Hedgehog signaling inhibitors in solid and hematological cancers

Stemness regulation in prostate cancer: prostate cancer stem cells and targeted therapy

BACKGROUND

Increasing evidence indicates that cancer stem cells (CSCs) and cancer stem-like cells form a special subpopulation of cells that are ubiquitous in tumors. These cells exhibit similar characteristics to those of normal stem cells in tissues; moreover, they are capable of self-renewal and differentiation, as well as high tumorigenicity and drug resistance. In prostate cancer (PCa), it is difficult to kill these cells using androgen signaling inhibitors and chemotherapy drugs. Consequently, the residual prostate cancer stem cells (PCSCs) mediate tumor recurrence and progression.

OBJECTIVE

This review aims to provide a comprehensive and up-to-date overview of PCSCs, with a particular emphasis on potential therapeutic strategies targeting these cells.

METHODS

After searching in PubMed and Embase databases using 'prostate cancer' and 'cancer stem cells' as keywords, studies related were compiled and examined.

RESULTS

In this review, we detail the origin and characteristics of PCSCs, introduce the regulatory pathways closely related to CSC survival and stemness maintenance, and discuss the link between epithelial-mesenchymal transition, tumor microenvironment and tumor stemness. Furthermore, we introduce the currently available therapeutic strategies targeting CSCs, including signaling pathway inhibitors, anti-apoptotic protein inhibitors, microRNAs, nanomedicine, and immunotherapy. Lastly, we summarize the limitations of current CSC research and mention future research directions.

CONCLUSION

A deeper understanding of the regulatory network and molecular markers of PCSCs could facilitate the development of novel therapeutic strategies targeting these cells. Previous preclinical studies have demonstrated the potential of this treatment approach. In the future, this may offer alternative treatment options for PCa patients.

Cancer Stem Cell Regulation as a Target of Therapeutic Intervention: Insights into Breast, Cervical and Lung Cancer

Cancer Stem Cells (CSCs) play an important role in the development, resistance, and recurrence of many malignancies. These subpopulations of tumor cells have the potential to self-renew, differentiate, and resist conventional therapy, highlighting their importance in cancer etiology. This review explores the regulatory mechanisms of CSCs in breast, cervical, and lung cancers, highlighting their plasticity, self-renewal, and differentiation capabilities. CD44+/CD24- cells are a known marker for breast CSCs. Markers like as CD133 and ALDH have been discovered in cervical cancer CSCs. Similarly, in lung cancer, CSCs identified by CD44, CD133, and ALDH are linked to aggressive tumor behavior and poor therapy results. The commonalities between these tumors highlight the general necessity of targeting CSCs in treatment efforts. However, the intricacies of CSC activity, such as their interaction with the tumor microenvironment and particular signaling pathways differ between cancer types, demanding specialized methods. Wnt/β-catenin, Notch, and Hedgehog pathways are one of the essential signaling pathways, targeting them, may show ameliorative effects on breast, lung and cervical carcinomas and their respective CSCs. Pre-clinical data suggests targeting specific signaling pathways can eliminate CSCs, but ongoing clinical trials are on utilizing signaling pathway inhibitors in patients. In recent studies it has been reported that CAR T based targeting of specific markers may be used as combination therapy. Ongoing research related to nanobiotechnology can also play a significant role in diagnosis and treatment purpose targeting CSCs, as nanomaterials can be used for precise targeting and identification of CSCs. Further research into the targeting of signaling pathways and its precursors could prove to be right step into directing therapies towards CSCs for cancer therapy.

Conserved C143 forms a branched intermediate in Hedgehog autoprocessing: A cancer drug discovery target against Hedgehog signaling

Hedgehog (Hh) signaling plays fundamental roles in embryonic development while its abnormal activation in adults is associated with cancer. Hh targeting drugs have gained FDA approval but resistance emerged quickly, underlining the need for novel types of Hh inhibitors. Hh signaling is initiated by the Hh ligand, generated from the autoprocessing of Hh precursor. However, the catalytic role of a highly conserved Hedgehog residue C143 is still poorly understood. Here, we confirmed that C143 is required for Hh autoprocessing in mammalian cells. NMR titration showed that C143 has an extremely low pKa of 4.5, befitting a highly reactive catalytic residue. We further established that Hh autoprocessing involves a branched intermediate (BI) with two N-termini, formed as a thioester on the C143 sidechain. BI migrates slower than the linear Hh precursor on SDS-PAGE and disappears with DTT treatment. With trypsin digestion and LC-MS/MS, we detected the N-terminal fragment from BI, which is absent from the linear Hh precursor. Therefore, C143 mediates the formation of a BI thioester in Hh autoprocessing, with a catalytic role equivalent to C + 1 in intein splicing. These findings bring us closer to a full mechanistic understanding of Hh autoprocessing while unifying the first two catalytic steps of Hh autoprocessing with intein splicing, its likely evolutionary predecessor. C143 can also serve as a target for covalent drugs for inhibiting Hh signaling in cancer.

Potential Benefits of Adding Alendronate, Celecoxib, Itraconazole, Ramelteon, and Simvastatin to Endometrial Cancer Treatment: The EC5 Regimen

Metastatic endometrial cancer continues to be a common cause of death as of 2024, even after maximal use of all currently available standard treatments. To address this problem of metastatic cancer generally in 2025, the drug repurposing movement within oncology identifies medicines in common general medical use that have clinical or preclinical experimental data indicating that they interfere with or inhibit a specific growth driving element identified in a given cancer. The drug repurposing movement within oncology also uses data from large scale in vitro screens of thousands of drugs, looking for simple empirical growth inhibition in a given cancer type. This paper outlines the data showing that five drugs from general medical practice meet these evidence criteria for inhibition of endometrial cancer growth, the EC5 regimen. The EC5 regimen uses the osteoporosis treatment drug, alendronate; the analgesic drug, celecoxib; the antifungal drug, itraconazole; the sleep aid, ramelteon; and the cholesterol lowering drug, simvastatin. Side effects seen with these drugs are usually minimal and easily tolerated by patients.

Regulation of the Cilia as a Potential Treatment for Senescence and Tumors: A Review

Millions of people worldwide die from malignant tumors every year, and the current clinical treatment is still based on radiotherapy and chemotherapy. Immunotherapy-adjuvant chemotherapy is widely applied, yet resistance to various factors persists in the management of advanced malignancies. Recently researchers have gradually discovered that the integrity of primary cilia is closely related to many diseases. The phenotypic changes in primary cilia are found in some cases of progeria, tumorigenesis, and drug resistance. Primary cilia seem to mediate signaling during these diseases. Hedgehog inhibitors have emerged in recent years to treat tumors by controlling signaling proteins on primary cilia. There is evidence for the use of anti-tumor drugs to treat senescence-related disease. Considering the close relationship between aging and obesity, as well as the obesity is the phenotype of many ciliopathies. Therefore, we speculate that some anti-tumor or anti-aging drugs can treat ciliopathies. Additionally, there is evidence suggesting that anti-aging drugs for tumor treatment, in which the process may be mediated by cilia. This review elucidates for the first time that cilia may be involved in the regulation of senescence, metabolic, tumorigenesis, and tumor resistance and hypothesizes that cilia can be regulated to treat these diseases in the future.

Imperatorin Suppresses Aberrant Hedgehog Pathway and Overcomes Smoothened Antagonist Resistance via STAT3 Inhibition

Background

Hyperactive Hedgehog (Hh) signaling initiates and drives the progression of various tumors. Despite the clinical success of Hh inhibitors targeting Smoothened (SMO), drug resistance, often stemming from SMO mutations, remains a formidable obstacle in cancer therapy. Here, we investigated the potential of imperatorin (IMP), a Chinese herbal medicine, to overcome drug resistance and revealed the potential mechanisms.

Methods

The effect of IMP on Hh signaling pathway was evaluated via Quantitative reverse transcription-polymerase chain reaction, Dual-luciferase reporter assay and Western blot. Meanwhile, we tested its ani-proliferative potential on Hh-driven tumor cells. Loss/gain-of-function, network pharmacology analysis, RNA-sequence analysis and molecular docking were performed to investigate the potential mechanisms of IMP-mediated functions. Furthermore, we established a subcutaneous Hh-driven medulloblastoma xenograft model using the DAOY cell line and examined the in vivo therapeutic efficacy of IMP.

