GLI transcription factors have important roles in intracellular signaling cascade, acting as the main mediators of the HH-GLI signaling pathway. This is one of the major developmental pathways, ...regulated both canonically and non-canonically. Deregulation of the pathway during development leads to a number of developmental malformations, depending on the deregulated pathway component. The HH-GLI pathway is mostly inactive in the adult organism but retains its function in stem cells. Aberrant activation in adult cells leads to carcinogenesis through overactivation of several tightly regulated cellular processes such as proliferation, angiogenesis, EMT. Targeting GLI transcription factors has recently become a major focus of potential therapeutic protocols.
Abstract
Prostate cancer is the second most frequent cancer diagnosed in men worldwide. Localized disease can be successfully treated, but advanced cases are more problematic. After initial ...effectiveness of androgen deprivation therapy, resistance quickly occurs. Therefore, we aimed to investigate the role of Hedgehog-GLI (HH-GLI) signaling in sustaining androgen-independent growth of prostate cancer cells. We found various modes of HH-GLI signaling activation in prostate cancer cells depending on androgen availability. When androgen was not deprived, we found evidence of non-canonical SMO signaling through the SRC kinase. After short-term androgen deprivation canonical HH-GLI signaling was activated, but we found little evidence of canonical HH-GLI signaling activity in androgen-independent prostate cancer cells. We show that in androgen-independent cells the pathway ligand, SHH-N, non-canonically binds to the androgen receptor through its cholesterol modification. Inhibition of this interaction leads to androgen receptor signaling downregulation. This implies that SHH-N activates the androgen receptor and sustains androgen-independence. Targeting this interaction might prove to be a valuable strategy for advanced prostate cancer treatment. Also, other non-canonical aspects of this signaling pathway should be investigated in more detail and considered when developing potential therapies.
Several signaling pathways are aberrantly activated in head and neck squamous cell carcinoma (HNSCC), including the Hedgehog-Gli (HH-GLI), WNT, EGFR, and NOTCH pathways. The HH-GLI pathway has mostly ...been investigated in the context of canonical signal transduction and the inhibition of the membrane components of the pathway. In this work we investigated the role of downstream inhibitors GANT61 and lithium chloride (LiCl) on cell viability, wound closure, and colony forming ability of HNSCC cell lines. Five HNSCC cell lines were treated with HH-GLI pathway inhibitors affecting different levels of signal transduction. GANT61 and LiCl reduce the proliferation and colony formation capabilities of HNSCC cell lines, and LiCl has an additional effect on wound closure. The major effector of the HH-GLI signaling pathway in HNSCC is the GLI3 protein, which is expressed in its full-length form and is functionally regulated by GSK3β. LiCl treatment increases the inhibitory Ser9 phosphorylation of the GSK3β protein, leading to increased processing of GLI3 from full-length to repressor form, thus inhibiting HH-GLI pathway activity. Therefore, downstream inhibition of HH-GLI signaling may be a promising therapeutic strategy for HNSCC.
Hedgehog signaling pathway is a developmental pathway mostly inactive in adult tissues, with the exception of stem cells. It is often found upregulated in various tumors, and associated with cancer ...stem cell maintenance.
This review focuses on different aspects of Hedgehog activation in tumors, with special emphasis on ovarian tumors and their treatment.
Mutations in pathway components lead to a series of developmental malformations and syndromes. Aberrant activation of the pathway can be caused by mutations, noncanonical transcriptional regulation, or epigenetic changes.
This pathway is an interesting target in cancer therapy, especially when combined with therapies targeting other signaling pathways. Combination therapy can be used to bypass resistance or to target cancer stem cells in a more efficient way.
