The role of RANK and RANKL in hormone-driven breast cancer

Weltweit ist Brustkrebs eine der häufigsten Krebsarten und zählt unter Frauen zu einer der führenden Todesursachen (Ferlay et al., 2007; Jemal et al., 2009). Viele Faktoren sind bekannt, die zur Entstehung und zur Progression von Brustkrebs beitragen. Auch Geschlechtshormone, wie Östrogene und Progesteron spielen eine kritische Rolle in manchen Brustkrebsarten. Kürzlichen Berichten zufolge ist die Wahrscheinlichkeit für Frauen, die sich einer Hormonersatztherapie unterziehen, grösser an Brustkrebs zu erkranken. Im speziellen werden syntethische Progesterone-Derivate (Progestine) wie Medroxyprogesteron Acetat (MPA) welches Millionen Frauen in Form von Hormonersatztherapeutika und hormonelle Kontrazeptiva zu sich nehmen, mit diesem erhöhten Brustkrebsrisiko in Verbindung gebracht. Trotzdem sind die genauen molekularen Mechanismen, welche Rolle Progestine in Brustkrebs spielen, noch wenig verstanden. Rezeptor Aktivator von NFkappaB (RANK) und sein Ligand RANKL sind essentielle Regulatoren für die Differenzierung und Funktion von Osteoklasten. Unfraglich hat die Entdeckung dieser Moleküle erheblich dazu beigetragen die molekularen Mechanismen im Knochenstoffwechsel und von Knochenerkrankungen besser zu verstehen. Außerdem sind RANK und RANKL auch wesentliche Faktoren für die der Entwicklung der Brustdrüsen während der Schwangerschaft. Über hormonelle Regulation und die Aktivierung von Id2 (Kim et al., 2006), NFkappaB und CyclinD1 (Cao et al., 2001) induzieren RANK und RANKL die Proliferation und Differenzierung von terminalen Endknospen zu lobuloalveolaren Strukturen. Interessanterweise berichten wir hier, dass die in vivo Verabreichung von Medroxyprogesteron Acetat zu einer Hochregulierung der RANKL-Expression in weiblichen Mäusen führt. Außerdem zeigen wir, dass die gewebsspezifische Inaktivierung von RANK in Brustepithelzellen nach Progesteron/DMBA Adminsitration zu einer signifikant späteren Entstehung von Brusttumoren führt. Auf molekularer Ebene scheint es, als ob die Inaktivierung von RANK in einer Beeinträchtigung von Id2 und NFkappaB und somit in einem Proliferationsblock resultiert. Weiters konnten wir beobachten dass die MPA-induzierte Expression von RANKL Brustepithelialzellen vor dem programmierten Zelltod induziert durch gamma-Bestrahlung schützt. Dies stellt eine Prärequisite für die Entstehung von Krebs dar. Zusammenfassend zeigen wir hier zum ersten Mal, dass RANK und RANKL, bekannt als Schlüsselmoleküle im Knochenmetabolismus auch die Entstehung von hormonabhänigigen primärem Brustkrebs kontrollieren.Worldwide, breast cancer is one of the most common cancers and a leading death cause amongst women (Ferlay et al., 2007; Jemal et al., 2009). Many factors contribute to the development and progression of breast cancer. Interestingly, sex hormones such as estrogen and progesterone are well known factors critically involved in mammary tumorigenesis and recently it has been shown that women undergoing combined hormonal replacement therapy (HRT) have an increased risk of developing breast cancer. In particular, synthetic progesterone derivatives like medroxyprogesterone acetate (MPA) which are widely used by millions of women in the form of HRT and contraceptives appear to markedly increase the risk of developing breast cancer (Beral, 2003; Rossouw et al., 2002). However, the mechanism how MPA is linked to breast cancer on a molecular level is still poorly understood. Receptor activator of NFkappaB (RANK) and its ligand RANKL are essential and central regulators of osteoclast differentiation and osteoclast function (Kong et al., 1999b). The discovery of these molecules has unquestionably significantly contributed to the understanding of the molecular mechanisms of normal bone metabolism and bone disease. Moreover RANK and RANKL are also crucial in pregnancy-dependent mammary gland formation (Fata et al., 2000). Embedded in a hormonal regulatory network the RANK/RANKL pathway initiates proliferation and differentiation of terminal end buds to lobuloalveolar structures via activation of the Id2 pathway (Kim et al., 2006) and the NFkappaB – CyclinD1 axis (Cao et al., 2001). Intriguingly, we here report that in vivo MPA administration results in massive upregulation of RANKL expression in female mice. Most importantly, we show that tissue specific inactivation of RANK in mammary epithelial cells results in a significantly delayed onset of breast cancer in response to MPA/DMBA treatment. On a molecular level it appears that loss of RANK leads to impaired NFkappaB and Id2 activation resulting in a block in proliferation. Moreover we observed that MPA-induced RANKL expression protects of gamma-irradiation-induced cell death, thus providing a prerequisite for the development of cancer. These data provide the first demonstration that RANK/RANKL control the development of hormone-driven breast cancer