Results

We identified IMP as a novel Hh inhibitor capable of overcoming drug-resistance caused by SMO mutants by inhibiting downstream transcription factor GLI1. IMP suppressed the proliferation of Hh-dependent cancer cells along with Hh activity inhibition. Mechanistically, IMP attenuated the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and its interaction with GLI1 promoter, consequently blocking GLI1 transcription and the target gene expressions. Molecular docking analysis revealed the favorable binding affinity between IMP and STAT3. Importantly, IMP application effectively inhibited the growth of medulloblastoma in vivo, accompanied by the downregulation of GLI1 and phosphorylated STAT3.

Conclusion

Our findings revealed IMP as an innovative approach to combat the drug resistance of SMO inhibitors in Hh-driven tumors, highlighting the crucial role of STAT3 as a transcriptional regulator in Hh signaling.

Stromal androgen signaling governs essential niches in supporting prostate development and tumorigenesis

Androgens and androgen receptor (AR) mediated signaling pathways are essential for prostate development, morphogenesis, growth, and regeneration. Early tissue recombination experiments showed that AR-deficient urogenital sinus mesenchyme combined with intact urogenital sinus epithelium failed to develop into a prostate, demonstrating a stem cell niche for mesenchymal AR in prostatic development. Androgen signaling remains critical for prostate maturation and growth during postnatal stages. Importantly, most primary prostate cancer (PCa) cells express the AR, and aberrant activation of AR directly promotes PCa development, growth, and progression. Therefore, androgen deprivation therapy (ADT) targeting the AR in PCa cells is the main treatment for advanced PCa. However, it eventually fails, leading to the development of castration-resistant PCa, an incurable disease. Given these clinical challenges, the oncogenic AR action needs to be reevaluated for developing new and effective therapies. Recently, an essential niche role of stromal AR was identified in regulating prostate development and tumorigenesis. Here, we summarize the latest discoveries of stromal AR niches and their interactions with prostatic epithelia. In combination with emerging clinical and experimental evidence, we specifically discuss several important and long-term unanswered questions regarding tumor niche roles of stromal AR and highlight future therapeutic strategies by co-targeting epithelial and stromal AR for treating advanced PCa.

Intervention of epithelial mesenchymal transition against colon cancer cell growth and metastasis based on SOX21/POU4F2/Hedgehog signaling axis

AIMS

Colon cancer poses a major threat to human health and a heavy burden on the national economy. As a member of the SOX transcription factor family, SRY-box transcription factor 21 (SOX21) is associated with various cancers, but its mechanism of action in colon cancer remains unclear. This study focused on the molecular mechanisms of transcription factor SOX21 in proliferation and metastasis of colon cancer cells.

MAIN METHODS

We analyzed SOX21 expression level and its impact on survival in colon cancer patients by bioinformatics analysis. We used public databases for gene correlation, GSEA enrichment analysis. Cell function experiments (colony formation assay, wound healing assay, Transwell migration and invasion assay) were utilized to determine the impact of SOX21 silencing and over-expression on cell proliferation and metastasis. The luciferase reporter assay, CUT&RUN-qPCR assay and Methylation Specific PCR were used to explore SOX21-POU class 4 homeobox 2 (POU4F2) molecular interactions. The molecular mechanisms were verified by Quantitative real-time PCR and Western blot analysis.

KEY FINDINGS

SOX21 is highly expressed and affects the overall survival of colon cancer patients. SOX21 can attenuates POU4F2 methylation state by binding with it. In addition, this interaction facilitate its transcriptional activation of Hedgehog pathway, mediates epithelial-mesenchymal transition (EMT), consequently promoting the proliferation and metastasis of colon cancer cells.

SIGNIFICANCE

Our study reveals that SOX21 is an oncogenic molecule and suggests its regulatory role in colon carcinogenesis and progression, providing new insights into the treatment of this disease.

Prostate cancer stem cells and their targeted therapies

Prostate cancer (PCa) is the most common malignancy among men worldwide. Through androgen receptor signaling inhibitor (ARSI) treatment, patients eventually succumb to castration-resistant prostate cancer (CRPC). For this, the prostate cancer stem cells (PCSCs), as a minor population of tumor cells that can promote tumor relapse, ARSI resistance, and disease progression, are gaining attention. Therefore, specific therapy targeting PCSCs has momentum. This study reviewed the identification and characterization of PCSCs and PCSC-based putative biomarkers and summarized their mechanisms of action. We further discussed clinical trials of novel therapeutic interventions focused on PCSC-related pathways, the PCSC microenvironment, cutting-edge miRNA therapy, and immunotherapy approaches from a mechanistic standpoint. This review provides updated insights into PCSC plasticity, identifying new PCSC biomarkers and optimized treatments for patients with advanced PCa.

Hedgehog ligand and receptor cooperatively regulate EGFR stability and activity in non-small cell lung cancer

PURPOSE

The hyperactivation of epidermal growth factor receptor (EGFR) plays a crucial role in non-small cell lung cancer (NSCLC). Hedgehog (Hh) signaling has been implicated in the tumorigenesis and progression of various cancers, however, its function in NSCLC cells remains controversial. Herein, we present a novel finding that challenges the current understanding of Hh signaling in tumor growth.

METHODS

Expression of Hh ligands and receptor were assessed using TCGA datasets, immunoblotting and immunohistochemical. Biological function of Hh ligands and receptor in NSCLC were tested using colony formation, cell count kit-8 (CCK-8) and xenograft assays. Biochemical effect of Hh ligands and receptor on regulating EGFR stability and activity were checked via immunoblotting.

RESULTS

Expression of Hh ligands and receptor was suppressed in NSCLC tissues, and the lower expression levels of these genes were associated with poor prognosis. Ptch1 binds to EGFR and facilitates its poly-ubiquitylation and degradation independent of downstream transcriptional signaling. Moreover, Hh ligands cooperate with Ptch1 to regulate the protein stability and activity of EGFR. This unique mechanism leads to a suppressive effect on NSCLC tumor growth.

CONCLUSION

Non-canonical Hh signaling pathway, involving cooperation between Hh ligands and their receptor Ptch1, facilitates the degradation of EGFR and attenuates its activity in NSCLC. These findings provide novel insights into the regulation of EGFR protein stability and activity, offer new diagnostic indicators for molecular typing of NSCLC and identify potential targets for targeted therapy of this challenging disease.

Targeting Notch signaling pathways with natural bioactive compounds: a promising approach against cancer

Notch signaling pathway is activated abnormally in solid and hematological tumors, which perform essential functions in cell differentiation, survival, proliferation, and angiogenesis. The activation of Notch signaling and communication among Notch and other oncogenic pathways heighten malignancy aggressiveness. Thus, targeting Notch signaling offers opportunities for improved survival and reduced disease incidence. Already, most attention has been given to its role in the cancer cells. Recent research shows that natural bioactive compounds can change signaling molecules that are linked to or interact with the Notch pathways. This suggests that there may be a link between Notch activation and the growth of tumors. Here, we sum up the natural bioactive compounds that possess inhibitory effects on human cancers by impeding the Notch pathway and preventing Notch crosstalk with other oncogenic pathways, which provoke further study of these natural products to derive rational therapeutic regimens for the treatment of cancer and develop novel anticancer drugs. This review revealed Notch as a highly challenging but promising target in oncology.

Post-Transplant Maintenance Therapy in Acute Myeloid Leukemia

Allogeneic hematopoietic cell transplantation (allo-HCT) is potentially curative for patients with acute myeloid leukemia (AML). However, the post-transplant relapse rate ranges from 40 to 70%, particularly with reduced intensity conditioning, and remains a major cause of treatment failure for these patients due to the limited efficacy of salvage therapy options. Strategies to mitigate this risk are urgently needed. In the past few years, the basic framework of post-transplant maintenance has been shaped by several clinical trials investigating targeted therapy, chemotherapy, and immunomodulatory therapies. Although the practice of post-transplant maintenance in AML has become more common, there remain challenges regarding the feasibility and efficacy of this strategy. Here, we review major developments in post-transplant maintenance in AML, along with ongoing and future planned studies in this area, outlining the limitations of available data and our future goals.

