Activation Of Hedgehog Signaling Pathway Research Articles

MDB-79. THE DEUBIQUITINATING ENZYME USP7 COOPERATES WITH SONIC HEDGEHOG SIGNALING TO PROMOTE MEDULLOBLASTOMA

Abstract BACKGROUND Constitutive activation of the Sonic Hedgehog (SHH) signaling pathway during cerebellar development may lead to medulloblastoma (MB), one of the most common malignant pediatric brain tumor. Clinically, SHH-MB with mutations downstream of SMO or TP53-mutated are a real challenge and alternative targeted therapies are sorely needed for this group of patients. In SHH-MB, the transcription factor Atoh1 is constitutively overexpressed and essential for tumor initiation and progression. Previous work demonstrated that proteasomal-mediated degradation of Atoh1 induces tumor regression in vitro and in vivo, therefore deciphering mechanisms controlling Atoh1 stabilization should provide new avenues for drug development in SHH-MB. METHODS Using a proteomic approach, we identified the deubiquitinating enzyme Usp7 as a positive regulator of Atoh1 in MB cells. We then applied a SILAC-based quantitative ubiquitinomics to investigate the Usp7 target landscape in SHH-MB. We also employed several biochemical approaches to demonstrate the functional interaction between Atoh1 and Usp7 in SHH-MB. In parallel, we validated the impact of Usp7 depletion in vitro and in vivo using relevant SHH-MB models. Last, we investigated large transcriptomic and proteomic datasets to unveil the prognostic value of Usp7 in SHH-MB human tumors. RESULTS We demonstrate that Usp7 binds and accumulates Atoh1 protein by counteracting its ubiquitylation. Post-natal electroporation in vivo directly into the developing cerebella also indicates that overexpression of Usp7 promotes proliferation, whereas in the absence of Atoh1 Usp7 was no longer able to spread cell growth, demonstrating a functional link between the Usp7-Atoh1 axis. In vivo, disruption of Usp7 expression in SHH-MB blocks tumor proliferation. Pharmacological inhibition of Usp7 triggers tumor growth in a syngeneic SHH MB mouse model. Lastly, SHH-MB cells with either TP53 or SMO downstream mutations are sensitive to Usp7 inhibition. CONCLUSIONS Overall, our data pinpoint Usp7 as a promising target against Atoh1, a master regulator of SHH-MB.

Metatypical BCC of The Ear: Partial Amputation of The Auricle as Adequate Dermatosurgical Approach

Non-melanoma skin cancer is the most common cancer in the world (1). Basal cell carcinoma (BCC) is the most common malignant neoplasia of the skin, accounting for approximately 80% of all cutaneous tumors (2). High cumulative ultraviolet (UV) light exposure and the presence of Fitzpatrick skin phototype I or II are pathogenetic risk factors (3). UV radiation induces mutations in the tumor suppressor PTCH1 gene, leading to increased Hedgehog (XX/Hh) signaling pathway activity (4). Dysfunction or abnormal activation of the Hedgehog signaling pathway is associated with disorders of embryonic development and the development of cancers such as Goltz–Gorlin syndrome for example (5). BCC has the characteristics of a locally invasive, slow-growing skin cancer, with a metastatic incidence between 0.0028-0.5%, with areas in the head and neck most commonly affected (6). Metatypical basal cell carcinoma (MTBCC) is a rare variant of BCC that has histopathological characteristics of both basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) (7).

YAP/Aurora A-mediated ciliogenesis regulates ionizing radiation-induced senescence via Hedgehog pathway in tumor cells

Primary cilia are antenna-like organelles that play critical roles in sensing and responding to various signals. Nevertheless, the function of primary cilia in cellular response to ionizing radiation (IR) in tumor cells remains unclear. Here, we show that primary cilia are frequently expressed in tumor cells and tissues. Notably, IR promotes cilia formation and elongation in time- and dose-dependent manners. Mechanistic study shows that the suppression of YAP/Aurora A pathway contributes to IR-induced ciliogenesis, which is diminished by Aurora A overexpression. The ciliated tumor cells undergo senescence but not apoptosis in response to IR and the abrogation of cilia formation is sufficient to elevate the lethal effect of IR. Furthermore, we show that IR-induced ciliogenesis leads to the activation of Hedgehog signaling pathway to drive senescence and resist apoptosis, and its blockage enhances cellular radiosensitivity by switching senescence to apoptosis. In summary, this work shows evidence of primary cilia in coordinating cellular response to IR in tumor cells, which may help to supply a novel sensitizing target to improve the outcome of radiotherapy.

