- Not to be confused with RANK, the osteoclast cell-surface receptor that binds to RANKL.
Receptor activator of nuclear factor kappa-B ligand (RANKL), also known as tumor necrosis factor ligand superfamily member 11 (TNFSF11), TNF-related activation-induced cytokine (TRANCE), osteoprotegerin ligand (OPGL), and osteoclast differentiation factor (ODF), is a protein that in humans is encoded by the TNFSF11 gene.[1][2]
RANKL is known as a type II membrane protein and is a member of the tumor necrosis factor (TNF) superfamily.[3] RANKL has been identified to affect the immune system and control bone regeneration and remodeling. RANKL may be used as an apoptosis regulator gene, a binding partner of OPG, a ligand for the receptor RANK and control proliferation by modifying protein levels of Id4, Id2 and cyclin D1.[4][5] RANKL is expressed in several tissues and organs including: skeletal muscle, thymus, liver, colon, small intestine, adrenal gland, osteoclast, mammary gland epithelial cells, prostate and pancreas.[5] Variation in concentration levels of RANKL throughout several organs, reconfirm the uses and importance of growth (particularly bone growth) and immune functions within the body.
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Tissue expression[edit]
The level of RANKL expression does not linearly correlate to the effect of this ligand. High protein expression of RANKL are commonly detected in the lung, thymus and lymph nodes, and low protein expression is found in bone marrow, stomach, peripheral blood, spleen, placenta, leukocytes, heart, thyroid and skeletal muscle.[5] While bone marrow expresses low levels of RANKL, it plays a critical role for adequate bone metabolism, this surface-bound molecule (also known as CD254) found on osteoblasts serves to activate osteoclasts, which are critically involved in bone resorption. Osteoclastic activity is triggered via the osteoblasts' surface-bound RANKL activating the osteoclasts' surface-bound receptor activator of nuclear factor kappa-B (RANK).
Gene and expression[edit]
RANKL can be expressed in three different molecular forms consisting of either a: (1) trimeric transmembrane protein, (2) primary secreted form, and (3) truncated ectodomain.[6] RANKL is identified as a part of the TNF family; RANKL is specifically categorized under the TNFSF11, the TNF ligand superfamily member. RANKL is composed of 314 amino acids and was originally described to have a gene sequence containing 5 exons.[7][8] Among the exons, Exon 1 encoded the intracellular and transmembrane protein domains and Exon 2-5 encoded the extracellular domains.[7] RANKL’s extracellular domains are similar to other TNF family members in regards to the structural homology and are able to cleave from the cell surface.[7] While the function and significance of A kinase anchor protein 11(AKAP11) is presently unknown, AKAP11 is immediately upstream from RANKL for all species that has a RANKL gene.[8] The upstream of AKAP11 may suggest there is a complex regulator process that regulates the level of RANKL expression.
Function[edit]
Since RANKL is a member of the tumor necrosis factor (TNF) cytokine family, it is a ligand for osteoprotegerin and functions as a key factor for osteoclast differentiation and activation. RANKL also has a function in the immune system, where it is expressed by T helper cells and is thought to be involved in dendritic cell maturation. This protein was shown to be a dendritic cell survival factor and is involved in the regulation of T cell-dependent immune response. T cell activation was reported to induce expression of this gene and lead to an increase of osteoclastogenesis and bone loss. This protein was shown to activate antiapoptotic kinase AKT/PKB through a signaling complex involving SRC kinase and tumor necrosis factor receptor-associated factor 6 (TRAF6), which indicated this protein may have a role in the regulation of cell apoptosis.[9]
Animal models[edit]
Targeted disruption of the related gene in mice led to severe osteopetrosis and a lack of osteoclasts. Deficient mice, with an inactivation of RANKL or its receptor RANK, exhibited defects in early differentiation of T and B lymphocytes, and failed to form lobulo-alveolar mammary structures during pregnancy.[5][9] It was observed that during pregnancy, RANK-RANKL signaling played a critical role in regulating skeletal calcium release; in which contributed to the hormone response that stimulated proliferation in the mammary cells.[5] Ultimately, impaired lobuloalveolar mammary structures resulted in death of the fetus.[5] Those who suffer from osteoporosis often have a cardiovascular defect, such as heart failure. Some studies suggest, since RANK-RANKL pathway regulates calcium release and homeostasis, RANK-RANKL signal could invertedly affect the cardiovascular system; thus, an explanation for the positive correlation between osteoporosis and cardiovascular deficiencies.[5]
Role in cancer[edit]
Primary tumors will commonly metastasize into the bone. Myeloma, Breast, and prostate cancers typically have a greater chance of inducing secondary cancers within bone.[10] Stephen Paget's seed and soil theory suggests, the microenvironment in bone creates a sufficient ‘soil’ for secondary tumors to grow in. Some studies suggest the expression of RANKL allows sufficient micro environmental conditions to influence cancer cell migration (i.e. chronic lymphocytic leukemia (CLL) and multiple myeloma).[11] Among patients with multiple myeloma, RANKL activity was greatly increased. In fact RANKL’s surface expression and RANKL release expression was reported to be an increase of, respectively, 80% and 50%.[11] Therefore, RANKL is considered to be a key signal regulator for cancer-induce bone diseases.
