Receptor tyrosine kinase inhibition causes simultaneous bone loss and excess bone formation within growing bone in rats

Ovarian cancer G protein-coupled receptor 1 inhibits A549 cells migration through casein kinase 2α intronless gene and neutral endopeptidase

Background

We have previously reported that a new intronless gene for casein kinase 2α (CK2α), CSNK2A3, is expressed in human cells. The promoter of the well-known CK2α, CSNK2A1, displays characteristics of a housekeeping gene, whereas CSNK2A3 has a characteristic of a regulated promoter with two TATA boxes and a CAAT box. GPR68, a family of the G protein-coupled receptors, is also known as ovarian cancer G protein-coupled receptor 1 (OGR1). In the current study, we analyzed the roles of CK2α genes and neutral endopeptidase (NEP), a key enzyme that influences a variety of malignancies, in the OGR1-induced inhibition of A549 cell migration.

Methods

We analyzed the transcript expressions of both the CK2α genes (CSNK2A1 and CSNK2A3) and NEP upon OGR1 overexpression. Protein expression of CK2α and NEP were also analyzed. We further elucidated the functional roles of both CK2α and NEP in the OGR1-induced inhibition of A549 cell migration in vitro using a wound-healing assay. We also analyzed the molecular mechanisms involved in the OGR1-induced inhibition of lung cancer cell migration.

Results

The findings of this study showed that OGR1 upregulated the expression of CSNK2A3 but not CSNK2A1 in the A549 cells. The findings further suggested OGR1 also upregulates the expression of NEP. The OGR1-induced inhibition of A549 cell migration was abrogated completely by inhibition of CK2α activity, whereas partial abrogation (~ 30%) was observed in the presence of NEP inhibition. The results also revealed that OGR1 regulates CSNK2A3 via activation of Rac1/cdc42 and MAPKs pathways. CK2 is ubiquitously expressed, and in contrast, is believed to be a constitutively active enzyme, and its regulation appears to be independent of known second messengers.

Conclusion

In the current study, we report for the first time the OGR1-induced regulation of CSNK2A3, CK2αP, and NEP in A549 cancer cells. Our study also decoded the downstream cellular proteins of OGR1 as well as the molecular mechanism involved in OGR1-induced inhibition of A549 cell migration. The findings of this research suggest the potential therapeutic targets to inhibit lung cancer progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09257-1.

A Selective FGFR inhibitor AZD4547 suppresses RANKL/M-CSF/OPG-dependent ostoclastogenesis and breast cancer growth in the metastatic bone microenvironment

Aberrant activation of fibroblast growth factor receptor (FGFR) signalling contributes to progression and metastasis of many types of cancers including breast cancer. Accordingly, FGFR targeted tyrosine kinase inhibitors (TKIs) are currently under development. However, the efficacy of FGFR TKIs in the bone microenvironment where breast cancer cells most frequently metastasize and also where FGFR is biologically active, has not been clearly investigated. We investigated the FGFR-mediated interactions among cancer and the bone microenvironment stromal cells (osteoblasts and osteoclasts), and also the effects of FGFR inhibition in bone metastasis. We showed that addition of culture supernatant from the MDA-MB-134-VI FGFR-amplified breast cancer cells-activated FGFR siganalling in osteoblasts, including increased expression of RANKL, M-CSF, and osteoprotegerin (OPG). Further in vitro analyses showed that AZD4547, an FGFR TKI currently in clinical trials for breast cancer, decreased RANKL and M-CSF, and subsequently RANKL and M-CSF-dependent osteoclastogenesis of murine bone marrow monocytes. Moreover, AZD4547 suppressed osteoclastogenesis and tumor-induced osteolysis in an orthotopic breast cancer bone metastasis mouse model using FGFR non-amplified MDA-MB-231 cells. Collectively, our results support that FGFR inhibitors inhibit the bone microenvironment stromal cells including osteoblasts and osteoclasts, and effectively suppress both tumor and stromal compartments of bone metastasis.