Emerging therapeutic frontiers in cancer: insights into posttranslational modifications of PD-1/PD-L1 and regulatory pathways

The interaction between programmed cell death ligand 1 (PD-L1), which is expressed on the surface of tumor cells, and programmed cell death 1 (PD-1), which is expressed on T cells, impedes the effective activation of tumor antigen-specific T cells, resulting in the evasion of tumor cells from immune-mediated killing. Blocking the PD-1/PD-L1 signaling pathway has been shown to be effective in preventing tumor immune evasion. PD-1/PD-L1 blocking antibodies have garnered significant attention in recent years within the field of tumor treatments, given the aforementioned mechanism. Furthermore, clinical research has substantiated the efficacy and safety of this immunotherapy across various tumors, offering renewed optimism for patients. However, challenges persist in anti-PD-1/PD-L1 therapies, marked by limited indications and the emergence of drug resistance. Consequently, identifying additional regulatory pathways and molecules associated with PD-1/PD-L1 and implementing judicious combined treatments are imperative for addressing the intricacies of tumor immune mechanisms. This review briefly outlines the structure of the PD-1/PD-L1 molecule, emphasizing the posttranslational modification regulatory mechanisms and related targets. Additionally, a comprehensive overview on the clinical research landscape concerning PD-1/PD-L1 post-translational modifications combined with PD-1/PD-L1 blocking antibodies to enhance outcomes for a broader spectrum of patients is presented based on foundational research.

Glasdegib with intensive/nonintensive chemotherapy in Japanese patients with untreated acute myeloid leukemia or high-risk myelodysplastic syndromes

Glasdegib is a potent, selective, oral inhibitor of the hedgehog signaling pathway. In this phase I study, previously untreated Japanese patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndromes were treated with glasdegib (100 mg once daily) combinations: low-dose cytarabine (20 mg twice daily; cohort 1, n = 6; expansion cohort, n = 15); daunorubicin and cytarabine (60 mg/m2 i.v.; cohort 2, n = 6); or azacitidine (100 mg/m2 i.v.; cohort 3, n = 6). Patients, except cohort 2, were ineligible for intensive chemotherapy. The primary end-point was dose-limiting toxicity in cohorts 1-3 and disease-modifying response in the expansion cohort. Disease-modifying response rate was tested with the null hypothesis of 6.8%, which was set based on the results from the phase II BRIGHT AML 1003 study (NCT01546038). No dose-limiting toxicities were observed in cohorts 1 or 3; one patient in cohort 2 experienced a dose-limiting toxicity of grade 3 erythroderma. The most common grade ≥3 treatment-related adverse events were neutropenia and thrombocytopenia (66.7% each) in cohort 1 and thrombocytopenia (60.0%) in the expansion cohort. In the expansion cohort, the disease-modifying response rate was 46.7% (90% confidence interval, 24.4-70.0; p < 0.0001), with all patients achieving either a complete response or complete response with incomplete blood count recovery. Median overall survival was 13.9 months. In this study, the primary disease-modifying response end-point with glasdegib plus low-dose cytarabine was met. The study confirms the safety and efficacy of glasdegib plus low-dose cytarabine in Japanese patients with AML ineligible for intensive chemotherapy.

Clinical and Preclinical Targeting of Oncogenic Pathways in PDAC: Targeted Therapeutic Approaches for the Deadliest Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer-related death worldwide. It is commonly diagnosed in advanced stages and therapeutic interventions are typically constrained to systemic chemotherapy, which yields only modest clinical outcomes. In this review, we examine recent developments in targeted therapy tailored to address distinct molecular pathway alteration required for PDAC. Our review delineates the principal signaling pathways and molecular mechanisms implicated in the initiation and progression of PDAC. Subsequently, we provide an overview of prevailing guidelines, ongoing investigations, and prospective research trajectories related to targeted therapeutic interventions, drawing insights from randomized clinical trials and other pertinent studies. This review focus on a comprehensive examination of preclinical and clinical data substantiating the efficacy of these therapeutic modalities, emphasizing the potential of combinatorial regimens and novel therapies to enhance the quality of life for individuals afflicted with PDAC. Lastly, the review delves into the contemporary application and ongoing research endeavors concerning targeted therapy for PDAC. This synthesis serves to bridge the molecular elucidation of PDAC with its clinical implications, the evolution of innovative therapeutic strategies, and the changing landscape of treatment approaches.

Rebuilding the microenvironment of primary tumors in humans: a focus on stroma

Conventional tumor models have critical shortcomings in that they lack the complexity of the human stroma. The heterogeneous stroma is a central compartment of the tumor microenvironment (TME) that must be addressed in cancer research and precision medicine. To fully model the human tumor stroma, the deconstruction and reconstruction of tumor tissues have been suggested as new approaches for in vitro tumor modeling. In this review, we summarize the heterogeneity of tumor-associated stromal cells and general deconstruction approaches used to isolate patient-specific stromal cells from tumor tissue; we also address the effect of the deconstruction procedure on the characteristics of primary cells. Finally, perspectives on the future of reconstructed tumor models are discussed, with an emphasis on the essential prerequisites for developing authentic humanized tumor models.

Small cells - big issues: biological implications and preclinical advancements in small cell lung cancer

Current treatment guidelines refer to small cell lung cancer (SCLC), one of the deadliest human malignancies, as a homogeneous disease. Accordingly, SCLC therapy comprises chemoradiation with or without immunotherapy. Meanwhile, recent studies have made significant advances in subclassifying SCLC based on the elevated expression of the transcription factors ASCL1, NEUROD1, and POU2F3, as well as on certain inflammatory characteristics. The role of the transcription regulator YAP1 in defining a unique SCLC subset remains to be established. Although preclinical analyses have described numerous subtype-specific characteristics and vulnerabilities, the so far non-existing clinical subtype distinction may be a contributor to negative clinical trial outcomes. This comprehensive review aims to provide a framework for the development of novel personalized therapeutic approaches by compiling the most recent discoveries achieved by preclinical SCLC research. We highlight the challenges faced due to limited access to patient material as well as the advances accomplished by implementing state-of-the-art models and methodologies.

Zinc finger proteins and ATP-binding cassette transporter-dependent multidrug resistance

BACKGROUND

Multidrug resistance (MDR) remains a significant challenge in cancer treatment, leading to poor clinical outcomes. Dysregulation of ATP-binding cassette (ABC) transporters has been identified as a key contributor to MDR. Zinc finger proteins (ZNPs) are key regulators of transcription and have emerged as potential contributors to cancer drug resistance. Bridging the knowledge gap between ZNPs and MDR is essential to understand a source of heterogeneity in cancer treatment. This review sought to elucidate how different ZNPs modulate the transcriptional regulation of ABC genes, contributing to resistance to cancer therapies.

METHODS

The search was conducted using PubMed, Google Scholar, EMBASE and Web of Science.

RESULTS

In addition to ABC-blockers, the transcriptional features regulated by ZNP are expected to play a role in reversing ABC-mediated MDR and predicting the efficacy of anticancer treatments. Among the ZNP-induced epithelial to mesenchymal transition, SNAIL, SLUG and Zebs have been identified as important factors in promoting MDR through activation of ATM, NFκB and PI3K/Akt pathways, exposing the metabolism to potential ZNP-MDR interactions. Additionally, nuclear receptors, such as VDR, ER and PXR have been found to modulate certain ABC regulations. Other C2H2-type zinc fingers, including Kruppel-like factors, Gli and Sp also have the potential to contribute to MDR.

CONCLUSION

Besides reviewing evidence on the effects of ZNP dysregulation on ABC-related chemoresistance in malignancies, significant markers of ZNP functions are discussed to highlight the clinical implications of gene-to-gene and microenvironment-to-gene interactions on MDR prospects. Future research on ZNP-derived biomarkers is crucial for addressing heterogeneity in cancer therapy.

Assessing the genetic risk of nodular melanoma using a candidate gene approach

BACKGROUND

Nodular melanoma (NM) is a challenge to diagnose early due to its rapid growth and more atypical clinical presentation, making it the largest contributor to melanoma mortality.

OBJECTIVES

Our study aim was to perform a rare-variant allele (RVA) analysis of whole-exome sequencing of patients with NM and non-NM (minor allele frequency ≤ 1% non-Finnish European) for a set of 500 candidate genes potentially implicated in melanoma.

METHODS

This study recruited 131 participants with NM and 194 with non-NM from South-east Queensland and patients with NM from Victoria to perform a comparative analysis of possible genetic differences or similarities between the two melanoma cohorts.

