Targeting the hedgehog transcription factors GLI1 and GLI2 restores sensitivity to vemurafenib-resistant human melanoma cells

Pharmacological agents targeting drug-tolerant persister cells in cancer

Current cancer therapy can be effective, but the development of drug resistant disease is the usual outcome. These drugs can eliminate most of the tumor burden but often fail to eliminate the rare, "Drug Tolerant Persister" (DTP) cell subpopulations in residual tumors, which can be referred to as "Persister" cells. Therefore, novel therapeutic agents specifically targeting or preventing the development of drug-resistant tumors mediated by the remaining persister cells subpopulations are needed. Since approximately ninety percent of cancer-related deaths occur because of the eventual development of drug resistance, identifying, and dissecting the biology of the persister cells is essential for the creation of drugs to target them. While there remains uncertainty surrounding all the markers identifying DTP cells in the literature, this review summarizes the drugs and therapeutic approaches that are available to target the persister cell subpopulations expressing the cellular markers ATP-binding cassette sub-family B member 5 (ABCB5), CD133, CD271, Lysine-specific histone demethylase 5 (KDM5), and aldehyde dehydrogenase (ALDH). Persister cells expressing these markers were selected as the focus of this review because they have been found on cells surviving following drug treatments that promote recurrent drug resistant cancer and are associated with stem cell-like properties, including self-renewal, differentiation, and resistance to therapy. The limitations and obstacles facing the development of agents targeting these DTP cell subpopulations are detailed, with discussion of potential solutions and current research areas needing further exploration.

The comprehensive landscape of prognosis, immunity, and function of the GLI family by pan-cancer and single-cell analysis

The Hedgehog (Hh) signaling pathway has been implicated in the pathogenesis of various cancers. However, the roles of the downstream GLI family (GLI1, GLI2, and GLI3) in tumorigenesis remain elusive. This study aimed to unravel the genetic alterations of GLI1/2/3 in cancer and their association with the immune microenvironment and related signaling pathways. Firstly, we evaluated the expression profiles of GLI1/2/3 in different cancer types, analyzed their prognostic and predictive values, and assessed their correlation with tumor-infiltrating immune cells. Secondly, we explored the relationships between GLI1/2/3 and genetic mutations, epigenetic modifications, and clinically relevant drugs. Finally, we performed enrichment analysis to decipher the underlying mechanisms of GLI1/2/3 in cancer initiation and progression. Our results revealed that the expression levels of GLI1/2/3 were positively correlated in most cancer tissues, suggesting a cooperative role of these factors in tumorigenesis. We also identified tissue-specific expression patterns of GLI1/2/3, which may reflect the distinct functions of these factors in different cell types. Furthermore, GLI1/2/3 expression displayed significant associations with poor prognosis in several cancers, indicating their potential as prognostic biomarkers and therapeutic targets. Importantly, we found that GLI1/2/3 modulated the immune microenvironment by regulating the recruitment, activation, and polarization of cancer-associated fibroblasts, endothelial cells, and macrophages. Additionally, functional enrichment analyses indicated that GLI1/2/3 are involved in the regulation of epithelial-mesenchymal transition (EMT). Together, our findings shed new light on the roles of GLI1/2/3 in tumorigenesis and provide a potential basis for the development of novel therapeutic strategies targeting GLI-mediated signaling pathways in cancer.

The sonic hedgehog pathway suppresses oxidative stress and senescence in nucleus pulposus cells to alleviate intervertebral disc degeneration via GPX4

Disruption of intervertebral disc (IVD) homeostasis caused by oxidative stress and nucleus pulposus cell (NPC) senescence is a main cause of intervertebral disc degeneration (IDD). The sonic hedgehog (Shh) pathway plays an important role in IVD development, but its roles in IDD are unknown. This study aimed to investigate the effects of the Shh pathway on the alleviation of IDD and the related mechanisms. In vivo, the effect of the Shh pathway on IVD homeostasis was studied by intraperitoneal injection of recombinant Shh (rShh) and GANT61 based on puncture-induced IDD. GANT61, lentivirus-coated sh-Gli1 and rShh were used to investigate the role and mechanism of the Shh pathway in NPCs based on senescence induced by Braco19 and oxidative stress induced by TBHP. Shh pathway expression decreased, and senescence and oxidative stress increased with age. Intraperitoneal injection of rShh activated the Shh pathway to suppress oxidative stress and NPC senescence and consequently alleviated needle puncture-induced IDD. In vitro, the Shh pathway upregulated glutathione peroxidase 4 (GPX4) expression to suppress oxidative stress and senescence in NPCs. Moreover, GPX4 suppression in NPCs by si-GPX4 significantly reduced the protective effect of the Shh pathway on oxidative stress and senescence in NPCs. Our results demonstrate for the first time that the Shh pathway plays a key role in the alleviation of IDD by suppressing oxidative stress and cell senescence in NP tissues. This study provides a new potential target for the prevention and reversal of IDD.

Targeting GLI1 and GLI2 with small molecule inhibitors to suppress GLI-dependent transcription and tumor growth

Aberrant activation of Hedgehog (HH) signaling in cancer is the result of genetic alterations of upstream pathway components (canonical) or other oncogenic mechanisms (noncanonical), that ultimately concur to activate the zinc-finger transcription factors GLI1 and GLI2. Therefore, inhibition of GLI activity is a good therapeutic option to suppress both canonical and noncanonical activation of the HH pathway. However, only a few GLI inhibitors are available, and none of them have the profile required for clinical development due to poor metabolic stability and aqueous solubility, and high hydrophobicity. Two promising quinoline inhibitors of GLI were selected by virtual screening and subjected to hit-to-lead optimization, thus leading to the identification of the 4-methoxy-8-hydroxyquinoline derivative JC19. This molecule impaired GLI1 and GLI2 activities in several cellular models interfering with the binding of GLI1 and GLI2 to DNA. JC19 suppressed cancer cell proliferation by enhancing apoptosis, inducing a strong anti-tumor response in several cancer cell lines in vitro. Specificity towards GLI1 and GLI2 was demonstrated by lower activity of JC19 in GLI1- or GLI2-depleted cancer cells. JC19 showed excellent metabolic stability and high passive permeability. Notably, JC19 inhibited GLI1-dependent melanoma xenograft growth in vivo, with no evidence of toxic effects in mice. These results highlight the potential of JC19 as a novel anti-cancer agent targeting GLI1 and GLI2.

The Role of Hedgehog Signaling in the Melanoma Tumor Bone Microenvironment

A crucial regulator in melanoma progression and treatment resistance is tumor microenvironments, and Hedgehog (Hh) signals activated in a tumor bone microenvironment are a potential new therapeutic target. The mechanism of bone destruction by melanomas involving Hh/Gli signaling in such a tumor microenvironment is unknown. Here, we analyzed surgically resected oral malignant melanoma specimens and observed that Sonic Hedgehog, Gli1, and Gli2 were highly expressed in tumor cells, vasculatures, and osteoclasts. We established a tumor bone destruction mouse model by inoculating B16 cells into the bone marrow space of the right tibial metaphysis of 5-week-old female C57BL mice. An intraperitoneal administration of GANT61 (40 mg/kg), a small-molecule inhibitor of Gli1 and Gli2, resulted in significant inhibition of cortical bone destruction, TRAP-positive osteoclasts within the cortical bone, and endomucin-positive tumor vessels. The gene set enrichment analysis suggested that genes involved in apoptosis, angiogenesis, and the PD-L1 expression pathway in cancer were significantly altered by the GANT61 treatment. A flow cytometry analysis revealed that PD-L1 expression was significantly decreased in cells in which late apoptosis was induced by the GANT61 treatment. These results suggest that molecular targeting of Gli1 and Gli2 may release immunosuppression of the tumor bone microenvironment through normalization of abnormal angiogenesis and bone remodeling in advanced melanoma with jaw bone invasion.