According to the vicious cycle hypothesis, after secondary tumors cells have migrated to bone, the tumor cell will secrete cytokines and growth factors to osteoblast. Since osteoblast control the regulation of RANKL, the stimulation via cytokines and growth factors, will then stimulate osteoblasts to increase the expression of RANKL. The additional binding of RANK/RANKL within an osteoclast will secrete tumor growth factor, which can ultimately increase tumor growth and bone destruction activity.
Clinical significance[edit]
Through the binding of RANKL, osteoclasts and osteoblasts play a vital role in normal bone remodeling. Overproduction of RANKL is implicated in a variety of degenerative bone diseases, such as rheumatoid arthritis and psoriatic arthritis. In addition to degenerative bone diseases, bone metastases can also induce pain and other abnormal health complexities that can significantly reduce a cancer patient’s quality of life. Some examples of these complications that are a consequence of bone metastasis are: hypercalcemia, pathological fractures and spinal cord compression.[12] Some findings also suggestion some cancers cells, particularly prostate cancer cells, can activate an increase in bone remodeling and ultimately increase overall bone production.[12] This increase in bone remodeling and bone production increases the overall growth of bone metastasizes. The overall control of bone remodeling is regulated by the binding of RANK with its receptor or its decoy receptor, respectively, RANKL and OPG.[12]
Denosumab[edit]
Denosumab is an FDA-approved fully human monoclonal antibody to RANKL and during pre-clinical trials was first used to treat postmenopausal patients suffering with osteoporosis (PMO).[12][13] In denosumab's third stage of the FDA's clinical trial, it was shown to: (1) decrease bone turnover, (2) reduce fractures in the PMO population, and (3) increase bone mineral density.[12] Since then the anti-RANKL antibody, denosumab, has been used in some cancer clinical trials. In both prostate and breast cancer, denosumab has been shown to reduce cancer treatment–induced bone loss.[12]
Prostate cancer[edit]
The HALT-prostate cancer trial (also known as NCT00089674) included 1468 non-metastatic prostate cancer patients who were currently receiving androgen deprivation therapy.[14] Randomly selected patients were given either 60 mg of denosumab or calcium and vitamin D supplements. This was done to measure the effectiveness of preventing treatment-induced bone loss.[12] The patients who received 60 mg of denosumab showed a +5.6% increased in bone mineral density and a 1.5% decrease in bone fracture rates.[12]
Another clinical trial (NCT00321620) was established to determine the safety and effectiveness of using denosumab compared to zoledronic acid.[15] In this trial, they used 1901 bone metastatic prostate patients whom were also suffering with other complication of bone diseases. Again, patients were randomized and some were given either 120 mg of denosumab or 4 mg of zoledronic acid.[12] Patients who were given 120 mg of denosumab (in comparison to those who were given 4 mg of zoledronic acid) show an greater increase in hypocalcemia, a greater resistance to bone turnover markers uNTx, a delay response in both pathological fractures and spinal cord compression.[12] However, survival rates for both clinical groups were comparable.[12]
Breast cancer[edit]
Hormone receptor positive breast cancer patients have a significant increased in developing complications such as osteopenia and osteoporosis. According to cancer.org, about two out of every three breast cancer patients are hormone receptor positive.[16] In the past several years, denosumab has been used in several clinical trials primarily because a much large population is affected by bone complication among those who have breast cancer.
