Abstract
The
B
cl‐2 family member
M
cl‐1 is essential for melanoma survival; however, the influence of oncogenic
BRAF
signalling remains elusive. In this study,
M
cl‐1 splice variant expression was ...determined in a panel of melanoma cell lines in relation to
BRAF
mutational status.
M
cl‐1
L
m
RNA
expression was increased in melanoma cells compared with primary melanocytes with significantly increased m
RNA
and protein expression observed in
BRAF
V600E
mutant melanoma cells. Although no change in
M
cl‐1S m
RNA
was observed,
M
cl‐1
S
protein expression also increased in
BRAF
mutant melanoma cells. Additionally, while over‐expression of mutant
BRAF
V600E
increased both
M
cl‐1
L
and
M
cl‐1
S
expression, inhibition of hyperactive
BRAF
signalling resulted in decreased
M
cl‐1
L
expression. These studies suggest that the regulation of
M
cl‐1 expression by
BRAF
signalling is increased by oncogenic activation of
BRAF
, revealing a mechanism of apoptotic resistance which may be overcome by the use of more specifically targeted
M
cl‐1 inhibitors.
The synthetic retinoid fenretinide
N-(4 hydroxyphenyl)retinamide induces apoptosis of cancer cells and acts synergistically with chemotherapeutic drugs, thus providing opportunities for novel ...approaches to cancer therapy. The upstream signaling events induced by fenretinide include an increase in intracellular levels of ceramide, which is subsequently metabolized to GD3. This ganglioside triggers the activation of 12-Lox (12-lipoxygenase) leading to oxidative stress and apoptosis via the induction of the transcription factor Gadd153 and the Bcl-2-family member protein Bak. Increased evidence suggests that the apoptotic pathway activated by fenretinide is p53-independent and this may represent a novel way to treat tumors resistant to DNA-damaging chemotherapeutic agents. Therefore, fenretinide offers increased clinical benefit as a novel agent for cancer therapy, able to complement the action of existing chemotherapeutic treatment regimes. Furthermore, synergy between fenretinide and chemotherapeutic drugs may facilitate the use of chemotherapeutic drugs at lower concentrations, with possible reduction in treatment-associated morbidity.
During the night of 29-30 October 1995, over 600 Redwings Turdus iliacus died as a result of flying into the lighthouse at Bardsey, Gwynedd, North Wales. These migrating birds were used to ...investigate fat levels in relation to age, sex, biometrics and pectoral muscle mass. Wing length was the best single linear measure of size and mean wing length of males was 2.5 mm greater than that of females. Body mass of the casualties declined during the night and the mean body mass of birds arriving towards the end of the night was 1.5 g lower than that of the first arrivals. Fat deposits at different body sites were significantly correlated with each other and with body mass, and, by extrapolation, the mass of intra-abdominal fat remaining would be significant when other fat deposits have been depleted. Fat in the tracheal pit (the claviculo-coracoid fat body) demonstrated the best correlation with body mass and was linearly correlated with visual fat scores. Fat was also present in the pectoral muscle but did not make a significant contribution to overall body mass. Two-thirds of the variation in body mass was accounted for by wing length, the mass of claviculo-coracoid fat and the lean-dry mass of pectoral muscle. Claviculo-coracoid fat and lean pectoral-muscle mass contributed independently to overall body mass. These data support the view that increase in fat in relation to migration is accompanied by an increase in protein or lean muscle mass, but suggest that these are controlled independently.
The overall survival rate for patients with neuroblastoma has improved over the past two decades, but long-term survival for the subgroup of patients with high-risk disease remains low. In recent ...years, there has been interest in the potential clinical use of drugs able to induce differentiation of neuroblastoma cells. Since 9-cis-retinoic acid induces better and more sustained differentiation of neuroblastoma in vitro than other retinoic acid isomers, this may be a more appropriate retinoid for use in neuroblastoma therapy.
The purpose of this work was to compare the long-term effects of all-trans- and 9-cis-retinoic acid on neuroblastoma differentiation using an N-type (neuroblastic) cell line, SH SY 5Y, as an in vitro model. In addition, we wanted to find out whether 9-cis-retinoic acid would induce programmed cell death (apoptosis) in these N-type neuroblastoma cells and to determine whether the effects of either 9-cis- or all-trans-retinoic acid are dependent on their continued presence in the culture medium.