N6-methyladenine-mediated aberrant activation of the lncRNA SOX2OT-GLI1 loop promotes non-small-cell lung cancer stemness

Despite the advent of precision medicine and immunotherapy, mortality due to lung cancer remains high. The sonic hedgehog (SHH) cascade and its key terminal factor, glioma-associated oncogene homolog 1 (GLI1), play a pivotal role in the stemness and drug resistance of lung cancer. Here, we investigated the molecular mechanism of non-canonical aberrant GLI1 upregulation. The SHH cascade was upregulated in stem spheres and chemo-resistant lung cancer cells and was accountable for drug resistance against multiple chemotherapy regimens. GLI1 and the long non-coding RNA SOX2OT were positively regulated, and the GLI1-SOX2OT loop mediated the proliferation of parental and stem-like lung cancer cells. Further mechanistic investigation revealed that SOX2OT facilitated METTL3/14/IGF2BP2-mediated m6A modification and stabilization of the GLI1 mRNA. Additionally, SOX2OT upregulated METTL3/14/IGF2BP2 by sponging miR-186-5p. Functional analysis corroborated that GLI1 acted as a downstream target of METTL3/14/IGF2BP2, and GLI1 silencing could block the oncogenicity of lung cancer stem-like cells. Pharmacological inhibition of the loop remarkably inhibited the oncogenesis of lung cancer cells in vivo. Compared with paired adjacent normal tissues, lung cancer specimens exhibited consistently upregulated GLI1/SOX2OT/METTL3/14/IGF2BP2. The m6A-modified GLI1-SOX2OT loop may serve as a potential therapeutic target and prognostic predictor for lung cancer therapy and diagnosis in the clinic.

Signaling Switching from Hedgehog-GLI to MAPK Signaling Potentially Serves as a Compensatory Mechanism in Melanoma Cell Lines Resistant to GANT-61

Background: Melanoma represents the deadliest skin cancer due to its cell plasticity which results in high metastatic potential and chemoresistance. Melanomas frequently develop resistance to targeted therapy; therefore, new combination therapy strategies are required. Non-canonical signaling interactions between HH-GLI and RAS/RAF/ERK signaling were identified as one of the drivers of melanoma pathogenesis. Therefore, we decided to investigate the importance of these non-canonical interactions in chemoresistance, and examine the potential for HH-GLI and RAS/RAF/ERK combined therapy. Methods: We established two melanoma cell lines resistant to the GLI inhibitor, GANT-61, and characterized their response to other HH-GLI and RAS/RAF/ERK inhibitors. Results: We successfully established two melanoma cell lines resistant to GANT-61. Both cell lines showed HH-GLI signaling downregulation and increased invasive cell properties like migration potential, colony forming capacity, and EMT. However, they differed in MAPK signaling activity, cell cycle regulation, and primary cilia formation, suggesting different potential mechanisms responsible for resistance occurrence. Conclusions: Our study provides the first ever insights into cell lines resistant to GANT-61 and shows potential mechanisms connected to HH-GLI and MAPK signaling which may represent new hot spots for noncanonical signaling interactions.

The Hedgehog/GLI signaling pathway activates transcription of Slug (Snail2) in melanoma cells

In melanoma and other cancers, invasion, epithelial-to-mesenchymal transition, metastasis and cancer stem cell maintenance are regulated by transcription factors including the Snail family. Slug (Snail2) protein generally supports migration and apoptosis resistance. However, its role in melanoma is not completely understood. The present study investigated the transcriptional regulation of the SLUG gene in melanoma. It demonstrated that SLUG is under the control of the Hedgehog/GLI signaling pathway and is activated predominantly by the transcription factor GLI2. The SLUG gene promoter contains a high number of GLI-binding sites. Slug expression is activated by GLI factors in reporter assays and inhibited by GANT61 (GLI inhibitor) and cyclopamine (SMO inhibitor). SLUG mRNA levels are lowered by GANT61 as assessed by reverse transcription-quantitative PCR. Chromatin immunoprecipitation revealed abundant binding of factors GLI1-3 in the four subregions of the proximal SLUG promoter. Notably, melanoma-associated transcription factor (MITF) is an imperfect activator of the SLUG promoter in reporter assays, and downregulation of MITF had no effect on endogenous Slug protein levels. Immunohistochemical analysis confirmed the above findings and showed MITF-negative regions in metastatic melanoma that were positive for GLI2 and Slug. Taken together, the results demonstrated a previously unrecognized transcriptional activation mechanism of the SLUG gene, which may represent its main regulation of expression in melanoma cells.

The Network Zoo: a multilingual package for the inference and analysis of gene regulatory networks

Inference and analysis of gene regulatory networks (GRNs) require software that integrates multi-omic data from various sources. The Network Zoo (netZoo; netzoo.github.io) is a collection of open-source methods to infer GRNs, conduct differential network analyses, estimate community structure, and explore the transitions between biological states. The netZoo builds on our ongoing development of network methods, harmonizing the implementations in various computing languages and between methods to allow better integration of these tools into analytical pipelines. We demonstrate the utility using multi-omic data from the Cancer Cell Line Encyclopedia. We will continue to expand the netZoo to incorporate additional methods.

TGF-β Signaling Activation Confers Anlotinib Resistance in Gastric Cancer

BACKGROUND

Gastric cancer (GC) has always been a great threat to human health due to its aggressiveness and lethality. Anlotinib, a novel multi-target tyrosine kinase inhibitor (TKI), has been certified its anti-tumor effects on various tumors. Nonetheless, there are few studies on applying anlotinib as a treatment for GC. The underlying mechanism of acquired resistance during anlotinib administration remains unclear.

METHODS

We investigated the toxicologic effects of anlotinib on GC cells through CCK8, colony-forming, and flow cytometry assays in vitro and xenograft models in vivo. Anlotinib-resistant GC cells, AGS-R and MGC803-R, were generated and characterized by cell proliferation and apoptosis assays. The signaling pathways involved in anlotinib resistance were probed using Cignal™ Finder 10-Pathway Reporter Array. Western blot and dual-luciferase reporter assays were performed to confirm the relationships. The TGF-β inhibitor LY364947 was introduced to demonstrate the importance of TGF-β signaling in anlotinib resistance via a series of functional assays.

RESULTS

Anlotinib suppressed cell growth and induced apoptosis in vitro and inhibited tumorigenesis and metastasis in vivo, while its anti-tumor effects were impaired in anlotinib-resistant cells. The results of dual-luciferase reporter assays and western blot indicated TGF-β signaling was activated in anlotinib-resistant GC cells. LY364947 combined with Anlotinib exerted a better antineoplastic effect than monotherapy and considerably reversed the anlotinib resistance in GC.

CONCLUSIONS

Our findings suggested that TGF-β signaling may take a significant part in anlotinib resistance in GC. The suppression of TGF-β signaling may be a possible and promising approach for the GC oncotherapy when combined with anlotinib.

Intensity-modulated radiotherapy combined with systemic atezolizumab and bevacizumab in treatment of hepatocellular carcinoma with extrahepatic portal vein tumor thrombus: A preliminary multicenter single-arm prospective study

Background and aims

The efficacy and safety of systemic atezolizumab and bevacizumab (atezo/bev) in treatment of patients with unresectable hepatocellular carcinoma (HCC) have been demonstrated. However, the efficacy of this treatment in patients with HCC and extrahepatic portal vein tumor thrombus (ePVTT) is not satisfactory. This study aimed to study the efficacy and safety of combining intensity-modulated radiotherapy (IMRT) with systemic atezo/bev in treatment of these patients.

Methods

This multicenter prospective study included patients with ePVTT treated with IMRT combined with atezo/bev from March to September 2021 in three centers in China. The outcomes of this study included objective response rate (ORR), overall survival (OS), progression-free survival (PFS), time to progression (TTP), and association between response and tumor mutational burden (TMB). Treatment-related adverse events (TRAEs) were analyzed to assess safety.

Results

Of 30 patients in this study, the median follow-up was 7.4 months. Based on the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, the ORR was 76.6%, the median OS for the entire cohort was 9.8 months, the median PFS was 8.0 months, and the median TTP was not reached. This study failed to establish a significant correlation between TMB with any of the following outcomes, including ORR, OS, PFS or TTP. The most common TRAEs at all levels were neutropenia (46.7%), and the most common grade 3/4 TRAE was hypertension (16.7%). There was no treatment-related deaths.

Conclusions

IMRT combined with atezo/bev showed encouraging treatment efficacy with an acceptable safety profile, making this treatment to be a promising option for HCC patients with ePVTT. Further studies are required to support the findings of this preliminary study.

Clinical trial registration

http://www.chictr.org.cn, Identifier ChiCTR2200061793.