There were 252 breast cancer patients enlisted in the HALT-BC clinical trial (also known as NCT00089661). In addition to receiving vitamin D and calcium supplements, half of the patients were randomly given 60 mg of denosumab while the other half were given a placebo.[12][17] In comparison, patients who were given denosumab had an increase in lumbar spine bone mineral density, a decrease in bone turnover markers; however there was not a significant change in survival rates.[12]
Another phase III clinical trial for breast cancer patients was conducted and was known as the NCT00321464 trial.[18] Similar to the prostate trial NCT00321620, this trial was conducted to measure the safety and efficacy of using denosumab compared to zoledronic acid. Patients were randomized into two groups, one who received zoledronic acid and the other group received denosumab. When comparing survival rates and the frequency of adverse events, both groups show similar outcomes.[12]
Multiple myeloma[edit]
Patients whom are diagnosed with multiple myeloma have approximately 80-100% chance of developing bone complications due to an increase in activity and/or formation of osteoclasts and a decrease activity of osteoblasts.[11][12] In a stage II clinical trial, denosumab had decrease bone turnover markers by blocking the RANKL/RANK pathway.[12] Once this trial was completed, 1176 patients with either multiple myeloma or progressed cancers were entered into the stage III clinical trial (known as NCT00330759).[19] The main objective of the NCT00330759 trial was to compare effects of patients who were given 120 mg of denosumab relative to patients give 4 mg of zoledronic acid. As a result of this trial, during a month period, patients who received denosumab had a decrease in pathological fractures and spinal cord compression; however, as time progressed it appear that denosumab had significantly delayed bone complications.[12] Similar to both breast and prostate cancers, patients in either denosumab or zoledronic acid groups appear to have compare adverse events and survival rates.[12]
Medroxyprogesterone acetate[edit]
Women with menopause have often been given various types of postmenopausal hormone therapies to prevent osteoporosis and reduce menopausal symptoms.[20] Medroxyprogesterone acetate (MPA) is a synthetic progestin and was commonly used as a contraceptive or used as a hormone therapy for endometriosis or osteoporosis. Recent studies suggest, using MPA increases patient risks of developing breast cancer due to an increase expression of RANKL.[20] MPA causes a substantial induction of RANKL in mammary-gland epithelial cells while deletion of RANKL decreases the incidence MPA-induced breast cancer. Hence inhibition of RANKL has potential for the prevention and treatment of breast cancer.[21][22]
See also[edit]
References[edit]
- ^ Wong BR, Rho J, Arron J, Robinson E, Orlinick J, Chao M, Kalachikov S, Cayani E, Bartlett FS, Frankel WN, Lee SY, Choi Y (October 1997). "TRANCE is a novel ligand of the tumor necrosis factor receptor family that activates c-Jun N-terminal kinase in T cells". J. Biol. Chem. 272 (40): 25190–4. doi:10.1074/jbc.272.40.25190. PMID 9312132.
- ^ Anderson DM, Maraskovsky E, Billingsley WL, Dougall WC, Tometsko ME, Roux ER, Teepe MC, DuBose RF, Cosman D, Galibert L (November 1997). "A homologue of the TNF receptor and its ligand enhance T-cell growth and dendritic-cell function". Nature 390 (6656): 175–9. doi:10.1038/36593. PMID 9367155.
- ^ Hanada R, Hanada T, Sigl V, Schramek D, Penninger JM (2011). "RANKL/RANK-beyond bones". J. Mol. Med. 89 (7): 647–56. doi:10.1007/s00109-011-0749-z. PMID 21445556.