Chinese guildeline on diagnosis and treatment of basal cell carcinoma (2023 edition)

Basal cell carcinoma (BCC) is the most common skin malignancy, with a higher prevalence in Caucasians than in East Asians. Although there is a lack of epidemiological data in China, it is generally believed that the incidence of BCC in China is increasing due to the aging population. A variety of risk factors are related to the occurrence of BCC, among which ultraviolet rays and gene mutations play a major role, especially the abnormal activation of Hedgehog (Hh) signaling pathway, which is considered to be the most important pathogenesis of BCC. The clinical manifestations of BCC are highly specific, and most experienced doctors can make a preliminary diagnosis by clinical manifestations. Dermoscopy and other imaging methods can greatly improve the accuracy of diagnosis, but there are still some atypical or rare types of BCC that need further confirmation through histopathological examination. This guideline is initiated by the National Clinical Research Center for Skin and Immune Diseases (based on Peking University First Hospital). It has invited a panel of experts consisting of 24 senior dermatologists specializing in dermatologic surgery from the Dermatologic Surgery Group of the Chinese Medical Doctor Association of Dermatology, the Dermatologic Surgery Group of the Dermatology & Venereology Committee, Chinese Association of Integration Medicine, and the Dermatologic Surgery and Cosmetic Branch of Clina Leprosy Association. In addition, experts from the Burn and Plastic Surgery (Maxillofacial), Ophthalmology, Otolaryngology, Head and Neck Surgery, Radiation Therapy, and Pathology were also invited to participate. This panel forms the "Chinese Guideline for the Diagnosis and Treatment of Basal Cell Carcinoma" expert group. Based on the latest domestic and international research findings, the guideline was developed through four rounds of discussions by the expert group and revised to provide valuable references for clinical healthcare providers in the diagnosis and treatment of BCC.

Comparative analysis identifies genetic and molecular factors associated with prognostic clusters of PANoptosis in glioma, kidney and melanoma cancer

The importance of inflammatory cell death, PANoptosis, in cancer is increasingly being recognized. PANoptosis can promote or inhibit tumorigenesis in context-dependent manners, and a computational approach leveraging transcriptomic profiling of genes involved in PANoptosis has shown that patients can be stratified into PANoptosis High and PANoptosis Low clusters that have significant differences in overall survival for low grade glioma (LGG), kidney renal cell carcinoma (KIRC) and skin cutaneous melanoma (SKCM). However, the molecular mechanisms that contribute to differential prognosis between PANoptosis clusters require further elucidation. Therefore, we performed a comprehensive comparison of genetic, genomic, tumor microenvironment, and pathway characteristics between the PANoptosis High and PANoptosis Low clusters to determine the relevance of each component in driving the differential associations with prognosis for LGG, KIRC and SKCM. Across these cancer types, we found that activation of the proliferation pathway was significantly different between PANoptosis High and Low clusters. In LGG and SKCM, we also found that aneuploidy and immune cell densities and activations contributed to differences in PANoptosis clusters. In individual cancers, we identified important roles for barrier gene pathway activation (in SKCM) and the somatic mutation profiles of driver oncogenes as well as hedgehog signaling pathway activation (in LGG). By identifying these genetic and molecular factors, we can possibly improve the prognosis for at risk-stratified patient populations based on the PANoptosis phenotype in LGG, KIRC and SKCM. This not only advances our mechanistic understanding of cancer but will allow for the selection of optimal treatment strategies.

Triptolide inhibits epithelial ovarian tumor growth by blocking the hedgehog/Gli pathway.