3-Bromopyruvate Suppresses the Malignant Phenotype of Vemurafenib-Resistant Melanoma Cells

(1) BRAF mutations are associated with high mortality and are a substantial factor in therapeutic decisions. Therapies targeting BRAF-mutated tumors, such as vemurafenib (PLX), have significantly improved the overall survival of melanoma patients. However, patient relapse and low response rates remain challenging, even with contemporary therapeutic alternatives. Highly proliferative tumors often rely on glycolysis to sustain their aggressive phenotype. 3-bromopyruvate (3BP) is a promising glycolysis inhibitor reported to mitigate resistance in tumors. This study aimed to evaluate the potential of 3BP as an antineoplastic agent for PLX-resistant melanoma treatment. (2) The effect of 3BP alone or in combination with PLX on viability, proliferation, colony formation, cell death, migration, invasion, epithelial-mesenchymal marker and metabolic protein expression, extracellular glucose and lactate, and reactive species were evaluated in two PLX-resistant melanoma cell lines. (3) 3BP treatment, which was more effective as monotherapy than combined with PLX, disturbed the metabolic and epithelial-mesenchymal profile of PLX-resistant cells, impairing their proliferation, migration, and invasion and triggering cell death. (4) 3BP monotherapy is a potent metabolic-disrupting agent against PLX-resistant melanomas, supporting the suppression of the malignant phenotype in this type of neoplasia.

HDAC11 activity contributes to MEK inhibitor escape in uveal melanoma

We previously demonstrated that pan-HDAC inhibitors could limit escape from MEK inhibitor (MEKi) therapy in uveal melanoma (UM) through suppression of AKT and YAP/TAZ signaling. Here, we focused on the role of specific HDACs in therapy adaptation. Class 2 UM displayed higher expression of HDACs 1, 2, and 3 than Class 1, whereas HDACs 6, 8, and 11 were uniformly expressed. Treatment of UM cells with MEKi led to modulation of multiple HDACs, with the strongest increases observed in HDAC11. RNA-seq analysis showed MEKi to decrease the expression of multiple HDAC11 target genes. Silencing of HDAC11 significantly reduced protein deacetylation, enhanced the apoptotic response to MEKi and reduced growth in long-term colony formation assays across multiple UM cell lines. Knockdown of HDAC11 led to decreased expression of TAZ in some UM cell lines, accompanied by decreased YAP/TAZ transcriptional activity and reduced expression of multiple YAP/TAZ target genes. Further studies showed this decrease in TAZ expression to be associated with increased LKB1 activation and modulation of glycolysis. In an in vivo model of uveal melanoma, silencing of HDAC11 limited the escape to MEKi therapy, an effect associated with reduced levels of Ki67 staining and increased cleaved caspase-3. We have demonstrated a novel role for adaptive HDAC11 activity in UM cells, that in some cases modulates YAP/TAZ signaling leading to MEKi escape.

RNA-seq and ChIP-seq Identification of Unique and Overlapping Targets of GLI Transcription Factors in Melanoma Cell Lines

BACKGROUND

Despite significant progress in therapy, melanoma still has a rising incidence worldwide, and novel treatment strategies are needed. Recently, researchers have recognized the involvement of the Hedgehog-GLI (HH-GLI) signaling pathway in melanoma and its consistent crosstalk with the MAPK pathway. In order to further investigate the link between the two pathways and to find new target genes that could be considered for combination therapy, we set out to find transcriptional targets of all three GLI proteins in melanoma.

METHODS

We performed RNA sequencing on three melanoma cell lines (CHL-1, A375, and MEL224) with overexpressed GLI1, GLI2, and GLI3 and combined them with the results of ChIP-sequencing on endogenous GLI1, GLI2, and GLI3 proteins. After combining these results, 21 targets were selected for validation by qPCR.

RESULTS

RNA-seq revealed a total of 808 differentially expressed genes (DEGs) for GLI1, 941 DEGs for GLI2, and 58 DEGs for GLI3. ChIP-seq identified 527 genes that contained GLI1 binding sites in their promoters, 1103 for GLI2 and 553 for GLI3. A total of 15 of these targets were validated in the tested cell lines, 6 of which were detected by both RNA-seq and ChIP-seq.

CONCLUSIONS

Our study provides insight into the unique and overlapping transcriptional output of the GLI proteins in melanoma. We suggest that our findings could provide new potential targets to consider while designing melanoma-targeted therapy.

Pilot study of bempegaldesleukin in combination with nivolumab in patients with metastatic sarcoma

PD-1 blockade (nivolumab) efficacy remains modest for metastatic sarcoma. In this paper, we present an open-label, non-randomized, non-comparative pilot study of bempegaldesleukin, a CD122-preferential interleukin-2 pathway agonist, with nivolumab in refractory sarcoma at Memorial Sloan Kettering/MD Anderson Cancer Centers (NCT03282344). We report on the primary outcome of objective response rate (ORR) and secondary endpoints of toxicity, clinical benefit, progression-free survival, overall survival, and durations of response/treatment. In 84 patients in 9 histotype cohorts, all patients experienced ≥1 adverse event and treatment-related adverse event; 1 death was possibly treatment-related. ORR was highest in angiosarcoma (3/8) and undifferentiated pleomorphic sarcoma (2/10), meeting predefined endpoints. Results of our exploratory investigation of predictive biomarkers show: CD8 + T cell infiltrates and PD-1 expression correlate with improved ORR; upregulation of immune-related pathways correlate with improved efficacy; Hedgehog pathway expression correlate with resistance. Exploration of this combination in selected sarcomas, and of Hedgehog signaling as a predictive biomarker, warrants further study in larger cohorts.

GLI-1 polymorphisms of Hedgehog pathway as novel risk and prognostic biomarkers in melanoma patients

In adult organisms, deregulation of the sonic hedgehog (SHH) signaling pathway is significantly correlated with different malignancies. Currently, data associating genetic polymorphisms in the SHH pathway with melanoma are scarce and largely unknown. The objective of our study was to elucidate an association between gene polymorphisms in the SHH pathway and prognosis of melanoma skin cancer patients. The current study investigated the association of PTCH1 (rs357564), SMO (rs2228617) and GLI1 (rs2228224, rs2228226), polymorphisms with melanoma predisposition and prognosis. Single-nucleotide polymorphisms were assessed by TaqMan SNP Genotyping Assays. The study involved 93 melanoma patients and 97 individuals in the control group. Melanoma patients with the variant mutant genotype GG of GLI1 rs2228226 polymorphism had poorer overall survival and recurrence-free survival (P = 0.0001 and P = 0.037, respectively). The multivariate analysis revealed that disease progression [hazard ratio (HR) = 14.434, P = 0.0001] and the GLI1 rs2228226 polymorphism (HR = 4.161, P = 0.006) persisted as independent prognostic factors. Mutated allele carriers (combined heterozygous and mutated genotypes) for GLI1 rs2228224 G and GLI1 rs2228226 G allele significantly increased melanoma risk [odds ratio (OR) = 2.261, P = 0.007; OR = 2.176, P = 0.010]. Our study demonstrated that genetic variants in GLI1, downstream member of the HH signaling pathway, are the risk factors for melanoma susceptibility and it can be a novel marker for melanoma prognosis. As a crucial SHH signaling member, GLI1 can also be regarded as a novel drug target for anti-cancer treatment in melanoma.

Upregulation of the novel lncRNA U731166 is associated with migration, invasion and vemurafenib resistance in melanoma

Our previous work using a melanoma progression model composed of melanocytic cells (melanocytes, primary and metastatic melanoma samples) demonstrated various deregulated genes, including a few known lncRNAs. Further analysis was conducted to discover novel lncRNAs associated with melanoma, and candidates were prioritized for their potential association with invasiveness or other metastasis‐related processes. In this sense, we found the intergenic lncRNA U73166 (ENSG00000230454) and decided to explore its effects in melanoma. For that, we silenced the lncRNA U73166 expression using shRNAs in a melanoma cell line. Next, we experimentally investigated its functions and found that migration and invasion had significantly decreased in knockdown cells, indicating an essential association of lncRNA U73166 for cancer processes. Additionally, using naïve and vemurafenib‐resistant cell lines and data from a patient before and after resistance, we found that vemurafenib‐resistant samples had a higher expression of lncRNA U73166. Also, we retrieved data from the literature that indicates lncRNA U73166 may act as a mediator of RNA processing and cell invasion, probably inducing a more aggressive phenotype. Therefore, our results suggest a relevant role of lncRNA U73166 in metastasis development. We also pointed herein the lncRNA U73166 as a new possible biomarker or target to help overcome clinical vemurafenib resistance.