RANKL/RANK control Brca1 mutation-driven mammary tumors

Breast cancer is the most common female cancer, affecting approximately one in eight women during their life-time. Besides environmental triggers and hormones, inherited mutations in the breast cancer 1 (BRCA1) or BRCA2 genes markedly increase the risk for the development of breast cancer. Here, using two different mouse models, we show that genetic inactivation of the key osteoclast differentiation factor RANK in the mammary epithelium markedly delayed onset, reduced incidence, and attenuated progression of Brca1;p53 mutation-driven mammary cancer. Long-term pharmacological inhibition of the RANK ligand RANKL in mice abolished the occurrence of Brca1 mutation-driven pre-neoplastic lesions. Mechanistically, genetic inactivation of Rank or RANKL/RANK blockade impaired proliferation and expansion of both murine Brca1;p53 mutant mammary stem cells and mammary progenitors from human BRCA1 mutation carriers. In addition, genome variations within the RANK locus were significantly associated with risk of developing breast cancer in women with BRCA1 mutations. Thus, RANKL/RANK control progenitor cell expansion and tumorigenesis in inherited breast cancer. These results present a viable strategy for the possible prevention of breast cancer in BRCA1 mutant patients

The stress kinase MKK7 couples oncogenic stress to p53 stability and tumor suppression. Nature Genet

A r t i c l e s JNK kinases (JNK1, 2 and 3) are required for cells to respond to their extracellular environment and regulate many physiological processes such as proliferation, apoptosis, differentiation and inflammation 1 . The JNK kinase pathway has also been implicated in tumorigenesis 2 . However, both tumor-promoting and tumor-suppressive functions have been reported RESULTS Conditional deletion of Map2k7 To investigate the role of MKK7 and MKK7-regulated activation of JNK in tumorigenesis, we generated a new mouse line that carries a conditional Map2k7 (also known as Mkk7) allele (Map2k7 floxed ; Prolonged survival in MKK7 deficient KRas G2D lung tumors To test the role of MKK7 in lung cancer driven by the inducible oncogenic KRas G12D allele, we crossed Map2k7 floxed/∆ mice with a Lox-Stop-Lox-KRas G12D strain (termed KRas; Map2k7 fl/∆ hereafter). Lox-Stop-Lox-KRas G12D mice rapidly develop non-small-cell lung carcinomas (NSCLCs) after induction of the KRas G12D allele 12 . We achieved expression of KRas G12D and deletion of exons 3-10 of Map2k7 by adenoviral delivery of Cre recombinase through inhalation (AdCre

RANK links thymic regulatory T cells to fetal loss and gestational diabetes in pregnancy

Successful pregnancies rely on adaptations within the mother(1), including marked changes within the immune system(2). It has long been known that the thymus, the central lymphoid organ, changes markedly during pregnancy(3). However, the molecular basis and importance of this process remain largely obscure. Here we show that the osteoclast differentiation receptor RANK(4,5) couples female sex hormones to rewiring of the thymus during pregnancy. Genetic deletion of Rank (also known as Tnfrsf11a) in thymic epithelial cells results in impaired thymic involution and blunted expansion of natural regulatory T (T(reg)) cells in pregnant female mice. Sex hormones, in particular progesterone, drive the development of thymic T(reg) cells through RANK in a manner that depends on AIRE(+) medullary thymic epithelial cells and depletion of Rank in the thymic epithelium results in reduced accumulation of natural T(reg) cells in the placenta, accompanied by an increased number of miscarriages. Thymic deletion of Rank also resulted in impaired accumulation of T(reg) cells in visceral adipose tissue, associated with enlarged adipocyte size, tissue inflammation, enhanced maternal glucose intolerance, fetal macrosomia, and a long-lasting transgenerational alteration in glucose homeostasis; key hallmarks of gestational diabetes. Transplantation of T(reg) cells rescued fetal loss, maternal glucose intolerance and fetal macrosomia. In human pregnancies, gestational diabetes also correlates with a reduced number of T(reg) cells in the placenta. Our findings show that RANK promotes the hormone-mediated development of thymic T(reg) cells during pregnancy and expand the functional role of maternal T(reg) cells to gestational diabetes and the transgenerational metabolic rewiring of glucose homeostasis

RANK rewires energy homeostasis in lung cancer cells and drives primary lung cancer

Lung cancer is the leading cause of cancer deaths. Besides smoking, epidemiological studies have linked female sex hormones to lung cancer in women; however, the underlying mechanisms remain unclear. Here we report that the receptor activator of nuclear factor-kB (RANK), the key regulator of osteoclastogenesis, is frequently expressed in primary lung tumors, an active RANK pathway correlates with decreased survival, and pharmacologic RANK inhibition reduces tumor growth in patient-derived lung cancer xenografts. Clonal genetic inactivation of KRas(G12D) in mouse lung epithelial cells markedly impairs the progression of KRas(G12D)-driven lung cancer, resulting in a significant survival advantage. Mechanistically, RANK rewires energy homeostasis in human and murine lung cancer cells and promotes expansion of lung cancer stem-like cells, which is blocked by inhibiting mitochondrial respiration. Our data also indicate survival differences in KRas(G12D)-driven lung cancer between male and female mice, and we show that female sex hormones can promote lung cancer progression via the RANK pathway. These data uncover a direct role for RANK in lung cancer and may explain why female sex hormones accelerate lung cancer development. Inhibition of RANK using the approved drug denosumab may be a therapeutic drug candidate for primary lung cancer