Targeting Hedgehog signaling and understanding refractory response to treatment with Hedgehog pathway inhibitors

Downregulation of Hedgehog Interacting Protein (HHIP) in Gastric Cancer: Implications for Tumorigenesis

The increasing incidence of gastric cancer (GC) in the Kashmir Valley is concerning, but its root causes are largely unknown. Dysregulated activation of the Hedgehog signaling pathway has been linked to various cancers, and the Human Hedgehog Interacting Protein (HHIP), a tumor suppressor, is frequently dysregulated in malignancies. However, the expression of the HHIP gene in GC is inconsistent and poorly understood. This study aimed to examine HHIP gene expression in gastric cancer. We used methylation-specific PCR, Western Blot analysis, and quantitative reverse transcription PCR (qRT-PCR) to assess the hypermethylation and expression levels of HHIP gene promoters. The correlation between these results and clinical parameters (e.g. age, gender, histological type, class, stage, and lymph node metastasis) was studied with samples from 53 GC patients confirmed by histology. In 69.81% (37 out of 53) of the tumor tissue, HHIP hypermethylation was found. Of the 45 cases examined for mRNA expression, 53.33% (24 out of 45) showed a decrease in the HHIP mRNA level compared to the normal sample. In addition, 49.05% (26 out of 53) showed a decline in the expression of HHIP proteins. Almost all GC samples with reduced protein expression also showed a reduction in mRNA levels. These results suggest that the hypermethylation of the HHIP promoter leads to a decrease in the regulation of HHIP, which contributes to the activation of the hedgehog signal path and may play a critical role in the progress of GC. Our study highlights the significant link between HHIP hypermethylation and reduced gene expression at both mRNA and protein levels, suggesting that target HHIP gene methylation could be a promising treatment strategy for gastric cancer.

Beyond cyclopamine: Targeting Hedgehog signaling for cancer intervention

Hedgehog (Hh) signaling plays a significant role in embryogenesis and several physiological processes, such as wound healing and organ homeostasis. In a pathological setting, it is associated with oncogenesis and is responsible for disease progression and poor clinical outcomes. Hedgehog signaling mediates downstream actions via Glioma Associated Oncogene Homolog (GLI) transcription factors. Inhibiting Hh signaling is an important oncological strategy in which inhibitors of the ligands SMO or GLI have been looked at. This review briefly narrates the Hh ligands, signal transduction, the target genes involved and comprehensively describes the numerous inhibitors that have been evaluated for use in various neoplastic settings.

Bioinformatics analysis of hedgehog interacting protein in colorectal cancer: a study based on GEO data and TCGA data

Colorectal cancer (CRC) is one of the most prevalent malignancies worldwide. Hedgehog Interacting Protein (HHIP) is evolutionarily conserved protein, which are important morphogens for a wide range of developmental processes,However, the specific role and mechanism of HHIP in CRC remains not fully understood. In this study, we first performed pan-cancer analysis for HHIP's expression via The Cancer Genome Atlas (TCGA) and The Genotype-Tissue Expression (GTEx) data and found that HHIP might be a potential anti-oncogene for CRC. Subsequently, non-coding RNAs (ncRNAs) contributing to down-regulated HHIP expression were identified through a combination of a series of in silico analyses, including expression and correlation analysis. Finally, the LINC02381/miR-577 complex was identified as the top potential upstream regulator of HHIP in CRC. In addition, HHIP expression level was significantly correlated with tumor immune cell infiltration, biomarkers of immune cells, and immune checkpoint expression. Overall, our findings clarified ncRNAs-mediated down-regulation of HHIP which was associated with poor prognosis and tumor immune infiltration in CRC.

Molecular Mechanisms Involving the Sonic Hedgehog Pathway in Lung Cancer Therapy: Recent Advances

According to the latest statistics from the International Agency for Research on Cancer (IARC), lung cancer is one of the most lethal malignancies in the world, accounting for approximately 18% of all cancer-associated deaths. Yet, even with aggressive interventions for advanced lung cancer, the five-year survival rate remains low, at around 15%. The hedgehog signaling pathway is highly conserved during embryonic development and is involved in tissue homeostasis as well as organ development. However, studies have documented an increasing prevalence of aberrant activation of HH signaling in lung cancer patients, promoting malignant lung cancer progression with poor prognostic outcomes. Inhibitors targeting the HH pathway have been widely used in tumor therapy, however, they still cannot avoid the occurrence of drug resistance. Interestingly, natural products, either alone or in combination with chemotherapy, have greatly improved overall survival outcomes for lung cancer patients by acting on the HH signaling pathway because of its unique and excellent pharmacological properties. In this review, we elucidate on the underlying molecular mechanisms through which the HH pathway promotes malignant biological behaviors in lung cancer, as well as the potential of inhibitors or natural compounds in targeting HH signaling for clinical applications in lung cancer therapy.