RESULTS

Phenotypic analysis revealed that a majority of patients diagnosed with NM were older males with a higher frequency of fair skin and red hair than is seen in the general population. The distribution of common melanoma polygenic risk scores was similar in patients with NM and non-NM, with over 28% in the highest quantile of scores. There was also a similar frequency of carriage of familial/high-penetrant melanoma gene and loss-of-function variants. We identified 39 genes by filtering 500 candidate genes based on the greatest frequency in NM compared with non-NM cases. The genes with RVAs of greatest frequency in NM included PTCH1, ARID2 and GHR. Rare variants in the SMO gene, which interacts with PTCH1 as ligand and receptor, were also identified, providing evidence that the Hedgehog pathway may contribute to NM risk. There was a cumulative effect in carrying multiple rare variants in the NM-associated genes. A 14.8-fold increased ratio for NM compared with non-NM was seen when two RVAs of the 39 genes were carried by a patient.

CONCLUSIONS

This study highlights the importance of considering frequency of RVA to identify those at risk of NM in addition to known high penetrance genes.

Targeting breast cancer stem cells through retinoids: A new hope for treatment

Breast cancer is a complex and diverse disease accounting for nearly 30% of all cancers diagnosed in females. But unfortunately, patients develop resistance to the existing chemotherapeutic regimen, resulting in approximately 90% treatment failure. With over half a million deaths annually, it is imperative to explore new therapeutic approaches to combat the disease. Within a breast tumor, a small sub-population of heterogeneous cells, with a unique ability of self-renew and differentiation and responsible for tumor formation, initiation, and recurrence are referred to as breast cancer stem cells (BCSCs). These BCSCs have been identified as one of the main contributors to chemoresistance in breast cancer, making them an attractive target for developing novel therapeutic strategies. These cells exhibit surface biomarkers such as CD44+, CD24-/LOW, ALDH, CD133, and CD49f phenotypes. Higher expression of CD44+ and ALDH activity has been associated with the formation of tumors in various cancers. Moreover, the abnormal regulation of signaling pathways, including Hedgehog, Notch, β-catenin, JAK/STAT, and P13K/AKT/mTOR, leads to the formation of cancer stem cells, resulting in the development of tumors. The growing drug resistance in BC is a significant challenge, highlighting the need for new therapeutic strategies to combat this dreadful disease. Retinoids, a large group of synthetic derivatives of vitamin A, have been studied as chemopreventive agents in clinical trials and have been shown to regulate various crucial biological functions including vision, development, inflammation, and metabolism. On a cellular level, the retinoid activity has been well characterized and translated and is known to induce differentiation and apoptosis, which play important roles in the outcome of the transformation of tissues into malignant. Retinoids have been investigated extensively for their use in the treatment and prevention of cancer due to their high receptor-binding affinity to directly modulate gene expression programs. Therefore, in this study, we aim to summarize the current understanding of BCSCs, their biomarkers, and the associated signaling pathways. Retinoids, such as Adapalene, a third-generation retinoid, have shown promising anti-cancer potential and may serve as therapeutic agents to target BCSCs.

Ligand-dependent hedgehog signaling maintains an undifferentiated, malignant osteosarcoma phenotype

TP53 and RB1 loss-of-function mutations are common in osteosarcoma. During development, combined loss of TP53 and RB1 function leads to downregulation of autophagy and the aberrant formation of primary cilia, cellular organelles essential for the transmission of canonical Hedgehog (Hh) signaling. Excess cilia formation then leads to hypersensitivity to Hedgehog (Hh) ligand signaling. In mouse and human models, we now show that osteosarcomas with mutations in TP53 and RB1 exhibit enhanced ligand-dependent Hh pathway activation through Smoothened (SMO), a transmembrane signaling molecule required for activation of the canonical Hh pathway. This dependence is mediated by hypersensitivity to Hh ligand and is accompanied by impaired autophagy and increased primary cilia formation and expression of Hh ligand in vivo. Using a conditional genetic mouse model of Trp53 and Rb1 inactivation in osteoblast progenitors, we further show that deletion of Smo converts the highly malignant osteosarcoma phenotype to benign, well differentiated bone tumors. Conversely, conditional overexpression of SHH ligand, or a gain-of-function SMO mutant in committed osteoblast progenitors during development blocks terminal bone differentiation. Finally, we demonstrate that the SMO antagonist sonidegib (LDE225) induces growth arrest and terminal differentiation in vivo in osteosarcomas that express primary cilia and Hh ligand combined with mutations in TP53. These results provide a mechanistic framework for aberrant Hh signaling in osteosarcoma based on defining mutations in the tumor suppressor, TP53.

Hedgehog signalling in allograft vasculopathy: a new therapeutic target?

Allograft vasculopathy (AV) leads to chronic rejection of organ transplants, but its causes are obscure. New research from the Jane-Wit laboratory showed that Sonic Hedgehog (SHH) signalling from damaged graft endothelium drives vasculopathy by promoting proinflammatory cytokine production and NLRP3-inflammasome activation in alloreactive CD4+PTCH1hiPD-1hiT memory cells, offering new diagnostic and therapeutic strategies.

Long-term strategies for management of advanced basal cell carcinoma with hedgehog inhibitors

Basal cell carcinoma (BCC), the most common type of skin cancer, is characterized by aberrant activation of the hedgehog molecular pathway. Systemic therapy is indicated when local approaches, such as surgery and radiation, are inappropriate. In this article, a group of clinical experts recommends the long-term management strategy for advanced BCC patients treated with systemic therapy. The hedgehog inhibitors sonidegib and vismodegib are first-line treatments for advanced BCC with a long-lasting response, but long-term treatment with hedgehog inhibitors is often challenged by tolerability issues. However, several strategies for adverse effect management are available, such as dose interruptions, on-label alternate-day dosing and supportive medications. In conclusion, although BCC shows a high tumor mutational burden that favors a response to immunotherapy, experts recommend keeping patients on hedgehog inhibitors limiting immunotherapy to those who developed resistance during hedgehog inhibitor therapy or in case of persisting toxicity despite long-term management of adverse events.

Cellular and molecular mechanisms of Hedgehog signalling

The Hedgehog signalling pathway has crucial roles in embryonic tissue patterning, postembryonic tissue regeneration, and cancer, yet aspects of Hedgehog signal transmission and reception have until recently remained unclear. Biochemical and structural studies surprisingly reveal a central role for lipids in Hedgehog signalling. The signal - Hedgehog protein - is modified by cholesterol and palmitate during its biogenesis, thereby necessitating specialized proteins such as the transporter Dispatched and several lipid-binding carriers for cellular export and receptor engagement. Additional lipid transactions mediate response to the Hedgehog signal, including sterol activation of the transducer Smoothened. Access of sterols to Smoothened is regulated by the apparent sterol transporter and Hedgehog receptor Patched, whose activity is blocked by Hedgehog binding. Alongside these lipid-centric mechanisms and their relevance to pharmacological pathway modulation, we discuss emerging roles of Hedgehog pathway activity in stem cells or their cellular niches, with translational implications for regeneration and restoration of injured or diseased tissues.

SCUBE2 mediates bone metastasis of luminal breast cancer by modulating immune-suppressive osteoblastic niches

Estrogen receptor (ER)-positive luminal breast cancer is a subtype with generally lower risk of metastasis to most distant organs. However, bone recurrence occurs preferentially in luminal breast cancer. The mechanisms of this subtype-specific organotropism remain elusive. Here we show that an ER-regulated secretory protein SCUBE2 contributes to bone tropism of luminal breast cancer. Single-cell RNA sequencing analysis reveals osteoblastic enrichment by SCUBE2 in early bone-metastatic niches. SCUBE2 facilitates release of tumor membrane-anchored SHH to activate Hedgehog signaling in mesenchymal stem cells, thus promoting osteoblast differentiation. Osteoblasts deposit collagens to suppress NK cells via the inhibitory LAIR1 signaling and promote tumor colonization. SCUBE2 expression and secretion are associated with osteoblast differentiation and bone metastasis in human tumors. Targeting Hedgehog signaling with Sonidegib and targeting SCUBE2 with a neutralizing antibody both effectively suppress bone metastasis in multiple metastasis models. Overall, our findings provide a mechanistic explanation for bone preference in luminal breast cancer metastasis and new approaches for metastasis treatment.