Hedgehog signaling underlying tendon and enthesis development and pathology

Hedgehog (Hh) signaling has been widely acknowledged to play essential roles in many developmental processes, including endochondral ossification and growth plate maintenance. Furthermore, a rising number of studies have shown that Hh signaling is necessary for tendon enthesis development. Specifically, the well-tuned regulation of Hh signaling during development drives the formation of a mineral gradient across the tendon enthesis fibrocartilage. However, aberrant Hh signaling can also lead to pathologic heterotopic ossification in tendon or osteophyte formation at the enthesis. Therefore, the therapeutic potential of Hh signaling modulation for treating tendon and enthesis diseases remains uncertain. For example, increased Hh signaling may enhance tendon-to-bone healing by promoting the formation of mineralized fibrocartilage at the healing interface, but pathologic heterotopic ossification may also be triggered in the adjacent tendon. Further work is needed to elucidate the distinct functions of Hh signaling in the tendon and enthesis to support the development of therapies that target the pathway.

TGF-β Signaling and Resistance to Cancer Therapy

The transforming growth factor β (TGF-β) pathway, which is well studied for its ability to inhibit cell proliferation in early stages of tumorigenesis while promoting epithelial-mesenchymal transition and invasion in advanced cancer, is considered to act as a double-edged sword in cancer. Multiple inhibitors have been developed to target TGF-β signaling, but results from clinical trials were inconsistent, suggesting that the functions of TGF-β in human cancers are not yet fully explored. Multiple drug resistance is a major challenge in cancer therapy; emerging evidence indicates that TGF-β signaling may be a key factor in cancer resistance to chemotherapy, targeted therapy and immunotherapy. Finally, combining anti-TGF-β therapy with other cancer therapy is an attractive venue to be explored for the treatment of therapy-resistant cancer.

TOP1 modulation during melanoma progression and in adaptative resistance to BRAF and MEK inhibitors

In melanomas, therapy resistance can arise due to a combination of genetic, epigenetic and phenotypic mechanisms. Due to its crucial role in DNA supercoil relaxation, TOP1 is often considered an essential chemotherapeutic target in cancer. However, how TOP1 expression and activity might differ in therapy sensitive versus resistant cell types is unknown. Here we show that TOP1 expression is increased in metastatic melanoma and correlates with an invasive gene expression signature. More specifically, TOP1 expression is highest in cells with the lowest expression of MITF, a key regulator of melanoma biology. Notably, TOP1 and DNA Single-Strand Break Repair genes are downregulated in BRAFi- and BRAFi/MEKi-resistant cells and TOP1 inhibition decreases invasion markers only in BRAFi/MEKi-resistant cells. Thus, we show three different phenotypes related to TOP1 levels: i) non-malignant cells with low TOP1 levels; ii) metastatic cells with high TOP1 levels and high invasiveness; and iii) BRAFi- and BRAFi/MEKi-resistant cells with low TOP1 levels and high invasiveness. Together, these results highlight the potential role of TOP1 in melanoma progression and resistance.

The Role of Smoothened-Dependent and -Independent Hedgehog Signaling Pathway in Tumorigenesis

The Hedgehog (Hh)-glioma-associated oncogene homolog (GLI) signaling pathway is highly conserved among mammals, with crucial roles in regulating embryonic development as well as in cancer initiation and progression. The GLI transcription factors (GLI1, GLI2, and GLI3) are effectors of the Hh pathway and are regulated via Smoothened (SMO)-dependent and SMO-independent mechanisms. The SMO-dependent route involves the common Hh-PTCH-SMO axis, and mutations or transcriptional and epigenetic dysregulation at these levels lead to the constitutive activation of GLI transcription factors. Conversely, the SMO-independent route involves the SMO bypass regulation of GLI transcription factors by external signaling pathways and their interacting proteins or by epigenetic and transcriptional regulation of GLI transcription factors expression. Both routes of GLI activation, when dysregulated, have been heavily implicated in tumorigenesis of many known cancers, making them important targets for cancer treatment. Hence, this review describes the various SMO-dependent and SMO-independent routes of GLI regulation in the tumorigenesis of multiple cancers in order to provide a holistic view of the paradigms of hedgehog signaling networks involving GLI regulation. An in-depth understanding of the complex interplay between GLI and various signaling elements could help inspire new therapeutic breakthroughs for the treatment of Hh-GLI-dependent cancers in the future. Lastly, we have presented an up-to-date summary of the latest findings concerning the use of Hh inhibitors in clinical developmental studies and discussed the challenges, perspectives, and possible directions regarding the use of SMO/GLI inhibitors in clinical settings.

A PDZ Protein GIPC3 Positively Modulates Hedgehog Signaling and Melanoma Growth

The Hedgehog (Hh) pathway is essential for animal development but aberrant activation promotes cancer growth. Here we show that GIPC3, a PDZ domain-containing protein with putative adaptor protein function, positively modulates Hh target gene expression in normal fibroblasts and melanoma cells and supports melanoma tumor growth. Using overexpression and epistasis studies, we show that Gipc3 potentiates Hh transcriptional output and it modulates GLI-dependent transcription independently of Sufu. While we find GIPC3 protein does not interact with Hh pathway components, Ingenuity Pathway Analyses of GIPC3-interacting proteins identified by co-immunoprecipitation and mass spectrometry show an association with cancer pathogenesis. Subsequent interrogation of TCGA and The Human Protein Atlas databases reveals GIPC3 upregulation in many cancers. Using expression screens in selected groups of GIPC3-upregulated cancers with reported Hh pathway activation, we find a significant positive correlation of GIPC3 expression with Hh pathway components GLI1, GLI2, and GPR161, in melanoma lines. Consistently, GIPC3 knockdown in melanoma lines significantly reduces GLI1 and GLI2 expression, cell viability, colony formation, and allograft tumor growth. Our findings highlight previously unidentified roles of Gipc3 in potentiating Hh response and melanoma tumorigenesis, and suggest that GIPC3 modulation on Hh signaling may be targeted to reduce melanoma growth.

How Neural Crest Transcription Factors Contribute to Melanoma Heterogeneity, Cellular Plasticity, and Treatment Resistance

Cutaneous melanoma represents one of the deadliest types of skin cancer. The prognosis strongly depends on the disease stage, thus early detection is crucial. New therapies, including BRAF and MEK inhibitors and immunotherapies, have significantly improved the survival of patients in the last decade. However, intrinsic and acquired resistance is still a challenge. In this review, we discuss two major aspects that contribute to the aggressiveness of melanoma, namely, the embryonic origin of melanocytes and melanoma cells and cellular plasticity. First, we summarize the physiological function of epidermal melanocytes and their development from precursor cells that originate from the neural crest (NC). Next, we discuss the concepts of intratumoral heterogeneity, cellular plasticity, and phenotype switching that enable melanoma to adapt to changes in the tumor microenvironment and promote disease progression and drug resistance. Finally, we further dissect the connection of these two aspects by focusing on the transcriptional regulators MSX1, MITF, SOX10, PAX3, and FOXD3. These factors play a key role in NC initiation, NC cell migration, and melanocyte formation, and we discuss how they contribute to cellular plasticity and drug resistance in melanoma.

The Role of Notch, Hedgehog, and Wnt Signaling Pathways in the Resistance of Tumors to Anticancer Therapies

Resistance to therapy is the major hurdle in the current cancer management. Cancer cells often rewire their cellular process to alternate mechanisms to resist the deleterious effect mounted by different therapeutic approaches. The major signaling pathways involved in the developmental process, such as Notch, Hedgehog, and Wnt, play a vital role in development, tumorigenesis, and also in the resistance to the various anticancer therapies. Understanding how cancer utilizes these developmental pathways in acquiring the resistance to the multi-therapeutic approach cancer can give rise to a new insight of the anti-therapy resistance mechanisms, which can be explored for the development of a novel therapeutic approach. We present a brief overview of Notch, Hedgehog, and Wnt signaling pathways in cancer and its role in providing resistance to various cancer treatment modalities such as chemotherapy, radiotherapy, molecular targeted therapy, and immunotherapy. Understanding the importance of these molecular networks will provide a rational basis for novel and safer combined anticancer therapeutic approaches for the improvement of cancer treatment by overcoming drug resistance.

Activation of AMPK sensitizes medulloblastoma to Vismodegib and overcomes Vismodegib-resistance

Vismodegib, a Smoothened antagonist, is clinically approved for treatment of human basal cell carcinoma (BCC), in the clinical trials of medulloblastoma (MB) and other cancers. However, a significant proportion of these tumors fail to respond to Vismodegib after a period of treatment. Here, we find that AMPK agonists, A769662, and Metformin, can inhibit GLI1 activity and synergize with Vismodegib to suppress MB cell growth invitro and invivo. Furthermore, combination of AMPK agonists with Vismodegib is effective in overcoming Vismodegib‐resistant MB. This is the first report demonstrating that combining AMPK agonist (Metformin) and SHH pathway inhibitor (Vismodegib) confers synergy for MB treatment and provides an effective chemotherapeutic regimen that can be used to overcome resistance to Vismodegib in SHH‐driven cancers.