Epithelial ovarian cancer (EOC), the most predominant subtype of ovarian cancer (OC), involves poor prognosis and exhibits high aggression. Triptolide (TPL), like other Chinese herbs, has historically played a significant role in modern medicine. The screening system based on Gli-dependent luciferase reporter activity assessed the effects of over 800 natural medicinal materials on hedgehog (Hh) signaling pathway activity and discovered that TPL had an excellent inhibitory effect on Hh signaling pathway activity. However, the significance and mechanism of TPL involvement in regulating the Hh pathway have not been well explored. Thus, this work aimed to understand better how TPL affects the Hh pathway activity, which, in turn, influences the biological behavior of EOC. Our findings observed that Smo agonist SAG-induced EOC cell proliferation, migration, and invasion were drastically reversed by TPL in a concentration-dependent pattern. Further evidence suggested that TPL promotes the degradation of Gli1 and Gli2 to inhibit the activity of the Hh signaling pathway by relying on Gli1 and Gli2 ubiquitination. Our in vivo studies also confirmed that TPL could significantly inhibit the tumor growth of EOC. Taken together, our results revealed that one of the antitumor mechanisms of TPL was the targeted inhibition of the Hh/Gli pathway.

Tau tubulin kinase 1 and 2 regulate ciliogenesis and human pluripotent stem cells–derived neural rosettes

Primary cilia are key regulators of embryo development and tissue homeostasis. However, their mechanisms and functions, particularly in the context of human cells, are still unclear. Here, we analyzed the consequences of primary cilia modulation for human pluripotent stem cells (hPSCs) proliferation and differentiation. We report that neither activation of the cilia-associated Hedgehog signaling pathway nor ablation of primary cilia by CRISPR gene editing to knockout Tau Tubulin Kinase 2 (TTBK2), a crucial ciliogenesis regulator, affects the self-renewal of hPSCs. Further, we show that TTBK1, a related kinase without previous links to ciliogenesis, is upregulated during hPSCs-derived neural rosette differentiation. Importantly, we demonstrate that while TTBK1 fails to localize to the mother centriole, it regulates primary cilia formation in the differentiated, but not the undifferentiated hPSCs. Finally, we show that TTBK1/2 and primary cilia are implicated in the regulation of the size of hPSCs-derived neural rosettes.

Effects of different immune microenvironment characteristics on predictive efficacy of PTCH1 mutations in immune checkpoint inhibitor therapy of solid tumors.

e21026 Background: The PTCH1 gene encoding the protein corticosteroid receptor, which regulates the activity of the Sonic Hedgehog (SHH) signaling pathway. Mutations in PTCH1 result in disruption of the SHH signaling pathway and are closely related to the development of various solid tumors. Previous research has shown that mutations of the PTCH1 gene may result in decreased of antigen expression on the surface of tumor cells. However, relevant correlation with the efficacy of ICI therapy and immune microenvironment are still lacking. Methods: NGS data from an independent cohort (the MSKCC study cohort) of 1661 patients and Chinese clinical dataset (panel on 381/733-gene) of 35337 patients with pan-cancer to explore the association between PTCH1 mutations and immune biomarkers. TMB was defined as total number of somatic non-synonymous mutations in coding region. MSI was evaluated by NGS of 500 known MSI loci. PD-L1 expression was evaluated using immunohistochemistry (Dako 22C3). Patients from three independent cohorts (OAK, POPLAR and MSKCC study cohort) and were used to analyze the correlation between PTCH1 mutations and the efficacy of immune checkpoint blockade immunotherapies (ICIs). Estimation of immune filtration cells scores were conducted via TIMER2.0 (http://timer.cistrome.org/). Results: In Chinese cohort, there were 1384 (3.91%) patients harboured PTCH1 mutation ( PTCH1mut), slightly more than the MSKCC cohort (2.52%, 42/1661). For the TMB, both Chinese (median, 24.14 Muts/Mb vs 8.52 Muts/Mb, P ＜0.0001) and MSKCC (median, 22.30 Muts/Mb vs 5.90 Muts/Mb, P = 0.0035) cohort were associated with higher TMB than the wild-type. Supplemental analysis of MSI in the Chinese cohort showed significant differences between the PTCH1mut and PTCH1wt groups (P ＜0.0001), but not on PD-L1 levels (P = 0.64). In terms of prognostic effect with ICIs therapy, PTCH1mut were significantly associated with the overall survival (OS) of NSCLC (median, 5 months vs 11 months; HR = 1.61; 95% CI, 1.00-2.60; P = 0.049) and colorectal (median, 11 months vs 8 months; HR = 0.27; 95% CI, 0.08–0.90; P = 0.023). Interestingly, PTCH1mut in NSCLC was inversely associated with ICIs efficacy, as opposed to other solid tumors. Exploring the correlation between PTCH1 and immune microenvironment, it was found that CD4+ T cell (P＜0.001), macrophages (P＜0.001), NK cells (P＜0.001), and CD8+ T cells (P = 0.015) infiltration was significantly positively correlated in colorectal. But the infiltration of most immune cells was negatively correlated with PTCH1mut in NSCLC, that the B cells (P = 0.005), macrophages (P = 0.049), and NK cells (P = 0.022) had a significant difference. Conclusions: The results showed that the PTCH1 had a high correlation in solid tumors with TMB and MSI. The PTCH1 might a potential biomarker for ICIs therapy, and the immune microenvironment may be a factor affecting of it.