Imatinib mesylate does not counteract ovarian tissue fibrosis in postnatal rat ovary

Chemotherapy may result in ovarian atrophy, a depletion of the primordial follicle pool, diminished ovarian weight, cortical and stromal fibrosis. Imatinib mesylate is an anticancer agent that inhibits competitively several receptor tyrosine kinases (RTKs). RTKs play important roles in cell metabolism, proliferation, and apoptosis. In clinic, imatinib mesylate is also known as an anti-fibrotic medicine. In the present study, the impact of imatinib on the ovarian tissue was investigated by assessing ovarian tissue fibrosis in postnatal rat administered with or without imatinib for three days. Fibrosis in the ovarian tissue was determined by histology (Picrosirius and Masson's trichrome staining) and the protein expression of vimentin and alpha-smooth muscle actin (α-SMA). Furthermore, mRNA expression of Forkhead box transcription factor O1 and O3 (FOXO1 and FOXO3), which are markers of cell proliferation was quantified. A short-term exposure to imatinib showed to increase tissue fibrosis in ovaries. This was observed by Masson's trichrome staining. Exposure to imatinib led also to a down-regulation of vimentin protein expression and up-regulation mRNA expression of FOXO3. This may indicate a role of FOXO3 in ovarian tissue fibrosis in postnatal rat ovaries.

Phosphoproteomics Analysis Identifies Novel Candidate Substrates of the Nonreceptor Tyrosine Kinase, Src-related Kinase Lacking C-terminal Regulatory Tyrosine and N-terminal Myristoylation Sites (SRMS)

SRMS (Src-related kinase lacking C-terminal regulatory tyrosine and N-terminal myristoylation sites), also known as PTK 70 (Protein tyrosine kinase 70), is a non-receptor tyrosine kinase that belongs to the BRK family of kinases (BFKs). To date less is known about the cellular role of SRMS primarily because of the unidentified substrates or signaling intermediates regulated by the kinase. In this study, we used phosphotyrosine antibody-based immunoaffinity purification in large-scale label-free quantitative phosphoproteomics to identify novel candidate substrates of SRMS. Our analyses led to the identification of 1258 tyrosine-phosphorylated peptides which mapped to 663 phosphoproteins, exclusively from SRMS-expressing cells. DOK1, a previously characterized SRMS substrate, was also identified in our analyses. Functional enrichment analyses revealed that the candidate SRMS substrates were enriched in various biological processes including protein ubiquitination, mitotic cell cycle, energy metabolism and RNA processing, as well as Wnt and TNF signaling. Analyses of the sequence surrounding the phospho-sites in these proteins revealed novel candidate SRMS consensus substrate motifs. We utilized customized high-throughput peptide arrays to validate a subset of the candidate SRMS substrates identified in our MS-based analyses. Finally, we independently validated Vimentin and Sam68, as bona fide SRMS substrates through in vitro and in vivo assays. Overall, our study identified a number of novel and biologically relevant SRMS candidate substrates, which suggests the involvement of the kinase in a vast array of unexplored cellular functions.

Pharmacology and pharmacokinetics of imatinib in pediatric patients

INTRODUCTION

The tyrosine kinase inhibitor (TKI) imatinib was rationally designed to target BCR-ABL1 which is constitutively activated in chronic myeloid leukemia (CML). Following the tremendous success in adults, imatinib also became licensed for treatment of CML in minors. The rarity of pediatric CML hampers the conduction of formal trials. Thus, imatinib is still the single TKI approved for CML treatment in childhood. Areas covered: This review attempts to provide an overview of the literature on pharmacology, pharmacokinetic, and pharmacogenetic of imatinib concerning pediatric CML treatment. Articles were identified through a PubMed search and by reviewing abstracts from relevant hematology congresses. Additional information was provided from the authors' libraries and expertise and from our own measurements of imatinib trough plasma levels in children. Pharmacokinetic variables (e.g. alpha 1-acid glycoprotein binding, drug-drug/food-drug interactions via cytochrome P450 3A4/5, cellular uptake mediated via OCT-1-influx variations and P-glycoprotein-mediated drug efflux) still await to be addressed in pediatric patients systematically. Expert commentary: TKI response rates vary among different individuals and pharmacokinetic variables all can influence CML treatment success. Adherence to imatinib intake may be the most prominent factor influencing treatment outcome in teenagers thus pointing towards the potential benefits of regular drug monitoring.

Multiparameter Analysis of Off-Target Effects of Dasatinib on Bone Homeostasis in Patients With Newly Diagnosed Chronic Myelogenous Leukemia

BACKGROUND

We assessed patients with chronic myelogenous leukemia (CML) for serum calcium (Ca), phosphate (PO4), bone alkaline phosphatase, N-telopeptide (NTx), osteoprotegerin (OPG) levels, and trabecular bone area (TBA) in bone marrow (BM) specimens before and after treatment with dasatinib. We identified a significant increase in percentage of TBA in postdasatinib BM (P = .022). This suggests that dasatinib therapy can increase TBA without significant changes in bone and mineral metabolism. Interferences with bone homeostasis and mineral metabolism have been described in patients receiving imatinib for CML or gastrointestinal stromal tumors. Dasatinib is a potent second-generation tyrosine kinase inhibitor designed to inhibit ABL and SRC kinases while also interfering with the c-Kit, platelet-derived growth factor receptor, and STAT5 pathways.