Hedgehog-Gli (Hh-Gli) signaling pathway is one of the new molecular targets found upregulated in breast tumors. Estrogen receptor alpha (ERα) signaling has a key role in the development of ...hormone-dependent breast cancer. We aimed to investigate the effects of inhibiting both pathways simultaneously on breast cancer cell survival and the potential interactions between these two signaling pathways. ER-positive MCF-7 cells show decreased viability after treatment with cyclopamine, a Hh-Gli pathway inhibitor, as well as after tamoxifen (an ERα inhibitor) treatment. Simultaneous treatment with cyclopamine and tamoxifen on the other hand, causes short-term survival of cells, and increased migration. We found upregulated Hh-Gli signaling under these conditions and protein profiling revealed increased expression of proteins involved in cell proliferation and migration. Therefore, even though Hh-Gli signaling seems to be a good potential target for breast cancer therapy, caution must be advised, especially when combining therapies. In addition, we also show a potential direct interaction between the Shh protein and ERα in MCF-7 cells. Our data suggest that the Shh protein is able to activate ERα independently of the canonical Hh-Gli signaling pathway. Therefore, this may present an additional boost for ER-positive cells that express Shh, even in the absence of estrogen.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Ovarian cancer (OC) is the most lethal female gynecological malignancy, mostly due to diagnosis in late stages when treatment options are limited. Hedgehog-GLI (HH-GLI) signaling is a major ...developmental pathway involved in organogenesis and stem cell maintenance, and is activated in OC. One of its targets is survivin (
), an inhibitor of apoptosis protein (IAP) that plays a role in multiple processes, including proliferation and cell survival. We wanted to investigate the role of different GLI proteins in the regulation of survivin isoform expression (WT, 2α, 2B, 3B, and Δex3) in the SKOV-3 OC cell line. We demonstrated that survivin isoforms are downregulated in GLI1 and GLI2 knock-out cell lines, but not in the GLI3 knock-out. Treatment of GLI1 knock-out cells with GANT-61 shows an additional inhibitory effect on several isoforms. Additionally, we examined the expression of survivin isoforms in OC samples and the potential role of
polymorphisms in isoform expression. Clinical samples showed the same pattern of survivin isoform expression as in the cell line, and several
polymorphisms showed the correlation with isoform expression. Our results showed that survivin isoforms are regulated both by different GLI proteins and
polymorphisms in OC.
The role of Hedgehog-Gli (Hh-Gli) signaling in colon cancer tumorigenesis has not yet been completely elucidated. Here we provide strong evidence of Hh-Gli signaling involvement in survival of colon ...cancer cells, with the main trigger of activation being deregulated GSK3β.
Our clinical data reveals high expression levels of GSK3β and Gli3 in human colon cancer tissue samples, with positive correlation between GSK3β expression and DUKES' stage. Further experiments on colon cancer cell lines have shown that a deregulated GSK3β upregulates Hh-Gli signaling and positively affects colon cancer cell survival. We show that inhibition of GSK3β with lithium chloride enhances Gli3 processing into its repressor form, consequently downregulating Hh-Gli signaling, reducing cell proliferation and inducing cell death. Analysis of the molecular mechanisms revealed that lithium chloride enhances Gli3–SuFu–GSK3β complex formation leading to more efficient Gli3 cleavage and Hh-Gli signaling downregulation. This work proposes that activation of the Hh-Gli signaling pathway in colon cancer cells occurs non-canonically via deregulated GSK3β. Gli3 seems to be the main pathway effector, highlighting the activator potential of this transcription factor, which is highly dependent on GSK3β function and fine tuning of the Gli3–SuFu–GSK3β platform.
•GSK3β staining in colon cancer tissues is positively correlated with DUKES' stage.•GSK3β is the main molecular switch for Hh-Gli activation in colon cancer cells.•GSK3β inhibition with LiCl enhances Gli3 processing.•GSK3β inhibition with LiCl downregulates Hh-Gli signaling and induces cell death.•Hh-Gli signaling stimulation rescues LiCl effects on cell proliferation.