Hedgehog pathway orchestrates the interplay of histone modifications and tailors combination epigenetic therapies in breast cancer

Epigenetic therapies that cause genome-wide epigenetic alterations, could trigger local interplay between different histone marks, leading to a switch of transcriptional outcome and therapeutic responses of epigenetic treatment. However, in human cancers with diverse oncogenic activation, how oncogenic pathways cooperate with epigenetic modifiers to regulate the histone mark interplay is poorly understood. We herein discover that the hedgehog (Hh) pathway reprograms the histone methylation landscape in breast cancer, especially in triple-negative breast cancer (TNBC). This facilitates the histone acetylation caused by histone deacetylase (HDAC) inhibitors and gives rise to new therapeutic vulnerability of combination therapies. Specifically, overexpression of zinc finger protein of the cerebellum 1 (ZIC1) in breast cancer promotes Hh activation, facilitating the switch of H3K27 methylation (H3K27me) to acetylation (H3K27ac). The mutually exclusive relationship of H3K27me and H3K27ac allows their functional interplay at oncogenic gene locus and switches therapeutic outcomes. Using multiple in vivo breast cancer models including patient-derived TNBC xenograft, we show that Hh signaling-orchestrated H3K27me and H3K27ac interplay tailors combination epigenetic drugs in treating breast cancer. Together, this study reveals the new role of Hh signaling-regulated histone modifications interplay in responding to HDAC inhibitors and suggests new epigenetically-targeted therapeutic solutions for treating TNBC.

Structure-based discovery of potent USP28 inhibitors derived from Vismodegib

Ubiquitin-specific proteases (USPs) 28 is overexpressed in multiple types of cancers. The development of potent USP28 inhibitors is still in primitive stage. We previously reported our discovery of Vismodegib as a USP28 inhibitor by screening a commercially available drug library. Herein, we report our efforts to solve the cocrystal structure of Vismodegib bound to USP28 for the first time and subsequent structure-based optimization leading to a series of Vismodegib derivatives as potent USP28 inhibitors. Based on the cocrystal structure, elaborative SARs exploration was carried out to afford much more potent USP28 inhibitors than Vismodegib. The representative compounds 9l, 9o and 9p bearing high potency on USP28 showed high selectivity over USP2, USP7, USP8, USP9x, UCHL3 and UCHL5. The detailed cellular assay suggested that compounds 9l, 9o and 9p could cause cytotoxicity in both human colorectal cancer and lung squamous carcinoma cells and significantly enhance the sensitivity of colorectal cancer cells to Regorafenib. Further immunoblotting analysis indicated that compounds 9l, 9o and 9p could dose-dependently down-regulate the cellular level of c-Myc through ubiquitin-proteasome system and anti-cancer effects could mainly be attributed to their inhibition on USP28 but not involving the Hedgehog-Smoothened pathway. Thus, our work provided a series of novel and potent USP28 inhibitors derived from Vismodegib and may contribute to the development of USP28 inhibitors.

Tumor cell plasticity in targeted therapy-induced resistance: mechanisms and new strategies

Despite the success of targeted therapies in cancer treatment, therapy-induced resistance remains a major obstacle to a complete cure. Tumor cells evade treatments and relapse via phenotypic switching driven by intrinsic or induced cell plasticity. Several reversible mechanisms have been proposed to circumvent tumor cell plasticity, including epigenetic modifications, regulation of transcription factors, activation or suppression of key signaling pathways, as well as modification of the tumor environment. Epithelial-to-mesenchymal transition, tumor cell and cancer stem cell formation also serve as roads towards tumor cell plasticity. Corresponding treatment strategies have recently been developed that either target plasticity-related mechanisms or employ combination treatments. In this review, we delineate the formation of tumor cell plasticity and its manipulation of tumor evasion from targeted therapy. We discuss the non-genetic mechanisms of targeted drug-induced tumor cell plasticity in various types of tumors and provide insights into the contribution of tumor cell plasticity to acquired drug resistance. New therapeutic strategies such as inhibition or reversal of tumor cell plasticity are also presented. We also discuss the multitude of clinical trials that are ongoing worldwide with the intention of improving clinical outcomes. These advances provide a direction for developing novel therapeutic strategies and combination therapy regimens that target tumor cell plasticity.

Hedgehog Signaling in Gonadal Development and Function

Three distinct hedgehog (HH) molecules, (sonic, desert, and indian), two HH receptors (PTCH1 and PTCH2), a membrane bound activator (SMO), and downstream three transcription factors (GLI1, GLI2, and GLI3) are the major components of the HH signaling. These signaling molecules were initially identified in Drosophila melanogaster. Later, it has been found that the HH system is highly conserved across species and essential for organogenesis. HH signaling pathways play key roles in the development of the brain, face, skeleton, musculature, lungs, and gastrointestinal tract. While the sonic HH (SHH) pathway plays a major role in the development of the central nervous system, the desert HH (DHH) regulates the development of the gonads, and the indian HH (IHH) acts on the development of bones and joints. There are also overlapping roles among the HH molecules. In addition to the developmental role of HH signaling in embryonic life, the pathways possess vital physiological roles in testes and ovaries during adult life. Disruption of DHH and/or IHH signaling results in ineffective gonadal steroidogenesis and gametogenesis. While DHH regulates the male gonadal functions, ovarian functions are regulated by both DHH and IHH. This review article focuses on the roles of HH signaling in gonadal development and reproductive functions with an emphasis on ovarian functions. We have acknowledged the original research work that initially reported the findings and discussed the subsequent studies that have further analyzed the role of HH signaling in testes and ovaries.

Targeting Features of Curaxin CBL0137 on Hematological Malignancies In Vitro and In Vivo

The anticancer activity of Curaxin CBL0137, a DNA-binding small molecule with chromatin remodulating effect, has been demonstrated in different cancers. Herein, a comparative evaluation of CBL0137 activity was performed in respect to acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia and multiple myeloma (MM) cultured in vitro. MTT assay showed AML and MM higher sensitivity to CBL0137's cytostatic effect comparatively to other hematological malignancy cells. Flow cytometry cell cycle analysis revealed an increase in subG1 and G2/M populations after CBL0137 cell treatment, but the prevalent type of arrest varied. Apoptosis activation by CBL0137 measured by Annexin-V/PI dual staining was more active in AML and MM cells. RT2 PCR array showed that changes caused by CBL0137 in signaling pathways involved in cancer pathogenesis were more intensive in AML and MM cells. On the murine model of AML WEHI-3, CBL0137 showed significant anticancer effects in vivo, which were evaluated by corresponding changes in spleen and liver. Thus, more pronounced anticancer effects of CBL0137 in vitro were observed in respect to AML and MM. Experiments in vivo also indicated the perspective of CBL0137 use for AML treatment. This in accordance with the frontline treatment approach in AML using epigenetic drugs.

Speckle-type POZ protein could play a potential inhibitory role in human renal cell carcinoma

BACKGROUND

Speckle-type POZ protein(SPOP), a substrate adaptor of Cul3 ubiquitin ligase, plays crucial roles in solid neoplasms by promoting the ubiquitination and degradation of substrates. Limited studies have shown that SPOP is overexpressed in human renal cell carcinoma (RCC) tissue. However, the exact role of SPOP in RCC remains unclear and needs to be further elucidated. The present study showed that SPOP was expressed at different levels in different RCC cell lines. The purpose of this study was to explore the roles of SPOP in the biological features of RCC cells and the expression levels of SPOP in human tissue microarray (TMA) and kidney tissues.

METHODS

Here, SPOP was overexpressed by lentiviral vector transfection in ACHN and Caki-1 cells, and SPOP was knocked down in Caki-2 cells with similar transfection methods. The transfection efficiency was evaluated by quantitative PCR and western blotting analyses. The role of SPOP in the proliferation, migration, invasion and apoptosis of cell lines was determined by the MTT, wound-healing, transwell and flow cytometry assays. Moreover, the cells were treated with different drug concentrations in proliferation and apoptosis assays to investigate the effect of sunitinib and IFN-α2b on the proliferation and apoptosis of SPOP-overexpressing cells and SPOP-knockdown RCC cells. Finally, immunohistochemical staining of SPOP was performed in kidney tissues and TMAs, which included RCC tissues and corresponding adjacent normal tissues.

