p8 (NUPR1 (nuclear protein-1), Com1 (candidate of metastasis-1)) is a protein related to the high mobility group of transcriptional regulators. It is a key player in the cellular stress response and ...is involved in metastasis. p8 was first identified as a gene induced in pancreatitis but has been since found overexpressed in several cancers and pathological conditions. Despite its small size and apparently simple structure, p8 functions in several biochemical and genetic pathways, and its expression is crucial for in vivo metastasis in mice, for cytokine induction of metalloproteases, and for stress-induced cardiomyocyte hypertrophy. Understanding p8 functions will provide new opportunities for developing more effective therapeutic approaches to cancer and cardiovascular diseases.
Stromal fibroblast senescence has been linked to ageing-associated cancer risk. However, density and proliferation of cancer-associated fibroblasts (CAFs) are frequently increased. Loss or ...downmodulation of the Notch effector CSL (also known as RBP-Jκ) in dermal fibroblasts is sufficient for CAF activation and ensuing keratinocyte-derived tumours. We report that CSL silencing induces senescence of primary fibroblasts from dermis, oral mucosa, breast and lung. CSL functions in these cells as a direct repressor of multiple senescence- and CAF-effector genes. It also physically interacts with p53, repressing its activity. CSL is downmodulated in stromal fibroblasts of premalignant skin actinic keratosis lesions and squamous cell carcinomas, whereas p53 expression and function are downmodulated only in the latter, with paracrine FGF signalling as the probable culprit. Concomitant loss of CSL and p53 overcomes fibroblast senescence, enhances expression of CAF effectors and promotes stromal and cancer cell expansion. The findings support a CAF activation-stromal co-evolution model under convergent CSL-p53 control.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, UILJ, UKNU, UL, UM, UPUK
Cancer-associated fibroblasts (CAFs) are important for tumor initiation and promotion. CSL, a transcriptional repressor and Notch mediator, suppresses CAF activation. Like CSL, ATF3, a ...stress-responsive transcriptional repressor, is down-modulated in skin cancer stromal cells, and
knockout mice develop aggressive chemically induced skin tumors with enhanced CAF activation. Even at low basal levels, ATF3 converges with CSL in global chromatin control, binding to few genomic sites at a large distance from target genes. Consistent with this mode of regulation, deletion of one such site 2 Mb upstream of
induces expression of the gene. Observed changes are of translational significance, as bromodomain and extra-terminal (BET) inhibitors, unlinking activated chromatin from basic transcription, counteract the effects of ATF3 or CSL loss on global gene expression and suppress CAF tumor-promoting properties in an in vivo model of squamous cancer-stromal cell expansion. Thus, ATF3 converges with CSL in negative control of CAF activation with epigenetic changes amenable to cancer- and stroma-focused intervention.
Melanoma provides a primary benchmark for targeted drug therapy. Most melanomas with BRAF
mutations regress in response to BRAF/MEK inhibitors (BRAFi/MEKi). However, nearly all relapse within the ...first two years, and there is a connection between BRAFi/MEKi-resistance and poor response to immune checkpoint therapy. We reported that androgen receptor (AR) activity is required for melanoma cell proliferation and tumorigenesis. We show here that AR expression is markedly increased in BRAFi-resistant melanoma cells, and in sensitive cells soon after BRAFi exposure. Increased AR expression is sufficient to render melanoma cells BRAFi-resistant, eliciting transcriptional changes of BRAFi-resistant subpopulations, including elevated EGFR and SERPINE1 expression, of likely clinical significance. Inhibition of AR expression or activity blunts changes in gene expression and suppresses proliferation and tumorigenesis of BRAFi-resistant melanoma cells, promoting clusters of CD8
T cells infiltration and cancer cells killing. Our findings point to targeting AR as possible co-therapeutical approach in melanoma treatment.
Abstract
Cancer associated fibroblasts (CAFs) are a key component of the tumor microenvironment. Genomic alterations in these cells remain a point of contention. We report that CAFs from skin ...squamous cell carcinomas (SCCs) display chromosomal alterations, with heterogeneous
NOTCH1
gene amplification and overexpression that also occur, to a lesser extent, in dermal fibroblasts of apparently unaffected skin. The fraction of the latter cells harboring
NOTCH1
amplification is expanded by chronic UVA exposure, to which CAFs are resistant. The advantage conferred by
NOTCH1
amplification and overexpression can be explained by NOTCH1 ability to block the DNA damage response (DDR) and ensuing growth arrest through suppression of ATM-FOXO3a association and downstream signaling cascade. In an orthotopic model of skin SCC, genetic or pharmacological inhibition of
NOTCH1
activity suppresses cancer/stromal cells expansion. Here we show that
NOTCH1
gene amplification and increased expression in CAFs are an attractive target for stroma-focused anti-cancer intervention.
Epigenetic mechanisms oversee epidermal homeostasis and oncogenesis. The identification of kinases controlling these processes has direct therapeutic implications. We show that ULK3 is a nuclear ...kinase with elevated expression levels in squamous cell carcinomas (SCCs) arising in multiple body sites, including skin and Head/Neck. ULK3 loss by gene silencing or deletion reduces proliferation and clonogenicity of human keratinocytes and SCC-derived cells and affects transcription impinging on stem cell-related and metabolism programs. Mechanistically, ULK3 directly binds and regulates the activity of two histone arginine methyltransferases, PRMT1 and PRMT5 (PRMT1/5), with ULK3 loss compromising PRMT1/5 chromatin association to specific genes and overall methylation of histone H4, a shared target of these enzymes. These findings are of translational significance, as downmodulating ULK3 by RNA interference or locked antisense nucleic acids (LNAs) blunts the proliferation and tumorigenic potential of SCC cells and promotes differentiation in two orthotopic models of skin cancer.