PATIENTS AND METHODS

We used a multiparameter approach to examine the off-target effects of dasatinib in 30 patients with CML treated between 2009 and 2012. We recorded serum Ca and PO4 levels, analyzed markers of bone formation (bone alkaline phosphatase/bone-specific alkaline phosphatase [BAP]) and bone resorption (NTx), measured OPG levels, and digitally analyzed changes in TBA in paired BM biopsy specimens before and after treatment. We correlated all findings with each other and with the results of conventional cytogenetic and molecular analyses.

RESULTS

We identified a significant increase in the percentage of TBA in postdasatinib BM biopsy specimens (P = .022) and noted a decrease in serum OPG levels in 75% of patients. Ca, PO4, BAP, and NTx levels remained steady, without significant changes. There was no correlation between biomarker levels, percentage of TBA, and/or cytogenetic or molecular response.

CONCLUSION

These findings suggest that dasatinib therapy (within the therapeutic range) can increase trabecular bone, without causing significant changes in bone and mineral metabolism. Nonetheless, monitoring of bone health and skeletal integrity should be included into the long-term management of patients treated with dasatinib to further enhance our understanding of its safety profile and its potential role as a treatment modality for other bone diseases.

ACVR2B/Fc counteracts chemotherapy-induced loss of muscle and bone mass

Chemotherapy promotes the development of cachexia, a debilitating condition characterized by muscle and fat loss. ACVR2B/Fc, an inhibitor of the Activin Receptor 2B signaling, has been shown to preserve muscle mass and prolong survival in tumor hosts, and to increase bone mass in models of osteogenesis imperfecta and muscular dystrophy. We compared the effects of ACVR2B/Fc on muscle and bone mass in mice exposed to Folfiri. In addition to impairing muscle mass and function, Folfiri had severe negative effects on bone, as shown by reduced trabecular bone volume fraction (BV/TV), thickness (Tb.Th), number (Tb.N), connectivity density (Conn.Dn), and by increased separation (Tb.Sp) in trabecular bone of the femur and vertebra. ACVR2B/Fc prevented the loss of muscle mass and strength, and the loss of trabecular bone in femurs and vertebrae following Folfiri administration. Neither Folfiri nor ACVR2B/Fc had effects on femoral cortical bone, as shown by unchanged cortical bone volume fraction (Ct.BV/TV), thickness (Ct.Th) and porosity. Our results suggest that Folfiri is responsible for concomitant muscle and bone degeneration, and that ACVR2B/Fc prevents these derangements. Future studies are required to determine if the same protective effects are observed in combination with other anticancer regimens or in the presence of cancer.

Impaired osteoclast homeostasis in the cystatin B-deficient mouse model of progressive myoclonus epilepsy

Progressive myoclonus epilepsy of Unverricht–Lundborg type (EPM1) is an autosomal recessively inherited disorder characterized by incapacitating stimulus-sensitive myoclonus and tonic-clonic epileptic seizures with onset at the age of 6 to 16 years. EPM1 patients also exhibit a range of skeletal changes, e.g., thickened frontal cranial bone, arachnodactyly and scoliosis. Mutations in the gene encoding cystatin B (CSTB) underlie EPM1. CSTB is an inhibitor of cysteine cathepsins, including cathepsin K, a key enzyme in bone resorption by osteoclasts. CSTB has previously been shown to protect osteoclasts from experimentally induced apoptosis and to modulate bone resorption in vitro. Nevertheless, its physiological function in bone and the cause of the bone changes in patients remain unknown. Here we used the CSTB-deficient mouse (Cstb^−/−) model of EPM1 to evaluate the contribution of defective CSTB protein function on bone pathology and osteoclast differentiation and function. Micro-computed tomography of hind limbs revealed thicker trabeculae and elevated bone mineral density in the trabecular bone of Cstb^−/− mice. Histology from Cstb^−/− mouse bones showed lower osteoclast count and thinner growth plates in long bones. Bone marrow-derived osteoclast cultures revealed lower osteoclast number and size in the Cstb^−/− group. Cstb^−/− osteoclasts formed less and smaller resorption pits in an in vitro assay. This impaired resorptive capacity was likely due to a decrease in osteoclast numbers and size. These data imply that the skeletal changes in Cstb^−/− mice and in EPM1 patients are a result of CSTB deficiency leading to impaired osteoclast formation and consequently compromised resorptive capacity. These results suggest that the role of CSTB in osteoclast homeostasis and modulation of bone metabolism extends beyond cathepsin K regulation.

