sensitivity and may, therefore, aid in design of TNBC therapies.

FSH, Bone Mass, Body Fat, and Biological Aging.

The Study of Women's Health Across the Nation has taught us that impending ovarian failure during late perimenopause is associated with a sharp rise in serum FSH, which coincides with the most rapid rate of bone loss and the onset of visceral adiposity. At this time in a woman's life, serum estrogen levels are largely unaltered, so the hypothesis that hypoestrogenemia is the sole cause of bone loss and visceral obesity does not offer a full explanation. An alternative explanation, arising from animal models and human data, is that both physiologic aberrations, obesity and osteoporosis, arise at least in part from rising FSH levels. Here, we discuss recent findings on the mechanism through which FSH exerts biological actions on bone and fat and review clinical data that support a role for FSH in causing osteoporosis and obesity. We will also provide a conceptual framework for using a single anti-FSH agent to prevent and treat both osteoporosis and obesity in women across the menopausal transition.

Epitope-specific monoclonal antibodies to FSHß increase bone mass.

Pituitary hormones have long been thought solely to regulate single targets. Challenging this paradigm, we discovered that both anterior and posterior pituitary hormones, including FSH, had other functions in physiology. We have shown that FSH regulates skeletal integrity, and, more recently, find that FSH inhibition reduces body fat and induces thermogenic adipose tissue. A polyclonal antibody raised against a short, receptor-binding epitope of FSHß was found not only to rescue bone loss postovariectomy, but also to display marked antiobesity and probeiging actions. Questioning whether a single agent could be used to treat two medical conditions of public health importance--osteoporosis and obesity--we developed two further monoclonal antibodies, Hf2 and Mf4, against computationally defined receptor-binding epitopes of FSHß. Hf2 has already been shown to reduce body weight and fat mass and cause beiging in mice on a high-fat diet. Here, we show that Hf2, which binds mouse Fsh in immunoprecipitation assays, also increases cortical thickness and trabecular bone volume, and microstructural parameters, in sham-operated and ovariectomized mice, noted on microcomputed tomography. This effect was largely recapitulated with Mf4, which inhibited bone resorption by osteoclasts and stimulated new bone formation by osteoblasts. These effects were exerted in the absence of alterations in serum estrogen in wild-type mice. We also reconfirm the existence of Fshrs in bone by documenting the specific binding of fluorescently labeled FSH, FSH-CH, in vivo. Our study provides the framework for the future development of an FSH-based therapeutic that could potentially target both bone and fat.

THYMIC CARCINOID WITH ADRENOCORTICOTROPIC HORMONE-PRODUCING ECTOPIC CUSHING SYNDROME AND EMPTY SELLA.

OBJECTIVE: Ectopic Cushing's syndrome secondary to thymic carcinoid is a rare disorder that may be difficult to diagnose and manage. METHODS: We describe a case of severe Cushing's syndrome secondary to a large adrenocorticotropic hormone (ACTH) producing thymic carcinoid in a patient with history of primary hyperaldosteronism. RESULTS: A 43-year-old female with a 20-year history of an aldosterone-secreting adrenocortical adenoma status post right adrenalectomy presented with acute onset of proximal muscle weakness, swelling, facial hirsutism, and severe hypokalemia. Ectopic Cushing's Syndrome was suspected based on the sudden symptom onset and markedly elevated 24-hr urine cortisol and ACTH levels. MRI revealed an empty pituitary sella and a large (7.3 cm) mediastinal mass visible on chest CT. The mass was resected by video-assisted thoracoscopic surgery, resulting in resolution of symptoms and cortisol levels. Pathology assessment confirmed well-differentiated thymic carcinoid with positive ACTH staining. CONCLUSION: The case highlights clinical features, challenges in diagnostic work up, treatment modalities, and associated endocrine findings in a thymic carcinoid abutting the heart and presenting with ectopic ACTH secretion.

Odontogenic Potential of Parathyroid Hormone-related Protein (107-111) Alone or in Combination with Mineral Trioxide Aggregate in Human Dental Pulp Cells.

INTRODUCTION: Parathyroid hormone-related protein plays an important role in bone remodeling. Its N-terminal domain parathyroid hormone-related protein (107-111) is called osteostatin (OST). OST has demonstrated osteogenic potential when combined with biomaterials such as hydroxyapatite or bioceramics. However, the odontogenic potential of OST has not yet been reported. Therefore, the aim of this study was to determine whether OST has an odontogenic effect or a synergistic effect with mineral trioxide aggregate (MTA) in human dental pulp cells (hDPCs) and to examine the underlying signaling mechanisms involved in OST-mediated odontogenic differentiation. METHODS: Viability of hDPCs on stimulation with OST or MTA was measured. Real-time polymerase chain reaction and Western blot analyses were performed to evaluate the expression levels of odontogenic markers and the activation of extracellular signal-regulated kinase (ERK). To evaluate mineralized nodule formation, alkaline phosphatase (ALP) staining and alizarin red S staining were performed. Combined effects of OST and MTA were evaluated. RESULTS: OST promoted odontogenic differentiation, as evidenced by the formation of mineralized nodules, induction of ALP activity, and upregulation of odontogenic markers (dentin sialophosphoprotein, dentin matrix protein-1, and ALP). Phosphorylation of ERK was increased by OST. However, ERK inhibitor (U0126) inhibited the increase in dentin sialophosphoprotein and dentin matrix protein-1 expression and mineralization induced by OST. A combination of MTA and OST upregulated odontogenic differentiation-associated gene expression and calcium nodule mineralization in hDPCs compared with MTA alone. CONCLUSIONS: The present study revealed that OST can promote odontogenic differentiation and mineralization through activating the ERK signaling pathway. A combination of MTA and OST showed a synergistic effect compared with MTA alone in hDPCs.