Berberine is a suppressor of Hedgehog signaling cascade in colorectal cancer

BackgroundColorectal cancer (CRC) is a malignant affliction that burdens people globally. Overactivated Hedgehog signal is highly implicated in CRC pathogenesis. Phytochemical berberine exerts strong potency on CRC, with molecular mechanism elusive. PurposeWe sought to study berberine's anti-CRC action and explore its underlying mechanism based on Hedgehog signaling cascade. MethodsIn CRC HCT116 cells and SW480 cells treated with berberine, the proliferation, migration, invasion, clonogenesis, apoptosis and cell cycle were measured, with determination of Hedgehog signaling pathway activity. Following establishment of mouse model of HCT116 xenograft tumor, the efficacies of berberine on carcinogenesis, pathological manifestation and malignant phenotypes of CRC were examined, with analysis of Hedgehog signaling axis in HCT116 xenograft tumor tissues. Additionally, toxicological study of berberine was conducted on zebrafish. ResultsBerberine was discovered to suppress the proliferation, migration, invasion and clonogenesis of HCT116 cells and SW480 cells. Furthermore, berberine caused cell apoptosis and blockaded cell cycle at phase G0/G1 in CRC cells, with dampened Hedgehog signaling cascade. In HCT116 xenograft tumor of nude mice, berberine inhibited tumor growth, alleviated pathological score, and promoted apoptosis and cell cycle arrest in tumor tissues, through constraining Hedgehog signaling. The toxicological study of berberine on zebrafish indicated that berberine incurred damage to the liver and heart of zebrafish at high dosage and prolonged administration. ConclusionsTaken together, berberine may inhibit the malignant phenotypes of CRC through diminishing Hedgehog signaling cascade. However, the potential adverse reactions should be taken into account upon abuse of berberine.

B13, a well-tolerated inhibitor of hedgehog pathway, exhibited potent anti-tumor effects against colorectal carcinoma in vitro and in vivo