Elucidating molecular mechanisms of acquired resistance to BRAF inhibitors in melanoma using a microfluidic device and deep sequencing

BRAF inhibitors (e.g., vemurafenib) are widely used to treat metastatic melanoma with the BRAF V600E mutation. The initial response is often dramatic, but treatment resistance leads to disease progression in the majority of cases. Although secondary mutations in the mitogen-activated protein kinase signaling pathway are known to be responsible for this phenomenon, the molecular mechanisms governing acquired resistance are not known in more than half of patients. Here we report a genome- and transcriptome-wide study investigating the molecular mechanisms of acquired resistance to BRAF inhibitors. A microfluidic chip with a concentration gradient of vemurafenib was utilized to rapidly obtain therapy-resistant clones from two melanoma cell lines with the BRAF V600E mutation (A375 and SK-MEL-28). Exome and transcriptome data were produced from 13 resistant clones and analyzed to identify secondary mutations and gene expression changes. Various mechanisms, including phenotype switching and metabolic reprogramming, have been determined to contribute to resistance development differently for each clone. The roles of microphthalmia-associated transcription factor, the master transcription factor in melanocyte differentiation/dedifferentiation, were highlighted in terms of phenotype switching. Our study provides an omics-based comprehensive overview of the molecular mechanisms governing acquired resistance to BRAF inhibitor therapy.

Organotypic Models in Drug Development "Tumor Models and Cancer Systems Biology for the Investigation of Anticancer Drugs and Resistance Development"

The landscape of cancer treatment has improved over the past decades, aiming to reduce systemic toxicity and enhance compatibility with the quality of life of the patient. However, at the therapeutic level, metastatic cancer remains hugely challenging, based on the almost inevitable emergence of therapy resistance. A small subpopulation of cells able to survive drug treatment termed the minimal residual disease may either harbor resistance-associated mutations or be phenotypically resistant, allowing them to regrow and become the dominant population in the therapy-resistant tumor. Characterization of the profile of minimal residual disease represents the key to the identification of resistance drivers that underpin cancer evolution. Therapeutic regimens must, therefore, be dynamic and tailored to take into account the emergence of resistance as tumors evolve within a complex microenvironment in vivo. This requires the adoption of new technologies based on the culture of cancer cells in ways that more accurately reflect the intratumor microenvironment, and their analysis using omics and system-based technologies to enable a new era in the diagnostics, classification, and treatment of many cancer types by applying the concept "from the cell plate to the patient." In this chapter, we will present and discuss 3D model building and use, and provide comprehensive information on new genomic techniques that are increasing our understanding of drug action and the emergence of resistance.

Skin Equivalent Models: Protocols for In Vitro Reconstruction for Dermal Toxicity Evaluation

This chapter presents the protocols for developing of skin equivalents (SE) and reconstructed human epidermis (RHE) models for dermal toxicity evaluation as an alternative method to animal use in research. It provides a detailed protocol for the in vitro reconstruction of human skin from primary keratinocytes, melanocytes, and fibroblasts obtained from foreskin biopsies, including the procedures for reconstruction of a stratified epidermis on a polyester membrane. SE and RHE developed through these methods have been proven suitable not only for dermal toxicity studies, but also for investigating of pathological conditions in the skin, such as diabetes and invasion of melanoma.

Loss of ACK1 Upregulates EGFR and Mediates Resistance to BRAF Inhibition

Targeted BRAF(V600E) suppression by selective BRAF inhibitors (BRAFis; e.g., vemurafenib and dabrafenib) has led to a sea change in the treatment of metastatic melanoma. Despite frequent upfront responses, acquired resistance has compromised long-term applicability. Among the various mechanisms of resistance, activation of multiple receptor tyrosine kinases is a known critical factor that contributes to vemurafenib resistance⁠. EGFR activation has been recurrently identified in a set of vemurafenib-resistant melanomas, but little is known about how EGFR, or possibly other receptor tyrosine kinases, becomes activated. Here, we report that ACK1, a protein kinase that modulates EGFR turnover, is downregulated in vemurafenib-resistant melanoma cells. We also found that ACK1 depletion with short hairpin RNA decreased EGFR degradation when activated by epidermal growth factor, increased EGFR protein expression, and conferred resistance to BRAFis both in vitro and in vivo. Vemurafenib resistance mediated by ACK1 inhibition can be reversed by the EGFR inhibitor gefitinib. Our data indicate that ACK1 loss may be a post-transcriptional mechanism that increases EGFR signaling and contributes to drug resistance.

miR-524-5p reduces the progression of the BRAF inhibitor-resistant melanoma

BRAF inhibitors were approved for the treatment of BRAF-mutant melanoma. However, most patients acquire the resistance to BRAF inhibitors after several months of treatment. miR-524-5p is considered as a tumor suppressor in many cancers, including melanoma. In this study, we investigated the biological functions of miR-524-5p in melanoma with acquired resistance to BRAF inhibitor and evaluated the endogenous miR-524-5p expression as a biomarker for melanoma. The results showed that the expression of miR-524-5p was 0.481-fold lower in melanoma tissues (n = 117) than in nevus tissues (n = 40). Overexpression of miR-524-5p significantly reduced proliferative, anchorage-independent growth, migratory and invasive abilities of BRAF inhibitor-resistant melanoma cells. Moreover, the introduction of miR-524-5p led to a reduced development of BRAF inhibitor-resistant melanoma in vivo. Remarkably, the MAPK/ERK signaling pathway was decreased after treatment with miR-524-5p. Furthermore, next-generation sequencing analysis implied that the complement system, leukocyte extravasation, liver X receptor/retinoid-X-receptor activation, and cAMP-mediated signaling may be related to miR-524-5p-induced pathways in the resistant cells. The miR-524-5p level was higher on average in complete response and long-term partial response patients than in progressive disease and short-term partial response patients treated with BRAF inhibitors. Our results proposed that miR-524-5p could be considered as a target for treatment BRAF inhibitor-resistant melanoma and a prognostic marker in the response of patients to BRAF inhibitors for melanoma.

HAS3-induced extracellular vesicles from melanoma cells stimulate IHH mediated c-Myc upregulation via the hedgehog signaling pathway in target cells

Intercellular communication is fundamental to the survival and maintenance of all multicellular systems, whereas dysregulation of communication pathways can drive cancer progression. Extracellular vesicles (EVs) are mediators of cell-to-cell communication that regulate a variety of cellular processes involved in tumor progression. Overexpression of a specific plasma membrane enzyme, hyaluronan synthase 3 (HAS3), is one of the factors that can induce EV shedding. HAS3, and particularly its product hyaluronan (HA), are carried by EVs and are known to be associated with the tumorigenic properties of cancer cells. To elucidate the specific effects of cancerous, HAS3-induced EVs on target cells, normal human keratinocytes and melanoma cells were treated with EVs derived from GFP-HAS3 expressing metastatic melanoma cells. We found that the HA receptor CD44 participated in the regulation of EV binding to target cells. Furthermore, GFP-HAS3-positive EVs induced HA secretion, proliferation and invasion of target cells. Our results suggest that HAS3-EVs contains increased quantities of IHH, which activates the target cell hedgehog signaling cascade and leads to the activation of c-Myc and regulation of claspin expression. This signaling of IHH in HAS3-EVs resulted in increased cell proliferation. Claspin immunostaining correlated with HA content in human cutaneous melanocytic lesions, supporting our in vitro findings and suggesting a reciprocal regulation between claspin expression and HA synthesis. This study shows for the first time that EVs originating from HAS3 overexpressing cells carry mitogenic signals that induce proliferation and epithelial-to-mesenchymal transition in target cells. The study also identifies a novel feedback regulation between the hedgehog signaling pathway and HA metabolism in melanoma, mediated by EVs carrying HA and IHH.