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μCT reveals changes in trabecular bone of the Cstb^−/− mouse model of EPM1, compatible with findings in human patients.

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Bone histology in Cstb^−/− mice shows lower osteoclast number and thinner growth plates in long bones.

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Cultured osteoclasts of Cstb^−/− mice show decreased size and number of mature osteoclasts with impaired bone resorption.

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Impaired osteoclast formation and resorption are likely to underlie the bone phenotype associated with CSTB deficiency.

Impact of long-term exposure to the tyrosine kinase inhibitor imatinib on the skeleton of growing rats

The tyrosine kinase (TK) inhibitor imatinib provides a highly effective therapy for chronic myeloid leukemia (CML) via inhibition of the oncogenic TK BCR-ABL1. However, off-target TKs like platelet-derived growth factor receptors (PDGF-R) and colony-stimulating factor-1 receptor (c-fms), involved in bone remodeling, are also inhibited. Thus, pediatric patients with CML on imatinib exhibit altered bone metabolism, leading to linear growth failure. As TKI treatment might be necessary for a lifetime, long-term effects exerted on bone in children are of major concern. Therefore, we studied the skeletal long-term effects of continuous and intermittent imatinib exposure in a juvenile rat model. Four-weeks-old male Wistar rats were chronically exposed to imatinib via drinking water over a period of 10 weeks. Animals were exposed to a standard and high imatinib dosage continuously and to the high imatinib dose intermittently. Bone mass and strength were assessed using pQCT, micro-computed tomography (μCT), and biomechanical testing at the prepubertal, pubertal, and postpubertal age. Bone length and vertebral height as well as biochemical markers of bone turnover were analyzed. Femoral and tibial bone length were dose-dependently reduced by up to 24% (p<0.0001), femoral and tibial trabecular bone mass density (BMD) were reduced by up to 25% (p<0.01), and femoral breaking strength was lowered by up to 20% (p<0.05). Intermittent exposure mitigated these skeletal effects. Long-term exposure resulted in reduced vertebral height by 15% and lower trabecular BMD by 5%. Skeletal changes were associated with suppressed serum osteocalcin (p<0.01) and non-significantly elevated serum CTX-I and PINP levels. In conclusion, imatinib mainly impaired longitudinal growth of long bones rather than the vertebrae of growing rats. Interestingly, intermittent imatinib exposure has less skeletal side effects, which may be beneficial in pediatric patients taking imatinib.

Chemotherapy- and irradiation-induced bone loss in adults with solid tumors

It is estimated that bone loss occurs in 70 % of all patients dying from cancer, causing a significant disease burden in cancer patients. Bone loss is caused by cancer itself and its metastases, but also by cancer therapies. Of the cancer therapy-induced bone loss, hormone therapies are best known for their bone damaging abilities. However, chemo- and radiotherapy may result in bone loss too. In this review, direct and indirect effects of various chemotherapies (such as methotrexate, imatinib, and taxanes) that cause bone loss are discussed. Furthermore, we discuss bone loss caused by radiotherapy and radionuclides, of which the latter may be reduced with the introduction of the alpha-emitter Radium-223. Finally, agents preventing chemotherapy- or radiotherapy-induced bone loss, in particular denosumab and bisphosphonates, are being reviewed for their efficacy in preventing chemotherapy- and irradiation-induced bone loss in cancer patients.

Cabozantinib inhibits growth of androgen-sensitive and castration-resistant prostate cancer and affects bone remodeling

Cabozantinib is an inhibitor of multiple receptor tyrosine kinases, including MET and VEGFR2. In a phase II clinical trial in advanced prostate cancer (PCa), cabozantinib treatment improved bone scans in 68% of evaluable patients. Our studies aimed to determine the expression of cabozantinib targets during PCa progression and to evaluate its efficacy in hormone-sensitive and castration-resistant PCa in preclinical models while delineating its effects on tumor and bone. Using immunohistochemistry and tissue microarrays containing normal prostate, primary PCa, and soft tissue and bone metastases, our data show that levels of MET, P-MET, and VEGFR2 are increasing during PCa progression. Our data also show that the expression of cabozantinib targets are particularly pronounced in bone metastases. To evaluate cabozantinib efficacy on PCa growth in the bone environment and in soft tissues we used androgen-sensitive LuCaP 23.1 and castration-resistant C4-2B PCa tumors. In vivo, cabozantinib inhibited the growth of PCa in bone as well as growth of subcutaneous tumors. Furthermore, cabozantinib treatment attenuated the bone response to the tumor and resulted in increased normal bone volume. In summary, the expression pattern of cabozantinib targets in primary and castration-resistant metastatic PCa, and its efficacy in two different models of PCa suggest that this agent has a strong potential for the effective treatment of PCa at different stages of the disease.