- ^ Mueller CG, Hess E (2012). "Emerging Functions of RANKL in Lymphoid Tissues". Front Immunol 3: 261. doi:10.3389/fimmu.2012.00261. PMC 3432452. PMID 22969763.
- ^ a b c d e f g Wada T, Nakashima T, Hiroshi N, Penninger JM (2006). "RANKL-RANK signaling in osteoclastogenesis and bone disease". Trends Mol Med 12 (1): 17–25. doi:10.1016/j.molmed.2005.11.007. PMID 16356770.
- ^ Findlay DM, Atkins GJ (2011). "Relationship between serum RANKL and RANKL in bone". Osteoporos Int 22 (10): 2597–602. doi:10.1007/s00198-011-1740-9. PMID 21850548.
- ^ a b c Walsh NC, Alexander KA, Manning CA, Karmakar S, Karmakar SK, Wang JF, Weyand CM, Pettit AR, Gravallese EM (2013). "Activated human T cells express alternative mRNA transcripts encoding a secreted form of RANKL". Genes Immun. 14 (5): 336–45. doi:10.1038/gene.2013.29. PMC 3740552. PMID 23698708.
- ^ a b O'Brien CA (2010). "Control of RANKL gene expression". Bone 46 (4): 911–9. doi:10.1016/j.bone.2009.08.050. PMC 2842447. PMID 19716455.
- ^ a b "Entrez Gene: TNFSF11 tumor necrosis factor (ligand) superfamily, member 11".
- ^ Coleman RE (2001). "Metastatic bone disease: clinical features, pathophysiology and treatment strategies". Cancer Treat. Rev. 27 (3): 165–76. doi:10.1053/ctrv.2000.0210. PMID 11417967.
- ^ a b c Schmiedel BJ, Scheible CA, Nuebling T, Kopp HG, Wirths S, Azuma M, Schneider P, Jung G, Grosse-Hovest L, Salih HR (2013). "RANKL expression, function, and therapeutic targeting in multiple myeloma and chronic lymphocytic leukemia". Cancer Res. 73 (2): 683–94. doi:10.1158/0008-5472.CAN-12-2280. PMID 23139212.
- ^ a b c d e f g h i j k l m n o p q r Castellano D, Sepulveda JM, García-Escobar I, Rodriguez-Antolín A, Sundlöv A, Cortes-Funes H (2011). "The role of RANK-ligand inhibition in cancer: the story of denosumab". Oncologist 16 (2): 136–45. doi:10.1634/theoncologist.2010-0154. PMC 3228090. PMID 21285392.
- ^ Miller PD (2009). "Denosumab: anti-RANKL antibody". Curr Osteoporos Rep 7 (1): 18–22. PMID 19239825.
- ^ "AMG 162 in the Treatment of Bone Loss in Subjects Undergoing Androgen-Deprivation Therapy for Non-metastatic Prostate Cancer". NCT00089674. ClinicalTrials.gov.
- ^ "Study of Denosumab vs. Zoledronic Acid to Treat Bone Metastases in Men With Hormone-refractory Prostate Cancer". NCT00321620. ClinicalTrials.gov.
- ^ "Hormone therapy for breast cancer". Cancer.org. Retrieved 2014-01-31.
- ^ "AMG 162 in the Treatment of Bone Loss in Subjects Undergoing Aromatase Inhibitor Therapy for Non-metastatic Breast Cancer". NCT00089661. ClinicalTrials.gov.
- ^ "A Study Comparing Denosumab vs. Zoledronic Acid for the Treatment of Bone Metastases in Breast Cancer Subjects". NCT00321464. ClinicalTrials.gov.
- ^ "Study of Denosumab vs. Zoledronic Acid to Treat Bone Metastases in Subjects With Advanced Cancer or Multiple Myeloma". NCT00330759. ClinicalTrials.gov.
- ^ a b Wood CE, Branstetter D, Jacob AP, Cline JM, Register TC, Rohrbach K, Huang LY, Borgerink H, Dougall WC (2013). "Progestin effects on cell proliferation pathways in the postmenopausal mammary gland". Breast Cancer Res. 15 (4): R62. doi:10.1186/bcr3456. PMC 3978455. PMID 23938070.