Exosomes secreted by chronic hepatitis B patients with PNALT and liver inflammation grade ≥ A2 promoted the progression of liver cancer by transferring miR-25-3p to inhibit the co-expression of TCF21 and HHIP

OBJECTIVES

The current study aimed to investigate the mechanism by which exosomes secreted by CHB patients with PNALT and liver inflammation grade (≥A2) affected the development of liver cancer.

MATERIALS AND METHODS

Gene expression was assessed by RT-PCR, Western blotting and immunohistochemistry. CCK-8, colony formation, transwell, scratch-wound and flow cytometry assays were used to detect cell viability, proliferation, apoptosis and metastasis. The interaction of TCF21 and HHIP was assessed by co-immunoprecipitation assay. Luciferase reporter was used to detect the combination of TCF21/HHIP and miR-25-3p. Xenograft studies in nude mice manifested tumour growth ability of miR-25-3p. Bioinformatics analyses were conducted using TargetScan, EVmiRNA, TCGA, GEO, DAVID, COEXPEDIA, UALCAN, UCSC and the Human Protein Atlas databases.

RESULTS

CHB-PNALT-Exo (≥A2) promoted the proliferation and metastasis of HepG2.2.15 cells. miR-25-3p was upregulated in CHB-PNALT-Exo (≥A2). miR-25-3p overexpression promoted cell proliferation and metastasis and was related to poor survival in patients with CHB-PNALT (≥A2). The cell proliferation- and metastasis-promoting functions of CHB-PNALT-Exo (≥A2) were abolished by miR-25-3p inhibitors. TCF21 directly interacted with HHIP. Inhibition of TCF21 or HHIP promoted cell proliferation and metastasis. Knockdown of TCF21 or HHIP counteracted the effects of CHB-PNALT-Exo (≥A2) containing miR-25-3p inhibitor on cell proliferation, metastasis and the expression of Ki67, E-cadherin and caspase-3/-9.

CONCLUSIONS

Transfer of miR-25-3p by CHB-PNALT-Exo promoted the development of liver cancer by inhibiting the co-expression of TCF21 and HHIP.

GLI1 Inhibitor SRI-38832 Attenuates Chemotherapeutic Resistance by Downregulating NBS1 Transcription in BRAFV600E Colorectal Cancer

Resistance to radiation and chemotherapy in colorectal cancer (CRC) patients contribute significantly to refractory disease and disease progression. Herein, we provide mechanistic rationale for acquired or inherent chemotherapeutic resistance to the anti-tumor effects of 5-fluorouracil (5-FU) that is linked to oncogenic GLI1 transcription activity and NBS1 overexpression. Patients with high levels of GLI1 also expressed high levels of NBS1. Non-canonical activation of GLI1 is driven through oncogenic pathways in CRC, like the BRAFV600E mutation. GLI1 was identified as a novel regulator of NBS1 and discovered that by knocking down GLI1 levels in vitro, diminished NBS1 expression, increased DNA damage/apoptosis, and re-sensitization of 5-FU resistant cancer to treatment was observed. Furthermore, a novel GLI1 inhibitor, SRI-38832, which exhibited pharmacokinetic properties suitable for in vivo testing, was identified. GLI1 inhibition in a murine BRAFV600E variant xenograft model of CRC resulted in the same down-regulation of NBS1 observed in vitro as well as significant reduction of tumor growth/burden. GLI1 inhibition could therefore be a therapeutic option for 5-FU resistant and BRAFV600E variant CRC patients.

HHIP overexpression inhibits the proliferation, migration and invasion of non-small cell lung cancer

Objective

The primary purpose of this study is to investigate the effect of hedgehog-interacting protein (HHIP) overexpression on the proliferation, migration and invasion of non-small cell lung cancer (NSCLC).

Methods

Firstly, HHIP gene expression data of NSCLC tissues and normal tissues were obtained from GSE18842/GSE19804/GSE43458 databases of the Gene Expression Omnibus (GEO) database and then validated by TCGA NSCLC database in a cohort of 1027 cases of NSCLC patients and 108 cases of normal people. A chi-square test was used to analyze the relationship between HHIP expression and clinicopathological characteristics of NSCLC. The expression levels of HHIP in NSCLC cells were detected by quantitative-real time PCR. The function of HHIP was investigated by a series of in vitro assays. CCK-8, wounding healing, Transwell invasion assay were utilized to explore the mechanisms of HHIP.