Abnormal activation of Hedgehog (Hh) signaling pathway mediates the genesis and progression of various tumors [1]. Currently, three drugs targeting the Hh signaling component Smoothened (Smo) have been marketed for the clinical treatment of basal cell tumors or acute myeloid leukemia. However, drug resistance is a common problem in those drugs, so the study of Smo inhibitors that can overcome drug resistance has important guiding significance for clinical adjuvant drugs. MTT assay, clone formation assay and EdU assay were used to detect the proliferation inhibitory activity of the drugs on tumor cells. The effect of B13 on cell cycle and apoptosis were detected by flow cytometry. An acute toxicity test was used to detect the toxicity of B13 in vivo, and xenograft tumor model was used to detect the efficacy of B13 in vivo. The binding of B13 to Smo was studied by BODIPY-cyclopamine competitive binding assay and molecular docking. The effect of B13 on the expression and localization of downstream target gene Gli1/2 of Smo was investigated by Western Blot and immunofluorescence assay. SmoD473H mutant cell line was constructed to study the effect of B13 against drug resistance. (1) B13 had the strongest inhibitory activity against colorectal cancer cells. (2) B13 can effectively inhibit the clone formation and EdU positive rate of colon cancer cells. (3) B13 can block the cell cycle in the G2/M phase and cell apoptosis. (4) B13 has low toxicity in vivo, and its efficacy in vivo is better than that of the Vismodegib. (5) Molecular docking and BODIPY-cyclopamine experiments showed that B13 could bind to Smo protein. (6) B13 can inhibit the protein expression of Gli1, the downstream of Smo, and inhibit its entry into the nucleus. (7) B13 could inhibit the expression of Gli1 in the HEK293 cells with SmoD473H, and the molecular docking results showed that B13 could bind SmoD473H protein. B13 with the best anti-tumor activity was screened out by MTT assay. In vitro, pharmacodynamics experiments showed that B13 could effectively inhibit the proliferation and metastasis of colorectal cancer cells, induce cell cycle arrest, and induce cell apoptosis. In vivo pharmacodynamics experiments showed that B13 was superior to Vismodegib in antitumor activity and had low toxicity in vivo. Mechanism studies have shown that B13 can bind Smo protein, inhibit the expression of downstream Gli1 and its entry into the nucleus. Notably, B13 overcomes resistance caused by SmoD473H mutations.

Novel Approach to the Hedgehog Signaling Pathway: Combined Treatment of SMO and PTCH Inhibitors

Purpose: Abnormal Sonic Hedgehog signaling Pathway (Shh) activation is crucial for development of cancer stem cells, neoplastic growth and epithelial-mesenchymal transition processes in adulthood. Activation of Hedgehog signaling pathway may induces the changes in cilia found in the cell membrane, iniciates the Gli1 transcription factor that is translocated to the cell nucleus and finally, the target genes are transcribed. In this study, invastigation of the antiproliferative, anti-invasive and antimigrative effect of the combined use of robotnikinin (Ptch1 antagonist) and vismodegib (Smo inhibitor) on the hedgehog signaling pathway was aimed. 
 
 Material and Methods: After demonstarting the presence of the hedgehog signaling pathway in the glioblastoma cell line U87-MG, the effect of the combined use of the robotnikinin and the vismodegib on the hedgehog signaling pathway was investigated. In-vitro cell proliferation, migration, and invasion analysis of the combination of antagonist and inhibitor and in silico drug-likeness analysis were performed.
 
 Results: Two different combinations of robotnikinin and vismodegib were tested. In vitro studies show that the combined use of agents in combined treatments of Smo and Ptch1is more effective than their individual usage.
 
 Conclusion: Inhibition of the hedgehog signaling pathway with specific inhibitors and antagonists is considered an innovative strategy for cancer therapy.

DNAR-13. SONIDEGIB AND GANT61 INDUCE DNA DAMAGE IN PEDIATRIC SONIC HEDGEHOG MEDULLOBLASTOMA

Abstract Medulloblastoma is the most common malignant brain tumor in children, accounting for 20-25% of all pediatric brain tumors. The current standard of care includes both craniospinal and focal radiation therapy which leads to long term consequences in the pediatric population such as bone and tissue hypoplasia, decreased neurocognitive functioning, as well as an increased risk for secondary radiation induced cancers. Thus, there is a need for novel approaches to radiation therapy that can effectively target and kill tumor cells while minimizing radiation toxicity in healthy tissue in the pediatric patient population. The dysregulation and constitutive activation of the Sonic Hedgehog (SHH) signaling pathway accounts for ~30% of all medulloblastomas. In addition to playing a role in tumorigenesis, the SHH pathway is known to play a role in the radiation sensitivity and risk of tumor recurrence. We hypothesize that inhibiting the SHH pathway at Smoothened (Smo) or Gli1 will increase DNA damage, resulting in increased cell killing following radiation therapy. We found that treatment of medulloblastoma cells with the drug Sonidegib or GANT61 decreased the expression of the respective targets Smo and Gli1. Both drugs also significantly decreased expression of FANCD2, a DNA damage repair gene essential for homologous recombination. Pretreatment with Sonidegib or GANT61 resulted functionally with decreased tumor cell viability and self-renewal following radiation. These data suggest that Smo and Gli1 inhibition are promising targets for increasing the radiation sensitivity of pediatric SHH medulloblastoma.