c-Abl-dependent molecular circuitry involving Smad5 and phosphatidylinositol 3-kinase regulates bone morphogenetic protein-2-induced osteogenesis

Skeletal remodeling consists of timely formation and resorption of bone by osteoblasts and osteoclasts in a quantitative manner. Patients with chronic myeloid leukemia receiving inhibitors of c-Abl tyrosine kinase often show reduced bone remodeling due to impaired osteoblast and osteoclast function. BMP-2 plays a significant role in bone generation and resorption by contributing to the formation of mature osteoblasts and osteoclasts. The effects of c-Abl on BMP-2-induced bone remodeling and the underlying mechanisms are not well studied. Using a pharmacological inhibitor and expression of a dominant negative mutant of c-Abl, we show an essential role of this tyrosine kinase in the development of bone nodules containing mature osteoblasts and formation of multinucleated osteoclasts in response to BMP-2. Calvarial osteoblasts prepared from c-Abl null mice showed the absolute requirement of this tyrosine kinase in maturation of osteoblasts and osteoclasts. Activation of phosphatidylinositol 3-kinase (PI 3-kinase)/Akt signaling by BMP-2 leads to osteoblast differentiation. Remarkably, inhibition of c-Abl significantly suppressed BMP-2-stimulated PI 3-kinase activity and its downstream Akt phosphorylation. Interestingly, c-Abl regulated BMP-2-induced osteoclastogenic CSF-1 expression. More importantly, we identified the requirements of c-Abl in BMP-2 autoregulation and the expressions of alkaline phosphatase and osterix that are necessary for osteoblast differentiation. c-Abl contributed to BMP receptor-specific Smad-dependent transcription of CSF-1, osterix, and BMP-2. Finally, c-Abl associates with BMP receptor IA and regulates phosphorylation of Smad in response to BMP-2. We propose that activation of c-Abl is an important step, which induces into two signaling pathways involving noncanonical PI 3-kinase and canonical Smads to integrate BMP-2-induced osteogenesis.

Digital image analysis as a tool to assess the effects of imatinib on trabecular bone in patients with chronic myelogenous leukemia

Skeletal integrity is sustained by osteoblast-osteoclast interactions, controlled by several signaling pathways that include tyrosine kinases. Imatinib is a tyrosine kinase inhibitor with an extended therapeutic range based on its ability to differentially bind to receptor and nonreceptor tyrosine kinases. In this study, we used digital image analysis to assess changes in trabecular bone surface area within bone marrow biopsy specimens of 34 patients with chronic phase chronic myelogenous leukemia treated with single-agent imatinib. These patients were 25 men and 9 women with a median age of 59 years. We selected representative areas of paired bone marrow biopsy specimens obtained at baseline and within the subsequent 48 months. Computer-assisted analysis was performed to calculate trabecular bone area (TBA) within the sample by using the equation TBA% = sum of trabecular area/total biopsy specimen area. Percentage changes were defined as ΔTBA% and were arbitrarily subdivided into marked (>50%), moderate (10%-50%), and mild (<10%). During the study interval, TBA% increased in 24 patients (71%) and decreased in 10 patients (29%). Overall, there was a significant increase in TBA% (P = .02). No correlation was found between changes in trabecular bone area and either clinical or cytogenetic response (P = .25). The results show that imatinib therapy can alter trabecular bone in bone marrow biopsy specimens of chronic myelogenous leukemia patients, most often resulting in an increase in TBA%.

FMS Kinase Inhibitors: Current Status and Future Prospects

FMS, first discovered as the oncogene responsible for Feline McDonough Sarcoma, is a type III receptor tyrosine kinase that binds to the macrophage or monocyte colony-stimulating factor (M-CSF or CSF-1). Signal transduction through that binding results in survival, proliferation, and differentiation of monocyte/macrophage lineage. Overexpression of CSF-1 and/or FMS has been implicated in a number of disease states such as the growth of metastasis of certain types of cancer, in promoting osteoclast proliferation in bone osteolysis, and many inflammatory disorders. Inhibition of CSF-1 and/or FMS may help treat these pathological conditions. This article reviews FMS gene, FMS kinase, CSF-1, IL-34, and their roles in bone osteolysis, cancer biology, and inflammation. Monoclonal antibodies, FMS crystal structure, and small molecule FMS kinase inhibitors of different chemical scaffolds are also reviewed.