Results

HHIP mRNA were significantly down-regulated in NSCLC in three GEO databases and TCGA database (P<0.05). This result was confirmed in NSCLC cell lines by qRT-PCR analysis, its expression in normal NSCLC cell line BEAS-2B was significantly higher than that in NSCLC cells. Chi-square test results showed that the low expression of HHIP was correlated with gender, cancer type, TNM stage and tumor size. Functional experimental results showed that over-expressing HHIP significantly decreased the ability of cell proliferation, migration and invasion in NSCLC cells (P<0.05).

Conclusion

Overall, the above results indicated that HHIP could regulate proliferation, migration and invasion, and could be used as a judging criterion for identifying NSCLC classification and stage.

State of the art of Smo antagonists for cancer therapy: advances in the target receptor and new ligand structures

Since the Hedgehog signaling pathway has been associated with cancer, it has emerged as a therapeutic target for cancer therapy. The main target among the key Hedgehog proteins is the GPCR-like Smo receptor. Therefore, some Smo antagonists that have entered clinical trials, including the US FDA-approved drugs vismodegib and sonidegib, to treat basal cell carcinoma and medulloblastoma. However, early resistance of these drugs has spawned the need to understand the molecular bases of this phenomena. We therefore reviewed details about Smo receptor structures and the best Smo antagonist chemical structures. In addition, we discussed strategies that should be considered to develop new, safer generations of Smo antagonists that avoid current clinical limitations.

Analysis of hedgehog signaling in periocular sebaceous carcinoma

PURPOSE

Sebaceous carcinoma (SC) is a clinical masquerader of benign conditions resulting in significant eye morbidity, sometimes leading to extensive surgical treatment including exenteration, and even mortality. Little is known about the genetic or molecular basis of SC. This study identifies the involvement of Hedgehog (Hh) signaling in periocular SC.

METHODS

Fifteen patients with periocular SC patients were compared to 15 patients with eyelid nodular basal cell carcinoma (nBCC; a known Hh tumor), alongside four normal individuals as a control for physiological Hh expression. Expression of Patched 1 (PTCH1), Smoothened (SMO), and glioma-associated zinc transcription factors (Gli1 and Gli2) were assessed in histological sections using immunohistochemistry and immunofluorescence (IF) techniques. Antibody specificity was verified using Western-blot analysis of a Gli1 over-expressed cancer cell line, LNCaP-Gli1. Semi-quantification compared tumors and control tissue using IF analysis by ImageJ software.

RESULTS

Expression of the Hh pathway was observed in SC for all four major components of the pathway. PTCH1, SMO, and Gli2 were more significantly upregulated in SC (P < 0.01) compared to nBCC. Stromal expression of PTCH1 and Gli2 was observed in SC (P < 0.01). In contrast, stromal expression of these proteins in nBCC was similar or down-regulated compared to physiological Hh controls.

CONCLUSIONS

The Hh signaling pathway is significantly more upregulated in periocular SC compared to nBCC, a known aberrant Hh pathway tumor. Furthermore, the stroma of the SC demonstrated Hh upregulation, in particular Gli2, compared to nBCC. Targeting of this pathway may be a potential treatment strategy for SC.

Phosphoproteome analysis reveals a critical role for hedgehog signalling in osteoblast morphological transitions

The reciprocal and adaptive interactions between cells and substrates governing morphological transitions in the osteoblast compartment remain largely obscure. Here we show that osteoblast cultured in basement membrane matrix (Matrigel™) exhibits significant morphological changes after ten days of culture, and we decided to exploit this situation to investigate the molecular mechanisms responsible for guiding osteoblast morphological transitions. As almost all aspects of cellular physiology are under control of kinases, we generated more or less comprehensive cellular kinome profiles employing PepChip peptide arrays that contain over 1000 consensus substrates of kinase peptide. The results obtained were used to construct interactomes, and these revealed an important role for FoxO in mediating morphological changes of osteoblast, which was validated by Western blot technology when FoxO was significantly up-expressed in response to Matrigel™. As FoxO is a critical protein in canonical hedgehog signalling, we decided to explore the possible involvement of hedgehog signalling during osteoblast morphological changes. It appeared that osteoblast culture in Matrigel™ stimulates release of a substantial amounts Shh while concomitantly inducing upregulation of the expression of the bona fide hedgehog target genes Gli-1 and Patched. Functional confirmation of the relevance of these results for osteoblast morphological transitions came from experiments in which Shh hedgehog signalling was inhibited using the well-established pathway inhibitor cyclopamine (Cyc). In the presence of Cyc, culture of osteoblasts in Matrigel™ is not capable of inducing morphological changes but appears to provoke a proliferative response as evident from the upregulation of Cyclin D3 and cdk4. The most straightforward interpretation of our results is that hedgehog signalling is both necessary and sufficient for membrane matrix-based morphological transitions.