A Novel Therapeutic siRNA Nanoparticle Designed for Dual-Targeting CD44 and Gli1 of Gastric Cancer Stem Cells

Purpose

Gastric cancer stem cells (CSCs) are important for the initiation, growth, recurrence, and metastasis of gastric cancer, due to their chemo-resistance and indefinite proliferation. Herein, to eliminate gastric CSCs, we developed novel CSC-targeting glioma-associated oncogene homolog 1 (Gli1) small interfering RNA (siRNA) nanoparticles that are specifically guided by a di-stearoyl-phosphatidyl-ethanolamine- hyaluronic-acid (DSPE-HA) single-point conjugate, as an intrinsic ligand of the CD44 receptor. We refer to these as targeting Gli1 siRNA nanoparticles.

Methods

We used the reductive amination reaction method for attaching amine groups of DSPE to aldehydic group of hyaluronic acid (HA) at the reducing end, to synthesize the DSPE-HA single-point conjugate. Next, targeting Gli1 siRNA nanoparticles were prepared using the layer-by-layer assembly method. We characterized the stem cellular features of targeting Gli1 siRNA nanoparticles, including their targeting efficiency, self-renewal capacity, the migration and invasion capacity of gastric CSCs, and the penetration ability of 3D tumor spheroids. Next, we evaluated the therapeutic efficacy of the targeting Gli1 siRNA nanoparticles by using in vivo relapsed tumor models of gastric CSCs.

Results

Compared with the multipoint conjugates, DSPE-HA single-point conjugates on the surface of nanoparticles showed significantly higher binding affinities with CD44. The targeting Gli1 siRNA nanoparticles significantly decreased Gli1 protein expression, inhibited CSC tumor spheroid and colony formation, and suppressed cell migration and invasion. Furthermore, in vivo imaging demonstrated that targeting Gli1 siRNA nanoparticles accumulated in tumor tissues, showing significant antitumor recurrence efficacy in vivo.

Conclusion

In summary, our targeting Gli1 siRNA nanoparticles significantly inhibited CSC malignancy features by specifically blocking Hedgehog (Hh) signaling both in vitro and in vivo, suggesting that this novel siRNA delivery system that specifically eliminates gastric CSCs provides a promising targeted therapeutic strategy for gastric cancer treatment.

Itraconazole inhibits the Hedgehog signaling pathway thereby inducing autophagy-mediated apoptosis of colon cancer cells

Itraconazole is as an antifungal medication used to treat systemic fungal infections. Recently, it has been reported to be effective in suppressing tumor growth by inhibiting the Hedgehog signaling pathway and angiogenesis. In the present study, we investigated whether itraconazole induces autophagy-mediated cell death of colon cancer cells through the Hedgehog signaling pathway. Cell apoptosis and cell cycle distribution of the colon cancer cell lines SW-480 and HCT-116 were detected by flow cytometry and terminal TUNEL assay. Autophagy and signal proteins were detected by western blotting and cell proliferation-associated antigen Ki-67 was measured using immunohistochemistry. The images of autophagy flux and formation of autophagosomes were observed by laser scanning confocal and/or transmission electron microscopy. Colon cancer cell xenograft mouse models were also established. Itraconazole treatment inhibited cell proliferation via G1 cell cycle arrest as well as autophagy-mediated apoptosis of SW-480 and HCT-116 colon cancer cells. In addition, the Hedgehog pathway was found to be involved in activation of itraconazole-mediated autophagy. After using the Hedgehog agonist recombinant human Sonic Hedgehog (rhshh), itraconazole could counteract the activation of rhshh. Moreover, treatment with itraconazole produced significant cancer inhibition in HCT-116-bearing mice. Thus, itraconazole may be a potential and effective therapy for the treatment of colon cancer.

Silencing TCF4 Sensitizes Melanoma Cells to Vemurafenib Through Inhibiting GLUT3-Mediated Glycolysis

Background

Vemurafenib is a selective BRAF inhibitor with significant early effects in melanoma, but resistance will develop with the duration of treatment. Therefore, overcoming vemurafenib resistance can effectively improve the survival rate of melanoma. The transcriptional activity of TCF4 is necessary to maintain the malignant phenotype of cancer cells. However, the effect of TCF4 on melanoma sensitivity to vemurafenib and the underlying mechanism is unclear.

Methods

Vemurafenib-resistant A375 (A375/Vem) and SK-Mel-28 (SK-Mel-28/Vem) cells were constructed by administering increasing concentrations of vemurafenib, and the expression of TCF4 was examined in parent and vemurafenib-resistant cells. TCF4 loss-function cells models were established in A375/Vem and SK-Mel-28/Vem cells, respectively. Cell survival, clone formation, and cell apoptosis were assessed. The downstream target gene of TCF4 was verified by chromatin immunoprecipitation. Finally, the effect of TCF4 on melanoma cells glycolysis was investigated and were performed.

Results

TCF4 expression was increased in vemurafenib-resistant melanoma cells, and knocking down TCF4 could promote the sensitivity of melanoma cells to vemurafenib. Mechanism investigation revealed that TCF4 could interact with GLUT3 and silencing TCF4 could inhibit GLUT3 expression. In addition, overexpression of GLUT3 reversed the growth and glycolysis of tumor cells that were inhibited by TCF4 knockdown.

Conclusion

Our study demonstrates that TCF4 downregulation sensitizes melanoma cells to vemurafenib through inhibiting GLUT3-mediated glycolysis. These findings support TCF4 as an oncogene and provide new mechanism by which TCF4 confers chemotherapy resistance in melanoma.

SETDB2 promoted breast cancer stem cell maintenance by interaction with and stabilization of ΔNp63α protein

The histone H3K9 methyltransferase SETDB2 is involved in cell cycle dysregulation in acute leukemia and has oncogenic roles in gastric cancer. In our study, we found that SETDB2 plays essential roles in breast cancer stem cell maintenance. Depleted SETDB2 significantly decreased the breast cancer stem cell population and mammosphere formation in vitro and also inhibited breast tumor initiation and growth in vivo. Restoring SETDB2 expression rescued the defect in breast cancer stem cell maintenance. A mechanistic analysis showed that SETDB2 upregulated the transcription of the ΔNp63α downstream Hedgehog pathway gene. SETDB2 also interacted with and methylated ΔNp63α, and stabilized ΔNp63α protein. Restoring ΔNp63α expression rescued the breast cancer stem cell maintenance defect which mediated by SETDB2 knockdown. In conclusion, our study reveals a novel function of SETDB2 in cancer stem cell maintenance in breast cancer.

Indoleamine 2,3-dioxygenase in melanoma progression and BRAF inhibitor resistance

Indoleamine 2,3-dioxygenase (IDO) is associated with the progression of many types of tumors, including melanoma. However, there is limited information about IDO modulation on tumor cell itself and the effect of BRAF inhibitor (BRAFi) treatment and resistance. Herein, IDO expression was analyzed in different stages of melanoma development and progression linked to BRAFi resistance. IDO expression was increased in primary and metastatic melanomas from patients' biopsies, especially in the immune cells infiltrate. Using a bioinformatics approach, we also identified an increase in the IDO mRNA in the vertical growth and metastatic phases of melanoma. Using in silico analyses, we found that IDO mRNA was increased in BRAFi resistance. In an in vitro model, IDO expression and activity induced by interferon-gamma (IFNγ) in sensitive melanoma cells was decreased by BRAFi treatment. However, cells that became resistant to BRAFi presented random IDO expression levels. Also, we identified that treatment with the IDO inhibitor, 1-methyltryptophan (1-MT), was able to reduce clonogenicity for parental and BRAFi-resistant cells. In conclusion, our results support the hypothesis that the decreased IDO expression in tumor cells is one of the many additional outcomes contributing to the therapeutic effects of BRAFi. Still, the IDO production changeability by the BRAFi-resistant cells reiterates the complexity of the response arising from resistance, making it not possible, at this stage, to associate IDO expression in tumor cells with resistance. On the other hand, the maintenance of 1-MT off-target effect endorses its use as an adjuvant treatment of melanoma that has become BRAFi-resistant.

Up-regulation of GLI1 in vincristine-resistant rhabdomyosarcoma and Ewing sarcoma

Background

The clinical significance of GLI1 expression either through canonical Hedgehog signal transduction or through non-canonical mechanisms in rhabdomyosarcoma (RMS) or Ewing sarcoma (EWS) is incompletely understood. We tested a role for Hedgehog (HH) signal transduction and GL11 expression in development of vincristine (VCR) resistance in RMS and EWS.

