Loss of estrogens or androgens increases the rate of bone remodeling by removing restraining effects on osteoblastogenesis and osteoclastogenesis, and also causes a focal imbalance between resorption and formation by prolonging the lifespan of osteoclasts and shortening the lifespan of osteoblasts. Conversely, androgens, as well as estrogens, maintain cancellous bone mass and integrity, regardless of age or sex. Although androgens, via the androgen receptor (AR), and estrogens, via the estrogen receptors (ERs), can exert these effects, their relative contribution remains uncertain. Recent studies suggest that androgen action on cancellous bone depends on (local) aromatization of androgens into estrogens. However, at least in rodents, androgen action on cancellous bone can be directly mediated via AR activation, even in the absence of ERs. Androgens also increase cortical bone size via stimulation of both longitudinal and radial growth. First, androgens, like estrogens, have a biphasic effect on endochondral bone formation: at the start of puberty, sex steroids stimulate endochondral bone formation, whereas they induce epiphyseal closure at the end of puberty. Androgen action on the growth plate is, however, clearly mediated via aromatization in estrogens and interaction with ERalpha. Androgens increase radial growth, whereas estrogens decrease periosteal bone formation. This effect of androgens may be important because bone strength in males seems to be determined by relatively higher periosteal bone formation and, therefore, greater bone dimensions, relative to muscle mass at older age. Experiments in mice again suggest that both the AR and ERalpha pathways are involved in androgen action on radial bone growth. ERbeta may mediate growth-limiting effects of estrogens in the female but does not seem to be involved in the regulation of bone size in males. In conclusion, androgens may protect men against osteoporosis via maintenance of cancellous bone mass and expansion of cortical bone. Such androgen action on bone is mediated by the AR and ERalpha.

Androgens may regulate the male skeleton directly through a stimulation of androgen receptors or indirectly through aromatization of androgens into estrogen and, thereafter, through stimulation of estrogen receptors (ERs). The relative importance of ER subtypes in the regulation of the male skeleton was studied in ER␣-knockout (ERKO), ER␤-knockout (BERKO), and double ER␣͞␤-knockout (DERKO) mice. ERKO and DERKO, but not BERKO, demonstrated decreased longitudinal as well as radial skeletal growth associated with decreased serum levels of insulin-like growth factor I. Therefore, ER␣, but not ER␤, mediates important effects of estrogen in the skeleton of male mice during growth and maturation.

Estrogen is of importance for the regulation of adult bone metabolism. The aim of the present study was to determine the role of estrogen receptor-beta (ERbeta) in vivo on global estrogen-regulated transcriptional activity in bone. The effect of estrogen in bone of ovariectomized mice was determined using microarray analysis including 9400 genes. Most of the genes (95% = 240 genes) that were increased by estrogen in wild-type (WT) mice were also increased by estrogen in ERbeta-inactivated mice. Interestingly, the average stimulatory effect of estrogen on the mRNA levels of these genes was 85% higher in ERbeta-inactivated than in WT mice, demonstrating that ERbeta reduces estrogen receptor-alpha (ERalpha)-regulated gene transcription in bone. The average stimulatory effect of estrogen on estrogen-regulated bone genes in ERalpha-inactivated mice was intermediate between that seen in WT and ERalphabeta double-inactivated mice. Thus, ERbeta inhibits ERalpha-mediated gene transcription in the presence of ERalpha, whereas, in the absence of ERalpha, it can partially replace ERalpha. In conclusion, our in vivo data indicate that an important physiological role of ERbeta is to modulate ERalpha-mediated gene transcription supporting a "Ying Yang" relationship between ERalpha and ERbeta in mice.