Functional analysis of missense mutations in GLI2 and GLI3 involved in congenital heart disease

Objective: In this study, we aimed to explore the biological functions of 10 rare case-specific missense mutations in GLI2 and 4 in GLI3, which were previously screened in a cohort of 412 patients with congenital heart disease (CHD) and 213 normal controls from Shandong Province, China. Methods: A dual-luciferase reporter assay was used to assess the effects of these mutations in GLI2 and GLI3 on the activity of the sonic Hedgehog signaling pathway in HEK293T cells. Differences in protein levels between mutant and wild-type GLI2 and GLI3 were detected in HEK293T cells using Western blotting. Results: The dual-luciferase reporter assay showed that compared to the wild-type GLI2 protein, p.A1113V significantly increased activation of the sonic Hedgehog signaling pathway, whereas p.H78P and p.I1451S did not have a significant effect. The other mutations largely reduced the activation effect. Compared with the wild-type GLI3 protein, only p.A286V, among the four mutations, significantly reduced the activation effect on the SHH signaling pathway. Western blotting data showed reduced expression of GLI2 p.G716V, GLI2 p.K736N, GLI2 p.I1451S, and GLI3 p.A286V, whereas the remaining mutations had no significant effects. Conclusion: The mutations GLI2 c.2147G>T (p.G716V), GLI2 c.2208G>C (p.K736N), and GLI3 c.857C>T (p.A286V) involved in CHD affect the regulation of the sonic Hedgehog signaling pathway; thus, these rare missense mutations in GLI2 and GLI3 might increase the risk of CHD.

SAG-dihydrochloride enhanced the expression of germ cell markers in the human bone marrow- mesenchymal stem cells (BM-MSCs) through the activation of GLI-independent hedgehog signaling pathway

Different studies indicated that the enhancing the expression of germ cell markers improved the efficiency of stem cells in the generation of germ line cells. The aim of the present study was to investigate the effect of SAG-dihydrochloride on the expression of germ cell markers in the human bone marrow-mesenchymal stem cells (BM-MSCs). For this purpose, the human BM-MSCs were cultured in the medium containing different concentrations of SAG-dihydrochloride (10, 20 and 30 µM). After RNA extraction and cDNA synthesis, the expression level of PTCH1, GLI1, PLZF, DDX4 and STRA8 genes were determined by using SYBR Green Real time PCR. The analysis of the results obtained from PTCH1 and GLI1 expression indicated that SAG-dihydrochloride had the ability to enhance the expression of germ cell markers in a Gli-independent manner. Furthermore, the significant increased expression of STRA8 was observed in the BM-MSCs treated by 10 µM SAG-dihydrochloride for 4 and 6 days (p < 0.05). There was also the up-regulation of DDX4 in the BM-MSCs following treatment with 20 µM SAG-dihydrochloride for 4 and 6 days. The obtained results suggested that treatment with SAG-dihydrochloride increased the expression of germ cell markers in the human BM-MSCs through the activation of non-canonical sonic hedgehog signaling pathway.

Human osteoprogenitor cells obtained from traumatic heterotopic ossification samples showed enhanced osteogenic differentiation potential and ERK/hedgehog signaling than that from normal bone.