Methods

We characterized baseline expression and activity of HH pathway components in 5 RMS (RD, Rh18, Ruch-2, Rh30, and Rh41) and 5 EWS (CHLA9, CHLA10, TC32, CHLA258, and TC71) cell lines. We then established VCR-resistant RMS and EWS cell lines by exposing cells to serially increasing concentrations of VCR and determining the IC₅₀. We defined resistance as a ≥ 30-fold increase in IC₅₀ compared with parental cells. We determined changes in gene expression in the VCR-resistant cells compared with parental cells using an 86-gene cancer drug resistance array that included GLI1 and tested the effect of GLI1 inhibition with GANT61 or GLI1 siRNA on VCR resistance.

Results

We found evidence for HH pathway activity and GLI1 expression in RMS and EWS cell lines at baseline, and evidence that GLI1 contributes to survival and proliferation of these sarcoma cells. We were able to establish 4 VCR-resistant cell lines (Ruch-2VR, Rh30VR, Rh41VR, and TC71VR). GLI1 was significantly up-regulated in the Rh30VR, Rh41VR, and TC71VR cells. The only other gene in the drug resistance panel that was significantly up-regulated in each of these VCR-resistant cell lines compared with their corresponding parental cells was the GLI1 direct target and multidrug resistance gene, ATP-binding cassette sub-family B member 1 (MDR1). We established major vault protein (MVP), which was up-regulated in both vincristine-resistant alveolar RMS cell lines (Rh30VR and Rh41VR), as another direct target of GLI1 during development of drug resistance. Treatment of the VCR-resistant cell lines with the small molecule inhibitor GANT61 or GLI1 siRNA together with VCR significantly decreased cell viability at doses that did not reduce viability individually.

Conclusions

These experiments demonstrate that GLI1 up-regulation contributes to VCR resistance in RMS and EWS cell lines and suggest that targeting GLI1 may benefit patients with RMS or EWS by reducing multidrug resistance.

Loss of Spry1 reduces growth of BRAFV600-mutant cutaneous melanoma and improves response to targeted therapy

Mitogen-activated protein kinase (MAPK) pathway activation is a central step in BRAF^V600-mutant cutaneous melanoma (CM) pathogenesis. In the last years, Spry1 has been frequently described as an upstream regulator of MAPK signaling pathway. However, its specific role in BRAF^V600-mutant CM is still poorly defined. Here, we report that Spry1 knockdown (Spry1^KO) in three BRAF^V600-mutant CM cell lines markedly induced cell cycle arrest and apoptosis, repressed cell proliferation in vitro, and impaired tumor growth in vivo. Furthermore, our findings indicated that Spry1^KO reduced the expression of several markers of epithelial–mesenchymal transition, such as MMP-2 both in vitro and in vivo. These effects were associated with a sustained and deleterious phosphorylation of ERK1/2. In addition, p38 activation along with an increase in basal ROS levels were found in Spry1^KO clones compared to parental CM cell lines, suggesting that BRAF^V600-mutant CM may restrain the activity of Spry1 to avoid oncogenic stress and to enable tumor growth. Consistent with this hypothesis, treatment with the BRAF inhibitor (BRAFi) vemurafenib down-regulated Spry1 levels in parental CM cell lines, indicating that Spry1 expression is sustained by the MAPK/ERK signaling pathway in a positive feedback loop that safeguards cells from the potentially toxic effects of ERK1/2 hyperactivation. Disruption of this feedback loop rendered Spry1^KO cells more susceptible to apoptosis and markedly improved response to BRAFi both in vitro and in vivo, as a consequence of the detrimental effect of ERK1/2 hyperactivation observed upon Spry1 abrogation. Therefore, targeting Spry1 might offer a treatment strategy for BRAF^V600-mutant CM by inducing the toxic effects of ERK-mediated signaling.

TKP, a serine protease extracted from Trichosanthes kirilowii, inhibits the migration and invasion of colorectal adenocarcinoma cells by targeting Wnt/β-catenin and Hedgehog/Gli1 signalings

Trichosanthes kirilowii, which is a type of Liana from cucurbitaceous family, possesses many bioactive constituents and therefore has multifarious pharmacological functions. TKP, which is a serine protease extracted from the fruit of Trichosanthes kirilowii, has been reported to possess potential anticancer activity. However, the effects of TKP on cancer cell migration and invasion are still unknown. Here, we reported that TKP could inhibit the migration and invasion abilities of colorectal cancer cells. In addition, the mRNA, protein expression levels, and activities of migration and invasion-related proteins MMP2 and MMP9 were decreased in TKP-treated cells. Mechanistically, TKP treatment repressed Wnt/β-catenin and Hedgehog/Gli1 signaling cascades. However, the addition of lithium chloride or the transfection of plasmid pcDNA3.1-V5-HisA-Gli1 reversed the impacts of TKP on MMP2, MMP9, cell migration, and invasion. These results indicated that TKP suppressed the migration and invasion of colorectal cancer cells through blocking Wnt/β-catenin and Hedgehog/Gli1 pathways-mediated MMP2 and MMP9.

MiR-326: Promising Biomarker for Cancer

MicroRNAs (miRNAs) are small non-coding and highly conserved RNAs that act in biological processes including cell proliferation, invasion, apoptosis, metabolism, signal transduction, and tumorigenesis. The previously identified miRNA-326 (miR-326) has been reported to participate in cellular apoptosis, tumor growth, cell invasion, embryonic development, immunomodulation, chemotherapy resistance, and oncogenesis. This review presents a detailed overview of what is known about the effects of miR-326 on cell invasion, metastasis, drug resistance, proliferation, apoptosis, and its involvement in signaling pathways.

Decitabine limits escape from MEK inhibition in uveal melanoma

MEK inhibitors (MEKi) demonstrate anti-proliferative activity in patients with metastatic uveal melanoma, but responses are short-lived. In the present study, we evaluated the MEKi trametinib alone and in combination with drugs targeting epigenetic regulators, including DOT1L, EZH2, LSD1, DNA methyltransferases, and histone acetyltransferases. The DNA methyltransferase inhibitor (DNMTi) decitabine effectively enhanced the anti-proliferative activity of trametinib in cell viability, colony formation, and 3D organoid assays. RNA-Seq analysis showed the MEKi-DNMTi combination primarily affected the expression of genes involved in G1 and G2/2M checkpoints, cell survival, chromosome segregation and mitotic spindle. The DNMTi-MEKi combination did not appear to induce a DNA damage response (as measured by γH2AX foci) or senescence (as measured by β-galactosidase staining) compared to either MEKi or DNMTi alone. Instead, the combination increased expression of the CDK inhibitor p21 and the pro-apoptotic protein BIM. In vivo, the DNMTi-MEKi combination was more effective at suppressing growth of MP41 uveal melanoma xenografts than either drug alone. Our studies indicate that DNMTi may enhance the activity of MEKi in uveal melanoma.

GLI1 is increased in ovarian endometriosis and regulates migration, invasion and proliferation of human endometrial stromal cells in endometriosis

BACKGROUND

Endometriosis is a benign gynecological disorder which shares certain characteristics with malignant tumor like migration, invasion and proliferation. Glioma-associated oncogene homolog 1 (GLI1) has been implicated in some cancers including endometrial cancer, however, its role in endometriosis remains unknown.

METHODS

The aim of this study was to explore the expression pattern of GLI1 in endometriosis, and further investigate the effect of GLI1 regulation on human endometrial stromal cells. The expression of GLI1 in normal endometrium and ectopic tissues was analyzed by immunohistochemistry, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot. The Short hairpin RNA (ShRNA) intervention technique and GLI1 inhibitor GANT-61 were used to silence GLI1. The expression levels of GLI1, MMP2 and MMP9 was detected by qRT-PCR and western blot. The migration and invasion ability of human endometrial stromal cells was determined by wound healing assay and transwell migration/invasion assay. The viability and proliferation potentiality of cells was detected by MTT assays and colony formation assay, respectively.

RESULTS

We found that the expression of GLI1 mRNA and protein were significantly higher in ectopic endometrium from patients with endometriosis. Our analyses also show that GLI1 downregulation attenuated cells migration, invasion and proliferation abilities. What's more, reduced expression of GLI1 inhibited the expression of matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9).

CONCLUSIONS

Our findings suggest that high levels of GLI1 may contribute to the development of endometriosis by promoting cell migration, invasion and proliferation involving regulation of MMP2 and MMP9 expression. Therefore, inhibition of GLI1 might be a novel potential therapeutic approach to the treatment of endometriosis, which sheds new light on our understanding of the pathogenesis of endometriosis.