- ^ Schramek D, Leibbrandt A, Sigl V, Kenner L, Pospisilik JA, Lee HJ, Hanada R, Joshi PA, Aliprantis A, Glimcher L, Pasparakis M, Khokha R, Ormandy CJ, Widschwendter M, Schett G, Penninger JM (November 2010). "Osteoclast differentiation factor RANKL controls development of progestin-driven mammary cancer". Nature 468 (7320): 98–102. doi:10.1038/nature09387. PMC 3084017. PMID 20881962.
- ^ Gonzalez-Suarez E, Jacob AP, Jones J, Miller R, Roudier-Meyer MP, Erwert R, Pinkas J, Branstetter D, Dougall WC (November 2010). "RANK ligand mediates progestin-induced mammary epithelial proliferation and carcinogenesis". Nature 468 (7320): 103–7. doi:10.1038/nature09495. PMID 20881963.
Further reading[edit]
- Whyte M (2006). "The long and the short of bone therapy". N Engl J Med 354 (8): 860–3. doi:10.1056/NEJMe068003. PMID 16495400. link
- Buckley KA, Fraser WD (2003). "Receptor activator for nuclear factor kappaB ligand and osteoprotegerin: regulators of bone physiology and immune responses/potential therapeutic agents and biochemical markers.". Ann. Clin. Biochem. 39 (Pt 6): 551–6. doi:10.1258/000456302760413324. PMID 12564836.
- Jeffcoate W (2005). "Vascular calcification and osteolysis in diabetic neuropathy-is RANK-L the missing link?". Diabetologia 47 (9): 1488–92. doi:10.1007/s00125-004-1477-5. PMID 15322748.
- Collin-Osdoby P (2005). "Regulation of vascular calcification by osteoclast regulatory factors RANKL and osteoprotegerin.". Circ. Res. 95 (11): 1046–57. doi:10.1161/01.RES.0000149165.99974.12. PMID 15564564.
- Whyte MP, Mumm S (2005). "Heritable disorders of the RANKL/OPG/RANK signaling pathway.". Journal of musculoskeletal & neuronal interactions 4 (3): 254–67. PMID 15615493.
- Clohisy DR, Mantyh PW (2005). "Bone cancer pain and the role of RANKL/OPG.". Journal of musculoskeletal & neuronal interactions 4 (3): 293–300. PMID 15615497.
- Anandarajah AP, Schwarz EM (2006). "Anti-RANKL therapy for inflammatory bone disorders: Mechanisms and potential clinical applications.". J. Cell. Biochem. 97 (2): 226–32. doi:10.1002/jcb.20674. PMID 16240334.
- Baud'huin M, Duplomb L, Ruiz Velasco C, Fortun Y, Heymann D, Padrines M (2007). "Key roles of the OPG-RANK-RANKL system in bone oncology.". Expert Rev Anticancer Ther 7 (2): 221–32. doi:10.1586/14737140.7.2.221. PMID 17288531.
- Yogo K, Ishida-Kitagawa N, Takeya T (2007). "Negative autoregulation of RANKL and c-Src signaling in osteoclasts.". J. Bone Miner. Metab. 25 (4): 205–10. doi:10.1007/s00774-007-0751-2. PMID 17593489.
- Boyce BF, Xing L (2007). "Biology of RANK, RANKL, and osteoprotegerin.". Arthritis Res. Ther. 9 Suppl 1: S1. doi:10.1186/ar2165. PMC 1924516. PMID 17634140.
- McClung M (2007). "Role of RANKL inhibition in osteoporosis.". Arthritis Res. Ther. 9 Suppl 1: S3. doi:10.1186/ar2167. PMC 1924518. PMID 17634142.
External links[edit]
- RANKL Signaling Pathway
- RANKL Protein at the US National Library of Medicine Medical Subject Headings (MeSH)
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This article incorporates text from the United States National Library of Medicine, which is in the public domain.