Relationship between Hedgehog signaling pathway and pancreatic cancer

Hedgehog (Hh) signaling pathway consists of ligands such as Hh, receptor (patched), transmembrane protein Smo, nuclear transcription factor Gli, and downstream target genes. This pathway plays an important role in cell differentiation, tissue development and organ formation in the embryonic stage. In recent years, the Hh signaling pathway has been reported to play an important role in the development of pancreatic cancer. It can induce differentiation, proliferation and invasion of pancreatic cancer cells. Blocking the Hh signaling pathway in pancreatic cancer cells will provide a new and effective method for the treatment of pancreatic cancer. In this review, we will summarize the composition of the Hh signaling pathway and its relationship with the development of pancreatic cancer.

The biologic era of childhood medulloblastoma and clues to novel therapies

Currently, the treatment of childhood medulloblastoma (MB) is tailored to risk groups defined by clinical parameters. Growing evidence of tumoral heterogeneity is apparent as response remains varied and unpredictable based on current treatment strategies, indicating the lack of understanding of the elusive biology that drives oncogenesis of these tumors. Advances in genomic technologies are revealing newer insights into the molecular pathogenesis of MB. Utilization of the genomic machinery has enabled the definition of new molecular markers and signaling pathways, resulting in a paradigm shift in the classification of childhood MB. Recent focus into the postgenomic era has revealed varied perturbations in the epigenetic machinery in these subtypes as likely predictive biomarkers and potential therapeutic targets. Ahead lies the task and challenge in the ability to comprehensively evaluate all these data, which could provide clues to profile the next-generation clinical trials combining conventional with molecularly targeted novel therapies.

Occurrence of HHIP gene CpG island methylation in gastric cancer

The present study aimed to observe the methylation status of the CpG islands at the human hedgehog interacting protein (HHIP) gene in gastric cancer tissues, peritumoral tissues and the AGS cell line, to analyze the association between the methylation status of the CpG islands and the tumorigenesis of gastric cancer. The HHIP mRNA expression in 60 human gastric carcinnoma tissues, peritumoral tissues and the gastric carcinoma AGS cell line were detected by reverse transcription polymerase chain reaction (RT-PCR). The HHIP methylation status of the promoter region in the gastric carcinnoma tissues and peritumoral tissues was detected by methylation-specific PCR (MSP). Prior to and following treatment with methyl transferase inhibitor 5-aza-2'-deoxycitydine (5-aza-dc), the HHIP mRNA expression level, the methylation status of the promoter region and the methylation site loci on the CpG islands in the AGS cells were detected by RT-PCR, MSP and bisulfite sequencing PCR (BSP), respectively. The correlation between the methylation status of the CpG islands at the HHIP promoter region and the HHIP mRNA expression level were analyzed. It was found that the expression level of the HHIP mRNA in the gastric carcinoma tissues was significantly lower than that in the adjacent tissues (0.82±0.38 vs. 1.60±0.26, respectively; P<0.001). No significant correlations were observed between the expression of HHIP mRNA and age, gender, tumor-node-metastasis stage, differentiation degree and presence of lymph node metastasis (P>0.05). The degree of methylation of the HHIP gene promotor in the peritumoral tissues (17.7±3.59%) was significantly lower than that in the gastric cancer tissues (62.9±6.14%) and in the AGS cells (99.7±0.67%) (P<0.05). Compared with prior to 5-aza-dc intervention, the HHIP mRNA expression level in the AGS cells was significantly increased subsequent to intervention (0.21±0.12 vs. 4.68±0.22; P<0.01), while the degree of methylation in the AGS cells was significantly decreased (90.2±0.67 vs. 10.1±0.21%; P<0.01), and the methylation sites in CpG islands were significantly reduced. The degree of HHIP methylation showed a negative correlation with the level of mRNA expression (r=-0.693; P<0.01). It can be hypothesized that a high degree of methylation of the HHIP gene promoter CpG islands in gastric cancer tissues and cells causes a decrease in HHIP mRNA expression, which may be involved in the carcinogenesis of gastric cancer.