Attenuation of hedgehog/GLI signaling by NT1721 extends survival in pancreatic cancer

BACKGROUND

Pancreatic cancer is one of the most lethal malignancies due to frequent late diagnosis, aggressive tumor growth and metastasis formation. Continuously raising incidence rates of pancreatic cancer and a lack of significant improvement in survival rates over the past 30 years highlight the need for new therapeutic agents. Thus, new therapeutic agents and strategies are urgently needed to improve the outcome for patients with pancreatic cancer. Here, we evaluated the anti-tumor activity of a new natural product-based epidithiodiketopiperazine, NT1721, against pancreatic cancer.

METHODS

We characterized the anticancer efficacy of NT1721 in multiple pancreatic cancer cell lines in vitro and in two orthotopic models. We also compared the effects of NT1721 to clinically used hedgehog inhibitors and the standard-of-care drug, gemcitabine. The effect of NT1721 on hedgehog/GLI signaling was assessed by determining the expression of GLI and GLI target genes both in vitro and in vivo.

RESULTS

NT1721 displayed IC₅₀ values in the submicromolar range in multiple pancreatic cancer cell lines, while largely sparing normal pancreatic epithelial cells. NT1721 attenuated hedgehog/GLI signaling through downregulation of GLI1/2 transcription factors and their downstream target genes, which reduced cell proliferation and invasion in vitro and significantly decreased tumor growth and liver metastasis in two preclinical orthotopic mouse models of pancreatic cancer. Importantly, treatment with NT1721 significantly improved survival times of mice with pancreatic cancer compared to the standard-of-care drug, gemcitabine.

CONCLUSIONS

Favorable therapeutics properties, i.e. 10-fold lower IC₅₀ values than clinically used hedgehog inhibitors (vismodegib, erismodegib), a 90% reduction in liver metastasis and significantly better survival times compared to the standard-of-care drug, gemcitabine, provide a rational for testing NT1721 in the clinic either as a single agent or possibly in combination with gemcitabine or other therapeutic agents in PDAC patients overexpressing GLI1/2. This could potentially result in promising new treatment options for patients suffering from this devastating disease.

GLI1 activation by non-classical pathway integrin αvβ3/ERK1/2 maintains stem cell-like phenotype of multicellular aggregates in gastric cancer peritoneal metastasis

Peritoneal metastasis is one of the most important causes of postoperative death in patients with gastric cancer, and the exact mechanism remains unclear. The proliferation of multicellular aggregates of exfoliated malignant gastric cells in the abdominal cavity is the focus of current research. However, the mechanism how gastric cancer multicellular aggregates survive remains unclear. In this study, we demonstrated that multicellular aggregates of exfoliated gastric cancer cells in the abdominal cavity expressed a stem cell-Like phenotype. We found that Integrin α_vβ₃ not only mediated adhesion of gastric cancer multicellular aggregates to form independent functional units, but also maintained their stem cell-like phenotype by the non-classical pathway Integrin α_vβ₃/ERK1/2/GLI1. In addition, ERK1/2 directly regulates the transcriptional activity of GLI1. GLI1 is a key effector of the Integrin α_vβ₃ pathway in regulating stem cell-like phenotype in multicellular aggregates. Our data indicates that although there is a crosstalk between the non-classical Integrin α_vβ₃ pathway and the classical Hedgehog pathway, the activation of GLI1 is almost independent of the Hedgehog pathway in multicellular aggregates of gastric cancer cells. Our study provides a basis for blocking GLI1 activity in the prevention and treatment of peritoneal metastases of gastric cancer.

HDAC Inhibition Enhances the In Vivo Efficacy of MEK Inhibitor Therapy in Uveal Melanoma

PURPOSE

The clinical use of MEK inhibitors in uveal melanoma is limited by the rapid acquisition of resistance. This study has used multiomics approaches and drug screens to identify the pan-HDAC inhibitor panobinostat as an effective strategy to limit MEK inhibitor resistance.Experimental Design: Mass spectrometry-based proteomics and RNA-Seq were used to identify the signaling pathways involved in the escape of uveal melanoma cells from MEK inhibitor therapy. Mechanistic studies were performed to evaluate the escape pathways identified, and the efficacy of the MEK-HDAC inhibitor combination was demonstrated in multiple in vivo models of uveal melanoma.

RESULTS

We identified a number of putative escape pathways that were upregulated following MEK inhibition, including the PI3K/AKT pathway, ROR1/2, and IGF-1R signaling. MEK inhibition was also associated with increased GPCR expression, particularly the endothelin B receptor, and this contributed to therapeutic escape through ET-3-mediated YAP signaling. A screen of 289 clinical grade compounds identified HDAC inhibitors as potential candidates that suppressed the adaptive YAP and AKT signaling that followed MEK inhibition. In vivo, the MEK-HDAC inhibitor combination outperformed either agent alone, leading to a long-term decrease of tumor growth in both subcutaneous and liver metastasis models and the suppression of adaptive PI3K/AKT and YAP signaling.

CONCLUSIONS

Together, our studies have identified GPCR-mediated YAP activation and RTK-driven AKT signaling as key pathways involved in the escape of uveal melanoma cells from MEK inhibition. We further demonstrate that HDAC inhibition is a promising combination partner for MEK inhibitors in advanced uveal melanoma.

MITF-the first 25 years

In this review, Goding and Arnheiter present the current understanding of MITF's role and regulation in development and disease and highlight key areas where our knowledge of MITF regulation and function is limited.

All transcription factors are equal, but some are more equal than others. In the 25 yr since the gene encoding the microphthalmia-associated transcription factor (MITF) was first isolated, MITF has emerged as a key coordinator of many aspects of melanocyte and melanoma biology. Like all transcription factors, MITF binds to specific DNA sequences and up-regulates or down-regulates its target genes. What marks MITF as being remarkable among its peers is the sheer range of biological processes that it appears to coordinate. These include cell survival, differentiation, proliferation, invasion, senescence, metabolism, and DNA damage repair. In this article we present our current understanding of MITF's role and regulation in development and disease, as well as those of the MITF-related factors TFEB and TFE3, and highlight key areas where our knowledge of MITF regulation and function is limited.

Influence of SHH/GLI1 axis on EMT mediated migration and invasion of breast cancer cells

Sonic Hedgehog signaling is critical for breast morphogenesis and cancer. The present study was conducted to explore the influence of SHH/GLI1 axis on epithelial mesenchymal transition and invasion in breast cancer cells. SHH/GLI1 positive samples demonstrated high expression of Snail and Vimentin with relatively low expression of E-cadherin. Overexpression of Vimentin and Snail in SHH/GLI1 positive patients was also associated with poor overall survival. Interestingly, GANT61 (GLI1 inhibitor) exposure significantly reduced cell viability and induced apoptosis at 10 µM. Suppression of Hedgehog pathway either by CRISPR mediated SHH knock out or GANT61 altered regulation of EMT markers in breast cancer cells. Moreover, in-activation of SHH/GLI1 axis also significantly restricted cell migration and invasiveness. These findings suggest that targeting SHH/GLI1 axis alters expression of EMT markers and abrogates neoplastic invasion in breast cancer cells.

Diverse Mechanisms of BRAF Inhibitor Resistance in Melanoma Identified in Clinical and Preclinical Studies

BRAF inhibitor therapy may provide profound initial tumor regression in metastatic melanoma with BRAF V600 mutations, but treatment resistance often leads to disease progression. A multi-center analysis of BRAF inhibitor resistant patient tissue samples detected genomic changes after disease progression including multiple secondary mutations in the MAPK/Erk signaling pathway, mutant BRAF copy number gains, and BRAF alternative splicing as the predominant putative mechanisms of resistance, but 41.7% of samples had no known resistance drivers. In vitro models of BRAF inhibitor resistance have been developed under a wide variety of experimental conditions to investigate unknown drivers of resistance. Several in vitro models developed genetic alterations observed in patient tissue, but others modulate the response to BRAF inhibitors through increased expression of receptor tyrosine kinases. Both secondary genetic alterations and expression changes in receptor tyrosine kinases may increase activation of MAPK/Erk signaling in the presence of BRAF inhibitors as well as activate PI3K/Akt signaling to support continued growth. Melanoma cells that develop resistance in vitro may have increased dependence on serine or glutamine metabolism and have increased cell motility and metastatic capacity. Future studies of BRAF inhibitor resistance in vitro would benefit from adhering to experimental parameters that reflect development of BRAF inhibitor resistance in patients through using multiple cell lines, fully characterizing the dosing strategy, and reporting the fold change in drug sensitivity.