SOCS-1/3 participation in FGF-2 signaling to modulate RANK ligand expression in paget's disease of bone

Kremen2 drives the progression of non-small cell lung cancer by preventing SOCS3-mediated degradation of EGFR

BACKGROUND

The transmembrane receptor Kremen2 has been reported to participate in the tumorigenesis and metastasis of gastric cancer. However, the role of Kremen2 in non-small cell lung cancer (NSCLC) and the underlying mechanism remain unclear. This study aimed to explore the biological function and regulatory mechanism of Kremen2 in NSCLC.

METHODS

The correlation between Kremen2 expression and NSCLC was assessed by analyzing the public database and clinical tissue samples. Colony formation and EdU assays were performed to examine cell proliferation. Transwell and wound healing assays were used to observe cell migration ability. Tumor-bearing nude mice and metastatic tumor models were used to detect the in vivo tumorigenic and metastatic abilities of the NSCLC cells. An immunohistochemical assay was used to detect the expression of proliferation-related proteins in tissues. Western blot, immunoprecipitation and immunofluorescence were conducted to elucidate the Kremen2 regulatory mechanisms in NSCLC.

RESULTS

Kremen2 was highly expressed in tumor tissues from NSCLC patients and was positively correlated with a poor patient prognosis. Knockout or knockdown of Kremen2 inhibited cell proliferation and migration ability of NSCLC cells. In vivo knockdown of Kremen2 inhibited the tumorigenicity and number of metastatic nodules of NSCLC cells in nude mice. Mechanistically, Kremen2 interacted with suppressor of cytokine signaling 3 (SOCS3) to maintain the epidermal growth factor receptor (EGFR) protein levels by preventing SOCS3-mediated ubiquitination and degradation of EGFR, which, in turn, promoted activation of the PI3K-AKT and JAK2-STAT3 signaling pathways.

CONCLUSIONS

Our study identified Kremen2 as a candidate oncogene in NSCLC and may provide a potential target for NSCLC treatment.

Clinical and Microstructural Findings in Paget Disease of the Entire Mandible

Paget disease of bone (PDB) is a chronic progressive bone disorder characterized by localized increased bone turnover and focal areas of woven bone formation. Although skull involvement is common, PDB very rarely affects the mandible. This report describes the clinical and histologic findings in a 75-year-old patient with PDB involving the mandible. Microstructural analyses showed an altered quality of the bone microstructure and calcium depletion of the affected bone. Differential diagnosis of PDB affecting the mandible is discussed.

SOCS proteins in regulation of receptor tyrosine kinase signaling

Receptor tyrosine kinases (RTKs) are a family of cell surface receptors that play critical roles in signal transduction from extracellular stimuli. Many in this family of kinases are overexpressed or mutated in human malignancies and thus became an attractive drug target for cancer treatment. The signaling mediated by RTKs must be tightly regulated by interacting proteins including protein-tyrosine phosphatases and ubiquitin ligases. The suppressors of cytokine signaling (SOCS) family proteins are well-known negative regulators of cytokine receptors signaling consisting of eight structurally similar proteins, SOCS1-7, and cytokine-inducible SH2-containing protein (CIS). A key feature of this family of proteins is the presence of an SH2 domain and a SOCS box. Recent studies suggest that SOCS proteins also play a role in RTK signaling. Activation of RTK results in transcriptional activation of SOCS-encoding genes. These proteins associate with RTKs through their SH2 domains and subsequently recruit the E3 ubiquitin machinery through the SOCS box, and thereby limit receptor stability by inducing ubiquitination. In a similar fashion, SOCS proteins negatively regulate mitogenic signaling by RTKs. It is also evident that RTKs can sometimes bypass SOCS regulation and SOCS proteins can even potentiate RTKs-mediated mitogenic signaling. Thus, apart from negative regulation of receptor signaling, SOCS proteins may also influence signaling in other ways.

Pathobiology of Paget's Disease of Bone

Paget's disease of bone is characterized by highly localized areas of increased bone resorption accompanied by exuberant, but aberrant new bone formation with the primary cellular abnormality in osteoclasts. Paget's disease provides an important paradigm for understanding the molecular mechanisms regulating both osteoclast formation and osteoclast-induced osteoblast activity. Both genetic and environmental etiologies have been implicated in Paget's disease, but their relative contributions are just beginning to be defined. To date, the only gene with mutations in the coding region linked to Paget's disease is sequestosome-1 (SQSTM1), which encodes the p62 protein, and these mutations lead to elevated cytokine activation of NF-B in osteoclasts but do not induce a "pagetic osteoclast" phenotype. Further, genetic mutations linked to Paget's appear insufficient to cause Paget's disease and additional susceptibility loci or environmental factors may be required. Among the environmental factors suggested to induce Paget's disease, chronic measles (MV) infection has been the most studied. Expression of the measles virus nucleocapsid gene (MVNP) in osteoclasts induces pagetic-like osteoclasts and bone lesions in mice. Further, mice expressing both MVNP in osteoclasts and germline mutant p62 develop dramatic pagetic bone lesions that were strikingly similar to those seen in patients with Paget's disease. Thus, interactions between environmental and genetic factors appear important to the development of Paget's disease. In this article we review the mechanisms responsible for the effects of mutant p62 gene expression and MVNP on osteoclast and osteoblast activity, and how they may contribute to the development of Paget's disease of bone.