Unlike other tumours, TP53 is rarely mutated in melanoma; however, it fails to function as a tumour suppressor. We assume that its functions might be altered through interactions with several ...families of proteins, including p53/p73, NME and GLI. To elucidate the potential interplay among these families we analysed the expression profiles of aforementioned genes and proteins in a panel of melanoma cell lines, metastatic melanoma specimens and healthy corresponding tissue. Using qPCR a higher level of NME1 gene expression and lower levels of Δ40p53β, ΔNp73, GLI1, GLI2 and PTCH1 were observed in tumour samples compared to healthy tissue. Protein expression of Δ133p53α, Δ160p53α and ΔNp73α isoforms, NME1 and NME2, and N'ΔGLI1, GLI1FL, GLI2ΔN isoforms was elevated in tumour tissue, whereas ∆Np73β was downregulated. The results in melanoma cell lines, in general, support these findings. In addition, we correlated expression profiles with clinical features and outcome. Higher Δ133p53β and p53α mRNA and both GLI1 mRNA and GLI3R protein expression had a negative impact on the overall survival. Shorter overall survival was also connected with lower p53β and NME1 gene expression levels. In conclusion, all examined genes may have implications in melanoma development and functional inactivity of TP53.
Hedgehog signaling pathway has been implicated in the pathology of ovarian cancer, and Survivin (BIRC5) has been suggested as a novel target of this pathway. Herein we investigated the role of ...Hedgehog signaling pathway and Survivin in ovarian carcinoma and borderline tumor samples. We aimed to determine possible ways of pathway modulation on primary ovarian cancer cells and an established cell line. RNA was extracted from fresh tumors and control tissues and gene expression was examined using qRT-PCR. Pathway activity in cell lines was examined after treatment with cyclopamine, SHH protein, GANT-61 or lithium chloride using qRT-PCR, western blot and confocal microscopy. The difference between control tissue, borderline tumors and carcinomas can be seen in GLI1 and SUFU gene expression, which is significantly higher in borderline tumors compared to carcinomas. SUFU also shows lower expression levels in higher FIGO stages relative to lower stages. BIRC5 is expressed in all tumors and in healthy ovarian tissues compared to our control tissue, healthy fallopian tube samples. Primary cells developed from ovarian carcinoma tissue respond to cyclopamine treatment with a short-term decrease in cell proliferation, downregulation of Hedgehog pathway genes, including BIRC5, and changes in protein dynamics. Stimulation with SHH protein results in increased cell migration, while GLI1 transfection or PTCH1 silencing demonstrate pathway upregulation. The pathway activity can be modulated by LiCl at the GSK3β-SUFU-GLI level, suggesting at least partial non-canonical activation. Downregulation of the pathway with GANT-61 has proved to be more effective than cyclopamine. GLI inhibitors may be a superior treatment option in ovarian cancer compared to SMO inhibitors.
PTCH1 gene codes for a 12-pass transmembrane receptor with a negative regulatory role in the Hedgehog-Gli signaling pathway. PTCH1 germline mutations cause Gorlin syndrome, a disorder characterized ...by developmental abnormalities and tumor susceptibility. The autosomal dominant inheritance, and the evidence for PTCH1 haploinsufficiency, suggests that fine-tuning systems of protein patched homolog 1 (PTC1) levels exist to properly regulate the pathway. Given the role of 5' untranslated region (5'UTR) in protein expression, our aim was to thoroughly explore cis-regulatory elements in the 5'UTR of PTCH1 transcript 1b. The (CGG)
n
polymorphism was the main potential regulatory element studied so far but with inconsistent results and no clear association between repeat number and disease risk. Using luciferase reporter constructs in human cell lines here we show that the number of CGG repeats has no strong impact on gene expression, both at mRNA and protein levels. We observed variability in the length of 5'UTR and changes in abundance of the associated transcripts after pathway activation. We show that upstream AUG codons (uAUGs) present only in longer 5'UTRs could negatively regulate the amount of PTC1 isoform L (PTC1-L). The existence of an internal ribosome entry site (IRES) observed using different approaches and mapped in the region comprising the CGG repeats, would counteract the effect of the uAUGs and enable synthesis of PTC1-L under stressful conditions, such as during hypoxia. Higher relative translation efficiency of PTCH1b mRNA in HEK 293T cultured hypoxia was observed by polysomal profiling and Western blot analyses. All our results point to an exceptionally complex and so far unexplored role of 5'UTR PTCH1b cis-element features in the regulation of the Hedgehog-Gli signaling pathway.
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