No abstract

There are two known estrogen receptors, estrogen receptor-(ER ) and estrogen receptor-(ER ), which may mediate the actions of estrogen. The aim of the present study was to compare fat content, skeletal growth and adult bone metabolism in female mice lacking ER (ERKO), ER (BERKO) or both ERs (DERKO). We demonstrate that endogenous estrogens decrease the fat content in female mice via ER and not ER . Interestingly, the longitudinal bone growth was decreased in ERKO, increased in BERKO, but was intermediate in DERKO females, demonstrating that ER and ER exert opposing effects in the regulation of longitudinal bone growth. The effects on longitudinal bone growth were correlated with similar effects on serum levels of IGF-I. A complex regulation of the trabecular bone mineral density (BMD), probably caused by a disturbed feedback regulation of estrogen and testosterone, was observed in female ER-inactivated mice. Nevertheless, a partial functional redundancy for ER and ER in the maintenance of the trabecular BMD was observed in the female mice at 60 days of age. Thus, ER and ER may have separate effects (regulation of fat), opposing effects (longitudinal bone growth) or partial redundant effects (trabecular BMD at 60 days of age), depending on which parameter is studied.

Transportan is a 27-residue peptide (GWTLN SAGYL LGKIN LKALA ALAKK IL-amide) which has the ability to penetrate into living cells carrying a hydrophilic load. Transportan is a chimeric peptide constructed from the 12 N-terminal residues of galanin in the N-terminus with the 14-residue sequence of mastoparan in the C-terminus and a connecting lysine. Circular dichroism studies of transportan and mastoparan show that both peptides have close to random coil secondary structure in water. Sodium dodecyl sulfate (SDS) micelles induce 60% helix in transportan and 75% helix in mastoparan. The 600 MHz (1)H NMR studies of secondary structure in SDS micelles confirm the helix in mastoparan and show that in transportan the helix is localized to the mastoparan part. The less structured N-terminus of transportan has a secondary structure similar to that of the same sequence in galanin [Ohman, A., et al. (1998) Biochemistry 37, 9169-9178]. The position of mastoparan and transportan relative to the SDS micelle surface was studied by adding spin-labeled 5-doxyl- or 12-doxyl-stearic acid or Mn2+ to the peptide/micelle system. The combined results show that the peptides are for the most part buried in the SDS micelles. Only the C-terminal parts of both peptides and the central segment connecting the two parts of transportan are clearly surface exposed. For mastoparan, the secondary chemical shifts of the amide protons were found to vary periodically and display a pattern almost identical to those reported for mastoparan in phospholipid bicelles [Vold, R., et al. (1997) J. Biomol. NMR 9, 329-335], indicating similar structures and interactions in the two membrane-mimicking environments.

Immune checkpoint inhibitors and adoptive cell transfer (ACT) of autologous tumor-infiltrating T cells have shown durable responses in patients with melanoma. To study ACT and immunotherapies in a humanized model, we have developed PDXv2.0 — a melanoma PDX model where tumor cells and tumor-infiltrating T cells from the same patient are transplanted sequentially in non-obese diabetic/severe combined immune-deficient/common gamma chain (NOG/NSG) knockout mouse. Key to T-cell survival/effect in this model is the continuous presence of interleukin-2 (IL-2). Tumors that grow in PDXv2.0 are eradicated if the autologous tumor cells and T cells come from a patient that exhibited an objective response to ACT in the clinic. However, T cells from patients that are non-responders to ACT cannot kill tumor cells in PDXv2.0. Taken together, PDXv2.0 provides the potential framework to further model genetically diverse human cancers for assessing the efficacy of immunotherapies as well as combination therapies.

Estrogen exerts a variety of important physiological effects, which have been suggested to be mediated via the two known estrogen receptors (ERs), and . Three-monthold ovariectomized mice, lacking one or both of the two estrogen receptors, were given estrogen subcutaneously (2·3 µg/mouse per day) and the effects on different estrogen-responsive parameters, including skeletal effects, were studied. We found that estrogen increased the cortical bone dimensions in both wild-type (WT) and double ER knockout (DERKO) mice. DNA microarray analysis was performed to characterize this effect on cortical bone and it identified four genes that were regulated by estrogen in both WT and DERKO mice. The effect of estrogen on cortical bone in DERKO mice might either be due to remaining ER activity or represent an ER /ER -independent effect. Other effects of estrogen, such as increased trabecular bone mineral density, thymic atrophy, fat reduction and increased uterine weight, were mainly ER mediated.