Traumatic heterotopic ossification (HO) refers to the abnormal ectopic osteogenesis following trauma, causing limb dysfunction and seriously lowering the life quality of patients. Aberrant osteogenic behavior of progenitor cells that ectopically accumulated within the soft tissues are believed to be responsible for HO formation. However, the detailed mechanism still remained to be clarified. Here in this study, we successfully isolated osteoprogenitors from human heterotopic ossification tissues (HO-ops) and identified their stemness and multi-directional differentiation potential. Using alkaline phosphatase staining together with alizarin red staining, we confirmed that the HO-ops in the heterotopic ossified tissues gained greater osteogenic potential than the normal human bone marrow mesenchymal stem cells (HBMSCs). RT-qPCR also indicated that HO-ops obtained more gene transcriptions of critical osteogenic determinators than HBMSCs. In addition, through Western blot, we proved that ERK signaling pathway and hedgehog signaling pathway were significantly activated in the HO-ops. When U0126 and cyclopamine were used to inhibit ERK signaling and hedgehog signaling respectively, the osteogenic potential of HO-ops decreased significantly. The hedgehog signaling and ERK signaling also showed cross-talk in HO-ops during osteogenic differentiation in HO-ops during osteogenic differentiation. The elevated ERK signaling and hedgehog signaling were further confirmed in the human traumatic HO sample sections by immunohistochemical staining. In sum, our results showed that the activation of ERK and hedgehog signaling pathway jointly enhanced the osteogenic potential of HO-ops to induce the formation of traumatic HO, which provides novel insights into the molecular basis of HO formation and offers promising targets for future therapeutic strategy.

Canonical Hedgehog Pathway and Noncanonical GLI Transcription Factor Activation in Cancer.

The Hedgehog signaling pathway is one of the fundamental pathways required for development and regulation of postnatal regeneration in a variety of tissues. The pathway has also been associated with cancers since the identification of a mutation in one of its components, PTCH, as the cause of Basal Cell Nevus Syndrome, which is associated with several cancers. Our understanding of the pathway in tumorigenesis has expanded greatly since that initial discovery over two decades ago. The pathway has tumor-suppressive and oncogenic functions depending on the context of the cancer. Furthermore, noncanonical activation of GLI transcription factors has been reported in a number of tumor types. Here, we review the roles of canonical Hedgehog signaling pathway and noncanonical GLI activation in cancers, particularly epithelial cancers, and discuss an emerging concept of the distinct outcomes that these modes have on cancer initiation and progression.

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.

Caspase-3–Induced Activation of SREBP2 Drives Drug Resistance via Promotion of Cholesterol Biosynthesis in Hepatocellular Carcinoma

This study finds that cholesterol biosynthesis supports the expansion of cancer stem cell populations to drive resistance to tyrosine kinase inhibitor therapy in hepatocellular carcinoma, identifying potential therapeutic approaches for improving cancer treatment.

Abstract 718: Significantly strong protective efficacy of silibinin against basal cell carcinoma growth and progression