RESULTS

Overexpression of SPOP inhibited cell proliferation, migration and invasion and increased cell apoptosis. Interestingly, sunitinib and IFN-α2b at several concentrations increased the proliferation inhibitory rate and total apoptosis rate of cells overexpressing SPOP. The findings of the present study showed that the SPOP protein was significantly expressed at low levels in most clear cell RCC (ccRCC) tissues and at relatively high levels in the majority of adjacent normal tissues and kidney tissues. Kaplan-Meier survival analysis showed that there was no statistically significant difference in cumulative survival based on the data of different SPOP expression levels in TMA and patients.

CONCLUSIONS

In contrast to previous studies, our findings demonstrated that overexpression of SPOP might suppress the progression of RCC cells, which was supported by cell experiments and immunohistochemical staining. SPOP could be a potential tumour inhibitor in RCC.

Resveratrol inhibits TRAF6/PTCH/SMO signal and regulates prostate cancer progression

Prostate cancer (PC) is one of the most common types of cancers among men, referring to the uncontrolled growth of the prostate gland. It is increasingly recognized that the interaction of the glioma-associated oncogene (GLI) pathway and androgen receptor affects PC progression. Nevertheless, the effects of resveratrol on PC progression via Hedgehog (HH) signaling remain unexplored. In this study, the castration-sensitive and castration-resistant xenograft models in mice are systematically established using two different PC cell lines (LNCaP and PC-3). Further, the Western blotting, immunohistochemistry, MTT, Transwell, and RT-qPCR analyses are performed to verify the mechanistic views of resveratrol on PC and HH signals in vitro and in vivo. Resveratrol showed epithelial-mesenchymal transition (EMT) progression, inhibiting the tumor size and expression levels of vimentin, vascular endothelial growth factor (VEGF), and matrix metalloproteinases (MMP) 7, as well as upregulating the expression profiles the E-cadherin and Annexin 2. Moreover, resveratrol inhibited the hedgehog (HH) signals and tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6) levels exhibiting the therapeutic action on castration-sensitive and castration-resistant PC cell lines. In summary, the overexpression of TRAF6 enhanced the viability and EMT progression of cancer cells. The resveratrol could alleviate the TRAF6 effect and regulate the HH signal to affect PC progression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-022-00544-0.

A Gold Nanoparticle Bioconjugate Delivery System for Active Targeted Photodynamic Therapy of Cancer and Cancer Stem Cells

Cancer stem cells (CSCs), also called tumor-initiating cells, are a subpopulation of cancer cells believed to be the leading cause of cancer initiation, growth, metastasis, and recurrence. Presently there are no effective treatments targeted at eliminating CSCs. Hence, an urgent need to develop measures to target CSCs to eliminate potential recurrence and metastasis associated with CSCs. Cancer stem cells have inherent and unique features that differ from other cancer cells, which they leverage to resist conventional therapies. Targeting such features with photodynamic therapy (PDT) could be a promising treatment for drug-resistant cancer stem cells. Photodynamic therapy is a light-mediated non-invasive treatment modality. However, PDT alone is unable to eliminate cancer stem cells effectively, hence the need for a targeted approach. Gold nanoparticle bioconjugates with PDT could be a potential approach for targeted photodynamic therapy of cancer and CSCs. This approach has the potential for enhanced drug delivery, selective and specific attachment to target tumor cells/CSCs, as well as the ability to efficiently generate ROS. This review examines the impact of a smart gold nanoparticle bioconjugate coupled with a photosensitizer (PS) in promoting targeted PDT of cancer and CSC.

Proton pump inhibitors and sensitization of cancer cells to radiation therapy

This review article outlines six molecular pathways that confer resistance of cancer cells to ionizing radiation, and describes how proton pump inhibitors (PPIs) may be used to overcome radioresistance induced by alteration of one or more of these signaling pathways. The inflammatory, adaptive, hypoxia, DNA damage repair, cell adhesion, and developmental pathways have all been linked to the resistance of cancer cells to ionizing radiation. Here we describe the molecular link between alteration of these pathways in cancer cells and development of resistance to ionizing radiation, and discuss emerging data on the use of PPIs to favorably modify one or more components of these pathways to sensitize cancer cells to ionizing radiation. Understanding the relationship between altered signaling pathways, radioresistance, and biological activity of PPIs may serve as a basis to repurpose PPIs to restore key biological processes that are involved in cancer progression and to sensitize cancer cells to radiation therapy.

HDAC6 inhibition decreases leukemic stem cell expansion driven by Hedgehog hyperactivation by restoring primary ciliogenesis

Aberrant activation of the Hh pathway promotes cell proliferation and multi-drug resistance (MDR) in several cancers, including Acute Myeloid Leukemia (AML). Notably, only one Hh inhibitor, glasdegib, has been approved for AML treatment, and most patients eventually relapse, highlighing the urgent need ti discover new therapeutic targets. Hh signal is transduced through the membrane of the primary cilium, a structure expressed by non-proliferating mammalian cells, whose stabilization depends on the activity of HDAC6. Here we describe a positive correlation between Hh, HDAC6, and MDR genes in a cohort of adult AML patients, human leukemic cell lines, and a zebrafish model of Hh overexpression. The hyper-activation of Hh or HDAC6 in zebrafish drove the increased proliferation of hematopoietic stem and progenitor cells (HSPCs). Interestingly, this phenotype was rescued by inhibition of HDAC6 but not of Hh. Also, in human leukemic cell lines, a reduction in vitality was obtained through HDAC6, but not Hh inhibition. Our data showed the presence of a cross-talk between Hh and HDAC6 mediated by stabilization of the primary cilium, which we detect for the first time in zebrafish HSPCs. Inhibition of HDAC6 activity alone or in combination therapy with the chemotherapeutic agent cytarabine, efficiently rescued the hematopoietic phenotype. Our results open the possibility to introduce HDAC6 as therapeutic target to reduce proliferation of leukemic blasts in AML patients.

Actionable Tumor Alterations and Treatment Protocol Enrollment of Pediatric and Young Adult Patients With Refractory Cancers in the National Cancer Institute-Children's Oncology Group Pediatric MATCH Trial

PURPOSE

The National Cancer Institute-Children's Oncology Group Pediatric MATCH trial aimed to facilitate evaluation of molecular-targeted therapies in biomarker-selected cohorts of childhood and young adult patients with cancer by screening tumors for actionable alterations.

PATIENTS AND METHODS

Tumors from patients age 1-21 years with refractory solid tumors, lymphomas, or histiocytic disorders were subjected to cancer gene panel sequencing and limited immunohistochemistry to identify actionable alterations for assignment to phase II treatment arms. The rates of treatment arm assignment and enrollment were compared between clinical and demographic groups.

RESULTS

Testing was completed for 94.7% of tumors submitted. Actionable alterations were detected in 31.5% of the first 1,000 tumors screened, with treatment arm assignment and enrollment occurring in 28.4% and 13.1% of patients, respectively. Assignment rates varied by tumor histology and were higher for patients with CNS tumors or enrolled at Pediatric Early Phase Clinical Trials Network sites. A reported history of prior clinical molecular testing was associated with higher assignment and enrollment rates. Actionable alterations in the mitogen-activated protein kinase signaling pathway were most frequent (11.2%). The most common reasons provided for not enrolling on treatment arms were patients receiving other treatment or poor clinical status.

CONCLUSION

The Pediatric MATCH trial has proven the feasibility of a nationwide screening Protocol for identification of actionable genetic alterations and assignment of pediatric and young adult patients with refractory cancers to trials of molecularly targeted therapies. These data support the early use of tumor molecular screening for childhood patients with cancer whose tumors have not responded to standard treatments.

Mechanism of Targeting the Hedgehog Signaling Pathway against Chemotherapeutic Resistance in Multiple Myeloma

Objective

The aim of this study was to explore the relationship between the Hedgehog signaling pathway and drug resistance in multiple myeloma.

Methods

The human myeloma cell line RPMI 8266 was taken as the research object. An azithromycin (AZM)-resistant cell line RPMI 8226/R was constructed, and GENT61 was used to block the Hedgehog signaling pathway. Cells were rolled into RPMI 8226/S (S group), RPMI 8226/R (R group), GENT61+RPMI 8226/S (GENT61+S group), and GENT61+RPMI 8226/R (GENT61+R group). The proliferation of cells in each group was assessed, and the expression of patched homolog 1 (PTCH1), zinc finger-containing transcription factors 1 (GLI1), GLI2, hair-division associated enhancer 1 (Hes1), and sonic hedgehog factor (SHH) in each group was detected. Interleukin (IL)-6 and vascular endothelial growth factor (VEGF) were measured.