SH SY 5Y cells were incubated in either the continued presence of all-trans- or 9-cis-retinoic acid or for 5 days with retinoic acid followed by culture in the absence of retinoid for up to 13 days. Morphologic changes were observed using phase-contrast and scanning electron microscopy. Apoptosis was determined by flow cytometry of propidium iodide-stained cells and by using terminal deoxynucleotidyl transferase to end-label DNA fragments in situ in apoptotic cells.
Culture of SH SY 5Y cells with all-trans- or 9-cis retinoic acid for 5 days induced morphologic differentiation and inhibited cell growth. These effects were maintained in the continuous presence of each retinoic acid isomer but were more profound in cells treated with 9-cis-retinoic acid. The differentiation of cells treated with all-trans-retinoic acid was reversible once retinoic acid was removed from the medium. Conversely, apoptosis was induced in cells treated with 9-cis-retinoic acid for 5 days and cultured for 9 days (4 days after washout) but not in cells cultured in the continuous presence of 9-cis-retinoic acid. This effect was specific to 9-cis-retinoic acid.
Previous studies have demonstrated differential responses to all-trans-retinoic acid in N- and S-type (substrate-adherent or Schwann-like) neuroblastoma cells: Apoptosis is induced in S-type cells, whereas differentiation occurs in N-type cells. The present results show that, unlike all-trans-retinoic acid, 9-cis-retinoic acid induces both differentiation and apoptosis in N-type SH SY 5Y neuroblastoma cells. However, apoptosis was dependent on removal of 9-cis-retinoic acid from the culture medium.
Since both differentiation and apoptosis are involved in tumor regression, 9-cis-retinoic acid may be a more appropriate retinoid for clinical trials in neuroblastoma. The dependence of apoptosis on treatment and subsequent removal of 9-cis-retinoic acid implies that drug scheduling may be an important parameter affecting therapeutic efficacy.
Retinoic acid is essential for the normal differentiation of epithelia but its cellular function is obscure. The expression patterns of retinoic acid receptors (RARs) in skin cell types may give an ...insight into the role of retinoic acid in skin. We have compared the patterns of RAR expression in human keratinocytes and dermal fibroblasts in vitro, and studied the effects of retinoic acid on RAR expression. RAR-alpha and RAR-gamma were expressed in keratinocytes and fibroblasts: RAR-gamma was expressed at similar levels in both cell types but RAR-alpha was more abundant in fibroblasts. There were no differences in expression of either RAR-alpha or RAR-gamma between stratifying (high-calcium medium) and proliferating (low-calcium medium) keratinocytes and expression of these RARs was unaffected by retinoic acid. RAR-beta was undetectable in keratinocytes. In the majority of fibroblast cell lines, RAR-beta transcripts were either undetectable or expressed at a low level. Retinoic acid at low concentrations (10(-10) to 10(-9) M) rapidly induced the expression of RAR-beta. Cyclic adenosine monophosphate (cAMP) analogues inhibit RAR-beta induction in teratocarcinoma cells. However, dibutyryl-cAMP did not affect RAR-beta induction in fibroblasts. Forskolin, an adenylate cyclase activator, and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) decreased constitutive RAR-beta mRNA levels but did not block induction of RAR-beta by retinoic acid. Since intracellular cAMP levels were only increased detectably in response to forskolin, the reduction in constitutive levels of RAR-beta mRNA may be mediated by mechanisms other than via cAMP.
Sedge Warblers Acrocephalus schoenobaenus are reported to have no partial postjuvenile moult before migration, but this is uncertain and controversial. To resolve this issue, feather growth and ...development was studied in nestling, juvenile and 1st-calendar-year Sedge Warblers. Two phases of feather growth, representing growth of juvenile feathers in the main feather tracts of nestlings, and, within a few days of fledging, the later growth of feathers along the margins of the mid-dorsal tract, the ventral apterium and under-wing remigial coverts, are described. In addition, replacement of some dorsal-tract juvenile feathers was observed in 19% of birds and may represent the initiation of post-juvenile moult. These data indicate that a proportion of juvenile Sedge Warblers in northern England may initiate post-juvenile moult before migration. This observation is discussed in the context of strategies for moult, dispersal and migration in Acrocephalus species and highlights the need for a greater understanding of the physiological control of moult in relation to dispersal and migration.
PDF