Abstract Basal cell carcinoma (BCC) is the most common skin malignancy accounting for ∼80% of non-melanoma skin cancers (NMSCs). It arises in basal cells of skin that line the deepest layer of the epidermis. The most important risk factor for BCC is solar ultraviolet B (UVB) radiation that results in DNA damage (CPDs formation) in skin epidermis, which, if not repaired, leads to fixation of mutations and initiation of skin carcinogenesis. One of the key molecular features of BCC is sustained activation of Hedgehog signaling (Hh) pathway through inactivating mutations in tumor suppressor gene Patched (Ptch) or activating mutations in Smoothened (Smo). Therefore, extensive efforts have been made to target activated Hh pathway for the treatment of BCC, though with toxic side effects. With regards to chemoprevention of BCC, the agents which target the events associated with UVB-induced DNA damage repair, together with targeting promotion/progression stages, might provide more effective broad-spectrum opportunities to intervene at the earliest. Utilizing the well-established patched (Ptch)+/- mouse model of UVB radiation-induced BCC formation, our approach in this study was to target BCC development and its prevention by employing silibinin (a natural flavonolignan from milk thistle seeds). Previously, we have extensively reported the efficacy of silibinin against UVB-induced photodamage and photo-carcinogenesis, and also recently reported silibinin efficacy against BCC growth in cell culture (including anti-BCC drug-resistant cell lines) and mouse BCC allograft tumors. In this study, both male and female (Ptch)+/- mice were irradiated with 240 mJ/cm2 UVB dose, 3 times per week (M, W, F) for 26 and 46 weeks with or without silibinin. Silibinin (9 mg/200μl of acetone) was applied topically, 30 min post and pre-UVB exposure. Our study shows that chronic UVB exposure induced BCCs in Ptch+/- mice. Treatment with silibinin post and pre-UVB exposure for 26 weeks decreased BCC lesion numbers (39-65%), and cross-sectional area (45-72%) p&amp;lt;0.001, respectively compared to UVB alone. Furthermore, continuous UVB exposure up to 46 weeks increased the BCC lesion number by ∼6 folds and cross-sectional area by ∼3.4 folds (p&amp;lt;0.001) respectively. Notably, silibinin (irrespective of post and pre-UVB treatment) significantly halted the progression of BCC (81-94%, p&amp;lt;0.001), even upon prolonged UVB exposure. Histological analysis showed increased dysplasia, fibro-sarcoma, and squamous cell carcinoma upon UVB exposure, which significantly decreased upon silibinin treatment. In addition, mechanistic studies revealed that silibinin significantly decreased basal cell proliferation (Ki-67) and the expression of cytokeratins (14 and 15), and Hh signaling mediators Smo and Gli1 in the BCC lesions. Together, our findings demonstrate that silibinin has the potential to prevent the growth and progression of UVB-induced BCC. Citation Format: Sandeep Paudel, Komal Raina, Vasundhara R. Tiku, Akhilendra Maurya, David J. Orlicky, Zhiying You, Cindy M. Rigby, Gagan Deep, Rama Kant, Bupinder Raina, Chapla Agarwal, Rajesh Agarwal. Significantly strong protective efficacy of silibinin against basal cell carcinoma growth and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 718.

MEDB-45. Functional genomics identifies epigenetic regulators as novel therapeutic targets for sonic hedgehog medulloblastoma

Medulloblastoma (MB) is among the most common malignant childhood brain tumors that comprises a group of four molecularly distinct diseases. A significant proportion of these tumors is characterized by aberrant activation of the canonical sonic hedgehog (SHH) signaling pathway. Although small-molecule inhibitors targeting Smoothened (SMO) have proven a promising treatment approach for SHH-MB subgroup, primary or acquired resistance impedes its clinical efficacy. Therefore, novel targeted approaches are urgently needed to improve therapeutic strategies for this tumor entity. Here, we conducted a genome-wide CRISPR/Cas9 knockout screen in a murine and a human SHH-MB cell line, SMB21 and DAOY, respectively, in order to decipher tumor-specific genetic dependencies. Our data demonstrate that SMB21 cells highly depend on positive regulators of the SHH pathway, such as Smo and Gli1 for their survival, as opposed to DAOY cells, suggesting that the latter does not represent a faithful model of SHH-MB. Members of the epigenetic machinery such as Dnmt1 and Smarca5 scored strongly as SMB21-context specific essentialities. Pharmacologically, we show that DNMT1 inhibition is efficacious at clinically relevant concentrations against SMO inhibitor- sensitive, as well as resistant SHH-MB cell lines, indicating novel therapeutic avenues for SHH-MB. By performing RNA sequencing of SMB21 cells, we identified early and late changes in global gene expression induced by DNMT1 inhibition, including decreased expression of mediators of SHH signaling, such as Gli1 and Gli2. Of note, gene set enrichment analysis revealed that DNMT1 inhibition downregulates top gene sets associated with cell cycle progression, corroborating the screening results that Dnmt1 is essential for SMB21 proliferation. Further global DNA methylation profiling in SMB cells will help to define the molecular basis of sensitivity to DNMT1 inhibitors in SHH-MB. Summarizing, our data highlight the potential of inhibitors targeting epigenetic regulators in SMO inhibitor- sensitive and resistant MB for more efficacious treatment options.