Results

Compared with the S group, the expression levels of PTCH1, GLI2, Hes1, and SHH and the contents of IL-6 and VEGF in the R group were greatly increased, while the expression level of GLI1 was notably decreased (P < 0.05). Compared with the R group, the GENT61+R group greatly increased cell proliferation inhibition. However, the expression levels of PTCH1, GLI2, Hes1, and SHH, and the contents of IL-6 and VEGF were notably decreased, while GLI1 expression levels were greatly increased (P < 0.05).

Conclusion

AZM-resistant multiple myeloma was closely associated with the Hedgehog signaling pathway activation, and blocking the Hedgehog signaling pathway can be used as a therapeutic target to improve drug resistance in multiple myeloma.

Hedgehog Autoprocessing: From Structural Mechanisms to Drug Discovery

Hedgehog (Hh) signaling plays pivotal roles in embryonic development. In adults, Hh signaling is mostly turned off but its abnormal activation is involved in many types of cancer. Hh signaling is initiated by the Hh ligand, generated from the Hh precursor by a specialized autocatalytic process called Hh autoprocessing. The Hh precursor consists of an N-terminal signaling domain (HhN) and a C-terminal autoprocessing domain (HhC). During Hh autoprocessing, the precursor is cleaved between N- and C-terminal domain followed by the covalent ligation of cholesterol to the last residue of HhN, which subsequently leads to the generation of Hh ligand for Hh signaling. Hh autoprocessing is at the origin of canonical Hh signaling and precedes all downstream signaling events. Mutations in the catalytic residues in HhC can lead to congenital defects such as holoprosencephaly (HPE). The aim of this review is to provide an in-depth summary of the progresses and challenges towards an atomic level understanding of the structural mechanisms of Hh autoprocessing. We also discuss drug discovery efforts to inhibit Hh autoprocessing as a new direction in cancer therapy.

Cholesterol and Hedgehog Signaling: Mutual Regulation and Beyond

The Hedgehog (HH) signaling is one of the key agents that govern the precisely regulated developmental processes of multicellular organisms in vertebrates and invertebrates. The HH pathway in the receiving cell includes Patched1, a twelve-pass transmembrane receptor, and Smoothened, a seven-transmembrane G-protein coupled receptor (GPCR), and the downstream GLI family of three transcriptional factors (GLI1-GLI3). Mutations of HH gene and the main components in HH signaling are also associated with numerous types of diseases. Before secretion, the HH protein undergoes post-translational cholesterol modification to gain full activity, and cholesterol is believed to be essential for proper HH signaling transduction. In addition, results from recent studies show the reciprocal effect that HH signaling functions in cholesterol metabolism as well as in cholesterol homeostasis, which provides feedback to HH pathway. Here, we hope to provide new insights into HH signaling function by discussing the role of cholesterol in HH protein maturation, secretion and HH signaling transduction, and the potential role of HH in regulation of cholesterol as well.

Blocking chondrocyte hypertrophy in conditional Evc knockout mice does not modify cartilage damage in osteoarthritis

Chondrocytes in osteoarthritic (OA) cartilage acquire a hypertrophic-like phenotype, where Hedgehog (Hh) signaling is pivotal. Hh overexpression causes OA-like cartilage lesions, whereas its downregulation prevents articular destruction in mouse models. Mutations in EVC and EVC2 genes disrupt Hh signaling, and are responsible for the Ellis-van Creveld syndrome skeletal dysplasia. Since Ellis-van Creveld syndrome protein (Evc) deletion is expected to hamper Hh target gene expression we hypothesized that it would also prevent OA progression avoiding chondrocyte hypertrophy. Our aim was to study Evc as a new therapeutic target in OA, and whether Evc deletion restrains chondrocyte hypertrophy and prevents joint damage in an Evc tamoxifen induced knockout (Evc^cKO ) model of OA. For this purpose, OA was induced by surgical knee destabilization in wild-type (WT) and Evc^cKO adult mice, and healthy WT mice were used as controls (n = 10 knees/group). Hypertrophic markers and Hh genes were measured by qRT-PCR, and metalloproteinases (MMP) levels assessed by western blot. Human OA chondrocytes and cartilage samples were obtained from patients undergoing knee joint replacement surgery. Cyclopamine (CPA) was used for Hh pharmacological inhibition and IL-1 beta as an inflammatory insult. Our results showed that tamoxifen induced inactivation of Evc inhibited Hh overexpression and partially prevented chondrocyte hypertrophy during OA, although it did not ameliorate cartilage damage in DMM-Evc^cKO mice. Hh pathway inhibition did not modify the expression of proinflammatory mediators induced by IL-1 beta in human OA chondrocytes in culture. We found that hypertrophic-IHH-and inflammatory-COX-2-markers co-localized in OA cartilage samples. We concluded that tamoxifen induced inactivation of Evc partially prevented chondrocyte hypertrophy in DMM-Evc^cKO mice, but it did not ameliorate cartilage damage. Overall, our results suggest that chondrocyte hypertrophy per se is not a pathogenic event in the progression of OA.

Sonidegib potentiates the cancer cells' sensitivity to cytostatic agents by functional inhibition of ABCB1 and ABCG2 in vitro and ex vivo

Sonidegib (LDE-225) is a Hedgehog pathway inhibitor used for the therapy of basal cell carcinoma. In addition, the drug is a subject of clinical trials for the treatment of other solid tumors including non-small cell lung cancer (NSCLC). In this study, we explored the potential of sonidegib to act as a perpetrator of drug-drug interactions (DDIs) and modulator of transporter- and enzyme-mediated multidrug resistance (MDR). First, we found that transport functions of ABCB1 and ABCG2 were effectively inhibited by sonidegib in accumulation studies. In contrast, the drug did not cause fluctuations in mRNA levels of tested efflux transporters. In drug combination assays, sonidegib synergistically enhanced the cytotoxicity of daunorubicin and mitoxantrone in ABCB1- and ABCG2-overexpressing cells, respectively. Notably, similar phenomena were also observed in explant tumor cultures derived from NSCLC-suffering patients. In addition, the anticancer effects of sonidegib were not hampered by the expression of the ABC transporters associated with MDR. Last, sonidegib had no significant influence on the activity of CYP3A4 isoform in vitro. In summary, our work suggests that sonidegib can be considered a potential perpetrator of clinical DDIs on ABCB1 and ABCG2. After in vivo evaluation, its chemosensitizing properties might be projected into efficient and safe treatment regimen for the clinical management of NSCLC patients with high ABCB1/ABCG2 expression.

Update on glasdegib in acute myeloid leukemia - broadening horizons of Hedgehog pathway inhibitors

Numerous new emerging therapies, including oral targeted chemotherapies, have recently entered the therapeutic arsenal against acute myeloid leukemia (AML). The significant shift toward the use of these novel therapeutics, administered either alone or in combination with intensive or low-intensity chemotherapy, changes the prospects for the control of this disease, especially for elderly patients. Glasdegib, an oral Hedgehog pathway inhibitor, showed satisfactory response rates associated with moderate toxicity and less early mortality than standard induction regimens in this population. It was approved in November 2018 by the FDA and in June 2020 by the EMA for use in combination with low-dose cytarabine as a treatment of newly-diagnosed AML in patients aged ≥ 75 and/or unfit for intensive induction chemotherapy. The current paper proposes an extensive, up-to-date review of the preclinical and clinical development of glasdegib. Elements of its routine clinical use and the landscape of ongoing clinical trials are also stated.

Advances in the drug management of basal cell carcinoma

INTRODUCTION

Basal cell carcinoma (BCC) is the most common skin cancer in humans. Recently, BCCs were suggested to be classified into 'easy to treat' and 'difficult to treat,' and different therapeutic options are suggested for their management.

AREAS COVERED

In this review, the authors discuss treatment options that are approved, recommended for, or are still in development for treatment of BCC. The review covers approved local therapies, such as imiquimod and 5-fluorouracil, and systemic therapies, such as hedgehog inhibitors. New medical agents, investigated in clinical trials, are reviewed. These include: targeted therapies, such as GLI antagonists or anti-VEGFR agents, immunotherapies, such as checkpoint inhibitors, recombinant cytokines or silencing RNA, as well as intralesional virotherapies with modified adeno- or herpes viruses.