Protease-activated receptor-1 drives pancreatic cancer progression and chemoresistance

Protease activated receptor (PAR)-1 expression in tumor cells is associated with disease progression and overall survival in a variety of cancers of epithelial origin; however, the importance of PAR-1 in the tumor microenvironment remains unexplored. Utilizing an orthotopic pancreatic cancer model in which tumor cells are PAR-1 positive whereas stromal cells are PAR-1 negative, we show that PAR-1 expression in the microenvironment drives progression and induces chemoresistance of pancreatic cancer. PAR-1 enhances monocyte recruitment into the tumor microenvironment by regulating monocyte migration and fibroblast dependent chemokine production thereby inducing chemoresistance. Overall, our data identify a novel role of PAR-1 in the pancreatic tumor microenvironment and suggest that PAR-1 may be an attractive target to reduce drug resistance in pancreatic cancer.

Blocking signaling at the level of GLI regulates downstream gene expression and inhibits proliferation of canine osteosarcoma cells

The Hedgehog-GLI signaling pathway is active in a variety of human malignancies and is known to contribute to the growth and survival of human osteosarcoma cells. In this study, we examined the expression and regulation of GLI transcription factors in multiple canine osteosarcoma cell lines and analyzed the effects of inhibiting GLI with GANT61, a GLI-specific inhibitor. Compared with normal canine osteoblasts, real-time PCR showed that GLI1 and GLI2 were highly expressed in two out of three cell lines and correlated with downstream target gene expression of PTCH1and PAX6. Treatment of canine osteosarcoma cells with GANT61 resulted in decreased expression of GLI1, GLI2, PTCH1, and PAX6. Furthermore, GANT61 inhibited proliferation and colony formation in all three canine osteosarcoma cell lines. The finding that GLI signaling activity is present and active in canine osteosarcoma cells suggests that spontaneously arising osteosarcoma in dogs might serve as a good model for future preclinical testing of GLI inhibitors.

A functional germline variant in GLI1 implicates hedgehog signaling in clinical outcome of stage II and III colon carcinoma patients

PURPOSE

Cumulating evidence indicates that germline variants in the Wnt, Notch, and Hedgehog pathways are involved in colon carcinoma progression and metastasis. We investigated germline polymorphisms in a comprehensive panel of Wnt, Notch, and Hedgehog pathway genes to predict time to recurrence (TTR) and overall survival in patients with stage II and III colon carcinoma.

EXPERIMENTAL DESIGN

A total of 742 consecutively collected patients with stage II and III colon carcinoma were included in this retrospective study. Genomic DNA was analyzed for 18 germline polymorphisms in Wnt, Notch, and Hedgehog pathway genes (SFRP, DKK 2 and 3, AXIN2, APC, MYC, TCF7L2, NOTCH2, and GLI1) by TaqMan 5'-exonuclease assays.

RESULTS

In univariate analysis, the homozygous mutant variant of GLI1 rs2228226 G>C was significantly associated with decreased TTR in a recessive genetic model after adjustment for multiple testing [HR = 2.35; confidence interval (95% CI), 1.48-3.74; P < 0.001] and remained significant in multivariate analysis including clinical stage, lymphovascular-, vascular-, and perineural-invasion (HR = 2.43; CI 95%, 1.52-3.87; P < 0.001). In subanalyses, the association was limited to patients with surgery alone (HR = 3.21; CI 95%, 1.59-6.49; P = 0.001), in contrast with patients with adjuvant chemotherapy (HR = 0.82; CI 95%, 0.35-1.95; P = 0.657). When the subgroup of patients with "high-risk" GLI1 rs2228226 C/C genotype was analyzed, no benefit of adjuvant 5-fluorouracil-based chemotherapy could be found.

CONCLUSION

This is the first study identifying GLI1 rs2228226 G>C as an independent prognostic marker in patients with stage II and III colon carcinoma. Prospective studies are warranted to validate our findings.

[Structure of the Smoothened receptor]

The Smoothened (Smo) receptor is a major component involved in signal transduction of the Hedgehog (Hh) morphogens both during embryogenesis and in the adult. Smo antagonists represent a promi-sing alternative for the treatment of cancers linked to abnormal Hh signalling. The crystal structure of the human Smo receptor bound to an antitumour agent demonstrates that this receptor belongs to the superfamily of G-protein coupled receptors. The antagonist binds to a pocket localized at the extracellular side formed by the seven transmembrane domains and the complex arrangement of the unusually long extracellular loops. The structure of the Smo receptor will promote the development of small molecules interacting with a key therapeutic target with interests in regenerative medicine and cancer.