Heme oxygenase-1 attenuates the inhibitory effect of bortezomib against the APRIL-NF-κB-CCL3 signaling pathways in multiple myeloma cells: Corelated with bortezomib tolerance in multiple myeloma

Osteoclasts (OCs) play an essential role in bone destruction in patients with multiple myeloma (MM). Bortezomib can ameliorate bone destruction in patients with MM, but advanced MM often resists bortezomib. We studied the molecular mechanisms of bortezomib tolerance in MM. The expression of the MM-related genes in newly diagnosed patients with MM and normal donors were studied. C-C motif chemokine ligand 3 (CCL3) is a cytokine involved in the differentiation of OCs, and its expression is closely related to APRIL (a proliferation-inducing ligand). We found that bortezomib treatment inhibited APRIL and CCL3. But the heme oxygenase-1 (HO-1) activator hemin attenuated the inhibitory effects of bortezomib on APRIL and CCL3. We induced mononuclear cells to differentiate into OCs, and the enzyme-linked immunosorbent assay showed that the more OCs differentiated, the higher the levels CCL3 secretions detected. Animal experiments showed that hemin promoted MM cell infiltration in mice. The weight and survival rate of tumor mice were associated with HO-1 expression. Immunohistochemical staining showed that HO-1, APRIL, and CCL3 staining were positively stained in the tumor infiltrating sites. Then, MM cells were transfected with L-HO-1/si-HO-1 expression vectors and cultured with an nuclear factor (NF)-kappa B (κB) pathway inhibitor, QNZ. The results showed that HO-1 was the upstream gene of APRIL, NF-κB, and CCL3. We showed that HO-1 could attenuate the inhibitory effect of bortezomib against the APRIL-NF-κB-CCL3 signaling pathways in MM cells, and the tolerance of MM cells to bortezomib and the promotion of bone destruction are related to HO-1.

Osteoprotegerin rich tumor microenvironment: implications in breast cancer

Osteoprotegerin (OPG) is a soluble decoy receptor for tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL). It belongs to the tumor necrosis factor receptor superfamily (TNFRSF). OPG was initially discovered to contribute to homeostasis of bone turnover due to its capability of binding to receptor activator of nuclear factor-kappaB (NF-kB). However, apart from bone turnover, OPG plays important and diverse role(s) in many biological functions. Besides having anti-osteoclastic activity, OPG is thought to exert a protective anti-apoptotic action in OPG-expressing tumors by overcoming the physiologic mechanism of tumor surveillance exerted by TRAIL. Along with inhibiting TRAIL induced apoptosis, it can induce proliferation by binding to various cell surface receptors and thus turning on the canonical cell survival and proliferative pathways. OPG also induces angiogenesis, one of the hallmarks of cancer, thus facilitating tumor growth. Recently, the understanding of OPG and its different roles has been augmented substantially. This review is aimed at providing a very informative overview as to how OPG affects cancer progression especially breast cancer.

Osteoprotegerin: A novel biomarker for inflammatory bowel disease and gastrointestinal carcinoma

Osteoprotegerin (OPG) is a member of the tumor necrosis factor receptor superfamily of proteins. Although initial data illustrated the key role that OPG plays in bone turnover, numerous recent reports indicate that OPG is also an important factor in inflammatory pathways and tumor cell survival. OPG contributes directly to inflammatory processes and has been evaluated as a novel non-invasive biomarker of gut inflammation. Furthermore, OPG affects cell turn-over, differentiation, death, and survival via extracellular pathways, correlating with worse prognosis in inflammatory bowel diseases and several gastrointestinal carcinomas. It is now clear that OPG has multiple functions and characteristics. This review gives an overview of OPG, highlights its roles in different extracellular pathways, and outlines how OPG could be used as a novel non-invasive biological marker in inflammatory bowel diseases and gastrointestinal carcinomas.