EXPERT OPINION

The progress made in recent years has improved the management of patients with advanced BCC; however, neither tumor targeting nor immune system engaging agents provide a cure. New treatment approaches directed not only to known targets but also the tumor microenvironment are in development and are anticipated to improve the management of difficult to treat BCC.

Using drug scheduling to manage adverse events associated with hedgehog pathway inhibitors for basal cell carcinoma

Basal cell carcinoma (BCC) is the most common malignancy and form of skin cancer worldwide; advanced BCC, either as locally advanced BCC (laBCC) or metastatic BCC (mBCC), can cause substantial tissue invasion and morbidity. Until the recent availability of the hedgehog pathway inhibitors (HHIs) sonidegib and vismodegib, treatment options for advanced BCC were limited. These agents demonstrate efficacy in patients with laBCC and mBCC; however, the adverse events (AEs) associated with these agents can lead to treatment interruption or discontinuation and reduced quality of life, all of which significantly impact long-term adherence to therapy, which might affect clinical outcome. Given that most AEs are class-related effects, switching HHIs does not appear to lead to a significantly different AE profile, underscoring the importance of maintaining patients on their first HHI. Interrupting treatment of sonidegib and vismodegib does not appear to undermine the efficacy of these agents and is therefore a practical option to manage AEs in order to maintain continued treatment and disease control.

Microtubule Targeting Agents in Disease: Classic Drugs, Novel Roles

Microtubule-targeting agents (MTAs) represent one of the most successful first-line therapies prescribed for cancer treatment. They interfere with microtubule (MT) dynamics by either stabilizing or destabilizing MTs, and in culture, they are believed to kill cells via apoptosis after eliciting mitotic arrest, among other mechanisms. This classical view of MTA therapies persisted for many years. However, the limited success of drugs specifically targeting mitotic proteins, and the slow growing rate of most human tumors forces a reevaluation of the mechanism of action of MTAs. Studies from the last decade suggest that the killing efficiency of MTAs arises from a combination of interphase and mitotic effects. Moreover, MTs have also been implicated in other therapeutically relevant activities, such as decreasing angiogenesis, blocking cell migration, reducing metastasis, and activating innate immunity to promote proinflammatory responses. Two key problems associated with MTA therapy are acquired drug resistance and systemic toxicity. Accordingly, novel and effective MTAs are being designed with an eye toward reducing toxicity without compromising efficacy or promoting resistance. Here, we will review the mechanism of action of MTAs, the signaling pathways they affect, their impact on cancer and other illnesses, and the promising new therapeutic applications of these classic drugs.

Hedgehog Pathway Inhibitors against Tumor Microenvironment

Targeting the hedgehog (HH) pathway to treat aggressive cancers of the brain, breast, pancreas, and prostate has been ongoing for decades. Gli gene amplifications have been long discovered within malignant glioma patients, and since then, inhibitors against HH pathway-associated molecules have successfully reached the clinical stage where several of them have been approved by the FDA. Albeit this success rate implies suitable progress, clinically used HH pathway inhibitors fail to treat patients with metastatic or recurrent disease. This is mainly due to heterogeneous tumor cells that have acquired resistance to the inhibitors along with the obstacle of effectively targeting the tumor microenvironment (TME). Severe side effects such as hyponatremia, diarrhea, fatigue, amenorrhea, nausea, hair loss, abnormal taste, and weight loss have also been reported. Furthermore, HH signaling is known to be involved in the regulation of immune cell maturation, angiogenesis, inflammation, and polarization of macrophages and myeloid-derived suppressor cells. It is critical to determine key mechanisms that can be targeted at different levels of tumor development and progression to address various clinical issues. Hence current research focus encompasses understanding how HH controls TME to develop TME altering and combinatorial targeting strategies. In this review, we aim to discuss the pros and cons of targeting HH signaling molecules, understand the mechanism involved in treatment resistance, reveal the role of the HH pathway in anti-tumor immune response, and explore the development of potential combination treatment of immune checkpoint inhibitors with HH pathway inhibitors to target HH-driven cancers.

Cell Differentiation Trajectory-Associated Molecular Classification of Osteosarcoma

This study aims to investigate the differentiation trajectory of osteosarcoma cells and to construct molecular subtypes with their respective characteristics and generate a multi-gene signature for predicting prognosis. Integrated single-cell RNA-sequencing (scRNA-seq) data, bulk RNA-seq data and microarray data from osteosarcoma samples were used for analysis. Via scRNA-seq data, time-related as well as differentiation-related genes were recognized as osteosarcoma tumor stem cell-related genes (OSCGs). In Gene Expression Omnibus (GEO) cohort, osteosarcoma patients were classified into two subtypes based on prognostic OSCGs and it was found that molecular typing successfully predicted overall survival, tumor microenvironment and immune infiltration status. Further, available drugs for influencing osteosarcoma via prognostic OSCGs were revealed. A 3-OSCG-based prognostic risk score signature was generated and by combining other clinic-pathological independent prognostic factor, stage at diagnosis, a nomogram was established to predict individual survival probability. In external independent TARGET cohort, the molecular types, the 3-gene signature as well as nomogram were validated. In conclusion, osteosarcoma cell differentiation occupies a crucial position in many facets, such as tumor prognosis and microenvironment, suggesting promising therapeutic targets for this disease.

Switching Hedgehog inhibitors and other strategies to address resistance when treating advanced basal cell carcinoma

Although basal cell carcinoma (BCC) is often managed successfully with surgery, patients with locally advanced BCC (laBCC) or metastatic BCC (mBCC) who are not candidates for surgery or radiotherapy have limited treatment options. Most BCCs result from aberrant Hedgehog pathway activation in keratinocyte tumor cells, caused by sporadic or inherited mutations. Mutations in the patched homologue 1 gene that remove its inhibitory regulation of Smoothened homologue (SMO) or mutations in SMO that make it constitutively active, lead to Hedgehog pathway dysregulation and downstream activation of GLI1/2 transcription factors, promoting cell differentiation and proliferation. Hedgehog inhibitors (HHIs) block overactive signaling of this pathway by inhibiting SMO and are currently the only approved treatments for advanced BCC. Two small-molecule SMO inhibitors, vismodegib and sonidegib, have shown efficacy and safety in clinical trials of advanced BCC patients. Although these agents are effective and tolerable for many patients, HHI resistance occurs in some patients. Mechanisms of resistance include mutations in SMO, noncanonical cell identity switching leading to tumor cell resistance, and non-canonical pathway crosstalk causing Hedgehog pathway activation. Approaches to managing HHI resistance include switching HHIs, HHI and radiotherapy combination therapy, photodynamic therapy, and targeting Hedgehog pathway downstream effectors. Increasing understanding of the control of downstream effectors has identified new therapy targets and potential agents for evaluation in BCC. Identification of biomarkers of resistance or response is needed to optimize HHI use in patients with advanced BCC. This review examines HHI resistance, its underlying mechanisms, and methods of management for patients with advanced BCC.

Targeted Therapy in Pediatric AML: An Evolving Landscape

The outcomes associated with pediatric acute myeloid leukemia (AML) have improved over the last few decades, with the implementation of intensive chemotherapy, hematopoietic stem cell transplant, and improved supportive care. However, even with intensive therapy and the use of HSCT, both of which carry significant risks of short- and long-term side effects, approximately 30% of children are not able to be cured. The characterization of AML in pediatrics has evolved over time and it currently involves use of a variety of diagnostic tools, including flow cytometry and comprehensive genomic sequencing. Given the adverse effects of chemotherapy and the need for additional therapeutic options to improve outcomes in these patients, the genomic and molecular architecture is being utilized to inform selection of targeted therapies in pediatric AML. This review provides a summary of current, targeted therapy options in pediatric AML.

The Role of the Hedgehog Pathway in Chemoresistance of Gastrointestinal Cancers

The hedgehog pathway, which plays a significant role in embryonic development and stem cell regulation, is activated in gastrointestinal cancers. Chemotherapy is widely used in cancer treatment. However, chemoresistance becomes a substantial obstacle in cancer therapy. This review focuses on the recent advances in the hedgehog pathway's roles in drug resistance of gastrointestinal cancers and the novel drugs and strategies targeting hedgehog signaling.