The connection between signaling pathways activating cancer-associated fibroblasts (CAFs) remains to be determined. Metabolic alterations linked to autophagy have also been implicated in CAF ...activation. CSL/RBPJ, a transcriptional repressor that mediates Notch signaling, suppresses the gene expression program(s), leading to stromal senescence and CAF activation. Deregulated GLI signaling can also contribute to CAF conversion. Here, we report that compromised CSL function depends on GLI activation for conversion of human dermal fibroblasts into CAFs, separately from cellular senescence. Decreased CSL upregulates the expression of the ULK3 kinase, which binds and activates GLI2. Increased ULK3 also induces autophagy, which is unlinked from GLI and CAF activation. ULK3 upregulation occurs in the CAFs of several tumor types, and ULK3 silencing suppresses the tumor-enhancing properties of these cells. Thus, ULK3 links two key signaling pathways involved in CAF conversion and is an attractive target for stroma-focused anti-cancer intervention.
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•CAF conversion by loss of CSL depends on GLI activation•CSL functions as a negative regulator of the pro-autophagy kinase ULK3•Increased ULK3 induces GLI2-dependent CAF activation separately from autophagy•Silencing of ULK3 in SCC-derived CAFs suppresses their tumor-enhancing properties
Goruppi et al. demonstrate that CSL, a transcriptional repressor mediating Notch signaling, suppresses the conversion of fibroblasts into cancer-associated fibroblasts (CAFs) by controlling the expression of autophagy kinase ULK3, which, in turn, activates GLI signaling. Their studies connect two key pathways involved in CAF activation and identify a target for stroma-focused anti-cancer intervention.
Cancer-associated fibroblasts (CAFs) are important at all tumor stages. CSL/RBPJκ suppresses the gene expression program leading to CAF activation and associated metabolic reprogramming, as well as ...autophagy. Little is known about CSL protein turnover, especially in the tumor microenvironment. We report that, in human dermal fibroblasts (HDFs), conditions inducing autophagy—often found in tumor stroma—down-regulate CSL protein levels but do not affect its mRNA levels. Genetic or pharmacologic targeting of the autophagic machinery blocks CSL down-modulation. Mechanistically, endogenous CSL associates with the autophagy and signaling adaptor p62/SQSTM1, which is required for CSL down-modulation by autophagy. This is functionally significant, because both CSL and p62 levels are lower in skin cancer-derived CAFs, in which autophagy is increased. Increasing cellular CSL levels stabilizes p62 and down-modulates the autophagic process. We reveal here an autophagy-initiated mechanism for CSL down-modulation, which could be targeted for stroma-focused cancer prevention and treatment.
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•Autophagy down-modulates CSL/RBPJk in stromal fibroblasts•CSL degradation by autophagy requires interaction with p62 adaptor•CSL down-modulation by autophagy induces cancer-associated fibroblast (CAF) genes•CSL overexpression in CAFs stabilizes p62 and represses expression of autophagy genes
Autophagic conditions are often found in the tumor stroma, where CSL/RBPJκ levels are down-modulated. Goruppi et al. identify a key role for autophagy in the degradation of CSL through a direct interaction with the p62 adaptor. This induces CSL-repressed genes involved in CAF activation and autophagy, linking the two processes.
Genomic instability is a hallmark of cancer. Whether it also occurs in Cancer Associated Fibroblasts (CAFs) remains to be carefully investigated. Loss of CSL/RBP-Jκ, the effector of canonical NOTCH ...signaling with intrinsic transcription repressive function, causes conversion of dermal fibroblasts into CAFs. Here, we find that CSL down-modulation triggers DNA damage, telomere loss and chromosome end fusions that also occur in skin Squamous Cell Carcinoma (SCC)-associated CAFs, in which CSL is decreased. Separately from its role in transcription, we show that CSL is part of a multiprotein telomere protective complex, binding directly and with high affinity to telomeric DNA as well as to UPF1 and Ku70/Ku80 proteins and being required for their telomere association. Taken together, the findings point to a central role of CSL in telomere homeostasis with important implications for genomic instability of cancer stromal cells and beyond.
The limited supply of oxygen and nutrients is thought to result in rigorous selection of cells that will eventually form the tumor.
Nupr1 expression pattern was analyzed in human tissue microarray ...(TMA) and correlated with survival time of the patient. Microarray analysis was conducted on MiaPaCa2 cells subjected to metabolic stress in Nupr1-silenced conditions. DNA repair and cell cycle-associated gene expression was confirmed by real-time quantitative PCR (qRT-PCR). Nupr1 and AURKA protective role were analyzed using RNA interference (RNAi) silencing or overexpression. DNA damage and autophagy were analyzed by Western blot analysis and immunofluorescence.
We showed that both Nupr1 and HIF1α are coexpressed in human pancreatic ductal adenocarcinoma (PDAC) samples and negatively correlate with survival time. PDAC-derived cells submitted to hypoxia and/or glucose starvation induce DNA damage-dependent cell death concomitantly to the overexpression of stress protein Nupr1. Affymetrix-based transcriptoma analysis reveals that Nupr1 knockdown enhances DNA damage and alters the expression of several genes involved in DNA repair and cell-cycle progression. Expression of some of these genes is common to hypoxia and glucose starvation, such as Aurka gene, suggesting that Nupr1 overexpression counteracts the transcriptional changes occurring under metabolic stress. The molecular mechanism by which hypoxia and glucose starvation induce cell death involves autophagy-associated, but not caspase-dependent, cell death. Finally, we have found that AURKA expression is partially regulated by Nupr1 and plays a major role in this response.
Our data reveal that Nupr1 is involved in a defense mechanism that promotes pancreatic cancer cell survival when exposed to metabolic stress.
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